![]() ![]() In April and May 2018, the star was found in the course of studying the supernova SN Refsdal with the Hubble Space Telescope. Ultraviolet light is redshifted into the visible range and the star appears reddish. History Comparison of observed data of the star Icarus with a model of a blue supergiant star spectrum. According to co-discoverer Patrick Kelly, the star is at least a hundred times more distant than the next-farthest non- supernova star observed, SDSS J1229+1122, and is the first magnified individual star seen. Light from the star was emitted 4.4 billion years after the Big Bang. Earendel, as of March 2022), at approximately 14 billion light-years from Earth ( redshift z=1.49 comoving distance of 14.4 billion light-years lookback time of 9.34 billion years). It is the second most distant individual star to have been detected so far (second only to WHL0137-LS, a.k.a. MACS J1149 Lensed Star 1, also known as Icarus, is a blue supergiant star observed through a gravitational lens. Our results suggest that mid-to-early K stars should be considered along with G stars as optimal candidates in the search for extraterrestrial life.Icarus, LS1, MACS J1149 LS1, MACS J1149 Lensed Star 1 (LS1), MACS J1149+2223 Lensed Star 1 ![]() F stars have narrower (log distance) CHZ's than our Sun because they evolve more rapidly. Planets orbiting late K stars and M stars may not be habitable, however, b ecause they can become trapped in synchronous rotation as a consequence of tidal damping. For a specified period of habitability, CHZs around K and M stars are wider (in log distance) than for our Sun because these stars evolve more slowly. The width of the CHZ around other stars depends on the time that a planet is required to remain habitable and on whether a planet that is initially frozen can be thawed by modest increases in stellar luminosity. A log distance scale is probably the appropriate scale for this problem because the planets in our own Solar System are spaced logarithmically and because the distance at which another star would be expected to form planets should be related to the star's mass. Nevertheless, the widths of all of these HZs are approximately the same if distance is expressed on a logarithmic scale. The HZ around an F star is larger and occurs farther out than for our Sun the HZ around K and M stars is smaller and occurs farther in. Stars later than F0 have main sequence lifetimes exceeding 2 Gyr and, so, are also potential candidates for harboring habitable planets. A conservative estimate for the width of the 4.6-Gyr continuously habitable zone (CHZ) is 0.95 to 1.15 AU. The HZ evolves outward in time because the Sun increases in luminosity as it ages. The width of the HZ is slightly greater for planets that are larger than Earth and for planets which have higher N2 partial pressures. Between these two limits, climate stability is ensured by a feedback mechanism in which atmospheric CO2 concentrations vary inversely with planetary surface temperature. Conservative estimates for these distances in our own Solar System are 0.95 and 1.37 AU, respectively the actual width of the present HZ could be much greater. The outer edge of the HZ is determined by the formation of CO2 clouds, which cool a planet's surface by increasing its albedo and by lowering the convective lapse rate. The inner edge of the HZ is determined in our model by loss of water via photolysis and hydrogen escape. Our basic premise is that we are dealing with Earth-like planets with CO2/H2O/N2 atmospheres and that habitability requires the presence of liquid water on the planet's surface. A one-dimensional climate model is used to estimate the width of the habitable zone (HZ) around our Sun and around other main sequence stars. ![]()
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