J band (infrared)

In infrared astronomy, the J band refers to an atmospheric transmission window (1.1 to 1.4 μm) centred on 1.25 micrometres (in the near-infrared).

Betelgeuse is the brightest near-IR source in the sky with a J band magnitude of −2.99.

The J band is a frequent source of ground based observations since the wavelengths it covers pass through clouds and other atmospheric gasses.

[4] It can be used to scrutinize the photosphere of giant and supergiant stars while mostly avoiding opacities from molecular bands and also has access to the 1080 nm He I line which is useful in the study of circumstellar disk interactions around T-Tauri stars.

[5] J, H and K-band spectroscopy is also commonly used to observe and research brown dwarfs[6] and directly imaged exoplanets.

Atmospheric windows in the infrared. The J band is the transmission window (1.1 to 1.4 μm) centred on 1.25 micrometres. (The gap between the J band and lower bands is too small to be visible at this scale; as a result they blend together and appear to comprise a single, contigous band.)