Over 20 lightyears away,

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Over 20 light-years away, Earth-like planets?
Credit ESO
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Location R.A. 15h19m26s Dec -07d4320
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Image ca. 20 arc minutes wide. Credit DSS
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Credit ESO
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Credit ESO
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Orbits
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b
Earth masses 15.65 Distance 0.04AU Period 5.37
d Eccentricity 0
System Data
Star cataloged as Gliese 581
Constellation Libra Spectrum M3 Age vs
Sun nearly 2x Distance 20.4 ly Magnitude 10.6
mv Sun masses 0.31 Sun radii 0.38 Sun
luminosity 0.00202 Temperature 3,250oK Sun
magnitude 3.81 mv
Earth masses 5.36 Distance 0.07AU Period 12.93
d Eccentricity 0.17
c
d
Earth masses 7.09 Distance 0.22AU Period 66.8
d Eccentricity 0.38
e
Earth masses 1.94 Distance 0.03AU Period 3.15
d Eccentricity 0
1AU 149.598 mio km (93.5 mio miles)
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Is Life out there on c and d?

• Pros
• Super-Earth-class size
• Situated in Gliese 581s HZ
• Existence of liquid water possible
• Grainy or ocean covered surface

• Cons
• Radiation impact from the star
• Probably tidally locked

Credit ESO
Anyway The system is only 20.4 light-years
away and therefore a travel target for the future
by when our successors will know more about this
planetary system, which may count more than the
four planets known to date. Suppose it would be
possible to travel near the speed of light, the
journey would take about 6.1 years one-way at 1g
acceleration.
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Further information The Crowded Universe by
Alan Boss on Fora TV http//fora.tv/2009/03/13/Al
an_Boss_The_Crowded_Universe The Extrasolar
Planet Encyclopaedia http//exoplanet.eu Planet
quest http//planetquest.jpl.nasa.gov The
Kepler Mission http//kepler.nasa.gov