Sky & Telescope - June 2020 - 15

features associated with both non-barred and barred spirals.
In addition, the inner arms form a ringlike structure. It's also
one of three Messier galaxies that share the same nickname,
the Pinwheel Galaxy; the other two are M33 and M99.
Work pressures prevented me from much serious observing in 1993, but I saved Clark's article with its accompanying
image and six years later tackled the H II regions that appear
as knots in M101's outer spiral arms. My 8-inch f/6 Newtonian at 116× revealed three of these knots: NGC 5461 (the
easiest of the three), NGC 5462, and NGC 5455. NGC 5461
and NGC 5462 were tiny fuzzies, while NGC 5455 looked
stellar but was only intermittently visible. One night during
a Messier marathon - not an event when you normally want
to linger on objects, since the aim is to bag as many of the
110 Messier objects as quickly as possible in one night - I had
my best view yet of M101 with an 8-inch scope (although Sue
French saw as much with her 105-mm refractor at 127×). At
93× the Dob, with its freshly aluminized mirror, forced me
to spend time on the galaxy because I could detect two barely
discernible spiral arms and a fairly faint nucleus.
Then, in 2004, the June issue (again) featured an excellent article by Steve Gottlieb entitled "H II Regions Galore
in M101." It again took a while before I could follow up on
the article, but on a first-rate night five years later I finally
got around to chasing down more of M101's knots. For this
purpose, I used my backyard observatory's 16-inch f/4.5
Newtonian on an equatorial mount. On the first night, 152×
revealed two prominent spiral arms plus sections of two faint
arms. As I swept around the galaxy, I detected 10 knots and
circled them on an unlabeled image. In the morning, I compared my markings to the H II regions and star associations
identified on the image in Steve's article. To the three NGC
knots that my 8-inch had shown in 1999, my 16-inch added
NGC 5450, NGC 5447, NGC 5471, and NGC 5458.
I don't know whether the three unidentified knots that
I saw in the galaxy were legitimate H II regions and star
associations or not. But there were three knots in Steve's
article that I hadn't seen by simply sweeping the galaxy. So,
the following year I returned to M101 and - again referring
to the image in Steve's article for star-hopping - I added
NGC 5453, NGC 5449, and NGC 5451. All three were mere
smudges and only occasionally detectable when the seeing
steadied. NGC 5451 required 229×, but 152× sufficed for the
other two. Sue French has observed seven of these star-forming regions with her 10-inch reflector - the last three were
just beyond the grasp of a 10-inch.

p SPIRAL SPLENDOR June nights bring this magnificent spiral galaxy
in Ursa Major into prime evening position. But it's not alone. Follow the
author as he explores the spiral arms of M101, and galaxy-hops around
the Pinwheel in search of further interesting targets.
q DISTORTED DWARF A member of the M101 group of galaxies,
NGC 5474 lies around 21 million light-years away and contains several
billion stars (instead of the several hundred billion that the Milky Way
counts as its own). Previous interactions with M101 might have contributed to this dwarf galaxy's odd look.
N

M101: M ASIL IM AGING TE A M;
NGC 5474: ESA / HUBBLE / N ASA

Galaxy-hopping Around the Pinwheel
The Astronomical League's Herschel 400 Observing Program
(https://is.gd/Herschel400) that I completed with my 8-inch
long ago includes three galaxies near M101 (NGC 5473,
NGC 5474, and NGC 5631). And in the course of working
my way around M101 to view the condensations in its spiral
arms I came across several more nearby galaxies. Last year
I decided to star-hop around the area in order to observe
sk yandtelescope.org * JUNE 2 02 0

15


https://www.is.gd/Herschel400 http://www.skyandtelescope.org

Sky & Telescope - June 2020

Table of Contents for the Digital Edition of Sky & Telescope - June 2020

Contents
Sky & Telescope - June 2020 - Cover1
Sky & Telescope - June 2020 - Cover2
Sky & Telescope - June 2020 - 1
Sky & Telescope - June 2020 - Contents
Sky & Telescope - June 2020 - 3
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