This is Dudley Observatory's Skywatch Line for Friday, October 31, through Tuesday, November 2, written by Alan French.

The Moon was new on Tuesday and has returned to the evening sky. If you have a good view to the southwest, you can catch a crescent Moon below Venus on Friday night. Look for brilliant Venus almost ten degrees above the southwestern horizon at 5:30 PM. Below and slightly right of Venus, a little more than halfway to the horizon, you'll see the slender Moon.

The Moon and Venus will be a lovely sight at 5:45 PM on Satuday night, with a somewhat fatter crescent Moon appearing to the left of Venus. At the same time on Sunday night, the crescent Moon will be halfway between Venus and Jupiter, with Jupiter in the south-southwest and the highest of the trio.

When you look at the Moon over the weekend, note that you can see the entire Moon, with the larger portion shining faintly within the bright crescent. If you were up on the Moon, you would see a nearly full Earth in the sky, and it is this bright Earth that illuminates the portion of the Moon still in night and free of sunlight. The gentle glow we see is called “Earthshine.”

Right now the line between bright sunlight and Earthshine on the Moon, known as the terminator, is the sunrise line, and the light of the Sun is marching relentlessly across the visible face of the Moon as we move toward the next Full Moon. Along the terminator the Sun is low and shadows are long, so detail stands out in bold relief. Any optical aid – binoculars, a spotting telescope, or an astronomical telescope – will reveal craters and mountains along the terminator. Often you will spot points of sunlight over in the darker portion of the Moon as mountains and the higher crater walls catch the first light of the rising Sun. It can be fun to watch the progress of sunrise over these mountains and craters, and it doesn't take long to see the changes produced by the rising Sun.

The first four asteroid, Ceres, was discovered on January 1, 1801. It was thought to be the “missing planet” between Mars and Jupiter. However, three more asteroids, Ceres, Pallas, and Juno, had been discovered by 1807. Ambitious skywatchers with modest telescopes can now see three of these four asteroids in our skies. Vesta is in Cetus and is best seen around 1:00 AM. Pallas is in Lepus and is best seen around 3:30 AM, as is Ceres, which is in the head of Leo, the Lion. For detailed finder charts visit www.heavens-above.com <http://www.heavens-above.com/>. The positions of the asteroids are not specific to your location, so you can just click on the asteroid's name and skip telling the site your location. Once you click on a name, you'll get finder charts to help you locate the asteroid among the stars.

We return to Standard Time this weekend, so don't forget to set your clocks back one hour – remember we “fall back” - before you go to bed Sunday night. We'll return to Daylight Savings Time on Sunday, March 8, next year. Unfortunately for us stargazers, Daylight Savings Time means we have to wait an extra hour for darkness to fall. During the longest days of summer the skies don't get completely dark until after 10:00 PM.

Dudley Sky Watch for October 29-30, 2008
By Mike Molitor

Tonight the moon is just past new.  For those with a good southwest horizon, its extremely thin crescent may just be visible in evening twilight using optical aid.  The bright planets Venus and Jupiter are also visible in the southwest at dusk and early evening.  Saturn rises in the east before dawn.

- - -
“The Sun is a mass of fiery stone, a little larger than Greece”, so stated Anaxagoras in 434 BC. 

Today we know that the Sun is not a just a little larger than Greece but is in fact about 109 Earth diameters across, or 1.3 million times the volume of Earth.  Also, the mass of the Sun is 330,000 times the mass of the Earth, resulting in a mean density of 1.4 times that of water, or about half the density of typical Earth stone.

The Sun is composed mostly of the gaseous elements Hydrogen, about 73% by mass, and Helium 25%.  At the center of the Sun the gases are compressed by gravity to a density of 10 times that of lead.  It is here in the core that the nuclear fusion reaction takes place that converts Hydrogen to Helium, and in the process releases an enormous amount of energy. The temperature in the core is estimated at around 27 million degrees Fahrenheit, and this energy in the form of radiation must escape from the depths, to the surface of the Sun. 

As the energy spreads outward by absorption and re-emission of radiation, the temperature drops to around 7 million degrees.  Somewhere around three-quarters of the way to the surface, the energy begins to travel not as radiation but as movement of the solar gas itself.  Hotter gas rises toward the surface while cooler gas falls toward the interior.  This convective movement of the gas continues through to the surface of the Sun, with the convection cells becoming progressively finer as the distance from the core increases.  The tops of the convection cells appear as granules, which can be seen from Earth using optical telescopes with special filters.  Though the density has dropped to approximately a million times less than the density of air we breath, it is the tops of these convective cells that we see as the solar surface.

