Consider Uranus, and entire system tipped 90 degrees relative to our star. Pancake-shaped systems might be the exception?

The assumption arises out of a rejection of anthropocentric ideas of the Universe. If the planet-planet inclinations in transiting systems are different then planet-planet inclinations in non-transiting systems, then there is something fundamentally different about planet formation in systems that are aligned a certain way relative to Earth, at this certain moment in time.

I think it is safe to reject this idea.

Put simply: there is no reason to expect transiting and non-transiting systems to be intrinsically different.

Let me put it another way. Your diagram above shows the chord transiting planet (as distinct from the one crossing the diameter) as crossing on a path parallel to the planet crossing at the diameter. But neither you nor Kepler have any way knowing (at least that I know of, or has been demonstrated yet) that that is in fact the case. In actuality, the two planes might be perpendicular to each other and, again, neither you nor Kepler could know whether THAT is the case or not. If there is some way to KNOW the planets MUST be nearly coplanar, and not simply ASSUME it, that's what I'd like to know. Indeed, to assume that they are is in fact to hold to the anthropocentric principle because it's based on what we've seen in our one system.

And to go further, even if you some how KNOW that two are in fact coplanar, what prevents there from being any number of other planets in highly inclined orbits in the same system that would therefore be NOT transiting and therefor not detectable by Kepler?

Yes it's possible that a multi-planet system only appears well aligned and only transit at their nodes, however you would then expect secular interactions to produce very visible transit timing and transit duration variations. Furthermore, only a small percentage of multiplanet systems will transit right at the nodes, in such a way that the impact parameter will behave as we expect (decreasing for longer periods).

Stability arguments would require them to orbit further out then, and I agree fully with JRehling here:

"BUT, any Kepler results are confined to inner systems, which includes planets whose orbits are tidally influenced by the star's rotation. This need not apply to planets further out."

Obviously, the completeness of our understanding of planetary system architecture from transits decays with increasing semi-major axis.

OK, we're making progress here. What I described was indeed a system with two planets in it in perpendicular planes and where the intersection of the two plane happened to point right at us. I agree that even if planetary systems had planets whizzing around like electrons around the old Bohr atom, such alignments would be rare. And it would also be true that the gravitational interactions (is that what you mean by "secular interactions"?) would most probably produce observable differences int the difference and timing of transits that could discriminate between the two possibilities. However, if that calculation was made and was part of the evidence for "pancake" systems, it wasn't mentioned in the brief. However I'm pretty sure that FOR THE SYSTEMS SHOWN, such calculations have in been done, because variations in transit times are seen as evidence that additional planets are in the system. However, none of this solves the problem anyway.

Kepler and Doppler studies both have a bias in favor of larger planets with short periods (which probably are "tidally influenced by the star's rotation", but that's not the basis of the bias.) Further, both have a bias in favor of planetary orbital planes the intersect earth. Kepler can ONLY detect such planets and the observable Doppler shift goes to 0 for planets, no matter how large or close in, in orbits perpendicular to our line of sight. These facts are well known and exactly why I STILL don't understand how Frank has CALCULATED the flatness of planetary systems.

Although it is true that the information available about exoplanetary architecture mainly applies to planets close to their stars (and, I'm willing to bet, their may be dynamical models of planetary interactions that severely limit, if not exclude, non coplanar planets in close to a star) it's the very fact that these limitations are known to exist that make me very uncertain what, exactly, is being claimed by Frank's article.

Put another way, how does she claim to constrain the inclination of orbits of planets about which we (apparently) know nothing?

I am not exactly sure what specifically you are confused about, so let me try to state what is known in as clear and concise a manor as I can.

I think the most accurate way to state it is that multi-planetary systems like those Kepler is sensitive to -- not exclusively ones Kepler can detect, but rather the typical system of several low-mass planets in periods < 200 days -- have minimum mutual inclinations that are very low, consistent with being very coplanar. Yes there are degeneracies that can prevent you from knowing the true mutual inclination, but statistical arguments alone imply that a great deal of the systems we see are truly rather coplanar.

As a singular test example, the Kepler-30 system is found to be well-aligned and coplanar based on the detection of transits of planets across star spots.
http://arxiv.org/abs/1207.5804

(and yes gravitational perturbations = secular interactions.)

