Sky & Telescope - October 2021 - 59

including what passes for a core, in my
scope at 570×, each showing a different
brightness and shape. Two field stars
(magnitudes 15 and 18) flank the main
agglomeration of knots.
Chasing the whole collection of
Arp 133 and 308
(10′, 570×)
ARP 133 The elliptical
NGC 541 has a curious clustering
of galaxies to its upper left,
seemingly just beyond its halo.
While the outermost two are
likely line-of-sight coincidences,
the middle of the trio is called
Minkowski's Object. It's a young
galaxy, and researchers believe
that the observed star formation
was triggered by a radio jet
emanating from NGC 541.
ably well-defined. At magnifications
exceeding 500×, a wide gap separates
this pair of " dust motes " from NGC
541, and a 17th-magnitude star is situated
a bit farther to the northeast.
A Duo of Pairs
Staying in Cetus, just 4.3′ northeast of
NGC 541, we come to the close pair of
Arp 308 (NGC 545/547). They're listed
in the Atlas as an example of a double
galaxy. NGC 545, an unbarred lenticular
galaxy, appears to cradle NGC 547, a
nearly spherical elliptical. At first, I took
the " cradling " to be another eye-brain
response, but deep survey images show
this effect as well. William Herschel
discovered the duo in October 1785,
and they're easy to see in a modern
amateur telescope.
Arp 230 (IC 51) is a near-twin of
NGC 545/547: a semicircular form
embracing a nebulous knot. In reality,
however, this object is a single, isolated
galaxy in which we are observing a ring
of star formation oriented almost edgeon
with the galaxy's nucleus peeking
over the rim. Images (such as the one at
right) show an extensive halo terminating
in a series of segments. This galaxy
is located a little more than 4½° north
of Beta (β) Ceti and is listed in the Atlas
as a representative of the group with the
peculiarity of " concentric rings. " The
outer rings remained invisible in my
telescope, although at high magnification
the central structure is quite robust.
Finishing in the Fish
Returning to Pisces - the easternmost
part of the constellation, about halfway
between Alpha (α) and Xi (ξ) Piscium -
we find the strongly interacting galaxy
pair Arp 126 (UGC 1449). Using my
scope at very high magnification from a
dark, elevated location reveals a wealth
of fine detail, making it a fitting object
with which to conclude our survey. The
compact western component, PGC 7415,
exhibits a broken ring of star-forming
regions around its nucleus, but this
feature is far too small to be seen visually.
The larger, low surface brightness
eastern component (Mrk 582)
consists of little more than
scattered knots of star
formation. I could see
four of these knots,
ARP 230 A longago
collision with
another galaxy likely
gave Arp 230 its irregular
shape. Its outer ring
- the site of ongoing star
formation - rotates over
the poles of the galaxy.
sk yand tele scope .o r g * OCTOBER 2021 59
targets listed in the Atlas of Peculiar
Galaxies is a wonderfully engrossing
way to pass time under the stars.
You're sure to come across some of the
stranger sights in the universe, ranging
from odd, little-known features in some
of the brighter galaxies to truly elusive
targets. Don't let the challenges that
mark many of the objects listed in the
Atlas deter you - dare, instead, to set
out with your telescope to explore the
realm of peculiar galaxies.
¢ IVAN MALY is a biologist living in upstate
New York. His observations can be
found at www.deepskyblog.net.
FURTHER MATERIAL For an online version
of Arp's Atlas of Peculiar Galaxies,
go to https://is.gd/ArpCat. Finder charts
and images for the targets discussed here
are at https://is.gd/ArpCharts.
Arp 230
(10′, 360× and 570×)
ARP 133: SOLOMON / CC BY 2.0; SKETCHES: IVAN MALY (2); ARP 230:
ESA / HUBBLE / NASA / ACKNOWLEDGEMENT: FLICKR USER DET58
http://www.deepskyblog.net https://www.is.gd/ArpCat https://www.is.gd/ArpCharts http://skyandtelescope.org
Sky & Telescope - October 2021

Table of Contents for the Digital Edition of Sky & Telescope - October 2021
