Astroblog

The Star Kepler16 B about to eclipse Kepler16 A as seen from Kepler 16 (A/B) b. Image simulated in Celestia.

Well, it's now clear why representatives of Industrial Light and Magic (Lucas Films) were at the NASA press conference this morning. The Kepler team announced the finding of Kepler-16b, a world that circles two suns, like Tatooine from Star Wars.

Admittedly, Tatooine orbited two stars that were very like our sun, while Kepler 16-b sun's are mismatched dwarf red stars. Also, Kepler 16-b is about 2/3rds the size of Jupiter, like Saturn, and just outside it's habitable zone; more like Hoth or Bespin than the parched, rocky desert world of Tatooine.

Kepler 16 (AB) system face on.

It's also not the first world in a multiple star system, although a white dwarf/pulsar system isn''t very Tatooine like. We've even found a planet in a triple star system as far back as 2005, but it is the first world that circles both stars, and both of which are at least notionally Sun-like. What does it mean overall? We originally thought that it would be difficult for planets to form around close binaries, that the dynamics of binary star formation would disrupt any protoplanets. Kepler 16 b shows that recognisable worlds can also form under these conditions, which greatly expands the number of stars which can have planets.

What does this mean for finding life? In this case Kepler 16 b is just outside the habitable zone, but a moon with a thick atmosphere might be warm enough for life. Another issue is whether the varying distances of the component suns would make planetary temperature swings too large for any form of complex life.

For Earth, the major driver of seasonal variation is the angle of inclination to the Sun, rather than the distance (northern hemisphere summer occurs at aphelion, when the earth is at it's furthest from the Sun, but Kepler 16 B comes closer and further from this world than Earth does to our Sun, and 20 day seasons could be interesting.

NASA's Kepler website has some good illustrations and animations, as well as some "Artists Concepts" with the press release. You can find more thoughts on this report at Universe Today, the Bad Astronomer, Greg Laden's blog and Dynamics of Cats. The original paper can be found here.

Of course, I've made a Celestia file. Two actually, one for the binary star system and one for the planet. I've had to guess the distance of the main star from the solar system barycenter, based on the illustration in et al., 2011, but the rest comes from the discovery paper except for the rotation period of the B component.

As usual, copy the data here to plain text files (Kepler16_binary.sts and Kepler16b.ssc), the copy both the files to the Celestia extras folder. The stars are 195 lightyears away, so in the Celestia star browser, you will have to show around 250 stars to see Kepler16 in the list. I'll have to update my Celestia Exoplanet Tour as well.

======================== Kepler16_binary.sts =========================
Replace Barycenter "Kepler16:2MASS 19161817+5145267:KIC 12644769" # replace the old star definition
{
RA 289.0750 # in degrees 19 16 18
Dec 51.7575 # in degrees +51 45 27
Distance 195.6981756 # in light years 60 pc
}

"Kepler16 A:2MASS 19161817+5145267 A:KIC 12644769 A" # Mass = 0.69 Sun masses
{
OrbitBarycenter "Kepler16"
SpectralType "K8V"
AppMag 12
Radius 451634 # in km, 0.6 Sun radii
EllipticalOrbit {
Period 0.1125 # P or T, in years
SemiMajorAxis 0.00496 # a, in AU (mass ratio MA/MB = 0.96/0.13)
Eccentricity 0.15944 #
Inclination 90.304 # in degrees
AscendingNode 0.0 # in degrees
ArgOfPericenter 263.464 # in degrees
MeanAnomaly 0.0 # in degrees
}
UniformRotation {
Period 842.4 # in hours, 35.1 days
}
}

"Kepler16 B:2MASS 19161817+5145267 B:KIC 12644769 B" # Mass = 0.33 Sun masses
{
OrbitBarycenter "Kepler16"
SpectralType "M4V"
AppMag 13
Radius 157456.08 # in km, 0.23 Sun radii
EllipticalOrbit {
Period 0.1125 # P or T, in years
SemiMajorAxis 0.22431 # a, in AU (mass ratio MA/MB = 0.96/0.13)
Eccentricity 0.15944 # guess, to be determined
Inclination 90.304 # in degrees
AscendingNode 0.0 # in degrees
ArgOfPericenter 0.0 # in degrees
MeanAnomaly 0.0 # in degrees
}
}
========================end======================================

=========================>8 Kepler16b.ssc >8==========================
"b" "Kepler16 A"

# Saturn-like world that orbits a binary star system, a bit Like Tatooine

{

Texture "exo-class4.*"
NightTexture "exo-class4night.*"
# Using Gas Giant


Mass 105.86 # M.sin(i) = 0.333 Jupiter
Radius 53890.6696 # 0.7 Jupiter radi, from paper

