Kepler Data on TRAPPIST-1 Coming Online

by Paul Gilster on March 9, 2017

K2 Campaign 12 is an observational window that comes at the right time. Operating as the K2 mission, the Kepler spacecraft collected data from December 15, 2016 to March 4 of this year on the TRAPPIST-1 system. With seven planets, at least six of them likely to be rocky worlds, TRAPPIST-1 is suddenly high on everyone’s target list for future observation. The new Kepler data are a key part of this, as Geert Barentsen, K2 research scientist at NASA’s Ames Research Center at Moffett Field, California, explains:

“Scientists and enthusiasts around the world are invested in learning everything they can about these Earth-size worlds. Providing the K2 raw data as quickly as possible was a priority to give investigators an early look so they could best define their follow-up research plans. We’re thrilled that this will also allow the public to witness the process of discovery.”

The raw cadence data — ‘cadence’ refers to the time between observations of the same target — are available from the archive at MAST. Note that these are raw data files, absent any vetting or processing. Data that have been put through this process will be available some time in June. On the NASA Kepler & K2 site, Barentsen described the use of the data this way:

While we recommend that scientists only use the pipeline-processed data products in journal papers, we do encourage our community to share their understanding of the raw data with the public by blogging or tweeting tutorials and analyses. This public TRAPPIST-1 data set offers a unique opportunity to let a wider audience witness the process [of] scientific discovery.


Image: Simulated image of TRAPPIST-1’s location on the detector, from the “Create Optimal Aperture” component of the Photometric Analysis module. The 11×11-pixel aperture of K2 ID 200164267 is represented by the yellow dots. The output module for TRAPPIST-1 is 19.4, its channel is 68, and it’s located approximately at pixel row 27, column 992. Credit: MAST/STScI.

Meanwhile, the raw, uncalibrated data are intended as an aid to astronomers as they prepare proposals due this month for further investigations of TRAPPIST-1 by telescopes on Earth. Needless to say, the data gathered here, once refined and fully examined, will also factor into observations of the TRAPPIST-1 planets by the James Webb Space Telescope.

K2 Campaign 12 offers 74 days of monitoring, the longest, nearly continuous set of observations of the star yet, and as this NASA news release explains, the data give us the chance to refine earlier measurements of the TRAPPIST-1 planets, refine the orbit and mass of the seventh planet (TRAPPIST-1h), and delve into the magnetic activity of the host star.

The preparation for this observing run began in May of 2016, when the discovery of the first three planets in the system was announced. The Kepler spacecraft’s operating system was then tweaked to make needed pointing adjustments for Campaign 12. A good bit of serendipity went into the observations, for the original coordinates for Campaign 12 were set in October of 2015 before the TRAPPIST-1 planets were known. Had the exoplanet discovery not occurred when it did, Campaign 12 might have missed the system entirely.

“We were lucky that the K2 mission was able to observe TRAPPIST-1. The observing field for Campaign 12 was set when the discovery of the first planets orbiting TRAPPIST-1 was announced, and the science community had already submitted proposals for specific targets of interest in that field,” said Michael Haas, science office director for the Kepler and K2 missions at Ames. “The unexpected opportunity to further study the TRAPPIST-1 system was quickly recognized and the agility of the K2 team and science community prevailed once again.”

Another indication of the importance of the TRAPPIST-1 planets, and the likelihood that atmospheres here will be among the first investigated as we begin the search for biomarkers.


{ 19 comments… read them below or add one }

DJ Kaplan March 9, 2017 at 13:16

Are these observations going to add radial velocity data to the transit data that we already have?


Bruce Mayfield March 9, 2017 at 20:07

I’ve been a big Kepler ‘enthusiast’ since well before its launch, reading everything I can find about it over the years. I don’t recall anything about Kepler being able to collect RV data, just very sensitive brightness light curves. So I think the answer is no, but someone please correct if this isn’t correct.


Paul Gilster March 9, 2017 at 22:07

Bruce, I think DJ was asking whether the new proposals for observation via Earth instruments that are in the pipeline will include RV. The new dataset will help astronomers with additional information as they plan for the upcoming observations, and I assume some of this Earth-based work will involve RV.


DJ Kaplan March 10, 2017 at 13:11

How can we estimate mass without RV measurements?


Harry R Ray March 9, 2017 at 14:42

“K2 campaign 12 offers 74 days of monitoring…” Unfortunately, only 69 days of data were transmitted to Earth. Five days were missed due to a cosmic ray hitting the spacecraft. I am sure that this is due to the evil cryoslugs on TRAPPIST-1p firing it through a temporal gate at the spacecraft to prevent us from finding out about their Starkiller Base located on the third moon orbiting their homeworld.


Harry R Ray March 9, 2017 at 15:06



Robin Datta March 9, 2017 at 20:48

Also to be kept in mind is that “our” biomarkers, while ubiquitous to our planet, may differ from the “bio”markers of alien “bio”chemistries.