I'll try to make this as simple as possible.

In the presence of noise and with sparse data, it is certainly a challenge to determine the typical flatness. But with enough and good enough data, it is definitely possible in principle. Consider the following ideal situation:

We have a vast number of systems which contain one planet with a period arbitrarily close to 50 days, and that planet transits right through the middle of the star's disc (which we can determine by the transit duration).

Now we consider these systems in terms of inner planets (or lack thereof) with a period of 25 days. In each system we either find or do not find such a planet. If we do find one, we can measure the impact (distance of the transit alignment from going right through the middle of the star's disc) on the basis of the transit duration. If we do not find such a planet, we can't know whether or not there's one which fails to transit or if there is none at all.

The data we CAN collect is the distribution of impacts for the inner planet where there is a transiting inner planet.

If the flatness of all systems is absolute, then all such inner impacts will be, like the impact of the outer planet, zero. It must be in the exact same planet.

If the flatness of all systems is as non-flat as possible, then the observed transits will display a completely flat distribution (and moreover, be very rare). We will see the inner planet display an impact of zero in the extremely small fraction of cases where the orbits either happen to be coplanar or non-coplanar orbits happen to cross our line of sight.

The distribution of impacts for the observed inner planets will tell us where in between these two extremes actual systems lie.

Now, to revoke those assumptions: We would never find so many systems with such precise constraints, so the analysis is complicated by allowing the varied periods of all observed systems. And we have serious errors in calculating impact precisely, because of observational noise (in luminosity as well as time) and because stellar parameters are uncertain. Finally, as I noted earlier, we can only gauge such work as valid for the types of systems and periods we observe. We have no proof that it won't be considerably otherwise for longer periods.

So I don't necessarily see as obvious if/that it is possible in practice, but it is definitely possible in principle.

I think I understand your argument, but need clarity about a few points first.

Could you be more precise about the distribution of impacts in the "non-flat" as possible case? What do you mean by a "flat distribution" in this case? Linear? Gaussian?

Also, I assume by "non-flat as possible" you mean that the observed planets transit the star. Is that correct? If not, what, precisely, do you mean by non-flat as possible flatness?

Finally, doesn't the argument you put forth REQUIRE the assumption that the (unobservable) paths of the observed transits of the 25 day period planets are parallel to the (unobserved/unobservable) path of the 50 day period planet?

Thanks

Also, I want to make clear that I do not doubt that some of the observed multi-planet systems (i.e., those planets that have been observed) are in fact nearly co-planar. It is generalizing those results to other planetary systems, or indeed to other planets in those systems that, as far as I understand, MIGHT exist, but not be observable by Kepler (since they don't transit). This is what the report seemed to me to be implying, though I could be wrong about that too.

I think the difficulty in picturing 3D spatial geometry creates snags.

Even if two planets' orbits around the star are non-coplanar,even if they were at right angles, there is a probability that they will both transit as seen from Earth. I think this may be the elusive fact. For some observer s(in either of two directions which are separated from one another by 180 degrees) both Earth and Pluto will appear to transit the Sun, even though the orbits of Earth and Pluto are non-coplanar. The coplanarity governs the probability that an observer will see both transit, not that they may or may not.

And given impact=0 for the first planet, A, we consider, coplanarity will determine the distribution of the impacts for the second planet, B. If the orbits in all systems are perfectly coplanar, and impactA=0, then impactB=0. If the orbits were always at right angles, then the distribution of impactB would be flat: It would just as likely be 0.8 as 0.4 as 0.2 as 0. So the observed distribution will tell us precisely how coplanar or non-coplanar the orbits are across all systems.

Could transiting a fast-rotating star give an opportunity to determine the angle crossed by the planet? Second order effects, such as the shape of the entry/exit curve could determine the location of the entry, the speed of entry could determine the length, and the two taken together could provide information on the angle the planet takes with respect to the centroid of the star. A planet diving straight vertical across the star would have a transit time similar to a planet at some latitude north/south of the star's equator. However, the entry curve of the vertical planet would be more abrupt, while the horizontal planet more gradual.

