Exoplanets » The Kepler Mission

At 10.50 pm Eastern Standard Time on 6 March 2009 the Kepler Mission thundered into the night sky over Cape Canaveral. It carried the hopes of the whole scientific world. It's hope was for nothing less than to find Earth sized planets in the habitable zone orbiting other stars. Its aim was similar to Corot only more ambitious. In the words of the principal investigator William Borucki of NASA's Ames Research Center in California:

"The Kepler Mission will, for the first time, enable humans to search our galaxy for planets as small as or even smaller than the Earth. With this cutting-edge capability, Kepler may help us answer one of the most enduring questions humans have asked throughout history: Are there others worlds similar to the Earth in the Universe?"

Like Corot, Kepler will detect planets indirectly, using the "transit" method. The periodic signature is used to detect the planet and to determine its size and its orbit. Seth Shostak, a senior astronomer at the SETI Institute explained it very dramatically:

"Take a bare 100 watt light bulb and switch it on. Step back about 300 miles. Once you're in position, arrange for a friend to slowly pass a pinhead 30 feet in front of the bulb without notice or warning. Your job is to detect the decrease in light when the pinhead gets between you and the bulb. I suspect that's not something you do every day. But NASA's Kepler telescope will be doing it every half-hour for the next three years and more. In fact Kepler will be measuring the brightness of more than 145,000 light bulbs (stars). Kepler will continuously monitor the luminosity of 145,000 stars in the region of constellations Cygnus and Lyra, looking for dimming of as little as 0.006 percent of a star's brightness. Unlike other schemes for finding planets around distant stars (so-called "exoplanets"), Kepler may discover Earths. That is, it can detect worlds hundreds of light years away that are comparable in both size and orbital position to our home planet. Cousins of the Earth – and obvious candidates for life."

An artist's impression of the Kepler's hunt and its target stars shown on the right above is due to Jon Lomberg, NASA.

A little over a year after take off, on June 15 2010 the Kepler team released a massive list of 300 extrasolar planets already found.

At least a dozen of the candidates are of comparable size to COROT 7 b at just 1.6 times the diameter of Earth, and some are estimated to be slightly smaller.

And those are just the smallest contestants from the set the Kepler team has not retained for follow-up observation. They have withheld data until February 2011 describing 400 possible stellar systems containing objects that appear as small or perhaps even smaller than the Earth. These Kepler discoveries also reveal that quite a number of Gas Giants in the habitable zone exists, some of which may have Earth sized moons. Natalie Batalha, a professor of physics and astronomy at San Jose State University and a co-investigator on the Kepler team states quite confidently:

"Kepler has seen Earth-size planet candidates. But before COROT 7 b loses its crown as the smallest known exoplanet, Kepler's candidates must be verified with more data to rule out possible errors".

The Kepler space telescope continued its mission successfully until May 2013 when one of the three reaction wheels that enables the instrument to aim very accurately on its target malfunctioned. For several months it was thought that nothing could be done to continue searching for transits. However the ingenuity of the scientists and engineers found ways to continue to use the instrument. Kepler's loss of a second spacecraft reaction wheel in May 2013 effectively ended data collection in the original Kepler field after 4 years of continuous monitoring. However, all other Kepler assets remain intact and can be used to continue the mission. In June 2014, K2 became fully operational, obtaining a photometric precision approaching closely that of the Kepler hardware it inherited.

On 7 January 2015 NASA announced that Kepler had confirmed the discovery of 1000 new planets with many more probables. Whilst many of them were large gas planets there were quite a few only slightly larger than Earth which have been named as Super-Earths. To date some planets have now been located that are a slightly smaller and of lower mass than the Earth. A number of stars have been found that have several planets. One of the most promising discoveries is that of the Kepler 186 system. The star is about 490 light years from Earth. The star is a red dwarf and less massive than our Sun. Five planets are known to orbit the star. The most distant of the five is Kepler 186f. This planet may lie in the habitable (Goldilocks) zone . Although much nearer to the star than the Earth is to the Sun, it may be distant enough not to be tidally locked. It may however probably rotate much more slowly than Earth and its day could be weeks or months long.

The ultimate prize of Kepler's hunt, an Earth type planet in the habitable zone orbiting around a sunlike star, remains years away. The Kepler team's protocols require that three transits must be recorded, along with other observations, before a candidate can be confirmed as a true planet, and an Earth-like orbit will carry a planet into Kepler's view just once a year - when the three objects—the planet, the host star and Kepler—fall into alignment. The Kepler transit graph diagram shown on the right above is courtesy of NASA, as is the illustration of the Kepler mission satellite shown on the left below.

There can be almost no doubt that we are on the brink of discovering planets like the Earth. The next missions which are even now being planned are the Terrestrial Planet Finder by NASA and the Darwin Mission by the European Space Agency (ESA).
In view of the financial situation it is likely that the missions may be amalgamated and that they may take a more international character.

NASA Ames Research Center presents a plaque to Nichelle Nichols (Lieutenant and Commander Uhura of Star Trek) 24 February 2010. Left to right:
Peter Tenenbaum (Kepler Science Operations Center Engineer),
Roger Hunter (Kepler Mission Manager),
Nichelle Nichols (Lt and Commander Uhura of Star Trek),
Lew Braxton, Jon Jenkins (Kepler Co-Investigator),
Dave Koch (Kepler Deputy Principal Investigtor), and
Pat Carroll.

Members of the Kepler Mission, NASA Ames Research Centre:

William Borucki
Principal Investigator
Kepler Mission
NASA Ames Research Centre

David Koch
Deputy Principal Investigator
Kepler Mission
NASA Ames Research Centre

Natalie Batalha
Kepler Mission
NASA Ames Research Centre

Edna DeVore
Kepler Mission
The SETI Institute

Ray Goodwin

Somewhere there are mountains
Glistening in the snow
Somewhere there are mountains
That we shall never know

Somewhere there are rivers
Flowing fast and free
Somewhere there are rivers
That we can never see

Somewhere there are oceans
And sun drenched island sands
Forests full of creatures
In vastly distant lands

Somewhere there’s a planet
Beneath an alien star
The people watch our tiny sun
And wonder where we are

One day perhaps we’ll find them
Across the void of space
Perhaps through ways as yet unknown
We’ll meet them face to face

The author of this web site Ray Goodwin holds B.Sc. Degrees from London University in Chemistry, Geology and Physiology and an M.Sc. in Biochemistry. He has spent most of his professional life teaching in Colleges of Technology. On his retirement he has entered the fields of astronomy, astrochemistry, astrobiology and space sciences. He has spent a great deal of his retirement in visiting amateur astronomy societies and in attending European Space Agency Symposia in ESTEC in the Netherlands and other scientific conferences in England and Sweden. He regularly attends the yearly European Astrofest in South Kensington London and other meetings in the UK. He has written scientific articles and given a number of lectures on diverse scientific subjects.

Readers of this web site are invited to e-mail the author ( ray@lifeinthecosmos.com) and discuss their opinions of the topics dealt with and suggest any changes which they think may be helpful.

Life in the Cosmos Website
Version 01.00 - April 20, 2015.