Illustration of a giant glowing donut produced by a planetary collision
mark garlick
A star system 1800 light-years away from ours may have been the site of a massive collision in which two giant planets collided and were incinerated, leaving behind a hot, glowing donut. This is the first time we’ve actually witnessed a planetary collision and its aftermath.
In 2021, astronomers discovered a strange phenomenon in which a sun-like star called ASASSN-21qj dimmed by 95 percent.when Matthew Kenworthy Researchers from Leiden University in the Netherlands looked at past observations of the star and found that it had doubled in brightness three years before it faded.
The cause of its brightening and subsequent dimming is that two giant planets collided in an explosive accident, and the resulting doughnut-shaped disk of heated dust and gas replaced the planets and orbited them for several years. Researchers believe it later obscured our view of the star. .
“We looked at a series of possible ideas,” Kenworthy says. “What seems consistent with all the data we have is a collision between two ice giants. This is the first time we’ve seen something like this.”
The two planets are each several tens of times more massive than Earth, comparable to Neptune, and would have orbited the sun at a similar distance to Jupiter. If they collided with each other, they “would have shattered into a completely molten state.” Kenworthy said it left behind a “giant ball of silica vapor” about seven times the width of the Sun.
Up close, Kenworthy said, observers would have seen a “red-hot impact” blowing rocks and debris away from the planet’s solid core.
At the center of this sphere, incandescent debris is thought to have burned, eventually forming a torus-shaped ring that orbited the star at scorching temperatures of about 700 degrees Celsius. This is about half the temperature that would be expected if the two planets were rocky, and the researchers believe that these planets were rich in water vapor and became ice giants like Neptune and Uranus. I am guessing that it is. After thousands of years, the debris could eventually condense to form a new planet surrounded by multiple moons.
It is unknown how the two planets collided. They could have been disturbed in their orbit by a passing star or another planet before colliding with each other, instantly releasing energy equivalent to keeping a small star burning for two years.
“There’s enough evidence that planetary collisions do happen,” he says. Jonathan Marshall The Institute of Astronomy and Astrophysics at Academia Sinica in Taiwan believes that the moon, for example, was formed when a Mars-sized object called Theia collided with Earth. But Marshall previously suggested ASASSN-21qj’s dimming is due to the breakup of a comet within the system, rather than a planetary collision. “We didn’t feel there was enough mass to warrant involvement of more than a small object,” Marshall says.
Andre Isidro Researchers at Rice University in Houston, Texas, say the idea of a giant collision in this system is “not far-fetched” and that “super-Earths and mini-Neptunes are very common near other stars. Therefore, a huge collision between them is inconceivable.” should also be very common. ”
However, as the system ages, such events should become rarer. This tumultuous period in the solar system is thought to have ended about 100 million years after the birth of the Sun, but Kenworthy and his colleagues believe ASASSN-21qj is 300 million years old. If correct, Isidro said, it would indicate that a giant collision could occur later.
Further observations of the system, perhaps using the James Webb Space Telescope, may show whether the idea of a planetary collision is correct. “My prediction is that in five to 10 years, we’ll start seeing extra light reflecting off dust clouds from the system,” Kenworthy said. “If that doesn’t happen, something else is going to happen.”
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