Sirius: The Brightest Star Explained – Facts, Location & How to See It
Look up tonight and spot the brightest star in the night sky — Sirius! This stunning star outshines all others and is easy to find if you know where to look. The quickest way to find Sirius from your location is to use the free Sky Tonight app. Keep reading to discover fascinating facts about this star and learn why it appears so bright in our sky!
Contents
- Sirius star system facts
- How to find Sirius in the sky?
- Where is Sirius tonight?
- Why is Sirius the brightest star?
- Why does Sirius twinkle so much?
- What is the common name for the star Sirius?
- Sirius’ constellation: Canis Major
- Sirius from Canis Major: bottom line
Sirius star system facts
- Official names: Sirius, α Canis Majoris, α CMa
- Catalog designations: 9 Canis Majoris, HD 48915, HR 2491, HIP 32349
- Constellation: Canis Major
- Distance from the Earth: 8.6 light-years
- Rotation period: ~50 years
- Star type: binary star
Sirius is not just one star but a star system with two stars: Sirius A, the brightest star in our night sky, and Sirius B, a faint white dwarf. They orbit a common center of mass, staying about 20 AU (astronomical units) apart. For reference, that’s about the same distance between the Sun and Uranus.
The only star you can see with the naked eye is Sirius A. So when people say "Sirius", they usually mean Sirius A.
Sirius B is 10,000 times dimmer than Sirius A! It's so faint that astronomers couldn't measure its size and mass until 2005, when they got enough data with the help of the Hubble Space Telescope.
Sirius A: The Main Star
- Right ascension: 06h 45m 08.917s
- Declination: −16° 42′ 58.02″
- Apparent magnitude: -1.46
- Mass: 2 solar masses
- Luminosity: 24.7 L
- Radius: 1.7 solar radius
- Surface temperature: 9,845 K
Sirius B: The Companion Star
- Right ascension: 06h 45m 09.0s
- Declination: −16° 43′ 06″
- Apparent magnitude: 8.44
- Mass: 1 solar masses
- Luminosity: 0.02 L
- Radius: 0.008 solar radius
- Surface temperature: 25,000 K
How to find Sirius in the sky?
From December to mid-May, look for Sirius in the evening after sunset. If you are in the Northern Hemisphere, you’ll find it in the southeastern sky. In the Southern Hemisphere, look northeast.
Use Orion’s Belt to find Sirius
A simple way to locate Sirius is to use Orion’s Belt — the three bright stars in a row. Draw an imaginary line through them, and you’ll reach Sirius. It’s about eight times farther from the Belt than the Belt's width.
Use an app to find Sirius instantly
The easiest way to find Sirius is with the Sky Tonight app. Open the app, tap the magnifier icon, and type "Sirius" in the search bar. Then tap the target icon to see Sirius on the sky map. Point your device at the sky and follow the white arrow to see where Sirius is in the sky right now.
Where is Sirius tonight?
Sirius is part of the Canis Major constellation. If you want to know its exact position tonight from your location, check the free Sky Tonight app.
- Sirius is visible from almost everywhere except north of 73° N.
- Sirius never sets below the horizon south of 73° S.
- In some cities, it stays low in the sky — for example, in Helsinki, Finland, it reaches only 13° above the horizon.
When can I see Sirius?
The visibility of Sirius varies throughout the year depending on your location.
In the Northern Hemisphere:
- Late November – mid-May: evening & night visibility 🌙
- Mid-May – mid-August: rises above the horizon only during the day* ☀️
- Mid-August – September: morning visibility 🌅
- October – November: morning & night visibility 🌙🌅
In the Southern Hemisphere:
- Mid-November – February: visible all night 🌙 (evening, night & morning)
- March – April: evening & night visibility 🌙
- April – late June: evening visibility 🌆
- Late June – early July: evening & morning visibility 🌆🌅
- Mid-July – mid-August: morning visibility 🌅
- Mid-August – early November: night & morning visibility 🌙🌅
*Sirius is bright enough to be seen in the daylight, but you must know exactly where to look for the star. Also, clean, haze-free sky is a must.
Why is Sirius the brightest star?
Sirius shines so brightly because it is:
- Very close to Earth — only 8.6 light-years away.
- Extremely luminous — about 25 times brighter than the Sun.
There are brighter stars than Sirius in terms of actual energy and light output, but they are much farther away, so they appear dimmer.
