An illustration of WD 1856 b. Courtesy: NASA’s Goddard Space Flight Centre

NASA Missions Spy First Possible ‘Survivor’ Planet

September 18, 2020

An international team of astronomers using Transiting Exoplanet Survey Satellite (TESS) and retired Spitzer Space Telescope of NASA has reported what may be the first intact planet.

The planet has been found closely orbiting a white dwarf, the dense leftover of a Sun-like star, only 40 per cent larger than Earth.

The Jupiter-size object, called WD 1856 b, is about seven times larger than the white dwarf, named WD 1856+534.

It circles this stellar cinder every 34 hours, more than 60 times faster than Mercury orbits our Sun.

"WD 1856 b somehow got very close to its white dwarf and managed to stay in one piece," said Andrew Vanderburg, an assistant professor of astronomy at the University of Wisconsin-Madison.

“The white dwarf creation process destroys nearby planets, and anything that later gets too close is usually torn apart by the star’s immense gravity," Vanderburg added.

"We still have many questions about how WD 1856 b arrived at its current location without meeting one of those fates," he further said.

A paper about the system, led by Vanderburg and including several NASA co-authors, appears in the Sept. 17 issue of Nature and is now available online.

TESS monitors large swaths of the sky, called sectors, for nearly a month at a time.

This long gaze allows the satellite to find exoplanets, or worlds beyond our solar system, by capturing changes in stellar brightness caused when a planet crosses in front of, or transits, its star.

The satellite spotted WD 1856 b about 80 light-years away in the northern constellation Draco.

It orbits a cool, quiet white dwarf that is roughly 11,000 miles (18,000 kilometres) across, maybe up to 10 billion years old and is a distant member of a triple star system.

When a Sun-like star runs out of fuel, it swells up to hundreds to thousands of times its original size, forming a cooler red giant star.

Eventually, it ejects its outer layers of gas, losing up to 80 per cent of its mass.

The remaining hot core becomes a white dwarf. Any nearby objects are typically engulfed and incinerated during this process, which in this system would have included WD 1856 b in its current orbit.

Vanderburg and his colleagues estimate the possible planet must have originated at least 50 times farther away from its present location.

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