Sky & Telescope - January 2021 - 22

OBSERVING LOG

by Ted Forte

Winter's
Galaxy
Groups

NGC 1440

Head off the
beaten path
to expand
your January
observing list.

o northern observers, the January sky with its iconic
constellations might be the most familiar of celestial
landscapes. Darkness falls early allowing most of us
to enjoy hours of observing without missing too much (or
any!) sleep. The winter evening sky is dotted with bright
stars - the largest collection of ﬁrst-magnitude stars we ﬁnd
anywhere in the heavens. Cold, crisp air makes them glitter
like diamonds, encouraging us to step out and look up. Scattered among the familiar constellations are some of the most
treasured objects visible in a backyard telescope. Amateur
astronomers know them well and love them dearly.
You probably don't think of galaxies when you consider
observing targets for January nights, but hidden among the
nebulae and star clusters of the winter constellations are
a number of galaxy groups worthy of attention. The dozen
groups I've selected for this tour all consist of four or more
galaxies that lie within 1° or so of the group's brightest
member, and all contain objects that are within the reach
of an 8-inch telescope under a dark sky. The groups' fainter
members will challenge you, providing a test of your optics,
your skills, and your determination. These galaxies are quite
distant, averaging about 230 million light-years, and the farthest we'll visit is nearly 430 million light-years away.
γ

ν
TAURUS
1587

DSS IM AG ES: POSS-II / STSCI / CA LTECH / PA LO M A R OBSERVATORY;
BACKG ROUND TE X T URES: ONE A ND ONLY / SHU T TERSTOCK .CO M;
G A L A X Y SK E TCHES: MELOK / SHU T TERSTOCK.COM

ORION

1684

M42
Rigel

0°

ν
ο1

1600

ο2

LEPUS
α

γ
6h

ERIDANUS

1407

ε
5h

τ9

Star magnitudes
0 1 2 3 4 5 4h

JANUARY 2 021 * SK Y & TELESCOPE

-10°

τ7
τ8

-20°

τ6
τ

NGC 1452

NGC 1407
Let's begin in Eridanus where
NGC 1407 anchors a group of
galaxies with a few members
brighter than 13th magnitude.
The field lies in a bend in the
celestial river midway between
Tau (τ) Ceti and Alpha (α) Leporis,
or about 8¾° almost due south
of Delta (δ) Eridani. The group
is dominated by NGC 1407 and
NGC 1400, the two forming a
bright pair about 12′ apart. Several fainter galaxies in the immediate vicinity just barely overflow
a 1° eyepiece field of view.
The NGC 1407 group is a
subgroup of the larger Eridanus Cloud. Of great interest to
astronomers, it's an example of a
fossil group, which is essentially a
large isolated elliptical galaxy that
results from an extensive merger
of all the galaxies within a small
group. With NGC 1407 we're
perhaps seeing a giant elliptical
galaxy in the making, caught in
the act of cannibalizing a number

of dwarf galaxies in its vicinity.
There are two bright members
of the NGC 1407 group with
interesting identity discrepancies.
(This happens quite often; see
"The NGC 2340 Tangle" sidebar
on page 27 for details on another
mix-up.) Contributing Editor Steve
Gottlieb explains how NGC 1440
was assigned four NGC numbers
(https://is.gd/gottlieb_ngc).
William Herschel discovered this
11.5-magnitude barred spiral on
October 6, 1785. He recorded it
again on September 20, 1786,
but introduced an error of 1° in
declination. His son, John Herschel, observed the object twice
and agreed with German astronomer Arthur Auwers that both of
William's observations were of
the same target. Jean Louis Emil
Dreyer, compiler of The New General Catalogue, recognized the
probable duplication, but gave it
two NGC designations anyway:
NGC 1440 and NGC 1442.

https://www.is.gd/gottlieb_ngc http://www.SHUTTERSTOCK.COM http://www.SHUTTERSTOCK.COM

Sky & Telescope - January 2021

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