What’s Up in the Sky – December, 2010
By Peter Burkey

This is a “good news/bad news” month.  The good news is there will be a total eclipse of the Moon visible from North America on the night of December 20-21, the first one we have been able to see since February, 2008.  The bad news is that totality does not start until 2:41 a.m.

A lunar eclipse occurs when the Moon passes through the shadow of the Earth.  Unlike a solar eclipse, which is visible only along a narrow path on Earth’s surface, a lunar eclipse is visible to anyone who can see the Moon.  Since lunar eclipses can be seen (assuming the sky is clear) from the entire night side of the Earth, they are much more frequently observed from any particular location than are solar eclipses.  The next total eclipse of the sun visible from the US will not be until 2017.

A lunar eclipse can only take place when the Moon is full.  About 20 minutes before the Moon reaches the dark central shadow of the Earth, it dims somewhat as the Earth partly blocks the sunlight.  As the Moon begins to move into the shadow, the curved shape of the Earth’s shadow can be seen.  Aristotle listed the round shape of the Earth’s shadow as one of the earliest proofs of the fact that the Earth is spherical.

Even during totality the Moon is still visible, appearing a dull, reddish color.  This is due to sunlight which has passed through the Earth’s atmosphere and has been bent by the air into the Earth’s shadow, sort of like all the sunsets on Earth being cast on the Moon.

Besides this spectacular event, which occurs in the wee hours of the morning, an easier sight can be seen the next few days.  Look SE tomorrow morning around 7:00 a.m. for bright Venus.  To the upper right of the planet is the crescent Moon and above that can be seen Saturn.  For those of you with an early morning commute, these two planets will put on a pretty good show up in the sky.
This month in history:
Dec. 3: Pioneer 10 spacecraft makes closest approach to Jupiter – 1973
Dec. 7: Apollo 17, final Moon landing mission, launched – 1972
Dec. 11: First auction of Soviet space hardware and artifacts – 1993
Dec. 14: Gene Cernan, Apollo 17 astronaut, is last human to walk on Moon – 1972
Dec 17: Orville Wright makes first powered flight –  – 1857
Dec. 24: Apollo 8 makes 10 orbits of the Moon – 1968
Dec. 27: Meteorite ALH 84001 discovered – 1984
Dec. 31: First flyby of Saturn’s moon, Iapetus, made by Cassini spacecraft – 2004

Here are this month’s viewing highlights:
Planets this month:  Jupiter is high in south at nightfall, great for telescopic viewing.   Saturn and Venus are “morning stars” visible in the SE before dawn.

Dec. 2:  Waning Crescent Moon lower right of Venus in predawn sky.
Dec. 5: New Moon
Dec. 13: First Quarter Moon
Dec. 13-14: Geminid meteors peak
Dec. 21: Full Moon – lunar eclipse 2:40 – 4:00 a.m.
Dec. 21: Winter solstice – first day of winter – 6:38 p.m. EST
Dec. 27: Last Quarter Moon

What’s Up in the Sky – November, 2010
By Peter Burkey

The connections people have to astronomy vary widely and are sometimes very subtle or even unknown.  Recently a friend noted that he often scans the weather page in the newspaper, noting the times the Sun and Moon rise and set.  Occasionally he notices that either the Moonrise or Moonset is listed as “none”.  “How can that be?”, he asked.  “Doesn’t the Moon rise and set every day?”  We all got a chuckle out of “none”.

But it got me thinking.  Sometimes newspapers make mistakes.  Maybe the feed to the Naval Observatory was down that day.  But it was always moonrise or -set, never sunrise.  And I knew I should be able to answer his question but, I must confess, it took GVSU Professor Douglas Furton and a Google search to jar my memory.

The fact is that there actually are days when the Moon does not rise (or set).  The reason has to do with the time between successive risings or settings.  You probably know that the Sun sets a few minutes earlier or later (depending on the season) each day.  But the Moon sets, on average, fifty minutes later each day.

The reason is because the Moon orbits the Earth in the same direction as the Earth turns on its axis so at the same time on successive nights it appears to move from west to east in the sky.  This means the Earth has to make a little more than one rotation before the Moon sets again and this takes a little more than 24 hours.

