Sky and Telescope - March 2018 - 32

Starburst Galaxies

occurring in May 2017 (SN 2017 eaw)
discovered in NGC 4449's halo. SSCs
and discovered by amateur astronomer
and numerous H II regions are scattered
Patrick Wiggins. Just for that reason
along the length of the disk. At 10th
alone, this galaxy is worth constant
magnitude and measuring 6′ × 4′, NGC
monitoring. Overall, NGC 6946 has
4449 is an easy object to observe and
fairly low surface brightness, but the
image with relatively small telescopes.
delicate spiral arms and H II regions
A good 8- to 10-inch scope will reveal
are readily visible with larger scopes. In
several bright condensations along the
contrast, NGC 253, the "Silver Dollar
central axis, while larger instruments
Galaxy," is a large dusty spiral inclined
will make the galaxy "come alive" with
60° to our line of sight. It collided with
numerous knots and dark rifts. Several
a dwarf system around 200 million years
SSCs are also in the range of 16-inch or
p SUPER STAR CLUSTERS Howard Banich
larger scopes, including a 15th-magniago, leading to the extensive starburst
captured some of the stellar clusters in NGC
tude cluster in the core of the galaxy.
activity in the core region. The HST
6946, the Fireworks Galaxy, in his sketch.
From NGC 4449, scan some 5° to the
identiﬁed several large SSCs, the largsoutheast to M94, a beautiful face-on
est having a mass of 1.4 million solar
masses and an absolute magnitude of -15, which is much
galaxy. Few realize it's also a special type of starburst galaxy:
brighter than that of a typical globular cluster. These objects,
Instead of the starburst being either galaxy-wide or concenhowever, are heavily obscured by the dust in the nuclear
trated in the core, most of the star-forming activity is located
region and are best seen at infrared wavelengths. Neverthein a ring about 70″ in diameter. Some sources refer to this
less, it's a fascinating area to explore with a larger scope at
structure as a starburst ring. As the inner region of M94 is
higher magniﬁcations.
quite bright, don't hesitate using high power to examine this
Wrapping up this part of the survey is the tiny dwarf irregstructure more closely.
ular IC 10 in Cassiopeia. IC 10 has the distinction of being
Other bright starburst galaxies of amateur interest are
NGC 6946 in Cygnus and NGC 253 in Sculptor. The face-on the closest known starburst galaxy at slightly more than 2
million light-years, and the only member of the Local Group
spiral NGC 6946 is also known as the "Fireworks Galaxy,"
currently undergoing starburst activity. Located 1.5° due east
as it's been home to no fewer than 10 supernovae, the latest

p THE SILVER DOLLAR GALAXY A collision with a dwarf galaxy some 200 million years ago triggered starburst activity in the core of NGC 253.
Several large SSCs lurk in this galaxy, but they're rather heavily obscured and best seen in the infrared. Nevertheless, this 7th-magnitude target is
an interesting one to explore, as both Richard Jakiel and Howard Banich did. The image on the left was taken by Richard using a 127-mm f/7 APO
refractor, while the sketch on the right shows what Howard saw through his 28-inch telescope.

M A RCH 2 018 * SK Y & TELESCOPE

Sky and Telescope - March 2018

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