M25

open star cluster · in Sagittarius

2,103 light-years from Earth

A bright cluster you can see without a telescope from a dark site. One of its stars, U Sagittarii, is a Cepheid: it swells and shrinks, brightening and fading every 6.7 days, and helps set the scale of distances in space.

• 2,100 light-years (Gaia) · its stars spread over about 50 light-years
• about 100 million years old · 565 of its stars as Gaia measured them

kind

nebula · star cluster

catalogue

M25 · IC 4725

size

52 light-years across