Scientists said Wednesday they had observed for the first time a dying star engulfing a planet, offering a preview of Earth’s predicted fate in about five billion years.
But when the Sun eventually engulfs the Earth, it will cause only a “small perturbation” compared to this cosmic explosion, US astronomers said.
Most planets are believed to meet their demise when their host star runs out of energy, turning into a massively expanding red giant, devouring anything unfortunate enough to come in its path.
Astronomers had seen the before and after effects of this process before, but they had never captured a planet in the act of being consumed.
Kishalay De, a postdoc at MIT in the US and lead author of the new study, said the accidental discovery played out like a “detective story.”
“It all started about three years ago when I was looking at survey data from the Zwicky Transient Facility, which takes pictures of the sky every night,” De said at an online news conference.
He came across a star that had suddenly brightened more than 100 times in a 10-day period.
The star is located in the Milky Way galaxy, about 12,000 light-years from Earth, near the constellation Aquila, which resembles an eagle.
– Ice in boiling water –
De was looking for binary star systems, where the larger star bites into its companion, creating incredibly bright explosions called outbursts.
But the data showed that this explosion was surrounded by cold gas, suggesting it wasn’t a binary star system.
And NASA’s NEOWISE infrared space telescope showed that dust had started blowing out of the area months before the explosion.
Even more puzzling was the fact that the explosion produced about 1,000 times less energy than previously observed star mergers.
“You wonder: what is 1,000 less massive than a star?” De said.
The answer was close to home: Jupiter.
The team of researchers from MIT, Harvard and Caltech determined that the engulfed planet was a gas giant with a mass similar to Jupiter, but was so close to its star that it completed one orbit in just one day.
The star, which is quite similar to the Sun, engulfed the planet over a period of about 100 days, starting to nibble at its edges, which expelled dust.
The brilliant outburst came within the last 10 days as the planet was completely destroyed as it crashed into the star’s interior.
Miguel Montarges, an astronomer at the Paris Observatory who was not involved in the research, noted that the star was thousands of degrees hotter than the planet.
“It’s like putting an ice cube in a boiling pot,” she told AFP.
– Observing the fate of the Earth –
Morgan MacLeod, a postdoc at Harvard University and co-author of the study, published in the journal Nature, said that most of the thousands of planets discovered so far outside the Solar System “will eventually suffer this fate.”
And by comparison, the Earth will most likely end not with a bang but with a whimper.
When the Sun expands beyond Mercury, Venus and Earth in about five billion years, it will produce “less dramatic disturbances” because rocky planets are much smaller than gas giants, MacLeod said.
“In fact, they’ll be really minor disruptions to the Sun’s energy output,” he said.
But even before it’s engulfed, Earth will already be “pretty inhospitable,” because the dying sun will have already evaporated all of the planet’s water, MacLeod added.
Ryan Lau, an astronomer and co-author of the study, said the discovery “speaks to the transience of our existence.”
“After the billions of years spanning the life of our Solar System, our final stages will likely conclude in a final flash lasting only a few months,” he said in a statement.
Now that astronomers know what to look for, they hope they will soon be able to observe many more planets being consumed by their stars.
In the Milky Way alone, a planet could be swallowed up once a year, De said.