Sky & Telescope - May 2019 - 57

Going Deep by Steve Gottlieb

Join the
BillionLight-Year
Club

3C 273

tp ANCIENT PHOTONS. The
quasar 3C 273, at a distance of
some 2 billion light-years in the
direction of Virgo, was the first
object to be identified as such. A
giant elliptical galaxy that hosts
a supermassive black hole, it's
also the source of relativistic
jets. The quasar can be spotted
in a 6-inch scope, but a detailed
finder chart or image is helpful.

Photons that have traveled
for billions of years instill a
sense of awe in the author.

3C 273: ESA / HUBBLE / N ASA; FINDER IM AG E: POSS-II / CA LTECH /
STSCI / PA LO M A R OBSERVATORY; A BELL 20 65: A DA M BLOCK / M OUN T
LEM M ON SK YCEN TER / UNIV ERSIT Y OF A RIZON A / CC BY-SA 3.0

M

y fascination with billion-lightyear galaxies began nearly 40 years
ago when I read about the fabulously
rich and distant Corona Borealis Cluster (Abell 2065) in Burnham's Celestial
Handbook. The cluster features several
hundred elliptical (E) and lenticular
(S0) galaxies packed into a 30′ circle,
the size of the full Moon. Due to the
remoteness of the cluster, its brightest
members are quite dim - close to 16th
magnitude - and Robert Burnham, Jr.
warned they were "far beyond the reach
of the usual amateur telescope."
This was a fair assessment back
in the 1970s. But a few years later I
netted seven elusive fuzzies using my
18-inch reﬂector - after considerable
effort. All were featureless glows, but
the largest was 15.4-magnitude PGC
54876 - a 15″ smudge just 1.4′ east of
an 11.3-magnitude star. Nearby PGC
54883 and PGC 54888 formed a tight
north-south pair that required high
power to split.
PGC 54846, the brightest cluster
member, is situated 20′ south-southwest of the core and 1.5′ northeast of a
9.3-magnitude star. When I nudged the
star just outside the ﬁeld, the galaxy was
visible with direct vision. But the real
reward for this cosmic archaeologist
was peering into the distant past and
savoring the 1 billion-year-old light.
Galaxies classiﬁed as type cD are
enormous ellipticals that dominate the
centers of rich clusters. They've grown

in mass and size through mergers and
are visible at greater distances than
typical galaxies. A gargantuan specimen
is IC 1101, located 80′ northwest of
5.3-magnitude 3 Serpentis. This galactic
leviathan houses a supermassive black
hole that weighs in at 40 to 100 billion
solar masses. IC 1101 is enshrouded in
an immense halo (the largest known)
of very diffuse light extending 4 million
light-years. The envelope consists of
stars stripped from neighboring galaxies
in Abell 2029 and would ﬁt 25 Milky
Ways side by side.
Despite its vast distance (similar to
Abell 2065), IC 1101 shines at magnitude 13.7. It was visible continuously
at 280× as a 15″ × 10″ ellipse of even
surface brightness. The galaxy is centered
within a 9-member circlet of 12th- to
14th-magnitude stars spanning 6′ across.
ESO 146-5 is another monstrous
cD galaxy, found in the southern constellation Indus (note that this target
is out of reach for observers in North
America). This 15th-magnitude heavy-

weight rules the cluster Abell 3827 and
is an extreme case of galactic cannibalism - four giant ellipticals are being
devoured in its core.
ESO 146-5 lies ½° southwest of
orange 5.6-magnitude Kappa2 (κ 2) Indi.
A 12th-magnitude star is parked 1.4′
northwest, providing a handy reference
to pinpoint the location. The galaxy was
barely visible in an 18-inch as a feeble
15″ glow - its ancient light having sped
across the universe for 1.3 billion years.
A 2010 study using the Gemini
South telescope revealed ESO 146-5
has gravitationally lensed a background
galaxy at 2.5 billion light-years. The

PGC 54888

PGC 54876

PGC 54883

u A CLUSTER IN CORONA BOREALIS.
Abell 2065, a cluster of galaxies just shy of
1 billion light-years away in the Northern
Crown, counts several hundred elliptical and
lenticular galaxies. The author was able to spot
seven of these faint galaxies using his 18-inch
reflector. How many can you see?
s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 9

57
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Sky & Telescope - May 2019

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