Lesson Summary
- Astronomers study light from distant objects.
- Light travels at 300,000,000 meters per second—faster than anything else in the uni-
verse. - A light-year is a unit of distance equal to the distance light travels in one year, 9.5
trillion kilometers. - When we see distant objects, we see them as they were in the past, because their light
has been traveling to us for many years. - Light is energy that travels as a wave.
- Visible light is part of the electromagnetic spectrum.
- Telescopes make distant objects appear both nearer and larger. You can see many
more stars through a telescope than with the unaided eye. - Optical telescopes are designed to collect visible light. The three main types of optical
telescopes are reflecting telescopes, refracting telescopes, and catadioptric telescopes. - Radio telescopes collect and focus radio waves from distant objects.
- Space telescopes are telescopes orbiting Earth. They can collect wavelengths of light
that are normally blocked by the atmosphere. - Galileo was the first person known to use a telescope to study the sky. His discoveries
helped change the way humans think about the universe. - Modern telescopes collect data that can be stored on a computer.
- A spectrometer produces a spectrum from starlight. Astronomers can learn a lot about
a star by studying its spectrum.
Review Questions
- Proxima Centauri is 4.22 light-years from Earth. Light travels 9.5 trillion kilometers
in one year. How far away is Proxima Centauri in kilometers? - Identify four regions of the electromagnetic spectrum that astronomers use when ob-
serving objects in space. - List the 3 main types of optical telescopes, and describe their differences.
- Explain the advantages of putting a telescope into orbit around Earth.
- Describe two observations that Galileo was the first to make with his telescope.
- List 3 things that an astronomer can learn about a star by studying its spectrum.
Further Reading / Supplemental Links