InfoURL "http://exoplanet.eu/planet.php?p1=Kepler-16+%28AB%29&p2=b"

EllipticalOrbit {
Period 0.626344263
SemiMajorAxis 0.7048
Eccentricity 0.0069
ArgOfPericenter 318
Inclination 90.0322
AscendingNode 0.003
MeanLongitude 106.51
#MeanAnomaly 271
}

# likely to be in captured synchronous rotation
}

AltSurface "limit of knowledge" "Kepler16 A/b"
{
Texture "extrasolar-lok.*"
}
===========================>8 cut >8============================

Labels: exoplanet, extrasolar planet, Kepler Space Telescope, spacecraft

I've posted links to the data from the Kepler Extrasolar planet mission (now linked to in Wikipedia, I'm not worthy), data on over 1,200 extrasolar planets and their stars. My Excel graph was rather sucky, but Flowing Data has some stunning visualizations of the data, and a cool animation from Jer Thorp. Rush over there right away.

(tip of the spreadsheet to Cosmic Variance)

Labels: exoplanet, extrasolar planet, Kepler Space Telescope

KOI-701.03, an as yet unconfirmed, Earth-like world probably in the habitable zone of its Sun. KOI-703.03 visualized in Celestia (click to embiggen).

As well as the unusual Kepler-11 solar system, the Kepler spacecraft has so far reported 1235 planetary candidates around 997 stars. See the paper here for more detail (warning, huge PDF file over 100 pages long)

To put this in perspective, in four months of staring a a patch of sky in Cygnus the size of your outstretched hand, Kepler has come up with 3 times as many extra-solar planets (maybe), as we had discovered from 1995 to June 2010.

Trying to understand this firehose of information will be a bit of an effort. First off, all these transit candidates have to be independently confirmed. This will be a massive piece of work, especially and ground based telescopes can only monitor the region of space Kepler scanned for about 6 months of the year, and multiple transits will have to be observed.

Distribution of planetary systems picked up by Kepler, I've used slightly different cutoffs that the Kepler folks (eg, I've used a 0.8-1.25 Earth radii as the criteria for 'Earth-like" but Kepler goes down to smaller radii). Click to embiggen.

Secondly, there is so much data. Trying to wrap our heads around the data will be bewildering, even for folks who are used to large data sets.

As a service to the amateur community, I've made Excel Spread sheets of tables 1 and 2 of Borucki et al, "Characteristics of planetary candidates observed by Kepler, II: Analysis
of the first four months of data", the Star Characteristics (table 1) and the Planet Candidates (Table 2) so you can play with the exoplanet data. Also, Kevin Schlaufman has made a plain text formatted electronic table that joins up Tables 1 and 2 (hat tip to Systemic) which is good for correlating planetary characteristics with stellar characteristics.

If you use this please a) remember to cite Borucki et al., (they did all the hard work after all) and b) remember that most candidates are unconfirmed, so don't get too excited. Most candidates will be real, but perhaps 5% are false positives, so be careful.

As an example of what can be done I've made a Celestia file of the unconfirmed Super-Earth KOI 701.03, which may be in the systems habitable zone (it is currently the most Earth-like world in a habitable zone). First download newextrasolar.stc here, (I've updated it with KOI 701 if you have downloaded a previous version) then copy it into the Celestia extras folder. Then you need the file the sets out the exoplanet Kepler701b.ssc, download it here and copy it into the extras folder.

Now, at -11 ºC the calculated black-body temperature of the planet is hotter than the black-body temperature of Venus (how hot Venus would be if it didn't have it's crushing carbon dioxide atmosphere, for comparison, without earth atmosphere our black body temperature would be -18 ºC) . How hot it is really depends on the nature of its atmosphere.

If I get enough time I'll make a script which will auto-magically extract data from the spreadsheets into Celestia format.

Other implications of the Kepler data are that if it's results are representative of the galaxy in general, then around 50% of Sun-like stars have planets, and they may be at least one million Earth-like planets in habitable zones in the Milky-Way alone.

While Kepler has only found planets around 0.6% of the stars it's looked at, it has been looking for only 4 months, and for example, it would be very unlikely to pick up a transit of a planet with an Earth-like orbital period or longer. As well, most stars will not be correctly oriented for Kepler to see a transit, which is why a 0.6% find rate implies that there are LOTS of planetary systems out there.

The Journal Nature has some free articles on the hunt for exoplanets here and here, the Bad Astronomers take is here, and Life at the SETI Institute here. Systemic has thoughtful posts here and here and a great video here, Centauri Dreams muses here.

Join the Planet Hunters and search the Kepler data for planetary candidates yourself!

Labels: exoplanet, extrasolar planet, Kepler Space Telescope