Data from a decommissioned NASA space telescope revealed the disaster scene left behind by a cosmic collision.
Debris-cloud-sized observations by NASA’s Spitzer Space Telescope suggest the dust was formed when two dwarf-planet-sized bodies collided a few hundred light-years from us.
“By looking at dusty debris disks around young stars, we can essentially look back in time and see the processes that may have shaped our own solar system,” said lead author Kate Su, a planetary debris risk researcher and research professor at the University of Arizona, said in a March 18 statement from NASA’s Jet Propulsion Laboratory (JPL) in California, which operated Spitzer.
gallery: The infrared universe as seen by NASA’s Spitzer Space Telescope
The new study marks the first successful attempt by astronomers to observe a debris cloud as it passed in front of its parent star, HD 166191. The star’s size and brightness, along with observations of the debris cloud, allowed astronomers to estimate the size of the cloud, along with the size of possible impacting objects.
Spitzer retired in 2020 after about 17 years observing the universe in infrared light. Infrared allows astronomers to see through dense dust clouds that impair our ability to see what’s happening with visual wavelengths.
HD 166191’s neighborhood is littered with debris, partly because the star is relatively young: only 10 million years old compared to the Sun’s 4.5 billion years. Dust left behind by the young star’s formation is now clumping together to create planetesimals — the possible “seeds of future planets,” as JPL called them.
But once gas begins to flow between these small worlds, collision catastrophes can ensue. Spitzer made more than 100 observations of the star between 2015 and 2019, and in 2018 investigators got lucky.
In mid-2018, and as astronomers watched, the HD 166191 system began to brighten, likely a sign of increased debris accumulation. But Spitzer also captured a transit — the cloud of debris that passes between the telescope and the star, making the star appear temporarily dimmer than when you see a cloud passing in front of the Sun.
Ground telescopes had also spotted the transits, and combining this data with the Spitzer data allowed scientists to estimate the size and shape of the dust cloud.
The observations indicate that the cloud was about three times the size of the star. However, the Spitzer Saw’s infrared brightening suggests that only a small portion of the cloud passed in front of the host star. The rest of the cloud, not seen by the telescope, could have been 100 times larger than HD 166191.
And to form such a large cloud, scientists calculated that the colliding objects must have been massive, the size of dwarf planets in our own neighborhood. The team compared the colliding objects to Vesta, the second largest asteroid, which is about 530 kilometers across.
That first collision also caused a cascade of smaller crashes, the scientists believe.
While the cloud quickly began to dissipate and was gone from Spitzer’s view by 2019, the authors said this study could help them test models and theories of how young planets grow.
“By looking at dusty debris disks around young stars, we can essentially look back in time and see the processes that may have shaped our own solar system,” Su said in the statement. “Learning about the outcome of collisions in these systems can also give us a better idea of how often rocky planets form around other stars.”
A study based on the research was published March 10 in the Astrophysical Journal.