Frequently Asked Questions About Astronomy
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What Do Astronomers Do?
In general, astronomers seek an understanding of how the
Universe works; from the planets in our own Solar System,
to the evolution of stars and nebulae, to whole systems of galaxies,
to the properties and fate of the Universe as a whole. Modern
astronomy is an interdisciplinary science that relies upon, and
furthers the development of, fields such as physics, chemistry,
computer science, and mathematics.
Unfortunately, only the very nearest astronomical objects (all
within our Solar System) can be reached by spacecraft in a reasonable
amount of time. Information about all other objects comes indirectly
from earth-bound telescopes or earth-orbiting satellites, which
observe light emitted or reflected from such objects. The collection
and detailed analysis of this light is key to unlocking the mysteries
of the observable Universe. The purpose of a telescope is to collect
this light; it is the role of the astronomer to analyze and interpret
these data in terms of physical theory.
What kinds of light come from astronomical objects?
In our everyday human experience, we see that light has measurable
properties. It has intensity (brightness), and it has color. The
intensity gives an indication of the number of light "waves"
or "particles" (called photons) coming from an object.
The color is a measure of the energy contained in each photon.
The colors of the rainbow (red, orange, yellow, green, blue, violet)
denote the energies of light waves that our human eyes can see
and interpret. This "color" or "energy" range
is called the visible spectrum. Red photons of light have the
least energy, violet photons carry the most energy. Until fairly
recently, all of our astronomical knowledge came from the detailed
study of visible light from astronomical objects.
Notice that radio, TV, and microwave signals are all light
waves; they simply lie at energies that your eye doesn't respond
to. On the other end of the scale, beware the high energy UV,
x-ray, and gamma-ray photons! Each one carries a lot of energy
compared to their visible- and radio-wave brethren. They're the
reasons you should wear sunblock in the summer, for example.
When we look at the Universe in light of different energies,
we probe different kinds of physical conditions -- and we can
see new kinds of objects! For example, high-energy gamma-ray
and X-ray telescopes tend to see the most energetic dynamos in
the cosmos, such as active galaxies, the remnants from massive
dying stars, accretion of matter around black holes, and so forth.
Visible light telescopes best probe light produced by stars (it's
no accident that human eyes have adapted to be sensitive to "ROYGBIV"
light like they are -- after all, that's where most of the Sun's
energy comes out). Going to even lower energies and longer wavelengths,
infrared and microwave radio telescopes best probe dark, cool,
obscured structures in the Universe: dusty star-forming regions,
dark cold molecular clouds, the primordial radiation emitted by
the formation of the Universe shortly after the Big Bang. Only
through studying astronomical objects at many different wavelengths
are astronomers able to piece together a coherent, comprehensive
picture of how the Universe works!
Popular myths about research astronomers:
 Astronomers only work at night
Well, some certainly do -- but you'll find that most astronomers
keep similar hours to the rest of the world. Astronomers who study
the Universe in visible light must do so at night, but infrared
and radio astronomers (and those who observe using satellite-based
telescopes like the Hubble Space
Telescope) can observe happily during daytime hours as well.
But even steadfast night-owl observers tend to snap back to normal
daylight hours when not on the mountain.
In fact, a large subset of astronomers don't observe or use
telescopes at all! Theoretical
astrophysicsts try to understand the Universe from the viewpoint
of physical theory. In this framework, observations exist to constrain
analytical theories and numerical models of how astronomical objects
behave. Mathematics and computers are the language and tools of
the astronomical theorist, just as telescopes and computers are
for the observational astronomer. And many problem-oriented astronomers
operate in both theoretical and observational arenas.
Astronomers "look" through telescopes
only with their eyes
Once upon a time, the human eye was the only astronomical detector.
In the late 19th century came photographic film... but even that
has been replaced almost entirely by electronic detectors.
Another point to consider is that "visible" light
is only a fraction of the light emitted from astronomical objects.
For these other regimes (gamma-ray, x-ray, UV, infrared, radio),
other detectors are needed. In fact, the development of electronic
"eyes" sensitive to other kinds of light is a research
pursuit of many personnel at Steward Observatory!
And even in visible light, the human eye is horribly inefficient
and ill-suited for most research purposes. Scarcely 5% of the
incident light gets "registered" in the brain, and the
eye only accumulates light for about 0.1 second before the brain
"reads" out the result. Plus, it is difficult to get
quantitative information from an eyeballed measurement. Research
astronomers typically use CCD cameras to act as sensitive electronic
"eyes" that are near 100% efficient in collecting visible
light, can collect light from an object for long periods of time
and can send quantitative data directly to a computer for analysis
and interpretation.
On the other hand, many professional astronomers personally
love to look through eyepieces on both large and small telescopes...
but typically not for research purposes.
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