Difference Between Astronomy and Planetary Science
Space Astronomy
Until recently, astronomers practically worked with blinders on. These blinders did not restrict astronomers to viewing narrow swaths of sky. Instead, they limited astronomers to fairly narrow swaths of the electromagnetic spectrum.
The universe emits a whole palette of electromagnetic radiation. Types of radiation include radio waves, microwaves, ultraviolet radiation, visible radiation, infrared radiation, and X rays. Earth’s atmosphere permits much of the visible light and radio waves from space to reach the planet’s surface. But other kinds of radiation are mostly or entirely blocked.
Some forms of radiation, such as infrared, reach Earth’s surface only at locations such as mountaintops, where the air is thin, or deserts, where humidity is low. And some forms of radiation, such as ultraviolet, may be observed through telescopes carried high into the atmosphere by special aircraft, weather balloons, or sounding (suborbital) rockets.
Trying to understand the universe by looking only at the visible and radio portions of the spectrum, and stealing occasional glances at the infrared and ultraviolet, is like trying to assemble a jigsaw puzzle even though most of the pieces are missing. However, astronomers may effectively find the missing pieces by using space-based observatories.
Since the 1960s, rockets have been used to launch specially designed telescopes into orbit. Such telescopes, effectively perched above Earth’s atmosphere, have provided clear and sustained views of the entire electromagnetic spectrum. And these views have revealed a remarkably different universe. That is, piecing together all the available views—from radio-wave to visible-range to gamma-ray light—has produced a clearer, more complete, and undistorted picture of the universe.
The Hubble Space Telescope (HST), launched by the National Aeronautics and Space Administration (NASA) in 1990, came to represent a milestone in space-based observatories. When the HST started delivering images, scientists found that they had 10 times the clarity of images that were available from even the largest ground-based instruments. Such high-clarity images, from the HST and other space-based platforms, have dramatically altered our understanding of the universe.
Planetary Science
Scientists who study the planets and their moons, asteroids, comets, and other objects of our solar system once held exclusive claim to the title “astronomer.” This subdivision of astronomy is now referred to as planetary science, and its practitioners work in fields as diverse as geology, meteorology, physics, chemistry, oceanography, volcanology, and biology, which they then apply to astronomy.
Even engineers contribute to planetary science, since distant celestial bodies are now studied by robot spacecraft that either orbit around or land on them. These robots carry extremely sophisticated packages of electronic hardware, optical instrumentation, and highly advanced computers to perform research far from Earthbound scientists.