Summer’s best weekend: Worth looking up

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Time for easy astronomy – loveliness that soothes the soul but require no charts, no knowledge. It’s right now, the next clear night.

The Moon is absent. Skies are dark and starry. All you need is a clear, open spot away from the lights of town: any meadow, cemetery, lakeside, hilltop. Figure between 9 and 10 p.m.

First look straight up. A single bright star hovers at the zenith. That’s Vega (say VEE-ga)

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Most of the galaxy’s stars are nameless. Only one ten-thousandth of one percent have been identified. These mostly possess license-platelike designations such as HDE226464. A mere hundred bear actual names still in use, like Zubenelgenubi or Rasalhague. A mere handful are brilliant and have well-known names. Of those, just one floats directly overhead at this time of year. So Vega – which boasts the shortest star name of all – is a cinch to identify.

Vega was pronounced “wega” until the 19th century, and is spelled that way in some old astronomy books. It derives from the Arabic, meaning a falling eagle. It was also an eagle to the ancient Indians, and a vulture to the Egyptians: always a bird.

Shining at a steady magnitude zero, Vega served as the “standard candle” used by the worldwide astronomical community to calibrate the brightness of everything else in the universe. Like the French bar of platinum once used to define the meter, Vega was the sky’s reference point for the magnitude system. It’s an ideal choice, because it displays no flickering or variability, despite years of controversy about this. Moreover, it’s a single star like the Sun, instead of a binary like so many others.

Vega spins crazily in 12 hours, compared to a month for our own Sun, despite being three times larger. If it rotated just 18 percent faster it would break apart. Moreover, its pole of rotation is pointed straight toward us, give or take a few degrees. This means that any Vegans looking skyward would see our Sun as its North Star!

Twelve thousand years from now, we’ll return the favor. Vega periodically becomes our own polestar as Earth’s axis wobbles through its 26-millennium precession.

Vega was the very first star to be photographed. This feat was attained at the exact midpoint of the 19th century. As if this weren’t enough to keep us interested, Vega marks the approximate direction toward which we travel in space. As our entire starry neighborhood participates in the galaxy’s grand rotation, we do a little nine-mile-per-second sideslip in Vega’s direction. It’s heading our way.

Now that your eyes have gotten dark-adapted by staring straight up at Vega, you’ll see the Milky Way splaying across the entire sky. This is when it’s best-positioned. Far from artificial lights, it’s gorgeous. It’s one of the reasons I take a group to Chile each year: for skies like these, and the wonders that they contain. (See https://specialinteresttours.net.)

Now follow the Milky Way south. Here, about a third of the way up the southern horizon, is the galaxy’s center, which is straight overhead from Chile. This is the spot around which we – and all the other stars of the night sky – revolve every 240 million years: the pivot point. The center of all sensible motion.

Also lowish in the south, to the right of the Milky Way, you’ll see the bright orange star Antares marking the heart of Scorpius. If you have a truly unobstructed southern view, you can go left from Antares to trace out the entire scorpion and see why, along with Orion, it’s the finest of the 88 constellations. Far to Antares’ right are two bright stars, one above the other: The lower is orange Mars, the other is Saturn.

Vega, the Milky Way, Antares, Scorpius, Mars and Saturn: all easy to find – and so lovely, during this optimum stargazing week of summer.

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