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vikingmars
QUOTE (hendric @ Mar 11 2011, 05:57 AM) *
We could just call them all "Venus-like" until proven otherwise

You made quite a good guess after all dry.gif :
"...I think that the atmospheres of extrasolar Earth-like planets would be more like Mars or Venus than the Earth." (see article herebelow)
http://www.spacedaily.com/reports/Computer...pheres_999.html
"The analog in our solar system for the planets we have considered here is Venus." (see "What if Extrasolar Planets are Rocky ?" from LPSC XXIX) :
http://www.lpi.usra.edu/meetings/LPSC98/pdf/1409.pdf smile.gif
siravan
QUOTE (Syrinx @ Mar 11 2011, 12:56 AM) *
It's a function of stellar radius, planet radius, and orbital radius.


To the first approximation, (upper bound on) the probability of transit is 2atan((R+r)/d)/pi, where R is stellar radius, r is planetary radius and d is orbital radius. For Earth, it calculates to 0.6%, but note that it includes some marginal transits which are practically undetectable, so the probability of transit detection is lower. For Jupiter, it is 0.12%.
Greg Hullender
Just noticed a new Manager's Update on March 8: http://www.kepler.arc.nasa.gov/news/mmu/in...&NewsID=109

New and improved data processing software, that ought to be able to work across multiple quarters. Apparently the old software could only work on one quarter's worth at a time. That explains a lot!

--Greg
Greg Hullender
Another Manager's update: http://www.kepler.arc.nasa.gov/news/mmu/in...&NewsID=110

Another safe-mode event, and they're still working on it. Does it seem like Kepler has more of these than other craft, or are they just better about reporting them?

--Greg
Syrinx
Kepler definitely has them more frequently. I believe it's due to hardware differences.

I hate to say something not true, but at one of the lectures here in the Bay Area I vaguely remember somebody claiming it is due to an old star tracker. Again, I'm not sure about that. What I do remember is thinking that if there was ever a Kepler 2 that it would be trivial to solve with modern hardware.
djellison
That very subject has been discussed in this very thread already.
Syrinx
Back online.

http://www.nasa.gov/mission_pages/kepler/n...m-20110321.html

Hopefully this was the "safe event to end all safe events" (the new firmware will cure the star tracker issue).
ngunn
I'm not sure when this amazing digram was first released. Possibly someone has already posted a more direct link to it. Anyhow I've only just spotted it on yesterday's APOD, so for anyone else who hasn't already seen it here it is: http://apod.nasa.gov/apod/ap110329.html
Explorer1
Amazing!
Roger Ebert posted it too (not perfectly described, but nice to see it shown anyway): http://blogs.suntimes.com/ebert/2011/03/a_...ce_of_dust.html
nprev
It's a profound image indeed, and it will resonate. wink.gif
DFinfrock
QUOTE (nprev @ Mar 31 2011, 06:00 AM) *
It's a profound image indeed, and it will resonate. wink.gif


Yes it will. It points out how very average and run-of-the mill our sun and Jupiter are. In the big scheme of things, our solar system is nothing special.
eoincampbell
Thank you very much, ngunn for bringing that brilliant illustration to light!, I'm eclipsed! smile.gif
Syrinx
QUOTE (DFinfrock @ Mar 31 2011, 02:32 PM) *
In the big scheme of things, our solar system is nothing special.

Your succinct statement is utterly depressing and amazingly inspiring, simultaneously. Here we are alive in 2011 between "ignorant" and "able". All we have is UMSF smile.gif.
stevesliva
Kepler releases on at least two of the three:

Echoes from depth of Red Giant
Triply Eclipsing Triple Star System

Edit, make that 3/3:
Kepler listens to chorus of stars
marsophile
Is there any way that Kepler could detect an asteroid belt (analogous to the one between Mars and Jupiter) around other stars? That may not be directly observable via the transit method, but is there any way of obtaining indirect evidence?
Drkskywxlt
QUOTE (marsophile @ Apr 11 2011, 11:29 AM) *
Is there any way that Kepler could detect an asteroid belt (analogous to the one between Mars and Jupiter) around other stars? That may not be directly observable via the transit method, but is there any way of obtaining indirect evidence?


