Orange Triplets

Stars come in all types. One of the most common types is the orange dwarf — which is also one of the hardest to see. Orange dwarfs are somewhat smaller and cooler than the Sun. And they’re not quite as bright, which is why so few are visible to the unaided eye. Tonight, though, you can see not one, not two, but three orange dwarfs all at once.

This triple star is known as 36 Ophiuchi. It’s just 19 light-years from Earth. Its two brightest stars each emit about a quarter as much visible light as the Sun does. The two stars orbit each other every 500 years, on a highly elongated path. Yet another orange star stands a good distance away from these two, giving 36 Ophiuchi a grand total of three orange dwarf stars.

Such stars account for about 10 percent of all the stars in the galaxy. They’re so faint, though, that none is prominent in the night sky. Fortunately, because 36 Ophiuchi is so close, it’s one of the few orange dwarfs you can see without binoculars or a telescope.

You will, however, need a star chart and a good, dark, moonless night, like tonight, away from city lights. 36 Ophiuchi is quite low in the south-southeast at nightfall, and due south around midnight, not far to the lower right of the bright planet Saturn. And if you can’t get away from the city, binoculars will bring the system into view — a triple orange dwarf that’s among our nearest neighboring stars.


Script by Ken Croswell, Copyright 2016

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