Sky & Telescope - May 2019 - 59

p Left: Abell 1413, a cluster that houses PGC 37477 among its 300 members, is located between Leo and Coma Berenices at a distance of almost
2 billion light-years. Strong interactions between the gravitationally bound galaxies heat up the intergalactic gas to such high temperatures that it
emits X-rays. Right: The quasar APM 08279+5255 lies more than 12 billion light-years away. This means that the photons that left it have traveled for
some 90% of the age of the universe. This Chandra X-ray image of outflows from the source shows a double structure that results from gravitational
lensing by a massive foreground object.

ber 29th at an astonishing apex: The
pre-solar light of CTA 102 reached magnitude 11.3 and was easily in the range
of a 4-inch scope!
But of all my observations of ancient
light, the long-distance title is held by
16.2-magnitude APM 08279+5255.
This radio-quiet quasar in Lynx was
found serendipitously in 1998 during
a spectroscopic survey of carbon stars.
With a phenomenal light travel time
of 12.1 billion years, APM 08279+5255
appeared to researchers to be "easily
the most intrinsically luminous object

known." But they cautioned, "the prodigious nature of this object is most likely
a consequence of gravitational lensing."
Follow-up investigations in 1999
utilized the near-infrared camera on the
Keck I telescope and the near-infrared
spectrometer (NICMOS) on the Hubble
Space Telescope. These studies conﬁrmed there are three lensed images
separated by 0.4″ with the light ampliﬁed between 90 and 100 times. A 2008
analysis of the molecular CO properties trimmed the magniﬁcation boost
to 4, indicating the quasar's intrinsic

luminosity exceeds 1,000 trillion times
(1015) the Sun's luminosity.
Visually, APM 08279+5255 was just
a barely-there speck in my 18-inch
scope. But it was simultaneously thrilling and humbling to contemplate that
those few photons had been traveling at
186,000 miles/second for nearly 90% of
the age of the universe!
¢ Contributing Editor STEVE GOTTLIEB
is often looking for new "far out" experiences at dark sites in Northern California.
His email is astrogottlieb@gmail.com.

The Billion-Light-Year Club
PGC 37477: ESA / HUBBLE / N ASA; A PM 0 8279+5255: N ASA /
CXC / PSU / G. CH A RTAS / M. WEISS

Object
PGC 54876
PGC 54846
IC 1101

Mag(v)

z

Light Travel Time (Gyr)

RA

Dec.

Comments

15.4

0.07

0.9

15h 22.4m

+27° 43′

Abell 2065

1.0

15h

21.9m

+27° 25′

Abell 2065

1.1

15h

10.9m

+05° 45′

Abell 2029

01.9m

15.1
13.7

0.08
0.08

ESO 146-5

15.0

0.10

1.3

22h

-59° 57′

Abell 3827

PGC 37477

15.2

0.14

1.8

11h 55.3m

+23° 24′

Abell 1413

2.0

12h

29.1m

+02° 03′

First identiﬁed quasar

7.9

22h

32.6m

+11° 44′

V=11.3 maximum

12.1

08h

31.7 m

+52° 45′

Most distant viewed

3C 273
CTA 102
APM 08279+5255

12.8
17.3
16.2

0.16
1.04
3.91

Distance is expressed as light travel time. An average value of H0 = 70 km/s/Mpc was used to calculate distances using redshifts. Visually, an object's size is often
smaller than the cataloged value and varies according to the aperture and magnification of the viewing instrument. Right ascension and declination are for equinox
2000.0. For more targets, see https://is.gd/GDMay2019.

s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 9

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Sky & Telescope - May 2019

Table of Contents for the Digital Edition of Sky & Telescope - May 2019
