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Skywatch March 2010 (newest at top)

Albany Clear Sky Clock

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This is Dudley Observatory's Skywatch Line for Thursday, March 11, through Sunday, March 14, written by Alan French.

There are many beautiful sights in the night sky, but few rival the majestic northern lights or aurora borealis. Although a display of aurora is possible on any night, they tend to be more common near the vernal and autumnal equinoxes, so this is a good time to make a habit of checking the northern and northwestern skies for their ghostly glow.

The first hint of an aurora is often a subtle glow of light low in the northwest. Sometimes it is a rather diffuse glow, other times it looks like a curtain of light. If the display becomes more active, the curtain may move higher in the sky and brighten. Often taller rays of light begin to extend upward from the curtain.

A really active display may move even higher in the sky. Overhead we can have coronal displays - essentially looking up into the auroral curtains. On rare occasions the light show can cover the entire sky.

Some displays are subtle and appear a pale white color. A very active display features vivid reds and greens.

Displays may also be static with only very slow changes with time. Sometimes static displays are hard to distinguish from high clouds. Other displays are very active, with bursts of brighter light traveling up from the horizon or across the entire sky. A bright, active display is something you will never forget.

The best way to catch a display is to check the northwestern sky as often as possible. You can get news about possible aurora conditions at www.spaceweather.com. If conditions are favorable, make plans to check a few times during the night. Encourage your friends who keep late hours to keep their eyes open, and to call you if they spot a good display. (If you do, warn your family members about possible late night phone calls!)

This is the Skywatch Line for Monday and Tuesday, March eighth and ninth.
by Joe Slomka

The Sun sets at 5:53 PM with night falling at 7:28. Dawn breaks at 4:44 AM and ends with sunrise at 6:18.

 

At sunset, Venus hovers low in the West. Venus far outshines Sirius, the bright star in the South. Venus creeps higher nightly and improves the observer's view over the month. Venus is almost "full," but as March progresses, it becomes slimmer but larger in the eyepiece.

 

As Venus sets, Saturn rises. If you are lucky and have unobstructed eastern and western horizons, it is possible to see them 180 degrees apart. Saturn joins Mars as night falls. Both remain visible for most of the night. Mars appears as a rusty object between Gemini and Cancer. White Saturn floats within the dim constellation of Virgo. Saturn is beginning its annual appearance, while Mars is drawing to a close. Mars had its opposition in late January. Earth has passed Mars and we are seeing it recede in our rear view mirror. But Mars is still large enough to observe surface details. Saturn's gas giant status precludes surface observation, but its rings and many moons are the highlight for any star party. The hours around midnight are the best times to view both planets.

By 10 PM, a bright orange star glows between Saturn and the North Pole. This is Arcturus, the brightest star of the constellation Bootes. It is variously translated as the "Herdsman" or "Bear Driver." Arcturus is the closest giant star to Earth. Its diameter is 26 times larger than the Sun, but its mass is only four times heavier. Arcturus is an older, bloated, cool star that has probably stopped fusing hydrogen and is burning helium instead. Arcturus is famous for a few reasons. Proper motion is a star's actual movement through space. Sir Edmond Halley, of comet fame, discovered the star's proper motion in 1718. The 1933 Chicago World's Fair used the light from Arcturus to officially open the event. At that time it was estimated to be 40 light-years distant, the time of the last Chicago World's Fair in 1893. We now know Arcturus is slightly closer, about 37 light-years away.

 

Clear Skies
Joe Slomka

This is Dudley Observatory's Skywatch Line for Friday, March 5, through Sunday, March 7, written by Alan French.

The Moon will be at last quarter on Sunday, so the hours before midnight this weekend will be dark and moonless.

The International Space Station will glide across our skies early Saturday evening. Its path will take it above Orion, the Hunter, and through Gemini, the Twins. The ISS will pass very close to Pollux and not far from Mars.

Look for the ISS coming up from the horizon just after 6:09 pm on Saturday night. It will be highest at 6:12 when 64 degrees above the southeastern horizon, and will vanish in the east northeast at 6:15. We see the ISS because it is up in sunlight while we are down in the Earth's shadow, and because it is large and reflects a lot of sunlight it appears brighter than any stars.

Vesta, discovered by German astronomer Heinrich Wilhelm Olbers on March 29, 1807, was the fourth asteroid discovered and is the brightest in the night sky. It can be seen with binoculars and is now fairly easy to find.

If you look toward the southeast around 9 pm you'll see a pattern of stars that looks like a backwards question mark, with a bright star at its bottom. This star pattern outlines the face of Leo, the Lion, and the bright star is Regulus, marking the lion's heart. Starting with Regulus as "one," count up to the third star. Vesta lies about midway between this star and the star that marks the top end of the question mark.

