ALMA photographs debris ring around young star Formalhaut
Disk's chemical composition is strangely similar to that of comets in our solar system.

By Laurel Kornfeld | Jul 28, 2017

Using the Atacama Large Millimeter/submillimeter Array (ALMA), a team of scientists has captured the first ever complete image of a ring of icy dust surrounding the young star Formalhaut.

The complete millimeter-wavelength of the ring reveals it to be a well-defined structure of dust and gas with a composition surprisingly similar to that of comets in our solar system.

Located approximately 25 light years away, Formalhaut has a planet initially discovered in 2008. It is one of only about 20 nearby star systems whose orbiting planets have been directly imaged.

The debris ring is approximately two billion kilometers wide at a distance of about 20 billion kilometers from the star.

At about 440 million years old, the system is just one-tenth as old as our solar system and may be experiencing its own version of the Late Heavy Bombardment that ours underwent about four billion years ago, a period characterized by asteroids and comets left over from the system's formation repeatedly slamming into its planets.

Impacts of exocomets crashing into one another in the outer regions of the Formalhaut system likely created the debris ring, scientists believe.

A previous attempt to image the debris ring with ALMA in 2012, when the telescope was still in the process of being built, revealed just half of the disk but already hinted at chemical similarities with our solar system's comets.

Now, "ALMA has given us this staggeringly clear image of a fully formed debris disk. We can finally see the well-defined shape of the disk, which may tell us a great deal about the underlying planetary system responsible for its highly distinctive appearance," noted Meredith MacGregor of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, and lead author of two papers on the subject scheduled for publication in the Astrophysical Journal.

With the help of computer modeling, the researchers were able to pinpoint the exact location and shape of the disk. Based on its narrow shape, they believe it to be the product of the gravitational influence of planets orbiting the star.

Interestingly, the debris disk contains approximately the same high levels of both carbon monoxide and carbon dioxide found in our own solar system's comets.

Impacts among numerous exocomets could be releasing these gases.

"This chemical kinship may indicate a similarity in comet formation conditions between the outer reaches of this planetary system and our own," noted Luca Matra of the University of Cambridge in the UK and lead author of one of the two papers on the discovery.

 

 

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