Lets learn some constellations! =D

WDragon

Sirius



Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek Seirios ("scorcher"), possibly because the star's appearance was associated with summer.[citation needed] The star has the Bayer designation α Canis Majoris (α CMa, or Alpha Canis Majoris). What the naked eye perceives as a single star is actually a binary star system, consisting of a white main sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B.

Sirius appears bright due to both its intrinsic luminosity and its closeness to the Earth. At a distance of 2.6 parsecs(8.6 ly), the Sirius system is one of our near neighbors. Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of 1.42. It is 25 times more luminous than the Sun[8] but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. The system is between 200 and 300 million years old.[8] It was originally composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago.[8]

Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major (English: Big Dog).[14] The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "Dog Days" of summer for the Ancient Greeks, while to the Polynesians it marked winter and was an important star for navigation around the Pacific Ocean.

read more
http://en.wikipedia.org/wiki/Sirius


Draco


Notable features

Eltanin (Gamma Draconis) is the brightest star in Draco, with an apparent visual magnitude of 2.24 magnitude units.

One of the deep-sky objects in Draco is the Cat's Eye Nebula (NGC 6543), a planetary nebula that is said to look like a blue disc. There are several faint galaxies in Draco, one of which is the lenticular galaxy NGC 5866, sometimes considered to be Messier Object 102. Another is the Draco Dwarf Galaxy, one of the least luminous galaxies with an absolute magnitude of -8.6 and a diameter of only about 3,500 light years, discovered by Albert G. Wilson of Lowell Observatory in 1954.

The star Thuban (α Draconis) was the northern pole star around 2700 BC, during the time of the ancient Egyptians. Due to the effects of precession, it will once again be the pole star around the year 21000 AD.
The Draco nebula (a soft X-ray shadow) is outlined by contours and is blue-black in this image by ROSAT of a portion of the constellation Draco. X-ray energies are between 100 eV and 300 eV. Credit: Dr. David Burrows and Jeff Mendenhall of the Penn State Department of Astronomy & Astrophysics.

The Draco nebula (a soft X-ray shadow) is outlined by contours in the image at right and is blue-black. This image was produced by ROSAT of a portion of the constellation Draco.

read more
http://en.wikipedia.org/wiki/Draco_%28constellation%29

马甲.真

too long to read~~~


sofa

WDragon

回复 2# 马甲.真


ur watering here

马甲.真

i just took the sofa~~~~

hoo now i know that Sirius is the brightest star in the night sky~~~en
nice artical!!

WDragon

.....................

晦暗星辰

Sirius？The FL？Oh,God!

WDragon

回复 6# 晦暗星辰


no!!
this is 100% learning!!