Disclaimer: links to web sites are ever-changing. It turns out to be a Sisyphus task to keep them updated all the time. Therefore, either try a different "spelling" of the hyperlink, look for it on google.com and/or let me know about an outdated link by writing an e-mail to aveh@wncc.net
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The Sky in November 2007
Winter has almost arrived and that means that the bounty of the beautiful winter sky charms us once more. The accompanying chart is set for 10 pm in late November, thus fewer stars are visible in the East during evening hours earlier in the month (but more in the West); stars with an asterisk * attached to them are marked with a letter on the chart. Orion, Taurus, Auriga and Gemini are visible in the Southeast. Inside these constellations are the bright stars of winter: red *Betelgeuse and *Aldebaran, blue *Rigel , yellow *Capella and the twins' *Castor and *Pollux; the latter two make a fine triangle with Mars. Also included is the star cluster of the Pleiades, best viewed with binoculars when up to 50 stars may be seen. Soon the bright stars Procyon and Sirius will follow. Now near the Zenith are Cassiopeia's W, the House of Cepheus, Pegasus’ Great Square and the swan Cygnus’ northern Cross.
Always in the same place is the Little Dipper with *Polaris and atop the Northern horizon appears the Big Dipper. The kite-shaped Bootes with red Arcturus is now setting while the summer triangle consisting of *Deneb (the Swan's tail), *Vega and *Altair is getting closer to the Western horizon.
Mars rises around sunset. Planets move counterclockwise in the Solar System – when viewed from North – which produces their true West to East motion along the ecliptic and through the Zodiac constellations as seen from one night to the next. But when the Earth, and we as the observers on Earth, pass a planet, that planet seems to move in the opposite direction: it retrogrades. From November through January it’s really easy to see Mars retrograde – which is mostly evidence for us passing Mars – because there are three stars situated near that are of comparable brightness. In the process of us passing Mars, the red planet becomes also brighter to the naked eye and appreciable larger in a telescope until it reaches opposition on December 19. Observe Mars weekly or even daily: it can be seen to the right (West) of Castor and Pollux in Gemini, moving East-West (left-to-right) towards red Aldebaran in Taurus (with the Pleiades further West). The triangle formed by Castor, Pollux and Mars becomes ever more elongated from mid-November through December until Mars stops retrograding in late January – now quite a bit closer to Aldebaran – when we have passed the planet enough that we see its true motion again. Mars is flanked by the almost full Moon on the 25th (see chart) and 27th of November, on the 26th Mars sits right beneath it.
Jupiter would be visible very low in the Southwestern sky during dusk, but only in the Southern United States.
Pluto, Neptune and Uranus are too low in the sky as well to be observable from Alaska.
Saturn and Venus are visible during dawn, having developed into a line with Leo’s Regulus: from midnight on throughout the rest of the night find Regulus leading Saturn in the East, then around 5 am Venus rises and you can use it to find the now higher situated star and ringed planet. And since Alaska nights get longer every day, you’ll see Venus during your morning commutes, if you’re heading East. On November 5 a crescent Moon is near Venus.
Mercury is also visible during early November in the dawn sky: between 7 am and 8 am – as you’re enjoying dazzling Venus, connect an imaginary line diagonally to the lower left from it towards the horizon: you should be able to see Mercury very low on the Southeastern horizon. In fact, the similarly bright star Spica is just to the right of it, so look for “headlights” beneath Venus, though Venus is quite a beacon compared to those headlights. On November 7 a very crescent Moon joins Mercury and Spica. Towards the middle of the month Mercury has moved along, seemingly back towards our Sun, now producing a long, slightly curved line with Spica and Venus. Try finding this speedy planet as few people have consciously seen the planet as such.
The Leonid meteor shower peaks in the wee hours of November 18th with an expected average of about 10 meteors per hour.
Comet 17P/Holmes came as a nice fuzz ball into view; it was the 17th periodic comet discovered and recognized as being periodic (1P/Halley was the first) by Edwin Holmes in 1892, with a seven year orbit that brings it as close as Mars’ orbit and as far as Jupiter’s orbit. Use binoculars and look half-way between Auriga’s pentagon and Cassiopeia’s W, the comet is about as bright as the surrounding stars.
The Sky in October 2007
As research for my astronomy columns I'm reading "Celestial Delights - the best Astronomical events through 2010" by Reddy and Walz-Chojnacki, some specialized information if I talk about a certain subject, and I study the “Starfinder” (a simple cardboard sky map that tells us where the stars are at any time during the night on any day during the year, every year). But I prepare especially by perusing the future issues of "Sky & Telescope" and "Astronomy". With "future" I mean that the November issues are about to hit the stores by the time you read this October article. Unfortunately all weekly and monthly periodicals publish their newest issue with a future date that still may be a month out and they are therefore pretending to be super-current (they're not). But just about the only magazines for which this is justified are astronomy related ones because they publish highly predictable events with the intent that readers would know about them a few weeks ahead of the fact. Ditto my monthly column.
So when I prepare my columns I carefully read through “Sky & Telescope” and then I don’t do this: plagiarize. Plagiarism is unethical, unlawful, and university professors hand out Fs for the course work if a paper was plagiarized. But besides that, I can’t even do it. I cannot take somebody else’s work and retype it. I just like my own sentence structure that’s distinctly me, including my German accent. In fact, after I have read through my sources, I put them aside and then I write my own narrative, frequently checking the sources for exact dates. So when I write that we will have a full Moon on October 25th at 8:52 pm, then even my facts are markedly different from the source (“The Moon is full at 12:52 a.m. EDT on the 26th”, S&T, October 2007, p.55), yet - of course - still similar since it’s about the Moon, it’s full, it’s in October and there are only a handful of ways to write about that in a coherent sentence.
After this long introduction (and I’m not done with the introduction) I figured I’d stray from my usual narrative and instead reiterate the information printed in S&T; you may compare. Please note that these are still my own words since I use a different way of writing (S&T has the luxury of using 23 pages to report on upcoming celestial events and observations while I’m restricted to half a page; I’m also using more parentheses).
During dawn on October 7 and 8, Saturn and Venus as well as the bright star Regulus in Leo and a waning crescent Moon shine low in the East (see the diagram, made with the shareware Stellarium). During the following days those two planets and star are really close to each other while our Moon moves on toward its monthly encounter with our Sun. On the 15th the now waxing crescent Moon meets Jupiter and Antares in Scorpius; however, this crescent as well as the 1st quarter Moon are very low on the Southern horizon – you may have seen the same scene in mid-September. The Orionid meteor shower takes place from October 20th through 22nd – its meteors can be seen anywhere in the sky, originating from their vantage point in Orion, high in the South. On October 25 we’ll have the largest full Moon of the year because it is also near its perigee at a distance of only 220,000 miles compared to an average 240,000 miles. On October 28th, Venus is at 46 degrees at its farthest from our Sun and has by now become a mainstay in the Eastern dawn sky through January 2008.
During October evenings the Summer triangle consisting of Cygnus, Aquila and Lyra (cross, eagle, small harp) are high in the South, the East harbors Pegasus and Andromeda (great square, two curved rows of three stars each), the North the Little and the Big Dipper, the West Bootes (kite), and Cassiopeia (a W shape) may appear near the Zenith. Bright Jupiter may be found close to the Southern horizon.
Mars becomes visible shortly before midnight, rising in the East. Through April 2008 it moves and retrogrades between Gemini and Taurus. Mainly look for a reddish object appearing between two bright stars and the bull’s snout with also reddish Aldebaran and the Pleiades.
Finally, last week marked the 50th anniversary of the first man-made satellite orbiting Earth, Спутњик (same pronunciation of the ‘u’ as in “butchered”), launched on October 4, 1957. These days, if you’re standing outside for just an hour or so staring up, you’re bound to see a few artificial satellites moving across the sky.
The Sky in August and September 2007
Stars can actually be seen again, so it's time to resume my Astronomy column. I usually write a September article but since there is a Total Lunar Eclipse visible from Alaska during the night of August 27/28, Monday to Tuesday, it makes more sense to have it published one week early.
This is not the perfect lunar eclipse - it's after midnight, our Moon sits very low above the Southern horizon, and you never know about the weather on the Kenai. But the largest land mass on Earth that can view the entire eclipse is Alaska. Front seats are also reserved for the US and Canadian West coast and Eastern Australia and New Zealand. The only other mammals to see this gorgeous event are Pacific whales and dolphins. However, the entire rest of North and South America can at least view the latter part of the eclipse prior to dawn.
