4 Attachment(s)
Object of the Week, May 17, 2015 - M101, NGC 5457, Arp 26
Spiral galaxy – SAB(rs)cd
Ursa Major
RA 14h 03m 12.6s
DEC +54° 20′ 57″
Magnitude: 7.86v
Apparent Size: 28′.8 × 26′.9
Distance: ~21 million light years
Discovered by: Pierre Méchain on March 27, 1781
M101 is not only a beautiful face on galaxy it also has the largest grouping of NGC objects in such a small apparent space - ten. Eleven, if you count M101 itself as NGC 5457. But that’s not the beauty of M101 to me, its real magic is seeing its stretched out grand design spiral arms and tidal tail all in one grand view as shown in this DSS image:
Attachment 1657
But make no mistake, just because M101 is a Messier object doesn't mean it’s bright or easy to see in a suburban sky. You’ll need a truly dark and transparent sky to fully appreciate its overall shape and subtle details.
At first glance, M101 looks to have a fairly round overall shape, which is much different than what we see in its photos. It takes a great sky for its two faint trailing arms and overall asymmetry to become visible. You might also see the tidal tail stretching off the brightest arm, near NGC 5462, on a night like this. There are other knots and dark areas spread throughout M101 other than the ten NGC objects as shown in the chart below that you might see as well.
By the way, each of the NGC objects that belong to M101 are made up of multitudes of separate objects that we see grouped together because of their small apparent size and individual faintness. Only by being bunched near each other do we see them as the knots that embellish the spiral arms of M101. This seems to be generally true of HII regions we see in distant galaxies.
My favorite area in M101 is the pair NGC 5447 and NGC 5450, which are close enough together to often appear as one object. The best nights will show them as two separate and rather large nebulous patches with ragged edges, and they're placed near the end of the two fainter trailing arms of M101. I'm still trying to get a good look at the dark lane near the core, but I suspect that will take a nearly perfect night with my 28 inch.
Attachment 1658 Attachment 1659
My drawing was built up by six hours of sketching at the eyepiece, spread out over several nights and two years, and every second was a joy.
NGC 5471: ~ 74 known HII regions, star clusters, SNR’s, x-ray and UV sources and compact galaxy cluster.
NGC 5462: ~ 117 known HII regions, star clusters, SNR’s, x-ray and UV sources and compact galaxy cluster.
NGC 5461: ~ 50 known HII regions, star clusters, SNR’s, x-ray and IR sources.
NGC 5458: ~ 19 known HII regions, star clusters, SNR’s, x-ray and UV sources.
NGC 5455: ~ 14 known HII regions, star clusters, SNR’s, x-ray, radio and UV sources.
NGC 5453: ~ 25 known HII regions, star clusters, SNR’s and UV sources.
NGC 5451: ~ 27 known HII regions, UV source and galaxies.
NGC 5450: ~ 40 known HII regions, star clusters and x-ray sources.
NGC 5449: ~ 27 known HII regions, compact galaxy cluster and galaxies.
NGC 5447: ~ 21 known HII regions, star clusters and x-ray sources.
Region A: ~ 14 known HII regions, star clusters, x-ray sources and compact galaxy cluster.
Region B: ~ 20 known HII regions, star clusters, SNR, IR and x-ray sources.
Region C: ~ 26 known HII regions and star clusters.
Region D: ~ 8 known HII regions and star clusters.
Region E: ~ 72 known HII regions, star clusters, SNR, and x-ray sources.
Region F: ~ 10 known HII regions, star clusters, x-ray and UV sources.
Region G: ~ 9 known HII regions, star clusters and UV sources.
Region H: ~ 67 known HII regions, star clusters x-ray and UV sources.
Sources: Aladin, Simbad and NED
Attachment 1656
GIVE IT A GO AND LETS US KNOW!
