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A Quarter of Sun-Like Stars Host Earth-Size Worlds
astroengine writes "Although there appears to be a mysterious dearth of exoplanets smaller than Earth, astronomers using data from NASA's Kepler space telescope have estimated that nearly a quarter of all sun-like stars in our galaxy play host to worlds 1-3 times the size of our planet. These astonishing results were discussed by Geoff Marcy, professor of astronomy at the University of California, Berkeley, during a talk the W. M. Keck Observatory 20th Anniversary Science Meeting on Thursday. '23 percent of sun-like stars have a planet within (1-2.8 Earth radii) just within Mercury's orbit,' said Marcy. 'I'll say that again, because that number really surprised me: 23 percent of sun-like stars have a nearly-Earth-sized planet orbiting in tight orbits within 0.25 AU of the host stars.'"
Lots of Goldilocks and no bears.
As Carl said, "...billions and billions..."
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
...that's translated as "lots of stars have planets in orbits which can in no way sustain life". Dims my hopes rather than the other way around.
Also: would that not decrease the chance of planets in goldilocks range overall, since planet material in that system was partly used to give birth to close orbiters?
...gis sdrawkcab (usually not responding to ACs; don't bother posting as AC)
As we all know, Mercury is not exactly hospitable to life. How many Earthlike planets are orbiting Sunlike stars in more Earth/Mars sized orbits?
Could it be that they're detecting none smaller than earth because we simply don't have the detection capability to go that small? Perhaps Earth is on the small side of rockies, despite being the largest rocky planet in our solar system? I guess I'm saying that "the mysteriosu dearth of planets smaller than earth" may simply be a detection/technology issue.
Although there appears to be a mysterious dearth of exoplanets smaller than Earth
-Our ability to detect smaller planets is improving, but is still limited.
-Many systems we have detected have Jupiter-mass or larger bodies orbiting very closely to the parent star. These huge planets are unlikely to have formed there. They could easily have "gobbled up" smaller planets when they moved inward towards the star.
-Forming solar systems are chaotic with tons of protoplanets. The smaller ones can easily combine or be smashed, absorbed, or thrown out of the system altogether.
What is "mysterious" about this dearth?
The news sounds bad... All those potential systems are now basically useless to us and probably wouldn't harbor life.
Because the death star has been busy!
I got to the chocolate box before you, that's why the hard ones have teeth marks.
And now you've said it four times. You said the same thing four times. Four times. The entire summary is just the same statement made four times.
Big Bird stands up to a third taller than the average adult. Should I tremble in fear?
In 30 years we will be able to detect planetesimals smaller than the moon orbiting stars out to 300 LY. This is of course just a guess.
I am very small, utmostly microscopic.
How much harder would be to find planets of those sizes if they were at a bigger distance from their sun?
"Sun-like stars?" Does that mean that they're owned by Oracle?
Earth-sized planets are underrepresented because while we have the right technology, we don't have funding for spacecraft capable of detecting them.
Dear God, please teleport me to one of these planets that is only inhabited by supermodel, nympho women. Thank you.
A Quarter of Sun-Like Stars, that we have observed, Host Earth-Size Worlds. Obviously, we haven't observed all the billions of stars in our galaxy. I happen to like Geoff, but is he up for a new grant or soemthing?
http://t.co/DhiB9Zxp
One unknown represented as the product of many unknowns is not progress, nor is it math. Ockham would slit his throat.
Fire up space engine http://en.spaceengine.org/ and find them.
p.s. don't click that link unless you want to be shown how small are planet is compared to the entire universe.
I am confused... can someone explain how this report is not selection biased against distant or small planets?
To put it another way, we started by finding huge planets. As we have gotten better methods, we have found successively smaller planets. The three factors that make a planet easy to find are its diameter (occlusion of star), gravitational effect (how much the star wobbles), and distance (how likely that the planet will occlude the star from our perspective, and also factoring into the gravitational effect).
Distant, small planets simply won't be detected from our perspective. So the report is not really saying 'Only 23% of stars have earth sized planets'. It's really saying 'We know that about 23% of stars have rocky planets that are really close. Since we have no reason to believe our solar system is extremely unique, that makes it very likely that an even greater percentage of stars have rocky planets that are farther out'.
This is probably a huge boost to the 'how many stars have possible life sustaining planets' factor in that oft derided formula, the Drake equation.
"I will trust Google to 'do no evil' until the founders no longer run it." Hello Alphabet.
Look I am not a scientist but can we make a leap here and suggest that a given sun with similar mass and composition to our own, will contain planets of a similar sizes and orbits to our own due the laws of physics.
We all know that the law of gravity make things fall at the same speed so using this we can assume that a given planet will orbit around a star within a certain distance due the force of gravity.
Please let me know if I am wrong in this premise and shoot me down in flames.
So we look for earth like stars similar mass and composition, we should find earth like planets orbiting these stars.
I think there are two aspects to answering your question properly, and they depend upon the method of detection you contemplate.
