Astronomy

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Dazzling double stars, open clusters,

nebulae, and even a galaxy will highlight

your summer of viewing the night sky.

by Stephen James O’Meara

CYGNUS THE SWAN wings its way

down the River Milky Way with three of the

largest and most conspicuous cosmic show-

pieces north of the celestial equator: the Great

Rift, the Northern Coalsack, and the North

America Nebula. When viewed under a dark

country sky, this trio of dark and bright naked-

eye splendors instills a sense of balance, a visual

reminder of sorts that every day has its night.

Cygnus also contains a rich assortment of tele-

scopic gems, many incorporating this natural

theme of darkness and light, that run the gamut

from an enormous supernova remnant to the

site of an infinitely small black hole candidate.

A choice selection follows.

Pairing off

We’ll begin with one of the most treasured

double stars in the night sky: Albireo (Beta [β]

Cygni), which combines a 3rd-magnitude pri-

mary and a 5th-magnitude companion. To the

unaided eye, this star appears solitary, but even a

2.4-inch scope can split it into a colorful pair of

celestial jewels 34" apart. Albireo A shines with a

golden hue, while its companion has an emerald-

blue light.

Now test your visual perception on a fainter

pairing of similar colors about 30' northeast of

25 Cygni. Known as h1470 Cygni, this pretty

double star sports a magnitude 7.5 golden pri-

mary with a magnitude 9 companion 29" to the

north-northwest. The pair shares the same low-

power field with a striking, 30'-long curve of four

similar double stars first noticed by Astronomy

columnist Glenn Chaple in the mid-1970s and

subsequently known as Chaple’s Arc. In the

DEEP-SKY

IN CYGNUS

Observe

Albireo (Beta [β] Cygni),

one of the most beautiful

double stars in the sky,

consists of a brilliant yellow

sun and its bluish companion.

ALAN TOUGH