Flash: Bầu trời tháng 9/2009
[FLASH]http://hubblesite.org/explore_astronomy/tonights_sky/db/51/movie.swf[/FLASH]
YOUR GUIDE TO CONSTELLATIONS, DEEP SKY OBJECTS,
PLANETS, AND EVENTS
Tonight's Sky ? Highlights of the September sky.
september
constellations
The September sky is for the birds!
| SOUTH (OVERHEAD) | 8:00 PM |
The great constellation Cygnus, the swan, dominates the autumn evening. Cygnus is also known as the Northern Cross. This shape is easy to spot against the Milky Way, which stretches across the September night sky.
Using bright Vega as your guide star, look for the cross just to the east.
Deneb, the swan?s tail, is a supergiant star. It has the luminosity of 160,000 Suns. If Deneb replaced the Sun in the center of our solar system, it would engulf Mercury and Venus.
Alberio, at the head of the great bird, is a showpiece for small telescopes. This spectacular pair of stars features contrasting colors of sapphire and golden topaz.
Aquila, the eagle, was known to the ancient Greeks as the great bird of Zeus.
Altair, the brightest star in Aquila, is only 16 light-years from Earth. Its fast rotation, less than 10 hours, distorts its shape. Altair is the southernmost star in the Summer Triangle, along with Deneb and Vega.
september
deep sky objects
Cygnus and Aquila are found in the overcrowded Milky Way area overhead.
On a clear night, hazy patches of nebulae can be seen by casually panning across the Cygnus area with binoculars.The most prominent is the North America Nebula, an area of gas and dust illuminated by the nearby, brilliant star, Deneb.Cygnus also hosts several clusters of stars. The easiest to find are M29 and M39.
M29, when viewed at low power with a small telescope, resembles a small square. It?s found near the center of the Northern Cross. Best seen with binoculars, M39 is a loosely bound cluster of about 30 stars, just to the north of Deneb.
Use binoculars to look for the Coathanger, located halfway between Altair and Alberio. From our viewpoint, these stars create a familiar pattern.
september
planets
| SOUTH | 10:00 PM |
Bright Jupiter dominates the night. Look for the large, yellowish star toward the south.
| EAST | 5:00 AM |
Reddish Mars rises well before sunrise. But the beacon that shines above the eastern horizon at dawn is the brilliant Venus.
september
events
Summer Solstice
During the summer, the Sun?s path appears high in the sky and the days are long.
On the day of the equinox, the Sun rises exactly in the east and sets exactly in the west, and day and night are equal length.
The autumnal equinox, heralding the beginning of the change in seasons from summer to fall, occurs on September 22nd at 5:22 PM Eastern Daylight Time.
After the equinox, the Sun will appear lower and lower in the sky, and the days will grow shorter.
These changes are due to the tilt of Earth?s axis as it travels around the Sun.
2009 is the International Year of Astronomy.
Celebrate by exploring the night sky from your own backyard.
Nguồn: Hubblesite.org