Mid-Infrared Instrument in the context of "Wolf–Rayet star"

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⭐ Core Definition: Mid-Infrared Instrument

MIRI, or the Mid-Infrared Instrument, is an instrument on the James Webb Space Telescope. MIRI is a camera and a spectrograph that observes mid to long infrared radiation from 5 to 28 microns. It also has coronagraphs, especially for observing exoplanets. Whereas most of the other instruments on Webb can see from the start of near infrared, or even as short as orange visible light, MIRI can see longer wavelength light.

MIRI uses silicon arrays doped with arsenic to make observations at these wavelengths. The imager is designed for wide views but the spectrograph has a smaller view. Because it views the longer wavelengths it needs to be cooler than the other instruments (see Infrared astronomy), and it has an additional cooling system. The cooling system for MIRI includes a pulse tube precooler and a Joule-Thomson loop heat exchanger. This allowed MIRI to be cooled down to a temperature of 7 kelvins during operations in space.

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👉 Mid-Infrared Instrument in the context of Wolf–Rayet star

Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. The surface temperatures of known Wolf–Rayet stars range from 20,000 K to around 210,000 K, hotter than almost all other kinds of stars. They were previously called W-type stars referring to their spectral classification.

Classic (or population I) Wolf–Rayet stars are evolved, massive stars that have completely lost their outer hydrogen and are fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; they are young extremely massive stars still fusing hydrogen at the core, with helium and nitrogen exposed at the surface by strong mixing and radiation-driven mass loss. A separate group of stars with WR spectra are the central stars of planetary nebulae (CSPNe), post-asymptotic giant branch stars that were similar to the Sun while on the main sequence, but have now ceased fusion and shed their atmospheres to reveal a bare carbon-oxygen core.

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Mid-Infrared Instrument in the context of Fomalhaut b

Fomalhaut b, formally named Dagon (/ˈdeɪɡən/), is an expanding dust cloud and former candidate planet observed near the A-type main-sequence star Fomalhaut, approximately 25 light-years away in the constellation of Piscis Austrinus. The object's discovery was initially announced in 2008 and confirmed in 2012 via images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. Under the working hypothesis that the object was a planet, it was reported in January 2013 that it had a highly elliptical orbit with a period of 1,700 Earth years. The object was one of those selected by the International Astronomical Union as part of NameExoWorlds, their public process for giving proper names to exoplanets. The process involved public nomination and voting for the new name. In December 2015, the IAU announced the winning name was Dagon.

The planetary hypothesis has since fallen out of favor; more gathered data suggested a dust or debris cloud is far more likely, and the object was placed on an escape trajectory. In 2023, a team of researchers used the James Webb Space Telescope's MIRI to probe the complex dust environment around the Fomalhaut. They discovered a new intermediate dust belt that might be shepherded by an unseen planet and suggested that the blob, Fomalhaut b, could have originated in this belt. The recent research of the Fomalhaut system used the JWST's NIRCam equipped with coronagraphs to probe the complex dust ring in different wavelengths of infrared light. The absence of detection in certain wavelengths support the idea that Fomalhaut b is not a massive planet but rather a dust cloud resulting from a collision among planetesimals.

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← Wolf–Rayet star ← Fomalhaut b
LINKS TO (CHILDREN)
Goddard Space Flight Center → James Webb Space Telescope → Spectrograph → Mid infrared → Micron → Coronagraph → Exoplanet → Infrared → Visible light → Silicon → Arsenic → Infrared astronomy → Pulse tube refrigerator → Joule–Thomson effect → Heat exchanger → Kelvin →