But back to Alaska. The full Moon starts to enter Earth's shadow at midnight but since so much sunlight still reaches our Moon, we won't notice until 1 a.m. Then our Moon enters Earth's umbral shadow, meaning that it now becomes more and more totally eclipsed by Earth's shadow. Totality lasts rom 2 a.m. to 3:20 a.m. - our Moon won't be entirely dark because Earth's atmosphere refracts sun light onto it, most strongly red, that colors our Moon copper-red. Then our Moon starts leaving Earth's shadow and the eclipse concludes at 5:20 a.m. when we get the fully illuminated Moon back.
If it's cloudy or if you're too tired to stay up that early, don't despair. While our Moon will go through its phases six times during the next six months - its amount of lit and dark surface entirely due to its place in its orbit where more or less sunlight is reflected to Earth - another total lunar eclipse is in store on February 20/21, 2008, visible in its entirety from Alaska as well.
As far as observing goes, viewing this lunar eclipse with your unaided eyes from your backyard will be just fine. Binoculars or a telescope are not necessary, though they may show some interesting features.
By the way, lunar eclipses are always accompanied by one or two solar eclipses, either 14 days prior or later. However, neither of the upcoming solar eclipses are observable from North America as the partial solar eclipse of September 11, 2007, is seen from South America and Antarctica, while the annular solar eclipse of February 7 is visible from Antarctica, Australia and New Zealand.
Now let's look at the stars that become visible this month. High in the South is the Summer Triangle made up of Vega, Deneb - in the cross-like constellation Cygnus - and Altair. High in the East are the Great Square of Pegasus and Andromeda, of course containing the Andromeda Galaxy which can be found with binoculars. I figure that it would be too arduous to describe here how to find it without producing another more detailed finder chart; therefore I refer the reader to http://www.greenwich-observatory.co.uk/andromeda.html. Stretching along the Southern and Eastern horizon are the Zodiac constellations Capricornus, Aquarius, Pisces, Aries, and finally Taurus. The first three, Cap, Aqr, Psc lack bright stars and distinctive shapes and are very close to the horizon, hence they are more difficult to observe from Alaska. Our Sun will reside in these constellations as well as in Scorpius and Sagittarius during winter and one can see why our Sun hugs the horizon during winter months. Neptune and Uranus can be glimpsed in Capricronus and Aquarius; finder charts are available at http://www.rasnz.org.nz/SolarSys/UranNept.htm - just hold them upside down because it's a New Zealandian web site. Sky & Telescope has finder charts in their July 2007 issue but unfortunately not online. Perhaps it advantageous to find them during the night of the lunar eclipse, because Uranus resides the same distance to the left of our Moon as Neptune resides to its right.
Towards the East Taurus with the splendid star cluster of the Pleiades becomes visible - more about that when we get into winter - as well as Mars which is hosted by both Taurus and Gemini throughout this winter. Low in the Northeast is Aquila with bright Capella, the first star announcing fall. The Big Dipper, part of Ursa Major, appears in the North. Its pointer stars in the bowl are used to find the North Star, because they point at it. Polaris itself is at the end of the Little Dipper's handle. On the opposite side are the W-shaped Cassiopeia and the house-shaped Cepheus, albeit somewhat fainter. Back to the Big Dipper, we can use its handle's curvature to find bright Arcturus in the West and at the bottom of kite-shaped Bootes. To its left are Corona Borealis and Hercules.
During pre-dawn and dawn, very bright Venus may be glimpsed low in the East - if you drive East on the Sterling highway during the wee hours, that's what you see. And halfway between Venus and the Eastern horizon are Saturn and Leo's Regulus shining like faint headlights - however, the Kenai Mountains in the East probably obscure that view.
The Sky in April 2007
Days are getting longer and nights are
getting shorter. We're also leaving the freezing cold behind. As we all
love winter's benefits, we surely regret that our beloved starry skies will
take a back seat soon.
But at least we get some nice views for a good-bye. With
Daylight Savings Time having started, it doesn't get dark until 10 pm or even
later and therefore the diagram shows the Western sky around 11 pm towards the
end of April. This late in the season, many of the brilliant stars of winter are
either gone or hard to detect. Therefore look early in the month in the West for
Sirius and Orion with Betelgeuse and Rigel, Aldebaran and the Pleiades. Still
visible all month are the twins Castor and Pollux in the middle of the diagram,
Procyon below and left of middle, Capella in its pentagon of Auriga on the
right and, having shifted from East to West throughout late winter are Leo with
Regulus and Saturn nearby. The latter is actually of virtually the same
brightness as these bright stars and thus blends in pretty good, so you would
need this diagram or a starfinder to locate Saturn.
Visible after sunset for about two hours is very bright Venus in the West and since it will stay there all summer, it will probably be the only heavenly object – aside from our Moon of course – that is easily spotted in our lit Alaskan night skies. When viewing Saturn with binoculars look for its rings and its largest and brightest moon Titan.
Jupiter appears in the night sky too but it’s in the Southern portion of the constellation of Ophiuchus which is near Scorpius and since Scorpius is such a low Zodiac constellation, Jupiter also appears very low on the Southern horizon around 2 am.
The other planets are currently too close to the Sun and it’s very hard to view them, especially since they only appear during our long dawn hours.
In the East find Arcturus by following the Big Dipper’s handle, in the Northeast Vega, Deneb and Altair are becoming more prominent. They can be seen all summer during the few hours of semi-darkness and are aptly named the Summer Triangle.
I could talk about the pros and cons of Daylight Savings Time but I don’t want to start a discussion that may be futile. Just this much: local noon is actually at 2 pm on the Kenai when the Sun is highest and local midnight at 2 am.
Instead I figured I’d talk about religious feasts that are based on astronomical observations of our Moon’s phases – not that that wouldn’t start a discussion.
The Islamic
calendar is completely based on the lunar cycle with 12 months, i.e. about 354
days long, each starting with the first sighting of the lunar crescent after
the new moon, from Muharram to Dhu
al-Hijjah. That’s on average 11 days shorter than the solar based
Gregorian calendar, so on it Islamic holy days are seemingly shifting by 11
days every year, although within the Hijri calendar itself they are celebrated
on fixed days. The first year started in GC 622 with the Hijra (withdrawal of
Muhammad from
The Jewish calendar is based on the lunar cycle with 12 months basically alternating between 29 and 30 days (our Moon needs 29.53 days to go through its cycles), each starting with the new moon, from Nisan to Adar. That means each lunar year is about 11 days shorter than a solar year, so about every third year contains a leap month, Adar II with 29 days. Because that’s still a little too short, leap years are still more frequent (calculated by year modulus 19 as years 0, 3, 6, 8, 11, 14, and 17), hence the “about”. The equivalent in the Gregorian calendar to the Jewish calendar’s first month Nisan is either March or April. In GC 2007 (JC 5767), 1 Nisan is March 20 (new moon was on March 19) and with the Passover always beginning on 15 Nisan, that would be April 3; of course Jewish days start at sundown, so Pesach (Passover) lasts from April 2 through April 9 or 10.
The Christian calendar, more commonly called the Gregorian calendar, is based on the solar year. The date of Easter is computed by figuring out the beginning of spring, i.e. the vernal equinox, figuring out the following Full Moon and then the upcoming Sunday. That’s the basic computation to compute this date on a computer, hence the official name of Computus which derives from the Council of Nicaea. This year’s spring equinox happened on March 21, the next full moon is on April 2 and the next Sunday is April 8.
By the way, the full moon on April 2 is the smallest of the year since our Moon happens to be near its apogee at 255,000 miles, the farthest point from Earth in its orbit, compared to an average 240,000 miles.
Thanks go to Marion Yapuncich who directed me to the free software Stellarium with which my image was generated and to Barb Christian who inspired me with the idea for this month’s topic.
The Sky in March 2007
The stars of winter aren’t quite gone yet. But the days are getting
noticeably longer. I consider Leo to be the constellation that heralds spring as
it becomes very prominent in March, then moves quickly across the sky over the
next weeks and by the time it’s out of sight it’s almost summer.
