Astronomers have noticed the smallest “cheater planet“A candidate, still known, a world, probably smaller than Earth, that apparently travels through our Milky Way galaxy, not attached to a star.
The potential exoplanet has a mass that is somewhere between Earth and Mars, which is only 10% as large as our world. If confirmed, the discovery will be a major milestone in the study of fraudulent planets believed to be incredibly abundant throughout the galaxy and beyond, but are very difficult to detect.
“Our discovery demonstrates that low-mass free-floating planets can be detected and characterized using ground-based telescopes,”
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Common, but difficult to notice
Astronomers have found more than 4,000 confirmed exoplanets to date. Most of them have been detected using the “transit method”, which marks declines in brightness caused when a world crosses the face of the receiving star from an observer’s point of view, or the “radial velocity method”, which notices stellar motions caused by the gravitational pull of the planet.
Both techniques depend on the existence of a receiving star, so they cannot be used to hunt for deceptive worlds. But another planet-hunting technique can work – “gravitational microlensing, “which involves observing foreground objects in front of distant background stars. When this happens, the closer body can act as a gravitational lens, bending and magnifying the star’s light in ways that can reveal the mass of the object. foreground and other features.
“Chances of microlens observation [events] are extremely thin because three objects – [light] source, lens and observer – should be almost perfectly aligned, “said study lead author Przemek Mroz, a postdoctoral fellow at the California Institute of Technology in Pasadena. If we observe only one star source, you will have to wait almost a million years to see the source microlensured. “
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But hunters of planets like Frost do not observe the heavens by a single star. In the new study, for example, Mroz and his colleagues analyzed data collected by OGLE. This project, led by the University of Warsaw in Poland, uses a 1.3-meter telescope at the Las Campanas Observatory in Chile to observe millions of stars near the center of the Milky Way every clear night.
The researchers drew a very interesting signal from OGLE’s observations – an event called OGLE-2016-BLG-1928, which with a duration of 42 minutes is the shortest microlensing event ever detected. The team also characterized the event using data collected by the Korean Microlensing Telescope Network, which operates telescopes in Chile, Australia and South Africa.
“When we first noticed this event, it was clear that it must have been caused by an extremely tiny object,” said co-author Radoslaw Poleski of the Warsaw University Astronomical Observatory in a statement.
The team’s calculations suggest that the lensing body has a mass between the mass of Mars and Earth and is probably closer to the Red Planet than to our own world. And the candidate for OGLE-2016-BLG-1928 is probably approaching through deep space, lonely.
“If the lens was orbiting a star, we would detect its presence in the light curve of the event,” Poleski said. “We can rule out a planet with a star within about 8 astronomical units.”
An astronomical unit or AU is the average distance from Earth to the sun – about 93 million miles (150 million kilometers). In our own solar system the object of 8 a.e. would orbit the sun between Jupiter and Saturn, a strange place for the existence of a small rocky planet.
The new study was published online today (October 29) in the Astrophysical Journal Letters. You can read a preprint of it for free at arXiv.org.
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Started from home
To date, astronomers have found only a few confirmed deceptive planets. But this small number suggests a large population, scientists say, given how difficult it is to find these exotic worlds.
Astronomers believe that most deceptive planets are born in the “normal” way, uniting from gas and dust orbiting a newly formed star. But these worlds were eventually removed from their native systems by gravitational interaction with other bodies, especially their siblings with gas giants.
The theory suggests that most scammers dumped in this way are rocky worlds with masses of 30% to 100% of those on Earth, Mroz and colleagues note in the new study. So the candidate for OGLE-2016-BLG-1928 can be quite representative of the crowded but elusive fraudulent population.
We could soon start to deal with this population much better. For example, NASA’s Roman Nancy Grace Space Telescope, which is due to launch in the mid-2020s, will conduct a major study on microleasing, among other scientific tasks. This study is likely to find about 250 rogue planets, including about 60 that are Earth-mass or lighter, a recent study found.
Mike Wall is the author of “Out there“(Grand Central Publishing, 2018; illustrated by Carl Tate), a book on the search for extraterrestrial life. Follow it on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.