In this historical study, researchers identified a planetary mass object forming in the disk arround a young star.
An international team of astronomers, including Johan Olofsson, associated researcher from the Millenium Nucleus of Planet Formation, captured the first direct image of a planet in formation. This planet orbits around the young star PDS 70 at about 3 billion kilometers, equivalent to the distance between Uranus and the Sun. The work led by M. Keppler from the Max Planck Institute for Astronomy and was published in the prestigious scientific journal Astronomy & Astrophysics.
It is known that planets are formed in disks around stars —called circumstellar disks—, which at the very beginning should be continuous, without gaps or cavities. But, when a planet is formed inside this continuous environment, it will slowly open a gap in disk and such gaps have been detected in disks around many young stars. But, until now, in most cases astronomers had not observed any of the planets that are thought to be responsible for opening those gaps. However, in this publication the team of astronomers detected a planetary mass object inside the gap around PDS 70, a young star in our galaxy about 368 ly away from us.
“When we detect a point source like this, there is a chance that it is a star closer to us or behind the host star, but it appears aligned with the star that we are observing. To confirm our detection we observed PDS 70 with different filters and, most importantly, at different times over the past years. The latter is crucial, because it allows us to see if that point source is moving together with the central star around the galaxy or not. If it is a projection, they will not move in the same way from our perspective”, says Johan Olofsson, who is also a researcher from the Institute of Physics and Astronomy at Universidad de Valparaíso, and director of the Max Planck Tandem Group (agreement between the Max Plack Institute for Astronomy, in Heidelberg, Germany, and Universidad de Valparaíso).
Scientist explains that to observe with different filters allowed them to study the planet atmosphere —which was published in other study lead by the A. Mueller at Max Plack Institute for Astronomy, who concluded that the color of the planet is very red, suggesting a cloudy and even dusty atmosphere—. Besides, he emphasizes that the object is detected using different instruments: SPHERE (installed at the Very Large Telescope, VLT, from ESO), NaCo (also installed at VLT) and NICI (installed at Gemini Sur Observatory), detecting the same point source with several instruments and ensures that the point source is not an instrumental artifact.
“This study is a milestone paper for the study of planet formation. It is the first indisputable detection of a young planet that has just been formed. There has been other candidates reported in the literature in the past year, but their nature was not 100% sure. But the case of PDS70 is a very robust one, and we will be able to study that object in great details” comments Olofsson.
Future work
Astronomer says that the future plans are to study the system as a whole. For this, the next step is to monitor the movement of PDS 70b, as the planet is called. “We want to continue observing this target and determine the orbit of the point source. We can see if it follows the gap, if it is eccentric or not, and we will be able to study if the size of the gap is compatible with the mass of the planet”, explains Olofsson. He adds that this is a great oportunity to test the models of planet-disk interactions, because this is the first time we see a planet still in its environment, there are many things to be tested.
Another objective is to study the way the planet grows in mass. For that, Olofsson explains, the light emitted by the planet can be decomposed to identify elements that, in a way, are more sensitive than others to the processes that include mass growth.
In addition, scientists want to use ALMA Observatory to investigate whether this planet, in turn, is surrounded by a disk of material or not.
The owners of the image areESO/A. Müller et al. This spectacular image from the SPHERE instrument on ESO’s Very Large Telescope is the first clear image of a planet caught in the very act of formation around the dwarf star PDS 70. The planet stands clearly out, visible as a bright point to the right of the centre of the image, which is blacked out by the coronagraph mask used to block the blinding light of the central star.