Concept illustration of a grism image

This image represents the data that comes from using the NASA/ESA Hubble Space Telescop's highly-sensitive Wide Field Camera 3 in its grism spectroscopy mode.

A grism is a combination of a grating and a prism, and it splits up the light from a galaxy into its constituent colours, producing a spectrum. In this image the continuum of each galaxy is shown as a "rainbow".

Astronomers can look at a galaxy’s spectrum and identify light emitted by the hydrogen gas in the galaxy. If there are stars being formed in the galaxy then the intense radiation from the newborn stars heats up the hydrogen gas and makes it glow.

All of the light from the hydrogen gas is emitted in a small number of very narrow and bright emission lines. For dwarf galaxies in the early Universe the emission lines are much easier to detect than the faint, almost invisible, continuum. 

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About the Image

Id:heic1412c
Type:Photographic
Release date:19 June 2014, 14:00
Related releases:heic1412
Size:1201 x 1022 px

About the Object

Name:Illustration, WFC3
Type:• Early Universe : Galaxy
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