What happens when a star spins really rapidly? Its spherical shape can squash into the shape of a pumpkin. The rapid rotation is thought to be caused by the merging of two binary stars into one.
Astronomers using observations from NASA’s Kepler and Swift missions discovered a batch of 18 of these rapidly spinning stars by detecting X-rays they produce at more than 100 times the peak levels ever seen from the Sun.
These rare stars were found as part of an X-ray survey of the original Kepler field of view, a patch of the sky comprising parts of the constellations Cygnus and Lyra. From May 2009 to May 2013, Kepler measured the brightness of more than 150,000 stars in this region to detect the regular dimming from planets passing in front of their host stars.
These stars rotate every few days, while our own Sun takes an entire month to complete one rotation, and the rapid spinning drives increased levels of stellar activity such as starspots, flares and prominences, which generate X-rays.
The most intense X-ray emission comes from an orange giant named KSw 71. This red giant is more than 10 times larger than our sun, and it rotates fully in just 5.5 days. Watch the video above to learn more.
The illustration above shows two sun-like stars born together in a close binary system, thought to be the first step toward forming a star like KSw 71.
In this next artist’s concept, the more massive star in a close binary system has begun to deplete its core fuel supply. The star has enlarged in response and now physically contacts its companion. These stars will merge together.
In this next illustration, the merging process is nearly complete. Gas ejected from the equatorial region of the combined star forms an excretion disk around it. The disk dissipates over the next 100 million years, leaving behind a very active, rapidly spinning solitary star.
Finally, you get this artist’s concept animation of a star similar to KSw 71, where the excretion disk has fully dissipated.