Anastasios (Andy) Tzanidakis, a doctoral candidate in astronomy at the University of Washington, recently stumbled upon something intriguing while examining old telescope data from 2020. He found that a star known as Gaia20ehk, located about 11,000 light years away in the constellation Puppis, was behaving unusually. Unlike most stable stars similar to our sun, which shine steadily, Gaia20ehk began flickering erratically.
“The star’s light output was stable, but then it started having these strange dips in brightness,” Tzanidakis explained. “By 2021, it began to show chaotic behavior. Stars like our sun don’t typically do that, so we were curious to find out what was happening.”
The researchers eventually discovered that the odd behavior stemmed not from the star itself but from massive amounts of rock and dust orbiting around it. This debris was blocking some of the light from reaching Earth, and it appeared to have originated from a dramatic event: a planetary collision.
“It’s remarkable that multiple telescopes actually observed this impact in real-time,” Tzanidakis said. “There are only a few recorded planetary collisions, and this one has similarities to the event that formed the Earth and moon. Observing more events like this could provide valuable insights into how our world was formed.”
Planetary collisions are a key feature of how solar systems form. Young stars attract dust, gas, and rocks, leading to frequent collisions between emerging planetary bodies. Some collide and merge, while others are ejected into space. Over millions of years, this process shapes stable planetary systems.
Interestingly, witnessing such events from Earth is rare. For astronomers, the debris must pass in front of the star to block its light, which can produce a dimming effect that often occurs over several years.
“Andy’s work uses a wealth of existing data to reveal phenomena that evolve slowly, sometimes over decades,” said James Davenport, Tzanidakis’s advisor. “This approach opens the door to many new discoveries.”
In their study, Tzanidakis and his team focused on stars that exhibit significant brightness changes. Their earlier research identified a system where a binary star and a dust cloud produced a lengthy eclipse. However, Gaia20ehk posed a unique challenge, initially showing brief brightness dips before transitioning to chaotic patterns.
Davenport suggested analyzing infrared light rather than visible light. What they found was surprising: while the star flickered dimly, its infrared light spiked. This could indicate that the material blocking the star was extremely hot and glowing.
A violent planetary collision could produce such heat, explaining the dim patches of brightness observed earlier. “This might be due to two planets moving closer together and experiencing a series of impacts before a catastrophic collision,” Tzanidakis noted.
There are also hints that this collision resembles the event that created the Earth and moon about 4.5 billion years ago. The debris around Gaia20ehk orbits at a distance similar to that of Earth from the sun, suggesting that, over time, this material could cool and form new celestial bodies. However, determining what will eventually emerge from this debris cloud could take millions of years.
This discovery underscores the need to keep looking for more planetary collisions. The upcoming Simonyi Survey Telescope at the NSF-DOE Vera C. Rubin Observatory is expected to aid significantly in this search. Davenport estimates that the observatory could identify around 100 similar collisions in the next decade.
Understanding these events could reshape our view of how planetary systems evolve and help refine our search for habitable worlds elsewhere in the universe. “How common are events like the one that formed the Earth and moon? That question is crucial for astrobiology,” Davenport stated. “The moon plays a vital role in creating a stable environment for life on Earth. By observing more of these collisions, we may get closer to answering these fundamental questions.”
For more detailed scientific insights, you can check out the research published in The Astrophysical Journal Letters.
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Space Telescopes; Space Exploration; NASA; Galaxies; Stars; Solar Flare; Sun; Astrophysics