Yes indeed. Look at KOI-13 for an example of a planet transiting a rapidly rotating, oblate star.
http://arxiv.org/abs/1105.2524

It hasn't come up for a while in this thread (IIRC), but the Rossiter-Mclaughlin effect is measurable in many transiting systems (of Jupiter size, anyway). This is the change in a star's mean Doppler shift as the planet covers up portions of it at varying locations. The sign and amplitude of the effect (which can be many times larger than the Doppler signature caused by the perturbation from the planet) tells the angle between the stellar equator and planetary orbit, and can also distinguish planet transits at such a steep angle that they only ever cross the star's leading or trailing half. The remaining uncertainty is the star's axial inclination to us, where there is some information from the rotational line broadening.

For the recently-reported PH1 system around an eclipsing binary, there was the interesting wrinkle that the sense of the correlation between transit times and phase of the central eclipsing binary (and a similar correlation with transit duration) says that the planet orbit has to be roughly aligned with the binary orbit. Unfortunately, the secondary star is too faint for Kepler to see transits against it alone, which would nail down whether they are coplanar at the 2-degree level or so.

New analysis of close in planets around M dwarfs suggest over 100 billion such planets exist in our galaxy.

http://arxiv.org/pdf/1301.0023v1.pdf

It seems that a majority of planets in the Milky Way orbit M dwarfs.

This result, which has been echoed in the mainstream media the past few days, certainly needs a bit more qualification than it's getting. Kepler has thus far told us next to nothing about planets with periods >500d (where, as a point of reference, most of the solar system's planets exist) so it is not even capable of telling us anything about a total number of planets per stellar class... unless that conclusion is qualified with a period threshold.

The fact that M dwarf stars outnumber other stellar classes, however, makes it "easy" for the claim to hold true that they collectively hold most of the planets. They could have fewer than half as many planets per star and that would still be true.

We may also note the microlensing survey by [Cassan et al. 2012] which found 1.6 planets per K-M star including only Super Earths and larger at distances 0.5-10.0 AU. Adding in such planets found inside 0.5 AU is likely to raise the total to about 2 planets per star and including smaller planets is likely to raise the total considerably.

I'm interested to see the details here about origins beyond the ice line for planets of this size. [Ida & Lin, 2010] hypothesize that embryos (solid protoplanetary bodies smaller than the Earth... how small depends on the model) migrate inwards from about 2 AU to about 0.5 AU. This would create a relative dearth of Super Earths in that zone, which of course is of great interest because of the whole "Eta Earth" question. Would it mean that Earths are more or less common in that zone? I don't think the models are sufficiently well-validated to say. [Mayor et al, 2011] found a relative dearth of Super Earths in that range based on the HARPS radial velocity survey whereas [Dong and Zhu, 2012] found no such dearth in the Q1-Q6 Kepler data. I plan on performing an analysis of the Q1-Q8 data when it's released which should answer the question. If HARPS and Kepler find differences, note that it is always possible that there is an important difference in the samples, namely that HARPS probably observes more high-metal stars and Kepler more low-metal stars.

The next few months will be very interesting.

I wouldn't say it has found nothing per-se. Places like Planet Finders have found some interesting transits but it may not be possible for them to become bona fide candidates before the end of the mission.

Forgive me, but the more I hear people talking about the ice line the less I believe we have a solid concept of it yet. I don't perceive it as a rigid barrier any more. Icy material is perfectly capable of interacting with terrestrial material, especially in the presence of massive bodies like planets. This has implications for water worlds because how I see it there are two different ways to form one. One is that the planet can form in stu and acquire water by accretion of planetesimals or by out gassing. Or an icy planet can form beyond the snow line and then migrate inward until its crust melts. We don't know yet how large terrestrial planets or Super-earths can get before there is a transition from a rocky crust to a fluid one because there is no example in the solar system we can study.

Now I am not a scientist, but I feel the reason there are no icy planets or hot Neptunes in the solar system is because of Jupiter. Jupiter has always been the most massive gas giant in the solar system well as the most inward one. I feel the second characteristic is the most important one. Imagine a solar system without a Jupiter analog. In the place of Jupiter many icy and Neptune sized planets would form. These would gravitationally interact with each other and start migrating. This would in turn lead to the terrestrial portion of the system being influenced, especially so if any icy planet migrated into the region. If a Jupiter sized planet were to form further out than our Jupiter did there would still plenty of icy material at the inner part of the ice line to form planets. In fact it may magnify the effect.

