Similar in size to Jupiter, these gas-dominated planets orbit extremely close to their parent stars, circling them in as few as 18 hours. We have nothing like them in our own solar system, where the closest planets to the Sun are rocky and orbiting much farther away. The questions about hot Jupiters are as big as the planets themselves: Do they form close to their stars or farther away before migrating inward? And if these giants do migrate, what would that reveal about the history of the planets in our own solar system?
To answer those questions, scientists will need to observe many of these hot giants very early in their formation. The detection of the exoplanet HIP b , thought to be the youngest hot Jupiter ever found in June , could expand our understanding.
It orbits a well-studied star that is about 17 million years old, meaning the hot Jupiter is likely only a few million years younger, whereas most known hot Jupiters are more than a billion years old.
The planet takes about seven days to orbit its star, which has a mass similar to the Sun's. Located only about light-years from Earth, HIP b is about 10 times the diameter of Earth, or close to that of Jupiter. Its size strongly indicates that it is a gas-dominated planet. The discovery offers hope for finding more young hot Jupiters and learning more about how planets form throughout the universe. There are three main hypotheses for how hot Jupiters get so close to their parent stars.
One is that they simply form there and stay put. But it's hard to imagine planets forming in such an intense environment. Not only would the scorching heat vaporize most materials, but young stars frequently erupt with massive explosions and stellar winds, potentially dispersing emerging planets. It could be more likely that gas giants develop farther from their parent star, past a boundary called the snow line, where it's cool enough for ice and other solid materials to form.
Jupiter-like planets are composed almost entirely of gas, but they contain solid cores. It would be easier for those cores to form past the snow line, where frozen materials could cling together like a growing snowball. The other two hypotheses assume this is the case, and that hot Jupiters then wander closer to their stars. But what would be the cause and timing of the migration? One idea posits that hot Jupiters begin their journey early in the planetary system's history while the star is still surrounded by the disk of gas and dust from which both it and the planet formed.
In this scenario, the gravity of the disk interacting with the mass of the planet could interrupt the gas giant's orbit and cause it to migrate inward.
The third hypothesis maintains that hot Jupiters get close to their star later, when the gravity of other planets around the star can drive the migration. The fact that HIP b is already so close to its star so early after its formation indicates that this third hypothesis probably doesn't apply in this case.
But one young hot Jupiter isn't enough to settle the debate on how they all form. Located less than 32 light-years from Earth, AU Microscopii is among the youngest planetary systems ever observed by astronomers, and its star throws vicious temper tantrums!
Weather here is deadly. The cobalt color comes from a hazy, blow-torched atmosphere containing clouds laced with glass. In , astronomers using NASA's Spitzer Space Telescope found evidence showing that gas-giant planets form quickly, within the first 10 million years of a Sun-like star's life. Gas giants could get their start in the gas-rich debris disk that surrounds a young star. A core produced by collisions among asteroids and comets provides a seed, and when this core reaches sufficient mass, its gravitational pull rapidly attracts gas from the disk to form the planet.
When classifying these gaseous planets, it should be mentioned that, due to the difference that these planets have in their structure and composition, they also differ between them. Jupiter and Saturn are classified as gas giants, while Uranus and Neptune are ice giants. Due to the distance from the sun that they occupy in the solar system, they have the nuclei composed of rock and ice.
Among the main differences that we see with respect to the rocky planets is that the gaseous planets are composed mainly of hydrogen, helium and methane. That is, they are composed mainly of gases, while the other planets of rocks. Rocky planets have mostly a solid surface and are made up of rocks. Another major difference is that the surface of rocky planets is well defined.
The rocky planets have secondary atmospheres that have emerged from internal geological processes while the rocky planets gaseous planets have primary atmospheres that have been captured directly from the original solar nebula. These planets are being studied in greater detail given human technology.
I hope that with this information you can learn more about the gaseous planets and their characteristics. The content of the article adheres to our principles of editorial ethics. It has 13 confirmed moons and an additional one awaiting confirmation, according to NASA. It was discovered by several people in Super-Earths: Scientists have found a multitude of "super-Earths" planets between the size of Earth and Neptune in other solar systems. There are no known super-Earths in our own solar system, although some scientists speculate there may be a "Planet Nine" lurking in the outer reaches of our solar system.
Scientists are studying this category of planets to learn whether super-Earths are more like small giant planets or big terrestrial planets. Astronomers think the giants first formed as rocky and icy planets similar to terrestrial planets. However, the size of the cores allowed these planets particularly Jupiter and Saturn to grab hydrogen and helium out of the gas cloud from which the sun was condensing, before the sun formed and blew most of the gas away.
Since Uranus and Neptune are smaller and have bigger orbits, it was harder for them to collect hydrogen and helium as efficiently as Jupiter and Saturn. This likely explains why they are smaller than those two planets. On a percentage basis, their atmospheres are more "polluted" with heavier elements such as methane and ammonia because they are so much smaller.
Scientists have discovered thousands of exoplanets. Many of these happen to be "hot Jupiters," or massive gas giants that are extremely close to their parent stars. Rocky worlds are more abundant in the universe, according to estimates from Kepler.
Scientists speculate that large planets may have moved back and forth in their orbits before settling into their current configuration. But how much they moved is still a subject of debate. There are dozens of moons around the giant planets. Many formed at the same time as their parent planets, which is implied if the planets rotate in the same direction as the planet close to the equator such as the huge Jovian moons Io, Europa, Ganymede and Callisto.
But there are exceptions. One moon of Neptune, Triton, orbits the planet opposite to the direction Neptune spins — implying that Triton was captured, perhaps by Neptune's once larger atmosphere, as it passed by. And there are many tiny moons in the solar system that rotate far from the equator of their planets, implying that they were also snagged by the immense gravitational pull.
Jupiter: NASA's Juno spacecraft arrived at the planet in and has already made several discoveries. It studied the planet's rings, which is difficult to achieve since they are far subtler than Saturn's.
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