Sky & Telescope - USA (2020-01)

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.

A

bout 230 million light-years from

Earth, on the edge of the Perseus-

Pisces 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 large-

aperture 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 fi nd most intrigu-

ing 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 Wil-

liam Herschel at Datchet in Berkshire,

England. Herschel’s Sweep 268 with the

“large 20-foot” (18.7-inch aperture)

refl ector 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 synchro-

tron process (when relativistic charged

particles, usually electrons, spiral in

a magnetic fi eld). 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 sepa-

rate object NGC 383’s small, round

companion, NGC 382, about 30′′

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58 JANUARY 2020 • SKY & TELESCOPE

southwest of its core. That remained

for the second wave of discovery that

Irish engineer Bindon Stoney con-

ducted at Birr Castle on November 4,

1850. Using the giant “Leviathan of
      Parsonstown,” the 72-inch refl ector
      built by William Parsons, 3rd Earl of
      Rosse, Stoney added fi ve 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 identifi ed 25 galaxies

1 h 15 m 1 h 10 m 1 h 05 m

383

392

410

403 374

399

398

HD 7033

(^7876) σ
82
+33°
+32°
St
ar
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ag
ni
tu
de
s 6
7
8
9
10
11
12
M33
HD 7033
82
π
ε
δ
μ
β
σ
τ

ANDROMEDA

1 h 20 m 1 h 00 m 0 h 40 m

PISCES

TRIANGULUM

+30°

+35°

1 h 40 m

St

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3 4 5 6 7 8

qFINDER CHARTS You’ll fi nd 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 fi nder 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.