Last year, astronomers captured the planet PDS 70b with the first ever confirmed direct image of a planet being born. Something of a rare feat.
What took them by surprise during follow-up observations was that a second planet was also being born at the same time - and that they had, in fact, captured images of the phenomenon at the same time as capturing pictures of PDS 70b.
The two planets that were being born and photographed are PDS 70b (the one astronomers found last year) and PDS 70c. The two planets orbit around PDS 70, a star in the constellation Centaurus.
Technologically-speaking, it is an incredible achievement, and it is a wonderful thing to capture.
Images have been captured in the past, but not with direct imagery
Directly photographing a planet is tricky. Even though many wonderful images of proplanetary discs have been shot in the past, none have managed to directly capture the images. The reason is that exoplanets (like PDS 70b and PDS 70c) are usually very far away.
When they are that far away they are typically too faint to see through our optical telescopes, especially if we also take into consideration that the light they may reflect is outshone by the brightness of the stars. It has been generally hard to tell whether or not planets are out there.
"With facilities like ALMA, Hubble, or large ground-based optical telescopes with adaptive optics we see discs with rings and gaps all over. The open question has been, are there planets there?," astronomer Julien Girard of the Space Telescope Science Institute notes.
"In this case, the answer is yes."
Thanks to these newly captured images, scientists have been able to deduce a good amount of information regarding the planets.
A little information about the two planets
PDS 70b, discovered and photographed last year, is around 4 to 17 times the mass of Jupiter. It orbits the star at a distance of about 20.6 au (3.22 billion kilometres, or 2 billion miles). It takes around 120 years for a single orbit.
The planet was discovered using the planet-hunting instrument SPHERE on the European Southern Observatory (ESO)'s Very Large Telescope (VLT).
PDS 70c, more recently discovered, is a little smaller, around 1 to 10 times the mass of Jupiter. It's also farther away - about 34.5 au (5.31 billion kilometres or 3.3 billion miles), and its orbital period is almost exactly twice that of PDS 70b. For every two of 70b's orbits, 70c only goes around once.
PDS 70c was discovered using a different instrument, the VLT's MUSE spectrograph.
"We were very surprised when we found the second planet," said astronomer Sebastiaan Haffert of Leiden Observatory. A surprise shared, and mutually enjoyed.