Humans are closer to finding an Earth-like inhabitable planet

Humans are closer to finding an Earth-like inhabitable planet

According to a new study, discovery of multi-planet systems is much more likely than ever, hinting that one or more planets in those systems can be like Earth

 

Jojo Puthuparampil 

 

Astronomers have always been intrigued by exoplanets (planets outside the solar system) as they possibly offer a clue to finding an Earth-like planet in the outer space that supports life. According to a new study, published in Astrophysical Journal, humans are one step closer to finding an ‘inhabitable’ planet within the solar system. The study, based on data from NASA’s Kepler spacecraft which envisions to discover Earth-like planets orbiting other stars, says discovery of multi-planet systems is much more likely than ever, hinting that one or more planets in those systems can be like Earth.

 

The spacecraft, named in honour of the 17th-century German astronomer Johannes Kepler, has since its inception in March 2009 identified 1,235 planetary candidates in 997 host star systems. Of these candidates, 759 are confirmed exoplanets, including 54 that may be in the habitable zone, the region around a star where liquid water, and thus life, can exist. For instance, one of the newly discovered worlds, dubbed HD 85512b, lies at the edge of its star's habitable zone. According to the study co-author Elisabeth Adams, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, of the 997 planetary systems, 170 have multiple planet candidates, implying the chance of one or a few of them being Earth-like, possibly with life-supporting elements like water.

 

Kepler looks for Earth-size planets around Sun-like stars. It has an inbuilt photometer that continually monitors the brightness of over 145,000 main sequence stars which are known for longevity and stability. With the help of this photometer, it spots potential alien worlds by staring at a patch of sky and watching for dips in starlight caused by objects transiting their stars, as seen from Earth. For instance, if a planet’s orbital period is 10 days, it will pass in front of the parent star every 10 days, resulting in a dip in the light emanating from the star. This data is transmitted to Earth, then analysed to detect periodic dimming caused by extrasolar planets that cross in front of their host stars.

 

But simply seeing a transit isn't enough to prove a planet is involved. Some other phenomenon, such as a smaller star passing in front of its much larger neighbour, could be causing the main star to dim periodically. Therefore, astronomers rely on other methods such as ‘radial velocity’ and ‘transit timing variation’ to confirm that the spotted body is indeed a planet. In the study, Adams and colleagues ran a statistical analysis and found that, if a star system has multiple planet candidates, the confirmation step can be skipped, as most planet candidates in multi-planet systems are likely to be ‘real’ planets.

 

Discovery of multi-planet systems also helps astronomers look at multiple worlds that were born together to get a better understanding of planetary transformations and hence deeper insights into Earth’s formative years after the Big Bang.

 

Scientists are enthused by Kepler’s recent discovery of Kepler-22b, a planet about 2.4 times the radius of Earth, in the habitable zone of its star. They do not yet know if it has a rocky, gaseous or liquid composition, but they feel its discovery is a step closer to finding Earth-like planets. Kepler has also found two other planets with higher atmospheric densities, suggesting they have atmospheres of mostly water, and therefore conducive for life to sprout. Spotting water in any of the Earth-like planets is the biggest leg-up astronomers are expecting in their search of life elsewhere.

 

The findings of Kepler are supplemented by data from High Accuracy Radial Velocity Planet Searcher (HARPS) at the European Southern Observatory's La Silla facility in Chile. HARPS recently found 50 new alien worlds, including 16 ‘super Earths’. Astronomers use Doppler wobble technique which involves searching for wobbles in a star's light that indicate the gravitational pull of an orbiting planet. The method helps them find massive planets that orbit close to their host stars. In 2007, HARPS discovered a super-Earth, called Gliese 581d, that is believed to be lying within the habitable zone of its star.

 

Scientists plan to upgrade HARPS hardware and software and use the instrument to conduct a more refined search of nearby Sun-like stars for rocky Earth-like planets that could support life. They are encouraged by the fact that there has been a significant increase in the number of rocky exoplanets discovered by space missions, including Kepler and HARPS. They expect that in 10 to 20 years, humans should have the first list of potentially habitable planets in the Sun's neighborhood, according to another study by Michel Mayor, an astronomer at the University of Geneva in Switzerland. One of those would-be-discovered planets, they hope, may splash chemical signs of life—such as oxygen—in their atmospheres, helping unicellular organisms to evolve.