It could be argued that one of the most confusing aspects of our solar system is the fact that not every planet is a nice, solid rock like Earth. Some are literally made almost entirely of gas. You can’t exactly “stop” anywhere on Jupiter unless you can squeeze through layers of gas and survive unreal amounts of pressure before heading towards the potentially rocky core of the orange-striped world. This doesn’t seem ideal.
Even science fiction video game creators sometimes have trouble depicting what it would be like to wander through one of these worlds. First thing I tried to do after gaining some free reign in Xbox gaming Star Field I was landing my ship in a simulated location Neptune, just to see what happens. The game did not allow this. It goes without saying that the mystery of giant gas spheres is also quite intriguing for scientists. And now they have James Webb Space TelescopeThey have incredibly powerful infrared eyes, they put the spacecraft on the chassis.
Just last week, a team announced that they might get some updates on the dynamics of gas giant formation thanks to JWST. More specifically, researchers say they are beginning to make progress in answering the question of how long gas giants must form around their host stars before all the gas around the stars is quenched.
The short answer is; It’s not very long, but the whole story is much more nuanced.
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The team used JWST to investigate what is (somewhat confusingly) known as the “disk wind.” This doesn’t actually indicate the wind as you might imagine. Rather, it refers to the process of gas separating from a disk around a star. This “disk” would be a disk filled with different types of materials that have the potential to lead to the formation of planets. For this reason it is otherwise known as the “protoplanetary disk”.
“We knew they existed and that they could play an important role in disk evolution,” Naman Bajaj, lead author of the new disk wind analysis and a scientist at the University of Arizona Lunar and Planetary Science Laboratory, told Space.com. “What we didn’t know was the underlying physics and how much mass was lost as a result. These are key to answering all our questions about the impact.”
Strictly speaking, such a disk would also contain non-gaseous debris, such as dust, which could coalesce over time to form rocky planets. In fact, it is believed that the Earth was once formed this way.
“I suspect it’s just because of its ‘slow’ speed in name,” Bajaj said. The disk wind studied by the team appears to move at around 10 to 15 kilometers (6 to 9 miles) per second. Fast-moving gas patterns, on the other hand, are typically called “jets.” These can have speeds of over 100 kilometers (62 miles) per second.
Although Bajaj and other researchers have not arrived at a final, definitively confirmed answer as to how long it might take for gas planets to form before the gas in the protoplanetary disk is completely exhausted, they have suggested a playing field based on their calculations. “Given the mass of gas in this disk, and assuming the gas will continue to separate at this constant rate we found (about one lunar mass per year), it will take about 100,000 years,” he predicts.
Yep, that seems like a long (long) time. But as Bajaj emphasizes, this is an incredibly short period of time in astronomical terms: “A protoplanetary disk lives for about five to 10 million years!”
How to find a space disk?
The first step in combating puck wind motion is to find the puck wind issue. And to find the disk wind issue, of course you need to find a proto-planetary disk.
Our solar system wouldn’t work for this kind of analysis because all our planets, including gaseous ones, are complete. So the team’s disk wind target became a target associated with the disk around a young, low-mass star called T Cha. Honestly, this is a very interesting star in its own right. Shining body lying around 350 light years It is known that there is a large dust gap in the disk coming from the Earth. This dust gap is exactly what it sounds like.
“These cavities are thought to be created by planets that consume all material in their path as they orbit the star,” Bajaj said.
Therefore, such a gap indicates that there are indeed budding planets around the star. And These newly formed worlds are old enough to eat up part of the disk. “We also call this the transition phase,” Bajaj said. “There is a transition from a protoplanetary disk to a more solar system-like structure.” Additionally, Bajaj explains, previous ground-based observations suggest there is neon in the disk, indicating how disk gas slowly escapes outwards. More on this in a moment.
So we had the perfect disc subject on our hands. The next step was to start making some observations to see what was going on around T Cha.
It was time to watch some neon.
fizzy nobility
Neon is a noble gas, a category of elements represented by atoms with completely filled outer electron shells or valence shells. Simply because of the valence shell property, these gases are very unreactive. However, it is still possible for them to lose one of the outer electrons when exposed to a high enough temperature. If this were the case, the gas would be “ionized” or electrically charged.