I don't think so...several studies have looked at whether Kepler could detect moons, rings or trojans of any detected planets, and the answer is more or less "yes given certain conditions" (e.g., very large moon/trojan-to-planet ratio) with either direct imaging or transit-timing variations. If you had an Earth analogue with an asteroid-belt analogue, without doing the math to confirm, I'd wager big money that there's very little variation in Earth's orbit due to asteroids. I'm not sure even Jupiter could be inferred if an alien Kepler was looking at transit timing variations of Earth.

Not to mention you'd need a large sample of transits to build up a statistically significant sample, and for an Earth analogue, Kepler probably will only get ~3 transits.
Hungry4info
QUOTE (Drkskywxlt @ Apr 11 2011, 10:41 AM) *
I'm not sure even Jupiter could be inferred if an alien Kepler was looking at transit timing variations of Earth.
Only because of Jupiter's long orbital period. Given a long-enough baseline, the transit timing variations would be detectable, I believe.
Drkskywxlt
Exactly. Over a nominal 3-5 year mission, you couldn't detect variations from Jupiter. I don't know how long you'd exactly need, but it would have to be at least 10-15 years to get 2-3 orbits of Jupiter "observed".
stevesliva
Any earthish planets with an annual occultation would certainly be watched after the mission end. Why does the mission timeframe matter for ferreting out that sort of thing?
NGC3314
QUOTE (stevesliva @ Apr 11 2011, 01:23 PM) *
Why does the mission timeframe matter for ferreting out that sort of thing?


At the moment, nobody has figured out a way to get the photometric precision needed to detect Earth-sized planetary transits against Sun-sized stars from the ground (atmospheric scintillation is a major limiting factor). Kepler or a successor would be the only game in town. On the other hand, if you already had a list of target stars and potential transit times, a less complex and much lower data-rate followup might be able to pick up the search - but compared to that, keeping Kepler going seems like a really powerful thing, especially since it has (AFAIK) no consumables to limit the mission duration.
stevesliva
Huh. Wouldn't have guessed the ground was quite that hopeless! I'm of course not augering for an early demise for Kepler, just curious. I guess my misunderstanding all along was not that Kepler was necessarily much more precise than, say, Keck, but that Kepler could just stare away and find these things, rather than looking at rain on Titan.

What sort of spacecraft cameras could do the trick? WISE, Deep Impact, Spitzer...? Thinking along the same lines that once these planets are discovered, their transits could be well observed by something else not dedicated to the task. I'll be somewhat shocked if Kepler and Corot(?) are fairly unique.
Hungry4info
WISE is out of comission, Deep Impact lacks the accuracy needed (their constraints to additional planets in known hot Jupiter systems ruled out planets down to ~Neptune radii, and these systems are much brighter than Kepler targets). Spitzer could probably detect it for Earth-size planets orbiting smaller stars, HST maybe.

Other than that, yeah, just Kepler and maybe CoRoT.
siravan
QUOTE (NGC3314 @ Apr 11 2011, 10:40 PM) *
...since it has (AFAIK) no consumables to limit the mission duration.


Actually, Kepler - as any 3-axis stabilized spacecraft - has hydrazine thrusters to desaturate the reaction wheels. I think the post launch estimate was that there is enough hydrazine onboard for a 6+ year mission.


djellison
And all spacecraft have a consumable that they all need that is very limited. Cash.
Greg Hullender
I'm trying to think of a successful mission that wasn't allowed to have an XM, though. For cost-effectiveness, running new experiments on already-orbited hardware is very hard to beat.

In Kepler's case, though, I could see it being a hard sell. More time makes it easier to see more remote planets, but the geometry of the problem makes those much less likely to see in the first place. Of course, as others have mentioned, more time gives you more chances to learn about other planets through their effect on the orbits of the ones already measured. I guess we'll see, but, even so, I'll be surprised if they can't get an XM approved, as long as the vehicle is still working reasonably well.

--Greg
siravan
In a sense, the problem is that observing the same field follows the law of diminishing return. One possible option for XM is that Kepler targets a new star field all together. It is a trade-off between possibility of detecting few long-period planets (which, of course, are of great interest) versus detecting lots of short-period planets/hot Jupiters (which improves planet frequency statistics).
Syrinx
- Bill Borucki himself has said they will almost certainly win an extended mission. How extended, he did not precisely say. In the context of the discussion it seemed it would be 2-3 years in duration.

- Kepler won't point at a different star field. Kepler takes advantage of star knowledge obtained from ground-based observatories. The current star field was studied for literally years before Kepler was launched.

