Quantcast
M 64 - Blackeye Galaxy Sleeping Beauty Galaxy
47 of 111

M 64 - Blackeye Galaxy, Sleeping Beauty Galaxy

February 18, 2005
Spiral Galaxy M64 (NGC 4826), type Sb, in Coma Berenices

Right Ascension: 12 : 56.7 (h:m)
Declination: +21 : 41 (deg:m)
Distance: 19000 (kly)
Visual Brightness: 8.5 (mag)
Apparent Dimension: 9.3x5.4 (arc min)

Discovered 1779 by Edward Pigott.

M64 is the famous Black Eye galaxy, sometimes also called the "Sleeping Beauty galaxy". The conspicuous dark structure is a prominent dust feature obscuring the stars behind. This feature also enables one to determine, or at least estimate, which of the galaxy's sides is nearer and which more remote; in case of M64, it seems that the southern side is nearer to us.

J.D. Wray, in his Color Atlas of Galaxies, points out that M64 may be taken as prototype for a class of galaxies called "ESWAG", for Evolved Second Wave (star forming) Activity Galaxy. As becomes evident in color photos, the main spiral pattern is consisted of an intermediate aged stellar population. Stellar formation has first evolved outside following the density gradient, forming stars as long as there was sufficient interstellar matter available, and then dying out slowly. As the matter was flowing back from the evolved stars, by stellar wind, supernovae, and planetary nebula activity, more and more interstellar matter could accumulate again, so that finally there was enough matter to start the formation of new young stars again. This second wave of star formation has apparently reached now the region where the dark dust lane appears.

The dust feature is well visible even in smaller telescopes. M64 was recently shown to have two counterrotating systems of stars and gas in its disk: The inner part of about 3,000 light years radius is rubbing along the inner edge of the outer disk, which rotates opposite and extends up to at least 40,000 light years, at about 300 km/sec. This rubbing process is probably the reason for the observed vigorous star formation process, which is currently under way, and can be observed as the blue knots imbedded in the peculiar dust lane on one side of the nucleus. It is speculated that this peculiar disk and dust lane may be caused by material from a former companion which has been accreted but has yet to settle into the mean orbital plane of the disk.

M64 was discovered by Edward Pigott on March 23, 1779, just 12 days before Johann Elert Bode found it independently on April 4, 1779. Roughly a year later, Charles Messier independently rediscovered it on March 1, 1780 and cataloged it as M64. However, Pigott's discovery got published only when read before the Royal Society in London on January 11, 1781, while Bode's was published during 1779 and Messier's in late summer, 1780. Pigott's discovery was more or less ignored and recovered only by Bryn Jones in April 2002!

The dark dust feature was discovered by William Herschel who observed M64 twice in 1785 and 1789, and already compared it to a "Black Eye."

M64 was identified rather early as a radio source also, which was cataloged as PKS 1254+21. While Sandage has classified it simply as an Sb spiral, in De Vaucouleurs it is of type (R)SA(rs)ab. Its nucleus is somewhat active, and shows rather weak emission lines of Seyfert 2 type.

The distance of this galaxy seems to be not very well determined. Kenneth Glyn Jones and Mallas/Kreimer give about 12, Tully's Nearby Galaxies Catalog 14 million light years, while Burnham has "20-25" million, and quotes Holmberg with 44 million light years (oddly, this latest value also occurs in Kenneth Glyn Jones' Introduction, p. 7 in the second edition). The Night Sky Observer's Guide by Kepple and Sanner gives a distance of 24 million light years. The radial velocity of 377 km/sec in recession would yield about 16 million light years (H0=75), but this is certainly very inacurate, as the direction to this galaxy is close to the Virgo cluster, so that a considerable deviation from the Hubble law must be taken into account. A new press release from the Space Telescope Science Institute (STScI PRC 99-10) gives the distance of M64 as 19 million light years, a value we adopt here for now.

That the distance is not yet better known is a bit strange, as Cepheid variables in this galaxy should be in the reach of current telescopes, perhaps even the largest Earth-bound ones.

Adopting this distance, the apparent extension of M64 of 9.3 arc minutes corresponds to a linear diameter of about 51,000 light years, and its visual magnitude of 8.5 to an absolute magnitude of -20.3 (uncorrected for absorption which is low at the galaxy's high galactic latitude).

M64 forms a small group with the small irregular UGC 8024 (also known as NGC 4789 A or DDO 154). De Vaucouleurs (1975) has included these two galaxies, together with M94 and a number of fainter galaxies, as a member of a nearby group or cloud of galaxies, the Canes Venatici I (CVn I) Cloud or M94 group. This group and the membership of M64 is also noted in Schmidt and Boller (1992), but not in R. Brent Tully's Nearby Galaxies Catalog who lists M64 in an own small group, labelled group 14+3+3, only with UGC 8024.

No supernovae have been recorded in this galaxy up to now.

M64 can be glimpsed with good binoculars, and is a rewarding object for small and medium-sized amateur telescopes. Visually, it exhibits an irregular shape with very uneven brightness and texture, overall a bright oval oriented about ESE-WNW, with a bright large core. The characteristic feature of the Blackeye Galaxy M64, the dark dust pattern, situated to the SSW direction from the nucleus, can be glimpsed with telescopes starting from 4 inch aperture, and get definitely resolved in 6-inch scopes. John Mallas even glimpsed the Black Eye feature in a 2.4-inch and found it easy in 4-inch, but more difficult in an 8-inch.

For locating M64, several methods have been proposed to find the 5th-mag binary star 35 Comae Berenices (ADS 8695, Struve 1687; A: 5.1 m, spec K0; B: 7.2m, F6; separation 1", position angle 182 deg for epoch 2000). One is to look at about 1/3 the distance on the line from Alpha to Gamma Comae; 35 is roughly 3 deg North and 3 deg West from Alpha. Another way is to find the rectangular triangle formed by 35 with 39 and 40 Comae, which are roughly 1 deg West of and forming a short line parallel to the line from Alpha to Beta Comae, which is roughly North-to-South; 35 is almost exactly West, by about 3 degrees, of 39. Eventually, one can look for the southernmost 5th-mag stars of the Comae Berenices Star Cluster, Mel 111, 20, 23, and 26 Comae, which form a conspicuous about equilateral triangle with one side (20-26) oriented E-W. Prolong this side about 3 deg East from the easternmost 26 to find 35. How ever you find 35 Comae, M64 is about 3/4 deg ENE.


comments powered by Disqus