Alien Atmospheres

Click HERE for FULL STORY about this exciting discovery.Click for quick link to soundbites from interview with Dr. Jennifer Wiseman. Canned interview with Dr. Jennifer Wiseman/ Hubble Senior ScientistTRT 7:45 Its size and surface gravity are much larger than Earth’s, and its radiation environment may be hostile, but a distant planet called K2-18b has captured the interest of scientists all over the world. For the first time, researchers have detected water vapor signatures in the atmosphere of a planet beyond our solar system that resides in the "habitable zone," the region around a star in which liquid water could potentially pool on the surface of a rocky planet.Astronomers at the Center for Space Exochemistry Data at the University College London in the United Kingdom used data from NASA’s Hubble Space Telescope to find water vapor in the atmosphere of K2-18b, an exoplanet around a small red dwarf star about 110 light-years away in the constellation Leo. If confirmed by further studies, this will be the only exoplanet known to have both water in its atmosphere and temperatures that could sustain liquid water on a rocky surface. Liquid water would only be possible if the planet turns out to be terrestrial in nature, rather than resembling a small version of Neptune.Given the high level of activity of its red dwarf star, K2-18b may be more hostile to life as we know it than Earth, as it is likely to be exposed to more high-energy radiation. The planet, discovered by NASA's Kepler Space Telescope in 2015, also has a mass eight times greater than Earth's. That means the surface gravity on this planet would be significantly higher than on our planet.The team used archive data from 2016 and 2017 captured by Hubble and developed open-source algorithms to analyze the host star’s light filtered through K2-18b’s atmosphere. The results revealed the molecular signature of water vapor, and also suggest the presence of hydrogen and helium in the planet’s atmosphere.The authors of the paper, published in Nature Astronomy, believe that other molecules, including nitrogen and methane, may be present but they remain undetectable with current observations. Further studies are required to estimate cloud coverage and the percentage of atmospheric water present. A paper from a different team of scientists using Hubble observations has been submitted to the Astronomical Journal.K2-18b is one of hundreds of "super-Earths" — exoplanets with masses between those of Earth and Neptune — found by Kepler. NASA’s TESS mission is expected to detect hundreds more super-Earths in the coming years. The next generation of space telescopes, including the James Webb Space Telescope, will be able to characterize exoplanet atmospheres in more detail.The Hubble Space Telescope is a project of international cooperation between ESA (the European Space Agency) and NASA. Related pages

ANIMATION Using NASA’s Hubble Telescope, scientists detected a stratosphere on the planet WASP-33b. A stratosphere occurs when molecules in the atmosphere absorb ultraviolet and visible light from the star. This absorption warms the stratosphere and acts as a kind of sunscreen layer for the planet below.Watch this video on YouTube. ILLUSTRATION WASP-33b’s stratosphere was detected by measuring the drop in light as the planet passed behind its star (top). Temperatures in the low stratosphere rise because of molecules absorbing radiation from the star (right). Without a stratosphere, temperatures would cool down at higher altitudes (left). STILL IMAGE Artist concept of the giant planet WASP-33b transiting its sun, the Delta Scuti variable star WASP-33 (HD 15082). Using NASA’s Hubble Space Telescope, scientists have detected a stratosphere, one of the primary layers of Earth’s atmosphere, on a massive and blazing-hot exoplanet known as WASP-33b.The presence of a stratosphere can provide clues about the composition of a planet and how it formed. This atmospheric layer includes molecules that absorb ultraviolet and visible light, acting as a kind of “sunscreen” for the planet it surrounds. Until now, scientists were uncertain whether these molecules would be found in the atmospheres of large, extremely hot planets in other star systems.Learn more on NASA.gov. For More InformationSee [NASA.gov](http://www.nasa.gov/press-release/nasa-s-hubble-telescope-detects-sunscreen-layer-on-distant-planet) Related pages

Scientists find creative ways to study the many planets that exist beyond our solar system. Find out more about the methods used to explore exoplanets by watching this video. When a planet crosses in front of a star, some of the star's light is absorbed, and some is transmitted, passing through the planet's atmosphere. During a transit, a planet’s size can be determined by measuring the observed decrease in brightness of its star. Scientists can identify which chemicals are present in a planet’s atmosphere by separating transmitted light into a spectrum of colors. Related pages

NASA's Kepler mission has discovered two new planetary systems that include three super-Earth-size planets in the habitable zone, the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. Two of the newly discovered planets orbit a star smaller and cooler than the sun. Kepler-62f is only 40 percent larger than Earth, making it the exoplanet closest to the size of our planet known in the habitable zone of another star. Kepler-62f is likely to have a rocky composition. Kepler-62e, orbits on the inner edge of the habitable zone and is roughly 60 percent larger than Earth. The third planet, Kepler-69c, is 70 percent larger than the size of Earth, and orbits in the habitable zone of a star similar to our sun. Astronomers are uncertain about the composition of Kepler-69c, but its orbit of 242 days around a sun-like star resembles that of our neighboring planet Venus. Scientists do not know whether life could exist on the newfound planets, but their discovery signals we are another step closer to finding a world similar to Earth around a star like our sun. Diagrams show super-Earth-size planets discovered by Kepler. Diagrams show super-Earth-size planets discovered by Kepler. Diagrams show super-Earth-size planets discovered by Kepler. Diagrams show super-Earth-size planets discovered by Kepler. For More InformationSee [kepler.nasa.gov/Mission/discoveries](kepler.nasa.gov/Mission/discoveries) Related pages

