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An Independent Monthly Newsmagazine Serving the Community since 1989

NIGHT SKIES

Moon, by Tim Nadeau

Photograph of the Moon in February, a couple of days before the official full moon.

March 2006 night sky

—CHARLIE CHRISTMANN
March is a great month to go outside and find some of the brightest stars in the night sky. The brightest is Sirius, the Dog Star, located in Canis Major. Sirius can be seen from every inhabited region of the Earth's surface. To find Sirius, look for Orion's belt. Use the belt stars as a pointer and look high in the southwest. The brightest star is Sirius.

Blazing at a visual magnitude of -1.42, it is twice as bright as any other star in our sky. Intrinsically, Sirius is over twenty times brighter than our Sun and over twice as massive. At a distance of 8.7 light years, it is not the closest star system; the Alpha Centauri system holds this position.

A smaller companion star, Sirius B, was discovered in 1862, by Alvan Graham Clark. In 1915, astronomers at the Mount Wilson Observatory determined that Sirius B was a white-dwarf star, the first ever to be discovered. This small, compact object is the remains of a low-to-medium-mass star that has used up its fuel. The core shrinks into a compact ball of hot star-stuff. Over the course of a few hundred billion years, white dwarfs cool down to where they are no longer visible. However, over the universe's lifetime to the present (about 13.7 billion years), even the oldest white dwarfs still radiate temperatures of a few thousand degrees.

Below Sirius in the southern sky is Canopus, residing in the constellation Carina, the Keel. Canopus is a true powerhouse. Its brightness is due to its great luminosity, not its proximity to Earth. At 310 light-years away and more than fourteen thousand times the brightness of our Sun, Canopus is the second-brightest star.

Having run out of its hydrogen fuel, Canopus is a dying star. It is now in the process of converting its core helium into carbon. This process has led to its current size, sixty-five times that of the Sun. If we were to place our solar system around Canopus, the star would almost envelop Mercury.

Canopus will eventually become one of the largest white dwarfs in the galaxy and may just be massive enough to fuse its carbon, turning into a rare neon-oxygen white dwarf. These are rare because most white dwarfs have carbon-oxygen cores. But a massive star like Canopus can begin to burn its carbon into neon and oxygen as the star evolves into a small, dense, and cooler object.

High in the sky above Sirius is a grouping of stars on the edge of our galaxy. Among these stars is Procyon, in Canis Minor, the Little Dog constellation. It is the eighth-brightest star in our sky. Procyon is a yellow-white main-sequence star, twice the size and seven times more luminous than the Sun. It appears so bright because it is relatively close, at 11.4 light-years.

Procyon is orbited by a white-dwarf companion detected visually in 1896 by John M. Schaeberle. At just one-third the size of Earth, its companion, dubbed Procyon B, contains 60 percent of the Sun's mass.

Finally, in the northwest is Capella, in the constellation Auriga, the Charioteer, shining as the sixth-brightest star in our sky. At a distance of forty-two light-years, Capella is one of the sky's most famous double stars. Its two component stars are both yellow class G stars with roughly the same temperature as the Sun. Both stars are much larger and brighter than the Sun, one fifty times more luminous, the other eighty times brighter. Each is about ten times the size of the Sun. These stars are dying giants that have stopped hydrogen fusion in their cores. The two stars, just below the edge of separability in the best telescopes, are only about sixty million miles apart, about two-thirds the distance between Earth and Sun.

So, on a cold winter's evening go outside and let some of the brightest stars in our night sky shine down on you.

THE PLANETS AND THE MOON
• Mercury will be visible just before sunrise in the east. Look for the Moon to be with Mercury on March 27.
• Venus is also low in the east before sunrise. The Moon is beside Venus on March 26.
• Mars can be found in the evening sky, setting about 11:00 p.m. Look for the Moon to stand beside Mars on March 5.
• Jupiter rises in the east about 10:00 p.m. and shines brightly throughout the morning hours. The Moon settles in beside Jupiter on March 19.
• Saturn is almost directly overhead about 8:00 p.m. this month. The Moon nestles next to Saturn on March 10.
• If you are feeling brave and have a good telescope, set it up March 25 through 27. Mercury and Uranus will be very close together low in the eastern sky. Then look for Venus higher in the morning sky. With Venus, you will be able to locate Neptune also very close together.
• The Moon is full on March 14 and new on March 29.


Astronomy club holds open house

The Albuquerque Astronomical Society (TAAS) will host an open house to highlight its programs, outreach services, and member benefits at UNM's Regener Hall on Saturday, March 11, at 7:00 p.m. This event is open to the general public, and admission is free..
Regener Hall is located on UNM's Main Campus, west of Popejoy Hall. For information and a map, visit www.taas.org or call 254-TAAS.


New comet visible before sunrise

—CHARLIE CHRISTMANN
During the next couple of weeks skywatchers will be looking for the newly discovered Comet Pojmanski, which has just swept past the Sun and will soon cruise past Earth on its way back out toward the depths of the outer solar system. At the time of its discovery, the comet was about a hundred times dimmer than the faintest stars that can be seen with the unaided eye. But since its discovery, the comet has been steadily brightening.

Finally, the comet is just becoming visible to the naked eye. It is expected to put on its best showing during the last days of February and the first week of March in the dawn sky. Currently, Comet Pojmanski is shining at around magnitude 5, which is roughly the same brightness as the faintest star in the bowl of the Little Dipper.

The comet is in the constellation of Capricornus, the Sea Goat. Beginning February 27, skywatchers in the Northern Hemisphere can try locating it, very low above the horizon, somewhat south of due east, about ninety minutes before sunrise. You can use Venus as a guide. The comet will be situated roughly seven degrees to the left and slightly below the brilliant planet (the width of your fist held at arm's length is equal to about ten degrees).

Comet Pojmanski will move a little higher above the horizon every morning. While only five degrees above the horizon on February 27, this quickly improves to ten degrees by March 2, sixteen degrees by March 5, and twenty-two degrees (more than two “fists" up from the horizon) by March 9.

In the early morning sky the comet can be readily picked up in binoculars, looking like a small circular patch of light with a bluish-white hue and an almost starlike center. It comet will passing closest to Earth on March 5, when it will be 71.7 million miles away. After March 5, Comet Pojmanski will be receding from both the Sun and Earth and rapidly fading, as it heads back out into space.

 


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