Direct images show baby exoplanets stealing gas from their parent star

While discoveries of exoplanets are commonplace, the most obvious method of detection – taking a picture of a planet directly – remains one of the most difficult. And such images almost always reveal a single giant planet orbiting away from its host star.

The researchers were therefore pleasantly surprised to find a second planet orbiting the PDS 70, a young star system about 370 light-years from Earth. It is only the second multi-planetary system observed by direct imaging, and the image shows the star system still in formation, providing valuable evidence on how planetary systems form and evolve.

Attention to the gap

The first planet found in the system is called PDS 70b. It was discovered in 2018. It weighs between 4 and 17 times the mass of Jupiter and orbits about as far from its star as Uranus makes our own sun.

The new planet is called PDS 70c and revolves around the same thing as Neptune in our solar system. It weighs less than its neighbor, between 1 and 10 masses of Jupiter. Astronomers led by Sebastiaan Haffert of the Leiden Observatory used the very large telescope of the Southern European Observatory in Chile to take the images. They published their results Monday in Nature Astronomy.

As the system is so young, it is only 6 million years old, the central star is still surrounded by a disk of gas and dust, like most young stars. But the planets have filled a large space in this disk, which extends from about 1.9 to 3.8 billion kilometers, and surround the star in this space.

These kind of holes in the dust clouds surrounding the young stars have already been used, and exoplanets are often referred to as the source of these holes. When planets gravitate around their planet, their gravity sucks materials nearby and eventually sucks up all the dust and gases nearby, creating an empty space. Finally, a planet will lack material and stop growing. This is also how researchers think that the planets of our own solar system have formed. But in many systems, only the holes are visible, not the planets themselves.

PDS 70 is the direct confirmation of planets and gaps in the same system, giving considerable weight to the astronomers' theories of planet formation. In addition, the two planets revolve around a resonance, the inner planet surrounding its star twice as often as the outer planet. Such resonances can cause planets to migrate over time, and researchers suspect that this type of resonance between Jupiter and Saturn has shaped much of the history of the solar system.