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NASA's Kepler Spots Its First Rocky Exoplanet
coondoggie writes "NASA today said its star-gazing satellite Kepler has identified its first rocky planet orbiting a sun similar to our own — 560 light years from our solar system. While not in an area of space considered habitable, the rocky planet known as Kepler-10b is never-the-less significant because it showcases the ability of Kepler to find and track such small exoplanetary movements. 'Kepler's ultra-precise photometer measures the tiny decrease in a star's brightness that occurs when a planet crosses in front of it. The size of the planet can be derived from these periodic dips in brightness. The distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star. Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet's surface. However, since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer to its star than Mercury is to our sun and not in the habitable zone.'"
Yo' Adrian!
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The headline isn't flashy enough.
Should read:
NASA's Kepler Spots Hell 560 light years from earth and closing.
That's less than 2 million miles, or .05 AU from the sun.
Quite toasty.
So this means if a planet orbits a sun in any other plane than the one that happens to line up directly with us, it wont spot anything? Wouldn't that be...most of space?
Seeing as Kepler uses transits to find these planets, I wonder what the expected timeframe is for when they start really pumping out the data. I mean, if it looking at the right place for a year solid, it would expect to see one dimming of our sun from us (if it was pointed at our system from elsewhere). And that is only to find a single transit. Then add another year to get the orbit, probably another year at least to confirm.
To me it seems that it is going to be a very slow start (apart from these totally hotrock type planets with insanely quick orbit) but then the taps will be turned on and they will start finding exponentially more and more?
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Im very curious how they know this...how can they determine this is not simply a sunspot if it is that close? It's my understanding all the Kepler measurements are validated on the ground with telescopes checking doppler shifts for the wobble method...for something this close and this small, wouldn't that be a problem?
The Roche limit is defined as:
d = R ( 2 rhoM/rhom) ^ (1/3).
d is the orbital distance.
R is the primary (star in this case) radius.
rhoM is the primary's density.
rhom is the satellite's density.
If rhom > 2 rhoM, d is inside the radius of the primary.
The star in question is similar to ours, so I'll use our sun's density: 1.4 g/cm^3
The planet's density is 8.8 g/cm^3.
Therefore, the roche limit is within the star's radius and the planet will not be ripped apart.
This presumes a nearly circular orbit, which is good enough for this case.
And that is only to find a single transit. Then add another year to get the orbit, probably another year at least to confirm.
Well, probably yes, assuming they're looking for yearly (like Earth's) orbits. Makes a bit of sense, but an Earth-like planet might be closer or further away from its host star, and be perfectly OK for liquid water, life, all that (depending on the host star's energy output). Probably not very different from a year though, it rather depends on the sizes (mass and orbital radius) involved.
As for the confirmation, it might not get that long; since the dip might be a starspot or a different agent, a Doppler effect study (or astrometry, in the future) might confirm or dismiss it because, to some extent, different methods of detection can be used on the same source for confirmation. Though, on the Kepler mission, I think the confirmation is 'included' and the timeframe is set for 3 years.
To me it seems that it is going to be a very slow start (apart from these totally hotrock type planets with insanely quick orbit) but then the taps will be turned on and they will start finding exponentially more and more?
Hopefully yes. For the moment the methods of detection are biased- each of them is capable of locating specific groups of planets based on two parameters, those parameters being the planetary mass and its distance from its host star- there's also gravitational lensing that can 'see' better, but its a one-timer.
Encouragingly enough, if one plots the findings so far (mass vs orbital distance) it is not hard to imagine that the so far covered areas will start to expand. My point being that, before the Kepler mission, 'hot Jupiters' kept being the majority of bodies discovered, because they are the only ones we had the means detecting- Kepler has been watching the same patch of space, and it should see more than 'hot Jupiters' (provided they're out there and we are going around this the right way).
The three laws of thermodynamics:(1) You can't win. (2) You can't break even. (3) You can't even quit.
.. not my favorite term, but a way to derive it in front of astrophysics students is to assume a planetary body, no atmosphere, figure out its surface temperature, and demand it to be 'within liquid water limits'.
Now, since one may very correctly inquire, "liquid water without atmosphere? Are you on crack? And do your math, some planets are obviously not in it like, well, THE ONE WE'RE STANDING ON", I will have to add that I have been in two conferences so far, and 'habitable zone' seems to be more a popular term than a scientific one.
There is much talking though on 'expanding' the definition (see 'dwarf planet' for examples on how that works) talking into account atmospheres, orbital characteristics and other stuff.
Still, given where we stand now regarding exoplanet detection, it's not so bad using what we've got and work our way up from there.
The three laws of thermodynamics:(1) You can't win. (2) You can't break even. (3) You can't even quit.
So to find a truly earthlike planet, won't they have to focus on a single star for more than a year in order to detect the planet passing the star more than once?
Yep. And for Jupiter-like planet we'd need to be watching it for hundreds, if not thousands of years if we were to use this method.
What if the planet's orbit never aligns to eclipse the sun?
Then we would never detect it via this method.
What if there are two or three planets in very similar orbits?
It depends on how well they are aligned. Even if they're perfectly aligned, we're liable to see the first one before the second or third one as it passes in front of the star. If they are even slightly out of phase, they will eventually be in an orbit in which we see all three distinctly. In any case, the radius and shape of the occlusion in front of the star is determined by the shape of the light intensity vs. time graph. Circular disks have a very specific light occlusion shape, while abberant occlusions have different shapes.
When referring to planets it always means "where liquid water could exist".
Because we have an ever so slight bias towards life as we see it on Earth.
Life at the anaerobic microbial level would be well suited to this, but higher organisms not
Not even those evolved from the "primordial soup of molten silica with the abundant phosporic and alumina nutrients in the presence of the rich cesium vapour atmosphere with the right amount sodium and that extra pinch of lithium, in the just-about-right-100m-tides created by their star which feeds them with the hydrogen and helium so generosly every day"?
Questions raise, answers kill. Raise questions to stay alive.
I have always felt that people put too narrow a view on what life is or could be.
You're reading too much into it if you're thinking they're limiting their view on what life is or could be. If I tell you I've just arrived in the city and am looking for good Italian restaurants, it does not follow that I am assuming only Italian food exists or could exist. It's just the kind I'm most interested in finding at the moment. The "habitable zone" is the zone that could support all the life we've ever detected. If we detect new forms of life, the zone will get bigger. There's no a priori assumption here that only life as we know it can exist, it's an a posteriori judgement: "this is what we've seen -- where could it survive?"
"Convictions are more dangerous enemies of truth than lies."