STScI: Young Planets Orbiting Red Dwarfs May Lack Ingredients for Life

[bystander]

Young Planets Orbiting Red Dwarfs May Lack Ingredients for Life
NASA | STScI | HubbleSite | 2019 Jan 08

Giant Blobs of Material Are Clearing Out Star's Disk

AU Microscopii ~ Image Credit: NASA, ESA, J. Wisniewski (University of Oklahoma), C. Grady (Eureka Scientific), and G. Schneider (Steward Observatory)

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Our Sun is not one of the most abundant types of star in our Milky Way galaxy. That award goes to red dwarfs, stars that are smaller and cooler than our Sun. In fact, red dwarfs presumably contain the bulk of our galaxy's planet population, which could number tens of billions of worlds. Surveys by NASA's Kepler Space Telescope and other observatories have shown that rocky planets are common around these diminutive stars. Some of these rocky worlds are orbiting within the habitable zones of several nearby red dwarfs. The temperate climates on such worlds could allow for oceans to exist on their surface, possibly nurturing life.

That's the good news. The bad news is that many of these rocky planets may not harbor water and organic material, the necessary ingredients for life as we know it. Earth, which formed as a "dry" planet, was seeded over hundreds of millions of years with icy material from comets and asteroids arriving from the outer solar system.

If the same life-nurturing process is needed for planets around red dwarfs, then they may be in trouble. Researchers using the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope (VLT) in Chile have discovered a rapidly eroding dust-and-gas disk encircling the young, nearby red dwarf star AU Microscopii (AU Mic). The disk is being excavated by fast-moving blobs of material, which are acting like a snowplow by pushing small particles — possibly containing water and other volatiles — out of the system. Astronomers don’t yet know how the blobs were launched. One theory is that powerful mass ejections from the turbulent star expelled them. Such energetic activity is common among young red dwarfs.

If the disk around AU Mic continues to dissipate at the current pace, it will be gone in about 1.5 million years, which is the blink of an eye in cosmic time. Smaller bodies, such as comets and asteroids, could be cleared out of the disk within that short time span. Planets, however, would be too massive to be displaced. Without enrichment from comet and asteroid material, the planets may end up dry, dusty, and lifeless.

Observations of Fast-Moving Features in the Debris Disk of AU Mic
on a Three-Year Timescale: Confirmation and New Discoveries ~ A. Boccaletti et al

• Astronomy & Astrophysics 614:A52 (Jun 2018) DOI: 10.1051/0004-6361/201732462
  arXiv.org > astro-ph > arXiv:1803.05354 > 14 Mar 2018

viewtopic.php?t=35246

[Ann]

I have never quite understood why planets orbiting red dwarf stars have been considered such ideal candidates for hosting life.

Yes, in the long run, when all massive and "semi-massive" stars have died many billion years from now, then red dwarfs will be the only stars still pumping out heat and light, and their planets will be the only planets that might still be habitable.

But for now the Universe is young. The entire Universe is only about three times older than the Sun and the Earth. There is no reason to think that all solar mass stars have already died and robbed their planets of the heat of their suns.

I get the impression that the reason why astronomers are spending so much time looking for planets orbiting red dwarfs is that these planets are the easiest ones to detect.

It's a bit like the old story of the man who was looking for his keys one night just below a street lamp. When asked if he had lost his keys under the street lamp, the man replied that he had actually lost them somewhere else, but that it was too dark to look for them where he had actually lost them.

Ann

[rstevenson]

It's a bit like the old story of the man who was looking for his keys one night just below a street lamp. When asked if he had lost his keys under the street lamp, the man replied that he had actually lost them somewhere else, but that it was too dark to look for them where he had actually lost them.

Ann

Sexism! I'm shocked! To be entirely politically correct, you'll have to update the story so it's about a sex-non-specific humanoid.

Rob-non-specific

[Ann]

It's a bit like the old story of the man who was looking for his keys one night just below a street lamp. When asked if he had lost his keys under the street lamp, the man replied that he had actually lost them somewhere else, but that it was too dark to look for them where he had actually lost them.

Ann

Sexism! I'm shocked! To be entirely politically correct, you'll have to update the story so it's about a sex-non-specific humanoid.

Rob-non-specific

Click to view full size image

Source: http://www.yzm.com.au/looking-for-custo ... lamp-post/

Okay!

A sex-non-specified humanoid was looking for its keys under a street lamp...

And if the humanoid in the picture looks like a male individual to you, bear in mind that it might a cross-dresser with a stocky build and a penchant for a tonsure-inspired coiffure.

Ann

[geckzilla]

[rstevenson]