Skywatch for the week of May 15, 2023
Mon May 15, 2023 BERENICE'S HAIR
The Big Dipper is in our northern sky this evening. To the south of the dipper’s handle are some faint stars that form the constellation of Coma Berenices, or Berenice's Hair. This strange constellation is based on a true story. Berenice was the wife of one of the Ptolemies of Egypt. Just before a great battle, she promised to cut off her hair and offer it to the gods if Ptolemy should win. He did, and she did. Then somebody stole the hair from the temple - a classic case of hair today and gone tomorrow! Ptolemy was angry; he grabbed his men by the head and shoulders and told them to comb the palace until they found the hair; some of them tried to give him the brush-off, but one man made up a bald-faced lie when he pointed to this part of the sky and declared that Berenice’s hair had risen up to the heavens to commemorate the occasion. So as a result, Berenice's Hair is now a permanent constellation, all because of some great hair-raising battle from long ago.
Tue May 16, 2023 HOWLING COYOTE
An old Navajo story tells how the stars came to be. Altse’ Hastiin, the first man, asked all the animals to gather up the bright shining stones along the river. They carried those stones up into the sky where they became stars. They put them in patterns which would show the people which creatures had set those stars in place. Now the small animals could not carry many stars and Great Spirit asked Coyote to take a bag of stones to help them complete their pictures. But Coyote soon grew tired, and he flung the stones across the sky, scattering them, and making a jumble of the pictures. Then Coyote was sorry, because he had forgotten to put his own picture up in the heavens. And that, say the Navajo, is why the Coyote howls at night.
Wed May 17, 2023 GREAT GALAXY!
In the evening in the summer, or in the fall, or the winter, when the sky is clear and dark, the Milky Way can be seen as a faint band of cloudy light that stretches across the heavens. But in the springtime evening, the Milky Way hugs the horizon in all directions, completely encircling it, and it can be lost in the glow of streetlights. The Milky Way is our home galaxy, and we are inside it. But which is bigger – the Milky Way galaxy or our solar system? Solar systems are billions of miles in diameter, but the disc of our Milky Way is roughly 600 thousand trillion miles across – much bigger, and what’s more, it contains hundreds of billions of solar systems. All of the stars you see up there are part of our Milky Way – great galaxy!
Thu May 18, 2023 THE SUN AND THE SOLAR YEAR
Over the course of a year, the sun drifts eastward against the background of stars. It’s a very slow motion caused not by earth’s rotation, but by its revolution about the sun, which displaces the sun’s position by about 1 degree of angle a day – that’s less than the width of your little finger at arm’s length! After roughly 365 days, the sun returns to where it had been exactly a year ago. Today the sun appears below the Pleiades star cluster in the constellation Taurus. Next month it will be in Gemini, the month after that in Cancer, then Leo, and so on until next May 18th, when it will be alongside the Pleiades again. This defines the solar year as the amount of time needed for the sun to go full circle, once around the zodiac in the heavens.
Fri May 19, 2023 ARCTURUS THE INTRUDER
In the eastern sky this evening there is a star that doesn’t belong here – an intruder. It’s Arcturus, the fourth brightest star in our night sky. Most of the stars you see are moving along with our sun, traveling in nearly circular orbits about the hub of our Milky Way galaxy, but Arcturus, an old red giant star, moves at a sharp angle to all the others, plunging along an elliptical path through the disc from up above. Tonight, it’s a mere 37 light years away, that’s a bit more than 200 trillion miles, but in a half million years or so it will have shot down below us, and its ever-increasing distance will make it too dim to see without a telescope. So, enjoy viewing Arcturus while it’s still in the neighborhood!