Astronomy is the study of anything outside of Earth’s atmosphere.  Astronomers study by looking at the sky, and in some cases listening to the sky.  This study can be done with something as simple as a pair of binoculars in your backyard, to the probes NASA sends through the solar system.

Who Is Considered An Astronomer?

An astronomer is, again, anyone studying anything outside of the atmosphere, and since this can be done very simply, almost anyone can take this up as a hobby and call themselves as astronomer.  Worldwide there are about 15,000 astronomers.  However, in the United States alone, there are over 300,000 astronomers.  Astronomy is an area of science that the amateur often makes significant contributions. 

In early days, the astronomer would look at the sky with the naked eye, and track the Sun, Moon, and stars so they could figure the seasons and the lengths of the year to help them now when to plant and harvest.  These observations were crucial to their life, and would determine if they woulAmateur AstronomersCredit: flourish, or even survive.

Amateur Astronomers

Amateur astronomers usually study the sky through observation.  With a good pair of binoculars, an amateur astronomer can see a lot of details.  And in these modern times, a very good telescope is relatively inexpensive.  Remember, up until the invention of the telescope in 1608 or so, all observation of the skies was done with the naked eye.  Even Galileo, considered the father of modern observational astronomy, worked with telescopes of only 3x magnification at first. 

An amateur astronomer knows all the constellations.  Events like meteor showers, comets and eclipses draw those with this hobby, and they may travel all over the world to be in a good position to view the event.

Astronomers watch for changes in the sky.  Many asteroids and comets have been spotted by amateur astronomers.  Amateur astronomers can monitor the brightness of variable stars, and monitor the shadows cast by asteroids to figure out their shape and size. 

With the near sky becoming better known, some professional types of astronomy are done without even looking at the sky and the professionals that pursue these professions may not even know the constellations and how they look in the sky.  The amateur carries forward a tradition from man’s beginnings.

Observational Astronomy

Optical astronomy is the oldest form of astronomy, and the most suited to the amateur.  This means just looking at the sky with our eyes and seeing what we can see.  When astronomy first originated, views of the sky would be drawn by hand.  Today, we can use photographic eqAstronomers Study The SkyCredit:, and even digital detectors. 

Most other forms of observation astronomy must be done from high in the Earth’s atmosphere or in space, as the rays are absorbed by the Earth’s atmosphere.  Ultraviolet astronomy is observation at ultraviolet wavelengths.  X-ray astronomy is done by observing x-rays, as the name suggests.  Gamma astronomy uses a space based satellite to observe gamma rays striking the atmosphere, and turns that into information for the astronomer. 

Celestial Mechanics

Measurement of the positions of the objects in the sky goes along with observing them.  Ancient man wanted to know when the Sun, Moon, planets, and stars would come around.  After observing them, they would work at tracking them mathematically.  In modern days, celestial mechanics enables us to track the objects in the sky, but also enables us to track satellites and other man-made objects when we put them up, to ensure that we put them in safe orbits.  

Knowing how the planets move also enables space agencies to send probes to other planets and moons.  Just as you lead a target when throwing a baseball or shooting a gun, to send a probe to another planet, the space agency must know where it will be in the future.  And, with distances so large, the calculations need to take into account the influence other celestial bodies might have on the probe during its travel.

Theoretical Astronomy

In theoretical astronomy, the astronomer tries to figure out how the observations they have fit into what we think we know.  If data is received that will not fit into the current theories, the theoretical astronomer works to modify the theory to make it fit all the data now in their possession.

Other SubFields

Of course, just like any other field, there are specialty fields.  Name something in the sky, and there is someone studying it.  There are astronomers that study the sun.  There are astronomers who study how the planets are formed in a new solar system.  There are those that study solarSome Astronomers Study Only The SunCredit: systems, galaxies, objects outside of the galaxy, specific objects like black holes, or neutron stars, and dark matter.


Astronomy can be as large or as small a study as you want.  Every time you look up at the sky, and look beyond the clouds to the stars, you are practicing astronomy.  So, the answer to the question, “What is Astronomy”, is simple.  Just look up.