Sky & Telescope - January 2022 - 49

7h 50m
+18°
81
7h 40m
74
7h 30m
7h 20m
3
4
5
6
7
8
9
GEMINI
+16°
68
Jan
1
3
5
7
9
11 13 15 17
P a t h
λ
19 21 23 25 27 29 31 Feb
o f 7 I r
2
+14°
2395
Medusa
Nebula
Eye on Iris
BINOCULARS ARE OFTEN underappreciated.
Many skywatchers leap from
naked-eye observing to a telescope and
bypass the humble handheld instrument.
I've learned to utilize binoculars
more and more over the years and can't
think of a better way to put them to
good use this month than by tracking
down the asteroid 7 Iris. It comes to
opposition on January 13th in southern
Gemini, where it glows at magnitude
7.7. That's a little brighter than Neptune,
which means Iris is well within
reach of 50-mm binoculars from a
moderately dark site.
Around opposition, Iris advances
westward about ¼° each night and ends
the month ¾° south-southeast of the
3.6-magnitude star Lambda (λ) Geminorum.
If you watch closely, you can
perceive its night-to-night motion even
in binoculars by carefully noting its
changing position against the background
stars.
English astronomer John Russell
Hind discovered Iris from London, England,
in August 1847 during a systematic
search following the discovery of
Neptune the previous year. Named for
the Greek rainbow goddess, Iris is the
fourth-brightest minor planet and has
a mean diameter of 214 kilometers. Its
β
Pollux
κ
+20°
λ
Path of
7 Iris
+10°
CANIS
MINOR
α
Procyon
γ
β
7h 30m
7h 00m
6h 30m
reflective surface is pocked by craters,
eight of which are between 20 and
40 kilometers across and bear Greek
names for the colors of a rainbow, such
as Chloros (green) and Cyanos (blue).
These features were discovered with the
Very Large Telescope's SPHERE instrument.
Iris
orbits the Sun every 3.7 years and
rotates once every 7.1 hours. Remote
examination of its surface reveals
similarities to LL-chondrite (low-iron)
meteorites. Familiar examples include
the Chelyabinsk meteorite fall of February
2013 as well as the asteroid Itokawa,
which the Japanese probe Hayabusa
visited in 2005, returning samples of
the asteroid to Earth in June 2010.
And now you can grab your own
retinal " sample " of Iris photons.
ξ
MONOCEROS
GEMINI
δ
ζ
γ
PK 205+14.1
ι
υ
ε
μ
ν
η
Moonless
Quads
NORMALLY, MOONLESS CONDITIONS
for any meteor shower would
be cause to celebrate, but the annual
Quadrantids are fussy. While up to
120 meteors per hour could be visible
under ideal conditions, the shower's
peak lasts only about 4 hours. If
you miss that brief window, the rate
plummets to about 25 per hour -
though that's still a bit better than a
typical Lyrid or Orionid display.
This year the Quads are expected
to peak around 20:40 UT (3:40 p.m.
Eastern Time) on January 3rd, which
favors observers in Asia and at
eastern European longitudes. North
American skywatchers will still see
a shower, but one with the volume
turned down. Because of the timing
of the peak, it's likely the mornings
of the 3rd and 4th will both offer
good viewing. Watch between 3 a.m.
and dawn when the radiant stands
highest in the northeastern sky.
pAstrophotographer Petr Horálek captured
this composite photo of the 2020 Quadrantid
meteor shower above a snowy Slovakian
landscape. The peak of this year's display
favors observers (and photographers) in
Eastern Europe and Asia.
sk yand tele scope .o r g * JANUARY 2022 49
2355
i s
Star magnitudes
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Sky & Telescope - January 2022

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