Image Captures Planet Formation in Striking Detail

11-6-14 Planet formation
ALMA image of the young star HL Tau and its protoplanetary disk. This best image ever of planet formation reveals the multiple rings and gaps that herald the presence of emerging planets as they sweep their orbits clear of dust and gas. ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF)

Planets are being born around a star roughly 450 light-years away from Earth in the constellation Taurus, and scientists have captured the process in striking detail using a new array of telescopes with high-resolution capabilities.

ALMA, or the Atacama Large Millimeter/Submillimeter Array, is a system of antennas that sits 16,000 feet above sea level over the Atacama Desert in the Andes Mountains in Chile. It's also an international collaboration in astronomy, with representatives from more than 20 countries in Europe, North and South America and East Asia. The collaboration is funded in part by the National Science Foundation and is the most expensive project it has ever undertaken, Al Wootten, an ALMA program scientist for North America, tells Newsweek.

The image captured by the ALMA—by turning radio signals, which measure electromagnetic radiation, into digital signals and translating those into a visual representation—"gives an incredible view of the process of planet formation," Tony Beasley, director of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, says in a press release Thursday.

"Such clarity is essential to understand how our own solar system came to be and how planets form throughout the universe," Beasley says.

The NRAO describes the process as follows:

All stars are believed to form within clouds of gas and dust that collapse under gravity. Over time, the surrounding dust particles stick together, growing into sand, pebbles, and larger-size rocks, which eventually settle into a thin protoplanetary disk where asteroids, comets, and planets form.

Once these planetary bodies acquire enough mass, they dramatically reshape the structure of their natal disk, fashioning rings and gaps as the planets sweep their orbits clear of debris and shepherd dust and gas into tighter and more confined zones.

The star of the new image is an actual star called HL Tau, which the NRAO describes as sun-like. The image shows concentric rings around HL Tau, with gaps in between. Though scientists are fairly certain the rings indicate that planets are beginning to form, the structure pictured defies the time line they would have predicted in the process of planetary formation. Because of its relative youth, scientists would have expected to see a smooth disk around the star, one that had not yet formed planetary bodies with enough mass to carve out rings and gaps, Aprajita Verma, an astrophysicist at the University of Oxford, tells BBC News.

"These features are almost certainly the result of young planet-like bodies that are being formed in the disk," ALMA Deputy Director Stuartt Corder says in the press release. "This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image."

Now that ALMA can capture such detail, scientists will be able to learn more about how planets form and could revise their standing hypotheses.

In recent years, "one of the big stories in astronomy has been the number of planetary systems that have been discovered," Wootten tells Newsweek. But "what we know about them is sparse."

The ALMA, which was completed in September and is currently in testing and verification stages, should help answer those questions. It has already produced the most detailed image ever captured of planets in formation, according to the NRAO, providing a window into processes scientists have previously been unable to observe firsthand.

"Most of what we know about planet formation today is based on theory. Images with this level of detail have up to now been relegated to computer simulations or artists' impressions," Tim de Zeeuw, director general of the European Southern Observatory, one of the many organizations involved in the ALMA, told BBC News.

11-6-14 Planet formation 2
Artist’s impression of a protoplanetary disk. Newly formed planets can be seen traveling around the central host star. These same ring-link structures were observed recently by the ALMA around the young star HL Tau. A. Khan/National Science Foundation

The ALMA compares radio signals from 66 high-precision telescopes—or antennas that look like satellite dishes, Wootten says—spaced up to 15 kilometers, or roughly nine miles, apart. Its ability to capture an image like the one of planets forming around HL Tau is "equivalent to a penny as seen from more than 110 kilometers away," the NRAO says.

ALMA Director Pierre Cox says the instrument can collect information no other facility has been able to thus far, including the best optical observatories. For example, because the HL Tau star is surrounded by so much dust and other material, it could not be observed with optical means, Wootten tells Newsweek.

"This is truly one of the most remarkable images ever seen at these wavelengths. The level of detail is so exquisite that it's even more impressive than many optical images," NRAO astronomer Crystal Brogan says in a press release. "The fact that we can see planets being born will help us understand not only how planets form around other stars but also the origin of our own solar system."