Nav: Home

Rogue planets could outnumber the stars

August 21, 2020

COLUMBUS, Ohio - An upcoming NASA mission could find that there are more rogue planets - planets that float in space without orbiting a sun - than there are stars in the Milky Way, a new study theorizes.

"This gives us a window into these worlds that we would otherwise not have," said Samson Johnson, an astronomy graduate student at The Ohio State University and lead author of the study. "Imagine our little rocky planet just floating freely in space - that's what this mission will help us find."

The study was published today in he Astronomical Journal.

The study calculated that NASA's upcoming Nancy Grace Roman Space Telescope could find hundreds of rogue planets in the Milky Way. Identifying those planets, Johnson said, will help scientists infer the total number of rogue planets in our galaxy. Rogue, or free-floating, planets are isolated objects that have masses similar to that of planets. The origin of such objects is unknown, but one possibility is they were previously bound to a host star.

"The universe could be teeming with rogue planets and we wouldn't even know it," said Scott Gaudi, a professor of astronomy and distinguished university scholar at Ohio State and a co-author of the paper. "We would never find out without undertaking a thorough, space-based microlensing survey like Roman is going to do."

The Roman telescope, named for NASA's first chief astronomer who was also known as the "mother" of the Hubble telescope, will attempt to build the first census of rogue planets, which could, Johnson said, help scientists understand how those planets form. Roman will also have other objectives, including searching for planets that do orbit stars in our galaxy.

That process is not well-understood, though astronomers know that it is messy. Rogue planets could form in the gaseous disks around young stars, similar to those planets still bound to their host stars. After formation, they could later be ejected through interactions with other planets in the system, or even fly-by events by other stars.

Or they could form when dust and gas swirl together, similar to the way stars form.

The Roman telescope, Johnson said, is designed not only to locate free-floating planets in the Milky Way, but to test the theories and models that predict how these planets formed.

Johnson's study found that this mission is likely to be 10 times more sensitive to these objects than existing efforts, which for now are based on telescopes tethered to the Earth's surface. It will focus on planets in the Milky Way, between our sun and the center of our galaxy, covering some 24,000 light years.

"There have been several rogue planets discovered, but to actually get a complete picture, our best bet is something like Roman," he said. "This is a totally new frontier."

Rogue planets have historically been difficult to detect. Astronomers discovered planets outside Earth's solar system in the 1990s. Those planets, called exoplanets, range from extremely hot balls of gas to rocky, dusty worlds. Many of them circle their own stars, the way Earth circles the sun.

But it is likely that a number of them do not. And though astronomers have theories about how rogue planets form, no mission has studied those worlds in the detail that Roman will.

The mission, which is scheduled to launch in the next five years, will search for rogue planets using a technique called gravitational microlensing. That technique relies on the gravity of stars and planets to bend and magnify the light coming from stars that pass behind them from the telescope's viewpoint.

This microlensing effect is connected to Albert Einstein's Theory of General Relativity and allows a telescope to find planets thousands of light-years away from Earth--much farther than other planet-detecting techniques.

But because microlensing works only when the gravity of a planet or star bends and magnifies the light from another star, the effect from any given planet or star is only visible for a short time once every few million years. And because rogue planets are situated in space on their own, without a nearby star, the telescope must be highly sensitive in order to detect that magnification.

The study published today estimates that this mission will be able to identify rogue planets that are the mass of Mars or larger. Mars is the second-smallest planet in our solar system and is just a little bigger than half the size of Earth.

Johnson said these planets are not likely to support life. "They would probably be extremely cold, because they have no star," he said. (Other research missions involving Ohio State astronomers will search for exoplanets that could host life.)

But studying them will help scientists understand more about how all planets form, he said.

"If we find a lot of low-mass rogue planets, we'll know that as stars form planets, they're probably ejecting a bunch of other stuff out into the galaxy," he said. "This helps us get a handle on the formation pathway of planets in general."
-end-
CONTACT: Samson Johnson, johnson.7080@osu.edu Scott Gaudi, gaudi.1@osu.edu

Written by: Laura Arenschield, arenschield.2@osu.edu

Ohio State University

Related Solar System Articles:

Second alignment plane of solar system discovered
A study of comet motions indicates that the Solar System has a second alignment plane.
Pressure runs high at edge of solar system
Out at the boundary of our solar system, pressure runs high.
What a dying star's ashes tell us about the birth of our solar system
A UA-led team of researchers discovered a dust grain forged in a stellar explosion before our solar system was born.
What scientists found after sifting through dust in the solar system
Two recent studies report discoveries of dust rings in the inner solar system: a dust ring at Mercury's orbit, and a group of never-before-detected asteroids co-orbiting with Venus, supplying the dust in Venus' orbit.
Discovered: The most-distant solar system object ever observed
A team of astronomers has discovered the most-distant body ever observed in our solar system.
Discovery of the first body in the Solar System with an extrasolar origin
Asteroid 2015 BZ509 is the very first object in the Solar System shown to have an extrasolar origin.
First interstellar immigrant discovered in the solar system
A new study has discovered the first known permanent immigrant to our solar system.
A star disturbed the comets of the solar system in prehistory
About 70,000 years ago, when the human species was already on Earth, a small reddish star approached our solar system and gravitationally disturbed comets and asteroids.
Scientists detect comets outside our solar system
Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets -- comets outside our solar system -- orbiting a faint star 800 light years from Earth.
Does the organic material of comets predate our solar system?
The Rosetta space probe discovered a large amount of organic material in the nucleus of comet 'Chury.' In an article published by MNRAS on Aug.
More Solar System News and Solar System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.