Kepler mission’s extraordinary planet discoveries
Since its launch in 2009, NASA’s space telescope Kepler has identified 1,235 candidate planets beyond our solar system. Kepler has now confirmed 15 planets, discovered a rocky planet only slightly larger than Earth, and found a planetary system with six planets. Famed planet-hunter Dr. Geoff Marcy – one of the co-investigators on the Kepler mission and a pioneer in exoplanet research at the University of California, Berkeley – talked about these results on May 2, 2011 in a public talk in Flagstaff, Arizona.
I sat in on his talk, which was titled Earth-Size Planets and Intelligent Life in the Universe. I wondered, with many new planets being discovered in distant solar systems, does Marcy believe we’ll find other intelligent life in the universe?
Other exoplanet scientists – dedicated planet-sleuths who search for and study distant worlds beyond our solar system – also gathered in Flagstaff this week to discuss recent discoveries at a conference co-hosted by the NASA/JPL Exoplanet Exploration Program and titled Exploring Strange New Worlds: From Giant Planets to Super Earths. Those conference attendees had a lot to talk about, too.
Exoplanet research is in its heyday. As of May 6, 2011, 548 confirmed exoplanets are listed in the Extrasolar Planets Encyclopaedia. The Kepler space telescope should find many more through constant monitoring of the brightness of over 150,000 stars.
Marcy – who was instrumental in the discovery of the first known planet orbiting a sun-like star (51 Pegasi b in 1995) – explained how Kepler sees new planets:
We can’t see the planet, can’t see the disc of the star, but we can measure the brightness of the star. It’s so simple – take a picture and measure how many photons you got. If the star dims repeatedly over and over and over again in an almost boring way, that tells you that you have a planet orbiting that star. Earth-size planets will cause the light from the star to dim by about 1/100 of 1%.
Dr. Marcy said that Kepler is a one-meter telescope with a large 10-degree by 10-degree field of view – the size of your hand held at arm’s length. Its 95-megapixel camera simultaneously takes pictures of the same 150,000 stars every minute, adding up results every 30 minutes. Kepler is focused on an area of sky between the constellations of Cygnus and Lyra. Kepler will monitor these same stars for the entire length of its 3.5 year mission.
Kepler 10b is the first rocky planet found by Kepler – and it’s only 40 percent larger than the Earth. After finding Kepler 10b, scientists were able to figure out its mass by observing the Doppler shift of the light of the star. Marcy explained that the more massive the planet, the more it would tug gravitationally on the star. Scientists were then able to calculate its density. Kepler 10b is denser than Earth and is possibly composed of iron and nickel. Its orbit is twenty times closer to its sun than Mercury.
Speaking of Kepler 10b, Marcy said:
We have a planet that we are sure is solid. We know its mass. We know its size. We even know its orbit. We know how close it is to the star and yet we don’t have one picture of this planet. We are even guessing what the surface looks like, and frankly the interior structure – maybe there’s a mantle and a core and a magnetic dynamo, who knows – this is the stuff of theoretical calculations. It’s an amazing moment in human history.
In February, the Kepler team announced the discovery of its 1,235 candidate planets. Marcy said that 90 to 95 percent of those are probably planets. The others would be false positives. Most of those planets are nearly Earth-sized, and around 130 stars have two or more planets. One star, Kepler 11, has six planets with orbits that would fit within Venus’s orbit.
The video below shows the multiple-planet systems discovered by Kepler as of February 2, 2011; orbits go through the entire mission (three and a half years). According to D. Fabrycky, who posted this video to YouTube earlier this year:
Hot colors to cool colors (red to yellow to green to cyan to blue to gray) are big planets to smaller planets, relative to the other planets in the system.
Of the 548 exoplanets confirmed using various methods since the 1990s (as of May 6, 2011), most are the size of Jupiter. Recent findings have been different. Marcy said:
The universe contains more and more of the smaller and smaller planets. We didn’t know this two months ago. The Jupiters [planets as large as or larger than the largest planet in our solar system] happen, they occur, but they are rare. The Saturns and the Neptunes [slightly smaller than Jupiter, but still giant planets] happen and they are a little more common. But they are still rare compared to planets twice the size of Earth.
He said Kepler also found more planets orbiting farther from their star, and that red dwarf stars more commonly harbor Earth-size planets.
So, with all these planets out there, does Marcy believe the universe is teeming with intelligent life? One of Kepler’s goals is to search for Earth-like planets that might support life, but, said Marcy, the verdict is still out on whether even Earth-like planets harbor civilizations like our human one on Earth. Marcy makes the argument that single cell life is probably common in the universe. Intelligent life might be rare, however, he said. He points to the 200-million-year history of dinosaurs and the ongoing 500-million-year span of jellyfish. He also suggests that we probably already should have made contact with intelligent life, if it were out there. He said:
Once you are smart, once you have a big brain there are some detrimental aspects of being so smart, namely you can build weapons: chemical, biological, nuclear, and you have the ability to make machines that can destroy your global environment. We all know that it is our intelligence that poses one of the greatest threats to our survival as a species. We don’t know the answer to the question: what is the typical lifetime of a brainy species? Perhaps a brainy species lasts for only a few thousands of years and they flicker on and off like a Christmas tree light that flickers on and flickers off. Maybe the galaxy had some bright lights but they came and went.
He said he believes that we should be searching for life, searching for radio and television signals – searching for our kindred spirits.
Kepler will continue to post amazing discoveries as it scans its 150,000 stars for signs of distant planets. Other missions, such as the James Webb Space Telescope, scheduled for launch in 2014, will give us further information about the exoplanets already discovered.