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Watch Mars and Saturn race toward star Antares in Earth’s sky

Mars and Saturn race toward star Antares in September 2014 Read more

Tonight for September 6, 2014

The view of the evening planets from Perth, Australia. Unlike at mid-northern latitudes, the planet Mercury and the star Spica are visible at nightfall.

The view of the evening planets from Perth, Australia. Unlike at mid-northern latitudes, the planet Mercury and the star Spica are visible at nightfall.

The view of the evening planets from mid-northern latitudes on September 27, 2014

The view of the evening planets from mid-northern latitudes on September 27, 2014

The view of the evening planets from the Southern Hemisphere on September 27, 2014

The view of the evening planets from the Southern Hemisphere on September 27, 2014

From northerly latitudes, look low in the southwest sky at nightfall to see the planet Mars in between the planet Saturn and Antares, the brightest star of the constellation Scorpius the Scorpion. We draw in the ecliptic – the Earth’s orbital plane projected onto the stars of the Zodiac- because the planets are always found on or near the ecliptic. In September 2014, the planets Mars and Saturn can be seen racing toward the star Antares, on the sky’s dome. It’s a race Mars is bound to win. Read on.

For Southern Hemisphere viewers. You also see the planet Mars in between the planet Saturn and the star Antares after darkness falls on these September 2014 evenings. However, the ecliptic intersects the horizon almost vertically at nightfall from Earth’s southerly latitudes, so the Southern Hemisphere sees these evening planets (and the stars Zubenelgenubi and Antares) much higher in the sky as darkness falls than we see them in the Northern Hemisphere. In fact, there’s even a good chance of catching the planet Mercury and the star Spica from southerly latitudes.

No matter where you live worldwide … watch the great race of the planets in the southwest or western sky throughout September 2014. Mars and Saturn are both heading eastward, or in the general direction of the star Antares. Both will catch up to Antares in 2014, but Mars will do so much sooner than Saturn.

Why? Because Mars is closer to the sun than Saturn and hence moves faster – both in its orbit around the sun and also on the dome of Earth’s sky. Mars and Saturn are called superior planets because they orbit the sun outside of Earth’s orbit. The more distant the planet, the more slowly it goes around the sun. Mars, at a relatively close 1.52 astronomical units from the sun, has an orbital velocity of 24.1 kilometers (15 miles) per second. Contrast Mars’ orbital velocity with that of distant Saturn, which at 9.5 astronomical units from the sun has an orbital velocity of 9.7 kilometers (6 miles) per second.

And that’s only part of the story. Saturn’s orbital distance is well over six times greater than Mars’.

Adding all this together, it takes Mars some 1.88 Earth-years to go full circle in front of the constellations of the Zodiac, whereas it takes Saturn nearly 29.5 Earth-years. So it shouldn’t come as too much surprise to watch Mars leave Saturn in the dust on the dome of Earth’s sky – and encounter the star Antares soon on our sky’s dome – over the weeks ahead.

Start observing tonight, September 6, 2014. In the weeks ahead, you’ll see Mars move quickly eastward in front of the background stars of the Zodiac, while slow-plodding Saturn goes at a snail’s pace.

Mars has its rendezvous on our sky’s dome with Antares on September 27, 2014. Meanwhile, Saturn won’t meet up with Antares until December 2015.

Bottom line: Start observing – September 6, 2014 – as Mars and Saturn both move toward the star Antares on our sky’s dome. Mars will quickly move eastward in front of the background stars of the Zodiac, while slow-plodding Saturn goes at a snail’s pace. Mars has its rendezvous with Antares on September 27, 2014, while Saturn won’t meet up with Antares until December 2015.

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