Quote:
Modelling of planet Gliese 581d shows it has the potential to be warm and wet enough to nurture Earth-like life, scientists have said. It orbits a red dwarf star called Gliese 581, located around 20 light years from Earth ... Gliese 581d orbits on the outer fringes of the star's 'Goldilocks zone', where it is not so hot that water boils away, nor so cold that water is perpetually frozen. Instead, the temperature is just right for water to exist in liquid form.
This planet
might be on the cool side, perhaps similar to the British Isles or Scandinavia.
HOWEVER, this requires that the world be a "Class M" world - so much like Earth that only the surface geography might be arranged differently. The size, atmosphere composition and pressure, and hydrographic percentage of the world must be taken into account. Volcanism is also an important factor, as are the effects of one or more moons on the oceans' tides. Since we know none of these factors, we can only assume that conditions
might be hospitable for human life.
The following is from an article by Thomas H. Maugh II - April 22, 2009
Quote:
"Two planets identified as most similar to Earth - both orbit the same star, 20 light-years from Earth, called Gliese 581. The larger of the two orbits in the 'habitable zone,' and could have oceans.
After locating more than 340 planets orbiting other stars, astronomers have identified two that are the most similar to Earth so far.
The most recently discovered one is almost twice as large as Earth, making it the smallest exoplanet -- for extra-solar planet -- found to date. The second one was found in 2007, but new observations have shown that it is the only exoplanet to date that orbits its star in the so-called habitable zone, where water remains a liquid. Thus, it is the only exoplanet discovered that is likely to have oceans.
Intriguingly, both orbit the same star, a dwarf 20 light-years from Earth called Gliese 581...",
(Commentary omitted from article)
Quote:
"The small planet is the fourth discovered circling Gliese 581 by a team of astronomers working with the European Southern Observatory's 3.6-meter telescope at La Silla, Chile. They identified the planets by detecting and analyzing slight wobbles in the star's path as the planets orbit it.
The small planet, called Gliese 581e, has an estimated mass equal to 1.9 Earths and orbits its sun every 3.15 days, the team reported at an astronomical meeting at the University of Hertfordshire in Britain. Because it is so close to Gliese 581, it is blisteringly hot, and any gases or liquids that it might have carried have long since dissipated, leaving only uninhabitable rock."
(Omitted text referring to another system)
Quote:
"The other three planets in the Gliese system have masses of 16, five and seven Earths. The one with a mass of seven Earths, called Gliese 581d, was initially thought to have an orbital period of 80 days, which would put it just on the outer edge of the habitable zone.
Recent refinements of the data, however, show that it has an orbit of only 66.8 days, which places it well within the habitable zone, astronomer Stephane Udry of Geneva University told the meeting. Because of its distance from Gliese 581, moreover, it must have a significant amount of water and other gases, he added. It could have oceans thousands of meters deep, he said."
(Omitted blah-blah text to end of article)
Some of the characteristics of Gliese 581 are:
Spectral type: M3 (A small red dwarf)
Luminosity Class: V (Main Sequence)
Temperature 3,480 ± 48 degrees Kelvin
Distance: 20.3 ± 0.3 light-years (6.2 ± 0.1 parsecs)
Absolute magnitude (MV): 11.6
Mass: ~0.31?
Radius: ~0.29?
Age 7 to 11 × 109[9] years
Gliese 581 has a very low UV index, meaning that it might not support photosynthesis, thus no chlorophyll-based plant life may exist on Gliese 581d no matter how hospitable it may be to human life. Plant-based foods might have to be imported to support any human colonies.
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17 May 2011, 5:53 pm