To be sure you have locating Vesta, draw the stars you see through your binoculars for several nights. The star that changes position is Vesta. You can also get a finder chart for Vesta at www.skyandtelescope.com. Look under the "Observing Highlights."

Dudley Skywatch line for Wed. and Thurs., March 3 and 4, 2010:
by Ray Bogucki

At nightfall this week, the spectacular constellation, Orion the Hunter, is still well up in the south-southwestern sky. Orion is one of the best known and most easily identified constellations in the sky. A fairly regular rectangle of bright stars outlines the shoulders and feet of the hunter, while three bright white stars, closely and evenly spaced in a straight line across the center of the rectangle, form his belt. A line of fainter stars hanging from his belt represent his sword.

 

The bright red supergiant star Betelgeuse in the hunter's shoulder, at the northeastern corner of the rectangle, approaches a billion miles in diameter and may be the largest single object visible to the human eye. Diagonally across the rectangle is the brilliant blue-white giant star, Rigel, marking Orion's foot. Even though Rigel is much smaller in diameter and more distant than Betelgeuse, it nevertheless outshines its giant orange neighbor. Indeed, shining almost six thousand times intrinsically brighter than our sun, Rigel is among the most luminous objects visible to the human eye. Giant stars such as Rigel can reach this intense brilliance only by burning their nuclear fuel at prodigious rates. This profligate consumption of their resources dooms them to a very short life. Within only a few tens of thousands of years, Rigel will likely expand in size to become a much cooler red supergiant like its neighbor Betelgeuse. These supergiants often end their short lives in the spectacularly violent explosions that create supernovas. For a few weeks, the exploding star will shine with the light of a billion suns while it generates heavy elements that cannot be made in the normal nuclear fusion occurring in an ordinary star. These heavy elements will eventually mix with huge clouds of interstellar gas and dust in the area. The new stars and planets that form from these clouds will contain these heavy elements.

 

On a dark, clear night you may detect by eye that the center of Orion's sword appears fuzzy. Binoculars confirm a nebulous cloud, while a telescope reveals a large windswept-appearing cloud of gas and dust in which stars are being born. Rather than an Earth-type wind, the cloud is agitated by intense ultraviolet radiation, largely coming from newly formed stars in a tight cluster known as the Trapezium. This radiation causes the gas in the cloud to fluoresce and glow, making the cloud visible even from our distant location of 1500 light-years away. Our own Sun and its planets were formed from a similar cloud some 5 billion years ago. We humans carry atoms in our bodies that were once expelled during a supernova explosion. Thus, we are made partly of star dust!

This is the Skywatch Line for Monday and Tuesday, March first and second.
by Joe Slomka

The Sun sets at 5:45 PM; night falls at 7:19. Dawn breaks at 4:56 AM and ends with sunrise at 6:30.

 

At sunset, Venus glows low in the West and sets about an hour after. Venus climbs slowly in the evening sky all month, while retaining its brilliance. The ecliptic, the path of the Sun and planets, is steep this season and permits long planetary appearances.

 

Mars, also on the ecliptic, also shines brightly in southern skies after sunset. Night reveals it midway between Cancer and Gemini; it ends its westward march at mid-month. Mars slowly dims and shrinks, but is still a worthwhile target for amateur observers.

 

The asteroid Vesta, also a telescopic object, still inhabits Leo's mane. It forms a neat triangle with the stars Algieba and Adhafera. Astronomy magazines and websites provide observing charts.

 

The Moon, one day past Full, and Saturn rise together in Aquarius on Monday night. Saturn is still observable, despite the lunar brilliance. Tuesday evening sees the Moon rise later and lower in Aquarius.

 

The hours after midnight present Mars, Saturn, Vesta and the Moon at their best for the rest of the night.

 

Gemini is an ancient constellation. The constellation was recognized as “Twins” by many cultures. Castor and Pollux, in Greek legends, were the sons of a mortal and Zeus. They crewed the legendary vessel Argo. Ancient sailors prayed to them for a safe voyage. The phrase “By Jiminy” harks back to an ancient oath. The stars are approximately equally bright. In 1803, Herschel discovered Castor to be a binary – two stars orbiting each other. This was the first binary to be discovered. Now astronomers know Castor to be a six member stellar system.

 

Pollux is even more interesting. It is the brightest star to have a planet. The planet is about three times Jupiter’s mass and takes 590 days to orbit Pollux. Pollux is also brighter than Castor. Pollux has left the main sequence and is in the beginning stages of becoming a giant star. Castor and Pollux are about 18 light years apart, with Pollux around 34 light years from Earth.

 

Clear Skies
Joe Slomka