A Baby Planet Is Born

In a rare discovery, astronomers have spotted a world swirling into being around its star.

A baby planet orbiting a star, as seen through ESO’s Very Large Telescope
The newborn planet orbiting its star, PDS 70, as seen through ESO’s Very Large Telescope (ESO / A. Müllet et al.)

In 2003, Donald Pettit, a NASA astronaut, sprinkled some salt into a ziplock bag for an experiment. Pettit was living on the International Space Station, about 200 miles above Earth. The station was just a few years old then, and astronauts were keen to see how stuff reacted in microgravity.

Pettit gave the bag a good shake. When he stopped, the salt crystals were suspended like tiny flakes in a snow globe. Then there was movement. The particles began bumping into each other. They stuck to each other, forming small chunks, which then collided with other chunks. Within seconds, the crystals had coalesced into one big clump. When Pettit shook the bag again, the clump refused to break apart.

With a plastic bag and some salt, Pettit had created a tiny model of planet formation.

The planets in our solar system and beyond all started out this way, as tiny particles in the cloud of dust and gas left behind from the violent birth of their parent stars. As they bumped into each other to form larger and larger chunks, their gravity attracted even more building material. After millions of years, they became massive worlds.

Astronomers are still trying to understand this process. A team of European astronomers recently aimed one of the world’s most powerful ground-based telescopes at a young star and crossed their fingers. If they looked long enough, perhaps they could catch a glimpse of a baby planet swirling into shape out of the cosmic fog.

They got their wish. Behold the yellow-orange blob in the photo at the top of this story. That’s a baby planet.

The image was taken by an instrument on the Very Large Telescope, a very accurately named telescope operated by the European Southern Observatory in the Chilean desert. The instrument is capable of suppressing the light coming from the star, which reveals its surroundings. In the image, the star appears as a black sphere.

The star, known as PDS 70, resides 370 light-years from Earth. Astronomers had suspected it might host a growing planet because they observed a gap in its protoplanetary disk—the cloud of stardust left over from its birth. Such gaps usually indicate the presence of an object big enough to absorb nearby material with its gravity.

The research, led by astronomers from the Max Planck Institute for Astronomy in Germany, was published Monday in the journal Astronomy and Astrophysics.

With the light of the star blocked, the faint light radiating from the planet, named PDS 70b, came into view. When the astronomers studied this light, they found that PDS 70b is a gas planet several times the mass of Jupiter. Despite what the family portrait above suggests, the planet orbits far from its star, and takes about 120 years to complete one trip around. With a surface temperature of 1,200 Kelvin, it’s a fiery world. And it’s probably still growing, the researchers say.

By observing the young inhabitants of other star systems, astronomers can glimpse the ancient history of our own. Although PDS 70b and Jupiter are unfathomable distances apart, they have similar stories. Their birthplaces determined their fate.

Young stars have a habit of gobbling up nearby gas. If PDS 70b and Jupiter had formed close to their respective stars, they would have emerged from what was left behind when the stars ate up gas: rock. They would have turned out like Mars or Earth. But the planets formed farther out, where gas was safe from the sun’s reach. Jupiter became a giant marble of swirling clouds; PDS 70b, the researchers say, is wrapped in clouds, too.

The image of PDS 70b is, for now, one of the best views we have of a young planet in the throes of formation. But you can witness the fundamental mechanics of this cosmic birth for yourself, and you don’t have to go up to the International Space Station with a bag of salt to do it. Just look under your couch and scan for clumps of dust. Like planets, those dust bunnies arose from the little particles swirling around the universe of your home.