A star is actually a giant ball of gas. Made of mostly hydrogen, they run like a nuclear fusion generator making heat and light energy. They vary in size from tiny neutron stars that are just a few miles wide to red super giants that are millions of miles wide. Stars can live for billions of years. The larger the star, the shorter its lifespan. When a star dies, it is because it runs out of hydrogen. It cools and expands into a red giant, then collapses into a white dwarf, and finally becomes a dead black dwarf. You can tell when you are seeing a star in a photograph because stars seem to have spikes of light shooting out from their center. This is really just how a relic of how the telescope captures the bright starlight.
Our sun is really just a star. It is 864,900 miles wide (1,392,000 km wide). That makes it 330,000 times bigger than the earth. It is 11,000° F (6,000°C) on the surface. Its spinning force acts like a big magnet. It rotates unevenly creating magnetic fields.
The outer most layer of the sun is called the corona. It is 620,000 miles (1,000,000 km) thick. The 2nd layer of the sun is the chromosphere. It is from here that jets of gas explode off the surface of the sun. The actual physical surface of the sun is the 3rd layer, the photosphere. It is made up of granules of gas bubbles boiling on the sun's surface.
Sometimes sunspots appear on its surface. They are areas of cooler, darker gas. How many sunspots we see varies in an 11-year sunspot cycle.
Loops of the sun's magnetic field sometimes burst into space. They are called prominences.
Gas particles (plasma) escape from the sun’s surface and fly through space gaining speed as they go. This is called solar wind. When it reaches Earth, we are protected from it by our planet's magnetic field. The solar particles that do make it through to reach the earth's atmosphere cause something called auroras, which we can see in the night sky. They can also cause radio and electrical problems on Earth.
The Earth is 93 million miles from the sun.
Omega Centauri has a center dense with stars. Scientists call this a globular star cluster and believe it contains several million stars. Most are yellow-white dwarf stars like our Sun. The stars here are very old. Some date back 12 billion years! Omega Centauri is the biggest and brightest globular star cluster in the Milky Way and is about 17,000 light-years from Earth. You can see it with the naked eye on a dark night as a small cloud in the southern sky.
A supernova is known as the bright flash caused by the exploding death of a large star. When a large star finally burns up all its hydrogen, it collapses and explodes in a powerful, bright burst. It releases a burst of energy called neutrinos that we can detect here on earth.
There are actually 2 types of supernovas. One is the explosion after the core collapse of a massive star decribed above. The other is the thermonuclear explosion of a growing white dwarf star.
In 1604 Johannes Kepler, a famous astronomer, watched a bright new star that had suddenly appeared in the night sky and stayed bright for almost a full year before fading away. This was the first recorded sighting of a supernova and is pictured in the Hubble photograph above.
Only six supernovas have been observed in our Milky Way in the last 1000 years.
A pulsar is a rotating neutron star that gives off radio waves out from its axis in a repeating pattern. When the axis rotates away from earth, it looks to us like the light is gone, so we see the pulsar as flashing on and off.
Betelgeuse is a red super giant, it is the largest star in the Milky Way. It is 1000 times larger than our sun.
Nebula are huge (a light year wide or more), thick clouds of dust and gas where stars are born or die. Stars form when hydrogen, helium, carbon and silicon are pulled together by gravity into hot clumps.
A nebula called Orion was found by the Hubble Telescope. Scientists have even named some of its forming stars. A star a little left of the center up high in the nebula has a stream of gas flowing around it is called LL Ori. The bright star in the lower left of the nebula is called LP Ori.
The Cat's Eye Nebula is a planetary nebula that forms when a dying star slowly gives off its outer gas layers. Scientists think the star released its gases in pulses every 1,500-years. These pulses of gas made huge dust shells surrounding the star. These dust shells made layers of rings like an onion around the dying star. In this view of the Cat's Eye Nebula taken by the Hubble Telescope, you can see the rings, like an onion cut in half.
The Boomerang Nebula is 5,000 light-years from Earth. It has a cloud of dust and gas that are being spit out into space from a central star. Scientists call this bipolar outflow. They believe that over the last 1,500 years, almost one and a half times the mass of our Sun has been lost by the central star in this outflow. Bipolar outflows are seen from very young stars called protostars, that are still forming and from old stars near the ends of their lives that have become red giants. The Boomerang nebula is believed to be one of those old red giants.
