Potential Giant World Circles a Tiny Star

Released Wednesday, September 16, 2020

ID: 13708

- Produced by:
- Chris Smith
- Written by:
- Jeanette Kazmierczak
- Visualizations by:
- Richard Barkus

Watch to learn how a possible giant planet may have survived its tiny star’s chaotic history. Jupiter-size WD 1856 b is nearly seven times larger than the white dwarf it orbits every day and a half. Astronomers discovered it using data from NASA’s Transiting Exoplanet Survey Satellite and now-retired Spitzer Space Telescope.

Credit: NASA/JPL-Caltech/NASA's Goddard Space Flight Center

Music: "Titanium" from Killer Tracks.

Complete transcript available.

An international team of astronomers has reported what may be the first example of an intact planet closely orbiting a white dwarf, a dense leftover of a Sun-like star that’s only 40% bigger than Earth. The detection of the Jupiter-size body was made using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and retired Spitzer Space Telescope.

The object, called WD 1856 b, is about seven times larger than the white dwarf. Based on the object’s size, astronomers think it’s a giant gaseous planet, which future observations and research may confirm. They also estimate it’s no more than 14 times Jupiter’s mass. The potential world circles the white dwarf every 34 hours, over 60 times faster than Mercury orbits our Sun.

The system may have looked very different prior to 6 billion years ago, though. 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% of its mass. The remaining hot core becomes a white dwarf. Any nearby objects are engulfed and incinerated during this process, which in this system would have included WD 1856 b in its current orbit. Astronomers estimate the possible planet must have originated at least 50 times farther away.

The team suggests several scenarios that could have nudged WD 1856 b onto an elliptical path around the white dwarf. This trajectory would have become more circular over time as the star’s gravity stretched the object, creating enormous tides that dissipated its orbital energy.

Illustration of WD 1856 b, a possible world, with its host star in the background.

Credit: NASA/JPL-Caltech/NASA's Goddard Space Flight Center.

Illustration of the potential planet WD 1856 b, its host star, and its orbit.

Credit: NASA/JPL-Caltech/NASA's Goddard Space Flight Center

Illustration of how the WD 1856 system may have evolved.

Credit: NASA/JPL-Caltech/NASA's Goddard Space Flight Center

Illustration of a size comparision between WD 1856 b and its host star.

Credit: NASA/JPL-Caltech/NASA's Goddard Space Flight Center

Illustration of the WD 1856 system, which includes the binary stars G 229-20 A and B, and the possible path a massive object may have taken through the system. Such an encounter could explain how WD 1856 b shifted closer to the white dwarf.

Credit: NASA's Goddard Space Flight Center