Look!
Up in the sky! It's a bird! It's a plane! No, it's a supernova! Yes, it's
a supernova! Strange visitor from another planet... oops, this is getting
pretty stupid. Anyway, before reading this article, did you have any idea
what a supernova might be? If you want some clues, you'll get some. First
of all, it doesn't live in a planet because it's just too big for one.
Second, it's not a bird or a plane.
A supernova is a giant star in a binary system that suddenly collapses or explodes. It burns up millions of years' worth of hydrogen fuel in a few hours. Its inner parts are forced inward to make it smaller and more compact. During some of its stages of explosion, it also pushes out a shell of gas that gives off a radio emission. This gas might also give off a visible-light spectra, and from this it's possible to use the Doppler effect to get the redshift of the supernova, as well as the velocity by which he shell expands. It bursts into light and slowly dims -- and it may take years to return to its pre-supernova magnitude.
Scientists believe that the slight differences in the time for brightening and dimming happens when the supernova is breaking into a few different groups. For each group, a distinct absolute brightness is reached. After this, it leaves some pretty spectacular remnants such as nebulae, neutron stars, and black holes.
The
Crab nebula, for example, is a remnant of a supernova near Zeta Tauri which
lives around 600 light years away. Neutrinos on the other hand, were detected
at the same time as the supernova SNR 1987A. This led scientists to believe
that around 90% of the energy from a supernova produces neutron stars.
This means that a supernova does pack a lot of energy if it produces this
much heavenly bodies. (Sort of like a little Big Bang.)
They are very rare events, though; only around one supernova can be born in the Milky Way per century. This is so much better than having a lot of them. Can you imagine being near one? It would probably scorch a third if not half of the solar system.
Supernovae have proven to be very useful in our study of the universe;
especially in calculating distances to other galaxies. The brightness change
of a supernova can be used to infer an absolute magnitude which is used
to get the distance of the supernova from Earth. Hubble's constant (Ho=cZ/D)
was derived by measuring the redshift through the spectra of the parent
galaxy of the supernova. They also help us understand the processes by
which matter reacts at very high temperatures and densities which can be
observed from the expanding outer layers developing very hot temperatures
and densities and causing hydrogen and helium to bind into heavier elements
which compose many of the objects around us.
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