I feel my hypothesis explains explains what were seeing from Kepler. Neptunes, sub-Neptunes and icy planets are very common. In our solar system Jupiter acted as the gravitational blockage that prevented the chaos that was occurring across the ice line from entering the terrestrial system. Who knows what happens without a Jupiter analogue.

Just to make clear what the ice line is, in the context of planetary formation: It means the boundary in the protoplanetary nebula outside of which small particles of water ice are stable and within which small particles of water ice are not. Outside the line, H2O ice is a major component of the nascent accumulating bodies. Inside the line, it may be a gas, but not a solid, so it is not retained as a bulk component of very small bodies. The sizes we're talking about here range from milllimeters up to the size of the Moon or bigger.

There may be some modest complexity governing where that line is for a given system, but there's not much room for controversy, so far as I can see, that there *is* such a line (or more properly, a spherical surface). In fact, there is a "line" for every substance: Rock experiences this at orbital periods of about 1.5 days for a sunlike star. For ice, it's at about 2.7 AU.

For larger worlds, certainly, there is a lot of diversity we know of and sure to be more diversity in other stellar systems. We may find ice surprisingly far inside it (e.g., Mercury) and we may find warmer worlds surprisingly far outside of it (Io and Europa). But in terms of the nebula, it's largely a matter of radiative heating and the states of H2O.

NASA has announced 461 new planet candidates today.

Here's a scorecard on the most recent Kepler releases. There are some big differences in the state of the analyses:

1) Feb 2011: Planetary candidates from the first 4 months of data. This list has a low rate of false positives and gives a pretty good survey of the distributions of planets with periods under 50 days. Great analysis in [Howard, et al. 2011]

2) Feb 2012: Planetary candidates from the first 16 months of data (Q1-Q6 observations). This list has a low rate of false positives and makes possible a pretty good survey of the distributions of planets with periods under ~250 days. I've spent a long time looking at this, and an analysis [Dong and Zhu, 2012] is on arxiv
http://arxiv.org/abs/1212.4853
This hasn't passed peer review yet, and it's worth looking at the difference between their conclusions about Neptunes with periods in the hundreds of days and those of [Mayor, et al. 2011] from the HARPS survey.

3) Jan 2013: ~3500 Planetary candidates from the first 22 months of data (Q1-Q8 observations). This list has a low rate of false positives and makes possible a pretty good survey of the distributions of planets with periods under ~400 days. It just came out yesterday.

4) Dec 2012: ~18,000 Threshold Crossing Events (TCEs) from the first 34 months of data (Q1-Q12 observations). This list has a high rate of false positives and presents some challenges in the cleanup. Most false positives identified so far have been binary stars, but the TCEs show some artifacts that are clearly operational in nature with no plausible astrophysical explanation. This list contains several objects that imply planets that closely resemble the Earth in size and period and/or equilibrium temperature, which has received some attention in the media. However, no single one such TCE is guaranteed to exist, and in fact, each individually is probably more likely to be a false positive than real, so the forthcoming cleanup is very important, and until that is done, we have no reason to speak of the TCEs which aren't in the January 2013 release as discoveries in any sense.

Kepler has completed 15 quarters of observations (~42 months), during which each star has been observed about 90% of the time, but the data after Q12 has not yet been released in the form of candidates or TCEs.

The next few months should be very interesting, because the data is on the ground awaiting analysis and as that progresses, a rush of discovery may follow, which may include result speaking fairly directly on the Eta Earth question: the abundance of planets with sizes and temperatures like the Earth.

Kepler have changed our perspective in a major way, from the initial discoveries where many were hot Jupiters, to the data we have here where Jupiter class planets in the inner part of planetary systems apparently are not as common as initially assumed, but planets of the 'super Earths' and Neptune class are the most common.

Yet one can see that in the graph at bottom, the number of datapoints thin out quite some for orbits over 200 days.
And the majority of the few that are there happen to be yellow- meaning the results are just in. So we will have to wait some more to learn how many inner-solar system analogues there might be to be found.
Yet it will be for the inner planetary systems only, since Kepler would have to keep observing for 24 years to confirm gas giant planets at a similar distance as our Jupiter and ~60 years for one analogue of Saturn.
So just like with the first searches for extrasolar planets, also Kepler will bring data that are won't tell the whole story - not that I am in any way complaining. Kepler have already been tremendously successful and already have achieved more than what I expected.

