Messier 105: Elliptical Galaxy in Leo

M105 is a round elliptical galaxy in the body of Leo, the brightest of a small cluster of galaxies that also includes the spirals M95 and M96.

What it is

Elliptical galaxies are smooth, rounded collections of mostly old stars with very little gas or new star formation, and M105 is a textbook example. It lies about 32 million light-years away. Its bright inner 2′ spans roughly 19,000 light-years. Hubble observations show that its core hosts a supermassive black hole. M105 belongs to the Leo I group of galaxies, along with M95, M96 and several fainter NGC galaxies; a vast ring of hydrogen gas, detected by radio telescopes, loops around M105 and its neighbor NGC 3384.

When to see it

M105 is a spring object, highest around midnight in early March and well placed in the evening from March through May. From about 40°N it climbs to roughly 63° in the south. It lies north of the celestial equator but not far, so it is also visible from the Southern Hemisphere, low in the north; from 35°S it reaches about 42°.

How to find it

Find Regulus, the bright star at the base of Leo's backward question mark, and Chertan (Theta Leonis), the star at the southwest corner of the triangle that marks Leo's hindquarters, about 16° to the east-northeast. The M95–M96–M105 group sits a little past the halfway point between them, closer to Chertan: M105 is about 9.7° east of Regulus and 7° west-southwest of Chertan. M96 is just under 1° south-southwest of M105.

What you will see

In binoculars from a dark site, M105 shows as a faint, starlike fuzzy spot near M95 and M96; from suburban skies it is difficult. A 70–100 mm telescope shows a small, round glow that brightens steadily toward the center. In the same field, a few arcminutes to the northeast, the lenticular galaxy NGC 3384 appears as a smaller, slightly elongated glow. A 200 mm or larger telescope shows M105's bright, almost stellar nucleus and makes NGC 3384 easy, with the fainter spiral NGC 3389 nearby as a third, dimmer smudge. Filters do not help.

History

Pierre Méchain discovered M105 on March 24, 1781, a few days after he found M95 and M96, but it did not make it into Messier's published catalog. In 1947 the Canadian astronomer Helen Sawyer Hogg drew attention to a 1783 letter in which Méchain described the object, and she proposed adding it to the list as M105. Together with M108, M109 and M110, these late additions from Messier's and Méchain's notes brought the list to its modern 110 entries.