Sky and Telescope - April 2015 - 40

The Herschel Sprint

NASA / ESA / K. COOK (LAWRENCE LIVERMORE NATIONAL LABORATORY, USA)

NGC 4921.

The face-on barred spiral galaxy NGC 4921 in Abell 1656 displays
a bright core surrounded by a large low surface brightness halo.

NGC 4798, and things once again became busy for the
observing team. Fifteen cluster members were recorded
during the next eight minutes. NGC 4816, NGC 4827,
NGC 4840, and NGC 4841 all appear similar visually;
they're classed as either lenticular or elliptical galaxies,
with NGC 4841 having a very slightly smaller and fainter
companion immediately northeast. NGC 4839, a giant
15h 50m

15h 40m

15h 30m

15h 20m

elliptical galaxy, measures as one of the largest in the
cluster. William laconically described all these galaxies as
"faint, pretty large."
Swinging into the heart of the Coma Cluster, William
noted two galaxies that present modern observers with
an intriguing viewing challenge. NGC 4869 and NGC
4874 were recorded together and described as, "Two. The
time taken between them." Both were recorded as class II
objects (faint), though visually, NGC 4874 appears larger
and brighter. A much fainter object, NGC 4872 appears
embedded in the outer halo of NGC 4874 to the southwest. Until recently, it was presumed that NGC 4872 was
the galaxy described by William. The confusion stems
from Heinrich d'Arrest's explorations of this same region
in 1864. Observing two galaxies at the same position,
d'Arrest concluded that the faint NGC 4872 was William's
discovery; he thus recorded NGC 4874 as a new object.
A little more than 1° south of NGC 4874, William
°
observed NGC 4892, an edge-on spiral galaxy located
well away from the main concentration of the cluster;
visually, it appears as an extended oval of subtle light, just
following two brighter ﬁeld stars.
IC 4051, another victim of mistaken identity, lies just
east of NGC 4889. It now seems clear that IC 4051, a
discovery credited to Guillaume Bigourdan and Hermann
Kobold in Dreyer's Second Index Catalogue, and NGC
4908, credited to Heinrich d'Arrest, are one and the same
object - Herschel's Class III object III 363. To confuse matters even more, in his General Catalogue, John
Herschel equated III 363 with a galaxy he discovered,
h1510 (NGC 4894), an error carried over into Dreyer's
New General Catalogue. As Dreyer noted, "This region is
so very crowded that it is not easy to identify a very faint
nebula." All editions of Uranometria 2000.0 plot NGC
15h 10m

15h 00m

14h 50m

5798

+30°

5773

+28°

β

5958

6001

CORONA

5771

+30°

BOOTES
+28°

BOREALIS
α

δ

γ

+26°

+26°

15h 50m

40

15h 40m

April 2015 sky & telescope

15h 30m

15h 20m

15h 10m

15h 00m

14h 50m

Sky and Telescope - April 2015

Table of Contents for the Digital Edition of Sky and Telescope - April 2015

Contents
Sky and Telescope - April 2015 - Cover1
Sky and Telescope - April 2015 - Cover2
Sky and Telescope - April 2015 - 3
Sky and Telescope - April 2015 - Contents
Sky and Telescope - April 2015 - 5
Sky and Telescope - April 2015 - A
Sky and Telescope - April 2015 - B
Sky and Telescope - April 2015 - 6
Sky and Telescope - April 2015 - 7
Sky and Telescope - April 2015 - 8
Sky and Telescope - April 2015 - 9
Sky and Telescope - April 2015 - 10
Sky and Telescope - April 2015 - 11
Sky and Telescope - April 2015 - 12
Sky and Telescope - April 2015 - 13
Sky and Telescope - April 2015 - 14
Sky and Telescope - April 2015 - 15
Sky and Telescope - April 2015 - 16
Sky and Telescope - April 2015 - 17
Sky and Telescope - April 2015 - 18
Sky and Telescope - April 2015 - 19
Sky and Telescope - April 2015 - 20
Sky and Telescope - April 2015 - 21
Sky and Telescope - April 2015 - 22
Sky and Telescope - April 2015 - 23
Sky and Telescope - April 2015 - 24
Sky and Telescope - April 2015 - 25
Sky and Telescope - April 2015 - 26
Sky and Telescope - April 2015 - 27
Sky and Telescope - April 2015 - 28
Sky and Telescope - April 2015 - 29
Sky and Telescope - April 2015 - 30
Sky and Telescope - April 2015 - 31
Sky and Telescope - April 2015 - 32
Sky and Telescope - April 2015 - 33
Sky and Telescope - April 2015 - 34
Sky and Telescope - April 2015 - 35
Sky and Telescope - April 2015 - 36
Sky and Telescope - April 2015 - 37
Sky and Telescope - April 2015 - 38
Sky and Telescope - April 2015 - 39
Sky and Telescope - April 2015 - 40
Sky and Telescope - April 2015 - 41
Sky and Telescope - April 2015 - 42
Sky and Telescope - April 2015 - 43
Sky and Telescope - April 2015 - 44
Sky and Telescope - April 2015 - 45
Sky and Telescope - April 2015 - 46
Sky and Telescope - April 2015 - 47
Sky and Telescope - April 2015 - 48
Sky and Telescope - April 2015 - 49
Sky and Telescope - April 2015 - 50
Sky and Telescope - April 2015 - 51
Sky and Telescope - April 2015 - 52
Sky and Telescope - April 2015 - 53
Sky and Telescope - April 2015 - 54
Sky and Telescope - April 2015 - 55
Sky and Telescope - April 2015 - 56
Sky and Telescope - April 2015 - 57
Sky and Telescope - April 2015 - 58
Sky and Telescope - April 2015 - 59
Sky and Telescope - April 2015 - 60
Sky and Telescope - April 2015 - 61
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Sky and Telescope - April 2015 - 63
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Sky and Telescope - April 2015 - 86
Sky and Telescope - April 2015 - Cover3
Sky and Telescope - April 2015 - Cover4
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