Astronomy Picture of the Day

Explanation: M33 is a prominent nearby spiral galaxy. Nicknamed the Triangulum, M33 is one of the larger members of the Local Group of Galaxies. Two massive spiral galaxies dominate the Local Group: M31 and our Milky Way Galaxy. M33 is the only other spiral galaxy known in the Local Group. At 3000 light-years, M33 is the second closest spiral galaxy. M33 is thought by some to be a satellite galaxy to massive M31. M33 is close enough to appear twice the angular size of the full moon, when viewed with binoculars. Globular clusters in M33's halo appear unusual and might be much younger than globular clusters in our Galaxy's halo.

M33是個很醒目的鄰近螺旋星系。 有 "三角大星系 "稱號的M33，是本星系群較大的成員之一。 在本星系群裡，最具主宰性的天體是M31和我們銀河系這二個螺旋星系，而M33則是其他唯一已知的螺旋星系。 距離約300萬光年的M33，是離我們第二近的螺旋星系。 有人認為M33是龐大的M31的伴星系之一。 當用雙筒望遠鏡觀賞時，因為M33夠近，所以視覺上的張角是滿月的2倍。 M33星系暈裡的球狀星團看來也很不尋常，可能比我們銀河系銀暈裡的球狀星團要年輕得多。