For the first time ever, astronomers took direct pictures of a pair of planets that were born. PDS 70, the star that gave us the first ever confirmed direct image of the birth of a planet last year, had an additional trick in its protoplanetary discs. Astronomers discovered a second planet in follow-up observations and were able to take pictures of both.
This provides it the added honor of being straight photographed only the second-ever multi-planet system. (The first was HR 8799, with its four exoplanets, one with water in its atmosphere, and the other with a stormy hell-world.)
The two PDS 70 orbiting planets are PDS 70b (the one discovered last year by astronomers) and PDS 70c. The fresh picture demonstrates that in the protoplanetary disk of gas and dust that surrounds the young star. An orange dwarfs only 370 light-years away, they carve out a huge cavity. And we got the first direct pictures of a pair of the planets that were born.
It’s a great technical accomplishment to see and an amazing thing to see. We understand there are tons of exoplanets out there. Thousands were identified, mostly by looking for the very slight dimming that takes place when a planet moves before a star. The very slight wobble triggered by the gravitational tug of the planet.
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We also understand that a swirling disc of dust, rocks, and gas orbits stars when they are freshly created. Planetary accretion occurs when particles in the discs collide and stick together. Gradually grow stronger, collect and clear material from the orbital route, and ultimately form a planet.
In the past, astronomers took some fairly incredible pictures of these protoplanetary discs, with powerful proof of that orbital clearing.
But it’s much difficult to photograph a planet straight. This is because exoplanets are generally far away and therefore too weak to be seen by our optical telescopes. Particularly when the star’s brightness outshines any light they may reflect. And sometimes it doesn’t seem what looks like direct proof.
So, while we can make an educated guess as to whether these discs contain baby planets. We actually saw very few, which means that there may not be.
“With equipment such as ALMA, Hubble, or big ground-based optical telescopes with adaptive optics, we see discs all over with rings and gaps. The open issue was, are there planets?” said astronomer Julien Girard of the Space Telescope Science Institute. “The reply is yes in this situation.”
The pictures acquired enabled researchers to infer quite a lot of planet data.
As we discovered last year, PDS 70b is about 4 to 17 times Jupiter’s mass. Orbiting the star at a distance of about 20.6 au (3.22 billion kilometers or 2 billion miles). Just a bit further than Uranus orbits the Sun. A single orbit requires about 120 years.
The planet was found on the ESO’s Very Large Telescope using the planet-hunting instrument SPHERE. With its starlight-blocking coronagraph and polarization filters that block particular wavelengths. Allowing the telescope to concentrate on the light that can be reflected by a planet as opposed to light emitted by a star.
PDS 70c is somewhat lower, about 1-10 times Jupiter’s mass. It is also farther out -about 34.5 au (5.31 billion kilometers or 3.3 billion miles). Its orbital period is near twice as much as PDS 70b. 70c only runs around once for every two of the 70b orbits.
PDS 70c was found using a separate device. The VLT MUSE spectrograph, with a fresh mode that enables the telescope to house in on a hydrogen signal-a signature of gas accretion. As you might see in a gigantic gas forming planet.
This mode was initially not meant to hunt exoplanets at all, but to study galaxies and star clusters. But the finding points to a prospective fresh manner of trying to locate in protoplanetary discs still forming exoplanets.
“We were very amazed to find the second planet,” said Leiden Observatory astronomer Sebastiaan Haffert. That’s the sort of surprise that we can all appreciate.
The study was released in Nature Astronomy.