We currently know of more than 5,000 exoplanets that are part of star systems. One of the satellites hunting them is TESS, the Transiting Exoplanet Survey Satellite. TESS astronomers believe they have made a surprising discovery, as the instrument has found the first free-floating, or stray, planet.
The planet was discovered thanks to gravitational microlensing, when the planet passes in front of a star, distorting its light and revealing its presence, Universe Today reports.
Stray planets drift without a parent star in the infinite universe. NASA/JPL-Caltech
We probably all know the planets of our solar system, and we hear the term exoplanet more and more. This applies to planets in other star systems, but they also have a third group, the stray planets.
They can’t help it
These mysterious objects drift through space without a star of their own. Their origin is still a matter of debate, but they were probably ejected from their star system during their formation or somewhat later as a result of gravitational interaction.
Simulations have suggested that these “free-floating planets” (FFPs) should be abundant in the galaxy, but so far few such planets have been detected.
However, the popular theory of ejection from stellar systems may not cover the whole story. Different genesis events are now believed to be responsible for the different FFP masses.
Planets that are high in mass may have formed in isolation from gas collapse, while low-mass planets similar to Earth likely met this fate by gravitational ejection.
Even conservative estimates of the number of stray planets are scarce
According to a study published in 2023, it is even in the deck that these stray planets are likely to be present in greater numbers in the galaxy than their star-bearing counterparts.
Detecting such wandering objects among the stars is more challenging for researchers than they thought. Due to the limited emission of electromagnetic radiation, it is almost impossible to observe them.
Gravitational microlensing is a technique that relies on a stray planet passing in front of a star. In doing so, the planet’s gravity focuses the light from the distant star, resulting in a brief change in brightness as the planet moves along its line of sight.
So far, only three stray planets have been detected from Earth using this technique.
A group of astronomers is using TESS to search for such microlensing events. TESS began operations in April 2018, and during its orbit it scans large slices of the sky simultaneously to monitor the brightness of tens of thousands of stars.
Detecting changes in light can reveal the passage of such an object as it passes in front of the star.
Finding one, however, is not an easy task, as asteroids in our solar system, exoplanets bound to stars, and even starbursts can give a false signal.
Fortunately, however, a team led by Michelle Kunimoto has algorithms to help identify potential targets.
The research team recently published their findings in the Astrophysical Journal and reported a possible FFP event associated with the star TIC-107150013, 3.2 parsecs away.
The event showed a light curve that contained the characteristics expected of FFP. So it’s the first rogue planet TESS has discovered, and it’s an exciting step toward helping researchers decipher the past of these landless worlds.
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