New Delhi: Astronomers have observed for the first time a Sun-like star swallowing up a planet in “one big gulp”, finally confirming a fundamental prediction about stars and their planets.
Earth will also face a similar fate 5 billion years from now, according to the study by researchers at MIT in collaboration with Harvard University and Caltech. published In Nature Wednesday.
“Astronomy helps us answer where we are in the universe and where we are going. This discovery has told us where we are going,” study lead author Kishalaya Dey told a press conference. Dey is a postdoctoral fellow at the Massachusetts Institute of Technology (MIT) Kavli Institute for Astrophysics and Space Research.
Stars expand as they evolve—powering luminous mass ejections as they do so—and thus scientists expect them to harbor planetary bodies. But this has never been seen till date.
This aging star, ZTF SLRN-2020, completely swallowed one of its inner planets over a period of about 10 days. The latter was much larger than the Sun’s inner planets – such as Mercury, Venus, or Earth – and had about 10 times the mass of Jupiter, although only about 1/1,000th the size of the star itself. The event occurred 15,000 light-years away in the Aquila constellation, which is near the galactic plane of the Milky Way.
The star suffered an outburst, with bright, infrared emissions that gradually faded over the course of about six months. To better understand the properties of this optical burst and its emission, the researchers ran various models.
While the explosion was similar to those associated with red novae – explosions caused by the merger of two separate stars – it had a much lower luminous intensity. This indicated that it was indeed a planet orbiting a star.
Along with archival images, astronomers used a combination of telescopes to make these observations, including Caltech’s Palomar Observatory, the WM Keck Observatory, and the Zwicky Transient Facility (ZTF) in NASA’s NEOWISE mission.
“Most planets will suffer this fate at the end of a star’s evolution,” said Morgan McLeod, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics and one of the project’s researchers. “Stars have an atmosphere. And then the planets that orbit around them can feel a pulling force from it. This causes the orbit to become tighter, and the star surrounds the planet. These findings could help determine the fate of planets as stars evolve.
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An Accident
Day’s research began three years earlier, when he was observing novae, which result from the sudden appearance of a bright and possibly new star. But this particular star, ZTF SLRN-2020, appeared extremely bright within a couple of weeks. Dee also observed that it had “ballooned” to four times its size, leading researchers to question whether it was just a nova, or something more.
“It seemed that the star had given off a lot of dust, which is why it is shining so brightly. It also ejected a lot of cold gas and at first, we thought it was a stellar merger. In a stellar merger, stars swallow other stars when they run out of fuel. But since it was much smaller than a stellar merger, we realized it was a star engulfing a planet,” said Dee.
Astronomers said that the Sun will also slowly expand, first swallowing Mercury, then Venus, and then Earth, about five billion years from now. But by that time the earth would be unsuitable. “The sun would also increase electricity production, so all the water on Earth would evaporate,” McLeod said.
But the outer planets of the Solar System may not meet such a fate. MacLeod suggested that even if the Sun ran out of fuel and expanded to a few hundred times its current radius, it would still not reach the outer planets.
The researchers note that whether or not a planet will eventually be consumed by its star is dependent on certain conditions, and suggest that future observations of ZTF SLRN-2020 are still needed.
(Editing by Zinnia Ray Chowdhury)
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