Sky & Telescope - February 2021 - 49

minute and takes around one second
to cross the disk of the Sun or Moon.
(Be sure to use a suitable solar filter
when attempting to observe a solar
transit.) Binoculars show the space
station as a dark speck while a telescope magnifying 50× will clearly
show its shape. If you're lucky, the
ISS will pass in front of the crescent
Moon, and you'll see it dramatically
illuminated against the dim, earthlit portion of the lunar disk.
To photograph an ISS transit,
attach your camera to a telescope or
long telephoto lens. Because these
events are so brief, the trick is to
shoot multiple images centered on
the predicted transit time. You can
either use your camera's burst mode,
or record a video sequence. For an
excellent tutorial on the subject, go
to is.gd/isstransitimage.

R Virginis and Chi Cygni Top Out
A YEAR AGO, Betelgeuse kept us in a thrall as it faded to magnitude 1.8 - its
faintest in recorded history. Observations made with the Hubble Space Telescope
revealed that a large convection cell of super-hot stellar gas had welled up inside
the bright Orion variable, and as the material ascended, it cooled and condensed
to form a cloud of dust that partially dimmed our view of the star.
Variable stars can be full of surprises, which is one reason they're so fascinating to watch. On February 24th, Mira-type variable R Virginis reaches its
maxima of around magnitude 6, making it an easy binocular target. R completes
a full pulsation cycle every 145.6 days, so if you start watching then you'll see
the star fade to around 12th magnitude later this spring before it returns to
maximum again in late July.
In the morning sky, look for Chi (χ) Cygni - another bright Mira-type
variable. The star is expected to reach maximum brightness (typically around
magnitude 5) on March 4th, but you'll want to start watching earlier than that
to see it brighten. Chi has been known to rise as bright as magnitude 3.3 and
plummet to as faint as magnitude 14.2 over its 408-day cycle.
You'll find detailed maps and additional information for both stars at the
website of the American Association of Variable Star Observers: aavso.org.

A Pair of Evening Asteroids
TWO LESSER-KNOWN bright asteroids reach opposition this
month: 18 Melpomene (February 1st) and 29 Amphitrite (on
February 21st).
Melpomene shines at magnitude 9.4 in Cancer and will be
in the same medium-power telescope field as Alpha (α) Cancri on and around opposition night. Amphitrite is a smidgeon
brighter at magnitude 9.2 and located in central Leo. Both are
easy catches in a small telescope. (The paths for both objects
are depicted in the charts below.)
The two objects are members of the S-type or " stony "
9h 10m

9h 00m

8h 50m

8h 40m

asteroids. Amphitrite is one of the largest of its kind, with
a diameter of about 200 kilometers, while Melpomene is
slightly smaller at 140 kilometers. Their light curves indicate
that these space rocks have approximately spherical shapes.
In the early days of the solar system, Jupiter's powerful
gravity stirred up the material orbiting between it and Mars,
preventing millions of individual bodies from coalescing into
a single, larger one. Had those pieces come together, we'd
instead have one additional dwarf planet about 1.4 times the
size of Ceres. A nod to Jupiter - I think we got the better deal!
10h 40m

10h 30m

10h 20m

10h 10m

η
19
17
15
13

CANCER

Pa

t

f
ho

18

lp
Me

e
om

26

28

11
5

7

Mar 1
+14°

3

α

M67

+12°

Feb 9
11 13

24
20

22

18
Jan 16

LEO

+14°

9

ne
Feb 1
30

+16°

13 15
7 9 11
3 5

27
23 25
19 21
te
17
15
phitri

Path

Am
of 29

Regulus

+12°
Star magnitudes
4 5 6 7 8 9

+10°

α

Star magnitudes
3 4 5 6 7 8 9

sk yandtelescope.org * FEBRUARY 2 021

49


http://www.aavso.org http://www.is.gd/isstransitimage.com http://www.skyandtelescope.org

Sky & Telescope - February 2021

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

Contents
Sky & Telescope - February 2021 - Cover1
Sky & Telescope - February 2021 - Cover2
Sky & Telescope - February 2021 - 1
Sky & Telescope - February 2021 - Contents
Sky & Telescope - February 2021 - 3
Sky & Telescope - February 2021 - 4
Sky & Telescope - February 2021 - 5
Sky & Telescope - February 2021 - 6
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