[▲ Imaginary drawing of the rolled up dust falling on the outer edge of the protoplanetary disk (Credit: Kagoshima University)]
Kagoshima UniversityAssistant Professor Yusuke TsukamotoThe research group led by the group was made of gas and dust surrounding a newborn young star.“Protoplanetary disk”ofMechanism of dust growth at the outer edgeWe announced the research results that were close to.According to the research group, it has been thought that it is difficult for dust to grow and form a planet at the outer edge of the protoplanetary disk, but this result isPossibility of planet formation even at the outer edge of the protoplanetary diskIs said to suggest.
■ Possibility of dust accumulating on the outer edge of the protoplanetary disk by a mechanism similar to volcanic ash fall
More than 4,500 have been found outside the solar system, including Earth and Jupiter.planetSurrounds the newborn star (protostar, central star)Formed within a protoplanetary diskIs believed to be.A lot of small dust is united in the diskPlanetesimalIs formed, and planetesimals repeatedly collide with each other.ProtoplanetIs expected to grow to.
Gas and dust in the protoplanetary disk revolve around protostars, but according to the research group,Dust grown in the diskActs like a headwindHow gas worksThe revolution movement is interrupted byRapidly falling towards the protostar(The fall of the central star of dust) is theoretically expected.Due to this phenomenon, it is tens of astronomical unitsaway from the protostar.The outer edge of the protoplanetary diskThen,It ’s very difficult for dust to grow and planets to form.
It is said that it has been considered.
*… 1 astronomical unit (au) = approx. 150 million km, derived from the average distance from the earth to the sun
[▲ The ring structure of the protoplanetary disk surrounding the “GW Orionis” observed by the ALMA telescope. The radius of the outermost ring is 338 astronomical units (Credit: ALMA (ESO / NAOJ / NRAO), Bi et al., NRAO / AUI / NSF, S. Dagnello)]However, in recent years, Chilean radio telescopes“ALMA”From the observation of the protoplanetary disk bySigns of large dust growth on the outer edge of the diskIs confirmed,A disc gap that may indicate the existence of a planet at a distance of tens of astronomical units from a protostar
Has been discovered. The theoretical mechanisms that can explain the growth of dust and the formation of planets in places that are expected to be theoretically difficult have been mysterious.This time, the research groupThree-dimensional magnetohydrodynamic simulation considering the motion of both gas and growing dust inside the protoplanetary diskThe National Astronomical Observatory of JapanAstronomy-only supercomputer “Aterui II”It was carried out using. According to the research group and the National Astronomical Observatory of Japan, this simulation is the first attempt in the world.As a result of the simulation, the research groupA new mechanism by which dust grows without falling on protostars
Annotated version of the opening figure. Refer to the text for each step 1 to 4 (Credit: Kagoshima University)
[▲ Annotated figure at the beginning. Refer to the text for each step 1 to 4 (Credit: Kagoshima University)]The mechanism discovered by the research group this time is as follows (the numbers correspond to the above figure).The dust that grows in the disk is due to the action of gas.Move towards the central protostar(1).The dust that reaches near the protostar is the gas that erupts in the vertical direction of the disk.OutflowBy (gas flow)Winding up(2).The dust that was rolled upCentrifugal forceFrom outflow bySeparate(3) Eventually, of the protoplanetary diskIt piles up on the outer edge
（4）。A mixture of gas and ash released as eruption from a volcano separates in the atmosphere, and only ash accumulates on the surface of the earth.“Ash fall”As this mechanism is similar, the research group described this phenomenon.“Phenomenon of ash fall in the sky”I call it. According to the research group, the resistance received from gas is smaller at the outer edge of the low-density protoplanetary disk.The accumulated dust can grow large and lead to the formation of planets.
The simulated gas (left) and dust (right) are flowing. The orange and red lines indicate the path of gas and dust, the white arrow indicates the direction of gas and dust flow, and the yellow indicates the protoplanetary disk formed in the simulation (Credit: Yusuke Tsukamoto).
[▲ The simulated gas (left) and dust (right) are flowing. The orange and red lines indicate the path of gas and dust, the white arrow indicates the direction of gas and dust flow, and the yellow indicates the protoplanetary disk formed in the simulation (Credit: Yusuke Tsukamoto)].Mr. Tsukamoto who performed the simulation actuallySakurajima eruption
It is said that he got the idea of research while looking at. According to Mr. Tsukamoto, in the “ash fall phenomenon in the sky”, dust equivalent to about 10% of the earth’s mass accumulates in one year. “The ash that has fallen on the disk in this way may have become a planet like the earth we live in, and even a source of life like us.” (Mr. Tsukamoto)The research group will carry out further simulations in the future.Elucidation of dust movement and size distributionI discovered this time through the observation of the ALMA telescope.Verification of “ash fall model”
Is supposed to do.
Related: The ring structure of the protoplanetary disk may show the history of planetary migration, analyzed by the supercomputer of the National Astronomical Observatory of Japan.
Image Credit: Kagoshima University
Source: Kagoshima University / National Astronomical Observatory of Japan
Sentence / Takehiro Matsumura
