Webb telescope shows end of planet formation

The James Webb Space Telescope (JWST) has for the first time captured winds from an old planet-forming disk that is actively expanding its gas content.

According to a team of scientists led by Naman Bajaj of the University of Arizona, published in the Astronomical Journal, it is important to know when the gas expands, because it limits the time left for newborn planets to consume the gas in their atmospheres. . Dr. Uma Gorti of the SETI Institute,

At the center of this discovery is the observation of TCha, a young star (relative to the Sun) surrounded by a decaying disk notable for its enormous dust spot, approximately 30 astronomical units in radius.

For the first time, astronomers have imaged scattered gas (also called winds) using four lines of the noble gases neon (Ne) and argon (Ar), one of which is the first identified in a planet’s forming disk.

(Ne II) The images show that the wind comes from an extended region of the disk.

“These winds may be driven by high-energy stellar photons (light from the star) or by the magnetic fields weaving the planet-forming disk,” Naman said in a statement.

It appears that planetary systems like our Solar System contain more rocky objects than gaseous objects.

Around our Sun, they include the inner planets, the asteroid belt, and the Kuiper Belt.

But scientists have long known that planet-forming disks start out with up to 100 times more mass in gas than in solids, raising an important question: When and how does most of the gas leave the disk/system?

During the early stages of planetary system formation, planets coalesce into a rotating disk of small gas and dust around the young star.

These particles stick together and form larger and larger pieces called planetesimals. Over time, these planetesimals collide and stick together, eventually forming planets.

The type, size, and location of the planets depend on the amount of material available and how long it remains in the disk.

Thus, the outcome of planet formation depends on the growth and expansion of the disk.

In another paper the same group, led by Dr. Andrew Selleck of Leiden Observatory, simulated stellar photon-driven scattering to distinguish between the two.

They compare these simulations with actual observations and find that scattering by high-energy stellar photons can explain the observations and therefore cannot be ruled out as a possibility.

Selleck described how “the simultaneous measurement of all four lines of the JWST was important in constraining the properties of the wind and helped us demonstrate that a significant amount of gas is scattered.”

To put this in context, researchers have calculated that the mass dispersed each year is equivalent to that of the Moon.

A companion paper, currently under review in the Astronomical Journal, will detail these results.

The (Ne II) line was first detected toward several planet-forming disks with the Spitzer Space Telescope in 2007 and was soon identified as a wind tracer by the project leader, Professor Pascucci of the University of Arizona; This changed research efforts to focus on understanding gas dispersion in the disk.

The spatially resolved discovery of (Ne II) and the first identification of (Ar III) using the JWST could become the next step toward transforming our understanding of this process.