Leo is positioned now prominently high above the Eastern horizon and can be
pictured facing to the right with the bright star Regulus as the front paw, the
hind leg to the left, a tail, a back and above the right shoulder with a faint
mane. An interloper may add some confusion though to its outline: Saturn
resides in or near Leo through 2009. If you have good binoculars, prop your
arms on a car roof to stabilize yourself and you might be able to see its rings
and probably are able to see its largest moon Titan.
During dusk and shortly thereafter find bright Venus above
the Southwestern horizon. Mercury has become a morning planet but only makes
for good views for observers on the Southern hemisphere. The same holds for
Mars, Uranus and Neptune as all four of these are situated in Capricornus and
Aquarius which are constellations that rise hardly above the horizon for
observers in
Still prominent above the Southwestern horizon, find the great constellations of winter centered on Orion with its brightest stars, red Betelgeuse and blue Rigel, its belt and sword containing the Orion nebula, a great target for binoculars; to Orion’s lower left lies Canis Major with the sky’s brightest star Sirius; to its left the star Procyon in its imperceptible constellation Canis Minor; to its upper left Gemini with its stars Castor and Pollux; above it Auriga in the shape of a pentagon with Capella; and to Orion’s upper right Taurus with red Aldebaran in the arrow head shaped open cluster Hyades and the most prominent open cluster Pleiades.
Every half year Earth enjoys a couple of eclipses. A total
eclipse of our Moon is visible from everywhere in the world, except
I wish I had the time to write an Astronomy column every day. But while holding down a serious and respectable full-time job, it’s hard to compete with astrologers, getting paid to make up stuff. I assume that from a reader’s perspective, horoscopes are nice entertainment, just as I read the cartoons and Dear Abby on the same page and do the Soduko. I wonder how it looks like from the astrologers’s side, maybe it’s a hard job after all, since inventing short stories does require quite a bit of creativity.
Anyway, I figured that I’d try myself on casting some horoscopes. Here they are; of course, the dates refer to the correct definition of the Sun entering and leaving a constellation. Aries (4/18-5/12): in the morning you’re likely to get up, in the evening you’re probably going to rest. Taurus (5/13-6/19): the stars in the Hyades clusters move toward the same vantage point. Gemini (6/20-7/19): this is hard. I admit, that astrologers do have a tough job, pulling adjectives and nouns out of thin air. Cancer (7/20-8/9): my situation of concocting bon-mots hasn’t improved. Leo (8/10-9/15): well, hm, … Okay, I got it. You’ll be surprised to see a bright object in your constellation. Then again, if you have read my astronomy column, you won’t be surprised. Virgo (9/16-10/29): you have a more rigid, theory-oriented approach to life. You are very organized. Libra (10/30-11/22): if you have kids, they will want to play. Be aware that they’ll refuse to go to school today. Scorpius (11/23-28): travel South. Then look out for something new and something really big. In fact, currently Jupiter resides in your constellation and a bright Nova has popped up. Ophiuchus (11/29-12/16): beware the ides of March. Advise to the wise: carry snakes. Sagittarius (12/17-1/18): three square meals, possibly served on round platters, are awaiting you today. Capricornus (1/19-2/14): what’s a sea goat? Aquarius (2/15-3/10): you are poetic, on the other hand, you know nothing of the scientific world (yep, that must be me). Pisces (3/11-4/17): you possibly will celebrate a birthday this month. I cast the bold prescience that it will be confined between 1 and 99.
As an exercise of applying the scientific method to outrageous claims, I had a couple of classes (about 25 students) in the past year try to match up horoscopes blindfolded. The success rate was at 10-15%, slightly higher than the expected 8% random match. (“Slightly higher” shouldn’t be taken as encouragement for the accuracy of horoscopes as there is still a failure rate of 85-90%.)
The Sky in February 2007
The diagram shows the sky on the Western horizon on February 7 at 6:00 pm. Early
February is the best time this year to view Mercury. You can bracket
observations around the 7th, perhaps from the 4th through the 12th.
Here’s how to find Mercury: start during dusk, about 20-30 minutes after
sunset (5:20 pm progressing to 5:40 pm during that time frame); find bright
Venus close to the horizon in the general direction of where the Sun just set,
i.e. Southwest; from there Mercury is a little closer to the horizon. Don’t
wait too long during the evening because both Mercury and Venus get ever closer
to the horizon, are thus harder to see, and set at 7:20 pm and 8:00 pm,
respectively. After dusk find the Great of Square Pegasus above Venus and
Cygnus further West; perhaps the cute constellation of Delphinus still shows
up.
The evening sky finds Ursa Minor in the North with Polaris
at the end of the Little Dipper’s handle as usual 60 degrees above the
horizon, telling us the Kenai’s latitude. East – or to the right
– of UMi lies Ursa Major with the Big
Dipper’s handle pointing toward the horizon and the last two stars in the
Dipper pointing toward Polaris. West – or to the left – of UMi are Cassiopeia in the shape of a W and Cepheus in the shape
of a house. As mentioned above, Pegasus and Cygnus with bright Deneb are
visible in the West, and so is the bright star Vega. Furthermore, one can find
the Andromeda Galaxy as follows: getting away from town lights and using
binoculars, look at second base of Pegasus’s
In the East find Leo with bright Regulus and a bright intruder, the planet Saturn. And finally, watching a big finale in the South, find the great constellations of winter centered on Orion with its brightest stars, red Betelgeuse and blue Rigel, its belt and sword containing the Orion nebula, a star forming region and also a great target for binoculars; to its lower left lies Canis Major with the sky’s brightest star Sirius – Venus and Jupiter are brighter but they’re planets; to its left the star Procyon in its imperceptible constellation Canis Minor; to its upper left Gemini with its stars Castor and Pollux; above it Auriga in the shape of a pentagon with Capella; and to its upper right Taurus with red Aldebaran in the arrow head shaped open cluster Hyades and the most prominent open cluster Pleiades. When it gets cold and clear, bundle up, have cookies and hot chocolate at hand, and brave the cold to marvel at the best views the Northern hemisphere is offering. Also, if you happen to use hot rum to stay warm, invite me too.
I have to admit that Comet McNaught caught me off guard
early last month. However, it was so close to the Sun that it was tough to find
anyway, so unfortunately we didn’t miss out on much by not knowing about
the comet. In the meantime it had become spectacular in the Southern
hemisphere: check out great images from
A couple of beautiful sights are the open clusters in Taurus, the Pleiades and the Hyades. The Pleiades, also called the Seven Sisters, appear as a mini dipper at a distance of 440 lightyears, containing about 500 stars and having evolved from a stellar nebula only about 100 million years ago. An open cluster orbits within our galaxy’s disk and its gravitational interaction with other stars will eventually disperse its stars; a globular cluster – there are some in Gemini and Auriga that can be seen with binoculars – in contrast orbits our galaxy at steep angles at distances of thousands of lightyears, its typically 100,000 stars stay gravitionally locked together, and they were born billions of years ago (both types of star clusters are ideal examples for stellar evolution with one of the main astrophysical tools, the Hertzsprung-Russell diagram, supplying their age). The Hyades are the clostest open cluster at 151 lightyears from our solar system with 100 stars and an age of 700 billion years. Open clusters are used for measuring accurate distances as well by recording its stars’s proper motion as they are moving towards a common vanishing point (a method also used in the arts for perspective drawings). However, even closer is the Ursa Major Moving Group at only 80 lightyears. While one characteristic of open and globular clusters is their stars’s proximity to each other, the UMa Group is really spread out with 5 of the Big Dipper’s stars moving in the same direction.
I’ll be offering a couple of free community classes on February 19 and 26 at 7 pm at KPC, probably covering observation techniques and doing outside observations.
The Sky in January 2007
The
view is toward Southeast between 7 pm and 10 pm throughout January; because of
Earth’s rotation, this part of the sky moves through the South into the
Southwest each night all night long. Three constellations are dominating
the sky: Orion the hunter, Gemini the twins, and Taurus the bull. This part of the sky is probably the most
interesting and brilliant since it contains a number of easily seen deep sky
objects as well as eight of the twenty brightest stars. Starting with Sirius,
the brightest one of all, on the horizon, we go clockwise to Procyon, then the
twin stars Castor and Pollux, then yellow Capella (just outside the diagram on
top left), then red Aldebaran in Taurus’ arrowhead, and finally close the
circle with blue Rigel and red Betelgeuse in Orion.
