Skip to main content

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

Astronomers discover two rogue planets that do not orbit a star

Astronomers from Warsaw University in Poland have identified two “rogue planets” in our galaxy that do not orbit around a star. Unlike the vast majority of discovered planets, these rogue planets drift through space alone with no sun to shine on them.

Debate has raged in astronomical circles for years as to whether rogue planets could exist. Since they do not have a star to illuminate them, they are extremely difficult to find as they are almost always in the dark. However, a technique called gravitational microlensing allowed researchers to identify rogue planets by seeing when a planet comes between a distant star and the Earth. When this happens, the planet acts like a lens, distorting the light that we can see from that star when it reaches Earth. This indicates that a massive body like a planet is passing in front of the star, and the size of the body can be estimated from the size of the distortion.

Recommended Videos

The two discovered rogue planets are called OGLE-2017-BLG-0560 and OGLE-2012-BLG-1323, named after the Optical Gravitational Lensing Experiment (OGLE) survey that discovered them. The first planet detected, OGLE-2017-BLG-0560, was detected in April 2017 and could be between one and twenty times the mass of Jupiter. Finding evidence of this planet inspired the scientists to look back through their older research data for similar evidence, which is how they discovered the smaller OGLE-2012-BLG-1323, somewhere between Neptune and Earth in size, which was first captured in August 2012. The results were published in the preprint journal archive arXiv.

This makes the planets two of only a small handful of rogue planets that have been identified so far. The reason that the researchers cannot be sure of the exact size of each planet is that they cannot know how far the planets are from Earth. Therefore, the planets could be larger and further away or smaller and closer and produce the same gravitational effect on the light from distant stars.

Even though they are hard to spot, some astronomers predict that rogue planets are not rare in our galaxy. Neil DeGrasse Tyson speculated that there could be billions of rogue planets out in the cold of space, created in the chaotic births of solar systems and flung out into space.

Georgina Torbet
Georgina has been the space writer at Digital Trends space writer for six years, covering human space exploration, planetary…
Astronomers discover a super-Earth located in the habitable zone
This illustration shows one way that planet TOI-715 b, a super-Earth in the habitable zone around its star, might appear to a nearby observer.

Astronomers have discovered a type of exoplanet called a "super-Earth" located in the habitable zone of its small star, and it's right in our cosmic backyard, just 137 light-years away. The planet, named TOI-715 b, is intriguing to astronomers who are increasingly interested in the possibility of habitable planets orbiting stars quite different from our sun.

Although it might seem to make sense to look for potentially habitable planets when looking for Earth-like planets orbiting sun-like stars, those aren't the only targets that astronomers are interested in. One issue is that most discovered exoplanets are much larger than Earth, partly because it is so hard to detect smaller planets. Another issue is that the most common star in our galaxy by far is not a yellow dwarf star like our sun, but a smaller, dimmer, redder type called a red dwarf. When researchers discover rocky planets orbiting around red dwarfs, a few of which have been identified to date, that increases the pool of potentially habitable worlds that could be out there.

Read more
Astronomers discover extremely hot exoplanet with ‘lava hemisphere’
Like Kepler-10 b, illustrated above, the exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star. HD 63433 d is the smallest confirmed exoplanet younger than 500 million years old. It's also the closest discovered Earth-sized planet this young, at about 400 million years old.

Astronomers have discovered an Earth-sized exoplanet with an unusually extreme climate where one half of the planet is thought to be covered in lava. The planet HD 63433 d is tidally locked, meaning one side of it always faces its star while the other half always faces out into space, creating a huge difference in temperatures between the planet's two faces.

Like Kepler-10 b, illustrated above, the exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star. HD 63433 d is the smallest confirmed exoplanet younger than 500 million years old.  NASA/Ames/JPL-Caltech/T. Pyle

Read more
Astronomers spot rare star system with six planets in geometric formation
Orbital geometry of HD110067: Tracing a link between two neighbour planets at regular time intervals along their orbits, creates a pattern unique to each couple. The six planets of the HD110067 system together create a mesmerising geometric pattern due to their resonance-chain.

Astronomers have discovered a rare star system in which six planets orbit around one star in an elaborate geometrical pattern due to a phenomenon called orbital resonance. Using both NASA's Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency's (ESA) CHaracterising ExOPlanet Satellite (CHEOPS), the researchers have built up a picture of the beautiful, but complex HD110067 system, located 100 light-years away.

The six planets of the system orbit in a pattern whereby one planet completes three orbits while another does two, and one completes six orbits while another does one, and another does four orbits while another does three, and so one. The six planets form what is called a "resonant chain" where each is in resonance with the planets next to it.

Read more