sial new model of the universe. According to Copernicus’s model, Earth and the other
planets revolve around the Sun. In Galileo’s time, most people believed that the Sun and
planets revolved around Earth. Galileo’s observations provided direct evidence to support
Copernicus’ model.
Observations with Modern Telescopes
Today, equipped with no more than a good pair of binoculars, you can see all of the things
Galileo saw, and more. You can even see sunspots, but you need special filters on the lenses
to protect your eyes. Never look directly at the Sun without using the proper filters! With
a basic telescope like those used by many amateur astronomers, you can also see polar caps
on Mars, the rings of Saturn, and bands in the atmosphere of Jupiter.
We now know that all of these objects are within our solar system. You can also see many
timesmorestarswithatelescopethanwithoutatelescope. However, starsseeninatelescope
still look like single points of light. Because they are so far away, stars continue to appear
as points of light in even the most powerful professional telescopes.Figure23.14shows one
rare exception.
Today, very few professional astronomers look directly through the eyepiece of a telescope.
Instead, they attach sophisticated instruments to telescopes. These instruments capture and
process the light from a telescope, and astronomers then look at the images or data shown
on these instruments. Most of the time, the instruments then pass the data on to a computer
where the data can be stored for later use. It can take an astronomer weeks or months to
analyze all the data collected from just a single night!
Aspectrometerisatoolthatastronomerscommonlyusetostudythelightfromatelescope.
A spectrometer uses a prism or other device to break light down into its component colors.
ThisproducesaspectrumliketheoneshowninFigure23.15. Thedarklinesinthespectrum
of light from a star are caused by gases in the outer atmosphere of the star absorbing light.
This spectrum can be observed directly, captured on film, or stored digitally on a computer.
From a single spectrum of a star, an astronomer can tell:
- How hot the star is (by the relative brightness of different colors).
- What elements the star contains (by the pattern of dark lines).
- Whether and how fast the star is moving toward or away from Earth (by how far the
dark lines are shifted from their normal positions).
Using telescopes, astronomers can also learn how stars evolve, what kind of matter is found
throughout the universe, and how it is distributed, and even how the universe might have
formed.