What makes a star (or any other object, e.g. a planet or our Moon) appear bright or faint depends on how bright the star really is and how close it is. Sirius and Procyon are actually the least luminous of these stars but are the closest at 9 and 11 light years. In contrast, Betelgeuse is at a distance of 430 ly but almost makes up for it by being 400 times brighter than Sirius.
Rigel, a blue supergiant at Orion’s foot, and Capella, a yellow normal giant high above Gemini, make for a good comparison. As they are of virtually the same apparent brightness, Capella is 42 ly close while Rigel is 770 ly far, i.e. 18 times further. But the latter is also 315 times more luminous; doing the math and knowing that brightness diminishes with the square of distance, 18^2 = 324, they appear virtually equally bright as seen from our solar system. Their difference in luminosity is originally based on their mass, 2.7 solar masses for Capella and 17 solar masses for Rigel. For a star to be in a balance between gravitation (due to its mass) and gas pressure (due to its high internal temperature), it has to be of a certain size and surface temperature: Capella has a diameter of 9 million miles (ten times that of our Sun) and a surface temperature of 10,000 F (making it yellow; virtually the same as our Sun) while Rigel has a diameter of 61 million miles (roughly the orbit of Mercury) and a surface temperature of 20,000 F (making it blue). Those two properties explain why Rigel is so much more luminous than Capella.
Aside from stars, there is of course the Orion nebula, a birth place for stars, making up the sword which can be glimpsed with binoculars. We find two prominent star clusters in Taurus, the Pleiades (just outside the diagram on top right) and the Hyades (the arrowhead surrounding Aldebaran) which can easily be seen with the naked eye. Stretching from Gemini up to Capella are four star clusters which need some prodding when using binoculars. Since Gemini and Taurus are also Zodiac constellations, planets regularly move through them, as Mars will do next winter.
Other prominent constellations and stars in the sky are the Little Dipper high in the North, the Big Dipper in the Northeast, Cassiopeia’s W almost in the Zenith (overhead), Pegasus’s Great Square low in the West, and Cygnus’s cross with bright Deneb and next to it bright Vega, both low in the Northwest.
As for
planets, Saturn rises between 8 pm and 10 pm due East, together with bright
Regulus in Leo. Jupiter can be seen very, very low in the South around 8 am.
Mars, Mercury and Neptune are within our Sun’s glare during dusk and
dawn. Venus should become visible just after sunset low in the Southwest
(“
Good sources for sky maps are Astronomy and Sky & Telescope magazines, available at Freddies and Safeway, and online monthly sky charts at skymaps.com and at skytonight.com.
The Sky in December 2006
Last month’s Mercury transit was a great success, owing mostly to clear skies
and it happening in the middle of an Alaskan winter day. About 100 people
showed up to look through my telescopes and at projected images of our Sun,
showing a beautiful sunspot and of course the transiting Mercury moving across
our Sun’s surface. Thanks also go to my students who helped set up -
specifically Mike Stacy - and to Scott Moon who shot and published a nice
transit photo. Enough self-accolades.
The chart shows the evening sky during December – 8 pm early and 6 pm late in the month. Stars with an asterisk * attached are marked as dots in the chart.
Still high in the sky is the “summer” triangle,
made up of Lyra’s Vega*, Cygnus’ Deneb* - a long necked swan, shown
as the northern cross on the chart - and
Orion, the Hunter, is about to rise. It is many people’s favorite because of its brilliance. Four stars arranged in a rectangle - red Betelgeuse*, blue Rigel*, Bellatrix, and Saiph - outline the body, while three stars make up the belt - Alnitak, Alinalam, Mintaka - with the Orion nebula as the sword beneath it. Above Orion you find Taurus, part of it in the shape of an arrowhead including red Aldebaran*. And above that are the Pleiades* or Seven Sisters, a must for binoculars. To Taurus’ left is the pentagon Auriga with yellow Capella*. Beneath Capella appear Castor* and Pollux*, the twins in Gemini. And then we close this circle towards the horizon, with Procyon and the Number One: Sirius, the brightest star in the entire sky; both of which will rise about two to three hours after Orion.
Along with them the only night planet this winter will rise. Around midnight notice two bright objects standing above the Eastern horizon. The lower one is Regulus, the brightest star in Leo, the Lion, a constellation easily recognized as such. The other object is our solar system’s gem, Saturn. In high-powered and stabilized binoculars or in low-power telescopes one can get a hint at its rings and see its brightest moon Titan too.
For early risers, watch Orion setting in the West just before dawn. Now Regulus and Saturn appear high in the South.
Around December 14, the Geminid meteor shower will be at maximum with up to 75 meteors per hour. However, light from the waning Moon will interfere. Still, at that rate it may any year’s best meteor shower, even outdoing the Perseids in August which battle the all too bright Alaskan summer nights anyway. While almost all meteor showers are associated with debris from comets, the Geminids derive from the asteroid Phaeton’s jetsam.
Later in the month Jupiter can be glanced very low in the southeast just before dawn. Mars and Mercury would join the giant planet too but they’re rising too late in Alaskan skies.
The Sky in November 2006
The most exciting astronomical event this month is the Mercury transit on
Wednesday, November 8, from 10 am to 3 pm. I will have telescopes set up on the
KPC front lawn, equipped with proper solar filters. Only the two inner planets,
Mercury and Venus, can get between us and our Sun. Because their orbits
are tilted - and despite the fact that they only need 88 days and 225 days,
respectively - such so-called transits are rare (because usually they orbit too
high or too low): at least Mercury transits every seven years on the average
but Venus only twice every 130 years or so. I was able to see a Venus
transit soon in June 2004 from Barrow and plan on the 2012 one seen from
Winter has almost arrived and that means that the bounty of the beautiful
winter sky charmes us once more. The accompanying chart is set for 10 pm in
early evening and midnight in late November (notice also that South is at lower
left), thus more stars will have risen in the earlier evening hours later this
month. Finally Orion, Taurus, Gemini and Auriga are rising in the
East. With them are the bright stars of winter: red Betelgeuse and
Aldebaran, blue Rigel, yellow Capella and next to the twins' Pollux and Castor
appears Saturn, its rings nicely seen in a small telescope. Also included
is the star cluster of the Pleiades, best viewed with binoculars when up to 50
stars may be seen. Soon the bright stars Procyon and Sirius will follow.
Now in the Zenith are Cassiopeia's W and the House of Cepheus. Always
in the same place is the Little Dipper with Polaris and toward the Northern
horizon appears the Big Dipper. The kite-shaped Bootes is now setting
while the summer triangle consisting of Deneb (the Swan's tail), Vega and
Altair is getting closer to the Western horizon but will be visible until
January since Deneb and Vega are circumpolar in Alaska (they never set).
Apart from watching Mercury during an unusual time - broad daylight - Saturn is
the only planet that can be easily seen this month. It rises in the
Northeast around midnight in early November and around 10 pm late in the
month. High-power, stable binoculars or a telescope are needed to view
its rings.
The Leonids, now a weaker meteor shower, will show during the night of November
17/18.
Our Moon will show us an interesting spectacle. On and around November 7
(plus/minus two days), our Moon will be almost full and will rise at 4:25 pm
and will not set until 2:45 the next day which means our Moon can be seen for
22.5 hours straight. I call this the "Midday Full Moon" as the
winter Moon's answer to summer's Midnight Sun. This can only happen in
Northern latitudes and only in winter. For the same reason that the Sun
can stay up virtually all day when it is in Taurus in late June, the full Moon
appears in Taurus and Gemini and is up just as long. In fact, since its
orbit is tilted by 5 degrees, that pushes the latitude of the midnight sun from
the arctic circle (67 degrees, Coldfoot) to 62 degrees (Talkeetna) and even
further South because atmospheric refraction makes our Moon appear even above
the horizon as seen from the Kenai. The same event repeats in early
December. (See also an article about this by Ralph Hulbert,
http://www.alaskchem.com/moon.htm, in the
The Sky in October 2006
The
stars of fall are back: I highlighted easy to find constellations such as the
Big Dipper, the fainter Little Dipper, kite-shaped Bootes, W-shaped Cassiopeia,
house-like fainter Cepheus, cross-like Cygnus, the dashed-line Summer Triangle,
the Great Square of Pegasus, the arrow-like snout of Taurus, pentagon-shaped
Auriga.
