With thousands of known exoplanets and tens of thousands likely to be discovered in the coming decades, it could be only a matter of time before we discover a planet with life. The trick is proving it. So far the focus has been on observing the atmospheric composition of exoplanets, looking for\u00a0molecular biosignatures<\/a>\u00a0that would indicate the presence of life. But this can be difficult since many of the molecules produced by life on Earth could also be produced by geologic processes. A new study argues that a better approach would be to compare the atmospheric composition of a potentially habitable world with those of other planets in the star system.<\/span><\/p>\n <\/span><\/p>\n Since planets form within the debris disk of a young star, they will generally have similar compositions. Because of the migration of certain molecules such as water ice, the outer planets can have a slightly different composition than the inner planets, but overall their composition is similar. For this study, the team looked at the abundance of atmospheric carbon among worlds.<\/span><\/p>\n Carbon is not just a primary element for life on Earth, it also absorbs readily in water and can be bound geologically in rocks. So the idea is that if an exoplanet is in the potentially habitable zone of a star and has significantly less atmospheric carbon than similar worlds in its system, then that is a strong indicator of the presence of water and organic life. Take our solar system as an example. Earth, Venus, and Mars are all roughly in the habitable zone of the Sun, but both Venus and Mars have atmospheres comprised mostly of carbon dioxide. In contrast, Earth has an atmosphere of mostly nitrogen and oxygen, and only a fraction of a percent of carbon dioxide. Earth\u2019s atmospheric carbon is so dramatically different from that of Venus and Mars that it stands out as a likely inhabited world.<\/span><\/p>\n \n The Crab Reveals Its Secrets To JWST<\/span><\/a>The Crab Nebula \u2013 otherwise known as the first object on Charles Messier\u2019s list of non-cometary objects or M1 for short<\/span><\/p>\n It has been known that there is a pulsar at the core of the nebula, and it\u2019s this pulsar that is the true remains of the progenitor star.\u00a0 When it went \u2018supernova,\u2019 the core collapsed to form the ultra-dense rotating object that, if you happen to be in the right place in space (hey, that rhymes), then you will see a pulse of radiation as it rotates. The infrared images from JWST reveal synchrotron emissions, which are a direct result of the rapidly rotating pulsar.\u00a0 As the pulsar rotates, the magnetic field accelerates particles in the nebula to astonishingly high speeds such that they emit synchrotron radiation. As a fabulously lucky quirk of nature, the radiation is particularly obvious in infrared, making it ideal for JWST.\u00a0<\/span><\/p>\n \n Uranus Has Infrared Auroras, Too<\/span><\/a><\/p>\n Auroras happen when charged particles in the solar wind and near-planet environment get trapped by a planet\u2019s magnetic field. They funnel down to the atmosphere and collide with gas molecules. This happens on Earth and we see auroras over the north and south poles of our planet. They also happen at other planets. Astronomers detect them on the other giant planets, and a smaller version of them occurs on Mars. Venus probably doesn\u2019t experience similar types of auroral displays, since it has no intrinsic magnetic field. However, it may experience something like them during particularly gusty solar wind events. At the outer planets, the gas mix is different in the atmospheres. That means their aurorae show up in ultraviolet and infrared wavelengths.<\/span><\/p>\n Uranus has an interesting magnetic field. It does not originate from the exact center of the planet. It\u2019s also offset by 59 degrees from the rotation axis. That\u2019s tipped 90 degrees from the plane of the solar system. This arrangement means that the Uranian magnetosphere is asymmetric and its field strengths vary depending on location. It connects with the solar wind once every Uranian day (which is 17 hours long). The planet does show some auroral activity, particularly around the poles and\u00a0<\/span>Hubble Space Telescope detected some in 2011<\/a><\/p>\n \n Three Planets Around this Sunlike Star are Doomed. Doomed!<\/span><\/a>According to new research we can start writing the eulogy for four exoplanets around a Sun-like star about 57 light years away. But there\u2019s no hurry; we have about one billion years before the star becomes a red giant and starts to destroy them.<\/span><\/p>\n The star is Rho Coronae Borealis, a yellow dwarf star like our Sun. It\u2019s in the constellation Corona Borealis, and has almost the same mass, radius, and luminosity as the Sun. The difference is in their ages. The Sun is about five billion years old, but Rho CrB is twice that, which means its red giant phase is imminent, at least in astrophysical terms.<\/span><\/p>\n Post main sequence stellar evolution can result in dramatic, and occasionally traumatic, alterations to the\u00a0planetary system architecture, such as tidal disruption of planets and engulfment by the host star,\u201d Kane writes. Rho Coronae Borealis is both old and bright, making it \u201c\u2026 a particularly interesting case of advanced main sequence evolution,\u201d according to Kane. Not only because its similar to the Sun and easily observed, but also because it hosts four exoplanets.<\/span><\/p>\n \n <\/p>\n White Dwarfs Could Support Life. So Where are All Their Planets?<\/span><\/a><\/p>\n<\/header>\n Astronomers have found plenty of white dwarf stars surrounded by debris disks. Those disks are the remains of planets destroyed by the star as it evolved. But they\u2019ve found one intact Jupiter-mass planet orbiting a white dwarf.<\/span><\/p>\n Are there more white dwarf planets? Can terrestrial, Earth-like planets exist around white dwarfs?<\/span><\/p>\n <\/span><\/p>\n A white dwarf (WD) is the stellar remnant of a once much-larger main sequence star like our Sun. When a star in the same mass range as our Sun leaves the\u00a0main sequence<\/a>, it swells up and becomes a red giant. As the red giant ages and runs out of nuclear fuel, it sheds its outer layers as a\u00a0planetary nebula<\/a>, a shimmering veil of expanding ionized gas that everybody\u2019s seen in Hubble images. After about 10,000 years, the planetary nebula dissipates, and all that\u2019s left is a white dwarf, alone in the center of all that disappearing glory.<\/span><\/p>\n![](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2023\/10\/Crab-1.jpeg\")
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