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Mars stops the show – Part 1




This month, the planet Mars emerges from its role as celestial understudy to Jupiter—and becomes a showstopper in its own right.

Scan the eastern sky at mid-evening, to see what I mean: Mars is now a truly regal apparition. It rises nightly with a dazzling retinue that includes golden-hued Saturn and the red supergiant, Antares.

The trio form a glittering triangle, set in the upper-left foreground of the luxuriant Scorpius constellation—reputedly, the second most magnificent of the 88 official star-groups, after Orion.

As with Orion, Scorpius has a striking configuration that makes it very easy to locate—a bent-fishhook (or curved “J”) pattern. Its richly varied array of brilliant blue, white and red stars also helps.

Like Orion as well, Scorpius is a seasonal marker. But whereas the mythical Hunter signifies sunny, comparatively dry conditions, Scorpius is a rainy season constellation.

Reddish-orange Mars, the triangle’s peak, shines brighter than any other object. Second, is the gas giant Saturn, radiating golden yellow, from the left angle of the base, with crimson Antares to its right.

Keep in mind, that most patterns in the night sky are merely visual effects. The objects appear to be spatially related, because they lie in our line of sight. (In some cases though, they do share proximity.)

Antares, for instance, has no spatial relationship whatsoever, to either Mars or Saturn—except in the celestial lore of the ancient Romans, who imagined the red star as a “rival” of their War God, Mars.

Mars and Saturn are sister satellites to Earth—and the fourth and sixth planets from the Sun. They orbit at average distances of 225 million km (Mars) and 1.4 billion km (Saturn).

By contrast, Antares—the 16th brightest star in the sky—is more than 600 light years away. (A light year, is the distance a photon travels in 12 months, at 300,000 km per second: About 10 trillion km!).

What makes the supergiant visible to us, at this distance, is size, not proximity: The diameter of Antares is 700 times that of the Sun (which is 1.4 million km)!

Something else that distinguishes Antares (and the other stars in Scorpius) from Mars and Saturn is the source of its light.

Antares generates energy through nuclear fusion, while its two triangle-companions reflect light from the Sun.

This is an important distinction, because the apparent brightness of Mars and Saturn will diminish or increase, over the next few months, as their orbital position changes—while that of Antares will not.

Known colloquially as “The Red Planet,” Mars is a comparatively small world, with only 11 percent of Earth’s mass: Not to speak of Saturn, which is 95 times more massive than our planet.

Yet Mars is currently outshining both Saturn and Jupiter and will, scientists predict, become much more luminous in the days ahead.

The apparent size of the Martian disc, and hence its brightness, started to increase January 13th and will peak on the 30th of this month. It’ll then start getting dimmer, bottoming out on December 20th.

Astronomers attribute these changes in luminosity to the orbital motion of Mars and corresponding alterations in its proximity to Earth and the Sun.

These variations, Universe Today notes, arise from the structure of the Martian orbit, which it described as “markedly eccentric”.

In astronomy, “eccentricity” is the extent to which a planet’s orbit around the Sun deviates from a circle. The paths of all planets deviate to some extent, and are thus said to be elliptical.

To be continued.

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