European astronomers have claimed to discover at least 16 new so-called “Super-Earths” —planets similar to our own but many times denser— of which one is potentially habitable.
The European Southern Observatory (ESO) said the exoplanets were seen through the High Accuracy Radical velocity Planet Searcher (HARPS) telescope in Chile.
“The harvest of discoveries from HARPS has exceeded all expectations and includes an exceptionally rich population of super-Earths and Neptune-type planets hosted by stars very similar to our Sun. And even better — the new results show that the pace of discovery is accelerating,” HARPS team leader Michel Mayor (University of Geneva, Switzerland) said in a news release.
One of the 16 Super-Earths orbits at the edge of the habitable zone of its star, the team found.
Also, the team has found that about 40 percent of stars similar to the Sun have at least one planet lighter than Saturn.
The ESO said this is the largest number of such planets ever announced at one time.
In the eight years since it started surveying stars like the Sun using the radial velocity technique, HARPS has been used to discover more than 150 new planets.
HARPS had discovered two-thirds of all the known exoplanets with masses less than that of Neptune.
Astronomers working with HARPS observations of 376 Sun-like stars have also improved their estimate of how likely a star like the Sun can host to low-mass planets.
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organization in Europe and the world’s most productive astronomical observatory.
It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom.
A habitable planet?
One of the newly discovered planets, HD 85512 b, is estimated to be only 3.6 times the mass of the Earth and is located at the edge of the habitable zone, ESO said.
The ESO described the habitable zone as “a narrow zone around a star in which water may be present in liquid form if conditions are right.”
“This is the lowest-mass confirmed planet discovered by the radial velocity method that potentially lies in the habitable zone of its star, and the second low-mass planet discovered by HARPS inside the habitable zone,” said Lisa Kaltenegger (Max Planck Institute for Astronomy, Heidelberg, Germany and Harvard Smithsonian Center for Astrophysics, Cambridge, USA).
Kaltenegger is an expert on the habitability of exoplanets.
The ESO said increasing precision of the new HARPS survey now allows the detection of planets under two Earth masses.
It added HARPS is now so sensitive that it can detect radial velocity amplitudes of significantly less than 4 km/hour — less than walking speed.
“The detection of HD 85512 b is far from the limit of HARPS and demonstrates the possibility of discovering other super-Earths in the habitable zones around stars similar to the Sun,” added Mayor.
With the results, astronomers are more confident they are close to discovering other small rocky habitable planets around stars similar to our Sun.
Upgrades to HARPS, new instruments
The ESO said hardware and software upgrades may soon allow HARPS to search for rocky planets that could support life.
At least 10 nearby stars similar to the Sun were selected for a new survey, it added.
“These planets will be among the best targets for future space telescopes to look for signs of life in the planet’s atmosphere by looking for chemical signatures such as evidence of oxygen,” said Francesco Pepe (Geneva Observatory, Switzerland), the lead author of one of the recent papers.
“These stars had already been observed by HARPS and are known to be suitable for extremely precise radial velocity measurements. After two years of work, the team of astronomers has discovered five new planets with masses less than five times that of Earth,” the ESO added.
Meanwhile, new instruments are planned to further this search.
These include a copy of HARPS to be installed on the Telescopio Nazionale Galileo in the Canary Islands, to survey stars in the northern sky, as well as a new and more powerful planet-finder, called ESPRESSO, to be installed on ESO’s Very Large Telescope in 2016.
Also, the CODEX instrument on the European Extremely Large Telescope (E-ELT) will push this technique to a higher level.
“In the coming 10 to 20 years we should have the first list of potentially habitable planets in the Sun’s neighborhood. Making such a list is essential before future experiments can search for possible spectroscopic signatures of life in the exoplanet atmospheres,” said Mayor, who discovered the first-ever exoplanet around a normal star in 1995.
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