Best-Ever View of Alien Planet Birth Caught by Giant Radio Telescope

Young Star HL Tau
This ALMA image shows the young star HL Tau and its protoplanetary disk. (Image credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF))

A huge radio telescope in Chile has captured the best-ever image of planets forming around a distant star, researchers say.

The spectacular view of planet birth, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile, shows numerous concentric rings in the disk of dust and gas surrounding HL Tau, a sunlike star found about 450 light-years away from Earth.

"These features are almost certainly the result of young planetlike bodies that are being formed in the disk," ALMA deputy director Stuartt Corder said in a statement. "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." [Amazing ALMA Radio Telescope Images]

The stunning detail and clarity of the new ALMA radio telescope image surprised scientists.

"The first time I saw this image, I thought it was actually probably a simulation. It was just way too good," Tony Beasley, director of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, said in a new video about the planet-formation image. (The NRAO manages ALMA operations on behalf of North American astronomers.)

The new image is the sharpest ever captured by ALMA, researchers said. In fact, it's sharper than most photos taken in visible light by NASA's famous Hubble Space Telescope, they added.

This image compares the size of our own solar system with the young star HL Tau and its protoplanetary disk. Although HL Tau is much smaller than the sun, the star's disk stretches out to nearly three times Neptune's distance from the sun. (Image credit: ALMA (ESO/NAOJ/NRAO))

HL Tau is veiled by dust and gas, making the star tough to observe in visible light. But ALMA was able to pierce this veil, because the telescope is optimized to view the universe in much longer wavelengths, which fall between the radio and infrared portions of the electromagnetic spectrum.

"This is truly one of the most remarkable images ever seen at these wavelengths," said NRAO astronomer Crystal Brogan. "The level of detail is so exquisite that it's even more impressive than many optical images. 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."

This composite image showing the young star HL Tau and its surroundings uses data from the ALMA radio telescope array (enlarged in box at upper right) and NASA's Hubble Space Telescope. (Image credit: ALMA (ESO/NAOJ/NRAO), ESA/Hubble and NASA; Acknowledgement: Judy Schmidt)

ALMA's design calls for 66 individual radio telescopes to work together as a single instrument. These dishes can be moved around the site using giant, 28-wheeled transporters.

ALMA obtained the new planet-formation picture with its antennas spaced up to 9 miles (15 kilometers) apart, researchers said. This "baseline" enables a resolution of 35 milliarcseconds — the equivalent of being able to spot a penny from 68 miles (110 km) away, they added.

"Such a resolution can only be achieved with the long baseline capabilities of ALMA, and provides astronomers with new information that is impossible to collect with any other facility, including the best optical observatories," said ALMA Director Pierre Cox.

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Mike Wall
Senior Space Writer

Michael Wall is a Senior Space Writer with and joined the team in 2010. He primarily covers exoplanets, spaceflight and military space, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.