TESS and Spitzer discover planet closely orbiting a white dwarf star

Shane McGlaun - Sep 17, 2020, 6:21am CDT
TESS and Spitzer discover planet closely orbiting a white dwarf star

NASA has announced that the Transiting Exoplanet Survey Satellite (TESS) and the now-retired Spitzer Space Telescope discovered the first intact planet found closely orbiting a white dwarf star. The white dwarf star is the dense remnant of a Sun-like star that is only 40 percent larger than the Earth. The planet orbiting the star is the size of Jupiter and is called WD 1856 b. It’s about seven times larger than the star it orbits.

The white dwarf itself is known as WD 1856+534, and the planet orbits it every 34 hours. That orbital period is over 60 times faster than Mercury orbits the sun. What’s interesting is that the planet was able to get so close to the white dwarf star without being torn apart. Scientists point out that the creation process of a white dwarf destroys nearby planets, and the star’s immense gravity typically destroys anything that gets too close later.

Researchers say they have many questions about how WT 1856 b arrived at its current location without being destroyed. The white dwarf and the planet are about 80 light-years away in the northern constellation Draco. The white dwarf is about 11,000 miles across and could be as old as 10 billion years. It’s also a distant member of a triple star system.

When the sun-like star ran out of fuel, it would’ve swollen to hundreds of thousands of times its original size and formed a cooler red giant star. Over time, the red giant sheds its outer layers of gas and loses up to 80 percent of its mass. The remaining hot core of the red giant becomes a white dwarf. Nearby objects are typically engulfed and incinerated during the process, and had WD 1856 b been in its current location, it would have been incinerated.

Scientists estimate that the planet would’ve had to form at least 50 times farther away from its present location to have survived. Researchers say that this is the first time they’ve seen a planet that was able to make the journey towards a white dwarf star intact.


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