Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones

Details Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones

Oct 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005asbio...5..587g&link_type=abstract

Astrobiology, Volume 5, Issue 5, pp. 587-603.

Biology

47

Cosmic Rays, Magnetospheres, Terrestrial Exoplanets, Habitability, Low Mass Stars

Scientific paper

Because of their different origins, cosmic rays can be subdivided into galactic cosmic rays and solar/stellar cosmic rays. The flux of cosmic rays to planetary surfaces is mainly determined by two planetary parameters: the atmospheric density and the strength of the internal magnetic moment. If a planet exhibits an extended magnetosphere, its surface will be protected from high-energy cosmic ray particles. We show that close-in extrasolar planets in the habitable zone of M stars are synchronously rotating with their host star because of the tidal interaction. For gravitationally locked planets the rotation period is equal to the orbital period, which is much longer than the rotation period expected for planets not subject to tidal locking. This results in a relatively small magnetic moment. We found that an Earth-like extrasolar planet, tidally locked in an orbit of 0.2 AU around an M star of 0.5 solar masses, has a rotation rate of 2% of that of the Earth. This results in a magnetic moment of less than 15% of the Earth's current magnetic moment. Therefore, close-in extrasolar planets seem not to be protected by extended Earth-like magnetospheres, and cosmic rays can reach almost the whole surface area of the upper atmosphere. Primary cosmic ray particles that interact with the atmosphere generate secondary energetic particles, a so-called cosmic ray shower. Some of the secondary particles can reach the surface of terrestrial planets when the surface pressure of the atmosphere is on the order of 1 bar or less. We propose that, depending on atmospheric pressure, biological systems on the surface of Earth-like extrasolar planets at close-in orbital distances can be strongly influenced by secondary cosmic rays.

Affiliated with

Also associated with

No associations

Rating

Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1620628