Science
Related: About this forumStar is crowded by super-Earths
This means its habitable zone can be much closer in before temperatures make liquid water impossible. The team is now confident that three rocky worlds occupy this region at Gilese 667C.
"Their estimated masses range from 2.7 to 3.8 that of the Earth's," Mikko Tuomi told BBC News.
...
"There might, in fact, be more habitable-zone planets in the Universe than there are stars, which makes it much easier for the future space missions to obtain images of these planets.
http://www.bbc.co.uk/news/science-environment-23032467
lumberjack_jeff
(33,224 posts)muriel_volestrangler
(101,403 posts)With the star smaller than the Sun, and the planet being considerably bigger than Mercury, I'd think it wouldn't be 100%. The presence of the other 2 planets close by could also complicate it. And I don't know if anyone would be able to work out the ratio of rotation to orbital period - Mercury's is 3 rotations to 2 orbits, but is that predictable?
lumberjack_jeff
(33,224 posts)muriel_volestrangler
(101,403 posts)Mercury possesses the most eccentric orbit of any planet except Pluto. At its farthest distance from the Sun (aphelion), it lies about 43 million miles (69 million kilometers) away. But when it arrives at its closest point to the Sun (perihelion) it's just under 29 million miles (47 million kilometers) away. So its orbital speed is appreciably greater at perihelion.
Mercury rotates on its axis three times for every two revolutions it makes around the Sun. But when it arrives at perihelion (as it will on September 13) Mercury's orbital velocity will exceed its rotational speed. As a consequence, a hypothetical observer standing on Mercury would see a sight unique in our entire solar system. Over the course of eight days (fours days before perihelion to four days after perihelion), the Sun would appear to reverse its course across the sky, then double back and resume its normal track across the sky.
If our observer were located on that part of Mercury where the Sun were to rise around the time of perihelion, the Sun would appear to partially come up above the eastern horizon, pause and then drop back below the horizon, followed in rapid succession by a second sunrise!
http://www.space.com/268-elusive-mercury-sunrise.html
longship
(40,416 posts)IIRC, it offers opposite sides to the sun every revolution. That would make for interesting weather patterns.
R&K
DreamGypsy
(2,252 posts)There's nothing particularly special about a 24 hour day.
From the article:
I don't know whether HARPS can determine the rotational periods of exoplanets in general, or at all. Depending on the rotation, they could have interesting cycles, just as you point out for Mercury (from Wikipedia):
My personal speculation is that long days and nights is not a major variable in the conditions for life. I expect there are much greater possible chemical, physical, and biological variations that constitute 'life' than we short-sighted humans can begin to imagine.
Judi Lynn
(160,656 posts)Three Potentially Habitable Planets Found Orbiting Gliese 667C
by Nancy Atkinson on June 25, 2013
A closer look at the previously-studied nearby star Gliese 667C has revealed a treasure trove of planets at least six with three super-Earths in the habitable zone around the star. Gliese 667C is part of a triple star system (Gliese 667) and is just over one third of the mass of our Sun. Now that we know there are multiple planets in the so-called Goldilocks zone a region where liquid water could exist Gliese 667C might be the best candidate for harboring habitable exo-worlds.
We knew that the star had three planets from previous studies, so we wanted to see whether there were any more, said Mikko Tuomi from the University of Hertfordshire in the UK, one of the astronomers who led the new study of Gliese 667C. By adding some new observations and revisiting existing data we were able to confirm these three and confidently reveal several more. Finding three low-mass planets in the stars habitable zone is very exciting!
Tuomi, along with Guillem Anglada-Escudé of the University of Göttingen, Germany looked at existing radial velocity data from the HARPS spectrograph at ESOs 3.6-metre telescope in Chile. The team said they are extremely confident on the data on the first five planets, while the sixth is tentative, and a potential seventh planet even more tentative.
More:
http://www.universetoday.com/103131/three-potentially-habitable-planets-found-orbiting-gliese-667c/#ixzz2XGa7FdTQ