Our SStars, Constellations, Galaxies & Blackholes
Our SStars, Constellations, Galaxies & Blackholes
Light from our sun takes about 8 minutes to reach Earth. So that means the light you see from the sun left the sun eight minutes ago!
Our sun is really a middle-sized star. It only seems bigger than other stars because it is the closest star to us. Many other stars are much bigger than the sun. Some are ten times bigger! These are called Giant or Super Giant stars. The smallest stars are about the size of Jupiter.
They can be different colors depending on their temperature. The coolest are 500 degrees and the hottest are 90,000 degrees. The cooler stars look red and the hot look bluish-white.
Astromers today have divied the sky into 88 sections called constellations. There are 14 men and women, 9 birds, 2 insects, 19 land animals, 10 water creatures, 2 centaurs, 1 head of hair, 1 serpent, 1 dragon, 1river and 29 non- living objects. As the earth rotates we see differnt stars at differnt times. In differnt sesons we see differnt contellations. Constellations look flat but they aren't at all. They are just far far away from each other.
The galaxy we live in is called the Milky Way. Within the Milky Way is our Solar System. Galaxies are huge clusters of stars. Ours is estimated to have about two billion stars in it! There are different kinds of galaxies: elliptical, which is an oval shaped galaxy with many old stars; spiral, which is like a very thin pinwheel with long, curved arms of younger stars; & barrel spiral, with spiral arms that spin out from the center. People think the Milky Way is a pinwheel galaxy. An irregular galaxy has no distinct shape.
You can see about 300 stars with the unaided eye in the city. With a small telescope, you can see about 2,000,000 stars!
We know that gravity is a force that attracts objects to one another. But can you imagine what gravity actually looks like? Picture gravity by pretending space is a rubber sheet. Any heavy object resting on the sheet puts a dent in it. The heavier the object, the deeper the dent. If an object is kept heavy but made smaller, the weight is concentrated on a smaller area, and the dent gets deeper. The deeper the dent, the harder it would be for an object to escape if it fell in. What if something is so small and heavy that it forms a dent too deep for anything to escape - ever?
When a large star explodes, it leaves behind an inner core that can become a neutron star, but if the core contains more than three times the mass of our Sun, it can be squeezed into a black hole. Nothing can escape a black hole hole, not even light! Scientists do not know what black holes look like, because they can not be seen, only heard. The only way scientists can identify a black hole is by seeing the matter getting pulled in. If a black hole orbits a star, matter from the star will get pulled into the black hole. Scientists have been using the Hubble Space Telescope to look at the center of a galaxy in the constellation Virgo, 50 million light-years away.
From the book : Mysteries Of Deep Space: Black Holes, Pulsars, and Quasars, page # 15, by Isaac Asimov