Sky & Telescope - January 2020 - 58

JANUARY 2020 OBSERVING
Going Deep by Ted Forte

Fishing in Pisces
The Pisces Cloud contains many faint galaxies - be prepared to probe deep to spot them.
bout 230 million light-years from
Earth, on the edge of the PerseusPisces Supercluster, lies a string of
elliptical galaxies known as the Pisces
Cloud (or the Pisces Chain). Hovering
around 13th magnitude, the brightest
members of this group are accessible to
an 8-inch telescope. Owners of largeaperture scopes might track down
more than 50 galaxies within 1° of the
group's brightest member, so this is a
good area in which to test your mettle
and push your optics.
One of the things I ﬁnd most intriguing about deep-sky observing is the sense
of retracing the steps of the great visual
astronomers of the past. This group of
galaxies has an interesting history that
begins on September 12, 1784, with William Herschel at Datchet in Berkshire,
England. Herschel's Sweep 268 with the
"large 20-foot" (18.7-inch aperture)
reﬂector encompassed six objects in the
area and included the brightest member
of the group, NGC 383.
NGC 383 is a radio galaxy, an active
galaxy that is very luminous at radio
wavelengths. The core of the galaxy

harbors a supermassive black hole and
is the site of intense activity that acts
as a launchpad for powerful jets. When
these high-speed jets interact with the
intergalactic medium, they give rise to
bright radio emission via the synchrotron process (when relativistic charged
particles, usually electrons, spiral in
a magnetic ﬁeld). However, none of
this is visible through the eyepiece of a
telescope. Instead, we see only a slightly
elongated object with a nearly round
bright core. Herschel assigned NGC 383
to his group II (faint nebulae).
Herschel didn't record as a separate object NGC 383's small, round
companion, NGC 382, about 30″

southwest of its core. That remained
for the second wave of discovery that
Irish engineer Bindon Stoney conducted at Birr Castle on November 4,
1850. Using the giant "Leviathan of
Parsonstown," the 72-inch reﬂector
built by William Parsons, 3rd Earl of
Rosse, Stoney added ﬁve more objects
to the then-known "nebulae" in the
group. Later observations by other Birr
Castle observers - Heinrich d'Arrest,
Lawrence Parsons (son of William),
Guillaume Bigourdan, R. J. Mitchell,
Robert Ball, John Dreyer, and Herman
Schultz - added another 10 objects to
the group by 1886. Edwin Hubble and
Milton Humason identiﬁed 25 galaxies

q FINDER CHARTS You'll find the Pisces Cloud in the northern reaches of the constellation that
bears its name, northwest of M33, or the Triangulum Galaxy, and south of Beta Andromedae. The
box in the finder chart below represents the area portrayed in the image at right. The chart below
left shows the positions of the Cloud members in relation to nearby stars.

1h 40m

1h 20m

1h 00m

0h 40m

ANDROMEDA

410

6
7
8
9
10
11
12

392
403

+33°

374

399

383

398

1h 10m

+32°
76

1h 05m

JANUARY 2 02 0 * SK Y & TELESCOPE

2
3
4
5
6
7
8

HD 7033

82
M33

HD 7033

1h 15m

Star magnitudes

TRIANGULUM

+35°

PISCES

σ
δ

+30°

τ
ε

PISCES CLOUD IM AG E: POSS-II / STSCI / CA LTECH /
PA LO MAR OBSERVATORY

Sky & Telescope - January 2020

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