Scientists find “largest cluster” of almost 100 free-floating planets in a single star-forming region

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Rogue planets have baffled astronomers for ages. In contrast to normal planets, which revolve around stars, these free-floating planets (FFPs) are ejected from the star systems in order to move independently in the galaxy. In the latest discovery, astronomers found the largest cluster of rogue planets in a single star-forming region. With an approximate discovery of 100 FFPs, the new sample is expected to double the existing sample of known rogue planets. No more than a decade ago, NASA’s Kepler Space Telescope had discovered a free-floating planetary object and sparked speculation about planetary anomalies.

The latest study uses data from 20 years of observation through multiple ground-based and space telescopes, combined with over 80,000 wide-field images. The scientists used microlens and direct imaging techniques along with the results of planet-planet scattering simulations.

Telescopes used for the study included the European Southern Observatory (ESO), the Visible and Infrared Survey Telescope for Astronomy (VISTA), the VLT Survey Telescope (VST), and the MPG / ESO 2.2-meter telescope in Chile.

The study was published in the journal Nature Astronomy on December 22nd.

Sean N. Raymond, an author on this study, added more details about the discovery in a tweet thread. In saying that 100 free-floating planets have been found in “a single star-forming region,” added Raymond, “This roughly doubles the total number of known rogue planets.”

Our new paper has just been published in @NatureAstronomy (@nmiretroig, Bouy et al.)!

Punchline: We found ~ 100 free-floating planets in a single star-forming region! This roughly doubles the entire sample of known rogue planets.

A threadhttps: //t.co/CW7WgCNvda

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– Sean Raymond (@sraymond_astro) December 22, 2021

The cluster was located within the constellations Scorpio and Ophiuchus. Brown dwarfs were also part of the discovery. The study was part of the Cosmic DANCE project.

@nmiretroig and Herve Bouy made the count of the Upper Scorpio: all stars, brown dwarfs and rogue planets (> 4 Jupiter masses)

They analyzed> 80,000 images of Upper Sco from the last 20 years (> 100 TB) the Cosmic-DANCE project https://t.co/vafGHjD1pt

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– Sean Raymond (@sraymond_astro) December 22, 2021

The planetary objects have been found to measure between four and 13 masses of Jupiter. Scientists could only estimate the number of FFPs since “their true masses depend on the age of the association, which is not precisely established”. The study assumes that the planets have been connected for three to 10 million years.

We found about 100 free floating planets with ~ 4 to 13 Jupiter masses!

Why “about 100”? Because their true masses depend on the age of the club, which is not precisely defined (3 to 10 Myr). https://t.co/WeUN3gXGBm

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– Sean Raymond (@sraymond_astro) December 22, 2021

Speculation about FFPs has puzzled scientists over the decades. Some parties may believe that FFPs are just failed stars traversing the galaxy like lost souls. But Raymond disagrees.

Are all of these rogue planets just tiny failed stars?

Probably not. There are too many free floating planets compared to several different initial mass functions.

Models don’t predict enough small stars.

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– Sean Raymond (@sraymond_astro) December 22, 2021

Almost 90 percent of the study sample could have formed around stars. They were later expelled during dynamic instabilities, researchers say.

A significant portion (up to 90%) of our sample of rogue planets could have formed around stars and ejected in dynamic instabilities

Dynamic instabilities (also known as planet-planet scatter) are nicely illustrated in this animation by Eric Ford https://t.co/mPHP4qSVyb

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– Sean Raymond (@sraymond_astro) December 22, 2021

Here are the factors that determine the number of planets ejected:

The number of planets ejected depends on 1) the frequency of occurrence of massive exoplanets around stars, 2) the proportion of systems that become unstable at very early times, and 3) the number of planets ejected per instability

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– Sean Raymond (@sraymond_astro) December 22, 2021

The new discovery is important as it provides scientists with a wide variety of FFPs to construct and study models of star and planet formation.

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