Kepler Scientists Find Plethora of Candidate Planets, Some in Habitable Zones

Data from NASA’s Kepler space telescope show that there are more than 1,200 planet “candidates” in a section of our galaxy framed by the constellation Cygnus and some are in the “habitable zones” of their stars.

Kepler scientists announced the results at a press conference this afternoon, explaining that it takes considerable analysis before a candidate planet is confirmed as an actual planet. To do that, additional observations and analysis are needed, but Debra Fischer, a Yale astronomer participating in the press conference, estimated that only about 20 percent will turn out to be false positives.

Explaining that Kepler is in search of the “holy grail” – an Earth-size planet in the habitable zone of a star that is like our Sun, Doug Hudgins, Kepler program scientist at NASA Headquarters, cautioned that he did not expect that result to come so early in Kepler’s observations. The space telescope has been operating for about one and a half years. A planet the size of Earth around a star like our Sun that has temperature conditions suitable for life as we know it would mean that it, too, would orbit once a year. Thus, it would take two years for scientists to notice it crossing (transiting) the face of the star, and a third year for them to really take notice of it. More time therefore is needed.

In the meantime, however, Kepler is finding hundreds of candidates to be confirmed as planets around other stars, called exoplanets. The telescope is looking at 155,000 stars in the constellation Cygnus. To date, 1,235 exoplanet candidates have been discovered, of which 68 are Earth-sized, 288 are “super-Earths,” 662 are the size of Neptune, 165 are the size of Jupiter, and 19 are even larger than that. Of the 1,235 candidate exoplanets, scientists identified 54 that are not too close and not too far from their star to be in the habitable zone where liquid water might exist. Five of the 54 are close to the size of Earth; the rest are larger.

The scientists were particularly excited at the number of stars with multiple planets forming solar systems not unlike our own. One of these, designated Kepler-11, has six planets. Those planets have been confirmed. Five of them are clustered together as close to the star as Mercury is to our Sun. The sixth planet is within the distance of Venus from our Sun. Most of the planets and planet candidates identified so far are close to their stars because they are the easiest to observe since they transit the star often and thus can be discerned. The Kepler-11 solar system is 2,000 light years from Earth, meaning that the light from the star took 2,000 years to get here.

Jack Lissauer, Kepler co-investigator and planetary scientist at NASA’s Ames Research Center, said they were very surprised to find so many planets so close to their star and so large. All six in the Kepler-11 system are larger than Earth. He said that the finding would “force us to go back and look at the formation models of planets.” The planets are low density, “fluffy like marshmallows, but not all gas, maybe marshmallow with a little hard candy at the core,” he said.

William Borucki, Kepler Science Principal Investigator at NASA/Ames, emphasized that Kepler is able to look at only about one-four hundredth of the total sky. “Imagine if we could see all of it,” he exclaimed. As for when we would know if there is life on any of these planets, Borucki indicated it will be many years. Comparing the process to building a cathedral, he said this step is just laying the foundation and it will take “patience and lots of money” to answer that question. Discovering if any of them have atmospheres is a critical step yet to come, he said.

Even without that, however, Yale’s Fischer asserted that Kepler “has blown the lid off of everything we thought we knew about exoplanets.”