Lesson Two : Optical Astronomy
Optical astronomy is the study of the sky in visible wavelengths (4 - 7 × 10-11 m). When we look up at the night sky using tools like binoculars or telescopes to aid our eyes, we can see many different sorts of objects at visible wavelengths, like our own moon, many stars, some of the other planets in our solar system, their moons, our galaxy (the Milky Way), other galaxies, and stellar nebulae. These tools help us to get a much clearer view of the heavens than we could with just our naked eyes.
Astronomers use a variety of telescopes that range from hand held instruments to huge telescopes filling entire buildings to satellites in orbit. Some of the largest Earth-based optical telescopes are the twin Keck telescopes in Mauna Kea, Hawaii. The most famous satellite-based optical telescope is the Hubble Space Telescope, which has taken thousands of high-resolution images of objects throughout our galaxy and beyond. The advantage of launching optical instruments into space is that their images are not distorted by the Earth's atmosphere; therefore, we get clearer views of the objects we're looking at.
We can learn a lot about objects in our universe by studying them at visible wavelengths. We can determine their distances from Earth, their sizes, their temperatures, their motion through space, their chemical compositions, and many other properties.
The Center of the Milky Way
courtesy of David Talent, NOAO/AURA/NSF
Keck Telescopes on Mauna Kea
Jean-Charles Cuillandre and the W. M. Keck Observatory
Eagle Nebula (M16)
NASA, ESA, STScI, J. Hester and P. Scowen
