Skip to main content

Digital Trends may earn a commission when you buy through links on our site. Why trust us?

Largest ever group of lonely rogue planets discovered in Milky Way

Deep in the cold, dark emptiness of interstellar space, you can find some lonely planets roaming freely and not orbiting a star. Known as rogue planets, these objects are elusive and are rarely discovered due to being difficult to spot — but a new study has found the largest collection of rogue planets to date, located in a region of the Milky Way called the Upper Scorpius OB stellar association.

Finding rogue planets is hard because, unlike stars, planets are dim and give off very little light, and these tiny points have to be picked out from a background of bright stars. But an international team was able to spot this group of rogue planets by using a combination of both new observations and archival data from a large number of sources including telescopes of the European Southern Observatory, the Canada-France-Hawaii Telescope, and the Subaru Telescope. In total, the data they used added up to 80,000 wide-field images taken over 20 years of observations.

Artist’s impression shows an example of a rogue planet with the Rho Ophiuchi cloud complex visible in the background.
This artist’s impression shows an example of a rogue planet with the Rho Ophiuchi cloud complex visible in the background. Rogue planets have masses comparable to those of the planets in our Solar System but do not orbit a star, instead, roaming freely on their own. ESO/M. Kornmesser

“We measured the tiny motions, the colors and luminosities of tens of millions of sources in a large area of the sky,” explained lead author Núria Miret-Roig. “These measurements allowed us to securely identify the faintest objects in this region.” Using this technique, the researchers found at least 70 rogue planets from the data. “We did not know how many to expect and are excited to have found so many,” said Miret-Roig.

Studying these rogue planets, or Free-Floating Planets (FFPs), in more detail could help us learn about planet composition and formation, according to project leader Hervé Bouy: “The FFPs we identified are also excellent targets for follow-up studies. In particular, they will be essential to study planetary atmospheres in the absence of a blinding host star, making the observation far easier and more detailed. The comparison with atmospheres of planets orbiting stars will provide key details about their formation and properties. Additionally, studying the presence of gas and dust around these objects, what we call ‘circumplanetary discs’, will shed more light on their formation process.”

This could be just the tip of the iceberg where rogue planets are concerned. There could potentially be billions of them in our galaxy. “Assuming the fraction of FFPs that we measured in Upper Scorpius is similar to that of other star-forming regions, there could be several billions of Jupiters roaming the Milky Way without a host star. This number would be even greater for Earth-mass planets since they are known to be more common than massive planets.”

The research is published in the journal Nature.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Browse through 3B celestial objects in Milky Way survey
Astronomers have released a gargantuan survey of the galactic plane of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. The data for this unprecedented survey were taken with the US Department of Energy-fabricated Dark Energy Camera at the NSF’s Cerro Tololo Inter-American Observatory in Chile, a Program of NOIRLab.

A new survey of the Milky Way has been released containing more than 3 billion objects, making it one of the largest astronomical catalogs ever produced. The second data release of the Dark Energy Camera Plane Survey, or DECaPS2, focuses on the galactic plane, which is the view looking across the disk of the galaxy in which most of the stars are located and covers 6.5% of the night sky.

The dataset is available to astronomers to use in their research, but it's also available for the public to view online in a web browser. The Legacy Survey Viewer shows a variety of different survey images -- you can select DECaPS2 images in the box in the top right to view the new data, and zoom in and out using the slider in the top left.

Read more
James Webb spots early galaxies similar to our Milky Way
The power of JWST to map galaxies at high resolution and at longer infrared wavelengths than Hubble allows it look through dust and unveil the underlying structure and mass of distant galaxies. This can be seen in these two images of the galaxy EGS23205, seen as it was about 11 billion years ago. In the HST image (left, taken in the near-infrared filter), the galaxy is little more than a disk-shaped smudge obscured by dust and impacted by the glare of young stars, but in the corresponding JWST mid-infrared image (taken this past summer), it’s a beautiful spiral galaxy with a clear stellar bar.

As the James Webb Space Telescope looks back at some of the earliest galaxies, it is helping us learn not only about galaxies very different from our own but also about how galaxies similar to the Milky Way were first formed. Recently astronomers announced they have used Webb to discover some of the earliest galaxies with a feature called stellar bars, making them similar to our barred spiral galaxy seen today.

A galaxy bar refers to a strip of dust and gas that forms a structure across the center of a galaxy, and which is frequently visible as a bright stripe across a galaxy in images. It is thought that these structures develop as a galaxy ages, as dust and gas are drawn toward the galactic center. So it was remarkable to see a bar in a galaxy from a very early period when the universe was 25% of its current age.

Read more
How the ‘hell planet’ covered in lava oceans got so close to its star
An artist’s impression of the planet Janssen (orange circle), which orbits its star so closely that its entire surface is a lava ocean that reaches temperatures of around 2,000 degrees Celsius.

Of the over 5,000 known planets outside our solar system, one of the most dramatic is 55 Cancri e. Affectionately known as the "hell planet," it orbits so close to its star that it reaches temperatures of 3,600 degrees Fahrenheit and its surface is thought to be to covered in an ocean of lava. Located 40 light-years away, the planet has been a source of fascination for its extreme conditions, and recently researchers shared a new theory for how it got so hot.

The planet orbits its star, 55 Cancri A, at a distance of 1.5 million miles which means a year there lasts less than a day here on Earth. “While the Earth completes one orbit around our sun in 365 days, the planet studied here orbits once every 17.5 hours, hugging its host star, 55 Cnc,” said study author Debra Fischer of Yale University in a statement.

Read more