At 13,000 light years from our planet and for about 100 days, a dying star increased its size hundreds of times, enough to swallow the nearest planet. This process will be similar to the one experienced by the Sun in its last days… but it will take 5,000 million years to do so.
For most of their lives, Sun-like stars fuse hydrogen into helium in their core. This process allows them to balance the weight of their outer layers. The problem starts when the hydrogen in the core runs out, then the star starts fusing helium into carbon and hydrogen fusion (formerly in the core) now takes place in the outer layers of the star. And it’s a problem because this causes them to expand and turn the star into a red giant. A “mutation” that is bad news for any planet in the inner system: when the star’s surface finally expands to engulf one of its planets, their interaction would trigger a spectacular burst of energy and material. This process would also slow the planet’s orbital speed, causing it to plunge into the star. Simply put: the star grows so large that it eats up the small or nearby planet.
By studying countless stars at different stages of their evolution, astronomers have been able to piece together their life cycles and how they interact with surrounding planetary systems as they age. Now a new study published in Nature confirms that when a Sun-like star nears the end of its life, it expands to between 100 and 1,000 times its original size, eventually engulfing the system’s inner planets. Such events are estimated to occur only a few times a year throughout the Milky Way.
Although previous observations there were already these events, they had never had the opportunity to capture one live. Thanks to the use of the Gemini South telescope (located in Chile) astronomers have observed the first direct evidence of a dying star expanding to engulf one of its planets. Evidence for this event was found in the explosion of a star in the Milky Way about 13,000 light-years from Earth. This event likely heralds the ultimate fate of Mercury, Venus, and Earth when our Sun begins its death throes in about five billion years.
An expulsion equivalent to 33 planets
The event lasted about 100 days and gave astronomers an idea of the mass of the star and that of its submerged planet. The ejected material consisted of about 33 Earth masses of hydrogen and about 0.33 Earth masses of dust. From this analysis, the team estimated that the parent star is between 0.8 and 1.5 times the mass of our Sun and that the engulfed planet was between 1 and 10 times the mass of Jupiter.
Now that the characteristics of these types of events are known, scientists can more accurately search for similar events occurring in other parts of the galaxy. This will be especially important when the Vera C. Rubin Observatory becomes operational in 2025. For example, the observed effects of chemical contamination on the remnant star when viewed elsewhere may indicate that an engulfment has occurred. The interpretation of this event also provides evidence of a missing link in our understanding of the evolution and ultimate fate of planetary systems, including our own.
“Gemini South continues to expand our understanding of the Universe, and these new observations support predictions for the future of our own planet. This discovery is a wonderful example of the feats we can achieve when we combine world-class telescope operations and cutting-edge scientific collaboration. These observations provide a new perspective for finding and studying the billions of stars that have already consumed their planets in the Milky Way,” concludes Ryan Lau, NOIRLab astronomer and study co-author. I think there is something quite remarkable in these results that speaks to the transience of our existence. After the billions of years spanning the lifetime of our Solar System, our own final stages will likely conclude in a final flash lasting only a few months.”
