Mars shines red next to blue Spica at sunset on Sept. 13

Mars will shine close to the blue star Spica at sunset on Sept. 13, but you'll need a clear view of the western horizon to catch the colorful duo before they slip swiftly out of view.

Look west as the sun sets and you'll find Mars less than 10 degrees above the summer horizon, with Spica shining to its lower left with the stars of the constellation Virgo. If you're new to navigating the night sky, it's useful to remember that the width of your clenched fist held at arm's length equates to roughly 10 degrees, while the span of your middle three fingers measures approximately 5 degrees of sky.

Both Mars and Spica will set below the horizon a little over an hour after the sun, so try to find an elevated spot with a clear view of the western horizon to catch the colorful cosmic pair before they disappear.

The point of light that we call Spica is in reality a binary star system composed of two magnificent stellar bodies with a combined luminosity more than 12,000 times brighter than our sun. It is the brightest jewel in the constellation Virgo, yet at a distance of 250 light-years from our solar system, its blue-white sparkle doesn't even rank amongst the top 10 brightest stellar bodies that are visible from Earth's northern hemisphere.

Mars, meanwhile, owes its famous red hue to an oxidation process that rusts iron minerals present in the martian rocks, soil and dust. The coming weeks will see the red planet become increasingly hard to spot as it draws closer to the sun in Earth's evening sky. The trend will continue in the runup to the Red Planet's solar conjunction in January 2026, when the rocky world will cross behind the sun from our perspective, to emerge weeks later as a bright red morning star in the predawn sky.

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