Astronomers discover traces of methyl chloride around infant stars and nearby comet

October 2, 2017
Organohalogen methyl chloride discovered by ALMA around the infant stars in IRAS 16293-2422. These same organic compounds were discovered in the thin atmosphere surrounding 67P/C-G by the Rosetta space probe. The background image of the Rho Ophiuchi cloud complex is from NASA's Wide-field Infrared Explorer (WISE). Credit: B. Saxton (NRAO/AUI/NSF); NASA/JPL-Caltech/UCLA

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected the faint molecular fingerprint of methyl chloride - a chemical commonly produced by industrial and biological processes here on Earth - around an infant star system known as IRAS 16293-2422. Traces of this organic compound were also discovered in the thin atmosphere of comet 67P/Churyumov-Gerasimenko (67P/C-G) by the Rosetta space probe.

Methyl chloride (CH3Cl), also known as Freon-40, is one of a class of molecules known as organohalogens. This new ALMA observation is the first detection ever of a stable organohalogen in interstellar space. The results are published in the journal Nature Astronomy.

The cosmic discovery of this organic compound, however, is disappointing news for astrobiologists, who previously suggested searching for methyl chloride in the atmospheres of alien worlds as a possible indicator of life. The recent ALMA and Rosetta detections raise doubts about that proposal, however. They indicate that methyl chloride forms naturally in interstellar clouds and endures long enough to become part of a forming solar system.

IRAS 16293-2422 is a collection of several infant stars, or protostars, each about the same mass as our Sun. It is located about 400 light-years from Earth and is still surrounded by its natal cocoon of dust and gas.

"Finding organohalogens near these young, Sun-like stars was surprising," said lead author Edith Fayolle, a researcher with the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., at the time of the discovery. "We simply didn't predict its formation and were surprised to find it in such significant concentrations. It's clear now that these molecules form readily in stellar nurseries, providing insights into the chemical evolution of solar systems, including our own."

"ALMA's discovery of organohalogens in the interstellar medium also tells us something about the starting conditions for organic chemistry on planets. Such chemistry is an important step toward the origins of life," said Karin Öberg, an astrochemist at CfA and co-author on the study. "Based on our discovery, organohalogens are likely to be a constituent of the so-called 'primordial soup', both on the young Earth and on newly formed rocky exoplanets."

Approximate location of comet 67P/C-G when the Rosetta space probe discovered traces of methyl chloride -- the same molecule detected by ALMA around the IRAS 16293-2422 star-forming region -- along with other molecules. Credit: B. Saxton (NRAO/AUI/NSF)

ALMA is able to function as an interstellar chemical analyzer by detecting the faint radio signals naturally emitted by molecules in space. Each molecule has a distinctive fingerprint, or series of spikes, in the radio spectrum. For large, organic molecules, however, that signal can be difficult to detect. Larger molecules emit a wider range, though subsequently weaker, series of spikes in the spectrum. It takes incredibly sensitive instruments like ALMA to tease out the telltale signal from molecules like methyl chloride.

The Rosetta spacecraft was able to detect the molecule in the atmosphere of comet 67P/C-G using the onboard instrument known as the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA).

"ROSINA was able to capture some of the around the comet, separate them by mass, and count them with an exquisite precision," said Kathrin Altwegg with the University of Bern, Switzerland, and principal investigator of ROSINA. "This highly sensitive instrument enabled us to detect a host of chemicals around the comet, including the one also discovered by ALMA far from our solar system."

The researchers also note that abundant organohalogens around a young Sun-like analog demonstrates that the present in the involves halogens, which was previously not known.

In addition, both ALMA and Rosetta detected this molecule in similar abundance ratios. Since comets are a remnant of the formation of our solar system and retain a chemical fingerprint of that era, the new observations support the idea that a young solar system can inherit the chemical make-up of its parent star-forming cloud.

"This does, however, raise the question: How much of the comet's organic content is directly inherited from the early stages of star formation?" said Fayolle. "Additional searches for organohalogens around other protostars and comets need to be undertaken to help find the answer."

Explore further: ALMA finds ingredient of life around infant Sun-like stars

More information: Protostellar and cometary detections of organohalogens, Nature Astronomy (2017). DOI: 10.1038/s41550-017-0237-7

Related Stories

ALMA finds ingredient of life around infant Sun-like stars

June 8, 2017

Two teams of astronomers have harnessed the power of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to detect the prebiotic complex organic molecule methyl isocyanate in the multiple star system IRAS 16293-2422. ...

Complex organic molecules discovered in infant star system

April 8, 2015

For the first time, astronomers have detected the presence of complex organic molecules, the building blocks of life, in a protoplanetary disk surrounding a young star, suggesting once again that the conditions that spawned ...

Comet contains glycine, key part of recipe for life

May 27, 2016

An important amino acid called glycine has been detected in a comet for the first time, supporting the theory that these cosmic bodies delivered the ingredients for life on Earth, researchers said Friday.

Recommended for you

NASA telescope studies quirky comet 45P

November 22, 2017

When comet 45P zipped past Earth early in 2017, researchers observing from NASA's Infrared Telescope Facility, or IRTF, in Hawai'i gave the long-time trekker a thorough astronomical checkup. The results help fill in crucial ...

Uncovering the origins of galaxies' halos

November 21, 2017

Using the Subaru Telescope atop Maunakea, researchers have identified 11 dwarf galaxies and two star-containing halos in the outer region of a large spiral galaxy 25 million light-years away from Earth. The findings, published ...

Cassini image mosaic: A farewell to Saturn

November 21, 2017

In a fitting farewell to the planet that had been its home for over 13 years, the Cassini spacecraft took one last, lingering look at Saturn and its splendid rings during the final leg of its journey and snapped a series ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.