The Pleiades (M45, the Seven Sisters) is an open star cluster located at a distance of about 444 light-years from the Earth.
It is the nearest Messier object to our planet and one of the most prominent deep-sky objects (magnitude 1.6). To the unaided-eyed observer, it usually appears as a smaller copy of the Big Dipper surrounded by a cloud of dust, a blueish 6 to 8 stars pattern.