I also highlighted the brightest stars with big dots. Big on star charts
means brighter - no matter how much stars are "magnified" in a
telescope, they're still pinpoints. But they appear brighter and perhaps
their color shows better, indicating the surface temperature of a star, ranging
from 5000 F for "cold" red stars, 11000 F for yellow stars, 20000 F
for white ones up to 40000 F for "hot" blue stars.
There are red Aldebaran in Taurus, yellow Capella in the Northeast, the twins
white Castor and orange Pollux on the northeastern horizon, red Arcturus in
Bootes - the Big Dipper's handle points to this star - and white Deneb, Vega
and Altair which make up the summer triangle; the fainter yellow North star
Polaris is designated by the little cross at the end of the Little Dipper's
handle. To the upper right of Aldebaran, look at the
Pleiades or Seven Sisters. Also of note is Albireo, actually a
double star, at the lower end of the cross with the brighter component showing
at a golden yellow in binoculars and the fainter one being blue.
The arrows show the direction in which the stars seemingly turn around Polaris
- due to Earth rotating in the opposite direction under the stars - with stars
setting in the West and new ones rise in the East.
Aside from these prominent stars and constellations, it's worth noting fainter
and harder to see constellations. Starting from the Southern horizon
going up towards Polaris I'll briefly describe Capricornus, Aquarius, Equuleus,
Delphinus, Lacerta and Cepheus. Capricornus and Aquarius are part of the
Zodiac, i.e. our Sun, our Moon and planets and most asteroids can be found
within these twelve constellations. Right now the planets Neptune and
Uranus can be spooted in Capricornus and Aquarius; on how to find them see my
September column or even better check out skypub.com which has some good finder
charts and features an online interactive star map rather than my static B&W
one. Equuleus means "little horse" and consists mainly of four
dim stars half way between Aquila Pegasus's
Although there are no special events this month, mark your calendar for
Wednesday, November 8, when Mercury will transit our Sun. I will announce
a public viewing for that.
The Sky in September 2006
Planets:
A very bright Jupiter can be seen very low in the Southwest just after
sunset. And a very bright Venus is visible very low in the East just
before sunrise.
Better situated is Saturn: it’s best seen by
commuters along the
September provides also the best chance to see the faint planets Uranus and
Neptune, hence the supplied charts of Aquarius and Capricorn. On a very
clear night without haze, you need to look very low on the Southern horizon
(best is at the
Stars: To first orientate yourself first, find the Big Dipper low in the Northwest; then extend the dipper's last two stars high into the North to find Polaris, the North Star, and the Little Dipper; with the Big Dipper on one side of Polaris, find the constellation Cassiopeia, a nicely shaped W, on the other side of Polaris high in the Northeast. Back to the Big Dipper, follow the curve of its handle toward the bright Red Giant Arcturus low in the West with its constellation of Bootes above, appearing as a kite or cone shape. Notice the bowl shaped Corona Borealis to its upper left. Prominently high overhead and extending to the South is the Summer Triangle, made up of the three bright stars Vega, Deneb and Altair. Deneb's constellation of Cygnus, the Swan, in a cross shape is easily seen; Vega's small rectangular shaped Lyra, the Harp, is prominent as well; while Altair's Aquila or Eagle may be depicted by its wings. But just on the upper left of Altair is the dolphin shaped small constellation Delphinus. Also prominent in the Southeast are the Great Square of Pegasus and low in the Northeast bright yellowish Capella with its pentagon shaped constellation Auriga. By morning, constellations have rotated towards the West with some of them having set while other have risen in the East. Those are Orion, Taurus, Gemini, Cancer and Leo as well as the planets described above.
Have fun observing, I'm looking forward to hopefully clear skies this winter and the Astronomy class I'll be teaching this fall.
Pluto: This is the IAU’s official definition on planets and other objects orbiting our Sun, with 237 yeah votes and 157 nay votes, 60% vs. 40%, among 424 astronomers present at the time of voting on August 24, 2006, at the meeting of the International Astronomical Union in Prague, Czech Republic, out of 2411 registered at the conference (the vote took place on the last day of the conference, hence rather few people voted), out of a few tens of thousands professional astronomers and millions of amateur astronomers world-wide:
(1) A "planet" [1] is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects [3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
Footnotes:
[1] The eight planets are: Mercury, Venus,
Earth,
Mars,
Jupiter, Saturn,
Uranus, and Neptune.
[2] An IAU process will be established to assign borderline objects into either "dwarf planet" and other categories.
[3] These currently include most of the Solar System asteroids, most
Trans-Neptunian Objects (TNOs), comets, and other small bodies.
The IAU further resolves:
Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
Astronomers seem to be divided about the decision as well as about Pluto’s status. As Pluto had been designated a planet for 75 years, in my opinion, the decision by the IAU to demote it to dwarf planet status is too new and the vote too contentious that the last word has not been spoken about it. So for at least the near future I go along with my preference which is that I continue labeling it as a planet. There’s not really a rationale behind it why I prefer Pluto being a planet – other than its long status as such – but perhaps with time I may change my opinion.
On a final note one may ask why there should be such a vote and if scientists can actually vote on scientific aspects. The answer to the first question is that there had not been an official definition of what a planet is, only the historical notion that planets are “wanderers” among the stars on the celestial sphere. The answer to the second question is that scientists are prohibited from voting on scientific issues because it’s nature and the evidence it reveals that determines scientific conclusions. However, voting on a definition is not about science: a definition of what a planet is is merely meant to categorize objects; hence the vote at the IAU conference is completely legitimate (as is the non-acceptance of individualized star names). In a similar vein, the taxa (kingdom, phylum etc.) used in biology simply categorize organisms and these definitions are agreed upon by biologists; on the other hand, all scientific conclusions in biology are based on data that nature provides, not biologists’ opinions or votes.
A few years ago astronomers voted that based on the data, the universe is not only expanding but that its expansion is even accelerating. Now that is a scientific conclusion (based on the data) for which a vote – even among respected astronomers – is meaningless.
Not needed:
Zodiac:
From August 10 through September 16 our Sun has been traveling through Leo and until October 30 it will be in Virgo. The astronomical path is different from astrology (Virgo and Libra in September) because the tilt of the Earth’s axis is continuously changing (precession) and hence our Sun is about one Zodiac constellation behind from where it was 4000 years ago when the signs became stylish. However, since our Sun is inside these constellations, they’re not visible anyway right now. More interesting is a constellation that’s exactly opposite Leo which is Aquarius.
This is probably the best month to see Aquarius, visible about half a year away from its assigned time (February). Best time to find it is on September 6 and 7 when the full Moon resides in that constellation. Between dusk and dawn find our Moon low on the southern horizon.
Eclipses:
Two eclipses occur this month but
neither of them is visible from
The next lunar eclipse viewed from
The Sky in April 2006
Days are getting longer and nights are getting shorter. We're also
leaving the freezing cold behind. As we all love winter's benefits, we
surely regret that our beloved starry skies will take a back seat soon.
But at least we get some nice views for a good-bye.
With Daylight Savings Time having started, it doesn't get dark until 10
pm or even later and therefore the diagram shows the Southeastern sky around 11
pm with very bright Jupiter making up a beautiful isosceles triangle with the
bright stars Arcturus and Spica, which they will continue to depict throughout
spring of this year. For the diagram itself I chose April 13 because the
full Moon appears between Spica and Jupiter; the day before it's next to Spica,
the day after next to Jupiter, showing nicely our Moon's West-to-East motion as
it's orbiting us.
I'm alternating between two planetarium
software, Redshft 3 and Starry Night Pro, to draw my diagrams: since SNP
shows landmarks on the horizon, I chose it and as I was running it, I noticed
that there are quite a few bright satellites orbiting through this part of the
sky. One distinguishes satellites from airplanes since the former' paths
of flight are very linear and stable, seem very high up and brighten up, then
fade; that's due to them reflecting our Sun's light, which is beneath the
Western horizon at this time, more or less efficiently, in fact, the satellites
fade as they enter Earth's shadow in the East or are rather backlit in the
West. The best web site to check for satellite fly-bys is
www.heavens-above.com (Chris Peat in
Saturn is still visible: you find it as it makes a very
obtuse triangle with Gemini's Castor and Pollux low in the West. The pretty
Beehive cluster (great in binoculars) is just to the left of Saturn and can be
seen with the naked eye, as I noticed even in locations where some streetlights
are diminishing the view. In a small telescope Saturn's rings can be
spotted, some of its moons, especially Titan, and Jupiter's four large moons as
well.