- Every lecture that I attend it seems like the estimated time to fuel exhaustion (not mission duration) pushes later by a year or two. At first it was three years, then six, then seven, and the last lecture at Stanford Natalie Batalha said up to 10 years.
Gsnorgathon
I'm guessing that staring at the same star field longer also increases the s/n, which makes spotting smaller planets (and maybe even moons) more likely. And lets not forget that Kepler can teach us a lot about stars, too!
NGC3314
QUOTE (siravan @ Apr 12 2011, 06:01 AM) *
Kepler - as any 3-axis stabilized spacecraft - has hydrazine thrusters to desaturate the reaction wheels.


Ahh, right. Good thing I qualified that. (A further qualification is "any 3-axis stabilized craft outside the geomagnetic field", anyway, since HST does fine managing the reaction wheels with that, and some even manage to do their pointing that way).

A mission extension would make much more sense at the original field, since that gets us new kinds of information (larger orbits) rather than better statistics in a regime already probed.
Hungry4info
Not to mention a longer baseline for transit timing variation measurements to discover more non-transiting planets and measure the mass of some who do, but are difficult to detect with radial velocity.
scalbers
Catching up on things I noticed an interesting chart of Kepler candidates in the May Sky and Telescope. It shows quite a few planets less than Earth radius (up to about 40 days orbital period). Some are actually down to around 0.1 radius. That's pretty small - perhaps the parent star is also a smaller radius to give a good S/N ratio? Here is a similar chart online (also shown in post #730):

http://arstechnica.com/science/news/2011/0...-candidates.ars

It would follow that given a longer period of monitoring there would very likely be some Earth Sized planets with 1 year orbital period. We'll see if it's around a sunlike star too.
Rob Pinnegar
QUOTE (scalbers @ Apr 24 2011, 04:54 PM) *
Some are actually down to around 0.1 radius. That's pretty small - perhaps the parent star is also a smaller radius to give a good S/N ratio?


That'd be my guess too. Some of the least massive known red dwarfs aren't that much bigger than Jupiter in terms of radius.

It's not difficult to picture something with 80-90 Jupiter masses having planets at least as large as the Galileans. If a star were to have one-ten-thousandth of the Sun's luminosity, planets circling at distances corresponding to the orbits of the Galileans around Jupiter would have surface temperatures roughly comparable to those of the planets of the inner Solar System. I'm no expert on planetary formation, but one would think that rocky bodies ought to be able to form at those kinds of temperatures. As a bonus, they would be close enough to their parent star to make eclipse-viewing geometry pretty favourable.

What would be *really* neat would be a hot (warm?) Jupiter in a relatively close orbit around this kind of red dwarf. Something like that might actually be larger than its primary in spite of being much less massive. It might be able to completely eclipse the primary. I wonder if a system like this would be stable, in the sense that the planet wouldn't start losing mass to the red dwarf (thereby shrinking)?

EDIT: fixed a mistake (see below... thanks Greg).
Hungry4info
One could just look through the paper that listed all 1,235 planet candidates, their radii, and the radii of their host stars...
http://arxiv.org/abs/1102.0541

It's pretty clear the graph is just drawn poorly. Here's a better graph by Mongo with planetary radius being the x-axis and equilibrium temperature on the y-axis.
http://solar-flux.forumandco.com/t282p465-...nd-results#5802

The smallest observed planet candidates have radii at 0.7 RE.
Greg Hullender
QUOTE (Rob Pinnegar @ Apr 26 2011, 04:09 PM) *
It's not difficult to picture something with 80-90 solar masses having planets at least as large as the Galileans. If a star were to have one-ten-thousandth of the Sun's luminosity . . .

I think a star with 80 times the mass of the sun but only one ten-thousandth the luminosity just isn't trying very hard.



--Greg :-)
dilo
Sorry for silly question, why I still cannot see >1000 Kepler planets on any public Exoplanet database like following ones?
http://exoplanets.org/
http://exoplanet.eu/index.php
http://planetquest.jpl.nasa.gov/
Perhaps because they still unconfirmed "candidates" or what else?
Moreover, I see lot of posts containing data/plots with these candidates, where can I find original source?
centsworth_II
QUOTE (dilo @ Apr 27 2011, 01:24 PM) *
....still unconfirmed "candidates" or what else?

That seems to be what the third site you link is saying in a March 7, 2011 news release.
"All of Kepler's candidate planets await verification from ground-based observatories."
dilo
Thanks, centsworth_II, I missed it... in the meantime, I found also the candidates list:
http://kepler.nasa.gov/Mission/discoveries/candidates/
Hungry4info
QUOTE ("dilo")
Moreover, I see lot of posts containing data/plots with these candidates, where can I find original source?


