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Scientists discover “near”-Earth 40 light years away

December 18th, 2009
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This artist's rendering of what GJ 1214 might look like with its rocky explanet transiting in front of the M-Class Dwarf star. Courtesy of the New York Times article.

Last month I wrote about the recent discoveries that the H2Oceans on Europa, one of the Jovian moons.  Europa is intriguing largely because the gravitational and magnetic forces of Jupiter create enough of a tidal effect that Europa is kept warm and the oceans do not freeze over.  Factor in much higher oxygenation of said oceans and scientists have determined that it’s theoretically possible for complex organisms that consume as much oxygen as an Earth trout to exist.

That’s wicked awesome.  But what could be more awesome than the real hypothesis for habitable zones in the solar system?  What about finding habitable zones in the search for exoplanets?  Scientists announced that they came very close with a rocky exoplanet recently.

For those unfamiliar, exoplanets are planets that exist outside of our solar system, AKA orbiting another another star.  Although they had long been theorized, the actual discovery can most easily be done by one of three methods that have been mastered in the last 15 years: Astrometry, which looks at the wobbles and changes in the celestial path of a star reflecting gravitational influence by a large orbiting body; Radial Velocity, which measures the changes in the redshift of a star’s light by looking at the speeding up or slowing down of the star caused by orbiting bodies as it moves further away from the Earth; or Transit Method, which looks for changes in the light visible from a star as exoplanets move in front of a star as viewed from Earth.

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There are other methods of observing exoplanets, but those are the three primary means of detection.  Pulsar Timing, which measures erratic signals from pulsars, also is a reliable method for finding exoplanets; however, anything orbiting a pulsar would be so different from Earth that one cannot fathom them as having a habitable zone.  In fact, given that pulsars are stars that have gone supernova, its somewhat mysterious that exoplanets are able to form via accretion from post-nova dust disks.  It is almost impossible to imagine any body that predated the nova could survive a blast or at least stay in orbit post-explosion.

THis animated GIF shows the wobble of a star created by a planet's orbit.  The wobble is because both the planet and the star orbit around their common center of gravity.

This animated GIF shows the wobble of a star created by an exoplanet's orbit. The wobble is because both the exoplanet and the star orbit around their common center of gravity.

Of the three methods, Astrometry is least likely to detect an Earth-like rocky exoplanet, as the observable wobble or variances in a star’s celestial path are so faint that an exoplanet would almost certainly have to be a super-massive gas giant in order to effect enough of a shift to be viewable.  Although Radial Velocity also relies on gravitational impact of the exoplanet or exoplanets on a star, the ability to measure redshift is more simple than observing a wobble.  The frequency with which a star’s light shifts to the red part of the spectrum (indicating that a star is moving away from the Earth at a certain speed) is measurable at fine increments.  As an exoplanet orbits a star, the speed with which the star moves away from Earth (all stars are moving away from the Earth due to universal expansion post-Big Bang) increases and decreases slightly.  This is detectable for much smaller exoplanets and is a means by which one can prove the existence of and then identify and study rocky exoplanets.

Transit Method is useful largely for closer stars and is more effective for larger exoplanets because it relies on a exoplanet blocking visible light when the exoplanet transits the star in front of the Earth — think of viewing a solar eclipse but with an exoplanet going in front of another star, instead of the moon going in front of the Sun.  Transits also can occur in our solar system with Mercury and Venus, with Mercury being the most common with its rapid orbit.

Anyways, I’ve gotten off track.  The discovery of an exoplanet, referred to as a “Super Earth” about three times larger and six times more massive than Earth, was made around the star GJ 1214.  The exciting thing is that GJ 1214 is only 40 light years from us, making the study of the star and its exoplanetary system all the more possible.  Heck, 40 light years is also within the realm of possibility for interstellar travel when the technology is ripe.  It is 40 years away at the speed of light.  Yes, humans are nowhere near to being able to travel at that speed, but it is far more feasible than finding and traveling or sending probes to an exoplanet 1000 light years away.  More importantly, the closer the exoplanetary system, the easier it is to study with telescopes like the Hubble and the Spitzer Space Telescope.

The orbit of Eris, Pluto's sister dwarf planet discovered recently, shows a distant, but extremely eccentric orbit.  Conversely, the planets are far more standardized, with limited eccentricity.

The orbit of Eris, Pluto's sister dwarf planet discovered recently, shows a distant, but extremely eccentric orbit. Conversely, the planets are far more standardized, with limited eccentricity.

Already, the scientists studying GJ 1214b (the exoplanet’s designation) have determined that it has a significant water component, likely in liquid or near-liquid states.  The temperature on GJ 1214b is about 400 degrees Fahrenheit, significantly higher than the boiling point on Earth; however, the added pressure of the exoplanet’s atmosphere caused by its mass and gravity create atmospheric conditions that make it more likely to be in a super-hot liquid state with some steam action.  Scientists feel that the planet is likely just outside the “habitable zone” for life, but its discovery still represents a big step toward finding the first exoplanet on which life might exist.

The habitable zone of a planet is defined as the narrow band of orbits that exist close enough to the host star that the exoplanet is not an ice-ball, but far enough away that it doesn’t boil or get burnt by the star.  One of the initial complexities was finding planets with standardized orbits like those in our solar system.  Many of the initial exoplanets discovered were both gas giants and had highly eccentric orbits that would take them from very far to very close to their stars.

Of the 400 exoplanets discovered in the last 15 years, increasingly more are rocky Super Earths, but none have existed with a standard orbit in the habitable zone.  This was the closest scientists have come yet.  It was discovered using the Planetary Transit method which showed that the light from GJ 1214 dipped every 36 hours.  Upon further study, the mass and gravitational tug was determined and the calculations led folks to determine that the exoplanet was a water world with 1/3rd the density of the Earth.

In addition to the discovery of GJ 1214b, scientists announced the discovery of several other exoplanets around various stars this week in a series of papers.  Estimates say that between ten and thirty percent of M-Class and M-Class dwarf stars have rocky exoplanets.  Given the number of stars within our local area, it is only a matter of time now before we are able to identify and study exoplanets that could support life.

Not discussed, but made more interesting by the study of Europa is the possibility of habitable zones on moons of gas giants larger than Jupiter and Saturn.  Life on moons of such gas giants would likely have to survive on geothermal or tidal energy, rather than sunlight.  As such, it would likely be limited to the type of life that exists near the Earth’s geothermic vents, but it still is an interesting possibility — even if we’d like to think an Endor could be out there.

The three best articles I found on the subject are linked below:

New York Times article

Time article

Daily Galaxy article

Also worth watching and of particular interest in thinking about the scale of what we’re just beginning to explore is this outstanding piece from the Museum of Natural History.

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