Red Dwarfs Have Teeny Tiny Habitable Zones

by Fraser Cain on January 11, 2008

Artist illustration of a red dwarf
As space telescopes get larger and more sensitive, the search for Earth-sized worlds surrounding other stars is about to get rolling. But astronomers are going to need to know where to look. A team of researchers are working on a survey of nearby stars, calculating the habitable zones around them. When the search begins, astronomers are going to want to study these regions.

The Research Consortium on Nearby Stars (RECONS) is a survey using relatively small telescopes to study the habitable zones in the nearby stars. The team uses measurements of various stars brightnesses at optical and infrared wavelengths matched with their distances to get a sense of the stars’ habitability.

After gathering together a big list of potential candidate stars, the researchers can then categorize stars by size and temperature to find ones that might harbour life.

“Once we have good values for the temperatures and sizes of the nearby stars, we can estimate how hot planets will be at different distances from the stars,” explains Justin Cantrell, a Doctoral Candidate in Astronomy at Georgia State University. “We consider those stars that would have surface temperatures suitable for liquid water to be in the traditional habitable zone.”

The researchers were looking for habitable zones around red dwarf stars, which can be 50-90% smaller than the Sun and much cooler. The comprise 70% of the stars in the Milky Way, but they’re harder to spot because they put out less light.

They were surprised to learn that these red dwarf stars have tiny habitable zones. When they added up the habitable zones of 44 red dwarf stars nearby the Sun, they found they didn’t add up to equal the habitable zone of a single Sun like star.

So even though these red dwarfs are common, they’re not great candidates for life. Earth-type stars would need to be perfectly positioned in their tiny habitable zones to be good candidates for life.

Original Source: Georgia State University News Release


Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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