Astronomy
is the study of all
extraterrestrial objects and phenomena. Until the invention of the telescope and the discovery of the laws of motion and gravity in the 17th century, astronomy was primarily
concerned with noting and predicting the positions of the Sun, Moon, and planets, originally astrological purposes and later for navigational uses and scientific interest. The catalog of
objects now studied is much broader and includes, in order of increasing
distance, the solar system, the stars that make up the Milky Way Galaxy, and other, more distant galaxies. With the advent of scientific space
probes, Earth also has come to be studied as one of the
planets, though its more-detailed investigation remains the domain of the Earth sciences. NASA
defines astronomy as simple "the study of stars, planets and space."
Astronomy is split into observational and theoretical branches.
Observational astronomy is focused on getting data from observations of
astronomical objects. This data is then analyzed using principles and laws of physics. Theoretical
astronomy is the development of computer
or analytical models to describe astronomical objects and phenomena. These two
fields complement each other.
Astronomers are unable to observe a system from birth to death, the lifetime of planets,
stars, and galaxies span millions to billions of years. Instead, astronomers
must rely on photos of bodies in various stages of evolution to determine how
they formed, evolved and died. Hence, theoretical and observational astronomy
tend to be together, as theoretical scientists use the information actually
collected to create simulations, while the observations serve to confirm the
models.
Unsolved
problems in astronomy
- What is the origin of
the stellar mass spectrum? That is, why do astronomers observe the same
distribution of stellar masses—the initial
mass function—apparently regardless of the initial conditions? A
deeper understanding of the formation of stars and planets is needed.
- Is there other life in
the Universe? Especially, is there other intelligent life? If so,
what is the explanation for the Fermi paradox? The existence of life
elsewhere has important scientific and philosophical implications.
- What is the nature
of dark matter and dark energy? These dominate the
evolution and fate of the cosmos, yet their true nature remains unknown.
- How did the first
galaxies form? How did supermassive black holes form?
- What is creating the ultra-high-energy cosmic rays?
- Why is the abundance
of lithium in the cosmos four times lower than predicted by the
standard Big Bang model?
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