The gas giant is in a place that could not have been formed by conventional means. It thus confirms what researchers have suspected for some time: Nature can make planets in different ways.
All planets are born in protoplanetary disks. These are disks of gas and dust around young stars. These disks of dust can spawn a variety of planets, from Earth-like worlds to giant gas giants. Researchers have ideas about how the last planets formed. For example, it is believed that most people see daylight through “primary accretion.” During this process, small objects in the protoplanetary disk — such as dust or pebbles — collide as they orbit their parent star and clump together. In this way, a planetary core is gradually created which – once it has enough mass – begins to draw gas from the same protoplanetary disk toward itself. The result is a gas giant: the core of a planet surrounded by a dense layer of gases.
Alternative method
It’s a straightforward story so far. But researchers have long suspected that not all gas giants arise in the same way. In theory, the gas giants could also see daylight in a more surprising way. This happens when the protoplanetary disk cools and, under the influence of gravity, disintegrates into one or more parts, which subsequently – much faster than the method described above – evolve into protoplanets similar to Jupiter. However, there was no evidence of this alternative method of formation for a long time. But the Hubble Space Telescope now appears to be changing that.
AB Aurigae B
The telescope discovered a planet that couldn’t actually form in the traditional way—by holding small molecules together and later accumulating gases. It is about the protoplanet AB Aurigae b which is still in the protoplanetary disk around its very young (only 2 million years old) parent star. The planet is about 9 times larger than Jupiter, and most importantly, it is 13 billion km away from its parent star. This means that the distance between the planet and its parent star is more than twice the distance between Pluto and our sun!
According to the researchers, the presence of a gas giant orbiting such a large distance from the star is significant. Because at such a large distance from the parent star, it would take a very long time – if possible – for a gas giant to form in the traditional way. “Nuclear accretion requires different masses of solid matter to clump together over a period of time (several million years),” said study researcher Thayne Currie. Scientias. nl† And at a greater distance from the parent star, all this simply does not happen fast enough. “Because the orbital period is longer and there are usually less solids available at such a large distance, for example, at the distance between Jupiter and the Sun. To put it very simply, the planetary core growing at a very large distance from the parent star has little food and eats Also at a slower rate.” The fact that a large gas giant can still be found around AB Aurigae – only 2 million years after the formation of this star and at a great distance from this star, strongly suggests that it could evolve in a different and much faster way. appeared to exist. “This new discovery is strong evidence that some gas giants can form because the protoplanetary disk is unstable,” said researcher Alan Boss.
Archival and recent images reveal the anticlockwise motion of the protoplanet orbiting the parent star. Images: Thane Currie (Subaru Telescope, Eureka Scientific), Alyssa Pagan (STScI).
Incidentally, the large distance between the parent star and the protoplanet is not the only indication that the planet formed in this protoplanetary disk in an unorthodox way. “The disk with the planet also has several spiral arms,” Currie said. This is something researchers expect to see when planets emerge due to instability in the protoplanetary disk. In fact, the AB Aurigae system is very similar to what we see in computer simulations when we simulate planet formation due to protoplanetary disk instability. The similarities are striking.”
Notes
Researchers build their conclusions – published in the journal natural astronomy – Not only on the Hubble notes. They also used observations from the Subaru telescope for the study. Curie points out that “interpreting this system is very challenging.” This of course has everything to do with the fact that AB Aurigae b is still hidden in the protoplanetary disk. “That’s one of the reasons we needed Hubble for this project,” Corey said. “(We, editor) wanted to be able to separate the light from the disk from the light from the planet.” Hubble was also instrumental in determining the protoplanet’s orbit; The telescope has been around for a while, and so there have been quite a few archival photos showing the planet (in hindsight). These images – along with archival footage from Subaru – eventually allowed the researchers to see the planet orbiting the star and confirm its existence.
Corey concludes that “nature is intelligent.” “This can shape planets in different ways.” Now that compelling evidence for this has been found, the question naturally arises as to whether there are no more gas giants formed in this unconventional way waiting to be discovered and whether this unconventional planet formation is truly unconventional. We asked Curie, and he certainly expects nuclear accretion to be the primary way gas giants emerge, so collapsing protoplanetary disks will still be somewhat unconventional. “To have such an unstable disk, it must firstly be very heavy and secondly very efficiently cool. However, a few protoplanetary disks are as massive as AB Aurigae disks. In addition, the rapid cooling criterion indicates that the instability in a disk Protoplanets happen more quickly at a great distance from the star (50 to 100 times the distance between the Earth and the Sun). We now know that a large percentage of stars possess gas giants, but only a small percentage of those stars possess gas giants at 50 to 100 AU.” . However, Currie predicts that there will be unconventionally formed gas giants still waiting to be discovered. However, in comparison with the gas giants created by nuclear accretion, it is expected that their number will remain much greater.
