Nancy Roman Space Telescope holds potential to find 400 rogue planets in Milky Way

The estimate of 400 rogue planets comes from a nine-year-long survey called Microlensing Observations in Astrophysics (MOA).

Mrigakshi Dixit

| Jul 20, 2023 06:53 AM EST

Created: Jul 20, 2023 06:53 AM EST

science

This artist's concept shows an ice-encrusted, Earth-mass rogue planet drifting through space alone.

NASA’s Goddard Space Flight Center

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The Nancy Roman Grace Telescope, an upcoming space observatory, might aid in the discovery of hundreds of rogue exoplanets.

Planets of this sort float freely through galaxies and are not gravitationally tied to any star system.

NASA and Osaka University scientists estimate that the telescope could locate around 400 such planets, with the number anticipated to grow once it begins actual hunting from its perch approximately a million miles away from Earth.

“We estimate that our galaxy is home to 20 times more rogue planets than stars – trillions of worlds wandering alone. This is the first measurement of the number of rogue planets in the galaxy that is sensitive to planets less massive than Earth,” said David Bennett, a senior research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in an official release.

Finding such lone wanderers

The estimate of 400 rogue planets comes from a nine-year-long survey called Microlensing Observations in Astrophysics (MOA) conducted at New Zealand's Mount John University Observatory.

Only one approach, known as a microlensing event, can detect rogue planets. It is a type of gravitational lensing that is useful for detecting low-mass planets from a long distance.

“Microlensing events occur when an object such as a star or planet comes into near-perfect alignment with an unrelated background star from our vantage point,” explains NASA statement.

However, there is a catch: these planets are extremely rare to identify as a microlensing event is a “one-time occurrence.” Therefore, there are fewer opportunities for follow-up observations.

For this reason, the Roman telescope will operate simultaneously with ground-based telescopes, mainly Japan's PRIME (Prime-focus Infrared Microlensing Experiment) at the South African Astronomical Observatory in Sutherland.

Using four detectors, a 1.8-meter PRIME telescope will undertake wide-area microlensing surveys in near-infrared light.

As a result, when a microlensing signal from a rogue planet reaches Earth, Roman and PRIME will be able to collect an adequate amount of data in a short time.

“Roman will be sensitive to even lower-mass rogue planets since it will observe from space. The combination of Roman’s wide view and sharp vision will allow us to study the objects it finds in more detail than we can do using only ground-based telescopes, which is a thrilling prospect,” said Naoki Koshimoto, an assistant professor at Osaka University.

One rogue planet candidate has already been discovered for future observations by the Roman space telescope, which is set to launch in May 2027.

The two discoveries — one of a possible rogue planet and a 400 demographic study — will be published separately in the Astronomical Journal.