Cooking Up A Distant Super-Luminous Supernova.
Out in the vastness of space, no one can hear you scream… or can they? While it might not be an audible last gasp, super-massive stars let go with a tremendous explosion.Then we see the light. While supernovae events are well-known, the super-luminous supernova variety just doesn’t occur that often. These cataclysms are the equivalent of a stellar scream – a scream that’s 10 to 100 times more bright than their distant cousins. Now, two of these rare events have been discovered by a team led by astrophysicist Dr. Jeffrey Cooke of Swinburne University of Technology and they set a record for the most distant so far.
“The light of these supernovae contains detailed information about the infancy of the Universe, at a time when some of the first stars are still condensing out of the hydrogen and helium formed by the Big Bang,” Dr. Cooke said.
Only a few years have elapsed since super-luminous supernovae were first discovered by Palomar Transient Factory research work. As we know, a supenova is spotted by its radiation – a process which can only be the result of two things. It is either the radioactive decay of newly created elements along with the stored heat from the explosion shock of the shell of a supergiant star – or it is the product of the debris encountering the sluggish hydrogen-filled circumstellar field. However, the super-luminous event just doesn’t fit in either category. Not only are they far more bright, but they emit an ultraviolet flux which last far longer than it should. They don’t seem to show any trace of hydrogen and their late-time decay just doesn’t jive with radioactivity.
So what can these super-luminous events be? While their origins are not yet understood, it is possible they are the last, dying gasp of extremely massive stars – ones which are 150 to 250 times more massive than the Sun. Many astronomers surmise the early Universe was filled with these monster stars. These first stars were incredibly large and led short, violent lives. Their nuclear explosions may have been set off by the conversion of photons into electron-positron sets – a process which defies all other types of supernovae.
For this theory to be correct, super-luminous supernovae must also have originated during the earliest epoch of the Universe, when these massive stars were known to exist. This anticipated frequency and unprecedented brightness level intrigued Dr. Cooke and he and his colleagues began their search for the super-luminous supernovae at redshifts which exceed two. This means they were looking back in time more than ten million years ago, less than a quarter of our Universe’s present age.
“Our program uses a novel image-stacking technique and monitors tens of thousands of infant galaxies targeted because they are rapidly forming stars, which increased our chances of detecting the supernovae,” Dr. Cooke said.
So how did they do it? By employing the Keck telescope in Hawaii, the team began combing through data of the early Universe and found what they were looking for – two events at redshifts 2.05 and 3.90. These super-luminous supernova candidates had broken the previous “normal” redshift record of 2.36! Apparently, Swinburne’s investment in the Keck Observatory telescope time was well founded… their research team had scored big. Here before them, was the evidence they were looking for.
“Other than hydrogen and helium, all elements such as carbon, oxygen, iron, and silicon, were manufactured in the cores of stars or during supernova explosions and ejected by the supernovae into space to cool and form the next generation of stars,” explains Dr. Cooke.“The multitude of supernovae over cosmic time enriched the Universe with heavy elements that eventually produced the diverse set of galaxies, stars, and planets we see around us today.”
Are they quark stars? Are they the product of a neutron star which has become incredibly dense? Are they the handiwork of a luminous blue variable star? Is this what happens when matter and anti-matter collide?
We know that normal supernovae happen at a rate of about one per century in a galaxy and this new class may be more than a thousand times more rare. Thanks to these new studies, we may be closer than ever to detecting the first generation of stars.
“Finding the first generation of stars is the current Holy Grail for astronomers. The distances of our supernovae overlap with the distances where we expect to find the first stars.” concludes Cooke.
“Our search technique provides the means to detect and study the deaths of the first generation of stars and understand the chemical enrichment process of the Universe from the beginning.”
Original Story Source: Swinburne University News Release. Reported by Tammy Plotner for “Dave Reneke’s World of Space and Astronomy News”.
- Farthest star explosions in universe found (msnbc.msn.com)