Surprise: Earth-sized Planets Are Common

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Kamuela, Hawaii – A team of astronomers from the University of California, Berkeley and the University of Hawaii at Manoa has found that 17 percent of all sun-like stars have planets one to two times the diameter of Earth in close orbits. The finding, based on an analysis of the first three years of data from NASA’s Kepler mission and the W. W. Keck Observatory on the summit of Mauna Kea, Hawaii, was announced at the American Astronomical Society meeting in Long Beach, California this week.


While other studies had shown that planets around stars are common in our galaxy, until this study, it remained unclear if this is true for Earth-size planets. 

The team consists of UC Berkeley graduate student Erik Petigura, former UC Berkeley postdoctoral fellow Andrew Howard, now on the faculty of the UH Manoa Institute for Astronomy, and UC Berkeley professor Geoff Marcy.

To find planets, the Kepler space telescope repeatedly images 150,000 stars in a small region of the sky. It looks for a tiny dip in each star’s brightness that indicates a planet is passing in front of it, much like Venus passed between Earth and the sun last summer.

We took a census of the planets detected by the Kepler Space Telescope,” said Howard. “Erik Petigura wrote a new pipeline to detect the shallow dimmings of Earth-size planets in Kepler photometry. With his efficient and well-calibrated pipeline we could confidently report the size distribution of close-in planets down to Earth-size. The result is that Earth-size planets are just a common as planets twice Earth size. Remarkable.”  

The Keck Observatory played a crucial role in this project, he said. While these planets were detected by the space-borne Kepler Telescope, the mighty Keck I Telescope fitted with HIRES (High Resolution Echelle Spectrograph) and a newly upgraded guider system were used to characterize the host stars of the newly discovered planets and to rule out any false planet detections from Kepler. “We took HIRES spectra of most of the planet host stars to characterize the Kepler-discovered systems and to search for double lines (which would indicate a possible false planet detection),” he said.The Observatory’s HIRES was improved in 2012 with Keck’s custom Multi-object Acquisition, Guiding and Image Quality, or MAGIQ, system to dramatically improve the instrument’s performance. MAGIQ was made possible by contributions from the Observatory’s growing base of private supporters.

Broadly speaking, new the MAGIQ guide camera is helpful for several reasons: “The wider field of view, finer pixel scale, and improved noise characteristics make the experience of observing more efficient – and enjoyable,” Howard said. “Those characteristics also yield better guiding on faint stars, which improves our efficiency and crucially improves the stability of the HIRES spectra.”

The team’s estimate includes only planets that circle their stars within a distance of about one-quarter Earth’s orbital radius – well within the orbit of Mercury – which is the current limit of Kepler’s detection capability. Further evidence suggests that the fraction of stars having planets the size of Earth or slightly bigger orbiting within Earth-like orbits may be as high as 50 percent.

Written By: W.M. Keck Observatory
continue to source article at keckobservatory.org

12 COMMENTS

  1. In reply to #1 by Alternative Carpark:

    Well, excuse me while I go and pack my suitcase.

    Mars One will be taking
    applications for “mars human settlement mission”.

    Let’s see – chocolate, hairdryer, George Strait cds…

    Seriously, it is encouraging and exciting to see the private sector becoming more and more
    involved, including private funding for this Kepler/Keck study.

  2. The discussion so far is far too highbrow for me. I’m just a little bit pleased that Earth sized planets are not as uncommon as was thought till recently.

    As Feynman said, along the lines of : “if the theory disagrees with experiment, the theory is wrong”. I can’t fault his approach.

  3. In reply to #2 by bluebird:

    In reply to #1 by Alternative Carpark:

    Well, excuse me while I go and pack my suitcase.

    Mars One will be taking
    applications for “mars human settlement mission”.

    Let’s see – chocolate, hairdryer, George Strait cds…

    .. …… thermocouple nuclear isotope generator, excavator, enclosed rover vehicle(s), double-shell-spacesuit, inflatable habitation modules – youtube.com/watch

  4. In reply to #8 by Alan4discussion:

    In reply to #2 by bluebird:

    In reply to #1 by Alternative Carpark:
    .

    .. …… thermocouple nuclear isotope generator, excavator, enclosed rover vehicle(s), double-shell-spacesuit, inflatable habitation modules – youtube.com/watch

    Well, yeah, those too ;)

    Interesting video; re the animal robots – isn’t the U.S. military working on something similiar?

    The selection process for these mission scenarios reminds me of ‘Contact’ – who should go??

  5. In reply to #6 by bluebird:

    BBC’s far-out Drake Equation chart.

    The link brings up this message when accessed from the UK:-

    BBC Future (international version)

    We’re sorry but this site is not accessible from the UK as it is part of our international service and is not funded by the licence fee. It is run commercially by BBC Worldwide, a wholly-owned subsidiary of the BBC, the profits made from it go back to BBC programme-makers to help fund great new BBC programmes. You can find out more about BBC Worldwide and its digital activities at http://www.bbcworldwide.com.

  6. rationalwiki.org/wiki/Drake

    The Drake Equation is a method for calculating (or more accurately, guessing) the probability of intelligent extraterrestrial life. The equation is often put as follows:
    N=R^{ast} times f_p times n_e times f_l times f_i times f_c times L

    where

     N represents the number of civilizations with which we might be able to communicate;
     R* is the average rate of star formation in our galaxy
     fp is the fraction of those stars that have planets
     ne is the average number of planets that can potentially support life per star that has planets
     fℓ is the fraction of the above that actually go on to develop life at some point
     fi is the fraction of the above that actually go on to develop intelligent life
     fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
     L is the length of time such civilizations release detectable signals into space. 
    

    We are starting to get some figures for some of these inputs, but many are still simply wild guesses.

    ( The formula looks clearer on the link.)

    “Earth-size-planets”, or “Earth-mass planets”, should not be confused with “Earth-type planets”.

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