Sky and Telescope - June 2018 - 71
NGC 50 0 5: JUDY SCHMIDT / CC BY 2.0; T. RE X: LE A H TISCIONE / S&T; NGC 4889:
N ASA / ESA; 3C 273: ESA / HUBBLE / N ASA; FOSSIL: G HEDOG HEDO / CC BY-SA 3.0
p MONSTER DRAGONFLIES Fueled
by an atmosphere rich in oxygen,
gigantic creatures such as dragonflies with 27-inch wingspans
evolved alongside millipedes 7 feet
long. Can you picture such a world
when you observe NGC 4889?
would lead to the evolution of
One more step remains: 3C 273, in
complex, multicellular life: fungi,
the constellation Virgo, the ﬁrst quasar
plants, animals, and us.
ever to be identiﬁed. As with other quasars,
In this tour we've seen one of
the light from 3C 273 is emitted by matter
almost every important category of astroshredded to plasma in an accretion disk around
nomical object, including a red dwarf, double
the supermassive black hole at the center of a distant galstars, open and globular star clusters, planetary nebulae, a
axy. The central black hole weighs in at around 1 billion solar
star-forming nebula, spiral and elliptical galaxies, and a quamasses. At 2.4 billion light-years away, 3C 273 is the most
sar. Almost all of the deep-sky objects we visited are Messier
distant object easily visible in amateur instruments.
or Caldwell objects, and that's the real moral of the story. A
By now, you may be expecting that the Earth of 2.4 billion
determined observer can learn a tremendous amount about
years ago was in the grip of climate change and mass extincthe structure of the Milky Way and the universe beyond just
tion - and that expectation is correct. Life had already been
by tracking down the Messiers and Caldwells and noting the
up and running for over a billion years, but about 2.4 billion
distances to the various objects. It's a cosmic voyage on the
years ago photosynthesis by cyanobacteria produced the ﬁrst
grandest scale, and a quest I hope you'll continue.
oxygen atmosphere. The Great Oxygenation Event caused
a mass extinction of microbes that could not tolerate free
oxygen and precipitated a severe ice age that lasted almost
¢ MATT WEDEL collects time machines. So far, they only go in
400 million years. In time, however, the oxygen atmosphere
one direction, but he's working on it.
sk yandtelescope.com * J U N E 2 018