{"id":19447,"date":"2016-03-01T18:47:13","date_gmt":"2016-03-01T10:47:13","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/how-to-do-a-reality-check-on-the-search-for-life-beyond-our-solar-system\/"},"modified":"2016-03-01T18:47:13","modified_gmt":"2016-03-01T10:47:13","slug":"how-to-do-a-reality-check-on-the-search-for-life-beyond-our-solar-system","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/how-to-do-a-reality-check-on-the-search-for-life-beyond-our-solar-system\/","title":{"rendered":"How to do a reality check on the search for life beyond our solar system"},"content":{"rendered":"
\"Image:
When Earth passes in front of the sun, it blocks a small part of the sun\u2019s light. Potential observers outside our solar system might be able to detect the resulting dimming of the sun and study Earth\u2019s atmosphere. (Credit: Axel Quetz \/ MPIA \/ NASA)<\/figcaption><\/figure>\n

The past decade has brought about a revolution in astronomers\u2019 ability to detect potentially habitable planets, and there\u2019s much, much more to come. The problem will be identifying the likeliest places for life to lurk, and two newly published studies address that problem from two dramatically different perspectives.<\/p>\n

One study takes an inward-looking perspective: If we were the aliens, how would we know about Earth?<\/p>\n

The best planet-detection method that\u2019s currently available to earthly astronomers looks for the telltale dimming of light as a planet crosses the disk of its parent star. But that dimming, known as a planetary transit, can be seen only when the planet and the alien star are lined up with Earth.<\/p>\n

That suggests that Earth is most likely to be detected by observers on alien planets in a narrow strip of the sky where our planet can be seen crossing the sun.<\/p>\n

\"Transit
This image shows the narrow transit zone from which distant observers could see Earth pass in front of the sun. (Credit: Axel Quetz for MPIA \/ Axel Mellinger for Central Michigan University)<\/figcaption><\/figure>\n

The study, which is being published in the March issue of the journal Astrobiology, estimates that Earth\u2019s transit zone amounts to only 0.2 percent of the sky as seen from our planet. Potentially habitable planets that lie in that strip should be put at the top of the list in the search for extraterrestrial intelligence, or SETI, the study\u2019s authors say.<\/p>\n

\u201cThe key point of this strategy is that it confines the search area to a very small part of the sky,\u201d Rene Heller, an astronomer at the Max Planck Institute for Solar System Research, said in a news release. \u201cAs a consequence, it might take us less than a human life span to find out whether or not there are extraterrestrial astronomers who have found the Earth. They may have detected Earth\u2019s biogenic atmosphere and started to contact whoever is home.\u201d<\/p>\n

Heller and the study\u2019s other co-author, McMaster University\u2019s Ralph Pudritz, estimate that about 100,000 nearby stars could harbor planets with inhabitants who could be trying to contact us. And they list 82 sunlike stars in the transit zone that are known to lie within 3,260 light-years of Earth and have a good chance of hosting habitable planets.<\/p>\n

https:\/\/www.youtube.com\/watch?v=7Hu3V9eULPY<\/p>\n

How can we be sure which of those planets harbor life? The other study suggests a way to do a reality check on readings that NASA\u2019s James Webb Space Telescope is expected to get after its launch in 2018.<\/p>\n

The Webb telescope should be good enough to determine the ingredients in the atmospheres of thousands of planets far beyond our solar system, including oxygen. On Earth, oxygen is considered a \u201cbiosignature\u201d associated with life\u2019s presence \u2013 but on extrasolar planets, that ain\u2019t necessarily so.<\/p>\n

For example, astronomers already have detected oxygen as well as carbon in the atmosphere of a \u201chot Jupiter\u201d called HD 209458 b. However, the conditions there are in no way conducive to life. In this example, the detection of oxygen is a false positive for habitability.<\/p>\n

\u201cWe wanted to determine if there was something we could observe that gave away these \u2018false positive\u2019 cases among exoplanets,\u201d Edward Schwieterman, a doctoral student in astronomy at the University of Washington, said in a news release.<\/p>\n

Schwieterman and his colleagues lay out their strategy in a paper published last week in Astrophysical Journal Letters. They focused on a couple of scenarios that could produce atmospheric oxygen through non-biological means \u2013 particularly on planets orbiting low-mass stars.<\/p>\n