Numerous starless extraterrestrials – astronomers have discovered 170 young solitary planets at once

Homeless Wanderers: Astronomers have discovered 70 to 170 solitary planets in close proximity to young stars – more than ever before. These planets do not orbit the parent stars, but move in solitude in space. According to researchers in the journal Nature Astronomy, the relatively small number of solitary creatures sheds new light on possible mechanisms for the formation of such unstarred asteroids.

Most planets known to date are part of a system: they orbit one or more stars and are made up of a disk of gas and dust orbiting their star. But there is also The one who is lonely – Infinite planets going into space without mother star. There are both of these starless planets Earth-sized rocky planetsn as well Big gas giants, Are also on the border of some brown dwarfs.

The target is human hunting

Astronomers working with Nuria Miret-Roig from the University of Bordeaux have discovered the largest population of unstarred asteroids to date. For their study, they spent 20 years and evaluating observational data from telescopes looking for hidden solitary planets hidden in the nearby galaxy Upper Scorpio. It is about 420 light-years away and contains many of the first young stars a few million years old.

Since starless planets do not reflect light, the research team searched for more than 80,000 images of the weak thermal signatures of still lonely planets, but also the predictable motions of surrounding stars. “We measured the tiny motions, colors, and brightness of tens of thousands of sources over a large area of ​​the sky,” explains Mired-Royk.

Up to 170 starless climbers

The yield was surprisingly large: the team was able to detect 70 to 170 isolated planets in both regions. It is becoming more widespread due to the great uncertainty about the age of the celestial bodies. But since age determines their thermal radiation and brightness, some lighter objects may already be brown dwarfs.

But even though there are only asteroids without 70 stars, this is the largest collection of individuals ever identified. “We don’t know how much to expect, and we & # 39; re glad we found so many more,” says Mired-Royk. Most of these exoplanets are gas giants at least the size of Jupiter. Astronomers could not detect any specific abnormalities in the distribution – the planets were relatively evenly distributed in the field of observation.

Starless planet in every square degree – at least

The number of individual planets allows us to make conclusions about how often such starless wanderers occur. According to astronomers, the ratio of such extraterrestrials is 0.045, compared to stars and brown dwarfs in the explored region of the sky. On average, there were 0.5 to 1 starless planet per square degree in their field of observation.

From this it can be found that there are probably more such isolated planets in space than has been thought for a long time. “There could be billions of these giant free-floating planets orbiting the Milky Way without a host star,” explains Hervவ் Boy, a colleague at Roek. This is consistent with previous estimates Up to 50 billion Such planets may be in our galaxy.

In the path of lonely planets in space.© ESO

How did the separate planets form?

This raises the question of how such loneliness arises in the large number of these heavenly bodies. Some astronomers believe that most of them were once created in planetary systems. Later, gravitational turbulence caused by co-planets or nearby stars ensured that they were expelled from their system. Other researchers believe that isolated ones may have been formed by the local collapse of gas clouds – similar to the way stars form.

“The large sample of our isolated exoplanets offers a great opportunity to test theories about star and planetary formation,” the researchers explain. As they found, current models of gas cloud collapse show a much lower rate of isolation than observed. “You predict a ratio of 0.009 to 0.019 – which is seven times lower than our measurements,” says Mired-Royk.

Astronomers estimate that at least ten percent, and more than 30 percent, of starless planets did not first appear as individual animals. Conversely, they were probably part of a planetary system that was later expelled. “Jupiter’s massive planets are relatively difficult to eject, meaning there may be even smaller solstices in Earth’s mass in our galaxy,” says Mired-Royk. (Natural Astronomy, 2021; doi: 10.1038 / s41550-021-01513-x)

Quelle: European Southern Laboratory (ESO)

December 23, 2021

– Nadja Podbregar