Sky & Telescope - October 2021 - 33

teducati and Weaver. In 1994, Walter Saurer (University of
Innsbruck) and his colleagues announced the identification
of six meager clusters, including Saurer 1, a 2′ sprinkling
of 17th-magnitude and fainter stars. Its distance of 63,000
light-years and location are compatible with the trailing tail.
Saurer 1 hides in the southwest corner of Canis Minor,
1° south-southeast of 5.9-magnitude HD 56989. I found it
a tough sighting and only detected a dim 20″ smudge - the
combined glow of the brightest four or five red giants.
In Conclusion
In 1975 Howard Bond (Pennsylvania State University)
discovered BoBn 1 during an objective-prism survey at
the Cerro Tololo Inter-American Observatory in northern
Chile. At the eyepiece of the 60-inch reflector, he reported
a " slightly soft appearance in good seeing, " suggesting a
diameter of 1″ to 2″. Further analysis in 2006 found a highexcitation
spectrum and a distance of 65,000 light-years
within the leading wing of L.
Look for BoBn 1 in western Cetus, 50′ west-northwest of
the 11th-magnitude galaxy NGC 210. A 10th-magnitude star
8′ due east provides a handy marker as the planetary is stellar
and shines feebly at magnitude 15.7. I used a narrowband
filter to quickly " blink " and confirm the identification.
A final census of Milky Way globulars stolen from the
Sagittarius Dwarf galaxy (and other former dwarfs) is incomplete.
NGC 5634 lies in a region shared by stellar debris from
other progenitors including the Helmi Stream, so it may have
a different origin. Several recent studies show the kinematics
of the Intergalactic Wanderer, NGC 2419, is consistent with
the Sagittarius Stream, so it may be added to the list. Future
improved data and models of the tidal streams should help
sort out a complete inventory.
Riders on the Stream
Object
Type
M54
Terzan 7
Terzan 8
Arp 2
Hen 2-436
Wray 16-423
Palomar 12
NGC 5634
Whiting 1
Berkeley 29
Saurer 1
BoBn 1
Globular cluster
Globular cluster
Globular cluster
Globular cluster
Planetary nebula
Planetary nebula
Globular cluster
Globular cluster
Globular cluster
Open cluster
Open cluster
Planetary nebula
γ
M77
ο
η
2
3
4
5
6
7
π
τ
ERI
τ1
υ
β
-20°
FINAL CHALLENGE Wrap up your survey of the Sagittarius Stream
with the challenging planetary nebula BoBn 1.
The Sagittarius Dwarf Spheroidal's traces are huge indeed.
Every time the galaxy orbits the Milky Way, several million
solar masses are yanked away from our hapless neighbor.
But although its star streams and globulars will ultimately
disperse across the Milky Way halo and into the disk, they'll
never completely lose their ancestral roots.
¢ Contributing Editor STEVE GOTTLIEB has been exploring
galaxies, both near and far, for more than 40 years. He can be
reached at astrogottlieb@gmail.com.
EXTRA MATERIAL For an animation of the Milky Way's " phase
spiral " see https://is.gd/galactic_whack. Also, to better understand
the movements of stars in the galaxy, see this post by
Ronald Drimmel: https://is.gd/drimmel. For finder charts/images,
go to https://is.gd/SgrFinders.
δ
2h
Whiting 1
HD 12262
θ
ζ
η
BoBn 1
CETUS 210
ι
-10°
1h
0°
Mag(v)
7.7
12.0
12.4
12.3
14.2
13.8
11.7
9.4
15
-
-
15.7
Size
9.1′
2.6′
5.0′
2.5′
0.5″
1″
2.9′
4.9′
0.5′
3.7′
2.6′
2″
RA
18h 55.0m
19h 17.7m
19h 41.7m
19h 28.7m
19h 32.1m
19h 22.2m
21h 46.6m
14h 29.6m
02h 02.9m
06h 53.1m
07h 20.9m
00h 37.3m
Dec.
-30° 29′
-34° 39′
-34° 00′
-30° 21′
-34° 13′
-31° 31′
-21° 15′
-05° 59′
-03° 15′
+16° 56′
+01° 48′
-13° 43′
Arm
M
M
M/T
M/T
Dist. (k l-y) Age (My)
90
80
90
94
13.5
8.0
13.0
13.5
T/L?
T
T
L
L?
L
M - -
M - -
60
85
95
43
43
-
5.7
-
-
- -
Distances are from the solar system. Sizes are from recent catalogs. 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.
-
sk yand tele scope .o r g * OCTOBER 2021 33
Star magnitudes

https://www.skyandtelescope.org/astronomy-news/pattern-in-milky-ways-stars-suggests-recent-galactic-whack/ https://www.is.gd/drimmel https://www.is.gd/SgrFinders http://skyandtelescope.org

Sky & Telescope - October 2021

Table of Contents for the Digital Edition of Sky & Telescope - October 2021