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Chapter 18 – Studying Space
•Astronomy – The study of space, stars the
visible universe.
•Year – The amount of time required for the Earth
to orbit the sun once.
•Month – The amount of time required for the
moon to orbit the Earth once. Derived from the
old English word “moonth”.
•Day – The amount of time required for the Earth
to rotate once on its axis.
Early Astronomers
• Ptolemy – Circa 140 C.E., developed the theory that placed the
Earth at the center of the universe. Successful in that this belief
persisted for over 1500 years and did accurately predict the
motions of the planets.
• Nicholai Copernicus – Developed a new theory that placed
the sun at the center of the universe (heliocentric) and had the
Earth and other planets orbiting it.
• Tycho Brahe – Used a mural to get precise measurements of
the planets orbits which helped future astronomers.
• Johannes Kepler – Demonstrated that the planets followed
elliptical orbits and developed the three laws of planetary
motion which are still in use by various space agencies today.
• Galileo Galelei – Invented and was the first to use a telescope
to observe the moon and planets.
• Isaac Newton – His insights into gravitational forces explained
how planets and moons are able to stay in their orbits.
• Edwin Hubble – Proved the existence of galaxies beyond ours.
• A device that collects and focuses electromagnetic radiation
from objects in space making it observable.
• Optical Telescopes – The most common type of telescope it is
designed to collect and focus visible light for close observation.
• Refracting Optical Telescope – The simplest type uses two
lenses to magnify light. Cannot perfectly focus and their size is
limited due to sagging of the glass lens.
• Reflecting Optical Telescope – Uses a mirror to gather light
and reflects it to a lens eyepiece where it is magnified. Can
gather more light, focuses a perfect image and can be made
larger so this type is preferred by professional astronomers.
• Hubble Space Telescope – A reflecting telescope placed in
orbit in 1980 to avoid atmospheric interference and can see
very faint objects in space.
Electromagnetic Spectrum
• All of the wavelengths of electromagnetic
radiation such as visible light, microwaves,
radio waves etc. For visible light, the longest
wavelength is the color red and the shortest is
the color blue. The invisible part makes up most
of the spectrum and the shorter wavelengths
are blocked by the Earth’s atmosphere which
acts as a protective shield. X-Ray wavelengths
are completely blocked so to observe them, xray telescopes are placed in orbit to detect
Nonoptical Telescopes
• Detect nonvisible radiation.
• Radio Telescopes – Detect radio waves
and can be used anytime.
• V.L.A. – The very large array is composed
of 27 radio telescopes linked by computer.
• Chandra X-Ray telescope – Placed in
• Infrared and gamma ray telescopes
detect much more sensitive information.
Mapping the Stars
• Constellation – A pattern of stars in the sky, many of which
were given Greek names.
• Astrolabe – An instrument used to describe the location of a
• Zenith – An imaginary point directly above any observer.
• Horizon – The point where the sky and the Earth appear to
• Altitude – the angle formed between an object and the horizon.
• Celestial Sphere – An imaginary sphere surrounding the Earth
used as a reference guide for scientists to map the sky.
• Ascension – How far an object is from the Vernal Equinox, the
point where the sun rises on the first day of spring, and
measures East and West.
• Declination – Measures North and South from the celestial
• Circumpolar stars – Stars near the poles that
can be seen all year long and all night long.
• Light Year – The distance light will travel in a
vacuum in one Earth year approx. 6 trillion
miles or 9 trillion km. Stars are much farther
away than the planets and require another
more useful scale than miles or kilometers.
• Scientists have observed that the universe is
expanding and the visible light from other
galaxies is shifted into red wavelengths. This
was confirmed by the Hubble Space
Telescope’s observations of distant stars.
Doppler Shift
• Red Shift – The apparent change in color
towards the red end of the spectrum that
occurs when an object is moving quickly
away from an observer.
• Blue Shift – The apparent change in color
towards the blue end of the spectrum that
occurs when an object is moving quickly
towards an observer.