The Caldwell Objects

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6 4
Tau Canis Majors Cluster;
“Northern” Jewel Box;
Mexican Jumping Star;
Liquid Pyramid
NGC 2362
Type: Open Cluster
Con: Canis Major
RA: 07 h 18.7 m
Dec: -24° 57'
Mag: 4.1
Diam: 6'
Dist: 5,100 light-years
Disc: Giovanni Batista Hodierna,
before 1654
W. H ERSCHEL: [Observed 6 March 1785] A very beautiful cluster of
pretty [bright] stars, very rich, contain [s] the [star] 30 Canis [Majoris].
(ΗVII-17)
I N THE LOWER BACKBONE OF C ANIS M AJOR,
Orion's greatest hunting dog, is one of the most
inconspicuous yet visually stunning open clusters
accessible to observers in both hemispheres.
NGC 2362 is called the Tau (τ) Canis Majoris
Cluster by most, but I call it the "Northern" lewel
Box. I place "Northern" in quotes because the
cluster is north of the original Jewel Box cluster
(Caldwell 94) but south of the celestial equator.
The two Jewel Boxes have much in common.
Both have Greek-letter designations; the Jewel
Box is also known as Kappa (κ) Crucis. Both
shine at 4th magnitude; both are roughly 5,000
light-years distant; and both are among the
youngest star clusters known, with ages of a few
million years. In his Astronomical Objects for
Southern Telescopes, Ernst Hartung writes: "This
most beautiful cluster contains about forty stars
grouped around the very bright white 30 [Canis
Majoris] which is set like a jewel in their midst."
254
GC: Cluster, pretty large, rich.
NGC: Cluster, pretty large, rich (30 Canis Majoris).
Shining at magnitude 3.8, the Tau Canis Majoris
Cluster is about 13° southeast of dazzling Sirius
and nearly 3° northeast of 2nd-magnitude Delta
(δ) Canis Majoris. The cluster is only 0.7
magnitude fainter than M44, the famous Beehive
Cluster in Cancer. Yet look at the star called Tau
Canis Majoris with the naked eye and you'd
never know a cluster existed around it. That's
because the stars in NGC 2362 are packed into an
area only 6' across (1/12 the Beehive's angular
diameter).
Contrary to popular belief, William Herschel
did not discover the Tau Canis Majoris Cluster;
he rediscovered it. The honor goes to Giovanni
Batista Hodierna (1597-1660), whose observations
appeared in his De Admirandi Coeli Caracteribus —
a catalog, published in 1654, of some 40 deep-sky
objects. The catalog somehow escaped Herschel's
notice, and indeed the modern world's, until
Giorgia Fodera Serio, Luigi Indorato, and Pietro
Nastasi
Deep-Sky Companions: The Caldwell Objects