First Earth-Sized Exoplanet May Have Been Found 222
Adam Korbitz writes "New Scientist is reporting the extrasolar planet MOA-2007-BLG-192Lb — whose discovery was announced just last summer — may actually be the first truly Earth-sized exoplanet to be identified. A new analysis suggests the planet weighs less than half the original estimate of 3.3 Earth masses; the new estimate pegs the planet's size at 1.4 Earth masses. The planet orbits a small red dwarf star, some 3,000 light-years from here, at an orbital distance of 0.62 astronomical units, about the same distance as Venus from our sun. One significance of the planet's discovery is that it points to the probable ubiquity of smaller terrestrial planets in somewhat Earth-like orbits around red dwarf stars, the oldest and most numerous stars in the galaxy. Here is a video report from the discoverers."
Re:GNAA (Score:5, Informative)
Food for thought.
ps June 2, 2008 (Score:5, Informative)
Using standard nomenclature, the star hosting the newly discovered planet is dubbed MOA-2007-BLG-192L with MOA indicating the observatory, 2007 designating the year the microlensing event occurred, BLG standing for bulge, 192 indicating the 192nd microlensing observation by MOA in that year and the L indicating the lens star as opposed to the background star further in the distance. The planet maintains the name but adds a letter designating it as an additional object in the star's solar system, so it is called MOA-2007-BLG-192Lb.
Hello MOA-2007-BLG-192Lb. How are you? We're fine thank you.
How's the weather? Would you like to play a game?
might be a lil off topic (Score:3, Informative)
Re:GNAA (Score:5, Informative)
As our techniques become more sophisticated, we will be able to find more planets of a comparable size to our own. Those 335 can be thought of as the 'first wave' of discovered exoplanets. Large bodies close to their parent stars. These planets are interesting for what they can tell us about how solar systems can form.
The next wave of discovered exoplanets will be smaller, say between the sizes of Venus and Neptune, and therefore far more interesting from the perspective of extrasolar life.
Re:'Earth-sized' can be misleading (Score:2, Informative)
Downright inhospitable, in fact, which is -- I think -- the word you were looking for.
Re:Quick quiz (Score:4, Informative)
could it not be possible to have a planet the size of say, Neptune, with a geological makeup similar to the Earth, that has a lower mass and therefore the acceleration at the surface is exactly 1g
It's entirely possible for a gas giant -- according to Wiki, the "surface gravity" of Neptune is 1.14g, and for Uranus it's 0.886g. I put "surface gravity" in quotes here for obvious reasons, but something like the "cloud city" in The Empire Strikes Back would be quite livable on either of these planets. As for rocky planets, it seems doubtful. Anything solid that was of Neptunian size and mass would, I think, very quickly collapse into a much more compact mass with much higher surface gravity.
Re:So? (Score:3, Informative)
For those who like to see some actual observations back up speculation, detection of an Earth-sized planet is a big deal. Until we see some, we can't really say how many such planets exist. Once we see one we know that we can detect them. Once we see two, we can start to make (poor) estimates of how many there are. From there the estimates only get better.
I'm sure Dr. Lineweaver would agree, see as how the first research interest listed on his web page is "the analysis of recent exoplanet data and its ability to address the question 'Is our Solary System typical?'" (http://www.mso.anu.edu.au/~charley/)
Re:Quick quiz (Score:3, Informative)
A planet with the same composition as Earth but with 10 times the mass will NOT have 10 times the surface gravity. It's radius will be larger, so the surface gravity will be less than 10x, but greater than 1x.
As warm as Pluto or as cold as Venus... (Score:1, Informative)
The planet orbits its host star at a distance equivalent to that of Venus from our Sun. Because the host star is probably between 3000 and 1 million times fainter than our Sun, the top of the planet's atmosphere is likely colder than Pluto. However, planetary formation theory suggests a thick atmosphere blankets the planet, which combined with radioactive decay in the planet's interior may make it as warm as Earth.
So it could be inhabitable, it might have an ocean, and maybe there are aliens that look like E.T. living there. Maybe. But does it have a Stargate?
Re:Quick quiz (Score:3, Informative)
It would have to be composed of dramatically different mix of elements; low density due to structural differences would not be possible beyond some fairly small radius -- far, far, smaller than Earth. Basically, once an object is large enough that gravity can form the object in to a sphere, the mass of the object will be high enough to obliterate any pore space beyond a fairly shallow depth. The details can be fairly readily calculated knowing the strength of rock, which is indeed well known for rock types that would constitute the bulk of any likely Earth-size planet.
