A special class of supernova, called a Type Ia supernova, has a remarkably consistent brightness (roughly 5 billion times brighter than the sun). This consistency has been used to estimate the distance of galaxies in the universe. It was studies of these supernovas that allowed scientists to discover that the universe’s expansion is accelerating, a behavior that led to the discovery of dark energy.
But despite many theories, the empirical evidence for each of them was few and far between, until now.
The Astrophysical Journal is about to publish a paper (already available on Arxiv) on the results. The discovery was made using the Large Binocular Telescope and a tool developed at Ohio State University called the Multi-Object Double Spectrograph (MODS).
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Using MODS, Benjamin Shappee and colleagues were able to analyze the frequencies of light being emitted from a recent supernova, and conclude that it was the result of an interaction between two white dwarfs.
A white dwarf is a “dead” star whose fusion reaction has come to an end. With no fusion to push the star outward, these dead stars collapse, become very dense, and only emit light because of energy that is still trapped inside.
The dominant theory is that a white dwarf gradually collects gas from a star that it is in orbit with. It continues absorbing this gas until it reaches critical mass and explodes. What was less clear is whether both of the stars were white dwarfs, or one of them was a traditional star.
The observation supports the theory of two white dwarfs. The spectograph didn’t see a hint of the levels of hydrogen that we would see from a red giant or a star like our own sun.
Only 1 thousandth of one solar mass of material was observed. Current models predict that if this were a star like the sun, it should have been about 15 percent of a solar mass, or half a solar mass if it was a red giant star.
This sets a lower limit of ejected mass ten times smaller than previous observations, essentially confirming the dual white dwarf model.
Note: Edits have been made to include additional information about the measurements taken during the study.
Einstein’s Telescope: The Hunt for Dark Matter and Dark Energy in the Universe