Highlights: 145 CMa- winter albireo?
When: late evenings throughout January
What’s special: Perceiving any colour, let alone vivid hues, when deep-sky observing is not common,
so the sight of a colourful double star is one to be savoured. Lurking within radiant Sirius’ stamping
ground is the colourful double star 145 Canis Majoris (CMa, HIP 35210, magnitude +4.8), offering
up through a small telescope superbly contrasting yellow-orange and bluish-white components that
are easily separated. It’s so good that it has received the popular moniker of the ‘Winter Albireo’
(Southern Albireo from the Southern Hemisphere), in recognition of its likeness to wonderful beta
Cygni, the true Albireo in Cygnus.
How to observe: A small telescope can easily split the magnitude +5 yellow-orange primary from
the magnitude +5.8 blue-white companion lying 26.8 arcseconds away to the north-east (position
angle 52 degrees). is optical double (a line-of-sight effect rather than a true binary) is also known
as Herschel (h) 3945, one of more than 5,500 double stars that were catalogued by John Herschel,
William’s son, in the early 1800s.
From UK shores, Canis Major, whose territory is located to the southeast of Orion, is somewhat
altitude challenged, yielding a limited observing window around culmination as a result. e Winter
Albireo (lying around 10 degrees south-east of Sirius) peaks at around 15 degrees at about 11.40pm
GMT from London at around mid-month.
The Winter Albireo is the apt nickname bestowed on 145 Canis Majoris -20° 2 17 (h3945), a marvellously coloured double star.
145 CMa (h3945) has the splendid popular name the ‘Winter κ Albireo’. It’s located in Canis Major, a southern constellation lying
south-east of Orion that hosts dazzling Sirius.
ViewHighlights: 145 CMa- winter albir...
January 2021
Astronomy Now