Mars is rapidly moving from Taurus into Gemini, during April
it can be seen above Orion on the Western horizon, however rather early during
dusk. With it the winter sky with its brilliant stars and constellations,
Sirius, Procyon, Aldebaran, Castor, Pollux, Capella, Betelgeuse, Rigel, Orion,
Taurus, Gemini, and Auriga, is giving its last hooray for the season until we
meet them again in November, to which, I'm positive, we're all looking forward
to.
Venus and Mercury appear so low during dawn in Alaskan skies
that it may be better to look at them during a trip to the second-largest state
in the
The Sky in March 2006
Since the winter sky appears now in all its splendor,
I just show the most interesting and most beautiful part of it, all those
bright stars in the South; instead of the entire sky as I usually do.
There is the hunter Orion with its belt and sword and the bright stars
Betelgeuse and Rigel. By themselves are Sirius and Procyon in the Big Dog
and the Little Dog, respectively, forming a nice straight line with Saturn
which itself is just to the right of the Beehive cluster. The twins,
Gemini, are marked by Castor and Pollux. The pentagon of the charioteer
Auriga with bright star Capella appears highest. And the bull Taurus with
Aldebaran and the cluster of the Pleiades hosts Mars. Enjoy.
The planets: aside from the just mentioned Mars and Saturn,
around midnight Jupiter rises in the East and becomes prominent in the low
Southeastern sky during the rest of the night; Venus rises just ahead of our
Sun but it's so low in the sky that one has to scan the Southeastern horizon
carefully during dawn.
A total solar eclipse will visit Northern Africa,
A friend of mine told me of an office discussion she had:
are winter days and nights in Barrow completely dark or does our Moon supply
some light? I haven't been in Barrow in the winter (I'm still failing to
convince my wife of this opportunity), so I can't answer that first hand.
But some astronomical knowledge does supply the answer. For one,
since our Sun is closer beneath, but not above, the Southern horizon during
mid-day, I imagine that the sky looks like dawn and dusk for a few hours.
And then there's our Moon perhaps in the sky, depending on its position
in its orbit. Both Sun and Moon as well as
planets and asteroids move along or at least very close to a path called the
ecliptic, a circle that stretches across the sky through the Zodiac
constellations. (Moon, planets and asteroids do that while in the case of
our Sun it's actually us, Earth, which is orbiting; but from our vantage point
it seems that our Sun is the orbiting body. And that's the necessary
vantage point used in this discussion.) Our Sun sweeps through these
constellations once per year, i.e. relatively slowly. Since Taurus,
Gemini and Cancer are Zodiac constellations that appear quite high in the sky
(in the Northern hemisphere) and our Sun moves through them between May and
August and becomes circumpolar (meaning that it never sets), that's when we
have summer. And since Scorpius, Sagittarius and Capricornus are really
low in the sky (in fact, they're for the most part not even visible from
Barrow) and that's where our Sun is from November to February and therefore
barely rises above the horizon, we have winter at that time. Our Moon on
the other hand moves through these constellations once a month, i.e. relatively
fast. So once per month, every month, it's very high in the sky and
circumpolar in Barrow for a few days; and every month it's below the horizon
all day (and night) long for a few days. For example, during most of
December our Sun is in Scorpius and thus never rises. But when our Moon
is in Taurus, as it was in mid-December, it itself is circumpolar and very high
in the sky. Since Taurus is in the opposite part of the sky from
Scorpius, our Moon was also full at that time: Barrow must have had beautiful
circumpolar full Moon nights and "days" during mid-months this past
winter.
The Sky in February 2006
I, the Sky Guy, the Great Astronomer, have to admit that I
have not used my telescope in more than a month. Between school starting,
the many cloudy evenings, the hassle of assembling the telescope in a cramped
garage versus keeping it safe from our 1 year old son, and our sub-zero
temperatures, it just wasn't feasible. I'll get better at it though as I have
scheduled some astronomy evenings for one of my classes during February.
If you like to join, send me an e-mail or call me.
The evening sky has changed so little from January that I
actually recycle the diagram from last month (Mars has shifted a bit towards
the Pleiades). I outlined the following constellations that should be
easy to find because they're highly recognizable: the Big Dipper high in the
Northeast, Orion in the South, Auriga (a Pentagon) high in the South, the
Square of Pegasus in the West, the Cross of Cygnus in the Northwest;
furthermore, these take a moment to find: the lion Leo in the East, the Snout
of Taurus the Bull (also in the shape of an arrowhead) above Orion, the Little
Dipper high in the North (use the pointer stars in the Big Dipper to find
Polaris), the W of Cassiopeia on the Western side of the Little Dipper,
opposite from the Big Dipper.
The labeled stars are the brightest ones in the winter sky;
I'm labeling them beginning in the middle, then spiraling counterclockwise:
Capella (6th), Castor (45th), Pollux (16th), Beehive cluster, Saturn
(a planet), Regulus (21st), Procyon (8th), Sirius (1st), Betelgeuse (10th),
Rigel (7th), Aldebaran (13th), Pleiades (another cluster), Mars
(another planet), Deneb (19th), Vega (5th), and Arcturus (3rd). There are
some stars in the Big Dipper and in Orion that are brighter than Polaris (49th)
but obviously Polaris seems more important. See if your observations of
the brightest stars match the offical list as I cited it; if not, think about
what could make them appear different to your eyes; and see how the planets fit
into this brighness scale.
Still long after midnight, Arcturus will be joined by Spica
(15th) and Jupiter, resembling a beautiful right triangle in the Eastern sky.
Despite its wee hours appearance we need to enjoy Jupiter now because it
will shine at its best in summer when we hardly get dark skies. Then
again, perhaps Jupiter will be the only bright object we can see in June and
July.
This month I like to talk about the constellation Leo.
Among the 88 constellations it also belongs to the few that can be
recognized easily as what it should depict, i.e. a male lion lying down with
his tail behind him and a faint mane above his body. The bright star
Regulus is his front paw. I consider Leo a quick constellation in the
sense that it can be seen for an only relatively short time in the evening sky,
from January to April. Of course it "moves" just as fast as the
other constellations but, as we're getting out of winter into spring, our
evenings get shorter as our Sun rises later. Thus Leo isn't in the
evening sky for very long and hence I also regard it as a messenger for spring
to arrive (imagine that).
Leo is also a prime example for explaining the meanning of
the Zodiac constellations. People born July or August have the sign of Leo (I'm not expounding on Astrology but that's the
only overlap this quackery has with the science of Astronomy). During
those months, a Zodiac constellation can't be seen because by definition that's
where our Sun is. Instead we can observe it half a year removed.
E.g. I have to wait to see my constellation of Aquarius until early fall.
Next month I'll talk about the total solar eclipse that will
be visible in Northern Africa,
The Sky in January 2006
I
don't know if people in other professions do this and I don't know about other
teachers, but I'm of the sort who constantly thinks about how I can use a
particular situation or event in the classroom. For instance, while
driving (and paying attention), I think about all the physics that's involved
that makes the car move and how I can use that in class. Or I may kayak
for leisure (in the summer) and make up lesson plans in my head. It's
quite bothersome.
When I moved here a few years ago, I knew that I'm just about 7 degrees too far
South to see the Midnight Sun but it crossed my mind that due to our Moon's
inclined orbit (by 5 degrees) we could actually almost see a Noon Full Moon.
I made that term up. It's quite bothersome. I think back then
I even figured out when that should happen: December 2005. Well, I spaced
that. If you noticed the full moon very high in the evening sky last
month, it wasn't because you read my column. So my little story is just
about saying sorry.
But why write about events past if they repeat? I'm looking forward to
December 2006 when this happens again and the full Moon will be 58 degrees
above the horizon around midnight and will rise barely East of North and set
barely West of North, both occurring around noon. Enough for now, I will
bring this up in my next December column.
