Wreckage at a White Dwarf

In April 2017 I wrote an article for Sky and Telescope about a disintegrating exoplanet,  of which I obtained data using my telescope,  for the science team led by Harvard. Here is an extract of that article. It is the first proven example of a disintegrating world around another star:

“If someone had told me 20 years ago that I, an amateur astronomer, would someday be on my roof watching the destruction of a small planet orbiting a 17th-magnitude star, I would have said they were nuts. Yet I and other amateur astronomers are now doing just that, and more.

“WD1145+017, or ‘WD 1145’ to its friends, is an obscure white dwarf star 570 light-years away in Virgo near the Leo border. It is pulling apart, grinding up, and devouring one or more of its planets as we watch. We are monitoring fastchanging clumps and streams of orbiting wreckage as they cross the star’s face, dimming its light in ways both regular and irregular. Amid the debris is a solid object some 1,000 Exoplanet kilometers in diameter that continues shedding material. We didn’t discover this happening. For that, we can thank the ingenious and determined engineers who put together the K2 mission for the Kepler spacecraft after it lost its precision pointing ability in May 2013 (see box).”

Kepler’s K2 Mission

Kepler detects worlds orbiting faraway stars by the tiny, periodic dimmings that a planet will cause if, by luck, it crosses the face of its star from our viewpoint. But after two of Kepler’s four reaction wheels (gyroscopes) failed, leaving only two working, the spacecraft lost its ability to orient and point steadily. For that, it needs three different force vectors that it can twist itself around in 3-D space.

Kepler’s handlers figured out how to balance the craft against the delicate radiation pressure of sunlight, so that it does not drift too far in its unconstrained third direction. Thus Kepler came back from the dead in November 2013. In its new role it is able to point to star fields along the ecliptic for a new, extended mission dubbed Kepler 2.

This mission continues today. Unavoidable slow drifts mean that Kepler cannot monitor stars’ brightnesses with the same precision as it originally could. But even so, the K2 mission had found 178 new exoplanets as of January — some of them, like WD 1145, very interesting.

Download and read the full article (PDF)