Detecting planets beyond the Solar System is very difficult, as shown by the fact that the first ones were not detected until 1992. Some of you will think that it was later, in 1995, when the astronomers Michel Mayor and Didier Queloz detected the first extrasolar planet, but that was not the case, what Mayor and Queloz detected was the first planet to orbit “around a solar-type star.” ”. The first detection was made three years earlier by astronomers Aleksander Wolszczan and Dale Frail, although they did not attract much attention because they did not orbit a star like ours, but a pulsar, that is, a neutron star that rotates very quickly and emits a radiation that periodically points at Earth, generating pulses of energy that give it its name. When Wolszczan and Frail observed the pulsar PSR B1257+12 detected anomalies in the pulses and concluded that they were caused by three planets orbiting around them.
These discoveries clearly show that planets not only exist orbiting stars like ours, but that they can accompany other objects and even, as we discussed today in Talking to Scientists, roam the galaxy free, without being gravitationally bound to other larger astronomical objects. massive. The latter are known as “wandering planets” or “wandering planets.”
Detecting an extrasolar planet is difficult because, in most cases, they cannot be seen directly, unless they are large, young, hot objects close to us. Wolszczan and Frail did not see any of the three planets around the pulsar. PSR B1257+12, it was the disturbances that they caused in the pulsar that revealed their presence. Mayor and Queloz did not see the planet that gave them fame either, they only detected its presence from the disturbances it caused in the star 51 Pegasi. And many other astronomical objects of this type are present when, luckily for us, they follow an orbit that crosses in front of the star and produces a decrease in brightness that gives them away.
A rogue planet, however, makes things very difficult for astronomers, because, as it roams freely in space, it does not disturb any star, pulsar, or massive object that might reveal its presence. How then can it be detected? Núria Miret Roig, our guest on Talking to Scientists, answers that question.
Núria is currently researching at the University of Vienna and has been awarded the Prize MERAC 2022 for the best thesis in observational astronomy, awarded by the European Astronomical Society (EAS), for “the discovery of many new floating planets, which shed light on the origin of these exotic nomadic planets,” according to the official announcement.
Núria comments during the interview that there are two ways to detect rogue planets. One consists of making use of gravitational lenses, that is, detecting them when, passing in front of a distant star, being in line with our vision, it bends the rays of light from the star and concentrates them towards us, momentarily increasing their brightness. As the brightness of the star increases more or less and the duration of the phenomenon, data can be extracted from the object that produces the lensing effect and determine if it is an exoplanet.
However, Núria has opted for a completely different approach to the problem. It consists of directly observing the wandering planets. For this she has chosen a very special region of our galaxy, the region known as Upper Scorpio and Rho Ophiuchus, located about 500 light years away from us. It is a very active region for the formation of new stars that is thought to have been created between 1 and 10 million years ago, that is, it is very young and, therefore, so are the bodies that have formed in it. . The observation of this region with the largest telescopes on Earth has revealed the existence of some 3,500 young objects that move in the same direction in space. Of all of them, between 70 and 170 are rogue planets that have masses between 4 and 13 times that of Jupiter. These planets can be directly observed because, being very young, they are hot and emit infrared radiation that can be detected.
Thus, although the result of the investigation only allows the detection of the largest and hottest planets, it is easy to imagine that there must be many other smaller and cooler rogue planets that escape the detection capacity of telescopes.
Núria Miret Roig, a postdoctoral researcher at the Institute of Astrophysics of the University of Vienna and Award Winner, talks about these and other things today. MERAC 2022 for the best thesis in observational astronomy awarded by the European Astronomical Society (EAS).