Short narrated videoFor complete transcript, click here. This artist's rendering illustrates the evaporation of HD 189733b's atmosphere in response to a powerful eruption from its host star. NASA's Hubble Space Telescope detected the escaping gases and NASA's Swift satellite caught the stellar flare. Swift's Ultraviolet/Optical Telescope captured this view of HD 189733b's host star on Sept. 14, 2011. The image is 6 arcminutes across. Credit: NASA/Swift/Stefan Immler Strong X-ray emission makes the host star of HD 189733b stand out in this view from Swift's X-Ray Telescope. The image combines data from Sept. 13 and 14, 2011, and is 6 arcminutes across. Credit: NASA/Swift/Stefan Immler An international team of astronomers using data from NASA's Hubble Space Telescope has detected significant changes in the atmosphere of a planet located beyond our solar system. The scientists conclude the atmospheric variations occurred in response to a powerful eruption on the planet's host star, an event observed by NASA's Swift satellite.The exoplanet is HD 189733b, a gas giant similar to Jupiter, but about 14 percent larger and more massive. The planet circles its star at a distance of only 3 million miles, or about 30 times closer than Earth's distance from the sun, and completes an orbit every 2.2 days. Its star, named HD 189733A, is about 80 percent the size and mass of our sun.Astronomers classify the planet as a "hot Jupiter." Previous Hubble observations show that the planet's deep atmosphere reaches a temperature of about 1,900 degrees Fahrenheit (1,030 C).HD 189733b periodically passes across, or transits, its parent star, and these events give astronomers an opportunity to probe its atmosphere and environment. In a previous study, a group led by Lecavelier des Etangs used Hubble to show that hydrogen gas was escaping from the planet's upper atmosphere. The finding made HD 189733b only the second-known "evaporating" exoplanet at the time.The system is just 63 light-years away, so close that its star can be seen with binoculars near the famous Dumbbell Nebula. This makes HD 189733b an ideal target for studying the processes that drive atmospheric escape.When HD 189733b transits its star, some of the star's light passes through the planet's atmosphere. This interaction imprints information on the composition and motion of the planet's atmosphere into the star's light.In April 2010, the researchers observed a single transit using Hubble's Space Telescope Imaging Spectrograph (STIS), but they detected no trace of the planet's atmosphere. Follow-up STIS observations in September 2011 showed a surprising reversal, with striking evidence that a plume of gas was streaming away from the exoplanet.The researchers determined that at least 1,000 tons of gas was leaving the planet's atmosphere every second. The hydrogen atoms were racing away at speeds greater than 300,000 mph. Because X-rays and extreme ultraviolet starlight heat the planet's atmosphere and likely drive its escape, the team also monitored the star with Swift's X-ray Telescope (XRT). On Sept. 7, 2011, just eight hours before Hubble was scheduled to observe the transit, Swift was monitoring the star when it unleashed a powerful flare. It brightened by 3.6 times in X-rays, a spike occurring atop emission levels that already were greater than the sun's. Astronomers estimate that HD 189733b encountered about 3 million times as many X-rays as Earth receives from a solar flare at the threshold of the X class. For More InformationSee [http://www.nasa.gov/topics/universe/features/exoplanet-atmosphere.html](http://www.nasa.gov/topics/universe/features/exoplanet-atmosphere.html) Related pages

Artist's interpretation of what the exoplanet, flare, and atmosphere loss might have looked like. Second still from animation The exoplanet HD 189733b lies so near its star that it completes an orbit every 2.2 days. In late 2011, NASA's Hubble Space Telescope found that the planet's upper atmosphere was streaming away at speeds exceeding 300,000 mph. Just before the Hubble observation, NASA's Swift detected the star blasting out a strong X-ray flare, one powerful enough to blow away part of the planet's atmosphere. For More InformationSee [http://www.nasa.gov/topics/universe/features/exoplanet-atmosphere.html](http://www.nasa.gov/topics/universe/features/exoplanet-atmosphere.html) Related pages

Video feature describing the process and implications of the planetary color analysis.For complete transcript, click here. Planets plotted on color table. With labels. Planets plotted on color table. Additional still from video Additional still from video Additional still from video NASA astronomer Lucy McFadden and UCLA graduate Carolyn Crow recently made a discovery that will help identify characteristics of extrasolar planets, such as the compositions of their surfaces and atmospheres. By comparing the reflected red, blue, and green light from planets in our solar system, a team led by Crow and McFadden was able to group the planets according to their similarities. As it turns out, the planets fall into very distinct regions on this plot, where the vertical direction indicates the relative amount of blue light, and the horizontal direction the relative amount of red light. This technique works even when the source of the reflected light is visible only as a point, like exoplanets appear when observed through a telescope. Therefore, scientists can use it to identify earthlike planets more easily. For More InformationSee [http://www.nasa.gov/topics/universe/features/planet-colors.html](http://www.nasa.gov/topics/universe/features/planet-colors.html) Related pages