It is estimated that it takes around a million years for the energy released in the solar core to reach the surface of the Sun.  At the solar surface the temperature has dropped to a mere 10,000 degrees Fahrenheit.  So, perhaps we can agree with Anaxagoras that the Sun is at least fiery, even if the mechanism that fuels this great heat is not fiery combustion.

The Sun is a star, not unlike many of the stars that fill the night sky. 
It is the closest star to Earth and the one that we can examine in the most detail. 
 

This is the Skywatch Line for Monday and Tuesday, October 27th and 28th.
by Joe Slomka

The Sun sets at 5:54 PM; night falls at 7:29. Dawn breaks at 5:48 AM and ends with sunrise at 7:24.

As the sky darkens, the bright planets Jupiter and Venus populate the southwestern sky. Venus is brighter and lower in the sky. Venus appears as not quite full, while Jupiter is fully illuminated. These planets are slowly converging and dramatically meet a month from now. Venus sets at nightfall, while Jupiter hangs on for two more hours.

The dim planets Uranus and Neptune are ideally observed after twilight's end. Uranus lies in Aquarius, while Neptune lies above the tail of Capricornus. The asteroid Vesta is also visible in Cetus, the Whale. Vesta was the fourth asteroid to be discovered and was temporarily called a planet. As many more asteroids came to light, they were desisted as planets and given a separate identity. All three objects appear star-like and require detailed charts, which can be found on astronomy websites.

Saturn is quite high by dawn, appearing beneath the rear quarters of Leo, the Lion. The hour before sunrise finds Mercury below and to Saturn's left. These planets present contrasts. In a telescope, Saturn and its ring system are large and beautiful to behold. Mercury appears bright and small, but about three-quarters illuminated.

Binocular users see the bright star Antares four degrees below Venus. The name means "Rival of Ares," the Greek version of the Roman war god Mars. Antares is one of the brightest stars in the northern sky. It is one of only two bright supergiant stars; the other is Betelgeuse. Antares is truly a giant star. Its diameter is 600 million miles; if substituted for the Sun, it would extend beyond Jupiter's orbit. Antares lies about 600 light years away; only Betelgeuse is closer. This star is nearing the end of its life. It is slightly variable, and will, one day, blow itself up as a supernova. In 1970, Antares was the first star, proven to emit radio waves.

Clear Skies
Joe Slomka

This is Dudley Observatory's Skywatch Line for Friday, October 24, through Sunday, October 26, written by Alan French.

The Moon was at last quarter this past Tuesday, and will be new next Tuesday. The Moon will not rise until just before dawn, so the skies over the weekend will be essentially dark and moonless.

On Saturday morning the thin cresent old Moon and Saturn will be a pretty pair above the eastern horizon around 5 AM, with yellowish Saturn to the upper left of the slender Moon. If you look at 5:20 on Sunday morning, you'll find an even slimmer crescent directly below Saturn. To the lower left of the Moon, and five degrees above the horizon, you should see a star. This star is actually the innermost planet, Mercury. (For reference, if you hold a fist at arms length, it spans ten degrees across the knuckles.) You'll need a good view of the eastern horizon free of clouds and haze to spot Mercury at such a low altitude.

If you are up Sunday morning enjoying the sight of Saturn, the crescent Moon, and Mercury, watch for the ISS passing over our area just after 6:00 AM. The ISS will become visible as it moves out of the Earth's shadow at 6:08:37 when 32 degrees above the west-southwestern horizon. If you are looking toward the western sky, the ISS will come out of the Earth's shadow and appear just below and right of Aldebaran, the brightest star in Taurus, the Bull.

The ISS will then move up past Capella, the luminary of Auriga, the Charioteer, and will be highest at 6:09:47 when 67 degrees above the north-northwest horizon. Its path will then take it down past the top of the Big Dipper, and through the constellation Bootes to the northeast horizon at 6:12:44 AM.

Weather permitting, the Albany Area Amateur Astronomers will host public star parties beginning at 8:00 on both Friday and Saturday nights. The star parties are at George Landis Arboretum in Esperance, and are free of charge and open to all. At star parties, amateur astronomers set up telescopes to provide guests with views of a variety of galaxies, star clusters, nebulae, and double stars.

To reach the arboretum, travel west on Route 20 from Duanesburg until you cross the Schoharie Creek entering Esperance. After crossing the bridge, take your first right. There is a large green sign for “George Landis Arboretum” at the turn. Continue to follow the signs for about one-and-a-half miles to the arboretum, where you will see a farmhouse on your right and a parking area on your left. Continue up Lape Road to the top of the steep part of the hill, and then turn right into the Meeting House field.

