"Life on Planets of Red Dwarf Stars May Be More Evolved than on Earth"
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December 07, 2013

"Life on Planets of Red Dwarf Stars May Be More Evolved than on Earth"



“We thought we would have to search vast distances to find an Earth-like planet. Now we realize another Earth is probably in our own backyard, waiting to be spotted,” said Courtney Dressing of the Harvard-Smithsonian Center for Astrophysics (CfA). Since red dwarf stars live much longer than Sun-like stars, this raises the interesting possibility that life on such a planet would be much older and more evolved than life on Earth.

Six percent of red-dwarf stars have habitable, Earth-sized planets, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have found. Red dwarfs are the most common stars in our galaxy; about 75 percent of the closest stars are red dwarfs. The closest Earth-like planet could be just 13 light-years away, Harvard astronomer Courtney Dressing has calculated.

Red dwarf stars are smaller, cooler, and fainter than our Sun. An average red dwarf is only one-third as large and one-thousandth as bright as the Sun. The cFa team culled the Kepler catalog of 158,000 target stars to identify all the red dwarfs, then re-analyzed those stars to calculate more accurate sizes and temperatures. They found that almost all of those stars were smaller and cooler than previously thought.

Locating nearby Earth-like worlds may require a dedicated small space telescope, or a large network of ground-based telescopes. Follow-up studies with instruments like the Giant Magellan Telescope and James Webb Space Telescope could tell us whether any warm, transiting planets have an atmosphere and further probe its chemistry.

Courtney D. Dressing, David Charbonneau, The occurrence rate of small planets around small stars, The Astrophysical Journal, 2013, in press

Daily Galaxy via Harvard-Smithsonian Center for Astrophysics

Image credit: http://us-of-alaska.deviantart.com/art/Red-Dwarf-with-Planet-and-Moon-131323840


I was under the impression that Brown Dwarfs are the most common type of stars in our Galaxy. Anyway, how can a planet be still in a habitable zone after surviving a star's Red Giant phase? This seems to be odd, isn't it?

Exactly. And Red Dwarf stars have low mass, which means the habitable zone is much closer than in our case, which also means that planets are tidally locked. And that means no day/night cycle, only half the planet is probably habitable at best...

All these used to be real questions about a year ago, but now everyone seems to have forgotten about them. I mean sure, the prospects are amazing, but some real issues remain, whether we like them or not.

Brown dwarfs aren't stars in the sense of something that would be bright enough to light and warm a planet. They're more akin to enormous gas giants that came close to becoming stars, but never accreted quite enough mass to do the job, and never actually ignited into what we commonly think of as stars.

And not every star goes through a phase of being a red giant, either.

Red dwarf stars are low mass, stay on the Main Sequence for hundreds of billions of years and are by far the most abundant stars. Red giant stars are stars that are near the end of their lives: they have nearly run out of their hydrogen fuel reserves and have started to fuse helium or heavier elements for a comparatively very brief time compared to their hydrogen-burning phase. They are relatively rare because the red giant phase doesn't last long. Most of them eventually blow off their outer envelope to leave white dwarf stars behind, which are abundant because many stars have run out of fuel over the last 13.7 billion-year age of the universe so far. If they are sufficiently massive, stars may briefly swell to even more rare red supergiants, or bypass the red supergiant phase entirely before blowing apart catastrophically in core-collapse supernova explosions, leaving behind a neutron stars (or pulsars) or stellar-mass black holes, both very rare compared to other stellar objects. Brown dwarfs are not massive enough to initiate hydrogen fusion in their cores, so they are technically not stars at all, but a kind of intermediate object with a mass between gas giant planet and star-hood. They may be as or very much more plentiful than red dwarf stars, but their role in the prevalence of life in the universe seems unlikely.

With the small amount of knowledge one can assume great wisdom.

What about a satellite of a Jupiter like planet orbiting in the star's goldi lock zone. The satellite will be tidally locked to star but satellite will experience day & night cycle (may be of longer duration.

And just what does "More evolved" mean?

Fascinating. There's another reason life may be more evolved near red dwarfs: they often flare which would stress their planetary systems. In early stages this could stimulate life to develop due to more crisis events. Later on, any civilizations would have more pressing incentive to develop protective technology. Finally, interstellar travel would be a bit easier from the shallower gravity well around the star.

"Fine minds make fine distinctions."

Red dwarfs do not end their age of brightness in an explosion; They simply cool off to a brown or white dwarf.

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