Planets orbiting deceptively no star. They wander the void of space on their own, having been evicted from their star systems by gravitational interactions with other planets and stars. No one really knows how many rogue planets there could be, but that could change in a few years.
Researchers from NASA’s Goddard Space Flight Center and Osaka University in Japan used the phenomenon of microgravity to estimate the number of rogue planets that could be detected in the heart of the Milky Way. They analyzed data from Microlens astrophysics (MOA) observations A survey that looked for gravitational microevents from 2006 to 2014 to see how many of these we can expect to find with NASA’s upcoming Nancy Grace Romanian Space Telescope.
There are currently only 70 known rogue planets, but there could be hundreds more. Now researchers suggest that Roman could spot at least 400 Earth-mass rogues prowling through our galaxy.
Use gravity as a magnifying glass
Anything with mass bends space-time because gravity is the curvature of space-time. When an object passes in front of a distant star, galaxy, or galaxy cluster without being perfectly aligned with it, the light from that star (or other light-emitting object) will pass through space curved by the mass of the object. This curved area can magnify the object like a lens, amplifying the brightness of the background star, making it more visible. This phenomenon is known as gravitational lensing.
Most rogue planets tend to be on the smaller side because less mass puts a planet at greater risk of being expelled from its outer system. Their small size and the fact that they are not associated with a star makes them very difficult to spot. But subtle gravitational lensing could help scientists.
Microlensing events occur in the same way as other gravitational lensing events, except microlensing refers to the lensing done by smaller objects. Because of the lower mass of many rogue planets, they create a weaker lensing effect which makes the events more difficult to see. However, a number of these microlensing events have been detected, so we know rogue planets are out there.
Rogue planets ranging from the mass of Mars to that of Earth will be future targets for the Roman telescope. Because they cross in front of a star and space-time bends (and thus the starlight bends), most of them may last no more than a day, but that is usually long enough to make observations.
The only telescope looking for separate planets
Launched in 2027, the Roman telescope will search for rogue planets in the heart of the Milky Way. The research team decided to see how many planets we might expect to find. To do this, they used data from the USDA and the Optical Gravitational Lensing Experiment (OGLE) to estimate how many of these planets there are. This approximation was then used to predict how many would be found in the central galactic bulge of the Milky Way based on the capabilities of the Roman telescope.
“We estimate that our galaxy is home to 20 times more evil planets than stars — trillions of worlds walking around on their own,” said one of the paper’s authors, senior researcher David Bennett of NASA’s Goddard Space Flight Center. press release. “This is the first measurement of the number of rogue planets in a galaxy sensitive to planets less massive than Earth.”
Bennett and his colleagues also estimated that there are at least six times more small rogue planets than planets with wide orbits in the center of our galaxy, meaning their orbits are farther from their star. The masses of these expected rogues lie between Mars and Earth, based on the pieces the researchers used.
If some planets of this mass have wide orbits and their masses are consistent with many rogue planets, this could mean that some rogue planets around the mass of Earth were also once in wide orbits around stars but were thrown into space by intense gravitational interactions with objects in their outer systems previous. They could also have been expelled during the turbulent formation of their star systems.
Roman’s instruments should be able to capture more microlensing events that reveal these planets than previous surveys. She already had high expectations to live up to. For now, at least we have an idea of what could be lurking there.
Elizabeth Raine Creature Writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. When she’s not writing, she’s either shape-shifting, drawing, or masquerading as a character no one has ever heard of. Follow her on Twitter: @hravenrayne.
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