An international team of astronomers using NASA’s Hubble Space Telescope has discovered what may be the most distant Type Ia supernova ever found.
Supernova SCP-0401, nicknamed Mingus, was collected by the Hubble Space Telescope in 2004 but could not be positively identified until after the installation of a new camera that serendipitously acquired more data (Space Telescope Science Institute)
The newly discovered Type Ia supernova, labeled SN SCP-0401 and nicknamed Mingus, has a redshift of 1.71 and dates back 10 billion years.
Supernova SCP-0401 is exceptional for its detailed spectrum and precision color measurement, unprecedented in a supernova so distant.
“This is the most distant supernova anyone has ever found for doing dependable cosmology,” said Dr David Rubin of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, who led the study published in the Astrophysical Journal (arXiv.org version).
“The most important unanswered question we have about the nature of dark energy is whether it varies over time – whether it affects the expansion of the universe differently in different eras. With SN SCP-0401, we have the first example of a well-measured supernova sufficiently far away to study the expansion history of the universe from almost 10 billion years ago.”
“Imagine you’re channel surfing and you come across live news coverage of an exploding star – and then you see the dateline that says it’s July 22nd, 9,947,989,219 BCE. By August 9 the supernova is at its brightest and starts to fade, but you get to watch the whole thing – even though, before the news could ever reach your TV, our Solar system had to form, and then our planet, and intelligent life had to evolve on Earth,” said Prof Saul Perlmutter of the Berkeley Lab’s Physics Division and the University of California, Berkeley.
“Live-at-the-scene coverage has special advantages. While the light curves of most supernovae with redshifts above 1.5 are either incomplete or not cosmologically useful, because their colors can’t be accurately measured, our imaginary TV broadcast has enough high-resolution information to allow us to confidently compare this ancient supernova with much more recent astronomical events.”
Most supernovae begin as stars whose cores collapse, but a Type Ia supernova, in the simplest model, begins as a white dwarf star borrowing mass from a companion star; when it reaches critical mass, it erupts in a titanic thermonuclear explosion. While not identical, Type Ia’s are more similar in brightness than any other type of supernova, and their variability can be accurately corrected for comparison.
This makes them excellent ‘standard candles’ for measuring cosmic distances – the dimmer they appear, the farther away they are, and their distance can be confidently measured. At the same time, their redshift is a direct gauge of how much the universe has expanded since the supernova exploded.
Measuring the history of expansion ultimately depends on comparing distance and redshift for enough Type Ia’s over a long expanse of time; this is how accelerating expansion, propelled by dark energy, was independently found by two competing teams and announced in 1998.
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Bibliographic information: D. Rubin et al. 2013. Precision Measurement of The Most Distant Spectroscopically Confirmed Supernova Ia with the Hubble Space Telescope. ApJ, 763, 35; doi: 10.1088/0004-637X/763/1/35
