Ask Me Everything

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a star on two scales.

hich star ines the ightest?

The Sun is by far the brightest star in Earth’s sky. The next-brightest star is Sirius, sometimes called the Dog Star, in the constellation ot Canis Major. Sirius is 12.5 billion times fainter than the Sun, but that is because it is much farther away—it is actually twice as big and 25 times brighter.

Measuring

scales

Astronomers measure the brightness of

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The first, called apparent magnitude,

gives the brightness of a star seen from Earth.

The second, absolute magnitude, is a

Inside the Sun, a tug of war is going on. The Sun’s gravity pulls gas in, but the pressure of the Sun’s core tries to push it out. The gravity and pressure balance each other out, so the Sun keeps its spherical shape.

measure of the star’s real brightness (its luminosity) and compares the stars as if they were the same distance from Earth.

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Ten brightest stars from Earth

Sun

Sirius

Canopus

Rigil

Kentaurus

Arcturus

6.    Vega

7.    Capella

8.    Rigel

9.    Procyon 10. Achernar

FAST FACTS

The Sun

01: The Sun has shone for around 4.6 billion years and will continue to shine for around another five billion years.

02: It is a huge bali of glowing gas: around 75% hydrogen,

25% helium, and tiny amounts of around 90 other elements.

03: At the Sun’s core, the temperaturę is 27 million °

(15 million °C), but the surface is a cooler 9,900°F (5,500°C).

04: When seen in ultraviolet light (right), the Sun appears deep orange.

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