Astronomers found the smallest “Rogue Planet“The candidate does not yet know that this world may be smaller than the earth, and it is clearly sailing in the Milky Way galaxy not attached to stars.
The mass of potential exoplanets is between Earth and Mars, and weighs only 10% of our world.If confirmed, this discovery will be an important milestone in the study of rogue planets, which are considered to be Very rich The entire galaxy and other places, but it is difficult to find.
“Our findings indicate that low-mass free-floating planets can be detected using ground-based telescopes,”
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Common but ugly
Astronomers have found more than 4000 confirmed Exoplanet to date. Most of them are discovered through the “transition method”, which records the decrease in brightness caused by a world passing over the face of its host star from the observer’s perspective, or the “radial velocity method”, which can be found by Star motion caused by planetary gravity. .
Both of these techniques depend on the existence of the host star, so they cannot be used to find a rogue world. But another planet search technology can accomplish this task -“Gravitational Microlens“It involves observing the foreground object passing in front of a distant background star. When this happens, the close body can act as a gravitational lens, bending and magnifying the light of the star in a way that reveals the mass and other characteristics of the foreground object.
“Opportunity to observe the microlens [events] The reason for being very slim is because of three objects- [light] The lead author of the study, Przemek Mroz, a postdoctoral researcher at the California Institute of Technology in Pasadena, said in the same statement: “The source, lens, and observer must be almost perfectly aligned.” Waiting for nearly a million years to see that the light source is Microlens. “
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But planet hunters like Mroz did not observe a single star at a time. For example, in the new study, Mroz and his colleagues analyzed data collected by OGLE. The project, led by the University of Warsaw in Poland, uses a 1.3-meter telescope at the Las Campanas Observatory in Chile to monitor millions of stars near the center of the Milky Way on a clear night.
The researchers extracted a very interesting signal from OGLE observations-an event called OGLE-2016-BLG-1928, which was the shortest microlens event ever detected in 42 minutes. The team further used data collected by the South Korean microlens telescope network operating telescopes in Chile, Australia and South Africa to describe the incident.
Radoslaw Poleski, a co-author of the University of Warsaw Observatory, said in the same statement: “When we first discovered this event, it was clear that it must have been caused by a very small object. of.
The research team’s calculations show that the mass of the lens is between Mars and the Earth, and the distance to the red planet may be closer than the distance to our own world. OGLE-2016-BLG-1928 candidates are likely to travel through deep space lonely.
“If the lens orbits the star, we will detect its presence in the light curve of the event,” Poleski said. “We can exclude planets that have a star within about 8 AU.”
An astronomical unit, or AU, is the average distance from the earth to the sun-about 93 million miles (150 million kilometers). In our own solar system, an 8 AU celestial body will orbit the sun between Jupiter and Saturn, which is a strange place for a small rocky planet.
The new research was published online today (October 29) in the Astrophysical Journal Letters.You can read its preprint for free At arXiv.org.
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Start from home
So far, astronomers have discovered only a few confirmed rogue planets.However, this figure shows high populationScientists say that given these exotic worlds, it is difficult to discover.
Astronomers believe that most rogue planets are born in a “normal” way. They are formed by condensing gas and dust around newly formed stars. However, these worlds are finally freed from the native system through the gravitational interaction with other objects, especially their Qi giant brothers and sisters.
Theoretically, most hooligans shot in this way are rock worlds with a mass of 30% to 100% of the earth, Mroz and colleagues point out in a new study. Therefore, the OGLE-2016-BLG-1928 candidate is likely to represent a flooded but elusive rogue population.
We can begin to better deal with this population problem soon. E.g, NASA’s Nancy Grace Roman Space TelescopeThis project, planned to be launched in the mid-2020s, will conduct large-scale microlens surveys and other scientific tasks. The survey may find about 250 rogue planets, of which about 60 are Earth-mass or lighter planets. A recent study found.
Mike Wall (Mike Wall) is “outside“(Grand Central Press, 2018; Karl Tate illustration), this is a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook .