Developing planet emerges in a swirl of gas

It appears as a bright spot in gas and dust spiraling around a young star

This is a swirl of gas and dust around a young star, AB Aurigae. The image comes from infrared light — wavelengths the eye can’t see. The star is in the center of the image. It has been blocked out to let the surrounding material shine. The gas and dust around it are forming into a planet. The spiral picture was taken by the Very Large Telescope in Chile.

A. Boccaletti et al/Astronomy & Astrophysics 2020, ESO

Scientists have spotted what appears to be evidence of a planet forming near a young star. And they’ve got pictures.

The star is AB Aurigae. It’s 520 light-years away in the constellation Auriga. (Auriga is Latin for “the chariot driver,” which the constellation is supposed to depict.) At just 4 million years old, AB Aurigae is about one-thousandth the age of our sun. “It’s really a baby,” Emmanuel Di Folco says. He works at the University of Bordeaux in France. As an astrophysicist, he studies the interactions of mass and energy within the cosmos.

AB Aurigae and bright knot
The star AB Aurigae and gas spiraling around it (left). Close-up of the swirling gas and dust (right) shows extra-bright knot (circled in white). That’s where a planet appears to be forming. For scale, blue circle (bottom, right) represents the size of Neptune’s orbit.A. Boccaletti et al/Astronomy & Astrophysics 2020, ESO

Astronomers have seen gaps and large-scale spirals around young stars before. They thought these must have been created by unseen exoplanets — planets outside of our solar system.

Developing planets pull in material from nearby space. In the process, their motions twist the gas around them like swirling skirts. Scientists can hunt for these swirls to pinpoint a planet’s location.

Di Folco and his colleagues used observations from two telescopes in Chile: the Atacama Large Millimeter/submillimeter Array and the Very Large Telescope. These scout for infrared light — a type the human eye can’t see. Images from the telescopes show a spiral disk of gas and dust surrounding AB Aurigae. Near the spiral’s center was a small S-shaped twist.

The star AB Aurigae is about 520 light-years away from Earth. It’s in the constellation Auriga. Zooming in close, scientists could see a spiral shape of dust and gas. An S-shaped region near the spiral’s center is where a new planet appears to be coming together.

That twist “is the precise spot where a new planet must be forming,” says Di Folco. He and his colleagues described their find May 20 in Astronomy & Astrophysics. “It was amazing,” Di Folco says. “It was exactly as we were expecting.”

The apparent planet’s mass is not known. It did make very big waves in the disk of gas. That means it probably has to be a gas giant like Jupiter rather than a rocky planet like Earth. And it might not be alone. The researchers detected a hint of a second planet near the disk’s outer edge.

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

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