Every method of exoplanet discovery has biases, and the completeness of detections drops off to zero for unfavorable regions of parameter space (defined most importantly in terms of distance from star to planet and planet size). Kepler comparatively excels at finding relatively small planets relatively close to the star, and leaves relatively little uncertainty regarding the orbital inclination of detected planets. Radial velocity surveys excel at finding larger planets but leave considerable uncertainty regarding orbital inclination.

Kepler may potentially detect a Saturn analogue given only a single transit, and then the duration of the transit gives a measure of the star-planet distance, but this leaves a large uncertainty regarding the orbital characteristics. However, the RV method is better than the transiting method for finding large exoplanets in orbits of several AU anyway.

A nice synergy from Kepler's discoveries of large planets is that we may verify them with the RV method and this will give us data on the radius-mass distribution, for which we have excellent data for the solar system's cases, which already show us the nonmonotonicity of density as a function of radius.

For smaller planets, Kepler is showing us the distribution out to about 100 days as of Q6, and may show us out to about 400 days as of Q12 or Q15. The TCEs for Q1-Q12 have the potential to have found, already, earth-sized planets in earth-like orbits (or, around cooler stars, at earthlike temperatures with orbits of much shorter periods), but the TCE list is sure to have a high rate of false positives; grappling with that will be an interesting feat in the coming months.

It may be a long time before we are able to detect earth-sized planets in outer (>~2 AU) orbits or obtain more than sporadic discoveries of large planets in orbits much beyond 10 AU. But within those limits, I think we'll soon have a good notion of what typical planetary systems are like. In fact, for large planets within 10 AU, that knowledge is already here, although the samples of stellar class differ from study to study, and that's an additional factor that will be nice to account for.

It's worth noting that of the closest sunlike stars, we now have evidence of planets around Alpha Centauri, Epsilon Eridani, and Tau Ceti. I expect that we will soon feel assured that the number of planets per star is typically several, and we'll have a good characterization of what variety of sizes and distances are typical. The accumulation of more detailed information about exoplanets has already begun. Exoplanet science is at about the same state now that solar system observation was about 400 years ago.

Very well stated, Mr Rehling!

Has Kepler found any previously undiscovered stars in its field of view? d'ohh - according to this page linked from NASA's Kepler site, 2708 eclipsing binary systems have been recorded.

How about faint, lonely stars? Today's published articles about earth-like planets orbiting red dwarf stars has led me to wonder...

Kepler only returns data from from the parts of the sensor where the targets are, so in general, Kepler not going to detect unknown stars (except for EBs, where a "target" turns out to be more than one star.) Follow-up observations do find previously uncatalogued objects, because they look for contaminating signals that are too close to the target to be resolved by Kepler. That includes previously unresolved stellar companions and background objects.

As I slowly digest the last few months' Kepler data/publications, I note the following:

1) The planetary candidates from Q1-Q6 observations have been analyzed for intrinsic planetary frequency by
[Dong and Zhu, 2012] http://arxiv.org/pdf/1212.4853.pdf
and
[Fressin et al, 2013] http://arxiv.org/abs/1301.0842

The latter contains a new caveat regarding Kepler results, that the rate of false positives is likely higher than had been anticipated, meaning that the assumption that the count of Kepler candidates is about the same as the rate of actual planets (within some epsilon) is not so sound. Therefore, the uncertainty of estimates of intrinsic frequencies is considerably higher than earlier claims, and (pertinent to my interest) it is particularly harder to discuss intrinsic frequencies as a function of stellar properties.

Relevant to the last two posts on this thread: The major sources of false positives, once other sources of noise have been eliminated, all concern multiple stars in the same pixel as the star in question. False positives result when a transit (of a star by a star or a planet) occurs around a secondary star (either a bound component of a binary/triple or background star). For example, if a Jupiter-sized planet transits a background star that contributes only 1% of the light falling on that pixel, it creates the same signal as if an Earth-sized planet were transiting the star that contributes 99% of the light falling on the pixel. It may be very difficult to identify these on a case-by-case basis; it is easier to estimate the rate of occurrence of false positives and then proceed to analyze the intrinsic frequencies of planets without knowing which candidates are really what they seem to be.

