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'Summer Triangle' reveals solar system's eventual destination

Near the border of the constellations Lyra and Hercules is the solar apex, the spot in space toward which our solar system is moving.
BY WAYNE HARRIS-WYRICK, For The Oklahoman Published: September 2, 2014

Go outside at 10 tonight and look straight up. Find the three bright stars that make a triangle in the center of the sky. These three stars, Vega, the western-most, Altair, the southern-most, and Deneb, the eastern-most, make a pattern commonly called the Summer Triangle. Vega, the brightest of the trio, marks the handle of Lyra, the harp. A line drawn from Deneb to Vega and extended that same distance ends in the constellation Hercules, the great hero of Greek mythology.

Move straight south from Vega by the width of one fist plus a finger held at arm’s length. That spot, near the Lyra-Hercules border, is the solar apex, the spot in space toward which our solar system is moving.

Everything in our Milky Way orbits the center of the galaxy. As with any other orbital motion, like Earth around the sun, galactic orbits aren’t perfectly circular. Our orbital speed around galactic central point is 137 miles per second, or 492,100 miles per hour. At that speed, it takes us some 250 million years to make one complete galactic orbit. Stars in the same part of the galaxy orbit at roughly the same speed, but not exactly.

The deviation of the sun’s orbit from the average of the stars around us is 36,910 miles per hour, and it is at that speed that we fly toward the solar apex.

If you really want to know where you’re headed, go out tonight and look straight out of our planet’s “front windshield,” south of Vega near the Lyra-Hercules border.

The planets Mars and Saturn have been relatively close together in our evening sky for weeks. Mars, being closer, appears to move faster than does more distant Saturn.

The planets generally move eastward relative to the background stars in their orbits. Since last May, when both Saturn and Mars showed up in our night sky, Mars was west of Saturn. Over the past three months, Mars has been moving east faster than Saturn and on Wednesday, Mars passed Saturn in the constellation of Libra.

At 8 p.m. Sept. 28, with Mars now in Scorpius and Saturn still in Libra, the moon will move to a spot in Libra half way between Saturn and Mars, making an interesting visual pattern low in the southwestern sky.

In addition to these three, Vesta and Ceres, the two brightest asteroids, will be close to Saturn. Vesta and Ceres are the targets of study for NASA’s Dawn spacecraft.

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