Kepler space telescope mission extension proposal

Artist's conception of the Kepler-16 system, where the planet Kepler-16b orbits two binary stars, much like Tatooine from Star Wars. Credit: NASA/JPL-Caltech/R. Hurt

Some potentially good news for exoplanet fans, and Kepler fans in particular – Kepler scientists are asking for a mission extension and seem reasonably confident they will get it. Otherwise, funding is due to run out in November of 2012. It is crucial that Kepler receive renewed funding in order to continue its already incredibly successful search for planets orbiting other stars. Its primary goal — and the holy grail of exoplanet research — is finding worlds that are about the size of Earth, orbiting in the “habitable zone” of stars that are similar to our Sun, where temperatures could allow liquid water on their surfaces…

See Universe Today for the full article.

Six more exoplanets found by Kepler and Hubble space telescopes

The number of exoplanets being found orbiting other stars continues to grow at an exponential rate; the current number of confirmed exoplanets now stands at 692. Plus the 1,235 additional candidates from Kepler (so far!) that are awaiting confirmation. Now six more have just been added to the confirmed list, a system of three planets found by Kepler and another system of three planets discovered (or re-discovered as outlined below) by the Hubble Space Telescope.

Credit: NASA; ESA; STScI, R. Soummer

Kepler’s new planetary trio orbit the sun-like star Kepler-18, which is only 10 percent larger than our sun. One of these is a “super-Earth” about twice the diameter and 6.9 times the mass of Earth, called Kepler 18-b. It’s very close to its star, taking only 3.5 days to complete an orbit. The other two, Kepler 18-c and Kepler 18-d, are both Neptune-size worlds about 5.5 times and seven times the diameter of Earth. What’s unusual is that these two planets seem to interacting with each other in a kind of “orbital dance,” alternately tugging and pulling on each other. They take about 7.6 and 14.9 days to complete an orbit respectively, so all three planets are in orbits that are much smaller than Mercury’s in our own solar system.

Meanwhile, the Hubble Space Telescope has imaged three planets orbiting the star HR 8799 (a small but growing number of exoplanets have been directly photographed so far). The interesting part is that these planets were actually known to exist already, but they didn’t show up in the first images taken by Hubble back in 1998. But now, using more advanced techniques, astronomers have been able to tease them out of the data in those original photographs after all. There are actually four known planets orbiting HR 8799, but the fourth one hasn’t been imaged yet. (Note: the story linked to above mentions two planets photographed in the text, although the image itself shows three and this is the number quoted in other articles about this, such as DiscoveryNews).

This is an exciting time for exoplanet research, with each new discovery adding to our knowledge of the many planetary systems beyond our own; and it wasn’t that long ago when we didn’t know of any

This article was first published on

Update on potentially habitable exoplanets and the Habitable Exoplanet Catalog

There is a new report from the Planetary Habitability Laboratory (PHL), part of the University of Puerto Rico at Arecibo, regarding the number of currently known exoplanets which are potentially habitable. The findings are limited to confirmed exoplanets and exoplanet candidates, from the available Kepler data, which are within the habitable zone of their stars and with either a radius less than two Earth radii or a mass less than 10 Earth masses.

As of now, the number stands at 16, two from the confirmed list of 687 and 14 from the candidates list of 1,235. That may not sound like a lot, but if, as now thought by Kepler scientists, that the number of exoplanets in our galaxy alone is in the millions if not billions, then you can extrapolate from there…

The results will become more refined as additional candidates are confirmed in the near future, noting also that the error rate is considered to be very, very low, so by far the majority of candidates are expected to be confirmed.

The PHL is also working on a new Habitable Exoplanet Catalog (HEC), to be launched on December 5, 2011. While other catalogs provide an overview of all known exoplanets, the HEC will focus on those ones considered to be potentially habitable, which will be a very valuable resource.

Of course, it is possible that many of the exoplanets considered unlikely themselves to have life could have moons which would be potentially habitable, as we have now found in our own solar system with moons such as Europa, Enceladus and Titan. How many of those types of worlds might there be out there?

Six Earth-sized exoplanetary candidates in habitable zones?

A very interesting new article was just published (draft version) by scientists at Cornell University on September 12 regarding lower mass Kepler exoplanetary candidates. Specifically, dealing with six exoplanet candidates with sizes estimated to range from just larger than Earth (1.85 Earth radius) to a bit smaller than Earth (0.85 Earth radius), and residing within the habitable zones of their stars, with estimated equilibrium temperatures ranging from about 217 K (-56˚ C / -69˚ F) to 261 K (-12˚ C / 10˚ F). On the cool side, but within the accepted habitable zone temperature range. From the abstract of the article:

“Our results significantly reduce the sizes of the corresponding planet-candidates, with many less than 1 Earth radius. Recalculating the equilibrium temperatures of the planet-candidates from the implied stellar luminosities and masses, and assuming Earth’s albedo and re-radiation fraction, we find that six of the planet-candidates are terrestrial-sized with orbital semi-major axes that lie within the habitable zones of their low-mass host stars.”

These are still listed as candidates, but if confirmed, and the stated characteristics are confirmed (or at least close), this would be a very significant finding in the quest for Earth-like planets elsewhere.

A world of two suns

The Kepler mission has found the first confirmed known planet orbiting a binary (double) star, also known as a circumbinary planet. The planet, Kepler-16b, orbits a double star system about 200 light-years from Earth. The stars are both smaller than our own sun, one about 69 percent the mass and the other about 20 percent.

The discovery brings to mind the hot desert planet Tatooine from the Star Wars movies (hence the inclusion of John Knoll in the news briefing), which was depicted orbiting a double star system also, but long before any planets like that had been considered likely to exist, never mind confirmed. This world though, is thought to be a cold gas giant about the size of Saturn, unlike Tatooine.

Artist's conception of Kepler-16b. Credit: NASA/JPL-Caltech/R. Hurt

As others have noted, candidate circumbinary planets have been detected before, but this is the first one to be confirmed, which opens the question as to how many others there may be out there? Most of the stars in our galaxy are in binary systems, so that would further increase the number of possible planets even more, already now estimated to be in the hundreds of millions if not billions. And on that note, the current count of known exoplanets has increased again today to 684!

Kepler news briefing on September 15

Following all the news already this week from HARPS, Kepler and WASP, there will be another news briefing this week on Thursday, September 15 at 11:00 am PT (2:00 pm ET), to discuss a new finding from the Kepler mission. Whether this is related to the new total of exoplanet candidates mentioned in the previous post isn’t known, as details have been embargoed until that time. It will be broadcast live on NASA Television (and remember you can now get NASA TV apps for iPhone and iPad as well).

Interestingly, joining the scientists on the panel will be John Knoll, visual effects supervisor from Industrial Light & Magic (a division of Lucasfilm Ltd). A special effects expert, what might that be about…?


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