The likelihood of maintaining a structurally low density planet, beneath a very shallow layer at the top of the planet's crust, is further reduced due to the problem of heat. Rock weakens as heat increases, and heat increases with depth. Even a geologically dead planet would have or have had considerable heat at depth at some point in its life, at which time the low density material would have collapsed.
This also ignores how such a body could form, certainly beyond my creativity to imagine.
A planet simply is not going to be low density by virtue of its structure. You need different materials.
The bulk of the Earth is made of silicate rock, iron, and nickel, giving it an average density of about 5.5 grams per cubic centimeter. You could build a planet of somewhat lower density using various kinds of ice.
The problem there, however, is that you probably won't be able to achieve density much lower than something between 1.2 and 1.8 grams per cubic centimeter (the precise amount depends on how exotic a composition you're willing to invent and its total mass -- substances will possess increasingly dense crystal structures as the material is put under higher pressure). That's a lot less than Earth, but not close to the level's originally suggested. And this planet certainly isn't going to look an awful lot like Earth. It'll look more like Titan.
Red Dwarfs & Life: the good and the bad of it (Score:5, Informative)
Specifically, Earth biology wouldn't do well orbiting a red dwarf [wikipedia.org]. Red dwarfs emit most of their energy via thermal convection, rather than (like our Sun) via radiation. This leads to lots of radiation bursts when convection cells reach the surface. At 1 A.U., no big deal. But, at an orbit close enough to keep - say - Earth as warm as it is orbiting the Sun, life would get hammered.
This isn't to say that *something* wouldn't evolve. It's just that at a basic level, it wouldn't resemble anything we're familiar with. And, given how long a red dwarf stays in the Main Sequence, there'd be billions upon trillions of years to simmer the soup 'til it was just right.
Re:might be a lil off topic (Score:3, Informative)
Writing hypertext seems to be a bit of an art form these days. If you've got five pages you want to link to you're not supposed to just pick five random words in your text and turn them into links.
Re:On the flip side... (Score:3, Informative)
All of which could be designed to "hypothetical" standards without the imminent fear of death.
Or... you could actually threaten people with death and force them to survive in a large Warehouse full of nerve gas.
Creating a 'space' environment in which technology is required to keep a crew alive is readily available on earth. It has the added benefit of saving hundreds of millions of dollars in rocket fuel to launch it somewhere it's not really needed.
Low gravity is the only condition I'm aware of that can't be readily simulated on terra firma. (Ignoring flight control, navigation, starship testing stuff. None of which is terribly useful in improving a more sustainable habitat here on earth.)
Save the tens of millions of dollars that would be spent launching our marginally useful environment improvement technology and put it straight into R&D.
Re:Quick quiz (Score:4, Informative)
g = G*Me/(Re)^2
Now you want something with the same g, but 10 times the mass?
G*10*Me/R^2 = g = G*Me/(Re)^2
It works out that:
R = sqrt(10)*Re or a little over three times the radius. So a planet with ten times the mass of Earth, and three times the radius, would have about the same gravitational pull at the surface.
Re:On the flip side... (Score:2, Informative)
Re:Red Dwarfs & Life: the good and the bad of (Score:5, Informative)
Uhh.. pardon me, who moderated this insightful?
All low-mass stars, including the Sun and ranging up to F-Type stars (about 1.7 times solar mass) have an outer convection zone (meaning that outside the core, and up to the surface, energy is transported by convection). There's nothing 'bursty' in that mechanism.
Hard radiation of low-mass stars is generated in the corona, which is heated by magnetic reconnection events (the magnetic equivalent of a short), leading to sudden release of the energy stored in magnetic fields. This is what is called 'stellar activity': starspots, flares, X-ray radiation, ...
Some red dwarfs are indeed much more active than the Sun, many are not. Activity is generally connected to the age of a star since magnetic fields are generated by a dynamo mechanism, and stars spin down slowly as they are aging, leading to a less efficient dynamo and a decrease of activity.
Re:Red Dwarfs & Life: the good and the bad of (Score:2, Informative)
And, given how long a red dwarf stays in the Main Sequence, there'd be billions upon trillions of years to simmer the soup 'til it was just right.
life cycle of a red dwarf is around 100 billion years. trillions of years is out of the question. heck, the universe is only around 15 to 20 billion years old