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Nemesis is a hypothetical hard-to-see red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50000 to 100000 AU (about 0.8-1.5 light-years), somewhat beyond the Oort cloud.[1] This star was originally postulated to exist as part of a hypothesis to explain a perceived cycle of mass extinctions in the geological record, which seem to occur once every 27 million years or so. In addition, observations by astronomers of the sharp edges of Oort clouds, similar to that of the Solar System, around various binary (double) star systems, in contrast to the diffuse edges of the Oort clouds around single-star systems, has prompted some scientists to postulate that a dwarf star may be co-orbiting the Sun. Counter-theories also exist that other forces (like the angular effect of the galactic gravity plane) may be the cause of the sharp-edged Oort cloud pattern around the Sun. To date the issue remains unsettled in the scientific community. Claimed periodicity of mass extinctionsIn 1984, paleontologists David Raup and Jack Sepkoski published a paper claiming that they had identified a statistical periodicity in extinction rates over the last 250 million years using various forms of time series analysis. They focused on the extinction intensity of fossil families of marine vertebrates, invertebrates, and protozoans, identifying 12 extinction events over the time period in question. The average time interval between extinction events was determined as 26 million years. At <b>…</b>

Source: YouTube

What happens when we find life outside our own planet? Discovery Channel brings viewers on a virtual mission of the future. Right now, the search for planets with "life signatures" goes on. These efforts are global, and experts tell us on camera how this search for life is progressing around the world. No longer just the domain of science fiction, what could alien life really look like? Alien Planet dramatizes an exciting — and possible — answer. The drama takes place on Darwin IV, a fictional planet 6.5 light-years from Earth, with two suns and 60 percent gravity. Having identified Darwin as a world that could support life, Earth sends a pilot mission consisting of the mothership Von Braun and three probes: Balboa, Da Vinci and Newton. This unmanned fleet is responsible for finding and assessing any life-forms on Darwin IV. Initially, the expectation is to find microscopic life, but the probes soon find themselves in the middle of a developed ecosystem teeming with life of all sizes. The viewer experiences Darwin IV through the "eyes" of the probes Ike (Newton) and Leo (Da Vinci), whose data is relayed back to the mothership and then communicated to Earth. The biological and atmospheric data from the probes and mothership are relayed to viewers through computer voice simulation and on-screen readouts. Real scientists consider data in this planetary environment. They discuss the larger issues of the possibilities of life outside our solar system and deconstruct the <b>…</b>

Source: YouTube

What happens when we find life outside our own planet? Discovery Channel brings viewers on a virtual mission of the future. Right now, the search for planets with "life signatures" goes on. These efforts are global, and experts tell us on camera how this search for life is progressing around the world. No longer just the domain of science fiction, what could alien life really look like? Alien Planet dramatizes an exciting — and possible — answer. The drama takes place on Darwin IV, a fictional planet 6.5 light-years from Earth, with two suns and 60 percent gravity. Having identified Darwin as a world that could support life, Earth sends a pilot mission consisting of the mothership Von Braun and three probes: Balboa, Da Vinci and Newton. This unmanned fleet is responsible for finding and assessing any life-forms on Darwin IV. Initially, the expectation is to find microscopic life, but the probes soon find themselves in the middle of a developed ecosystem teeming with life of all sizes. The viewer experiences Darwin IV through the "eyes" of the probes Ike (Newton) and Leo (Da Vinci), whose data is relayed back to the mothership and then communicated to Earth. The biological and atmospheric data from the probes and mothership are relayed to viewers through computer voice simulation and on-screen readouts. Real scientists consider data in this planetary environment. They discuss the larger issues of the possibilities of life outside our solar system and deconstruct the <b>…</b>

Source: YouTube

Since its launch in March, 2009, the Kepler Mission has announced the discovery of 9 confirmed exoplanets (or planets outside our solar system). This video explores how the team works to combine photometry from the spacecraft, data from ground-based observatories and precise asteroseismic analysis to determine if Earths are common or rare in our Galaxy. For more information about the Kepler Mission, please visit www.nasa.gov

Source: YouTube