QUOTE ("Hungry4info")
One could just look through the paper that listed all 1,235 planet candidates, their radii, and the radii of their host stars...
http://arxiv.org/abs/1102.0541
Rob Pinnegar
QUOTE (Greg Hullender @ Apr 27 2011, 07:48 AM) *
I think a star with 80 times the mass of the sun but only one ten-thousandth the luminosity just isn't trying very hard.


Dahhh!!! I meant 80 Jupiter masses, of course. This has been fixed, for what it's worth.
ngunn
I've been similarly confused many times. Earth mass Jupiter mass and Solar mass are all regularly used as units for exoplanets and brown dwarfs. They're on a par with 'an area the size of Wales'. How many people actually know the conversions between them? It's a pain. Let's stick to kg.
AndyG
300 Earths is near enough a Jupiter, and 1000 Jupiters just about 1 Sol. It seems to me that Jupiter is reasonably well-placed for defining the relative masses of BDs, smaller stars and giant exoplanets.

The problem with kg is with those pesky scientific notations, and the ease of which you can mentally miscalculate by a magnitude (or two)!

Andy
Habitable Zoner
As most have heard by now, there have been at least two interesting Kepler announcements at the AAS 218 meeting, one dealing with the abundance of multi-planet systems, the other an announcement of the hot super-earth Kepler 10c. The press releases are available on the Kepler website. The first announcement, "Keplerís Astounding Haul of Multiple Planet Systems," has a very cool animation showing the systems. The second, "Kepler-10c and a New Method to Validate Planets," discusses the Blender technique of validating candidates. Archives of the presentations, including slides, are available on the site.
Tom Tamlyn
QUOTE (centsworth_II @ Apr 27 2011, 01:56 PM) *
That seems to be what the third site you link is saying in a March 7, 2011 news release.
"All of Kepler's candidate planets await verification from ground-based observatories."

"All our candidates is belong to ...."

TTT (sorry)


Greg Hullender
This article (refered to in the links above) has an excellent account of what they do to try to validate a candidate planet.

http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.4647v1.pdf

I feel I have a much better understanding of why it takes them so long, but it also sounds like (from this and some of the other papers) they've got the hang of it now, so I expect we'll see results coming more quickly now.

But there's some GREAT stuff here!

--Greg
Syrinx
Not strictly Kepler related, but MIT recently hosted distinguished speakers who each gave short presentations on the topic of exoplanets. The presentations were recorded and are available for streaming.

http://amps-web.amps.ms.mit.edu/public/EAP...oPlanets-may27/

There are four videos, each about an hour in duration. I've watched the first two. The second video ("Stars and Planets Within our Reach") features Geoff Marcy's opinions on TPF / the decadal survey / NASA in general, and also Sara Seager's CubeSat program "ExoplanetSat" of which I was not previously aware.
Syrinx
Mission Manager Update arrived today:

http://www.nasa.gov/mission_pages/kepler/n...m-20110617.html

QUOTE
The health of the spacecraft and photometer, the instrument used to measure changes in the brightness of distant stars, is excellent and has recorded more than two months of routine operations in this quarter. The observing efficiency in Quarter 9, which is April through June 2011, has been above 97 percent due to two very efficient monthly science data downlinks in April and May-- 16.6 hours and 15.2 hours, the quickest yet! Coupled with no unplanned breaks in collecting science data, it has been a strong quarter so far. [...]

performance of Ka band downlink between the spacecraft and the Deep Space Network ground stations has been excellent. Greater than 99 percent of science data reaches the ground on the first attempt. [...]

in May, the team completed a file uplink to the spacecraft to mitigate the root causes of the anomalies encountered during Quarter 8 operations. [...]

To date, the downlink rate operates at the maximum Ka band rate of 4.3 Mbps. [...]

The latest estimates show the spacecraft is equipped with enough propellant for the thrusters to last for an additional eight years.
Drkskywxlt
Eight years!?! blink.gif

Awesome! cool.gif
nprev
Yes, that's exciting news! We should have a VERY good dataset by end of mission, and ultimately a much more accurate estimate of planetary population than we'd hoped.

Good times, good times.
ElkGroveDan
Here's to our Kepler and eight more years of successful Kepling!
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