The first technique that we have used to detect exoplanets has been through the laws of gravity - i.e. the mass of the exoplanet causes it's star to 'follow' it's orbit, even very slightly. This causes a minute shift in the light reaching us from the star. The force of gravity experienced between the two objects - the planet and it's star, varies inversely with the square of the distance separating them: translation - if you double the distance of separation, the gravitational effect is reduced to one quarter, and so on. From this it should be apparent that as you move further from the star, the ability of the planet to influence the star's position is reduced, and thus our ability to detect is reduced. Only very large and very massive exoplanets [or, at a pinch, other stars such as a brown dwarf] would be of use.
The second technique would be to look for occlusion events - that is, a darkening in the apparent brightness of the star as a planet transits between it's star and our point of observation. But let's think about this for a moment... The earth is positively tiny in relation to our sun, and if a remote exoplanet of similar size just happened to share an orbital plane with say a sizeable asteroid belt, then the scatter effect and variation in stellar brightness would, from a distance, have a greater random pattern. It would look like a low-variation flicker.
So - and I'm guessing - I'd suspect that planets orbiting further out, especially worlds with a gravity field compatible for humans, would be pretty darn hard to detect.
23 huh? There are also 23 flavors in Dr. Pepper. Is there a connection?
Absolutely. Present technology is strongly biased towards detecting large planets orbiting close to their stars in a plane we're looking at nearly edge-on. This is a recognized weakness among astronomers, and means that planets that depart from any of those criteria will be less likely/take longer to be detected. It typically take at least 3-5 orbits worth of observations to confirm a planet detection, and smaller or more distantly-orbitting planets will be harder to detect (lower signal-to-noise ratio), so more orbits are required for confirmation. Something like an exo-Jupiter with it's multiple-century orbit won't be directly* detected for a thousand years or so using current technology, despite it's large mass. And an exo-Earth with it's small signal and longer year will take much longer to detect than say an exo-Mercury.
We can make educated guesses about what other system are actually like, but for the immediate future the only planets types we can make any sort of statistical extrapolation about are the kinds that are easiest to detect. On the bright side as the length of observation increases not only can we detect more planets directly, we can also more accurately characterize the orbits of previously detected planets, including the perturbations caused by other planets in the system too small or slow to detect directly.
* technically what I'm calling direct detection is via the Doppler shift it causes in its star's spectrum
--- Most topics have many sides worth arguing, allow me to take one opposite you.
"Alone In The Universe: Why Our Planet Is Unique" by John Gribbin. I've just finished it. Those who've always hoped to one day chat with a Wookie or a Klingon (not to mention SETI-types) will find it thoroughly depressing, but it's filled with excellent science. There's a good review of it here:
http://freethoughtblogs.com/bluecollaratheist/2012/05/29/alone-in-the-universe-why-our-planet-is-unique-part-1
Computer geeks will like it because many of its conclusions are based on cluster-run computer simulations. :) The results of the simulations are nothing short of amazing.
Example: Earth's molten iron core is what gives us a strong magnetic field that protects our atmosphere. The only way they could get that to work out was to put a supernova(!!!) .1 light years (that's not a typo) from the solar system at a critical time while it was forming. This also helps answer why our system has an unusual mix of elements compared to other stellar systems (particularly of radioactives such as Aluminum 26 and Iron 60).
Example: we're actually a binary planet -- Earth and Moon. The moon is thought to have formed from a planet in the Langrange point, called "Theia," that would have fractured our thick crust, making continental drift possible; the moon's gravitational effects on Earth are also critical.
Read the book. Even if you disagree with it (and I know many here will, especially my good friends who love SETI), but it's an excellent read.
Cogito, igitur comedam pizza.
Astronomers (and/or the reporters sending these reports) keep making comments like "... there appears to be a mysterious dearth of exoplanets smaller than Earth..."
and then, later buried in the text:
"...âoeThis is a guess, but theyâ(TM)re just harder to detect,â Marcy told Discovery News. âoeSmall planets dim the star less â" the dimming has to be greater than the noise to detect the planet...."
Well, no SHIT, Sherlock. But: Observing a lack of something doesn't mean that something is missing, particularly when we KNOW our method of observations are clumsy and limited.
We only recently developed the tech to discover planets at all, so obviously our gross methods first detected the largest planets that would either a) swing the primary around the most, or b) occlude the most light.
The Earth, transiting in front of the sun, blocks about 1% of the (2d) visible side. That's not much occlusion.
Further, when you consider that our detection methods largely rely on the faint chance (see what I did there?) that the planet passes almost DIRECTLY between Earth and the observed primary - and does so repeatedly (at least 3x), and within the span of observation - it's pretty f*cking unbelievable that we've seen ANY. And if the chance of observing something happening is vanishingly small, yet we are seeing thousands of these, then isn't it logical that the event must be happening with very high frequency?
On the contrary, given our still-new detection technologies, and the geometry working against us, I'd say the numbers of planets we've already observed strongly suggests that 'planet-building mechanisms' are common around pretty much every star.
-Styopa
You find what you are able to see,of course.
Afghan version:
One day Mullah Nasruddin lost his ring down in the basement of his house, where it was very dark. There being no chance of his finding it in that darkness, he went out on the street and started looking for it there. Somebody passing by stopped and enquire:
- What are you looking for, Mullah Nasruddin ? Have you lost something?
- Yes, I've lost my ring down in the basement.
- But Mullah Nasruddin , why don't you look for it down in the basement where you have lost it? asked the man in surprise.
- Don't be silly, man! How do you expect me to find anything in that darkness!