Sky and Telescope - April 2018 - 45

Under the Stars by Fred Schaaf

Springtime Skies
Spring ushers in special sights of stars, planets, and more.

TA M AS L A DA NYI

pring is a time of sap stirring in
trees and ASAP (pronounced ay-sap
- meaning "as soon as possible") stirring in human beings.
But spring isn't just a season of
greatest vitality, it's a season of greatest
variety. It's a time of tulips and tornadoes, of blossoms and (in early spring)
blizzards. So let's explore three different
kinds of celestial sights that are unique
to spring skies.
The few but ﬁne 2nd-magnitude
stars of spring. The dearth of 2ndmagnitude stars in the traditional constellations of spring is really surprising.
At least, that's true if you don't include
the six 2nd-magnitude stars of the Big
Dipper (which, for many of us, are circumpolar) or stars too far south to see
well from around latitude 40° north. If
you do that, you ﬁnd that out of what
I count to be 71 stars between magnitude 1.5 and 2.5 in all the heavens,
only four of them are in the traditional
spring constellations.
You can probably think quickly of
the three 1st-magnitude stars of spring:
Arcturus, Spica, and Regulus. But what
are the four 2nd-magnitude luminaries?
They are Alpha (α) Hydrae (Alphard),
Gamma (γ) Leonis (Algieba), Beta
(β) Leonis (Denebola), and Alpha (α)
Coronae Borealis (Alphecca) - with
magnitudes of 1.99 (Alphard), 2.01
(Algieba), 2.14 (Denebola), and 2.22
(Alphecca). Delta (δ) Leonis (Zosma) at
magnitude 2.56 just misses being in this
category. But is Alphecca's constellation
Corona Borealis, the Northern Crown,
really a constellation of spring? Or does
it belong to early summer (Alphecca's
epoch J2000.0 RA is 15h 35m)? If Alphecca doesn't count, then spring's tally of
2nd-magnitude stars is only three.
Alphard, whose name means "the
solitary one," is the orange lonely heart
of Hydra, the Sea Serpent, and is in a

"Nothing is so beautiful as Spring -
When weeds, in wheels, shoot long and lovely and lush;
Thrush's eggs look little low heavens, and thrush
Through the echoing timber does so rinse and wring
The ear, it strikes like lightnings to hear him sing ..."
-Gerard Manley Hopkins, "Spring"

large, dimly starred region of the heavens. Algieba is one of our ﬁnest double
stars, its golden magnitude-2.2 and
-3.5 components currently 4.4″ apart.
Denebola marks the tail of Leo, though
the tuft used to be the big loose cluster
of Coma Berenices, Berenice's Hair. And
Alphecca, also known as Gemma, is
indeed the brightest gem in the semicircle of the Northern Crown.
Steep planets at nightfall in
springtime. Around the spring
equinox, the angle of the zodiac is
quite steep with respect to the western horizon at nightfall. This places
the Moon and the planets as high as
possible for a given elongation from
the Sun. Last spring, as it does every 8
years, Venus passed its maximum north
of the Sun (slightly more than 8°) at
inferior conjunction. Back in 2001 this
helped me see Venus with the naked
eye at both ends of one night - and see
the crescent Venus without magniﬁcation (through an eye-centered pinhole
to eliminate the diffraction spikes or
rays of Venus). Last year (2 × 8 = 16

years after 2001) I was able to see Venus
at both ends of the same day - this
required optical aid, though - and to
observe it in a small telescope shortly
before sunrise, virtually right at the
moment of inferior conjunction.
Best in spring: six out of six
amazing comets. I feel that a "great
comet" may be most basically deﬁned
as one of 2nd magnitude or brighter
when visible outside of twilight. If
so, then all four such comets for the
Northern Hemisphere in the past 50
years were best seen in March and
April: Comet Bennett in 1970, Comet
West in 1976, Comet Hyakutake in
1996, and Comet Hale-Bopp in 1997.
But my two other most fascinating
comets of the past 50 years have been
Comet Halley in March-May 1986 and
Comet IRAS-Araki-Alcock in May 1983,
the latter of which I'll discuss here in
next month's column.
¢ FRED SCHAAF lives on the edge of
the New Jersey Pinelands Reserve (with
no lights for about 10 miles to his east).
sk yandtelescope.com * A PR I L 2 018

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Sky and Telescope - April 2018

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