Few people would want to know the time and nature of their own demise, but for planet Earth, its fate is sealed. In five billion years it will probably be captured by our own Sun and consumed by a stellar inferno.
Now, for the first time, astronomers have seen what that might look like as another planet in the Milky Way appears to be engulfing its own star.
Experts from Harvard, Caltech and MIT were studying a star 12,000 light years away that was entering its red giant phase at the end of its life and increasing in size.
As the star expanded in an attempt to extend its life as it ran out of fuel it began to attract an orbiting planet towards it, before disappearing.
Over a period of ten days the scientists saw the star 100 times brighter than usual and analysis showed similarities to when two stars merged.
However, the brightness of this event was only a thousandth of the strength of a binary star merger, leading the team to conclude with various computer models that the star had swallowed a large planet, about the size of Jupiter .
After ten days of exceptional brightness the star cooled and astronomers saw the brightness fade over the next six months. Our own Sun, whose heat and gravity allowed life to flourish, will one day do the same for us but Earth’s fiery collapse will occur in about five billion years.
“We are witnessing the future of Earth,” the study’s lead author, Dr. Kishalay De of MIT, said of the findings. “If some other civilization were watching us from 10,000 light years away and the Sun was in conjunction with the Earth, they would see the sun suddenly brighten as it ejects some material, then creates dust around it, before settling they back to what it was.”
100-fold spike in brightness
He also says he was looking at data from the Palomar Observatory in California when he saw the 100-fold spike in brightness which, he says, was “unlike any constellation I had ever seen in my life”.
A year later he studied the same event with infrared data, not visible light. “That infrared data jumped out of my chair,” he says. “The source was extremely bright in the near-infrared.”
Dr. De’s scientific findings are an important advance in understanding planetary dynamics but they are surprising for Mercury, Venus, and probably for Earth as well.
“I think there’s something really remarkable about these results that speak to the impermanence of our lives,” said Ryan Lau, co-author of the study from the NOIRLab.
“After the billions of years that our Solar System will last, our own final stages are likely to be accomplished in a final flash lasting only a few months.”
The study is published in the journal Nature, and Dr Smadar Noaz, an astronomer at UCLA, said in an accompanying article that “gravitational interactions between a star and a planet in close orbit around it can slowly drive the planet into extinction”.
“As a star exhausts its core of hydrogen fuel, it expands and becomes a sub-giant. At this stage, it will begin to swallow its nearby planets – in a few billion years, the Sun will undergo this process.”
Dr Noaz added that more observations of the star engulfing planet seen in this study are needed to understand more about similar events and to find out why they happen.