I’m always excited when springtime is just around the corner. It’ll soon be time to get outdoors more and enjoy the warmth of our beautiful sun.
We all take our sun for granted, expecting it to be there every day, but ancient civilizations worshiped its light and heat because they recognized its life-giving properties.
Today we know they were right; life on Earth, and even the Earth itself, could never exist without our nearest star.
The sun appears large and bright because it’s nearby, only 93 million miles away.
Most people would consider that to be tremendously distant, but we astronomers recognize it as a mere stone’s throw on a cosmic scale.
The enormity of our sun is pretty remarkable too. The “photosphere” — the disk that we can see (with a proper solar filter, of course) — stretches about 865,000 miles from edge to edge. That’s large enough that 109 Earths could stretch across its face!
No wonder that we consider our sun to be immense. But, again, on a cosmic scale, is it?
Our sun is one of a class of stars known as “solar-type” stars; these comprise only about 7% of the Milky Way galaxy.
Most stars, however, are considerably smaller than the sun. These are known as “red dwarfs,” and they make up about 75% of our galaxy, so by comparison, our sun is huge.
But what about the other 18%? What type of stars are those?
Many of them are known as “giants” and “supergiants,” and two of the best examples of these are visible tonight in the constellation Orion.
Look for Orion as a vertical rectangle of stars midway up in the southern sky just after dark; at its center lie three equally bright stars that form a straight line.
Orion represents a hunter, with the top two stars marking his shoulders, the bottom two marking his knees, and the three central stars outlining his belt.
Many of the stars of Orion are giants and supergiants, but two are particularly spectacular.
The bright star marking the northeastern corner (one shoulder) of Orion is known as Betelgeuse. This red supergiant glows with an orange light that’s pretty tough to miss.
At the opposite corner (in one of the hunter’s knees) lies sparkling Rigel, another supergiant that displays a slightly bluish-white color.
Rigel lies about 850 lightyears (5,100 trillion miles) from Earth, contains about 21 times more mass, and has a diameter some 74 times greater than the sun.
Betelgeuse, on the other hand, makes Rigel appear small by comparison.
Some 15-20 times more massive than our sun, Betelgeuse is one of the first stars to have its size measured.
And it’s big. Very big. We would need about 700 suns to cross the face of Betelgeuse.
Betelgeuse is so immense that if it replaced our sun at the center of our planetary system, it would engulf not only the sun but the orbits of Mercury, Venus, Earth and Mars, and extend nearly to Jupiter!
For all its enormity, Betelgeuse isn’t the largest known star. That honor goes to UY Scuti, a red supergiant 30% larger than Betelgeuse!
