Sky and Telescope - July 2017 - 49

19h 30m

Teaspoon

19h 20m

-21°

Path of
Pluto

Path

π

of Plu

to

50

19h 10m

HD 179201

-22°

SAGITTARIUS
-23°

Star magnitudes
3 4 5 6 7 8 9

SAGITTARIUS

SAGITTARIUS

g4
12

16

12

16

8

20

HD 179201

24

Nov 4

HD 179519

28

31

Sept 1

27

23

5

9

13

7

1721
25
29
Oct 3
7
19 15 11

HD 179113

HD 179609

19h 14m

19h 13m

ell, actually you can look now -
if you have a 14-inch or larger
telescope and a sky dark enough to
detect a 14.4-magnitude speck low in
the south. Good luck. Pluto is fading
into the distance year by year, and it's
at declination -21°. We're edging into
a century-plus era when, for practically
all visual observers, Pluto will be nothing but a memory at most. But it will
always remain a fairly easy target for
long-exposure telescopic imagers.
The chart here is your other essential
visual equipment. Pluto is in northern
Sagittarius just below the Teaspoon
asterism, as shown on the small charts
above. The black box on each one shows
the field of the next one up. The large
chart is only 1.2° tall, and its brightest stars are 7th and 8th magnitude.
Use these to start narrowing in on the
precise point where Pluto will be hiding
at the time and date when you look. The
date ticks on Pluto's path are for 0h Universal Time; put a pencil prick at exactly
the right point on the path. As you get
close with the scope, switch to your
highest power to improve the visibility
of the very faintest stars.
The tiniest in these swarms are no
fainter than Pluto itself, so if you think
you see something that ought to be it,
make a careful sketch of its position in
the star field right around it. Come back
in a day or two to see if your suspected
object is moving.

The Name Game

Star magnitudes

8

W

19h 12m

19h 11m

8
9
10
11
12
13
14

The stunningly successful New Horizons flyby of Pluto two years ago, a triumph from start to finish, resurrected
this dwarf planet as an important
object in planetologists' pantheon of
worlds. It's currently more geologically
active than Mercury or Mars, and it's
only the third place in the solar system
where we see plain evidence of an active
hydrological cycle. On Earth, water is the
volatile that evaporates, then rains or
snows out of the atmosphere, flows in
rivers or glaciers to pool in lowlands,
and then evaporates again. On Titan,
it's mixtures of methane and ethane.
On Pluto, New Horizons found nitrogen
s k y a n d t e l e s c o p e .c o m

* J U LY 2 017

49



http://www.skyandtelescope.com

Sky and Telescope - July 2017

Table of Contents for the Digital Edition of Sky and Telescope - July 2017

Contents
Sky and Telescope - July 2017 - Cover1
Sky and Telescope - July 2017 - Cover2
Sky and Telescope - July 2017 - 1
Sky and Telescope - July 2017 - Contents
Sky and Telescope - July 2017 - 3
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