2) The January 2013 release of candidates for Q1-Q8 is not complete in a principled way, so it cannot be used to perform the same kind of analyses as February 2012's release of candidates for Q1-Q6.

3) The December 2012 release of TCEs for Q1-Q12, which are events that have not yet been screened for false positives has some data artifacts that have not yet been characterized. The data release notes the anomalies, but it appears that accounting for them has yet to happen.

To be more specific: The completeness of observations for the transiting method decreases for longer orbital periods, because (among other reasons) the geometry of alignment is less favorable for orbits farther from the star. So we should expect that detected planets will show a period distribution clustered tightly to the star, because the close-in planets transit with a rate of some 5-30%, whereas at Earth's distance from the Sun, this drops to about 0.5%, and for Jupiter 0.1%, etc.

However (!) the TCE list shows a spike in frequency for objects with a period of about a year and sizes about that of Earth. (Exactly what Star Trek would have you believe.) This is highly contrary to the trends seen at shorter periods, and is definitely due to artifacts in the process.

I've analyzed those, prompted by observations in the release, and noticed this: Although there are 21 modules of detectors in Kepler's telescope (arranged in a 5x5 grid with the corners missing, hence 21), 37% of those seemingly habitable Earths were detected exclusively by 1 of the modules, and 64% of them were detected by 3 of the 21 modules. Moreover, Kepler rotates 90 degrees every quarter, so this cannot be explained by different portions of the Kepler field being richer in habitable Earths than the others. The same modules find lots of habitable Earth TCEs in whichever of the four sectors of the field they are observing, and when other modules monitor the same sector of the field, they don't find many habitable Earth TCEs. In essence, it seems that there are "hot" modules producing false positives of Earth size. A fact corroborating this is that in many cases, the same star has multiple Earth-sized TCEs with period varying by suspiciously small amounts (e.g., 4%). This false-TCE problem spikes for periods of about a year because that is the cycle on which the same module returns to observe the same stars. (Coincidentally, the hottest module and one of the two "warm" modules are 180 degrees opposite one another, so there is also an anomalous detection of six-month-period TCEs.)

Whatever is going on there, it can be compensated for by raising the level of signal-to-noise ratio one requires to promote a TCE to planetary candidate status. Whereas a threshold of SNR>7.1 was used in earlier work, many of these anomalous habitable Earth TCEs have SNRs>7 and some have SNR>10. (Fressin, et al), without discussing this in particular, analyze the SNR requirement and suggest that a threshold of 16 is necessary to eliminate false positives. But this (perhaps necessarily) throws out the baby with the bathwater: There are almost no Earth-sized TCEs detected in Kepler's Q1-Q12 data with SNR>16 and periods longer than 35d! This is one of the issues making the mission extension (already approved) so crucial: If 2.5 years of observations could only detect Earths with periods of about 30d, then we may be able to detect Earths at longer periods (even 100d) given a large number of transits.

Alternately, taking into account how hot each module is may allow us to assign different SNR thresholds to each of them, which could give us more usable data than if we use an SNR threshold that is safe for the hottest of the modules.

Since most of the stars in Kepler's view are Red Dwarfs, an earth-sized planet in a 100-day orbit would be a very tantalizing discovery!

Depends on the star's actual mass & temp. Pretty sure that some theoretical hab zones were mentioned for 50-day orbits. Might be considerable variation there in terms of percentages.

Relatively few of the stars observed by Kepler are red dwarfs: They're too dim if they're far away. Of course, they exist, and Kepler is observing a sample of them, but the statistics are coming in more slowly because there are so few of them being observed. Moreover, small stellar radius cuts the probability of a transit. Yet, that moves the temperatures of interest in tighter, and I've seen an abstract for a talk suggesting that Kepler would have good info on Eta Earth for red dwarfs before other types of stars.

The typical Kepler-observed star is a G star cooler and smaller than the Sun. About halfway between the Sun and Alpha Centauri B. Gs are most typical, followed by Ks, Fs, and Ms, in that order.

