What does this number measure?
A vast cloud of energetic particles surrounds this cluster. The extent of the radio-detected halo, not the cluster's gravitational diameter or the size of a single galaxy. The Chandra release reports a halo almost 20 million light-years across. Its extent depends on sensitivity and the definition of diffuse emission; this halo is not a solid material shell.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
The Chandra press release reports a halo spanning almost 20 million light-years. Its extent depends on sensitivity and on the definition of the diffuse emission; this halo is not a solid physical shell.
A generic artistic pattern shared with another entry in the same family; it represents neither a photograph nor an observed map of this structure. The galaxies and filaments are symbolic; only the stated extent follows the length scale factor. The galaxy pattern is not a real radio image and does not describe the halo's measured shape.