We point our telescopes at just about any point in the sky, and wonders emerge: planets and their moons, asteroids and comets, galaxies, nebulae, supernovae, quasars – myriad fascinating objects to inspire ruminations that run the gamut from trivial to profound. Gazing at the images that are released, our curiosity about our place in the Universe grows.
In terms of cosmic “geography,” our home planet orbits a star that is located in a minor arm of the Milky Way called the Orion Spur (or one of several other names) about 27,000 light years from the center of the galaxy.
In this relatively uncluttered neighborhood, we have plenty of elbow room. The nearest stars in our vicinity – a three-star system collectively called Alpha Centauri – are a full 4.3 light years away. The next closest is Barnard’s Star, almost 6 light years distant. What is striking is the vast emptiness of interstellar space.
When the Hubble Space Telescope is aimed at the center of the Milky Way, however, things seem a lot more crowded. A recent image posted by NASA/ESA pictures the incredible density of stars and interstellar dust that obscure the supermassive black hole lurking at the galaxy’s center. In the Milky Way nuclear star cluster, there are billions of stars packed together. If the space between the Sun and Alpha Centauri were as densely populated as the galactic core, as many as a million stars would fit – and there would be still be space between them.
The Hubble image uses infrared wavelengths to reveal structures and objects behind the clouds of dust that would otherwise be invisible. The blue stars in the foreground lie between us and the nuclear star cluster. The red ones shine from behind or within the dust. The very darkest structures we see are clouds of dust so dense that even the space telescope’s infrared vision cannot penetrate them. Behind it all, invisible to us, the supermassive black hole at the galaxy’s nucleus devours whatever drifts too close, swallowing even the light.
Our pre-industrial ancestors were struck with awe by the Milky Way pouring across the night sky. Once we turned the lights on here on Earth, we began to lose the galaxy’s nourishing light. Fortunately, though, over time – and especially in the past few decades – instruments of increasing power and sophistication have been produced to pierce the veil and invite us again, well . . . to see the light.