Free
When a star like our Sun burns out, it doesn’t fade quietly. Instead, it has a colorful “last hurrah.” It puffs off glowing clouds of gas. Those are called a planetary nebula.
Driven by the spinning and wobbling star, the gases create shapes that look like a carnival spin-art game. Stars ten times bigger than our Sun go out with a bang. The star’s nuclear furnace suddenly shuts down, and it collapses. The collapse is so violent that the star explodes with energy equal to blowing up a hundred thousand trillion trillion of the biggest nuclear bombs at once! This is called a supernova.
◀ Star Corpses
When massive stars explode, they leave remnants that are crushed by gravity. One remnant is a black hole. That’s an object with such strong gravity, no light can escape from it. Another remnant is a neutron star. Its density is 100,000 times greater than steel. We can’t directly see black holes and neutron stars. However, the hot gas around them glows in the X-ray light of a telescope camera. They appear as bright points in the Antennae Galaxies (left). These objects will keep radiating energy long after the last star in the universe has burned out, about 10 trillion years from now.
▲ Ant Nebula
This planetary nebula is so nicknamed because it resembles the head and body of an ant. Why is the pattern symmetrical? One cause may be the gravitational pull of a closely orbiting companion star. Another may be the spinning action of the dying star itself. Astronomers observe dying Sun-like stars such as this one. It is helping them to discover what our Sun’s fate will be.
◀ Supernova Ring
On February 23, 1987, a supernova appeared in the southern sky. It was so bright that it could be seen without a telescope. The Hubble Space Telescope’s sharp eye caught an eerie glowing ring of gas around the explosion. The ring began to brighten again in 2002 as a shockwave from the explosion finally smashed into the ring. The shockwave caused the gases in the ring to light up.
▲ Helix Nebula
At first, this nebula looks like a ring. It is really a trillion-mile-long tunnel made up of material that came from the central star before it became a white dwarf. The white dot at the center is the hot white dwarf. Its ultraviolet light makes the gases in the helix (spiral) glow.