All of this calls to mind a story which has made the press today, a study by Dressing, et al, which purports that Kepler has already found planets the size and temperature of Earth.

http://www.space.com/19659-alien-earth-exo...red-dwarfs.html

Note: The key detail in this work is that they have suggested a revised method of calculating stellar parameters, so that they are speaking of some particular planet candidates that earlier Kepler work has proclaimed to be somewhat larger and somewhat hotter. The method of calculating Kepler stars' parameters is acknowledged to be somewhat uncertain. The key message in the Dressing work is almost identical to that which came out a year and a half ago from Muirhead, et al, although the methods may be quite different.

http://arxiv.org/abs/1109.1819

Offering better estimates of stellar parameters for the Kepler field has been done by a few groups, and it is sure to continue for some time, so that the interpretation of Kepler candidates shifts, hopefully towards some consensus.

This subject are somewhat related to the findings of Kepler.

Are super-Earths really mini-Neptunes?

That's discouraging, but I'm wondering what sort of flaw could produce a result like that. Have you looked at individual light curves? I'm wondering if it's something that happens just once each time they roll the spacecraft, in which case these "transits" ought to be highly correlated with roll times. In fact, there ought to be a simultaneous drop for ALL stars on those panels. Is it easy to look for something like that in the data?

--Greg

It's been noted in team publications that the electronics produce spurious activity specific to certain portions of the instrument and moreover conditional on heating. Per your suggestion, the anomalies show up as an excess of false positives, not (so far as I can see) a drop-out of true positives. In the TCE list, one particular subset of anomalies shows up in 3 of the 4 seasons, but not the fourth. Plotting the locations of these TCEs makes the anomalous nature profoundly obvious, as many TCEs occur densely packed in geometric patterns, including squares, triangles, and near-line segments (or very thin rectangles).

It's particularly unfortunate that this anomaly most affects the period range of about a year (324-415d), which is the period range of greatest interest. In the TCE list for Q1-Q12, there are at least about 5 false positives for every real planet in this period range and perhaps more than 20 times as many. So unless >90-95% of them can be eliminated, it will be hard to identify the number of actual planets. I'm looking into ways to discard the false positives en masse and winnow the data down to a subset that is relatively unaffected. In that regard, it's extremely convenient that many of the false positives are clustered in certain ways. It's of little concern to have a large number of false positives if there's a way to eliminate almost all of them. At the present moment, I'm not sure if there's an effective way to do this, but there are lots of possible ways to go about it, and having observations continue into the future will probably be extremely helpful. If we get data through Q16 (which is about now), that seems like it would help a lot, because anomalies in the electronics are unlikely to show the strict long-term periodicity of actual planets.

If this problem can be addressed, we're left with the more fundamental concern that finding Earth-sized planets is challenging because host stars are noisier than the pre-mission estimates, false positives from the background are higher than we thought even a year ago, and the actual rate of occurrence may be somewhat low.

It's an exciting time... Big possibilities, but a lot of uncertainty.

Planet smaller than Mercury discovered; very impressive work for the Kepler team! (Let's not derail into definitions here, considering Mercury is the smallest in our solar system...)
http://www.jpl.nasa.gov/news/news.php?release=2013-066

Well I have some bad news.

The reaction wheel looks like its going to remain a problem. I have no idea if the spacecraft will last to 2016 or not but if anyone irk some good out of a bad situation, it's NASA.

http://www.nasa.gov/mission_pages/kepler/n...m-20130329.html

Reaction wheels are so vexing.

They need to call the guys at JAXA.

If the 3rd reaction fails (OK, when) they'll still be able to do some kind of scanning operation according to the mission manager - though it sounds like the concept is not yet fully fleshed out. The quote (from spaceflight dot com)

Hoping for the best on the reaction wheel.

Live Kepler science update today (April 18, 2013) on NASA TV. 6pm GMT, 2pm Eastern, 11am Pacific.

NASA TV ustream link

They will have the Kepler bigwigs in attendance.

Kepler Snags Super-Earth-Size Planet Squarely in a Habitable Zone

How quick this field goes. A decade ago this would not have been imagined, and yet now I find it hard to get enthusiastic about a planet that cannot be explored much further. Kepler has really changed the expectations of what planets to expect, in a good way: they're everywhere! Now, bring on TESS, JWST and ELT!

