Messier 99, also known as the Coma Pinwheel or Virgo Cluster Pinwheel, is an unbarred spiral galaxy in Coma Berenices. It is one of the brighter spiral galaxies in the Virgo Cluster and appears almost face-on, which makes it a popular target for both professional and amateur astronomers.

Messier 99 is a grand design spiral, completely unbarred and with two giant spiral arms, with one of the spiral arms is normal and the other appears distorted. M99 is slightly asymmetric in shape, with the nucleus shifted from the galaxy’s center, likely as a result of interactions with other galaxies in the Virgo Cluster. M99 rotates clockwise and is classified as an Sc type spiral galaxy.

	Description
Visible From Pacific Northwest	December To May
Best Time To Observe	May
Minimum Size Of Viewing Device	Small/Medium Telescope
Object Type	Spiral Galaxy
Designations	Messier 99, M99, NGC 4254, Coma Pinwheel, Virgo Cluster Pinwheel, PGC 39578, ALFALFA 1-248, UGC 7345, VCC 307, Z 98-144, Z 99-11, Z 1216.3+1442, 2E 2650, 2E 1216.3+1441, GB6 B1216+1442, IRAS 12162+1441, 2MASX J12184962+1424593, MCG+03-31-099, MRC 1216+146, NVSS J121850+142450, NVSS B121617+144129, SDSS J121849.60+142459.4, 1RXS J121853.8+142602, UZC J121849.6+142501, HIPASS J1218+14
Right Ascension	12h 18m 49.6s
Declination	+14°24’59”
Constellation	Coma Berenices
Number Of Stars	150 billion
Apparent magnitude	+10.4
Apparent dimensions	5′.4 x 4′.7
Object Radius	42,500 light years
Distance From Earth	55.7 million light years

History

The Virgo Cluster Pinwheel was discovered by the French astronomer Pierre Méchain on March 17, 1781, along with the galaxies Messier 98 and Messier 100. Méchain reported the discovery to his friend Charles Messier, who determined the positions for the three objects and added them to the Messier Catalogue on April 13, 1781, just before completing the third and final edition. Messier noted:

John Herschel catalogued M99 as h 1173 and later included it in his General Catalogue as GC 2838. He described the object as “very remarkable; bright; large; round; gradually brighter toward the middle; mottled.”

Messier 99 was one of the first spiral galaxies in which a spiral pattern was recognized. The spiral pattern was first observed by William Parsons, 3rd Earl of Rosse, in the spring of 1846.

M99 was the second object Lord Rosse recognized as a spiral, after the Whirlpool Galaxy, M51, which he had discovered about a year before M99.

Locating M99 In The Sky

Messier 99 can be found 7 degrees east of the bright star Denebola in Leo or just under a degree southeast of the magnitude 5.1 star 6 Comae Berenices, which lies 0.5 degrees east of the edge-on spiral galaxy Messier 98. The best time of year to observe M99 and other galaxies in the Virgo Cluster is during the spring.

Viewing M99

The galaxy can be seen in small telescopes, but only appears as a dim ball of light with a brighter centre. 8-inch telescopes reveal a hazy patch of light with a more clearly defined centre. 10-inch telescopes begin to hint at the spiral structure under good conditions, and larger instruments reveal the galaxy’s dust bands and other details.

Photographing M99

Due to the concentration of matter in the line of sight between Earth and he Coma. So the only real chance to photograph the spiral structure in any detail, other than looking at someone else’s images, is to have access to a large aperture telescope, a CCD camera, or both. It is indeed possible to utilize a DSLR, but one would have to potentially pump up the ISO, as there will need to be a plethora of time taken to gather data. There might need to be several nights of gathering data. Accurate auto guiding will be required to image this galaxy. There are some forum posts that are linked below to provide some guidance for specific setups.

Sources And Further Reading

Descriptions of all of Messier Objects can be found here.

https://www.nasa.gov/feature/goddard/2017/messier-99

https://freestarcharts.com/messier-99

https://www.cloudynights.com/topic/579711-m99-or-coma-pinwheel-galaxy-from-red-zone/

https://www.cloudynights.com/topic/695222-messier-99-st-katherines-wheel/