But back to this month: our Moon does have an interesting event in store for us
as it will occult the Pleiades cluster during the night of January 9/10, Monday
to Tuesday. On Sunday, the 8th, or before that day, check on the Pleiades
in Taurus and notice that our Moon is closing in on it (passing by Mars in the
process). On Monday, you may notice the almost full moon very low in the
East even before sunset. After nightfall, around 6 pm, notice
that there are no Pleiades. Then follow our Moon through the night and
glimpse the Pleaides again, emerging on the right side of our Moon (its East
side but our Western direction) shortly before midnight. By the way, the
effect of an occultation is the same as that of an eclipse, as we don't see the
occulted object; the difference is that no shadows are involved.
Venus retreats from the evening sky in January, it
hasn't been a great Venus apparition anyway. But we will enjoy it as a
morning planet throughout the entire spring. Whenever you make an early
trip to Acnchorage, starting just before dawn and driving East on the
The chart shows the sky around midnight in early January and around 10 pm in
late January. Highlighted constellations in the North are Cygnus, the
Swan or Northern Cross, and the stars Deneb and Vega (notice the first letters
used); in the Northeast the star Arcturus (the Big Dipper's handle curves
toward it); in the West the Great Square of Pegasus; overhead the Big Dipper,
the Little Dipper with Polaris, and the W of Cassiopeia; and in the South the
glorious winter sky with the constellations Orion, the pentagon of Auriga, the
snout of the bull Taurus (looks also like an arrowhead) and Gemini, the twins,
with the bright stars, listed counterclockwise, Betelgeuse, Rigel, Aldebaran,
Capella, Castor, Pollux, Regulus, Procyon and Sirius with Mars and Saturn
flanking them. Also highlighted are the star
clusters of the Pleiades and Beehive, the latter is found with binoculars as it
lies just to the upper right of Saturn.
Last month I described Auriga, this month I like to cover Orion, the Hunter,
that most famous of constellations. Mostly it's famous for being so
easily recognizable and made up of so many bright stars. There are
Betelgeuse (right shoulder) and Rigel (left foot), one a Super-Red-Giant, the
other a Blue Giant. Even the untrained human eye should easily see the
non-white color of a small number of stars: our yellow Sun, the Red Giant stars
Aldebaran, Antares, Arcturus, Betelegeuse, and the blue Giant Rigel. The
other prominent five stars in Orion are also blue but it only shows in
telescopes, which collect more light and therefore enhance color. Those
are Bellatrix (left shoulder), Saiph (right foot), and Alnitak, Alnilam and
Mintaka which make up the belt (in East to West order). There is also the
Orion nebula, just visible with binoculars. In a good amateur telescope,
the trapezium of very hot, blue, and young stars can be glimpsed, those
progenitors of all the stars that are about and will be born in this stellar
nursery. Just South of Alnitak lies a bright
nebula (the term meaning "it looks like haze") against which a dark
nebula is silhouetted in the form of the Horsehead Nebula, also a sight for
large amateur telescopes.
As an afterthought, we're closest to our Sun on January 4, at 91, 405,953 miles
(the perihelion), exactly 3,101,962 miles closer than on July 3 (the aphelion).
And on Thursday, Janaury 5, I'll have my telescopes pointed at some of
the marvels described above, starting around 5:30 pm, on the KPC parking lot
during our Open House and walk-in registration.
The Sky in December 2005
The
dominating constellation is Orion, the Hunter. It is many people’s
favorite because of its brilliance. Four stars arranged in a rectangle
(with red Betelgeuse, blue Rigel, Bellatrix, and Saiph) outline the body, while
three stars make up the belt with the Orion nebula as the sword beneath
it. Above Orion you find Taurus, part of it in the shape of an arrowhead
including red ALDEBARAN. And above that are the Pleiades or Seven
Sisters, a must for binoculars. To Taurus’ left is the pentagon Auriga
with yellow CAPELLA. Beneath Capella appear CASTOR and POLLUX, the twins
in Gemini. And then we close this circle towards the horizon, with Procyon and
the Number One: Sirius, the brightest star in the entire sky. Since
Jupiter resides further East , also look for Cancer and
Leo.
If you're wondering why some of the above constellations don't show in the
diagram, you're right: above I described the late evening sky and since I trust
that you'll be able to find Orion, I opted to show the early evening sky
instead so that you can locate one very bright object, that is planet.
See the text below.
However, there is more in the sky: the huge summer triangle is called that way
because it’s the dominant feature in the summer sky but is still visible
until January in the West. It is comprised of VEGA, DENEB and ALTAIR,
another three of the brightest stars. Since these three stars are from
different constellations (Lyra, Cygnus,
If you happen to be in a dark area, even a turn-out on the
How do you find the North star Polaris? Take the last two stars of the
Big Dipper’s pan and mark off a distance five times their separation,
towards North. You’ll always end up at Polaris which is the last
star of the smaller and fainter Little Dipper. Since the Little
Dipper’s stars are fainter, you might need to be in a darker area without
light pollution. You can also depict the two dippers as if you were
flipping pancakes forth and back between the two. Polaris is only 49th in
brightness and thus appears way fainter then most people expect: its claim to
fame is its fixed position of 60 degrees (marking one’s latitude) above
the Northern horizon, not its brightness.
Venus is by now in the constellation Capricornus but is finally high enough the
SSW horizon that it can be seen as a bright beacon during dusk: look in that
direction, then turn around and see Mars is high in the Eastern sky, some
distance from the Pleiades; it's a nice spectacle. Saturn rises earlier
in the evening and is still following Castor and Pollux. And Jupiter
appears brightly in the Southeast during dawn.
This month I like to mention the constellation Auriga a little more in
depth. It looks like a pentagon and is high in the eastern sky during
evening, placed between Taurus (Aldebaran, Pleiades, and currently Mars) and
Gemini (Castor, Pollux, Saturn). Its brightest star is Capella, its
diameter is 13 times larger than our Sun (12 million miles compared to 900,000
miles), its spectrum is very similar and hence its temperature of 11,000 F as
well and - it's yellow, a color you may be able to see with binoculars.
Putting these numbers together yields an energy output about 160 times as
much as our Sun's but of course at its distance of 45 lightyears, only some of
its light reaches us, making it the sixth brightest star in appearance from our
solar system (Sun excluded). Auriga lies also inside the Milky Way, so
you see more (fainter) stars looking at it while for example looking at the Big
Dipper. Not coincidentally it also bears some open clusters as these
conglomerates of several hundreds of stars each were formed within our galactic
disk. These have the prosaic names M37, M36, and M38. All are
towards the lower left corner of the pentagon (the opposite side from Capella)
and while each at magnitudes 5.5 to 6.5 are just on the brink of naked eye
visibility, all three are fine objects for binoculars. M37 contains about
150 stars within a diameter of 25 ly and at a distance of 4600 ly; M36 has only
60 stars within 14 ly and at 4100 ly from us; and M38 has about 100 stars
within 25 ly and at 4200 ly from us. Since all three are at roughly the
same distance from us, they all appear almost equally bright.
Last but not least, my community schools Astronomy class has its last evening
on Wednesda, December 14 at KPC.
The Sky in November 2005
Winter
has almost arrived and that means that the bounty of the beautiful winter sky
charms us once more. The accompanying chart is set for 10pm in early evening
and midnight in late November, thus more stars will have risen in the earlier
evening hours later this month. Finally Orion, Taurus, Gemini and Auriga
are rising in the East. Inside these constellations are the bright stars
of winter: red Betelgeuse and Aldebaran, blue Rigel ,
yellow Capella and next to the twins' Pollux and Castor appears Saturn, its
rings nicely seen in a small telescope. Also included is the star cluster
of the Pleiades, best viewed with binoculars when up to 50 stars may be
seen. Soon the bright stars Procyon and Sirius will follow. Now in
the Zenith are Cassiopeia's W and the House of Cepehus.
Always in the same place is the Little Dipper with Polaris and toward the
Northern horizon appears the Big Dipper. The kite-shaped Bootes is now
setting while the summer triangle consisting of Deneb (the Swan's tail), Vega
and Altair is getting closer to the Western horizon but will be visible well
into January since Deneb and Vega are circumpolar in Alaska (they never set).
Mercury and Venus are visible during dusk; however, they’re very low in
the sky this month since they’re in the constellations of Scorpius and
Sagittarius, respectively, and those two are very low constellations as seen
from
Mars rises around sunset, though of course in the East. It is followed by
the star cluster Pleiades and red Aldebaran, both in Taurus; look for an
elongated triangle made up of these three objects. Mars is in opposition
this month which means it’s closest to us. You might be able to see
a disk in binoculars but definitely use them for marveling at the stars in the
Pleiades. By mid-November, the full moon has joined Mars.
