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View Full Version : New Earth-sized Exoplanet is in Starís Habitable Zone



Fraser
2010-Sep-29, 09:10 PM
An enticing new extrasolar planet found using the Keck Observatory in Hawaii is just three times the mass of Earth and it orbits the parent star squarely in the middle of the star’s “Goldilocks zone,” a potential habitable region where liquid water could exist on the planet‘s surface. If confirmed, this would be the most [...]

More... (http://www.universetoday.com/74640/new-earth-sized-exoplanet-is-in-star%e2%80%99s-habitable-zone/)

Trakar
2010-Sep-29, 09:43 PM
I really wish they would stop with the sensationalism. A planet 1.5x the mass of the Earth does not fit "earthlike" to any serious consideration. Heck, even a +/- 10% can skew the "Earthlike" consideration for many aspects and properties.

Hungry4info
2010-Sep-29, 11:13 PM
In terms of bulk composition, the planet is probably Earth-like in that it is like Earth, a solid rocky world. This is what the paper means.

whimsyfree
2010-Sep-30, 12:08 AM
I really wish they would stop with the sensationalism. A planet 1.5x the mass of the Earth does not fit "earthlike" to any serious consideration.

Where did you get 1.5 from? Wikipedia (http://en.wikipedia.org/wiki/Gliese_581_g) is quoting 3.1-4.3 Earth masses minimum. A rocky planet of the smallest of those masses (unlikely) would have a surface gravity of about 1.5g, which would probably count as uninhabitable for most people.

I get an irradiation of about 0.6S for Gl581g, which is compatible with a liquid water environment.

Canis Lupus
2010-Sep-30, 01:30 AM
It has a dark side. Yum, yum, that would mean cookies, according to Chrissy.

astromark
2010-Sep-30, 03:04 AM
Never mind the nit pick... The interesting fact I gleam from this is...

That there are earth like planets in the Goldilocks zone of near by stars...

No, its not another earth...but its getting nearer and, must rise the odds of finding such.

Canis Lupus
2010-Sep-30, 03:09 AM
Never mind the nit pick...

Hopefully I am mistaken in thinking this refers to my post because it is a little embarrassing to be pointing out obvious good natured humour.

astromark
2010-Sep-30, 03:38 AM
:clap:I always have time for humor...and love it.

This 'Earth like planet find has made it into the first ten minutes of the evening news.'... here in NZ

otakenji
2010-Sep-30, 04:15 AM
To avoid the hyperbole, here is the link to the original scientific paper that was published and created all of the press attention:
http://www.ucolick.org/~vogt/ms_press-1.pdf

Van Rijn
2010-Sep-30, 04:22 AM
To avoid the hyperbole, here is the link to the original scientific paper that was published and created all of the press attention:
http://arxiv.org/PS_cache/arxiv/pdf/1009/1009.5814v1.pdf

Is it? That seems to be an article about atmosphere models for Gliese 581D. The new story seems to be a claim for another planet (581G).

astromark
2010-Sep-30, 07:37 AM
'Otakenji' have a look at OP #1. Where Fraser has given you the full story...

Twenty light years away, 581g A six planet, so far orbiting Gliese... Some excitement is warranted.

tnjrp
2010-Sep-30, 07:47 AM
Is it? That seems to be an article about atmosphere models for Gliese 581D. The new story seems to be a claim for another planet (581G).I do believe this is the article about 581g:
http://arxiv.org/abs/1009.5733

It's an interesting find to be sure but I'm still not breaking out the bubbly in the middle of the work week.

otakenji
2010-Sep-30, 04:32 PM
I stand corrected, and corrected the post.

Trakar
2010-Sep-30, 04:59 PM
Where did you get 1.5 from? Wikipedia (http://en.wikipedia.org/wiki/Gliese_581_g) is quoting 3.1-4.3 Earth masses minimum. A rocky planet of the smallest of those masses (unlikely) would have a surface gravity of about 1.5g, which would probably count as uninhabitable for most people.

I get an irradiation of about 0.6S for Gl581g, which is compatible with a liquid water environment.

There's a reason wiki isn't considered a reliable and authoritative reference.

Trakar
2010-Sep-30, 05:00 PM
To avoid the hyperbole, here is the link to the original scientific paper that was published and created all of the press attention:
http://www.ucolick.org/~vogt/ms_press-1.pdf

Thank you

Trakar
2010-Sep-30, 05:23 PM
Sorry, to be such a stickler, but a hunk of rock orbiting a star within the narrow range of where its solar emissions allow the triple point of water to exist upon its surface, simply doesn't make a planet "Earth-like." Personally, as stated earlier, I don't consider Venus to be "Earthlike" but it is certainly closer to that than any other planet in our solar system (and anything yet discovered in any other stellar system). To my considerations "Earthlike" is a very specific and narrow definition, not some broad and general category.

Hungry4info
2010-Sep-30, 07:09 PM
There's a reason wiki isn't considered a reliable and authoritative reference.

What about the discovery paper? It says 3.1 Me as well.

Trakar
2010-Oct-01, 06:31 PM
What about the discovery paper? It says 3.1 Me as well.

IINM, this is a minimum value, based upon methodology employed. Actual mass may be much more.
as stated before 3.1 earth mass equivilant is not "earthlike" (IMO),
orbiting about twice as close to your parent star as Mercury orbits our Sun, is not "Earthlike" (IMO)

whimsyfree
2010-Oct-03, 01:26 AM
There's a reason wiki isn't considered a reliable and authoritative reference.

Do you have an answer to the question?

Trakar
2010-Oct-03, 03:14 AM
What about the discovery paper? It says 3.1 Me as well.

no it says: "...GJ 581g, a minimum-mass 3.1M⊕..."

as well as: "...So, the likely mass for this planet candidate is 3.1 – 4.3M⊕..."

The problem is in the gross, overly broad definitions being ascribed to as "Earth-like/size/mass":


...The official definition of ⊕ is given by the Exoplanet Task Force Report (Lunine et al. 2008) as:
“The fraction of stars that have at least one potentially habitable planet. The Task Force
defines a potentially habitable planet as one that is close to the size of the Earth and that
orbits within the stellar habitable zone. Close to Earth-sized means between 1/2 and twice
the radius of the Earth or in terms of mass between 0.1 – 10 times the mass of the Earth...

To expand and distort the characteristics of "earthlike" this greatly is to render the term virtually meaningless, at least with regards to issues such as life as we know it and have evidences in strong support of.

whimsyfree
2010-Oct-06, 01:32 AM
Do you have an answer to the question?

It seems not. Apparently you're one of the posters who wont admit it when they've made a mistake.

Trakar
2010-Oct-06, 03:37 AM
Do you have an answer to the question?

Sorry, I didn't see your question and even in looking at it it took me a while to figure out what you were referring to.

The "1.5x" reference was me saying that I wouldn't consider a planet half again as massive as the Earth to be Earthlike, yet alone one 3x as large. This should have been clear from my later statements that I don't consider venus to be "Earthlike" and it is only 20% less massive.

whimsyfree
2010-Oct-09, 08:18 AM
The "1.5x" reference was me saying that I wouldn't consider a planet half again as massive as the Earth to be Earthlike, yet alone one 3x as large.

Desperate stuff.

Jim
2010-Oct-09, 08:46 PM
Whimsyfree, let's keep the discussion civil.