Kepler Mission Options

[Explorer1]

Meanwhile, from the primary mission, another unexpected discovery.
Shades of Clement's 'Mission of Gravity', but truth is yet again stranger than fiction...

[Gerald]

Since people always want to know, and I didn't find the numbers anywhere else, I calculated the surface gravity to be 3.0 +/- 0.4 -times the surface gravity of Earth (using 2.35 Earth radii, and density 7.1 +/- 1.0 g/cm³).

Edit: More technical details.

[AndyG]

Surface gravity is linearly proportional to density and radius - I think your result is too high.

Edit - Apologies! No it isn't. My error!

Andy

[brellis]

space dot com article on binary exo-earths - http://www.space.com/27832-binary-earth-si...en-planets.html

A pair of smaller planets would possibly give a signal that looks like one bigger planet in the Kepler survey, perhaps?

[Phil Stooke]

Yes, I guess, in that they would block more light from the star than either one individually. Presumably as they orbited each other, each eclipse ingress would look different (stepwise eclipse versus simultaneous), and if they occulted each other the depth of the eclipse would sometimes vary during the eclipse or between eclipses... I think the details of the binary could be worked out in ideal circumstances.

Phil

[Jackbauer]

http://spaceref.com/exoplanets/reborn-kepl...ew-mission.html

NASA's planet-hunting Kepler spacecraft makes a comeback with the discovery of the first exoplanet found using its new mission -- K2.
(…)
The newly confirmed planet, HIP 116454b, is 2.5 times the diameter of Earth and follows a close, nine-day orbit around a star that is smaller and cooler than our sun, making the planet too hot for life as we know it. HIP 116454b and its star are 180 light-years from Earth, toward the constellation Pisces.

[JRehling]

I'm delighted and surprised that Kepler has been brought back online!

In every way but one, the new discovery is just one more planet on a huge list. But there's one remarkable thing: Its distance from Earth. 180 light years is very close for a Kepler discovery. Most Kepler discoveries are in the range of 1000-6000 light years, because of its "deep stare" strategy. The ones that are just a couple of hundred light years away or less are much more accessible for follow-up study.

[Jackbauer]

http://www.nasa.gov/press/2015/january/nas...mall-worlds-in/

NASA’s Kepler Marks 1,000th Exoplanet Discovery, Uncovers More Small Worlds in Habitable Zones

Two of the newly validated planets, Kepler-438b and Kepler-442b, are less than 1.5 times the diameter of Earth. Kepler-438b, 475 light-years away, is 12 percent bigger than Earth and orbits its star once every 35.2 days. Kepler-442b, 1,100 light-years away, is 33 percent bigger than Earth and orbits its star once every 112 days.
Both Kepler-438b and Kepler-442b orbit stars smaller and cooler than our sun, making the habitable zone closer to their parent star, in the direction of the constellation Lyra. The research paper reporting this finding has been accepted for publication in The Astrophysical Journal.

With the detection of 554 more planet candidates from Kepler observations conducted May 2009 to April 2013, the Kepler team has raised the candidate count to 4,175. Eight of these new candidates are between one to two times the size of Earth, and orbit in their sun's habitable zone. Of these eight, six orbit stars that are similar to our sun in size and temperature. All candidates require follow-up observations and analysis to verify they are actual planets

[brellis]

Our galaxy may host billions of planets where liquid water can exist - http://www.spacedaily.com/reports/Milky_Wa..._study_999.html

...researchers from the Australian National University and the Niels Bohr Institute in Copenhagen attempted to calculate how many stars in the Milky Way could have planets in their habitable zones where liquid water could exist.
...

"The calculations show that billions of the stars in the Milky Way will have one to three planets in the habitable zone...," said a statement from the Niels Bohr Institute.

The findings of the study were published in the scientific journal Monthly Notices of the Royal Astronomical Society.

The team used a new version of a 250-year-old method called the Titius-Bode law, which correctly predicted the position of Uranus before it was discovered.

According to the law, there is a ratio between the orbital periods of planets in a solar system.

Therefore, if you know how long it takes some planets to circle the star, you can calculate the orbital period of others, determine their position and find planets "missing" from the sequence.

"We decided to use this method to calculate the potential planetary positions in 151 planetary systems, where the Kepler satellite had found between three and six planets," said researcher Steffen Jacobsen of the Niels Bohr Institute.

->edited to remove content heading into Rule 1.3 territory

[Explorer1]

Telecon tomorrow morning:

http://www.jpl.nasa.gov/news/news.php?feature=4660

Interesting list of speakers...

[JRehling]

There's speculation that today's announcement might indicate something like "the most earthlike" planets found so far. Determining the properties of Kepler discoveries always leaves significant uncertainty regarding size and temperature, so any announcement could only go so far and be probabilistic in its conclusions regarding any single planet. So I might guess that they've found a few candidates, leaving a high probability that one of them really is in some interesting range of size-temperature even if we don't know which of the candidates that is.

Another possibility is that a new type of analysis of existing data has been utilized. The existing pipeline was finding a couple of (possibly, loosely speaking) "earthlike" planets and might find a couple more. Jeff Coughlin's research might be doing something new. He's looked at:

Secondary eclipses to try to find the properties of larger planets (which might work on some rare smaller ones?).
Absorption during primary eclipses to try to find the properties of planets' atmospheres.
And, searching for smaller planets in general.

It seems like one of these methods has turned up something new. We'll find out soon.

[Explorer1]

Starting in a few minutes: almost 50,000 viewing now....
Graphics here: http://www.nasa.gov/keplerbriefing0723

[JRehling]

The real significance here is not the particular discovery itself – a Super Earth in the habitable zone of a sunlike star – but the fact that we're getting a data point that extends the already very-very-near-certain likelihood that planets of earthlike size exist in these situations.

The previous discovery, of Kepler 186-f, indicated that "earthlike" planets exist around smaller, cooler stars. The only way in which this new discovery is "more earthlike" is in the nature of its star.

[dvandorn]

Well -- the other big thing about this new discovery is that it's a planet orbiting in the habitable zone of a sunlike star, and thus, unlike those orbiting smaller stars, is far enough away from its star to avoid tidal lock. I has a 385-day year.

Even if it's five Earth masses, it's roughly 6 billion years old, and has spent almost all of that time in the habitable zone of its star. And hasn't been tidally locked to its primary. I have to think that life is more possible in such a situation than on a smaller planet orbiting a cooler star in less than 100 days that always shows the same face to its star.

-the other Doug

[JRehling]

Generally speaking, most Kepler discoveries are going to be difficult targets for follow-up study, and I would anticipate that in almost every case of a small planet discovery, we'll be able to perform follow-up science on closer planets that are yet to be discovered before we can do it with the particular Kepler discoveries. So my mantra is that the real significance of Kepler work will be to provide a partial statistical survey of planet type frequencies. Systems within 50-250 light years will be where the details will eventually come from.

But, definitely, the main excitement around "sunlike stars" is that they are unlikely to put "earthlike planets" into tidal lock, whereas dwarf stars may do that quite often. On the other hand, dwarf stars outnumber sunlike stars, so there may be more un-locked earthlike planets around the former than the latter.