Our Sun Was Involved In “Cannibalism on Astronomical Scales”

Young stars consume the equivalent of one Earth every ten days.

Wait… stars eat each other?

It was previously thought that stars born inside a rotating cloud of interstellar gas and dust accumulate their mass steadily.  However, new research is to pointing to this growth being due to a series of violent events called stellar brightening.

The material in the cloud lands on what is known as a circumstellar disk, which forms around the star due to the conservation of angular momentum.  And it is this material that is transported through the disk and onto the star, causing the star to grow in mass.  Precisely how this growth occurs is a major research area in astrophysics.

SEE ALSO: How Jupiter Tried and Failed to Become a Star

For example, the young FU Orionis star in the constellation of Orion showed an increase in brightness by a factor of 250 over a time period of just one year, and has stayed in this high-luminosity state for almost a century.

One explanation for these events was proposed 10 years ago by Eduard Vorobyov, who now works at the Astrophysical Department of the Vienna University in collaboration with Shantanu Basu from the University of Western Ontario, Canada.

According to the theory, stellar brightening may be caused by gravitational instabilities in the circumstellar disks surrounding young stars which leads to the disk being broken into pieces.  These clumps then migrate onto the star.

It is similar to throwing logs into a fireplace — the clumps entering the star release excess energy which causes the young star to brighten by a factor of hundreds to thousands.  During each episode, the star consumes the equivalent of one Earth every ten days.  However, after this, it may take several thousand years before another event happens.

Vorobyov describes the process as “cannibalism on astronomical scales” in a press release.  These clumps could have formed into giant planets such as Jupiter, but instead they were gobbled up by the star.

To test this theory, a group of astronomers led by Huayu Liu from the European Space Observatory in Garching Germany, used high-resolution, adaptive optics observations in polarized light.  The team was able to verify the presence of key features associated with a fragmented disk model, which included large-scale arms and arcs surrounding four young stars that underwent luminous outbursts, including FU Orionis.

“This is a major step towards our understanding of how stars and planets form and evolve,” said Vorobyov.  “If we can prove that most stars undergo such episodes of brightening caused by disk gravitational instability, this would mean that our own Sun might have experienced several such episodes, implying that the giant planets of the Solar system may in fact be lucky survivors of the Sun's tempestuous past.”

I guess all's fair in the fight for survival.