Earth-size planets abound in Milky Way

[StarRider1701]

Vindication - at last! And right on SDC's front page!

Many of you have stated over and over again that earth sized and earth like planets will be rare in our Galaxy. To this I have always said that we don't yet know that because we cannot see planets that small yet. But you all persisted, despite the total lack of evidence supporting you. Just because some "powers that be" somehow decided that they knew all about how planets formed in other solar systems merely from looking at the very few planets that we have been capable of seeing to date.

Today, on the SDC home page the article has vindicated my seemingly lone voice of reason. Oh, ye of little faith. Should I say "I told you so?" Yes, I think I will.

 

[bdewoody]

Re: Vindication - at last! And right on SDC's front page!

Twenty five to thirty years ago the commom wisdom among astronomers was that stars with planets would be very rare and that stars with rocky planets even rarer still. The numbers originally used in the drake equation had like one in a million stars with planets and then only one in a million stars with planets having any that could support life. I think it's great that modern equipment has allowed astronomers to conclude that the old guesses were way off. But I'm not ready to hop the next space freighter to Gliese just yet. Our predicament is that we happen to be located in a region of our galaxy that is relatively sparsely populated which also may be a prerequisite for developing intelligent life and as eager as we are to get out there and say howdy to our neighbors the laws of physics must be obeyed and we will most likely remain on our own for the forseeable future.

 

[captdude]

The following link will take you to the full article that has its first few paragraphs cut & pasted below.

http://news.yahoo.com/s/afp/20101029/sc_afp/usastronomy

Thu Oct 28, 10:24 pm ET
WASHINGTON (AFP) – One out of four Sun-like stars in our Milky Way galaxy could host Earth-size planets, making life-bearing systems like ours possibly more common than previously thought, according to a new astronomical study.

Dubbed the most extensive planetary census of its kind, the NASA-funded study at the University of California, Berkeley found that smaller planets rather than massive ones are prevalent in close orbit to the stars.

"The data tell us that our galaxy, with its roughly 200 billion stars, has at least 46 billion Earth-size planets, and that's not counting Earth-size planets that orbit farther away from their stars in the habitable zone," said study co-author Geoff Marcy.

The astronomers for five years used the W.M. Keck Observatory in Hawaii to search 166 sun-like stars near our solar system for planets ranging from three to 1,000 times the mass of Earth.

The results showed more small planets than large ones.

 

[MeteorWayne]

Moved to Space Science and Astronomy...

 

[neilsox]

In our solar system, two (possibly 4) out of 8 planets are approximately Earth size, so there is likely no good reason to think typically stars have less than two. As Venus illustrates, Earth size can be very different in respects other than size. A significant oxygen atmosphere seems unlikely unless there are photosynthesis plants (which require water in a rather narrow band of temperature) Earth would likely lose half of it's free oxygen in less than a million years of no photosynthesis. Perhaps we should ask do 1% of the the planets within 100 light years have significant photosynthesis at present? What changes are necessary to allow photosynthesis for the other 99%? Clearly the changes are difficult for Venus, Mars. Europa, Titan etc. Other difference are also likely hostile to life.
Clearly we can genetically modify humans to shift the range of optimum conditions by at least a small amount. Large changes may remain impractical, if not impossible, very long term. The worst disadvantage, is persons comfortable in one environment may find Earth typical unacceptable after modification = they can't visit Earth. Neil

 

[SpaceTas]

3 different search methods are all indicating that there are a large number of earth mass planets.

Micorlensing and radial velocity methods extrapolate current results to estimate near 40% or near 25% (respectively) of single stars have earth mass planets. Radial velocity estimates are for close in planets, while microlensing is for distant (> 2 AU) planets. Microlensing shows there are many more cold small planets than close in hot planets (radial velocity and transits). Also this method estimates only 1/6th of planetary systems are like our Solar System (space for small planets close in, giants in middle, Neptunes on outside)

Kepler has found many many more small transit features. But until these are followed up with ground based spectroscopy and imaging to eliminate grazing binary stars, we don't kn ow the real fraction. All these Kepler candidates are close in. Only after 3 years will it really probe 1AU (earth-like orbits).

 

[StarRider1701]

In our solar system, two (possibly 4) out of 8 planets are approximately Earth size, so there is likely no good reason to think typically stars have less than two.
Clearly the changes are difficult for Venus, Mars. Europa, Titan etc. Neil

I wouldn't call Mars, "Earth Sized." With its light gravity I don't think it could hold an atmosphere even if it were in the same orbit of Earth.

As for Europa and Titan, they are not planets but moons. Althought Europa might actually be the next most livable place in our solar system!

 

[SteveCNC]

I have to agree with you about Europa being the most habitable object in our solar system besides earth , it has everything needed to be self sustainable .

 

[dragon04]

Europa would be far more problematic than Mars. Those enormous tidal forces are constantly cracking Europa's Icy Crust making it pretty dicey to set up shop there.

Mars on the other hand has water, CO2, modest gravity, and with the discovery of lava tubes, underground habitats could be constructed with ease compared to Europa. Not to mention that Mars is only months away from Earth as opposed to Years in the case of Europa. IMO, Mars is a far more habitable world than any other save Earth.

I like Europa for a robotic mission though. Especially one that can bore or melt its way down through the ice and into that global ocean.

 

[StarRider1701]

Europa would be far more problematic than Mars. Those enormous tidal forces are constantly cracking Europa's Icy Crust making it pretty dicey to set up shop there.

Mars on the other hand has water, CO2, modest gravity, and with the discovery of lava tubes, underground habitats could be constructed with ease compared to Europa. Not to mention that Mars is only months away from Earth as opposed to Years in the case of Europa. IMO, Mars is a far more habitable world than any other save Earth.

I like Europa for a robotic mission though. Especially one that can bore or melt its way down through the ice and into that global ocean.

Under the Ice - that's where we would live. We already KNOW that there is water under that ice, and the geysers are proof that there is some volcanic activity keeping that water warm. Because of that, I will bet that we find life, not just bacteria, but an ecosystem similar to what is in our oceans, there. That is truly where we would have everything we needed to live, Mars is a waste of time. Even if there is no life in that huge ocean, all we would need to bring with us is fish! We could mine the other moons for minerals we needed and live safely and happily on a huge raft inside a baloon(very simplistic description) between the water and the ice. At that point, we have perfectly livable conditions for Earth life(US) as well as the resources we needed with regards to water and air, not to mention a good probability of available food. Just make sure the top of the shaft is capped and the raft is anchored to the underside of the ice near the shaft.

Yes, I know. The hard part is making the shaft through who-knows how much ice. Is it 100 feet thick? 500? 1000 or more? I realize that we don't know that yet. But hey, few things worth doing are easy.

 

[jaxtraw]

As for Europa and Titan, they are not planets but moons.

Titan would have been a planet if it had found a stable orbit and avoided capture by Saturn.