HEIC: "Distance" is Key to Preserving Primordial Discs

[bystander]

"Distance" From the Brightest Stars is Key to Preserving Primordial Discs
ESA Hubble Science Release | 2020 May 28

Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team

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The NASA/ESA Hubble Space Telescope was used to conduct a three-year study of the crowded, massive and young star cluster Westerlund 2. The research found that the material encircling stars near the cluster’s centre is mysteriously devoid of the large, dense clouds of dust that would be expected to become planets in a few million years. Their absence is caused by the cluster’s most massive and brightest stars that erode and disperse the discs of gas and dust of neighbouring stars. This is the first time that astronomers have analysed an extremely dense star cluster to study which environments are favourable to planet formation.

This time-domain study from 2016 to 2019 sought to investigate the properties of stars during their early evolutionary phases and to trace the evolution of their circumstellar environments. Such studies had previously been confined to the nearest, low-density, star-forming regions. Astronomers have now used the Hubble Space Telescope to extend this research to the centre of one of the few young massive clusters in the Milky Way, Westerlund 2, for the first time.

Astronomers have now found that planets have a tough time forming in this central region of the cluster. The observations also reveal that stars on the cluster’s periphery do have immense planet-forming dust clouds embedded in their discs. To explain why some stars in Westerlund 2 have a difficult time forming planets while others do not, researchers suggest this is largely due to location. The most massive and brightest stars in the cluster congregate in the core. Westerlund 2 contains at least 37 extremely massive stars, some weighing up to 100 solar masses. Their blistering ultraviolet radiation and hurricane-like stellar winds act like blowtorches and erode the discs around neighbouring stars, dispersing the giant dust clouds. ...

In Planet Formation, It's Location, Location, Location
NASA | GSFC | STScI | HubbleSite | 2020 May 28

[Ann]

Well, location, location, location.

Then again: There are precious few protoplanetary disks in the Milky Way that will be destroyed because they are situated right next to 37 extremely massive stars.

Ann

[BDanielMayfield]

Well, location, location, location.

Then again: There are precious few protoplanetary disks in the Milky Way that will be destroyed because they are situated right next to 37 extremely massive stars.

Ann

I wonder how this finding speaks to the average number of planets per star question. One might naturally think that it must lower it somewhat, but as Ann points out this is a rare situation with so many very high mass stars being formed in this cluster. Currently at least the great majority of newly forming star systems would be forming far from such turbulent regions, but in the deep past such very high mass star producing clusters would have been more common.

OTOH, ALL of those 37 extremely massive stars are destined to promptly (astronomically speaking) go Supernova, thereby enriching surrounding space with more planet building "starstuff". Therefore in the overall picture the existence of such very high mass clusters could actually enhance the production of planets. The volume of space that will eventually be affected by 37 expanding SN shock wavefronts will be vastly greater than the relatively small area of current planet building suppression.

Bruce, seeing the glass half full