I think it's particularly important that we get good data through at least Quarters 14-16. This appears to have happened already with the download of data from Q15. Q16 is ending about now, and hopefully good data comes from much of Q16.

The importance of this is as follows (as I posted previously): Because the spacecraft performs quarterly rolls, planets with periods of about a year will always be observed when the instrument is in the same one of its four orientations. This is a problem because some of the electronics are producing false positives, a problem which is greatly mitigated if the planet is observed by different modules (i.e., when the spacecraft is at different orientations). This is a perversely insidious problem because it is most profound for smaller planets (about Mars-Earth size) with orbital periods of about a year -- precisely the most earthlike planets that Kepler could observe!

However, the problem is likely mitigated enormously when there are sufficient observations to detect four transits of such planets, because sporadic false events are very unlikely to time themselves precisely so as to occur at the same interval four times. It is much more likely that such a thing would happen three times, when only two intervals need to be nearly the same.

Four transits would occur for a world observed in quarters Q1, Q5, Q9, and Q13, and you can add +1, +2, and +3 to those sequences to derive the other possibilities. So Q13 is the first crucial quarter, and Q16 is the quarter that allows four observations of most earthlike planets that Kepler could have detected.

More observations are still better, because the signal-to-noise ratio of added observations may prove critical for observing many earthlike planets in the field. However, the observations from Q13 (through Q16) are basically de rigueur, and it seems that we have obtained at least most of that data.

Isn't this exactly what would have been imagined? Isn't this exactly why Kepler was built? To find these planets?

OK, Imagined is not the good word. I'll have to re-assess every word I post more carefully in the future. But you know what I mean... nobody knew for sure what Kepler would find.

The Kepler mission just keeps getting better and better. I watched the press conference live. It was a little speculative for my tastes but it was hard not to see how excited the team was. Also they had an hour to fill in somehow.

And I found this cool infographic too.

http://www.nytimes.com/interactive/science...=space&_r=0

Gotta love the Times.

Boy that is a great graphic! They put a lot of time into it. What tool did they use?

NASA has suddenly announced a "status teleconference" for Kepler, to take place this afternoon. Worrisome?

EDIT 1: and WOW that NYTimes graphic above IS great!

EDIT 2: Kepler may have gone into safe mode again, and NASAwatch says "it is unlikely that the spacecraft will be able to resume its original extrasolar planet detection mission." http://nasawatch.com/archives/2013/05/kepler-is-havin.html


http://www.nasa.gov/home/hqnews/2013/may/H...ler_Status.html

MEDIA ADVISORY: M13-078

NASA HOSTS KEPLER SPACECRAFT STATUS TELECONFERENCE TODAY

WASHINGTON -- NASA will host a news teleconference at 4 p.m. EDT, today, May 15, to discuss the status of the agency's Kepler Space Telescope.

Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, which is the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. Launched in 2009, Kepler has been
detecting planets and planet candidates with a wide range of sizes and orbital distances to help scientists better understand our place in the galaxy.

The briefing participants are:
-- John Grunsfeld, associate administrator, Science Mission Directorate, NASA Headquarters, Washington
-- Paul Hertz, astrophysics director, NASA Headquarters, Washington
-- William Borucki, Kepler science principal investigator, Ames Research Center, Calif.
-- Charles Sobeck, deputy project manager, Ames Research Center, Calif.

For dial-in information, journalists should e-mail their name, affiliation and telephone number to J.D. Harrington at j.d.harrington@nasa.gov. Media representatives and the public also can questions via Twitter to #AskNASA.

Audio of the teleconference will be streamed live on NASA's website at:

http://www.nasa.gov/newsaudio

Yep. Reaction wheel failure.
They're looking at seeing if they can recover one, or if not, maybe finding some way to get more science out of it.

If they can't fix it, then its game over for its primary planet hunting mission

At least it may be useful for other kinds of observations.

Actually - given that primary means something specific in spaceflight - it's important to note that it's primary planet hunting mission was 3.5 years - it exceeded that and was already in an extended mission.

Would it be useful for Kepler to randomly scan wherever it is pointed?

It does not scan, it stares to see changes, you can't stare with only 2 wheels.

According to the mission manager, it can scan if it comes to it: