Depth 23 · Binary star

Sirius

Sirius, the Dog Star, is the brightest star in the night sky, a hot white star paired with a faint white dwarf called Sirius B. Sirius B packs about the Sun's mass into a body smaller than Earth, which made it a key test case for the physics of dead stars.

Fact sheet

Type: Binary star (A-type main-sequence star and white dwarf)
Distance: About 8.6 light-years from the Sun
Size: Sirius A is about 1.7 times the Sun's radius and about twice its mass; Sirius B has about the Sun's mass in a body slightly smaller than Earth
Constellation: Canis Major
Position in the sky: Right ascension 6h 45m, declination −16° 43′
Seeing it from Earth: Easy to see with the naked eye from almost anywhere on Earth as the brightest star of the night, best in the evening sky during northern winter (southern summer); Sirius B is very hard to spot even with a good telescope because of A's glare.
On the voyage: Depth 23, in the Nearby stars section of the route, between Barnard's Star and Vega

Things to know

In 1844 Friedrich Bessel noticed that Sirius wobbles as it moves and concluded it must have an unseen companion; Alvan Graham Clark and his father, Alvan Clark, finally saw Sirius B through a telescope in 1862. arXiv
The two stars orbit each other about once every 50 years, and Sirius B is roughly 10,000 times fainter than Sirius A in visible light. NASA
Hubble weighed Sirius B by measuring how its strong gravity stretches its light toward redder wavelengths, an effect predicted by Einstein, and found about 98% of the Sun's mass. ESA
Sirius B is only about 12,000 kilometres across, so the gravity at its surface is hundreds of thousands of times stronger than on Earth. ESA
In X-ray light the roles flip: the hot white dwarf Sirius B outshines its much bigger partner. NASA Chandra

Sources

Reach depth 23 on a voyage to fly past Sirius yourself. Every right answer warps your ship one stop deeper.

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