I’m sure this question has been asked before, but it made me wonder recently because I heard someone mention that we’ve currently discovered something like 100+ extrasolar planets. Granted, many of them are just gas giants from failed stars, but I figure the more we find sooner or later we’ll find some that are similar to our profile, particularly as our detection methods get better through techological advances.
I know its like looking for a needle in a Mt Everest-sized haystack, but given that earth exists, I figure its only a matter of time before we find another solar system where similar conditions happened to create another earth-like planet. I guess some questions I also have in this regard are:
-How time-specific are the conditions to create an earth-like planet? Are they perhaps more common than we think, its just they are earth-like in a ‘narrow’ time frame? i.e. some planets we’ve found used to be/may become earthlike?
-Is it feasible to have 2+ earthlike planets in one solar system? As in, having them at just the right orbital distance from their star to have a stable atmosphere that can support liquid water yet not having a proximity to each other to cause major gravitational issues?
I know a couple of people who work in this area and they hope to find them within a relatively short timescale, possibly as short as a year or two, but possibly several years.
Given that an earth like (as in small and rocky) planet has been imaged for the first time recently it is only a matter of time before more are imaged, as the frequency of imaged planets increases the likelihood of finding one with water and oxygen increases.
Depends on what you mean by “earth-like”. If you mean a rocky body rather than a gas giant, we’ve already found some, the only trouble is that they are orbiting a pulsar rather than a star. But eventually, maybe we’ve already found some, we’ll find some rocky bodies orbiting a star.
If you’re asking for a rocky body with liquid water that could be tougher. But if we find a rocky body orbiting a star we can get a good estimate of how much solar radiation it gets and therefore how hot the surface is. If that surface temperature is somewhere between 0C and 100C then it’s pretty likely that there is at least some liquid water on the planet.
We might also be able to detect the presence of water or O2 directly, via spectroscopic analysis. But that’s going to be tough because the very very very faint light reflected by the planet is overwhelmed by the very very very bright light emitted by the star.
We will almost certainly continue finding more earth-like planets as our technology and techniques get better at it.
The trick is that we can’t always know just how earth-like based on the information we’re likely to get. Venus and Mars are hotter and colder than Earth partly because of the distance from the Sun and partly because of their atmospheric conditions. Given the limited information we’d get on our system from another star, we might conclude that there are three potential earth-like planets here. To really be “Earth-like” from a human perspective, you need the right atmospheric mix (which may partly depend on plate tectonics) and the right magnetic shield.
Surprised no one has mentioned the launch of the Kepler Space Telescope a few days ago which is meant to specifically search for earth-like planets.
Actually it is hoped they will find planets in the “habitable zone” around other stars. Areas where liquid water could exist. Of course that will not definitively say they can or do possess life but it is a good start down that road.
Expect answers in the next few years from this mission (due to run for 3.5 years…how long data analysis will take I have no idea).
ETA: I read somewhere else about this telescope that from its vantage point trailing the earth it is sensitive enough to detect someone turning on their porch light on earth.
All NASA data is released to the public within a year after it’s collected (or earlier, if the principle investigators allow it), meaning that the PIs generally have a plan already in place to do the most important aspects of the data analysis within a year. Then, once the data embargo is lifted, there’s another flurry of activity as everyone else gets their hands on the data, but for a good mission, you’ll still have people making good use of the data decades later.
So most of the data analysis will be done in about a year, but there will probably be some ongoing for a very long time indeed. Also note that NASA likes extending successful missions whenever possible, and it’s not unheard-of for something to keep collecting useful data for five times as long as the official planned duration. So we might well still be getting fresh new data from Kepler a decade or two from now.
Earth is not going to have “Earth-like conditions” for the entire lifetime of the Sun, silly as that sounds. The Sun is getting brighter as it fuses its supply of hydrogen into helium. Eventually (I have heard estimates of 1 billion to 3 billion years from now), it will make Earth hot enough that the oceans will boil. With an estimated lifetime of 10 billion years for the Sun, that’s quite a bit of uncertainty as to what fraction of the lifetime of the Sun will have Earth with “Earthlike” conditions.
Having the right magnetic shield might depend on plate tectonics, too. That’s one possible explanation for why Venus doesn’t have a magnetic field like Earth’s, despite being of similar size. Water helps plate tectonics along, too, and may be required for plate tectonics.
There’s no mystery why Venus doesn’t have a significant magnetic field; that’s just because she’s rotating so slowly. The mechanism by which planets and stars produce a magnetic field depends on rotation. Now, Mars’s lack of field is a bit more interesting, since he rotates about as fast as Earth, but may be related to a relative lack of core differentiation (Mars’s iron is spread out through the whole planet, rather than being mostly concentrated in the core like Earth’s).
BlinkingDuck, the bottleneck in predictions is always in getting off the surface of the planet. Kepler having now been launched, optimism about its results is perfectly reasonable. Most successfully-launched experiments or observatories have produced the results expected in the time expected, and often have produced much better results or quicker than planned.
I thought that Oxygen would not be present in an atmosphere unless there was life? Please fight my ignorance as this may be something I read or watched on the TV.
For the Op you might be interested in the book RARE EARTH by Peter Ward, a good read, and if I recall correctly discusses some of these issues.
I was gonna start a thread on that in the next day or two.
Roughly speaking, its going to look at a 100,000 stars for the next few years. Your chance of detecting OUR Earth orbiting some other sun like star using their method is somewhere between one in 200 to 400. So, if EVERY star has an “earth”, thats 250 to 500 “earths”. Lets say only one in 50 have an “earth”. Thats still 5 to 10 of em.
So, within just a few months of operation, Kepler has a decent chance of seeing a blip. Withing a year, it could see a dozen or so blips, some of them being repeats which confirm this or that particular “earth”.
So, unless “earths” are fairly uncommon, the answer is darn soon. Yeeeahhhh
Correct. Did you see something which contradicts this?
Note, of course, that it’s also possible to have life without putting significant oxygen into the atmosphere, so the absence of oxygen doesn’t tell you much of anything.
A couple of responses mentioned detecting oxygen in the atmosphere. I guess this lead me to :
A) if Oxygen was detected, would not this be the biggest scientific discovery ever? If ox = life that is. (not that finding a earth like planet would not be a big deal).
B) Would a planet be considered Earth like if it did not have any Oxygen in the atmosphere? A planet could be in the habitable zone, (liquid water), have a reasonable atmosphere ( ie thick enought to protect surface life, but not Venus like), but not have any Oxygen in the atmosphere.
The Earth itself had life for more than a billion years with no significant O2 in the atmosphere. Then some bacteria learned the trick of photosynthesis and started pumping out O2, which was toxic to almost all other life on earth.
Yes, which is why we’d really like to be able to detect oxygen in an atmosphere.
As for whether a planet would be considered “Earthlike”, that depends on your definition. Some standards of “Earthlike” include Mars; some even include Venus, Mercury, and Luna. Of course, the more like Earth a planet is, the more exciting.
