Looking toward Sagittarius, we face the center of the Milky Way Galaxy. With ordinary telescopes, we see lots of stars and dust. Visible light cannot penetrate all that dust, but radio waves can. Radio telescopes can see all the way to the galaxy’s core, revealing a black hole millions of times more massive than the sun, surrounded by arching magnetic fields.
Nearly the whole universe is invisible to the eye — only a tiny fraction shines in visible light. But instruments aboard spacecraft, in deserts and on mountains can extend our sight.
This month’s meeting of the Nevada County Astronomers Club features a slide show by Alan Stahler, looking at the universe in invisible colors (see his column in the Learning section of today’s The Union). The meeting is at 7 p.m. Wednesday in the community room of the Madelyn Helling Library. It’s free, and all ages are welcome. For information, call 530-274-2313.