As darkness falls on June 6, 2014, it’ll be hard to miss the bright starlike object close to the moon. That “star” is actually Mars, the fourth planet outward from the sun. As Earth spins eastward on its rotational axis tonight, the moon and Mars will appear to move westward across the sky. These two worlds – the moon and Mars – will set in the west in the wee hours after midnight.
Mars was brighter a few months ago, around the time our Earth passed between it and the sun on April 8. It’s still respectably bright now, though, and you’ll have no trouble picking it out in the moon’s glare.
Astronomers of old were quite confused by the varying brightness of the planet Mars. Sometimes Mars can outshine the giant planet Jupiter, which is usually the fourth-brightest celestial body to light up heavens, after the sun, moon and the planet Venus. At its brightest, Mars beams about 75 times more brilliantly than when it’s at its faintest. At its faintest, Mars exhibits about the same brightness as the star Mirfak in the constellation Perseus the Hero.
Bird’s-eye view of inner solar system in early June 2014
At one time, Earth was thought to lie at the center of the universe, and Mars’ change in brightness was a big mystery. The innovative astronomer Copernicus (1473 – 1543) suggested that the puzzle of Mars’ variable brightness could be solved by presuming that both Mars and Earth revolve around a central sun. Copernicus explained that when Earth – in its faster, smaller orbit – passes between Mars and sun, Earth swings closest to Mars. At such times, Mars appears brightest in Earth’s sky. Copernicus correctly computed Mars’ mean distance from the sun at 1.52 times the Earth’s distance from the sun. Astronomers use the term astronomical unit (AU) to refer to the sun/Earth distance: approximately 150,000,000 kilometers or 93,000,000 miles
We emphasize that the 1.52 astronomical-unit figure represents Mars’ mean distance from the sun. Because Mars has such an eccentric – oblong – orbit, this world can get as close as 1.38 AU or as far as 1.67 AU from the sun. That means Mars orbital distance varies by about 0.29 AU (45 million kilometers or 28 million miles). In contrast, Earth’s distance only varies by about 5 million kilometers or 3 million miles in our planet’s nearly circular orbit around the sun. Click here to view a cool animation of Earth’s and Mars’ orbits around the sun.
On June 6, 2014, Mars resides 1.56 AU from the sun and 0.83 AU from the Earth. That places Mars well over 300 times the distance of the June 6 moon, which lies about 391 thousand kilometers or 243 thousand miles away!
Bottom line: The bright object near the moon on June 6, 2014 is the planet Mars. This post explains why Mars is sometimes bright, and sometimes faint, in our sky.