Before dawn on July 11, early risers will be treated to a striking celestial scene low in the east-northeast sky.
A slender waning crescent moon, softly glowing with earthshine, will appear to align with the orange light of Mars, the orange-red star Aldebaran, with the sparkling Pleiades and Hyades star clusters close by. Together, they will form a beautiful morning tableau in Taurus — one well worth setting an alarm to see.
First: the moon
Most obvious is, of course, the moon, appearing as a lovely waning crescent, 14% illuminated. It rises around 2:00 a.m. local daylight time and will likely appear as a thin arc of light enclosing a ghostly ball. Here is one of nature's beautiful sights and fits the old saying, "the old moon in the new moon's arms." Leonardo da Vinci (1452-1519) was the first to recognize it as earthshine. That faint bluish-gray light is light from Earth reflected toward the moon. Earth's light, of course, reflects sunlight, so earthshine is really sunlight that is reflected off Earth to the moon and reflected toward Earth.
Next: Mars
The second object is a planet: Mars. It will appear as an orange-yellow star roughly five degrees below and slightly to the right of the moon. Your clenched fist held at arm's length measures roughly 10 degrees in width, so Mars will hover roughly 'half a fist-width" below the lunar disk.
Mars rises around 2:40 a.m. local time and is about 15 degrees above the east-northeast horizon by dawn. So as the eastern sky begins to lighten up, Mars will be about "one and a half fist-widths" above the horizon.
It currently resides within the boundaries of the zodiacal constellation of Taurus the Bull. Mars remains rather inconspicuous, but its luminosity continues to increase as we gain on it in our smaller, faster orbit, though it is a very slow process. The planet moves from 17.5 light minutes away on July 1 to 15.4 light minutes by Sept. 1, brightening ever-so-slightly from magnitude +1.3 to +1.2. At its closest approach this coming February, Mars will be only 5.6 light minutes from Earth and will appear to shine fully 10 times brighter than it does now.
Finally: Aldebaran
Shining about 5.5 degrees below and slightly to the right of Mars will be a similarly hued, orange-red star, appearing to shine nearly twice as bright as the planet. That will be Aldebaran, marking the angry right eye of Taurus. Aldebaran is the fourteenth brightest star in the sky and lies 67 light-years from Earth. This is a red giant star, 45 times larger than our sun, 1.6 times more massive and over 400 times as luminous. Aldebaran is older and redder than the sun and is preparing to fuse its lightweight core into heavier elements, which are common among stars of its type. Aldebaran has a surface temperature of about 6,760 degrees F (3,738 degrees C). And Aldebaran is really a double star; its companion is much smaller and far dimmer, with an overall mass less than half that of the sun and only about one-third as large.
Incidentally, although it appears among them, Aldebaran is not actually a member of the V-shaped Hyades cluster. But it's much closer to us in space than the other Hyades stars, so it's simply an "innocent bystander," but nicely completes the V-shaped face of the Bull in our sky. Henry M. Neely (1879-1963), a long-time lecturer at New York's Hayden Planetarium, wrote in his book: A Primer for Stargazers:
"When Taurus is in the night sky, it is well worth the while of any stargazer to beg, borrow or steal a pair of binoculars. . . because the most dazzling of the stars are not visible to the naked eye. This is particularly true of the area inside the V of the Bull's face. Someday I hope an imaginative designer of jewelry will duplicate this superb setting of celestial gems, matching them in color, sparkle and design."
And completing this lovely early morning tableau, is the beautiful Pleiades star cluster. They'll glitter, as Tennyson imagined, "like a swarm of fireflies tangled in a silver braid." They'll sparkle about six degrees to the moon's upper right. Good binoculars will reveal a score of stars in this little group, while long-exposure observatory photographs show about 1000 in the area — all suffused in great clouds and streamers of nebulous light.
What a great way to start the second weekend of July!
So, rise before the first blush of dawn, seek out a clear east-northeast horizon, and let the morning sky reward your early vigil. With binoculars in hand, linger a little longer among the Pleiades and the nearby celestial jewels—an ancient sparkle waiting quietly above the waking world.
If you're looking for a telescope or binoculars to observe the night sky, our guides for the best binocular deals and the best telescope deals can help. Our best cameras for astrophotography and best lenses for astrophotography can help you get ready to capture the next stunning skywatching event.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, Sky and Telescope, The Old Farmer's Almanac and other publications.