Sunday, August 30, 2009

Constellations, Sagittarius and Scorpius

Sagittarius, the Archer Sagittarius, the archer, whose brightest stars form the shape of a teapot slides low across the southern sky of summer. Sagittarius has drawn his bow, and his arrow is pointing at Antares, the bright red heart of Scorpius, the scorpion. The archer is avenging Orion, who was slain by the scorpion's sting.

The constellation Sagittarius is one of the most interesting regions of the sky. The center of our Milky Way galaxy lies inside Sagittarius, about 26,000 light years away. The constellation also contains several globular clusters tightly packed collections of hundreds of thousands of stars.

Antares is a yellow-orange supergiant star 600 light-years away in the constellation Scorpius.
The star Antares marks the "heart" of Scorpius, the scorpion. It is the brightest star in Scorpius. It's the most difficult to see in the early twilight, but as the sky gets darker, it stands out more. Antares also stands out because of its color. While most of the stars show little or no color, Antares is a vivid orange. That's the result of its surface temperature, which is thousands of degrees cooler than the Sun.

But Antares is a supergiant star, one of the biggest and most massive in our part of the galaxy, so its interior is millions of degrees hotter than the Sun's interior. Like most supergiants, Antares is likely to end its life with a bang, it'll explode as a supernova. That could happen anytime within the next few million years, or as early as tonight.

Scorpius, the Scorpion Three bright stars form the "head" of Scorpius, the celestial scorpion, while its tail curves away below it in the southern sky of summer.

The brightest star in Scorpius is Antares, which is in the middle of the scorpion's curving body. This brilliant red star is one of the behemoths of our stellar neighborhood. If you placed it at the center of our own solar system, it would swallow Mercury, Venus, Earth, and Mars, and almost reach Jupiter.

Tuesday, August 25, 2009

Aquila, the Eagle

There are 88 constellations covering the entire northern and southern sky.
Aquila, the Eagle: Aquila glides on outstretched wings through the glowing band of the Milky Way. Look for it high in the south in late summer.

The brightest star in Aquila is a white star about 16 light-years from Earth called Altair, the Arabic word for eagle. Altair is the southern point of a pattern of three bright stars called the Summer Triangle. Deneb, in the constellation Cygnus, forms the triangle's northeastern point. Vega, in Lyra, the harp, is in the northwest. Altair is nice and bright and easy to find right up to the beginning of winter.

Cygnus, the Swan: The brightest stars of Cygnus form a cross, so the swan is also known as the Northern Cross. Find it soaring high overhead during late summer evenings.

The constellation's brightest star is Deneb, an Arabic word that means "the tail." Deneb the tail of the swan, marks the top of the cross. The swan's outstretched wings form the horizontal bar of the cross, while the head of the swan, a double star called Albireo is the bottom of the cross.

Although it lies about 1,500 light years from Earth, Deneb shines brightly in our night sky because it's a white supergiant, a star that's much larger, hotter, and brighter than the Sun. Deneb is the northeastern point of a star pattern called the Summer Triangle.

If you use binoculars to scan the area between the two bright stars that define the swan's eastern wing, you'll see the remnant of a supernova a faint, incomplete ring of light called the Cygnus Loop.

Lyra, the Harp: It's easy to find Lyra, the harp, by first finding Vega one of the brightest stars in Earth's night sky. Look for Vega high overhead in mid-summer. Lyra looks like a small, lopsided square, with Vega just beside one of the corners of the square.

Sunday, August 16, 2009

Astronomy (August 15th and 16th 2009)

On August 15th and 16th Mars is to the lower left of the Moon at first light on the 15th, and closer to the upper right of the Moon on the 16th. The star Aldebaran, which looks like Mars, is to their upper right.

Aldebaran outshines all the other stars that outline the bull's face. But Aldebaran isn't a member of the Hyades cluster, it just lies in the same direction. It's about 70 light-years away, half as far as the stars of the Hyades. Aldebaran is a red-giant, an old bloated star that's used up most of its nuclear fuel. It's much larger and much brighter than our own middle aged Sun.

On August 16 the crescent Moon and the planet Venus highlight the pre-dawn sky tomorrow. Venus is the dazzling "morning star" just below the Moon. Venus, the dazzling morning or evening star, outshines all the other stars and planets in the night sky. It begins the year in the evening sky, well up in the west as darkness begins to fall. It will disappear from view in late March as it passes between Earth and the Sun. It will return to view as a “morning star” by early April, and remain in the morning sky until December.

Saturday, August 8, 2009

Meteor Shower August 12, 2009

The next meteor shower is the Perseids on August 12, 2009. The shower peaks early afternoon on the 12th, so the morning of the 12th (midnight to dawn) and late evening are the best times to watch from the U.S.

Here are some tips on viewing meteor showers

An increase in the number of meteors at a particular time of year is called a meteor shower. Comets shed the debris that becomes most meteor showers. As comets orbit the Sun, they shed an icy, dusty debris stream along the comet's orbit. If Earth travels through this stream, you will see a meteor shower. Depending on where Earth and the stream meet, meteors appear to fall from a particular place in the sky, maybe within the neighborhood of a constellation.

Meteor showers are named by the constellation from which meteors appear to fall. For instance, The Perseid meteor shower is named because meteors appear to fall from a point in the constellation Perseus.

Shooting stars are name that people have used for many years to describe meteors. Streaks of light across the night sky caused by small bits of interplanetary rock and debris called meteoroids crashing and burning high in Earth's upper atmosphere. Traveling at thousands of miles an hour. Almost all are destroyed, the rare few that survive and hit the ground are known as meteorites.When a meteor appears, it seems to shoot across the sky, and its small size and intense brightness might make you think it is a star.

If you live near a city, drive away from the city lights and toward the constellation from which the meteors will appear to radiate. Find a dark spot where oncoming lights will not ruin your night vision. When you are at your observing spot, position yourself so the horizon appears at the edge of your peripheral vision, with the stars and sky filling your field of view. Meteors will get your attention as they streak by.

If you can see each star of the Little Dipper, your eyes have "dark adapted," and your chosen site is probably dark enough. Under these conditions, you should see plenty of meteors.
What should I pack for meteor watching?

If you can bring red-filtered flashlight for reading star maps and charts without ruining your night vision. Binoculars are not necessary. Its better with just your eyes.