Skip to Content
MIT News: 77 Mass Ave

Planetary smashup

Astronomers found compelling evidence for a type of giant collision never directly observed.

December 17, 2021
illustration of collision in space
illustration of collision in space
At least 200,000 years ago in the nearby HD 172555 star system, an Earth-size planet collided with a smaller body so forcefully that part of its atmosphere was stripped away.Mark A Garlick

Scientists believe that young planetary systems experience extreme growing pains as protoplanets collide and fuse—the process thought to have produced the Earth and moon. But such smashups have been difficult to observe in other solar systems.

Now astronomers at MIT, the National University of Ireland Galway, Cambridge University, and elsewhere have discovered evidence of a giant impact around the 23-million-year-old star HD 172555, 95 light-years away. It appears that at least 200,000 years ago, a roughly Earth-size body and a smaller one collided at more than 22,000 miles per hour—a crash so powerful that part of the larger body’s atmosphere was blown away.

The researchers examined data taken by the Atacama Large Millimeter Array in Chile to analyze the dust around HD 172555 and found carbon monoxide circling in large amounts, surprisingly close to the star; a star’s light normally causes this gas to break down at such close range. Their conclusion was that it must be the remnant of an atmosphere-stripping collision. “The only plausible process that could produce carbon monoxide in this system in this context is a giant impact,” says the study’s lead author, Tajana Schneiderman, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences.

“This is the first time we’ve detected this phenomenon of a stripped protoplanetary atmosphere in a giant impact,” says Schneiderman. “Everyone is interested in observing a giant impact because we expect them to be common, but we don’t have evidence in a lot of systems for it. Now we have additional insight into these dynamics.”

Keep Reading

Most Popular

Rendering of Waterfront Toronto project
Rendering of Waterfront Toronto project

Toronto wants to kill the smart city forever

The city wants to get right what Sidewalk Labs got so wrong.

Muhammad bin Salman funds anti-aging research
Muhammad bin Salman funds anti-aging research

Saudi Arabia plans to spend $1 billion a year discovering treatments to slow aging

The oil kingdom fears that its population is aging at an accelerated rate and hopes to test drugs to reverse the problem. First up might be the diabetes drug metformin.

Yann LeCun
Yann LeCun

Yann LeCun has a bold new vision for the future of AI

One of the godfathers of deep learning pulls together old ideas to sketch out a fresh path for AI, but raises as many questions as he answers.

images created by Google Imagen
images created by Google Imagen

The dark secret behind those cute AI-generated animal images

Google Brain has revealed its own image-making AI, called Imagen. But don't expect to see anything that isn't wholesome.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.