This recent photo of the center of the Milky Way was made in the dust-penetrating light of X-rays and infrared (heat energy) light combined. The white patch is home to a massive black hole at the very center of the galaxy. Radiation and winds from stars crowded in the core create the wild filaments of dust (left). The blue haze is gas heated to millions of degrees by material expelled from around the black hole as well as explosions from supernovas and massive stars. The galaxy’s center is crowded place humming with activity. Credit: NASA, ESA, SSC, CXC, and STScI
Antimatter. Antipasto. Antihero. Antibiotic. And then you’ve got your anticenter. Of the galaxy that is. Who gives much thought to this place in the Milky Way 180 degrees opposite the center? It’s easier to focus instead on the galaxy’s hub, home to a black hole four million times more massive than the sun, thousands of sardine-packed stars and much vibrant activity. Even though that’s all but hidden from view behind dark clouds of interstellar dust in the constellation Sagittarius, scientists monitor the galaxy’s flickering, arrhythmic heart with telescopes sensitive to infrared and other forms of light that can bust through the dust.
The summer Milky Way widens in the direction of the galaxy’s center in Sagittarius. Click on this excellent interactive photo exhibit to see pictures of our galaxy taken in many types of light. Photo: Bob King
As seen from mid-northern latitudes, Sagittarius is low in the southern sky during mid-summer. When we gaze in its direction we look through our Milky Way’s flattened disk toward the center or galactic bulge. Though the core itself is invisible to ordinary vision, the stars stack up over the 20,000 light separating us from the center and form a thick glowing band — the Milky Way — that spans the sky on summer evenings.
Look away from Sagittarius toward the horns of Taurus to face the Milky Way’s anticenter. Created with Stellarium.
In contrast, the anticenter is directly opposite Sagittarius in the direction of Auriga the Charioteer and very near the star El Nath that defines the tip of Taurus the Bull’s northern horn. Direct your gaze toward the bull’s horns and you’ll quickly find yourself in the Milky Way’s countryside. The bright lights and busy intersections of the galactic metropolis are now far behind you. Not much going on here. True, you’re looking through 25,000 light years of galaxy, but things thin out as you approach the edge and you soon find yourself teetering on the starless emptiness of intergalactic space.
While the hazy band of the Milky Way is still visible through Auriga and Taurus, it’s thin and anemic compared to summer’s billowy star clouds. Imagine your viewpoint from a planet orbiting a star at the anticenter. During the part of the year when you’d face back toward the galaxy’s center, the sky would be filled with stars, but for the remainder of the year you’d face a nearly starless sky as you looked across the enormous chasm of space separating the Milky Way from the galaxies beyond. You might even feel a touch of vertigo as you stood there at the edge of the abyss.
This is an artist’s depiction of what our galaxy would look like if you could see it from the outside. The sun is in the flat disk about halfway from center to edge. Each of the spiral arms has its own name, and I’ve added the locations of the center and anticenter. The entire Milky Way galaxy is about 100,000 light years across and contains some 400 billion stars, numerous star clusters, nebulas and planets. Credit: NASA/CXC/M.Weiss
Recent research has shown that there are at least four faint star clusters lined up in the neighborhood of the anticenter. As we learned yesterday, Taurus has a fine array of clusters for both naked eye and binoculars and Auriga even more. The Milky Way provides an assortment of goodies no matter what direction you look.
Just a heads up this weekend. The annual Geminid meteor shower will reach maximum on Sunday night-Monday morning December 13-14 with up to 140 meteors per hour expected. It could well prove to be the best shower of the year. I’ll provide more information about the event later in the week. Cross your fingers for clear skies.
Plan on being awake tomorrow at dawn? If so, take a gander to the east at the thick crescent moon as shown here around 6 a.m. Thursday. The moon will pass about a fist below the planet Saturn. Joining them will be Virgo’s brightest star Spica and Arcturus in Bootes. The space station will pass below the moon at 5:31 a.m. Created with Stellarium.