Since electrons have a negative charge, losing one makes the previously neutral atom slightly more positive. Gaining an extra electron will similarly make a previously neutral atom slightly more negative. But most importantly for astronomers, when such ionization occurs anywhere in the universe, it leaves behind a signature that can be tracked by their equipment. This includes the James Webb Space Telescope.
And as Bajaj explains, the Neon’s signature is specifically for disc wind tracking.
First, some gases are more likely to be found in protoplanetary disks. Light neon is one of them. “The abundance of the heavier noble gases is very low, so we cannot see them,” Bajaj explained.
Second, ionization occurs differently for different elements. Sometimes it takes a really high temperature to knock an electron out of an atom; other times electrons come out more willingly and do so at lower temperatures.
“Helium, which is more abundant than all these [noble gases]It has a much higher temperature requirement to ionize, Bajaj said.
Neon, on the other hand, will spit out an electron under more modest temperature requirements; so the team specifically looked for neon emission lines to see how gas evolved within the T Cha protoplanetary disk. In short, they found two.
“When we saw the spectrum for the first time – during my first week of graduate school – we saw both neon lines bursting!” Bajaj added that one of these lines has never been seen around T Cha before. “We realized that the neon was coming from further away from the star by looking at it with JWST.”
“I spent months trying to figure out if we could see the neon emission structure from the images; it was very difficult,” Bajaj said. He explained that it took about eight months to confirm from JWST images that the structure was indeed there.
But that’s not all. There was a surprise.
Bajaj said that along with the neon lines, the team also found a very strong argon line. An argon line like this has been seen in a few protoplanetary disks before, but none appeared this strong.
then there was another surprise.
“We always thought we had two neon emission lines and one argon emission line, but one fine day I was examining the spectrum and realized we had another argon line,” Bajaj said. “This one was much weaker than the others, so we missed it for a long time.”
“We realized that this was the first time we had seen this line in any proto-planetary disk!” added. “Some of the senior researchers thought it would never be possible to do this, but with more rigorous testing over several months we confirmed that we did.”
Where do we go from here?
An important point Bajaj reiterated was that the team’s new result is really a small, albeit crucial, step in the grand march to learn more about the inconceivable nature of gas planets. Where do these strange gas globules come from? Their architecture seems very difficult to deal with.
The new study not only strengthens many of the previous observations in this field (some of which Directed by Bajaj’s co-writers, actually) but it also opens the door to fascinating future work. For example, study co-author Andrew Sellek, a postdoctoral researcher at Leiden University in the Netherlands, put together these disk wind details along with a subsequent paper outlining simulations that suggest the disk wind process is driven by something else. It is called photoevaporation.
At the risk of oversimplifying, photoevaporation in this case refers to energy from a star that heats gas in the disk around it, which then forces that gas to disperse into space. “Just like water evaporates on Earth,” Bajaj said. Sellek’s paper was recently accepted for publication in The Astronomical Journal; You can view the preprint here.
OK, I might be thinking a bit at this point, but I can’t help but think how satisfying the subject is after delving this deep into the dynamics of disc wind. It’s like the pieces are falling into place.
For example, because of the way gas exits the protoplanetary disk, it is true that only rocky planets can form when the gas is gone. It is also true that gas worlds, and especially gas giants, are more likely to arise in the outer regions of a planetary system. There is a tendency for more general mass in the outer regions of the protoplanetary disk, leading to the formation of larger planets as a whole, including Jupiter-like gas giants. In addition, the presenter stars also have a say in this matter.
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“Rocky planets very close to the star will have little or no atmosphere [like Mercury]”It is similar to photoevaporation due to being stripped by the sun’s high-energy photons,” Bajaj said. “For gas giants, if they form close to the star, it is possible for them to find a balance between their own gas and solar energy.”
And finally, although it’s incredibly cliché to say this at this point, this is all a testament to how much the James Webb Space Telescope has revolutionized our understanding of the universe. Its infrared sensitivity is huge, of course, but much of its discovery is owed to existing work that can already be built upon—the library of papers that help scientists decide exactly where JWST should look.
“We truly stand on the shoulders of giants and giant telescopes,” Bajaj said.
The study was published March 4 in The Astronomical Journal.