This Week’s Sky at a Glance, July 3 – 11
This is the time of year when the two brightest stars of summer, Arcturus and Vega, are equally high overhead at dusk. Arcturus is toward the southwest, Vega is toward the east.
Arcturus and Vega are 37 and 25 light-years away, respectively. They represent the two commonest types of naked-eye stars: a yellow-orange K giant and a white A main-sequence star. They’re 150 and 50 times brighter than the Sun, respectively — which, combined with their nearness, is why they dominate the high evening sky.
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