M99 is a magnitude +10.2 spiral galaxy situated in the southern part of the constellation of Coma Berenices. It's a beautiful object that's a member of the Virgo cluster of galaxies and appears almost face-on from our perspective. M99 was discovered by Pierre Mechain on March 15, 1781, on the same night he also discovered M98 and M100. The discoveries were then reported to Charles Messier, who measured the positions before adding them to his catalogue on April 13, 1781. This was just prior to the release of the third and final published edition.

The 3rd Earl of Rosse, William Parsons, first identified the spiral structure of M99 in 1846 using his 72-inch (1.83 m) reflecting telescope at Birr Castle in Ireland. The galaxy was one of the first to have its structure identified. At the time, Rosse was using the World's largest optical telescope.

M99 is located 55 Million light-years from Earth. It covers 5.3 x 4.6 arc minutes of apparent sky, which corresponds to a spatial diameter of 85,000 light-years. The galaxy is positioned 7 degrees east of bright star Denebola (β Leo - mag. +2.1) and just less than 1 degree southeast of star 6 Com (mag. +5.1). Tenth magnitude edge-on spiral galaxy M98 lies 0.5 degrees west of 6 Com.

M99 Spiral Galaxy (ESA/NASA/Matej Novak)

Finder Chart for M99 (also shown M49, M53, M58->M60, M64->M66, M84->M91, M98 and M100)

Finder Chart for M99 (also shown M49, M53, M58->M60, M64->M66, M84->M91, M98 and M100) - pdf format

M99 is visible through small telescopes as a faint roundish glow with a brighter core. Of course aperture helps and it's much easier to detect with a medium sized telescope or larger. Through a 200mm (8-inch) scope the galaxy appears as a fuzzy patch of light with a noticeably brighter centre. On dark nights, the outer haze hints at the spiral structure, which is easily seen at high powers through 250mm (10-inch) scopes. Even larger instruments bring out finer details such as dust bands and subtle details on the spiral surface. It's a testament to the quality of today amateur scopes that the spiral structure can be easily seen, compared to the enormous sized instrument required by Lord Rosse for the same task.

While not classified as a starburst galaxy, there is a high activity of star formation occurring in M99. To date, four supernovae have been recorded in the galaxy. They are SN 1967H (mag. +14), SN 1972Q (mag +15.6), SN 1986I (mag +14) and SN 2014L (mag +15.4).

M99 and the other Virgo cluster galaxies are best seen during the months of March, April and May.

M99 Data Table

Object TypeSpiral galaxy
ConstellationComa Berenices
Distance (kly)55000
Apparent Mag.10.2
RA (J2000)12h 18m 50s
DEC (J2000)14d 25m 01s
Apparent Size (arc mins)5.3 x 4.6
Radius (light-years)42,500
Number of Stars150 Billion
Notable FeatureThree Supernovae have been observed in this galaxy.

Sky Highlights - April 2017

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