Sirius Disappears

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Sirius Disappears

The brightest star in the night sky is getting ready to leave it for a while. Sirius, the Dog Star, is low in the southwest as night falls. Over the next few weeks, it’ll sink deeper into the twilight, then disappear from view.

Sirius is almost nine light-years away. And it actually consists of two stars, not one. The one we see is a good bit bigger, brighter, and heavier than the Sun. The other is about the same mass as the Sun, but a whole lot smaller — only as big as Earth.

That star is a white dwarf. It’s the crushed core of a star that originally was more massive than its companion. Because of those extra pounds, the star aged more quickly. It puffed up to giant proportions. When it could no longer produce energy in its core, it cast off its outer layers, leaving only the dead core. The white dwarf is so small and faint that it’s visible only through a telescope.

The bright star of Sirius eventually will suffer the same fate. And so will the Sun — but not for several billion years.

Sirius will return to view — in the morning sky — in August, with the exact date depending on your location. From ancient Egypt, it disappeared for about 70 days. Sirius was important in both religious and secular life. So 70 days became the length of time set aside to prepare a dead king’s body for the afterlife. And the star’s reappearance marked the start of a new year — in a calendar regulated by the Dog Star.

Script by Damond Benningfield

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