The 10 Brightest Stars
By Pedro Braganca
Special to
posted: 07:00 am ET
15 July 2003

The ten brightest stars on the Celestial Sphere

Each star is an individual with its own personality. Thousands are visible on any clear night far removed from city lights. Together, with the faint glow of myriad others, the tapestry of the celestial sphere is fashioned.

Stars come in different colors, sizes, shapes and ages. One trait that makes a star unique is its brightness.

Below: The Brightest Star

Astronomers measure the brightness of a celestial object according to a system originally devised by Hipparchus in 120 B.C. Hipparchus ranked the brightness of stars in the sky on a scale of 1 to 6 as seen from the Earth. The brightest stars he could see were classified as first magnitude and the faintest were sixth magnitude.

Centuries later we still use the magnitude scale of Hipparchus, although it has since been modernized.

The magnitude scale is logarithmic; one magnitude difference is equal to a brightness difference of about 2.5 times. So a magnitude 1 star is about 100 times brighter than a magnitude 5 star. The brighter planets and stars have negative magnitudes. The Sun, being the brightest object in the sky, has a magnitude of 26, followed by the full Moon at magnitude 11. Objects with a magnitude of 6 or less can be seen without optical aid under ideal observing conditions away from all local lighting.

The following is a catalog of the ten brightest stars that grace the celestial sphere, an imaginary projection of Earth into space. All the stars are drawn on the inside of this sphere, even though stars of course exist in space at varying distances. As on Earth, the celestial sphere is split into northern and southern halfs, called hemispheres.

As seen from our corner of the galaxy, these are lighthouses of the heavens and can be enjoyed even from the heart of metropolitan areas.


The Lick Observatory's 3-meter telescope reveals the faint companion of Sirius A.

Terms & Definitions

Luminosity: The intrinsic brightness of a star -- as it would appear if you orbiting it -- compared to the Sun. The Sun's luminosity is 1. Sirius has a luminosity of 23 and Betelgeuse 55, 000.

Magnitude: A logarithmic brightness scale; the difference between magnitude 1 and magnitude 5 is 100 fold. The larger the magnitude, the fainter the object. The lower the magnitude, the brighter the object. The brightest stars have negative magnitudes.

Brightness: A measure of a star's magnitude or brightness as seen from the Earth. Brightness is dependent on luminosity and distance.

Degrees: The separation between two points of light on the celestial sphere is measured in degrees. A closed fist held at arms length is about 10 degrees while a finger would be 1 degree or two moon widths.

Pedro Brananca is an astronomy support associate at Starry Night.

1. Sirius

All stars shine but none do it like Sirius, the brightest star in the night sky. Aptly named, Sirius comes from the Greek word Seirius, meaning, "searing" or "scorching." Blazing at a visual magnitude of -1.42, it is twice as bright as any other star in our sky.

Sirius resides in the constellation Canis Major, the Big Dog, and is commonly called the Dog Star. In ancient Greek times the dawn rising of Sirius marked the hottest part of summer. This is the origin of the phrase "dog days of summer."

Because of Earths 26,000 year precession cycle, in which the planet's axis slowly wobbles due to the gravitational attraction of the Sun and Moon on the Earths equatorial bulge, Sirius no longer marks the hottest part of summer, rising later in the year. Precession gradually changes the location of stars on the celestial sphere.

Sirius is best seen at a favorable time during the winter months for northern hemisphere observers. To find the Dog Star, use the constellation of Orion as a guide. Follow the three belt stars -- obvious targets even for casual skywatchers -- 20 degrees southeast to the brightest star in the sky. Your fist at arm's length covers about 10 degrees of sky.

Sirius, the red giant star Betelgeuse, and Procyon in Canis Minor form a popular asterism known as the Winter Triangle.

Intrinsically, Sirius is 23 times more luminous and about twice the mass and diameter of the Sun. Of course its farther away from Earth than the Sun. But not too far, cosmically speaking. At a mere 8.5 light-years away, Sirius seems so bright in part because it is fifth closest star to the Sun.

The brilliance of Sirius illuminates not only our night skies, but also our comprehension of them. While observing it in 1718, Edmund Halley, of comet Halley fame, discovered that stars move in relation to one another a principle now known as proper motion.

In 1844, German astronomer Friedrich Bessel observed that Sirius had a wobble, as if being tugged by a companion. While testing his new 18.5-inch lens in 1862 (the largest refracting telescope in the world at that time), Alvan Clark solved this mystery by discovering that Sirius was not one star but two; the first compact stellar remnant had been discovered, and it would prove to be a pioneer of what would be later referred to as a whole class of white dwarf stars.

The companion, dubbed Sirius B, has the mass of the Sun in a package as small as the Earth, having collapsed after depleting its hydrogen. A single cubic inch of matter from this companion star would weigh 2.25 tons on Earth. At magnitude 8.5, it is 1/400th as luminous as the Sun. The brighter and larger companion is now known as Sirius A. [Sirius Map]

[Map Sirius from your location with Starry Night Software]

Use the navigation below to learn about the other brightest stars.

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