Comet Collisions Spotted Around Distant Star

This artist's concept illustrates the preferred model for explaining ALMA observations of Beta Pictoris. At the outer fringes of the system, the gravitational influence of a hypothetical giant planet (bottom left) captures comets into a dense, massive swarm (right) where frequent collisions occur. Image Credit:  NASA's Goddard Space Flight Center/F. Reddy
An artist’s concept of the system around Beta Pictoris. A hypothetical giant planet (bottom left) captures comets into a dense, massive swarm (right) where frequent collisions occur. Credit: NASA’s Goddard Space Flight Center/F. Reddy

Violent comet crashes are occurring around a star easily visible to sky-watchers, astronomers report. The star is one already known to harbor a burgeoning solar system.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) Telescope in northern Chile announced this week that they have found a giant clump of carbon monoxide gas in the dusty disk previously seen surrounding a Southern Hemisphere star called Beta Pictoris.

The new results are published this week in the journal Science.

This unexpected gas cloudwhich according to theory should be rapidly broken down by radiation from the host starappears to be continuously refilled with carbon monoxide. And the best source for this gas seems to be from ongoing collisions between small icy comets embedded in the disk of debris circling Beta Pictoris.

“Unless we are observing Beta Pictoris at a very unusual time, the carbon monoxide must be continuously replenished,” said lead author Bill Dent, an astronomer at the Joint ALMA Office in Santiago, Chile.

“The most abundant source of carbon monoxide in a young solar system is collisions between icy bodies, from comets up to larger planet-size objects.”

Researchers estimate there may be a swarm of comets whirling around Beta Pictoris, with collisions occurring every five minutes or so.

Astronomers also believe this cometary bombardment may eventually bring potentially life-giving water to the young planets in this alien star system, some 63 light-years from Earth. The location of the gas clump itself is not without mystery either.

It appears to be concentrated in a single spot that sits 13 billion kilometers from the star. That is about three times the distance of Neptune’s orbit from our sun.

“This clump is an important clue to what is going on in the outer reaches of this young planetary system,” said co-author Mark Wyatt, an astronomer at the University of Cambridge, U.K.

“Either the gravitational pull of an as-yet-unseen planet similar in mass to Saturn is concentrating the cometary collisions into a small area, or what we are seeing are the remnants of a single catastrophic collision between two icy, Mars-mass planets.”

See for Yourself

While all this action around Beta Pictoris remains visible only at large observatories, backyard sky-watchers in the Southern Hemisphere can easily spot the star.

Skychart showing location of Beta Pictoris in the southwest sky after nightfall in the Southern Hemisphere. Credit: SkySafari by Simulation Curriculum
Skychart showing location of Beta Pictoris in the southwestern sky after nightfall in the Southern Hemisphere. Credit: SkySafari by Simulation Curriculum

Here’s how: Face your southwest horizon after nightfall and look about halfway up the sky to locate the second-brightest star in the entire sky, yellow-colored Canopus.

Visible even from the southernmost United States, this star 309 light-years away is really best seen from locations south of the Equator.

Canopus is a convenient guidepost to finding Beta Pictoris, which is the second-brightest star in the tiny constellation Pictor, the Easel. It lies less than 6 degrees below Canopus, just a little more than the width of your three middle fingers held at arm’s length.

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Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.