In our sky, only the Sun, Moon, Venus, Jupiter, Mars, and sometimes Mercury outshine Sirius. Of all the stars, Sirius is the most brilliant star in the night sky, and it outshines its closest competitor, Canopus, by almost twice as much!
Why does Sirius twinkle so much?
Sirius is famous for exhibiting flashes of intense color as it twinkles. This is because the Northern Hemisphere observers usually see the star positioned low in the sky so that its very bright light is passing through a thicker blanket of air. The pockets of turbulence in our atmosphere that makes stars twinkle also work like tiny refracting prisms — splitting apart Sirius’ white light and randomly sending different colors (wavelengths) to our eyes.
Other stars twinkle too, but this effect is especially noticeable with Sirius because it is so bright.
Fun fact: This twinkling effect helps observers tell the difference between stars and planets! Unlike stars, planets shine with a steadier light because they are closer to Earth and have a larger apparent size.
Want to know more ways to tell stars from planets? Check out our Stars VS Planets infographic.
What is the color of Sirius?
Sirius A, the brightest star in the Sirius binary system, has a white to blue-white color in space. However, when seen from Earth, it often appears to twinkle in many colors — which is why some call it a rainbow star.
What is the common name for the star Sirius?
Sirius’ name means “searing” or “scorching” in Greek. It’s also commonly known as the Dog Star because it is the brightest star in the constellation Canis Major, which means the Big Dog in Latin.
Another Sirius name (that you probably hear less often) is Alpha Canis Majoris. Usually, the brightest star of any constellation is designated so.
Sirius’ constellation: Canis Major
Canis Major, the constellation where Sirius is located, is not very large, but it has an interesting star pattern. The dog’s head is shaped like a small triangle of medium-bright stars. However, these stars are faint and can be hard to see in bright city skies.
From nose to tail, Canis Major stretches about 19° across the sky — roughly the width of two fists held at arm’s length. From ears to paws, the constellation spans about one fist in height.
The rest of the dog’s body is made up of brighter and more noticeable stars. Let’s take a closer look at them! The descriptions below are based on how they appear from mid-northern latitudes.
What are the major stars in Canis Major?
Below Sirius shines the bright star Wezen, which marks the dog’s “bottom.” The tip of the dog’s tail, marked by a modest star named Aludra, is in the lower left of Wezen. Above Wezen, you’ll find two less conspicuous stars positioned side-by-side and separated by two finger widths. They nicely denote the dog’s slim torso. The left-hand star is whitish Al Zara (HR 2580). To the right is fainter and orange-tinted star Udra (HR 2653). Both stars are designated Omicron Canis Majoris.
To the lower right of Wezen, a bright star named Adhara represents the dog’s rear legs. Some representations include two dimmer stars for the rear paws.
The dog’s front legs are formed by the bright star Beta Canis Majoris (Mirzam) located to the lower right of Sirius. Beta Canis Majoris is 60 times more luminous than Sirius. If that star were located where Sirius is, instead of 500 light-years away from us, it would appear 15 times brighter than Venus!
Deep-sky Objects in Canis Major
In the heart of Canis Major, below Sirius, is a bright little cluster of stars designated Messier 41, sometimes called the Little Beehive Cluster. Binoculars should show it easily. The cluster, which is about 2300 light-years away from us, consists of several brighter golden stars and numerous fainter ones.
Another nice cluster named NGC 2354 sits on the upper left of Wezen. An even nicer cluster sits to the left of Wezen. It’s formally known as the Tau Canis Majoris Cluster (NGC 2362), and also the Mexican Jumping Star and Pirate’s Jewels Cluster.
A bright little nebula with an unusual shape is located on the upper left of Sirius. NGC 2359 is aglow with a mixture of reddish light from ionized hydrogen and some blue light scattered by interstellar dust. “Wings” of gas flanking the main zone have given it the nick-names Thor’s Helmet, the Duck Nebula, and the Flying Eye Nebula.
Sirius from Canis Major: bottom line
Sirius is the brightest star in the night sky, but it’s not just one star — it’s a binary star system! It consists of Sirius A, a bright main-sequence star, and Sirius B, a faint white dwarf. Sirius appears to twinkle in many colors — this effect is caused by Earth's atmosphere. Its brightness and flickering make it stand out among other stars. Want to find Sirius easily? Use the free Sky Tonight app and start your stargazing journey!
We wish you clear skies and happy stargazing!
