Springtime Skies: Spring ushers in special sights of stars, planets, and more.
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 2nd-magnitude 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[degrees] 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 (a) Hydrae (Alphard), Gamma (y) Leonis (Algieba), Beta ([beta]) Leonis (Denebola), and Alpha (a) Coronae Borealis (Alphecca)--with magnitudes of 1.99 (Alphard), 2.01 (Algieba), 2.14 (Denebola), and 2.22 (Alphecca). Delta (O) 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 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[degrees]) 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 x 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).
"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"
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|Title Annotation:||Under the Stars|
|Publication:||Sky & Telescope|
|Date:||Apr 1, 2018|
|Previous Article:||Planetary Almanac.|
|Next Article:||Mars, Saturn, and the Teapot: Early in the month, the two planets congregate by the Teapot; by the end of the month, Mars slips away from Saturn.|