NIRCam in the context of "Wolf–Rayet star"


Wolf-Rayet stars exhibit spectra characterized by broad emission lines of ionized helium, nitrogen, or carbon, indicating a significant enrichment of heavy elements at their surfaces and a depletion of hydrogen. These stars possess extremely high surface temperatures, ranging from 20,000 K to 210,000 K, and are often observed with strong stellar winds. The Near-Infrared Camera (NIRCam) is particularly useful in observing these stars because their intense emission lines are prominent in infrared wavelengths, allowing for detailed analysis of their composition and atmospheric properties.

⭐ In the context of Wolf-Rayet stars, NIRCam is considered most valuable for studying which characteristic of these stars?

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⭐ Core Definition: NIRCam

NIRCam (Near-InfraRed Camera) is an instrument aboard the James Webb Space Telescope. It has two major tasks, as an imager from 0.6 to 5 μm wavelength, and as a wavefront sensor to keep the 18-section mirrors functioning as one. In other words, it is a camera and is also used to provide information to align the 18 segments of the primary mirror. It is an infrared camera with ten mercury-cadmium-telluride (HgCdTe) detector arrays, and each array has an array of 2048×2048 pixels. The camera has a field of view of 2.2×2.2 arcminutes with an angular resolution of 0.07 arcseconds at 2 μm. NIRCam is also equipped with coronagraphs, which helps to collect data on exoplanets near stars. It helps with imaging anything next to a much brighter object, because the coronagraph blocks that light.

NIRCam is housed in the Integrated Science Instrument Module (ISIM). It is connected to the ISIM mechanically with a system of kinematic mounts in the structural form of struts. There are thermal straps connecting the NIRCam optical bench assembly to theISIM structure and to thermal radiators. It is designed to operate between 32 K (−241.2 °C; −402.1 °F) and 37 K (−236.2 °C; −393.1 °F). The Focal Plane Electronics operate at 290 K.

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HINT: Wolf-Rayet stars are distinguished by their spectra containing prominent emission lines of ionized helium, nitrogen, or carbon, and NIRCam's capabilities in the infrared spectrum allow for detailed observation and analysis of these lines, revealing information about the stars' composition and atmospheric conditions.

👉 NIRCam 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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