Goldilocks

It was an early Christmas present for astronomers in 2011 when NASA reported the finding of Kepler 22b, a promising “Goldilocks” planet.

We all know the child’s story of Goldilocks and the Three Bears.  Goldilocks finds the home of the three bears, enters their dwelling and tastes their porridge, finding it too hot or too cold.  So it is with a Goldilocks planet which is found in the habitable zone around the parent sun.  Too close to the sun, it is too hot and water will boil away; too distant from the sun, it is too cold and water will freeze.  The habitable zone is the area found between the two orbital extremes where water will remain a liquid.  Kepler 22b is such a planet; however, much additional work must be completed to confirm current observations.    

We will never know the extent of ancient man’s interest in the heavens, but it is doubtful that it was more than some level of casual wonderment or possibly religious.   Early cultures of civilized man de- veloped surprising abilities in astronomy  providing modern man with much information from their observations, but without touching on the possibility of other worlds, habitable or not.  The world had to wait until the late 20^th century before interest and ability had advanced sufficiently to permit realistic studies in other worlds.

Mid-20^th century found interest growing in the possible existence of other intelligent life with a few organizations devoting their time to the search for patterns of electronic emissions.  This effort was relatively minor.  During 1959-60 a relatively large program called SETI was initiated to conduct a major search.  In 1960s – 1970s, NASA joined the program with low-level contributions, including Project Orion, the Microwave Observing Project and others.  In 1992, NASA initiated a formal, more intensive, SETI program.  Less than a year later, while NASA was still organizing the updated SETI, Congress cancelled the program.  In 1995, while Congress was withdrawing the United States from the search program, two researchers of the Geneva Observatory detected the first exoplanet, 51 Pegasi b, a “hot Jupiter” gas giant planet orbiting the star 51 Pegasi, 50 light years from Earth.  Major participants in the cancelled NASA program, strongly disagreed with the action of Congress and reorganized SETI under two private non-profit organizations, SETI Institute and SETI League.  In 1980, Carl Sagan, Bruce Murray and Louis Friedman founded The Planetary Society and inspired the public to support the search for intel-ligent life.  Since its origination, the society has been the major program in non-government, non-profit searches for intelligent life, extrasolar planets and a multitude of other activities in astronomy sup-ported exclusively by the membership.  One of the major contributions by the society is a catalog of all known exoplanets with detailed information on each.   In the meantime, NASA has had a continued interest in astrobiology and has included the search for intelligent life in its Origins program.

Not to be undone by The Planetary Society, the Planetary Habitability Laboratory at the University of Puerto Rico, Arecibo has developed a second catalog of planets, but this time the catalog covers habitable planets.  The Habitable Exoplanets Catalog provides readers, through the Internet, with a schedule of potential habitable exoplanet discoveries.  The current issue describes over 15 exoplanets and 30 exomoons as potential habitable candidates.  It should be noted that while a planet or moon may be in the habitable zone of a star, until the status of the planet or moon is clearly defined, it is only a candidate for habitability.  For example, if researchers on some distant planet were to observe our Solar system, they would find three planets orbiting in the habitable zone.  It would take additional research to determine that one planet was too hot to be habitable (Venus), one was too cold to be habitable (Mars), but the third was habitable (Earth).  Finding planets in the habitable zone of a star must be considered as an early first step subject to further review.

Enter the Kepler mission.  With the end of the 20^th century, NASA and others had confirmed substantial numbers of exoplanets, including gas giants, hot-super-Earths in short period orbits, and ice giants.  The new challenge was to find terrestrial planets having from half to twice the size of Earth preferably in the habitable zone of their stars.  The Kepler Mission was the considered means of satisfying the new search.

From a concept study in 2000 the Kepler Mission was assigned NASA Discovery Mission #10 and   “. . . designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets.”

“The scientific objective of the Kepler Mission is to explore the structure and diversity of planetary systems.  This is achieved by surveying a large sample of stars to:

1.       Determine the abundance of terrestrial and larger planets in or near the habitable zone of a wide variety of stars.

2.       Determine the distribution of sizes and shapes of the orbits of these planets.

3.       Estimate how many planets there are in multiple star systems.

4.       Determine the variety of orbit sizes and planet reflectivities, sizes, masses and densities of short-period giant planets.

5.       Identify additional members of each discovered planetary system using other techniques, and

6.       Determine the properties of those stars that harbor planetary systems.

“The Kepler Mission also supports the objectives of future NASA Origins theme missions Space Interferometry Mission (SIM) and Terrestrial Planet Finder (TPF), by:

·         Identifying the common stellar characteristics of host stars for future planet searches.

·         Defining the volume of space needed for the search, and

·         Allowing SIM to target systems already known to have terrestrial planets.”

NASA Discovery Mission #10 was assigned in 2001, development was started in 2002 and a three to four year mission was launched on March 5, 2009 with the possibility of a 2-year extension.  The mission is now in progress and much of the future of the exoplanet search is dependent upon the successful results of the Kepler mission.

Back to Goldilocks.  In 2010 astronomers reported that they had found the first Goldilocks planet orbiting Gliese 370 and another orbiting Gliese 581.  A controversy erupted in 2011 disputing Goldilocks having been found.  Reports appear to support the possibility that neither cited Goldilocks is truly Goldi-locks.

The possibility of Kepler 22b being Goldilocks is more probable, though, as stated earlier, there is much additional research that must be performed before a final decision is rendered.  Some information, as reported by Yahoo News, follows.

“The most Earth-like planet ever discovered is circling a star 600 light years away, . . . “ and is one of “. . . about 150,000 stars in the constellations Cygnus and Lyra, . . .” 

“The planet, called Kepler 22b, joins a list of more than 500 planets found to orbit stars beyond our solar system.  It is the smallest and the best positioned to have liquid water on its surface – among the ingredients necessary for life on Earth.  This is the first detection of a potentially habitable world orbiting a Sun-like star, scientists reported in findings to be published in The Astrophysical Journal.”

Kepler 22b, which is about 2.4 times the radius of Earth, sits squarely in its star’s so-called habitable zone. . . Follow-up studies are under way to determine if the planet is solid, like Earth, or more gaseous, like Neptune. . . . If Kepler 22b has a surface and a cushion of atmosphere similar to Earth’s, it would be about 72 degrees F (22 C), about the same as a spring day in Earth’s temperate zone.”

It should be noted that the planet could be solid and rocky and have the atmosphere and temperature similar to Earth, but unlike Earth, which has 70% of its surface covered by water, be completely covered by water – in effect, an ocean planet – with no dry land mass.  The possibility also exists that the planet could have water, but less than needed to be a viable candidate. Presently, there are more than 2,300 candidate planets found by the Kepler team.  Only 10 are roughly Earth-size and reside in the host stars’ habitable zone.  All will be subjected to extensive testing to determine if they are capable of supporting life, as we know it. 

As if that news wasn’t sufficiently exciting, while I was writing this story the media reported on December 21 that the Kepler mission had discovered a group of five planets orbiting Kepler 20 in the constellation Lyra about 1,000 light years away.  In this instance there are two rocky planets, Kepler 20e and 20f, and three Neptune-sized gas giants orbiting their star at a distance less than Mercury is to our Sun.  Because of the tight orbit it is believed at this time that the two rocky planets, while being of the right size,  are too hot to permit water in liquid form and so doubtful to support life as we know it. 

Which raises another question.  What about other life forms that don’t match ours?

I hope this essay will be found both informative and interesting.  The discoveries are new and current and I have tried not to stray from the facts in making my presentation, but if in the time that follows you find some discrepancies, I apologize, it was not intentional. 

December 2011

LFC