John Freeman March 9, 2017 at 22:42

I’ve heard it said repeatedly that all the TRAPPIST-1 worlds have potential for liquid water, but only three are in the habitable zone. I can imagine ice + volcanism = water for the outer worlds, but how does that work for the hot inner worlds?


Nicolas AUGUST March 10, 2017 at 11:10

With the tidal locking the inner planets may have liquid water on their dark side possibly.


Michael March 10, 2017 at 16:56

If an atmosphere existed on these planets it would likely have moved heat around the planets even with tidal locking and most likely over heated them ‘cooking off’ the water compliment like on Venus.


MGillon March 11, 2017 at 7:26

If the atmosphere is scarce enough for a (not too) hot tidally-locked rocky planet, it will not transport heat efficiently to the night side, so the night side could be cold enough for water to freeze and form an ice crust that could melt at the day-night side jonction (the terminator). This is called a “hot eyeball planet” model. See Leconte et al. 2013 ( and
So if b, c, and d are “hot eyeball planets”, they could, in theory, have some liquid water at their terminators.


Harry R Ray March 12, 2017 at 14:52

Apparently, there has been an attempt to derive radii for the inner 4 planets from unprocessed K2 data. Here they are: b, 0.95Re; c, 1.14Re; d, 0.59 Re; and e, 0.95Re. Only the “e” data falls within the error box of your data. I expect the data for “b” and “c” to also fall in your error box once the processed data comes out in May, however; the difference between your data and the unprocessed K2 data seems(correct me if I am wrong)to be too great for this to happen for “d”. Could this be because the atmosphere of d is transparent at optical wavelenghts but opaque at infrared wavelenghts? If so, waht could this mean? Also: Two other candidate “signals” appear in the K2 data. I strongly suspect that the candidate between g and h is a false positive, because it was not detected by Spitzer, but the candidate whose possible orbit lies outside of h’s may turn out to be a real planet.


Michael Fidler March 11, 2017 at 1:55
Ashley Baldwin March 13, 2017 at 18:27

Predicts the 32 day period for “h”.


Harry R Ray March 13, 2017 at 9:53

Tomorrow there will be a new paper up on ArXiv by Rodrigo Luger(et al?)based on K2 data regarding TRAPPIST-1(JUST AS I PREDICTED!). The REAL orbital period is 32.601 days(THREE TRANSITS-WE GOT LUCKY!). Sadly, this puts the planet outside of even the volcanic Hydrogen habitable zone. If this planet turns out to be a super-Europa with a substantial atmosphere, an appropriate name for it might be Aquahoth.


Ashley Baldwin March 13, 2017 at 18:07

Michael Gillon has told me that they have now constrained the orbital period of h , and that the provisional results will be on arXiv this week so that sounds about right. The extra transit data in conjunction with a current Spitzer observation (just ending) will constrain the planetary masses , via TTV, to < 20 % . With further Spitzer observations in the autumn ( and more time requested next year ) they should ulimately improve this down to the stellar noise baseline of just 10 % in the next two years .


Michael Fidler March 13, 2017 at 22:11

A terrestrial-sized exoplanet at the snow line of TRAPPIST- 1.
“The TRAPPIST-1 system is the first transiting planet system found orbiting an ultra-cool dwarf star. At least seven planets similar to Earth in radius and in mass were previously found to transit this host star2. Subsequently, TRAPPIST-1 was observed as part of the K2
mission and, with these new data, we report the measurement of an 18.764 d orbital period for the outermost planet, TRAPPIST-1h, which was unconstrained until now. This value matches our theoretical expectations based on Laplace relations3 and places TRAPPIST-1h as the seventh member of a complex chain, with three-body resonances linking every member. We find that TRAPPIST-1h has a radius of 0.715 R⊕ and an equilibrium temperature of 169 K, placing it at the snow line. We have also measured the rotational period of the star at 3.3 d and detected a number of flares consistent with an active, middle-aged, late M dwarf.”

So what is this 32.601 days? Could it be TRAPPIST-1i or TRAPPIST-1j or is it just TRAPPIST-1h incorrectly identified? Just how many planets are around this star?


Michael Fidler March 13, 2017 at 22:39

A terrestrial-sized exoplanet at the snow line of TRAPPIST- 1.
“We search for but do not detect additional planets in the system.”
So we can assume it’s just an incorrect id?
“An age in the range 3−8 Gyr (Billion years)” So may be older then the solar system!
“The presence of star spots and infrequent weak optical flares (0.38 d−1
for peak fluxes above 1% of the continuum, 30 times less frequent than active M6-M9 dwarfs) are consistent with a low-activity M8 star, also arguing in favor of a relatively old system.”
So much more conducive to life!!!


Harry R Ray March 13, 2017 at 9:55

Sorry, I meant TRAPPIST-1h.


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