Skip to main content

Strangely chonky exoplanet has astronomers puzzled

Astronomers recently discovered a hefty exoplanet orbiting a star similar to our sun. At just 15 million years old, this chunky planet is a baby by galactic standards, old, but it has researchers puzzled due to its tremendous density.

The planet, called HD 114082 b, is similar in size to Jupiter, but seems to have eight times its mass. It’s common for astronomers to discover gas giants similar to or larger than Jupiter, but it’s very unusual to discover a planet this dense and heavy.  “Compared to currently accepted models, HD 114082 b is about two to three times too dense for a young gas giant with only 15 million years of age,” said lead author Olga Zakhozhay in a statement.

Artist’s conception of a gas giant exoplanet orbiting around a Sun-like star. The young exoplanet HD 114082 b revolves around its Sun-like star within 110 days at a distance of 0.5 astronomical units.
Artist’s conception of a gas giant exoplanet orbiting around a sun-like star. The young exoplanet HD 114082 b revolves around its sun-like star within 110 days at a distance of 0.5 astronomical units. NASA/JPL-Caltech

If the mass measurements of this planet are correct, that would make it twice as dense as Earth — and Earth is already a dense planet, being a rocky type with a metal core. It could be that because the planet is so young, there is something about the way gas giants form that we are not yet aware of.

“We think that giant planets can form in two possible ways,” Ralf Launhardt, a co-author from the Max Planck Institute for Astronomy, says. “Both occur inside a protoplanetary disk of gas and dust distributed around a young central star.”

The first approach to how planets might form is called core accretion, in which a small core attracts other particles, which collide and stick to it until it becomes the starting point of a planet. The second theory is called disk instability, in which there is a disk of matter that cools and then splits into planet-sized chunks.

Most astronomers lean toward the core accretion theory, but this planet doesn’t fit that model. If it were formed by core accretion, you’d expect it to start off hotter than in the disk instability model, and hot gas should puff up to a larger volume. The small volume of this planet is a better fit with the less popular disk instability model.

However, there are many open questions about how planets form and how quickly they cool after formation. “It’s much too early to abandon the notion of a hot start,” said Launhardt. “All we can say is that we still don’t understand the formation of giant planets very well.”

The research will be published as a letter to the editor in the journal Astronomy & Astrophysics.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
NASA has collected a whopping 121 grams of sample from asteroid Bennu
A view of eight sample trays containing the final material from asteroid Bennu. The dust and rocks were poured into the trays from the top plate of the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) head. 51.2 grams were collected from this pour, bringing the final mass of asteroid sample to 121.6 grams.

When the OSIRIS-REx dropped a capsule in the Utah desert last year, it made headlines around the globe for returning NASA's first sample of an asteroid to Earth. Scientists were eager to get their hands on the sample of asteroid Bennu to learn about the early formation of the solar system, but actually getting at the sample proved to be rather trickier than imagined.

Scientists were able to extract 70 grams of material from the sample canister relatively easily, making it by far the largest asteroid sample ever brought to Earth, but two troublesome fasteners made it difficult to extract the rest of the sample. The team knew it had plenty more sample inside, but it had to be patient as special new tools were constructed that could undo the fasteners without losing a single gram of the precious sample.

Read more
James Webb photographs two potential exoplanets orbiting white dwarfs
Illustration of a cloudy exoplanet and a disk of debris orbiting a white dwarf star.

Even though scientists have now discovered more than 5,000 exoplanets, or planets outside our solar system, it's a rare thing that any telescope can take an image of one of these planets. That's because they are so small and dim compared to the stars that they orbit around that it's easier to detect their presence based on their effects on the star rather than them being detected directly.

However, thanks to its exceptional sensitivity, the James Webb Space Telescope was recently able to image two potential exoplanets orbiting around small, cold cores of dead stars called white dwarfs directly.

Read more
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