Sky and Telescope - January 2018 - 65

Capella

+45$

¡
59

1664

+40$

AURIGA

1778
M38

+35$

1907

M37

IC 410
1893

the Waves

+30$

TA U R U S

14
Star magnitudes

M36

1
2
3
4
5
6
7

CH A RT: G REGG DINDER M A N / S&T, SOURCE: SK Y & TELESCOPE 'S POCKE T
SK Y ATL AS; M37 & M38: A N THON Y AYIO M A MITIS (2)

open clusters is just over 3,000 light-years, but we gaze at
NGC 1893 across an astonishing 11,000 light-years. Even
at that distance, it subtends nearly ½°, corresponding to an
actual diameter of more than 80 light-years - this seeming
minnow is actually a distant leviathan. The cluster is embedded in the faint nebula IC 410, from which it formed only
four million years ago. I've never spotted the nebula myself,
but 15× will resolve a ragged line of stars aligned almost perfectly north-to-south, aimed between the two Waves.
Just off the northern end of the smaller wave you'll ﬁnd
M38. Pause for a moment, though, and have a look at NGC

M37

1907 (Stop 13), ½° to the south. Comparing the two open
clusters is instructive - NGC 1907 is both smaller in diameter and about a third again as distant as its brighter and
more famous neighbor. Like many of the non-Messier clusters
on this tour, it's just a fuzzy ball of ﬂuff at 7×, but it starts to
resolve at 15×.
Comparing clusters is the name of the game in the next
stretch of the tour: We've arrived at the Messier trio of M38,
M36, and M37 (Stops 13 and 14). M36 is 2° southeast of
M38, and M37 is just over 3° east-southeast of M36. All told
the three span just over 5°, so they'll ﬁt into the ﬁeld of view
of most 7×50 and 10×50 binoculars. With the smaller ﬁeld
of 15×70s you'll have to pick two clusters at a time to observe
and compare.
All three clusters lie at roughly the same distance from
us, between 4,300 and 4,600 light-years away, so the differences you see mostly correspond to astrophysical reality.
M38 looks the largest, and it is - its diameter is about 26
light-years, compared to 12 for M36 and 18 for M37. M36 has
the fewest stars, but it is the ﬂashiest of the three, a compact
shotgun blast of brilliant blue-white stars. M37 is by far the
richest, with hundreds of suns compared to the dozens in
the other two clusters. Although technically intermediate in
size between the other two, it often looks the smallest - the
cluster's diffuse outer members are hard to detect in handheld binoculars, and what registers as "the cluster" in small
instruments is in fact its dense core, only about 5″ across.
I called this a tour, but it's been more of a blitz, hitting a
few showpiece objects but rocketing past many more. Perseus
and Auriga will reward further exploration, whether you seek
to understand the structure of our galaxy, or just relax and
appreciate the beauty of the night sky. Don't take my word for
it - go see for yourself.
¢ Contributing Editor MATT WEDEL is frankly a little alarmed
about trying to understand the night sky in a single lifetime.
But he's enjoying the attempt.

M38

sk yandtelescope.com * JA N UA RY 2 018

http://www.skyandtelescope.com/

Sky and Telescope - January 2018

Table of Contents for the Digital Edition of Sky and Telescope - January 2018