Astronomers have uncovered rare evidence that two planets collided in a distant solar system, producing a large cloud of hot debris. The discovery began when Anastasios (Andy) Tzanidakis, while checking old telescope data from 2020, noticed that Gaia20ehk — a stable main‑sequence star about 11,000 light‑years away near the constellation Pupis — was showing unusual variability.
The brightness record shows three initial dips starting in 2016 and then far more chaotic behaviour around 2021. The team concluded the dips and subsequent disorder were not intrinsic to the star but caused by large amounts of rocks and dust passing in front of it. When, at senior author James Davenport’s suggestion, they examined infrared measurements, the infrared light curve spiked as visible light dimmed. That opposite response indicates the debris was very hot and glowing in the infrared.
Researchers propose a scenario of a series of grazing impacts that produced small dips, followed by a final, major collision that generated much more heat and debris. The resulting dust cloud now orbits Gaia20ehk at roughly one astronomical unit — the same distance from the Sun to Earth — which has led some to compare the event to the impact that created the Earth and moon about four and a half billion years ago. The analysis appears in The Astrophysical Journal Letters and highlights the value of decades of data and searches for slow events.
Looking ahead, the NSF–DOE Vera C. Rubin Observatory will begin its Legacy Survey of Space and Time later this year. Davenport estimates Rubin could find 100 new impacts over the next 10 years, which would help researchers learn how common collisions like this may be. The research was funded by Breakthrough Initiatives. Source: University of Washington.
Difficult words
- variability — change in brightness over time
- debris — small fragments from a destroyed object
- infrared — electromagnetic radiation with longer wavelength
- light curve — graph showing an object's brightness over time
- spike — to rise quickly to a much higher levelspiked
- impact — a collision between two moving objectsimpacts
- astronomical unit — distance equal to Earth–Sun separation
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- If the Vera C. Rubin Observatory finds many similar impacts, how might that change our ideas about how common planetary collisions are? Give reasons.
- Why were decades of telescope data important for detecting this event? What advantages does long-term data provide?
- The article compares this collision to the impact that created the Earth and Moon. What does that comparison help readers understand about the size or significance of the event?
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