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Bode’s Galaxy · M81: size, dimension and comparison

The adopted reference is about 90,000 light-years.

representative luminous diameter ≈ 90 000 ly

A light-year is a distance: how far light travels in one year. It is used for distances between stars.

A regular spiral with a bright central bulge.

Explore at this scale
Bode’s Galaxy · M81, interpreted illustration
Interpreted illustration · dimension stated in the fact sheet.

What does this number measure?

The Messier Objects catalogue relates the angular diameter of 26.9 arcminutes to a diameter of about 90 000 ly. The value is a convention for the luminous extent, not a sharp material boundary.

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.

Compare with Milky Way in the explorer →

Source and limitations

Rounded documentary extent. Boundaries are diffuse and depend on the observations and convention used; this is not a distance from Earth.

Original schematic illustration, not a photograph. Shapes, colours and details are interpreted; only the stated dimension is compared.

Illustration sources

How Big — generated illustration; NASA/ESA documentation.

Source coverage: Visual interpretation; colours and texture do not constitute an observation. Only the designated extent follows the catalogue's reference value.