And, because the Moon orbits the Earth, it can, and does, rise and set at all hours of the day.  So, suppose the Moon sets at 11:45 p.m. on Monday.  The following night it may set 45 minutes later, for example, at 12:30 a.m. which will be Wednesday, so the Moon did not set on Tuesday.  About two weeks later the same situation holds for Moonrise.

So, a basic knowledge of some fundamental principals in astronomy is needed to understand some obscure entry on the weather page.  But that is just one example of the many things in our world that can be understood through science. From what makes the stars shine to how far away the galaxies are, science enables us to answer many questions about what’s up in the sky. 

This month in history:
Nov. 3: The dog Laika is first living creature to orbit Earth, aboard Sputnik 2 – 1957
Nov. 9: Carl Sagan born. – 1934
Nov. 16: Interstellar message broadcast from Arecibo radio telescope – 1974
Nov. 19: Second lunar landing made by Apollo 12 – 1969
Nov. 30: Ten-pound meteorite strikes and bruises Alabama woman, Elizabeth Hodges  – 1954

Here are this month’s viewing highlights:
Planets this month:  Jupiter continues to dominate the southern sky all night.  Venus and Saturn are in the ESE before dawn.

Nov. 6: New Moon
Nov. 13: First-quarter Moon
Nov. 17,18: Peak of Leonid meteor shower, best  before dawn.
Nov. 21: Full Moon
Nov. 28: Last-quarter Moon

What’s Up in the Sky – October, 2010
By Peter Burkey

It’s Jupiter time!  Anyone who has been out at night lately has certainly noticed the bright object in the southeast sky.  This brightest “star”  is actually the planet Jupiter and it is in a great position for observing with a telescope.  This month Jupiter rises just before sunset and is well up in the southern sky by the time darkness sets in.  Also, we are relatively close to the planet so it appears relatively large. 

When observing Jupiter, you will want to focus on two things: its surface features and its moons.  Remember that Jupiter is a giant ball of gas, ten times the diameter of Earth, so when we talk about “surface features” we are referring to the patterns visible in the cloud tops.  Jupiter’s atmosphere is mostly hydrogen and helium with small amounts of a few other chemicals like ammonia and methane.  It is these chemicals that form the features such as the Great Red Spot (a giant atmospheric disturbance) and  equatorial bands of various colors.  These can be observed with a modest scope at average magnification.

I always enjoy observing the moons of Jupiter the most.  After all, watching them orbit the planet from night to night was one of the pieces of evidence that helped Galileo figure out the solar system.  And you can watch them disappear behind the planet or pass in front of it.  If you have good eyes and a fairly decent telescope, you can even see the shadows of moons cast on the cloud tops.  One of the best opportunities for that comes on the evening of October 23.  Start observing about 9:30 p.m. Over the course of the next hour, you should be able to see one moon disappear behind the planet and two pass in front, each casting its shadow on the cloud tops.

As an added bonus, Uranus is also visible about two finger-widths to the left of Jupiter.  With a low power eyepiece, you should be able to get them both in the same field of view.

So dust off the scope and enjoy good views of the King of the planets, one of the neatest objects up in the sky.

This month in history:
Oct. 1: First observations with 300-foot radio telescope at Green Bank, WV – 1962
Oct. 4: Space Age begins when Sputnik 1, first artificial satellite, is launched – 1957
Oct. 10: Triton, one of Neptune’s moons, is discovered by Wm. Lassell – 1846
Oct. 13: M51 (the Whirlpool Galaxy) observed by Charles Messier – 1773
Oct. 24: 199th and final flight of X-15 rocket ship – 1968
Oct. 30: STS-61A Challenger Space Shuttle launched – 1985

Planets this month:     Venus, low in SW at sunset, is gone by mid-month.  Jupiter dominates southeastern sky after dark. Uranus can be found in binoculars just to the upper left of Jupiter.
Oct. 7: New Moon.
Oct. 6: One-half hour before sunrise look for crescent Moon with Mercury to its left near eastern horizon.
Oct. 14: First quarter Moon.
Oct. 21-22: Peak of Orionid meteors.
Oct. 22: Full Moon
Oct. 30: Last quarter Moon.