To date, astronomers have found more than 4,000 exoplanets – extraterrestrial planets orbiting other stars.
There are a variety of ways to find them, most using indirect methods, but one of the coolest is pretty straightforward: getting real images of the planets next to the host stars. Called direct imaging, this technique has been used to find dozens of planets.
A team of astronomers has targeted 70 nearby stars to search for such exoplanets and have just announced a new one: YSES 2b, a huge planet orbiting a star just 360 light-years away.
We have seen some similar ones, but in this case, this planet is special. First, it orbits a star that will one day be very similar to the Sun. For another, it orbits at least 16.5 billion kilometers of the star, 110 times farther from its star like the Earth of the Sun!
This is a very, very long road and what it does so far is a mystery.
The direct image works best to find very young planets, up to several tens of millions of years old. The formation of the planet is a violent, 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 secondary advantage that stars are usually weaker in IR than in visible light, making it easier to see any planet.
Astronomers who discovered this new planet conducted a survey called the Young Suns Exoplanet Survey, or YSES, and looked at a nearby group of young stars called the lower Centaurus Crux subgroup, part of a much larger group of stars called the Scorpius association. -Centaurus. These stars are very young, about 14 million years old (the Sun is 4.6 billion years old, for comparison, so these stars are babies) and are only 350 light-years away, close enough for an exoplanet to it can be separated from its star enough to see in the pictures.
We know that stars more massive than the Sun tend to have more massive planets, so to avoid any bias like the survey, look only at stars with masses similar to the Sun. They target 70 such stars in the group.
DA 2* is the second star they looked at where they found a planet (they observed about 45 others, but are still working to find planets around them). It has a mass 1.1 times that of the Sun, so it is very similar, although it is colder at this time (over time, it will probably heat up once it settles and becomes stable). I’m about 360 light-years away.
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 take many years for it to move visibly). To confirm that an exoplanet is a companion to a host star, the team takes pictures of each star a year apart. The stars are all moving as they orbit the center of the galaxy, and the targeted stars are close enough to Earth to make this motion look great (like when you’re in a car and the trees pass by while a distant mountain barely seems to move). to all). If the candidate planet is truly a companion, it will move with the star. If it’s a backdrop, it won’t.
Images taken a year later show that the object is really moving with the star, so it is a companion. Using physical models of how planets cool after formation, he discovers that it has a mass somewhere between 5 and 8 times greater than that of Jupiter, with a very probable mass of about 6 Jupiters, which makes it a real planet. They called it YSES 2b.
The thing is, what does it do so far from the star? There are two known ways to create 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 do something at a distance from a star (how binary stars form, for example), but the strange thing is that it’s hard to do something so easy. A planet that forms in this way should be much more massive than YSES 2b.
The other method is called basic accumulation, where small particles in a disk around the star stick together, grow and then become large enough to attract the material by gravity. However, the disk around a star is quite weak as far as YSES 2b is, so in this case it is too massive to have formed this way.
The probable explanation is then that, like most gas giants, it formed by accumulating nuclei closer to the star where the disk is thickest and then thrown at the current distance after encountering another giant planet orbiting the star; the planet’s gravity could take it out at that distance.
The problem is that no other planet of this kind is seen in observations. It may be so close to the star that the brightness makes it too hard to find. This seems probable to me, because we know that such things can happen, while the other two possibilities are less likely. However, it would be nice to know for sure.
That is why YSES 2b is an important catch. If the team finds more, they hope to see trends on planets that will help them understand how planets form around Sun-like stars and how some form or reach such distant distances. Although our own solar system may not have a planet like this (although we could), it helps us understand how our own system was formed. There are still many things we do not know about the processes of planetary formation, and every young planet found is a step toward advancing this knowledge.
*A lot of surveys tend to name the objects they find after the survey in question. The star has a more formal name than 2MASS J11275535-6626046, which is easier to search in databases, but YSES 2 is good enough for here.