Hottest White Dwarf Star in the Galaxy Discovered with Hubble Space Telescope

First Posted: Nov 25, 2015 08:39 AM EST

Scientists may have uncovered the hottest white dwarf in the galaxy. With a temperature that's a staggering 250,000 degrees Celsius, the dying star has already entered its cooling phase.

Relatively low-mass stars, like our sun, get extremely hot towards the end of their lives. The sun's surface temperature has been fairly constant at around 6,000 degrees Celsius since its birth about 4.6 million years ago. Immediately before its source of nuclear energy is exhausted in about 5 billion years, the sun will reach 30 times that temperature at 180,000 degrees before cooling down as a white dwarf.

In this latest study, the researchers evaluated the ultraviolet spectra of a white dwarf with the Hubble Space Telescope. They found that the white dwarf had a new record of a staggering 250,000 degrees-a temperature that can only be reached by a star that's five times more massive than our sun.

The white dwarf is called RX J0439.8-6809, and has already entered its cooling phase. It appears to have reached its maximum temperature of 400,000 degrees about a thousand years ago. Currently, its chemical composition is not understood, though analysis does show that carbon and oxygen are present on its surface.

The white dwarf was first noticed more than 20 years ago as a very bright spot on X-ray images, indicating tremendous heat. Originally, it was thought to be a white dwarf carrying out nuclear fusion on its surface using hydrogen drawn from a companion star. However, closer observations revealed that this wasn't the case.

The findings reveal a bit more about this white dwarf star, which shows researchers that stars can become a lot hotter than expected.

The findings are published in the journal Astronomy & Astrophysics.

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TagsWhite Dwarf, Galaxy, Galaxies, Stars, star, Hubble Telescope, Hubble Space Telescope