The night sky has fascinated humans for centuries, with people incorporating its myriad of twinkling stars into various navigation methods, cultural traditions, religious movements, and more. Of these stars, a few stand out to viewers here on Earth as the largest and brightest. But which is the brightest star in the sky?
The answer, it turns out, isn’t simple. Because of the Earth’s rotation and tilt on its axis, the brightest star in the sky depends on which hemisphere — northern or southern — you live in and what season you’re experiencing. That’s because the night sky changes throughout the year, so a star’s position and the times it rises and sets all affect how bright you see it.
That said, the intrinsic brightness of a star does not change based on an observer’s location. Astronomers use a magnitude scale to measure the brightness of stars, with lower numbers indicating brighter stars. This measurement remains constant regardless of whether the star is prominently visible in your region.
To clarify all this, we’ll discuss the brightest stars and tell you when they are most visible in the Northern or Southern Hemisphere.
Sirius: Winter (Northern Hemisphere), Summer (Southern Hemisphere)
As far as astronomers are concerned, Sirius is objectively the brightest star visible from Earth (apart from the sun, of course). To measure the brightness of stars, they use a magnitude scale, with lower numbers indicating brighter stars. Sirius has a magnitude of -1.46, a lower magnitude than any other star in the night sky.
From mid-December to February, Sirius dominates the night sky. These months correspond to winter in the Northern Hemisphere and summer in the Southern Hemisphere.
Because Sirius is located in the constellation Canis Major (the Great Dog), it is also known as the “Dog Star.” At only 8.7 light years away, Sirius is not only the brightest star, but also the closest star to Earth (again, after the Sun).
How to recognize Sirius
Sirius is visible in both hemispheres for several months of the year, but is most prominent from December through February.
To find Sirius in the Northern Hemisphere, look toward the southern horizon in the early evening during the winter months. If you can find Canis Major, it will be the brightest star in that constellation.
In the southern hemisphere, Sirius can be seen high above us during the summer months.
Canopus: Winter to Spring (Southern Hemisphere)
By late spring, Sirius is no longer visible in the Southern Hemisphere, having come too close to the Sun from our perspective on Earth. This sunset of Sirius allows for a new star to put on a show in the Southern Hemisphere: Canopus.
Located in the constellation Carina (a Latin term for the keel of a ship), Canopus is visible in the southern sky in late summer and fall. At magnitude -0.74, it is the second-brightest star astronomers have ever measured.
How to recognize Canopus
During the spring and summer months in the Southern Hemisphere, Canopus can be seen high in the sky.
If you are in the Northern Hemisphere, Canopus is only visible on the horizon from the lowest latitudes. The best time to look is February.
Alpha Centauri: All year round (southern hemisphere)
Sirius may be the closest star to Earth (again, after the Sun), but Alpha Centauri is the closest star system to Earth, at just 4.37 light-years away. It is actually made up of three stars: Rigil Kentaurus, Toliman, and Proxima Centauri.
Alpha Centauri is located in the constellation Centaurus (the Centaur) and has an apparent magnitude of -0.1, making it the third-brightest star in the sky.
How to Spot Alpha Centauri
In most of the Southern Hemisphere, Alpha Centauri never sets, meaning you can see it on almost any clear night. Look for the configuration known as the Southern Cross. The crossbar points the way to a bright, yellowish star, Alpha Centauri.
The galaxy is not visible from most of the Northern Hemisphere, but if you’re in the southernmost regions it will appear as a bright point of light near the horizon.
Arcturus: Spring (Northern Hemisphere)
Arcturus is a bright red giant in the constellation Bootes (from the Greek word for “shepherd”). What makes this star special is that there are no other notable bright stars near it in the night sky.
The fourth brightest star, Arcturus (and its magnitude -0.05) is easily visible throughout most of the Northern Hemisphere throughout the year. It is most prominent between March and May and glows orange-red.
How to recognize Arcturus
In the Northern Hemisphere, first find the constellation Ursa Major: the stem points directly toward Arcturus.
Arcturus is also visible in the Southern Hemisphere, but only in spring and summer.
Vega: Summer (Northern Hemisphere)
As summer arrives in the Northern Hemisphere, Vega takes center stage. It is one of the brightest stars in the sky, measuring a magnitude of 0.03. Summer is the best time to view it, although it is technically visible year-round in the Northern Hemisphere.
Vega belongs to a famous trio of bright stars: Astronomers have named Vega, Altair, and Deneb (all three of which belong to different constellations) the Summer Triangle.
Vega is located in Lyra (the constellation Lyre or Harp) and is about 25 light-years from Earth.
How to recognize Vega
To see the star Vega in the Northern Hemisphere, look toward the northeast in mid-evening in May or directly overhead after sunset in July.
In the Southern Hemisphere, Vega may be difficult to observe, as it doesn’t reach its highest point until 3 or 4 a.m. If you can stay up that late to catch a glimpse, May is the best month.
Capella: Winter (Northern Hemisphere)
Visible from late August to mid-June in the Northern Hemisphere, Capella is most noticeable in winter, when the bright star is prominent in the night sky. At magnitude 0.08, it is the sixth-brightest star astronomers have measured and is part of the constellation Auriga, or the Charioteer.
Capella is special because it is not really a single star, but a quadruple star system, with two red giants. To viewers on Earth, the star appears as twinkling flashes of red, green, and blue light as it rises or sets above the horizon.
How to recognize Capella
In the Northern Hemisphere, Capella can be found in the northeast in the early evening, from mid-October through March.
In most of the Southern Hemisphere, Capella is not visible at all.
Rigel: Winter (Northern Hemisphere), Summer (Southern Hemisphere)
Rigel is one of the brightest stars in the night sky and is located in the constellation Orion. With an apparent magnitude of 0.13, it is the seventh brightest star in the sky.
Astronomers classify Rigel as a blue supergiant. It is extremely hot and luminous—about 10,000 times brighter than our sun—which is why it still appears so bright to viewers on Earth, despite being 863 light-years away.
If you can find Orion in the night sky, you can also find Rigel. Rigel represents Orion’s right leg and shines blue-white.
How to recognize Rigel
In the Northern Hemisphere, you can spot Orion and Rigel in the east in summer just before sunrise, but it’s a more spectacular sight on winter nights, when it’s high in the southern sky.
In the Southern Hemisphere, Rigel is visible high on summer nights. In January and February, it is visible as soon as the sun has set.
We created this article using AI technology and then fact-checked and edited it by an editor from HowStuffWorks.
Original Article: What’s the Brightest Star in the Sky? Depends on the Season
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