Once Taurus is up and after Gemini has risen by late evening, around midnight perhaps, look for Saturn following suit in
Cancer. Again use binoculars (probably without hope for seeing the rings;
a small telescope would be needed) but scan just a little ahead from Saturn to
look at another pretty star cluster, the Beehive in Cancer. A gibbous
moon will accompany Saturn around November 21.
Jupiter rises shortly before dawn in the Southeast. And since
Also, my community school class starts on Wednesday, November 9 (instead of
11-02), at KPC around 7:15 pm. If it’s clear, we’ll
definitely be outside observing. Around that time our Moon will be full
and since that compromises views of the starry skies anyway, I prefer a more
convenient viewing area such as KPC’s gravel pit across from our parking
lot.
The Sky in October 2005
The stars of fall are back: this time I highlighted easy to find constellations
such as the Big Dipper, the fainter Little Dipper, kite-shaped Bootes, W-shaped
Cassiopeia, house-like fainter Cepheus, cross-like Cygnus, the Summer Triangle
(dashed line), the Great Square of Pegasus, the arrow-like snout of Taurus,
pentagon-shaped Auriga. I also just highlighted the brightest stars
(though I abstained from naming them on the chart, fearing information
overload), red Aldebaran in Taurus, yellow Capella in the Northeast, the twins
Castor and Pollux on the NE horizon, red Arcturus in Bootes (the Big Dipper's
handle points to this star), and Deneb, Vega and Altair that make up the summer
triangle; the fainter North star Polaris is designated by the little cross at
the end of the Little Dipper's handle. To the upper right of Aldebaran,
look at the Peiades or Seven Sisters while Mars
completes the views in Taurus. The arrows show the direction in which the
stars seemingly turn because of Earth rotating in the opposite direction under
the stars. That means that stars set in the West and new ones rise in the
East during the night, including the planet Saturn which will show itself
around 2 am.
On Monday, October 17, a partial lunar eclipse will be visible from 3:30 am to
4:30 am in
Good sources for information are as always the two major magazines in the
Now latitude is a diiferent story. In Southcentral
I also like to advertise the class I'll be teaching for Community Schools
(262-...), starting Wednesday, November 2.
The Sky in September 2005
This would be a good month to watch Venus and Jupiter during dusk but we just
too far north. Both planets and our Sun set virtually at the same time as
seen from
Mars in Taurus rises around 10 pm and is visible the entire night. It too
is a winter planet, making a beautiful triangle with the red giant star
Aldebaran and the star cluster Pleiades.
Saturn in Cancer is the dominant object in the pre-dawn skies. With
average binoculars you probably won't see its rings but look right above it and
you see the beautiful Beehive cluster. You can actully see that without
binoculars using averted vision (out of the side of your eye, not directly
looking at it). Saturn's rings are visible with powerful binoculars or a
small telescope.
The chart shows the sky at 3 am throughout September. I used that unusual
time to squeeze Saturn on it. For views earlier during the night and in
the evening, imagine to rotate the chart clockwise, so that stars in the
Northwest, West and Southwest are high in the South, stars beneath the horizon
are in the West (described below) and stars in the Eastern parts have not yet
risen. Still, this doesn't compromise the chart's usefulness.
For the stars themselves: since we are now able to actually see stars in once
again dark environs; this is for the evening sky. To first orientate
yourself first, find the Big Dipper low in the Northwest; then extend the
dipper's last two stars high into the North to find Polaris, the North Star,
and the Little Dipper; with the Big Dipper on one side of Polaris, find the
constellation Cassiopeia, a nicely shaped W, on the other side of Polaris high
in the Northeast. Back to the Big Dipper, follow the curve of its handle
towards the bright Red Giant Arcturus low in the West with its constellation of
Bootes above, appearing as a kite or cone shape. Notice the bowl shaped
Corona Borealis to its upper left. Prominently high overhead and
extending to the South is the Summer Triangle, made up of the three bright
stars Vega, Deneb and Altair. Deneb's constellation of Cygnus, the Swan,
in a cross shape is easily seen; Vega's small rectangular shaped Lyra, the
Harp, is prominent as well; while Altair's Aquila or Eagle may be depicted by
its wings. But just on the upper left of Altair is the dolphin shaped
small constellation Delphinus. Also prominent in the Southeast are the
Great Square of Pegasus and low in the Northeast bright yellowish Capella with
its pentagon shaped constellation Auriga. By morning, constellations have
rotated towards the West with some of them having set while other have risen in the East. Those are Orion, Taurus,
Gemini, Cancer and Leo as well as the planets described above.
Have fun observing, I'm looking
forward to hopefully clear skies this winter and the Astronomy class I'll be
teaching this fall.
The Sky in August 2005
The astronomy season starts out in grandeur as the first major planet will be
Mars at its best. It’ll be joined by Venus and Jupiter early this
fall and Saturn later this year.
The red planet has been an odd-year planet throughout the 90s and 00s, i.e. it
became last prominent in 2003, then now obviously, and next time in late
2007. Mars needs about 1 year and 11 months for one orbit. So as
Earth orbits our Sun and returns to the same spot after exactly one year, Mars is
almost on the other side of our Sun. As we’re trying to catch up
during our second orbit, Mars makes the feeble attempt to elude us, but finally
we’ve caught up and get closest to Mars once again after 2 years and 2
months. Hence the two year recurrence of Mars from our vantage point.
As for late 2005 and early 2006 Mars is moving across Aries from July on until
January where it will also start retrograding in October with our closest
approach on November 6 (Mars' opposition), the on through Taurus in February
and March and through Gemini in April and May of next year.
We like to be close to Mars to observe it because we can only see it when both
of us are on the same side of our Sun, else our Sun
would be in between, rendering Mars obliterated by the bright daytime skies, as
will be the case for the remainder of 2006. But we also like to be closer
to a planet because it appears brighter and bigger, which is especially the
case for Mars. Once again, Mars is in the news for allegedly being closer
than ever - quite forgetting that that happened two years ago.
Nevertheless, Mars is a great sight every other year.
You can’t miss reddish Mars in the East or South, depending on the time
of night , because it’s be the brightest object in the night time sky,
apart from our Moon if that is out . The diagram shows the positions of
Mars during August and September around
There are some bright stars out but none of them is nearly as bright as Mars,
though some of them could be mistaken for Mars. These stars are reddish
Arcturus and Antares in the West and Southwest: these are huge, though cool
[radiating at around 5000 F which corresponds to red] dying stars called Red
Giants, hence unlike Mars which gets its color from its oxidized, rusted
surface rocks. Other bright stars make up the summer triangle overhead, Vega,
Deneb and Altair .
As
every year, August brings the most famous and probably best known meteor show,
visible around August 11-13, Thursday and Friday nights this year. As we
on Earth orbit our Sun, we intercept the orbits of comets (just the orbits, not
the comets themselves, they're in other positions of their orbits) and are
"pelted" by the the debris of these comets that is strewn throughout
their entire orbits: mostly fine dust particles, at best tiny rock pebbles. In
August of each year, we're passing through the orbit of comet Swift-Tuttle and
when we look down its orbit we see the constellation Perseus. Therefore
it appears that the dust particles in Swift-Tuttle's wake are coming from
Perseus and hence the meteor shower is given the name Perseids. These
dust particles then burn up in our atmosphere, creating what's called meteors.
The accompanying diagram shows what you perhaps could see during the
morning hours of August 12. Here you're looking high towards the South.
Try to take photos with a camera that allows time exposures, use a wide angle
lens.
Comets are named after their discoverer(s), in this case independently by
Americans Lewis Swift and Horace Tuttle who noted the comet in 1862; this was
also the first instance that a comet and a meteor shower were shown to be
related phenomena. The comet also goes by the designation 109P, the P
meaning it's a periodic comet that returns in regular intervals, the number
meaning it's one among 164 such comets: designation 1 goes to Halley, 9 to
Tempel (that's the one with which NASA's Deep Impact probe collided last
month). Swift-Tuttle returns every 130 years or so. In fact when it
was rediscovered in 1992, its orbital data didn't correspond with the previous
ones. Instead, a non-gravitational computation provided a better fit.
That sounds counter-intuitive at first since gravitation really