So far astronomers have found more than 4,000 exoplanets (alien planets orbiting other stars).
There are several ways to find them, most of which use indirect methods, but one of the most fun is direct: getting real images of the planets near their host stars. He called direct image, this technique has been used to find dozens of planets.
A team of astronomers has targeted 70 nearby stars to search for these exoplanets and has just announced a new one: YSES 2b, a giant planet orbiting a star just 360 light-years away.
We have already seen some similar ones, but in this case this planet is special. On the one hand, it is orbiting a star that will one day look a lot like the Sun. On the other hand, it is orbiting at least 16.5 billion kilometers of the star, 110 times farther from its star than the Earth of the Sun.
It’s a very, very long road, and what it’s doing so far is a mystery.
Direct imaging works best for finding very young planets, up to a few dozen million years old. The formation of the planet is a violent and energetic process, so these young planets are hot. They glow brightly in the infrared (IR) part of the spectrum, so astronomers use IR cameras on large telescopes to find them. This has a side advantage: stars are usually weaker in IR than in visible light, making it easier to see any planet.
Astronomers who found this new planet conducted a survey called the Young Suns Exoplanet Survey, or YSES, and are seeing a group of nearby young stars called the lower Centaur Crux subgroup, part of a group of very loose stars. largest called the Scorpius-Centaurus association. These stars are very young, about 14 million years old (the Sun is 4.6 billion years old, by comparison, so these stars are babies) and are only about 350 light-years away, close enough that an exoplanet can separate from its star. enough to detect in images.
We know that stars more massive than the Sun tend to have more massive planets, so to avoid any bias like this, the survey looks only at stars with masses similar to the Sun. They target 70 stars in this group.
YES 2* it is the second star they have seen where they have found a planet (they have observed about 45 more, but they are still working to find planets around them). It has a mass 1.1 times that of the Sun, so it is very similar, though cooler at this time (over time it will probably become hotter once it is established and kept stable). We are about 360 light years from ourselves.
The planet looks like a background star and is so far from the star that it is not possible to see any orbital motion (it will be many years before it moves noticeably). To confirm that an exoplanet is accompanied by a host star, the team takes images of each star one year apart. The stars are moving as they orbit around the center of the galaxy, and the pointed stars are close enough to Earth for this motion to appear large (such as when it is in a car and trees pass by while a distant mountain just looks like moves all). If the candidate planet is really a companion, it will move along with the star. If it’s a background star, it won’t.
Images taken a year apart show that the object actually moves with the star, so it is a companion. Using physical models of how planets cool after formation, they find that it has a mass of 5 to 8 times that of Jupiter, with a mass probably about 6 Jupiter, making it a true planet. This is how they named it YSES 2b.
The thing is, what does it do so far from the star? There are two known ways to make a massive planet. One is what is called direct collapse, where it forms from the collapse of a part of a gas cloud, just as a star does. In fact, this can cause a star to distance itself (this is how binary stars form, for example), but the strangest thing is that it is difficult to do something so light. A planet formed in this way should be much more massive than YSES 2b.
It is called the other method nucleus accretion, where the small particles of a disk around the star stick together, become larger, and then become large enough to attract material through gravity. However, the disk surrounding a star is quite sparse as far as YSES 2b is, so in this case it is too massive to have formed that way.
The likely explanation is that, like most gas giants, it was formed by accreting the nucleus closest to the star where the disk is thickest, and then launched at the current distance after meeting. with another giant planet orbiting the star; the gravity of this planet could drive it away at this distance.
The problem is that no other planet like this is seen in the observations. It may be so close to the star that the glare makes it too hard to find. This seems likely to me, as we know things like this can happen, while the other two possibilities are less likely. Still, it would be nice to know for sure.
That’s why YSES 2b is an important catch. If the team finds more, they hope to see trends on the planets that will help them understand how planets form around Sun-like stars and how they form or reach such remote distances. While our own solar system may not have a planet like this (although we could), it helps us understand how our own system was also formed. There are still many things we do not know about the processes of planetary formation and every young planet that is found is a step forward in this knowledge.
*Many surveys usually name the objects they find after the survey in question. The star has a more formal name of 2MASS J11275535-6626046, which is easier to search in databases, but YSES 2 is good enough out there.