October 5, 2022

The James Webb Space Telescope will map the atmosphere of exoplanets

Exoplanets, worlds that orbit stars other than the sun, are discovered at ranges very far from Earth. My work is related to the characterization of exoplanet atmospheres. A transit occurs when, from our perspective, an exoplanet passes in front of its host star. (Image credit: ESA)In general, the environment of an exoplanet is thought about a one-dimensional object when examining it. Four instruments, consisting of Canadas NIRISS (Near-infrared Imager and Slitless Spectrograph), will observe in the infrared range and characterize the environments of a multitude of exoplanets.With the Webb telescope, it will be possible to use the mapping methods offered to us to determine the three-dimensional variation of exoplanet atmospheres.

Exoplanets, worlds that orbit stars aside from the sun, are discovered at ranges extremely far from Earth. For example, the closest exoplanet to us, Proxima Centauri b, is 4.2 light-years away, or 265,000 times the range between the Earth and the sun.To the naked eye, the planets in the planetary system appear as bright spots. Using a telescope, these dots stand out from the stars and reveal structures such as Jupiters Great Red Spot, Saturns rings, or the ice caps of Mars.Although the presence of such phenomena is expected on exoplanets, their range from the Earth prevents us from straight resolving their surface areas. There are ways to find out more about the structure of their environments and map them.Live updates: NASAs James Webb Space Telescope missionIn images: The Christmas launch of NASAs James Webb Space TelescopeI am a PhD trainee in astrophysics at the University of Montreal. My work is related to the characterization of exoplanet atmospheres. More particularly, my research study focuses on the advancement of tools to map the atmosphere of exoplanets using observations from the James Webb Space Telescope.The telescope, introduced on Dec. 25, 2021, is anticipated to reinvent the field of exoplanetary science. Detecting and characterizing exoplanetsApart from a couple of special cases where light from a world can be observed directly, most of exoplanets are spotted utilizing indirect approaches. An indirect technique includes observing the effect of the planets existence on the light produced by its star.The transit method has caused the biggest variety of exoplanet detections. A transit occurs when, from our point of view, an exoplanet passes in front of its host star. Throughout the transit, the light from the star decreases as the stars surface is partially obscured by the planet.Light is divided into a spectrum of wavelengths that represent various colours. When a transit is observed at several wavelengths, it is possible to measure the climatic structure of the exoplanet. Water particles highly soak up light in the infrared wavelengths, making the world appear bigger, considering that its environment blocks a larger fraction of the light from its star. In a similar method, it is also possible to measure the temperature of the atmosphere and to detect the presence of clouds.In addition, a transiting world can likewise pass behind its star. This phenomenon, in which just the light from the star is observed, is called secondary eclipse. By observing this, it is possible to isolate the light coming only from the world and hence get additional details about its atmosphere.The transit method is more conscious the presence of clouds, while the secondary eclipse method offers more details about the temperature level of the atmosphere.Schematic of a world around its star and the light coming from the system according to its position. (Image credit: ESA)In general, the atmosphere of an exoplanet is considered a one-dimensional object when analyzing it. That is, its composition and temperature level are thought about to differ just with altitude and not with its position in longitude and latitude. To take these 3 measurements into account concurrently would require complicated models along with a high degree of observational accuracy. Solely considering altitude might produce approximations that are not valid. On Earth, for example, the temperature level at the equator is much greater than at the poles.Some exoplanets also have strong spatial variation in their environments. Hot Jupiters, comparable in size to Jupiter, orbit extremely close to their host star and can hence reach temperatures of a number of thousand degrees Celsius.In addition, these planets normally revolve around themselves at the same speed as they do around their star. This means that on these worlds, a day and a year are the exact same length. In the exact same method that we can just see one side of the Moon from Earth, only one side of a hot Jupiter constantly faces its star. This phenomenon can cause a large temperature difference in between the day side, which is lit up by the star, and the night side, which is constantly in darkness.Mapping methodsAlthough it is impossible to observe the surface of an exoplanet directly, it is possible to measure the spatial variation of the atmosphere utilizing 2 techniques: phase curve analysis and secondary eclipse mapping.The stage curve is the variation of light from the star-planet system throughout a duration of revolution. Considering that the planet rotates on itself throughout its orbit, different areas of its atmosphere are successively visible to us. From this signal, it is possible to map the strength of the light discharged by the planet in longitude. When it comes to hot Jupiters, whose day side is typically hotter, the maximum of light from the world is near the secondary eclipse. Likewise, the minimum of the curve is near the transit, because it is then the night side that is observed.In secondary eclipse mapping, the day side of the exoplanet is resolved. As the world moves in and out from behind its star from our point of view, areas of it are concealed, enabling us to separate the light emitted by a given area of its environment. By measuring the amount of light released by each individual area, it is then possible to map the day side of the atmosphere against longitude and latitude.The arrival of the James Webb Space TelescopeTo date, phase curve analysis has actually been used to numerous planets utilizing area telescopes, including the Hubble, Kepler and TESS area telescopes. Secondary eclipse mapping has only been used to one exoplanet, Hot Jupiter HD189733 b, from observations with the Spitzer space telescope. However, these observations are typically made at a single wavelength and dont supply a total photo of the climatic procedures at work on these exoplanets.With a 6.5-meter mirror, compared to Hubbles 2.4-meter mirror, the Webb telescope will supply unprecedentedly exact observations over a wide variety of wavelengths. 4 instruments, including Canadas NIRISS (Near-infrared Imager and Slitless Spectrograph), will observe in the infrared range and define the atmospheres of a wide variety of exoplanets.With the Webb telescope, it will be possible to apply the mapping approaches available to us to determine the three-dimensional variation of exoplanet atmospheres. These measurements will allow us to deepen our understanding of climatic processes.As technology and instruments continue to advance, it might even be possible to map an Earth-like exoplanet in the future.This post was initially published in French and on The Conversation.Follow us @Spacedotcom, Facebook and Google+.

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