In the past 26 years, astronomers have detected thousands of exoplanets orbiting stars other than the Sun, but relatively few interstellar planets have been discovered, roaming the galaxy without being gravitationally attached to any stars. However, a study published this week in the journal Nature Astronomerand accounts for new findings that suggest the existence of at least 70 rogue planets in our galaxy.
It is the largest number of this type of celestial bodies discovered to date. “We didn’t know how many to expect and we are excited to have found so many,” he says in a release Núria Miret-Roig, astronomer at the Laboratoire d’Astrophysique de Bordeaux, the first author of the research. However, finding them has not been an easy task, since the rogue planets, being independent of a star, usually shine very little.
A jump in the number of wandering planets
To find the rebel planets, the researchers analyzed more than 20 years of data collected by the observation instruments of the European Southern Observatory (ESO) and the Gaia satellite of the European Space Agency (ESA). They focused precisely on the constellation Ophiuchus and the stellar association of Scorpius-Centaurus. “We measured the small movements, the colors and the luminosity of tens of millions of sources in a great area of the sky”, details Miret-Roig.
Since the researchers could not calculate the mass of the detected celestial bodies, they had to rely on their brightness to qualify them as potential rogue planets. This is because objects with masses greater than about 13 times the mass of Jupiter cannot be classified as extrasolar planets. Consequently, some of the sources detected would be left out of the list.
The study indicates that the aging of a planet is associated with the loss of heat and, consequently, with the loss of brightness. Taking this into account, the brightest objects detected in an old part of the galaxy are likely to be above 13 jupiter masses, and below if it is a young region. Given the uncertainty in the age of the study region, astronomers note that between 70 and 170 rogue planets have been identified.
Two theories predominate about the origin of the rebellious planets. One is that these objects are formed like stars, through a gravitational collapse of tiny clouds of gas. On the other hand, they assure that they form like planets around a star, however, are thrown out of that system due to gravitational instabilities with the main star or other planets. The truth is that these advances will allow us to better understand the origin of these mysterious cosmic objects.