Chromosphere

A chromosphere ("sphere of color", from the <a href="/facts/Ancient_Greek/LIK7NlUh">Ancient Greek</a> words χρῶμα (khrôma) 'color' and σφαῖρα (sphaîra) '<a href="/facts/Sphere/jywYLNM2">sphere</a>') is the second layer of a <a href="/facts/Stellar_atmosphere/Ll4LjxIn">star's atmosphere</a>, located above the <a href="/facts/Photosphere/32a139LB">photosphere</a> and below the <a href="/facts/Solar_transition_region/fwsuHRhk">solar transition region</a> and <a href="/facts/Stellar_corona/W4WNqV9u">corona</a>. The term usually refers to the <a href="/facts/Sun/CadPCVHh">Sun</a>'s chromosphere, but not exclusively, since it also refers to the corresponding layer of a <a href="/facts/Stellar_atmosphere/Ll4LjxIn">stellar atmosphere</a>. The name was suggested by the English astronomer <a href="/facts/Norman_Lockyer/Uh3no29f">Norman Lockyer</a> after conducting systematic solar observations in order to distinguish the layer from the white-light emitting <a href="/facts/Photosphere/32a139LB">photosphere</a>. 
In the <a href="/facts/Solar_atmosphere/CadPCVHh">Sun's atmosphere</a>, the chromosphere is roughly 3,000 to 5,000 kilometers (1,900 to 3,100 miles) in height, or slightly more than 1% of the Sun's radius at maximum thickness. It possesses a homogeneous layer at the boundary with the photosphere. Narrow jets of <a href="/facts/Plasma_(physics)/1d3btMVU">plasma</a>, called <a href="/facts/Solar_spicule/UERNMzhm">spicules</a>, rise from this homogeneous region and through the chromosphere, extending up to 10,000 km (6,200 mi) into the corona above.
The chromosphere has a characteristic red color due to <a href="/facts/Electromagnetic_emission/Ynx7ujCW">electromagnetic emissions</a> in the <a href="/facts/H-alpha/Akk50rbI">Hα</a> <a href="/facts/Spectral_line/HuI4Bj5f">spectral line</a>. Information about the chromosphere is primarily obtained by analysis of its emitted electromagnetic radiation. The chromosphere is also visible in the light emitted by ionized calcium, Ca II, in the violet part of the solar spectrum at a wavelength of 393.4 nanometers (the <a href="/facts/Calcium_K-line/rVSJ6nlH">Calcium K-line</a>).
Chromospheres have also been observed on <a href="/facts/Star/PFbd6ICx">stars</a> other than the Sun. On large stars, chromospheres sometimes make up a significant proportion of the entire star. For example, the chromosphere of <a href="/facts/Supergiant_star/y7w8WEcm">supergiant star</a> <a href="/facts/Antares/adRhtq7X">Antares</a> has been found to be about 2.5 times larger in thickness than the star's radius.

Chromosphere open-in-new

Chromosphere