---
title: "Sirius: facts, distance and size – Krillion Space"
description: "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. With sourced facts."
url: https://krilion.app/atlas/sirius
language: en-US
---

# Sirius

Binary star. Depth 23 on the Krillion Space voyage, in the Nearby stars.

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.

![Sirius at depth 23 in Krillion Space, painted by the game (an illustration, not a photograph).](https://krilion.app/assets/atlas/sirius.webp)

## 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](https://arxiv.org/abs/1703.10625))
- 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](https://science.nasa.gov/asset/hubble/the-dog-star-sirius-and-its-tiny-companion/))
- 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](https://www.esa.int/Science_Exploration/Space_Science/Weighing_the_Dog_Star_s_companion))
- 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](https://www.esa.int/Science_Exploration/Space_Science/Weighing_the_Dog_Star_s_companion))
- In X-ray light the roles flip: the hot white dwarf Sirius B outshines its much bigger partner. ([NASA Chandra](https://chandra.harvard.edu/photo/2000/0065/))

## Sources

- [NASA Science (Hubble) – The Dog Star, Sirius, and its Tiny Companion](https://science.nasa.gov/asset/hubble/the-dog-star-sirius-and-its-tiny-companion/)
- [ESA – 'Weighing' the Dog Star's companion](https://www.esa.int/Science_Exploration/Space_Science/Weighing_the_Dog_Star_s_companion)
- [Chandra X-ray Observatory – Sirius A & B](https://chandra.harvard.edu/photo/2000/0065/)
- [Bond et al. 2017, ApJ – The Sirius System and its Astrophysical Puzzles (arXiv)](https://arxiv.org/abs/1703.10625)

## On the route

- Previous landmark: [Barnard's Star](https://krilion.app/atlas/barnards-star)
- Next landmark: [Vega](https://krilion.app/atlas/vega)
- [The whole Star Atlas](https://krilion.app/atlas)
- [Fly the voyage yourself](https://krilion.app/d/): every right answer warps your ship one stop deeper.