Sky & Telescope - September 2020 - 59

19h 30m

19h 00m

18h 30m

18h 00m

CYGNUS
ε
δ

α
ζ

Vega

Star magnitudes

+40°

+35°

LYRA

γ
M57

+30°

β Lyr

1
2
3
4
5
6

M57

γ Lyr

M56

ν Lyr

+25°

α
VULPECULA

HERCULES

p FINDING THE RING IS EASY Look for M57 about halfway between Beta (β) and Gamma (γ) Lyrae at 18h 53.6m, +33° 02′.

then and gradually discovered more to
it than its bright, readily apparent ring
and its tiny pinprick of a central star.
One of the Ring's more fascinating
characteristics is its namesake shape.
But is it really a ring? Or might it be an
illusion of perspective?

rver
bse

Contrary to what I wrote a couple of
years ago in an article on M27 (S&T:
July 2018, p. 66), the 3D shape of the
Ring Nebula isn't similar to that of the
Dumbbell Nebula. Instead, recent studies of M57 show that the bright, oval
main ring is a nebulous torus that we
see nearly face on.
The Ring is brightest and most
sharply deﬁned along its minor axis
because this material is closer to the
central star. Note (for example in the
Hubble image on page 58) how the
fainter major axis ends of the Ring seem
to taper as they fade outward, as com-

To o

FINDER FIELD: POSS-II / STSCI / CA LTECH / PA LO M A R
OBSERVATORY; 3D DIAG R A M: G REGG DINDER M A N / S&T,
SOURCE: N ASA / ESA / A . FEILD (STSCI)

The Main Ring

pared to the brighter and more sharply
deﬁned minor axis arcs.
These details are obvious in larger
scopes, but a careful look with an 8-inch
instrument at high power will show
this brightness difference, too. I've also
found that nebula ﬁlters don't bring out
hidden features of the main ring, but
they do make it appear brighter.
At ﬁrst glance, I see the northeast
end of the main ring as the most

Inner
halo

Outer ha
lo

Lobe

Bright knot
Central star

Main ring

u VISUALIZING THE NEBULA This 3D
diagram portrays the geometry and structure of
M57 as viewed from a perspective different to
that of an observer on Earth. It shows the two
halos in relation to the main ring and its internal,
lozenge-shaped bubble. What we see as the
"ring" is in fact the brightest part of the nebula.

Bright knot

Lobe

elongated, but with averted vision the
southwest end pushes out a little farther. In short, the main ring is a cosmic
Cheerio with slightly squashed ends.

The Dark Center
The Ring's dark center is more circular
than oval. It's a striking feature, but,
curiously, what I ﬁrst noticed was the
subtle, gently glowing nebulosity within.
The brightest parts are two evenly
spaced, parallel bands of nebulosity
stretching through the dark center along
the Ring's major axis. Although visible in
most images, I ﬁnd that the bands can
be detected visually only when the sky is
exceptionally transparent. The ﬁrst time
I saw them was on August 6, 1983, with
my 12.5-inch f/7.9 Dobsonian:
I thought I might glimpse the central
star tonight as the sky was clear, dark
and M57 was in the darkest part . . .
When I ﬁrst looked at 117× I thought
I saw it - my heart nearly stopped! At
240× I examined the Ring very closely -
but nothing! Well, not exactly - looking
at the Ring is hardly "nothing!" Nebula
structure was visible with averted
vision in the central hole. Looking at
M57 is always time well spent.
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Sky & Telescope - September 2020

Table of Contents for the Digital Edition of Sky & Telescope - September 2020