Five potential habitable exoplanets now

Phys.org ^ | July 20,2012 | Staff

[Red Badger]

New data suggest the confirmation of the exoplanet Gliese 581g and the best candidate so far of a potential habitable exoplanet. The nearby star Gliese 581 is well known for having four planets with the outermost planet, Gliese 581d, already suspected habitable. This will be the first time evidence for any two potential habitable exoplanets orbiting the same star. Gliese 581g will be included, together with Gliese 667Cc, Kepler-22b, HD85512, and Gliese 581d, in the Habitable Exoplanets Catalog of the PHL @ UPR Arecibo as the best five objects of interest for Earth-like exoplanets.

Doubts about the existence of Gliese 581g appeared only two weeks after its announcement on September 29, 2010 by astronomers of the Lick-Carnegie Exoplanet Survey. Scientists from the HARPS Team from the Geneva Observatory, which discovered all the previously known four planets around Gliese 581, were not able to detect Gliese 581g out of their own data, which included additional observations. Further analysis by others scientists also questioned the existence of Gliese 581g in the last two years.

Now the original discoverers of Gliese 581g, led by Steven S. Vogt of UC Santa Cruz, present a new analysis with an extended dataset from the HARPS instrument that shows more promising evidence for its existence. The new analysis strength their original assumption that all the planets around Gliese 581 are in circular and not elliptical orbits as currently believed. It is under this likely assumption that the Gliese 581g signal appears in the new data.

“This signal has a False Alarm Probability of < 4% and is consistent with a planet of minimum mass 2.2M [Earth masses], orbiting squarely in the star’s Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility” said Vogt.

Based on the new data Gliese 581g probably has a radius not larger than 1.5 times Earth radii. It receives about the same light flux as Earth does from the Sun due to its closer orbital position around a dim red dwarf star. These factors combine to make Gliese 581g the most Earth-like planet known with an Earth Similarity Index, a measure of Earth-likeness from zero to one, of 0.92 and higher than the previously top candidate Gliese 667Cc, discovered last year.

“The controversy around Gliese 581g will continue and we decided to include it to our main catalog based on the new significant evidence presented, and until more is known about the architecture of this interesting stellar system” said Abel Méndez, Director of the PHL @ UPR Arecibo.

Authors on the original paper are Steven S. Vogt, UCO/Lick Observatory, UCSC; Paul Butler, Department of Terrestrial Magnetism, Carnegie Institution; and Nader Haghighipour of the Institute for Astronomy and NASA Astrobiology Institute. Their research is published online on July 20, 2012 in the journal Astronomical Notes, 333, No. 7, 561-575.

[Red Badger]

Artistic representation of all the five known potential habitable worlds including now Gliese 581g, the best candidate for an Earth-like exoplanet so far. All of these planets are superterrans (aka Super-Earths) with masses estimated between two and ten Earth masses. Numbers below the planet names correspond to their similarity with Earth as measured in a scale from zero to one with the Earth Similarity Index, one being identical to Earth.

Comparison of the estimated relative size and orbits of the five exoplanets around Gliese 581. The green shade represent the size of the habitable zone, or the orbital region where an Earth-size planet could have surface liquid water. Planets e, b, and c are too hot for liquid water and life but g and d are in the habitable zone. Planet g is specially in the right spot for Earth-like conditions while d is marginally within these limits, and colder. This is the first case of a stellar system with two potential habitable exoplanets orbiting the same star.

[Red Badger]

Ping!.........

[texson66]

And only 20 light years away!

[musicman]

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[cripplecreek]

Good article. Must be the writer has a fair amount of scientific knowledge and didn’t over sensationalize it.

[the invisib1e hand]

And only 20 light years away!

hey, you want privacy, you gotta commute.

[cripplecreek]

[DigitalVideoDude]

20 light years is only 117,572,507,463,672.14 miles.
That's 117.5 trillion miles.
Just a hop, skip and a jump!

[Tenacious 1]

We should send a probe tomorrow. My children’s children might someday know for sure if their children’s children could live there in about the year 2200.

Cool.

[Bubba_Leroy]

The most “Earth-like” planet ever discovered is named Venus. Similar mass, radius, density and just a little bit closer to the sun than Earth. If only Venus had a magnetic field and a moon it would probably be habitable.

I suspect that most if not all of the “Earth-like” exoplanets are actually “Venus-like” or “Mars-like.”

[jimmygrace]

I have my doubts that any superterrans can foster life. If the planet is too big, most likely the core will be some material other than iron and have little or no magnetic field. No magnetic field means no protection from solar wind which means no atmosphere. I’d like to see an analysis of what size range of planets have the proper gravity to create an iron core.

[Red Badger]

At warp 5 we could get there in 4 years!..........

[ryan71]

“Habitable” in my book means walking around, breathing air not living in a spacecraft and/or wearing a space suit.

Thousands of parameters need to be just right to consider another planet, “habitable”.

Earth is special.

[bigheadfred]

[Bubba_Leroy]

At warp 5 we could get there in 4 years!

You need to recheck your warp factor calculations. At warp 5 we could get there in less than two months (one month if we have one of those new fangled 24th Century warp drive engines).

Warp Speed Comparison Chart

[Bubba_Leroy]

Thousands of parameters need to be just right to consider another planet, “habitable”.

I suspect that the number of parameters that have to perfectly coincide to make a habitable planet is in trillions. Even the list of known variables is pretty lengthy - size, mass, atmosphere, magnetic field, distance from the sun, type of sun, a relatively large moon to create tides, outer gas giants to block some of the debris, radiation from neighboring stars, etc.

Of course, we have no way to know how rare Earth is until we actually find another one. Until then it is all speculation.

[Riley]

How long is the trip at Ludicrous Speed?

[aimhigh]

I remember hearing years ago, that a 2% deviation in earth’s orbit would render it inhabitable.

[Flavius]

Let’s go

[Alas Babylon!]

Would an orbit only .13 AUs not be tidal locked? Therefore only one side would get constant sunlight, while the other hemisphere would be in constant darkness?

While life could exist on such a world, I think it wouldn’t be Earth-like.