By Brian Cuthbertson
Ursa Major, Canes Venatici, Leo, Virgo: let’s admit it, April is basically galaxy time. If you like galaxies, you’re in. There are of course always interlopers to provide a little variety, represented this time by globular cluster M53. Otherwise, take some time to drift through the extragalactic universe this month; the summer Milky Way will be here before you know it. Enjoy.
M53 & friends rating EASY
Globular cluster in Coma Berenices
RA 13h 12.9m Dec +18d 10.1′ (2000)
Magnitude 8.0 dia 12′
Like its close neighbor NGC 5053 and M3 to the NE in Canes Venatici, M53 is an extreme western outlier of the central Milky Way globular swarm, giving us a taste of things to come later in the summer. In the meantime, these globulars drift in front of the much more distant Virgo cluster, which provides an interesting distance contrast between our local galactic backyard and the great metropolis of galaxies far beyond.
M53 is an easy find, just 1 degree NE of 5th-magnitude Alpha CrB. Alpha is interesting itself – a nearly edge-on visual binary about 65 light years away whose components are both magnitude 5.1. The two stars appear to move back and forth in virtually a straight line, with a 25.85-year period. Their angular separation ranges from essentially 0 to a maximum of about 0.9″. However the system’s 0.1-degree orbital inclination from edge-on prevents actual eclipses from occurring.
M53 is a rich globular found in February of 1775 by J.E. Bode; Messier’s independent discovery followed 2 years later in February of 1777. William Herschel considered M53 one of the most beautiful sights in the heavens in his great reflector, as did Smyth later. M53 is visible in smaller scopes, but a 6-inch is needed to begin resolving it. The globular lies about 65,000 light years away, about 1000 times the distance of Alpha CrB. But take heart: M53 is approaching us at 70 miles per second, so wait long enough and perhaps you can easily observe its 50-odd variable stars in a few million years.
A degree SE of M53 is a fainter neighboring globular cluster, 10th-magnitude NGC 5053. NGC 5053 is a very loose peculiar globular system found by William Herschel in 1784, and it requires an 8-inch scope to be easily seen. It contains about 3400 stars down to 21st magnitude – very sparse for a globular. Its distance of 55,000 light years puts it a bit closer to us than M53.
Finally, half a degree SSW of M53 and half a degree due E of Alpha CrB (more or less between the two) is 7th-magnitude solar twin star HD 114762, which is about 140 light years away – twice the distance of Alpha. In the late 1980s, HD 114762 was found to have an invisible companion in an 84-day orbit similar to that of Mercury around the Sun. The companion’s mass is thought be greater than 9 Jupiters, making it most likely a brown dwarf.
NGC 4559 rating MEDIUM
Spiral galaxy in Coma Berenices
RA 12h 36.0m Dec +27d 57.5′ (2000)
Magnitude 9.8
NGC 4559 is a relatively nearby spiral galaxy in Coma Berenices, just NE of the Coma star cluster. If NGC 4559 were face-on, it would probably resemble open spiral galaxy M33 in the Local Group. However, we see NGC 4559 at a lower angle, perhaps 45-60 degrees off of face-on.
Also known as Caldwell 36, the galaxy is notable even in a 6-inch scope, which features two nearby stars to the east and south. In a 12-inch class scope the galaxy is about 9×2′ with an irregular core.
For you supernova hunters, NGC 4559 is a known producer: a type II supernova went off in 1941 (SN 1941a) with an estimated apparent magnitude of 13. Based partly on this, the galaxy’s distance is estimated to be in the range of 20-30 million light years. And like many nearby spirals, NGC displays bright star-forming regions and dust lanes in its arms. Of these, several actually have IC numbers, but don’t expect to go looking for these with amateur scopes: IC 3550, 51, 52, 55 and 63 are all HII regions and/or star clouds. Two others, IC 3554 and 64, are actually stars superimposed on the galaxy. Deep images also show a number of background galaxies and galaxy groups in and around the system.
NGC 4244 rating HARD
edge-on galaxy in Canes Venatici
RA 12h 17.5m Dec +37d 48.3′ (2000)
Magnitude 10.5
Look for this edge-on spindle in eastern Canes Venatici, about 8.7 degrees or 38 RA minutes west of 3rd magnitude Alpha Cvn (Cor Caroli).
NGC 4244 is a member of the M94 galaxy group, also known as the Canes Venetici I Group. The group is relatively close to the Local Group containing the Milky Way. The galaxy itself sits about 4.3 Megaparsecs or 14 million light-years, from us. Its nearness explains why it is so bright (10.4) and large (15.9×1.8′) despite its small mass of 10 billion Suns, only one-tenth the mass of a typical member of its Sc galaxy type.
In a 6-inch scope, the galaxy presents a 10×1’spindle with a slightly brighter core. The galaxy grows to about 15×1′ if you have a 10-inch, and just a bit fatter, 15×1.5′ if you use a 12-inch scope.
For those of you fond of nicknames and aliases, NGC 4244 is also known as the “Silver Needle Galaxy” and Caldwell 26.