Star parties are canceled if the skies are mostly cloudy. Call 374-8460 to verify if a star party is being held or for further information.

Skywatch line for Wed. and Thurs., Oct. 22 and 23, 2008:
by Ray Bogucki

Mars is now lost in the Sun's glare but the other four bright planets are visible, although not at the same time. Jupiter, in the south, and Venus, low in the west, continue to dominate the evening sky. Saturn, which rises in the east about 4 a.m., and Mercury, rising two hours later at the beginning of morning twilight, and currently at its greatest elongation west of the Sun, are reserved for early risers. Looking to the northern sky at nightfall, the five bright stars of the constellation Cassiopeia ride high above Polaris, the North Star. The five stars form the familiar "M" in the Autumn and look like a "W" in the Spring, when they are below Polaris. In Greek mythology, Cassiopeia was the wife of King Cepheus of Ethiopia. To appease the angry god Poseidon, they chained their beautiful daughter Andromeda to a rock to be devoured by the sea monster Cetus. The hero Perseus, riding his winged horse Pegasus, rescued and married the princess.

All of these mythological figures are found in the northern circumpolar constellations. In fact, the star in the northeastern corner of the "great square of Pegasus" is assigned to the constellation Andromeda. Starting with this star, Andromeda sweeps to the northeast in a thin, bent "V" shape. Lying close to the western branch of the "V" is a foggy patch of light easily visible to the unaided eye on a clear, dark night. This is the great spiral galaxy in Andromeda, which is notable for several reasons.

Although our own Milky Way galaxy is a giant among galaxies, the Andromeda galaxy is half again as large as the Milky Way, and one of the largest galaxies known. At a distance of 2.4 million light years, it is probably the most distant light source visible to the unaided human eye. When viewed through a telescope if appears larger than the diameter of the full Moon. Photographs show a spiral galaxy almost edge-on with characteristic layers of dust along the galactic plane. It is one of the small local group of galaxies and is approaching our galaxy at a speed of about 22 miles per second. However, we don't need to worry about a collision because long before it reaches us, our own Sun will have expanded into a red giant, wiping out the solar system.

 

This is the Skywatch Line for Monday and Tuesday, October 20th and 21st
by Joe Slomka

. The Sun sets at 6:04 PM; night falls at 7:39. Dawn breaks at 5:40 AM, ending with sunrise at 7:16.

After Sunset two bright planets attract our attention. Jupiter shines due south, while Venus blazes in the southwest. Venus is much brighter than Jupiter. Venus displays an 81 percent crescent, while Jupiter is completely illuminated globe. If using binoculars, compare Venus with nearby Delta Scorpii less than a degree away; the difference between star and planet is obvious.

The Moon is up by midnight within Gemini on Monday night. Tuesday night finds it one degree south of the Beehive Star cluster, also known as M-44. Tuesday night provides a great binocular view.

Pre-dawn observers on Tuesday morning may see meteors streaming from the area of Orion's club. This is the annual Orionid meteor shower. Meteor showers result when Earth's orbit crosses paths with debris from comet's tails. The Orionids come from the most famous comet of them all - Comet Halley, which returns about every 76 years. Due to the bright, already risen Last Quarter Moon, the number of observed meteors should number only about a dozen per hour.

As if to emphasize the relation of meteors to comets, a new comet is visible in our sky. Comet Cardinal, named for its Canadian discoverer, inhabits the area near the North Celestial Pole. Over the next few weeks, Comet Cardinal approaches Polaris. The comet is visible to amateur telescopes. Details are found on astronomy websites.

The hour before sunrise finds Saturn shining through Leo's hind feet. Mercury rises an hour after Saturn and to Saturn's lower left. Mercury is at greatest elongation, or separation, from the Sun. So predawn Wednesday is an ideal time to see this elusive planet.

The Albany Area Amateur Astronomers hold their monthly meeting on Tuesday, October 21, at 7:30 PM at the Schenectady Museum and Planetarium. This month, Dudley Observatory Rising Star Intern Dan Mancuso describes his experiences at the University of Arizona's "Advanced Astronomy Camp 2008." All club events are free and the public is very welcome.

Clear Skies
Joe Slomka

This is Dudley Observatory's Skywatch Line for Friday, October 17, through Sunday, October 19, written by Alan French.

