How do planets meet their ends? For many of the smallest worlds, it maybe as a debris disc strewn around the tiny white dwarf that is all that is left of their stars. The faint infrared glow from nearly forty such discs have been discovered, their rocky origins given away by the chemical composition of the material falling onto the parent white dwarf. Today’s paper adds another disc to the sample, although not without difficulty.
Nearly a year ago, Astrobites reported on an unexpected finding from the Kepler spacecraft: A pair of white dwarfs that were “outbursting”, becoming as much as 20 percent brighter every few days before quieting down again. Today’s paper adds another two outbursting white dwarfs, and begins to explore the reason for this hitherto unobserved behavior.
White dwarfs, the tiny, burnt out cores that stars like the Sun leave behind when they run out of fuel, are a surprisingly ideal place to look for potentially habitable planets. The authors of today’s paper have checked to see if we haven’t already found one, entirely by accident.
On 16th November in 483 CE, astronomers in China recorded the appearance of “a guest star east of Shen, as large as a peck measure, and like a fuzzy star”. The new celestial light shone brightly for just under a month, then faded to nothing. Over 1500 years later, the authors of today’s paper suggests that they may have found the source.
In around five billion years, the hydrogen fuel in the core of the Sun will run out, and our star will begin to die. After swelling up into a red giant, many times bigger than its current size, the Sun will blow away its outer layers to leave a tiny, ultra-dense core, around the size of the Earth. White dwarfs, as these dead, slowly cooling star cores are known, are the ultimate fate for the vast majority of stars in the Universe.
This variable white dwarf pulsates as expected, but it also experiences very bright outbursts. Today’s paper takes us through the discovery and verification of the second pulsating white dwarf with outbursts, and speculates how the pulsations and outbursts may be linked.