ESO image of galaxy NGC 6744. Credit: ESO
Of all the galaxies in the Universe that we have pictures of, from early photos taken through big ground-based telescopes to the stunningly detailed and far-reaching eye of the Hubble Space Telescope, the one we actually need an artist to paint us a picture of is the one closest to home: our own Milky Way. We’re simply too close to it, and can’t see the forest for the trees….
So what does it actually look like? Good question. It’s the closest galaxy to us—meaning, we’re inside it—but we have better pictures of galaxies billions of light years away than we do of our own home.
The Milky Way is known to be a “barred spiral” galaxy, with a dense, elongated central core with an uncertain number of spiral arms pinned to it. It is thought to be about 100,000 light years across, and contain between 100 and 400 billion stars. This fuzzy picture of the Milky Way is put together from observations of the stars we see around us, near and far, and lanes of dust and gas that cloud our view along the galactic plane. We’re not sure how the spiral arms of stars, dust, and gas are laid out, or exactly what the overall central core looks like, because most of it is beyond our direct view—much like trying to draw a map of a city by viewing it from inside a single neighborhood.
But, an image of the galaxy NGC 6744, recently released by the European Southern Observatory, may supply us with a photographic example of what the good ol’ Milky Way looks like from the outside, for it possesses many of the same characteristics—other than being twice the diameter.
NGC 6744, about 30 million light years away in the constellation Pavo, has spiral arms surrounding an elongated and dense core set inside a dusty disk. It even has a small companion galaxy similar to the irregular “satellite” galaxies that accompany the Milky Way: the Magellanic Clouds. Peer into this looking glass, or this twin’s face, and you may be looking at the best picture of our home galaxy we’ll ever see….
Where did the Milky Way get its name, anyway? It’s certainly more poetic than “NGC 6744” (which means the 6744th entry in the New General Catalog). If you’ve ever seen the ghostly, cloud-like smear arcing across a dark night sky—the combined light from stars in our galaxy too distant to see as individuals—you can probably guess the answer. It looks “milky.” In Greek mythology, the whitish band was the spilt mother’s milk of the goddess Hera. In fact, the word “galaxy” itself comes from the Greek name for the Milky Way: “galaxias,” meaning “milky circle.”
Recent discoveries make what we see in the image of NGC 6744, or what we see of the Milky Way in the night sky, only a phantom of what’s really there. Not only are galaxies believed to consist of 90% “dark matter“—matter that we cannot detect by observing light—we now estimate there to be at least 50 billion planets in the Milky Way, 500 million of them located within the “habitable zone”: the right distance from their star for liquid water to exist. And now there is even evidence for up to twice as many “free floating” planets (planets not orbiting stars) as star-bound ones!
Just makes me hungry for the next amazing discovery….