Saturday, August 9, 2014



With all this talk of a zombie apocalypse, nobody thought to keep an eye to the skies! No, really! NASA’s Hubble Space Telescope recently made an unexpected discoverery. A “Zombie Star”; what is a zombie star?


A zombie star comes out a catastrophic explosion of a large star. Basically as a star ages, the stellar evolution leads it down a path where it ends up with two options. (There are type Ia and Type lax supernovas.) With one option it explodes and flat out obliterates any remnants, but in the other option it doesn’t result in a complete obliteration. In fact a faint supernova leaves behind a surviving part of the dwarf star-essentially, a zombie star.


AND in addition to being lone survivors, the zombie stars are also helping scientists in their bid to understand/study dark energy. (that elusive stuff that makes up ¾’s of the Universe – maybe responsible for the accelerating expansion?) Apparently the scientists use the zombie stars to figure out distance in the Universe as they are all about the same brightness.


To review, a supernova is a stellar explosion that radiates more energy or at least as much as the Sun is expected to over its entire lifetime. The burst of radiation expelled contains most if not the entire star’s material at a speed that is 10% the speed of light. (in other words, fast). This sends a shock wave with an expanding shell of gas and dust.


Supernovae can be triggered in one of two ways. Either by reigniting the nuclear fusion of the degenerate star or by the gravitational collapse of the core of a once massive star; If the first manner then a white dwarf might accumulate enough material through accretion or merger with its companion to raise the core temperature and trigger a runaway nuclear fusion reaction, but in the second case, the core of a massive star undergoes sudden gravitational collapse releasing the gravitational potential energy which in turn creates a supernova explosion.


To date astronomers have identified only a few dozen ‘zombie’ stars which if one considers how vast the universe is, is quite small. Plus they have been looking for decades.


The newly discovered “zombie” star is called (drum roll please) SN 2012Zand can be found in the galaxy NGC 1309. This is of particular interest as there was an object near the location of the supernova-a companion, helium star. Plans are to utilize Hubble in 2015 to observe the area where the supernovae occurred and confirm (or not) the presence of a zombie star and its companion helium star.


Too bad, I was rooting for zombies from outer space-oh well!

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