The Moon was full last Tuesday and is headed toward last quarter next Tuesday, so a waning gibbous Moon will grace the weekend skies. The Sun sets around 6:07 PM, and the sky is completely free of the western twilight glow just after 7:40. On Friday, the Moon will rise at 7:43 PM, just after the sky becomes completely dark. There will be an hour of dark, moonless skies on Saturday before the Moon rises at 8:41, and Sunday's 9:50 moonrise will allow stargazers two hours of complete darkness.

Elusive Mercury, approaching magnitude zero, now rises almost an hour and a half before the Sun. Because of its closeness to the Sun, Mercury can never appear high in the dark skies, and the chances to spot it each year are brief. Mercury is now making its best appearance of the year in the morning sky, and the next several mornings offer the best chances to spot the innermost speed demon.

An hour before sunrise, at 6:15 AM, Mercury will be a little over five degrees above the eastern horizon, and 21 degrees from Saturn - almost directly below the ringed planet, but a little to the left or south. If you have a good view to the east, and the skies are clear and free of clouds and haze, Mercury should be visible to the unaided eye. If not, try looking for it with binoculars. Mercury will be highest in the morning sky next Wednesday morning. Look for it six degrees above the eastern horizon at 6:18 AM when it will at magnitude -0.5. Mercury will continue to brighten to magnitude -1 at the end of the month, but will be moving lower in the morning sky and farther into the glare of morning twilight.

The other inner planet, Venus, is now in the evening sky, and shines brightly at magnitude -4 in the southwestern sky as darkness falls. Venus is bright because it is shrouded in highly reflective clouds. Its brightness makes it difficult to observe though a telescope, and the best views are during bright evening twilight. The earlier, the better. If you catch it early, you might be able to see it looks like a small, fat gibbous Moon. Both innermost planets show phases like our Moon.

If you turn a telescope toward Mercury on the morning of October 18 you will find it a fat crescent, like the Moon when it is approaching first quarter. Because of its speedy journey around the Sun, it will be more than half full by the morning of the 22^nd . You'll need unusually steady skies to get a good look at Mercury's phase. We look though a thick layer of the Earth's atmosphere when objects are low in the sky, and this often makes them shimmer and shake and rarely provides clear views. Perhaps you'll get lucky and get a clear view of the elusive planet and its phase.

Skywatch line for Wed. and Thurs., Oct. 15 and 16, 2008:
by Ray Bogucki

   

  Last night (Tuesday), the Moon stood at its Full phase, brightening the night sky for the next few days.  Astronomers who prefer to seek out faint, deep sky objects grumble and put their telescopes aside until we return to dark, Moonless skies. 

 

  About midnight next Monday (Oct. 20), the Orionid Meteor Shower is expected to reach peak activity.  This shower occurs each year as the Earth is pelted by tiny particles deposited in Earth's orbit by the passage of Halley's Comet every 76 years.  The Moon will  then be at Last Quarter phase, rising near midnight.  This is about the same time as the red supergiant star Betelgeuse, in Orion, also rises.  The radiant for the Orionids is close to Betelgeuse and the meteor activity will increase dramatically after the radiant rises.  Although the light from the Quarter Moon is significantly diminished from the light of the Full Moon, it will still be strong enough to wash out the fainter meteors.  Even so, putting the Moon at your back, you should still be able to observe perhaps 15 of the brighter meteors per hour. 

  An incident that occurred last Monday (Oct. 5), reminds us that the Earth occasionally runs into much larger objects than tiny meteor particles.  An observatory in Arizona reported sighting a fast moving asteroid, about the size of an automobile, approaching the Earth.  This is not an uncommon event as objects of this size collide with the Earth typically several times each year.  Most of them fall, unseen, into the oceans or other uninhabited areas of our planet.  Some objects of this size are observed and their projected trajectories typically indicate a near miss.  This observation was different because it was the first observed incoming mini-asteroid, designated as 2008TC3, whose trajectory indicated a definite collision.  Within hours, NASA's Jet Propulsion Lab predicted that 2008TC3 would slam into the Earth's atmosphere at a speed of 8 miles per second, about 10:46 EDT at a point over Sudan in North Africa.  It was expected to reach incandescent heat and explode about 20 miles above the Earth's surface in a bright fireball, releasing energy equivalent to 1,000 tons of TNT.  No significant-sized particles were expected to reach the surface.

 

  In fact, an airburst was detected at the expected time by an infrasound sensor operated by the International Monitoring System, and both visible and infrared flashes were detected by a European weather satellite.  Curiously, although thousands of observers on the ground both in Africa and southern Europe were on the lookout, no confirmed reports of sightings from the ground have come in.  However, on a KLM airliner, flying about 800 miles from ground zero, the crew, having been alerted, reported a bright, distant flash at the expected time.  Living on an active planet can be exciting!