While you won’t see the barrage of colors you’ll find in a fireworks show, there are tinges of red, white and blue in our July night skies.
We don’t see bright color in the stars, or even planets, for two reasons.
First of all, planets in our solar system are millions and millions of miles away; the stars — while much, much larger than the planets — are trillions and trillions of miles away. Not much of that light reaches our eyes. When it does, Earth’s atmosphere also partially obscures that faint light, even with clear skies.
The second reason we don’t see intense color is because of how our eyes coordinate with our brain. We can only process so much light at a time. If we could accumulate light like DSL cameras we would see much more color in the stars. That’s why you see much more color in astrophotography images.
There is red to see in the sky this month, compliments of Mars beaming away in the southeastern evening sky. It’s still fairly close to Earth at just over 55 million miles away. Not far from Mars is the moderately bright star Antares in the constellation Scorpius. In fact, the name Antares means “rival of Mars.” The red we see on 4,200-mile-wide Mars is because of an abundance of iron oxide on the surface. The red we see on Antares is because the star is a 6,000 F, 760 million-mile-wide ball of hydrogen gas. This gigantic star is a comparatively cooler star, giving it a ruddy hue. Antares is also a lot farther away than Mars, at more than 600 light-years. One light-year equals nearly 6 trillion miles. Other cooler stars like Antares also glow red.
By the way, the planet Saturn is just to the left of Mars. It isn’t red, but it’s a heck of a telescope target even if you have a small telescope. It’s my favorite planet outside of Earth.
Another reddish and cooler star in the July evening skies is Arcturus, the brightest actual star in our night sky right now. It’s shining high in the southwestern evening and is the brightest star in the constellation Bootes, in mythology a farmer hunting the nearby constellation Ursa Major, the Big Bear. It’s much easier to see it as a giant kite with Arcturus at the tail.
In the eastern heavens there’s a good example of a star with a bluish tinge to it. It’s Vega, the second brightest star in our summer skies. It sports a slight blue hue because it’s one of the hotter stars in our part of the Milky Way galaxy, with a surface temperature of about 17,000 F. By comparison, our sun is about 10,000 F. Vega is part of the “Summer Triangle,” made up of three stars: the brightest in each of their respective constellations. You can’t miss them. They’re the brightest stars in the eastern half of the sky right now. Vega is in a faint constellation called Lyra the Harp. Good luck seeing it as that.
Enjoy the red, white, and blue in our July summer skies and have a great 4th of July.
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