The universe is vast – perhaps infinite – and in the scheme of things, our planet is small. Even in our area Solar SystemEarth is dwarfed by gas giants such as… Jupiter. But are there bigger planets? How much bigger? What is the largest planet we know of?
The answer depends on several factors, including how you define a planet. However, there are a few candidates for the largest known planet. One of the largest of these planets is called ROXs 42Bb, a gas giant orbiting a star about 460 light-years away from us. Land. Its mass is about nine times that of Jupiter and its radius is about 2.5 Jupiter radii.
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Thane KoreanAn associate professor of physics and astronomy at the University of Texas-San Antonio told Space.com he thinks it’s unlikely that the planet is truly the largest. Curie identified ROXs 42Bb from data from the Keck Space Telescope in 2013 (another group independently identified the object around the same time). There are known objects of approximately the same size Exoplanet “And bigger than that,” Corey continued.
“There are two planets that are actually protoplanets, so they are still being assembled,” he said. “I doubt these are actually bigger.” These two protoplanets orbit the star PDS 70 around 370 Light year From Earth, its radius is between two and four times the radius of Jupiter. Another candidate for the largest planet, HAT-P-67 b, has a radius greater than twice that of Jupiter, which is similar to ROXs 42Bb.
Why uncertainty? One reason has to do with the different ways scientists measure the size of exoplanets. For example, ROXs 42Bb were imaged directly – “seen” as an independent object using the Keck telescope. Protoplanets orbiting PDS 70 have also been directly imaged. Scientists have no way to directly measure the size of these planets, so they have to infer their size based on other factors such as their brightness and the wavelength patterns of light they emit. Scientists use models to determine these things, and these models are not always 100% correct.
Other objects are detected using the transit method, which is when an object appears to cross in front of its host star during its orbit and the star temporarily dims. Exoplanets discovered in this way, such as HAT-P-67 b, can be measured directly. So a better bet might be that the radius of this planet is more than twice that of Jupiter.
The other uncertainty comes from the question of how to define a planet. Although most people know that stars are very large and planets are much smaller, there is a middle ground – an object called a brown dwarf, which is too small to be a star but larger than a planet. Although the brown dwarf’s core is not hot enough to fuse ordinary hydrogen like a star, it can fuse deuterium, a special form of hydrogen that contains a neutron.
Scientists agree that brown dwarfs are not planets. What is less clear is how to distinguish between the two.
“Some people specify a strict block break,” Corey said. “So anything larger than 13 Jupiter masses is a brown dwarf and anything less than that is a planet.”
But more recent observations have revealed this Universe He does not necessarily “agree” with this rule. research Corey and his colleagues highlight that the transition between planet and brown dwarf could occur at a much higher mass — perhaps 25 times the mass of Jupiter, or even more massive. It also appears that how massive the object is compared to its host star or companion star is what matters, Currie said.
Even then, there are some complications. For example, Currie says that although he would call ROXs 42Bb a planet (or a “planetary mass companion”), he doubts that its composition was more similar to how it formed. stars Form. Normally, planets like Jupiter form a rocky core, which attracts a disk of dust and gas that gradually turns into a spherical planet. ROXs 42Bb may have formed in a different way, as parts of the dust and gas disk were so massive and heavy that they collapsed in on themselves.
The way the object is shaped is not currently part of the formal form Definition of planet. Some scientists refer to planetary-mass companions that form like this as “structureless dwarfs,” although Curie said he “couldn’t call that anything.” He said scientists disagree about what to call ROXs 42Bb because of its high mass ratio (its mass compared to the mass of its star) and how far it is from that star — more than five times the distance from our sun. Neptune.
Although the debate over what “counts” as a planet may seem arbitrary, it highlights big questions about what different planetary systems might look like, especially those that differ significantly from our own, Currie says.
“Our solar system is just one of countless outcomes,” he said. “So it’s fun to see how different a planetary system could be.”