62 ASTRONOMY • JANUARY 2020BINOCULAR UNIVERSE
After the holidays end,
winter can be a gray time
of year. As I look across
my backyard, the ground is cov-
ered with snow and the trees are
bare. Not much color out there.
But what my monochromatic
terrestrial view may lack, the night
sky more than makes up for: The
winter sky abounds with colorful
stars. This month, let’s take a tour
of a few to add a little color back
into our lives.
One of the most intensely col-
ored stars anywhere in the sky is
Orion’s Betelgeuse (Alpha [α]
Orionis). Betelgeuse has always led
a colorful life. There was enough
mass — probably 15 to 20 times
that of our Sun — when it first
came into being some 10 million
years ago to create a blue type O
main sequence star. But since
then, Betelgeuse has squandered its nuclear fuel and
evolved off the main sequence to the land of red super-
giants, where we find it today. A casual glance through
binoculars immediately displays its stunning
ruddy color. Try softening the focus slightly
to further amplify the hue.
Rigel (Beta [β] Orionis) is another vibrant
sight through binoculars. Although desig-
nated as the constellation’s second brightest
star, Rigel actually outshines Betelgeuse by a
quarter magnitude. It’s classified as a spec-
tacular blue-white supergiant. Through
binoculars, the star gleams like an intense
stellar sapphire, in stark color contrast to
ruby-red Betelgeuse.
Aldebaran (Alpha Tauri) has a spectral
type of K. It’s an orange giant star that also puts on a
vivid show through binoculars. The effect stands out
especially well against the backdrop of the Hyades
Cluster. While it certainly appears as though Aldebaran
belongs to the cluster, it’s just a chance, line-of-sight
coincidence. The Hyades is about 150 light-years away,
which makes it one of the closest open clusters to Earth.
A ldeba r a n, howe ver, l ie s at le s s t ha n ha l f t hat d i st a nc e.
Most of the stars in the Hyades appear white, although
a few offer hints of yellow or orange. For instance, the
binocular double star Theta^1 (θ^1 ) and Theta^2 (θ^2 ) Tauridisplays contrasting colors of yellow and white,
respectively.
Some of the most colorful stars in the sky are a
special breed of type M red giants that vary in bright-
ne s s a s convec t ive c u r rent s c a r r y c a rbon mater ia l f rom
deep within to the star’s surface, creating a carbon-rich
outer layer. Just as particulate matter in our own atmo-
sphere causes red sunsets and sunrises, this carbon
layer scatters the blue end of the star’s visible light while
allowing reds and oranges to pass into space and to our
waiting eyes.
One of the best-known carbon stars is R Leporis,
found about 7.5° south-southwest of Rigel. You may be
familiar with it by its popular nickname, Hind’s
Crimson Star, after British astronomer John Russell
Hind, who discovered it in 1845. R Leporis varies in
brightness from magnitude 5.5 to 11.7, with a period of
427 days. As is the case with most carbon stars, R’s red-
ness is most impressive toward minimum brightness.
That’s below most binocular thresholds, but you can
still watch it on its way down. And that’s exactly what
it’s doing now; R passed maximum in early November.
As winter wears on, keep an eye on it as it dims and
reddens toward the next minimum in late spring.
Let’s close out the first month of 2020 with a striking
double star recommended by reader Robert Pickman.
His suggestion is known as h3945, the 3,945th entry in
a double star catalog with over 5,500 members, created
by John Herschel in the early 19th century. It also car-
ries the label 145 G Canis Majoris, the G indicating its
designation in the 1879 Uranometria Argentina by
Benjamin Gould. (Many references incor-
rectly omit the G.) Either way, it’s located 3.6°
northeast of Wezen (Delta [δ] Canis Majoris),
the large dog’s tailbone.
There, we discover a coincidental pairing
of a 5.0-magnitude primary sun with a
5.9-magnitude companion separated by
26.8". That’s tight by binocular standards, but
theoretically possible under ideal sky condi-
tions at 10x. I’ve never had luck splitting
them with my 10x50s, but regularly do so in
my 16x70s. One look through the latter and
it’s clear why h3945 is nicknamed the Winter
Albireo: The brighter star shines with a golden radi-
ance, while the companion looks icy blue. My fellow
Astronomy columnist Glenn Chaple once wrote that
h3945 is “one of the most colorful, yet underrated,
double stars in the heavens.”
Do you have a favorite target you’d like to share
with the rest of us? Contact me through my website,
http://www.philharrington.net.Orion and its region offer gemmy wintertime binocular treats.
Colorful winter stars
The majestic
constellation Orion
offers two dazzling
and colorful stars for
binocular viewers:
Betelgeuse (bright
orange, left of center)
and Rigel (blue-white,
near bottom right).
TONY HALLAS Carbon
stars are
some of the
most
colorful
stars in the
sky.BY PHIL
HARRINGTON
Phil is a longtime
contributor to
Astronomy and the
author of many books.BROWSE THE “BINOCULAR UNIVERSE” ARCHIVE AT
http://www.Astronomy.com/Harrington