Sky & Telescope - December 2018 - 24

Bright Stars

his time of year is nothing without its traditions.
One of my favorites is taking a break from the holiday rush to spend time with friends on New Year's
Eve and track down all 15 ﬁrst-magnitude stars visible from
mid-northern latitudes. They're all above the horizon at some
point between sunset on December 31st, New Year's Eve, and
sunrise on January 1st, the morning of New Year's Day. The
other six brightest stars in Earth's skies are too far south for
most of us clustered here farther north to see without some
exciting travel. It's fun to use the boost we get from the long
nights around the winter solstice for own little "Naked-Eye
Marathon." (Those of you familiar with the Messier Marathon know that the aim is to ﬁnd as many of the 110 Messier
objects in one night as possible.) Let's get to it - bundle up,
grab a pre-festivities glass of champagne, maybe even a piece
of that giant sandwich, and head outdoors.

The Summer Triangle
The last time most of us contemplated the Summer Triangle,
it was likely shining above us after a long, slow, summer
sunset. Back in August, the constellations Cygnus and Aquila

Deneb

Vega

soared high overhead with Lyra vying for attention, their
bright stars lighting up those sweltering nights. Believe it or
not, the Summer Triangle's stars are still twinkling in the
evening's chilly skies. Let's start our tour with that trio and
look westward right after sunset. Just as twilight deepens,
we'll see the Swan and Eagle glide toward the horizon as they
chase after the Sun.
Altair, whose formal name, Alpha (α) Aquilae, indicates
that it's the brightest star in the Aquila constellation (there
are some exceptions to this convention), and Vega (Alpha
Lyrae) are among the closest stars to Earth, only about 27
and 25 light-years away, respectively. Deneb (Alpha Cygni)
anchors the Swan's tail and is, on the other hand, one of
the most distant stars we can see with the naked eye. It's
an old giant star whose exact distance is a little tough to
pin down. Estimates are that its light has been traveling to
us for about 2,000 years, with some studies placing it even
as distant as 3,000 light-years. Even from that far, it's still
very bright, but it remains fainter than the other two - its
distance really shows.
The trio is wonderful in summer, but there's something
special about seeing these stars in the dusky early evening
sky in winter and letting your mind wander back to hot dogs,
baseball games, and trips to the beach.
Don't drag your feet on this, but there's no need to rush,
either. Altair sets around 7:30 p.m. for viewers at latitudes
around 40° north, with Vega and Deneb not too far behind.
If you're fortunate enough to live under good, dark skies,
away from the worst of the light pollution, you might also be
able to make out the Milky Way's glow cutting right through
the center of the Triangle.

Dusty Disk

t SUMMER TRIANGLE Surprisingly, the three stars of the Summer
Triangle are still visible in the depth of winter. But they're very low on the
western horizon right after sunset, so be ready to head outdoors as soon
as daylight fades to start your naked-eye marathon. Can you make out
the Swan, the Eagle, and the Lyre?

DECE MBE R 2 018 * SK Y & TELESCOPE

A K IR A FUJII

Altair

While we're still looking toward the west after locating
the ﬁrst three stars, it's just a quick hop to the fourth. The
southernmost ﬁrst-magnitude star visible in the Northern
Hemisphere is Fomalhaut, whose name comes from Arabic
and means "the mouth of the whale." Piscis Austrinus, the
Southern Fish (not to be confused with Pisces, the directionally agnostic ﬁsh) is a dim and sparse constellation that can
be tough to discern because our view of it puts it low in the
southern sky. Fomalhaut, at declination -29°, never rises
more than about 20° above the horizon for mid-northern
latitudes. Yet as Fred Schaaf mentions in his book The Brightest Stars, Fomalhaut is the zenith star for the middle latitudes
in the Southern Hemisphere! Traveling south on the celestial
sphere, Fomalhaut is the only ﬁrst-magnitude star between
Antares (at declination -26°, more on this star later) and the
next one at declination -53°, Canopus in Carina.

Sky & Telescope - December 2018

Table of Contents for the Digital Edition of Sky & Telescope - December 2018