star light, star bright...
If you spend some time looking at the stars, you’ll notice that some seem brighter than others. Astronomers describe how bright stars are using a number and the word magnitude. Magnitude is a way to measure and compare levels of brightness. The magnitude scale starts with negative numbers and goes up into positive numbers. The lower the number, the brighter the star.
The brightest visible star (other than the sun) is called Sirius. Sirius is nearly at magnitude -1 (magnitude -1.47, actually). To compare, the brightness of a full moon is nearly magnitude -13 (magnitude -12.5, at the brightest) and the brightness of the Sun is nearly magnitude -27 (magnitude -26.74). That’s quite a difference.
At times of the year when you can see the constellation Orion, you can usually see Sirius. The three diagonal stars in the middle of Orion--called Orion's belt--point to Sirius. Imagine a diagonal line extending from Orion's belt. Sirius will be the brightest star on that line.
In an urban neighborhood, the dimmest stars you are able to see without a telescope or binoculars are magnitude +3 or +4. In a remote place, with clear skies and otherwise good conditions, you may be able to see stars as dim as magnitude 6 without using a telescope or binoculars.
In an urban neighborhood, the dimmest stars you are able to see without a telescope or binoculars are magnitude +3 or +4. In a remote place, with clear skies and otherwise good conditions, you may be able to see stars as dim as magnitude 6 without using a telescope or binoculars.
The image above shows differences in magnitude and in light pollution. The bright stars on the left side are practically glowing. These are the stars that make up the constellation Orion. Notice all of the stars around the constellation that you can see.
On the right side, all of the stars are much dimmer. This is because light pollution from a city blocks the starlight. You can still see some of the bright stars. The stars in Orion are still there, but they look like tiny dots.
The brightest stars in Orion are Rigel, at almost magnitude 0, and Betelgeuse, at about magnitude 1. Rigel is in the bottom right corner, and Betelgeuse is in the top left. The three belt stars are all about magnitude 2.
On the right side, all of the stars are much dimmer. This is because light pollution from a city blocks the starlight. You can still see some of the bright stars. The stars in Orion are still there, but they look like tiny dots.
The brightest stars in Orion are Rigel, at almost magnitude 0, and Betelgeuse, at about magnitude 1. Rigel is in the bottom right corner, and Betelgeuse is in the top left. The three belt stars are all about magnitude 2.
diamonds in the sky
You may have noticed something else about the stars in Orion--they seem to be different colors. Betelgeuse stands out as a gold or light orange color. Stars shine in a variety of colors. Some are reddish, some are greenish, some are bluish, and some are yellowish, like our Sun. A star’s color shows how hot it is. Bluish stars are the hottest, and reddish stars are the coolest. The Sun’s heat is somewhere in the middle.
Amateur astronomer George O. Pitcovich wrote a poem comparing stars to gemstones.
Amateur astronomer George O. Pitcovich wrote a poem comparing stars to gemstones.
The Sky
by George O. Pitcovich
The Sky’s my treasure chest,
It’s there that I store
Diamonds and sapphires,
Emeralds galore
Rubies of red, jades of green
Topaz and opal, iridescent sheen
Gems of all color,
Jewels of all hue,
This treasure’s all mine,
But I’ll share it with you.
--Courtesy of Dan Heim, http://heimhenge.com/skylights/
by George O. Pitcovich
The Sky’s my treasure chest,
It’s there that I store
Diamonds and sapphires,
Emeralds galore
Rubies of red, jades of green
Topaz and opal, iridescent sheen
Gems of all color,
Jewels of all hue,
This treasure’s all mine,
But I’ll share it with you.
--Courtesy of Dan Heim, http://heimhenge.com/skylights/
What do you think about the stars? Do they look like gemstones or something else?
The next chance you get, go outside at night and look up. How many stars can you see? How many different star colors can you see?
The next chance you get, go outside at night and look up. How many stars can you see? How many different star colors can you see?