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Early Astronomy


Mercury, Venus, Mars, and Jupiter orbit Earth. Heliocentric Model ... Copernicus concluded that Earth is a planet. ... 3. Venus has phases just like the moon. ... – PowerPoint PPT presentation

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Title: Early Astronomy


Early Astronomy
22.1 Early Astronomy
Astronomy is the science that studies the
It includes the observation and interpretation
of celestial bodies and phenomena.
22.1 Early Astronomy
Geocentric Model
In the ancient Greeks geocentric model, the
moon, sun, and the known planets Mercury, Venus,
Mars, and Jupiter orbit Earth.
Heliocentric Model
In the heliocentric model, Earth and the other
planets orbit the sun.
22.1 Early Astronomy
? Nicolaus Copernicus
Copernicus concluded that Earth is a planet.
He proposed a model of the solar system with the
sun at the center.
? Tycho Brahe
Brahe designed and built instruments to
measure the locations of the heavenly bodies.
Brahes observations, especially of Mars, were
far more precise than any made previously.
22.1 Early Astronomy
? Johannes Kepler
Kepler discovered three laws of planetary
1. Orbits of the planets are elliptical.
2. Planets revolve around the sun at varying
3. There is a proportional relationship between a
planets orbital period and its distance to the
An ellipse is an oval-shaped path.
An astronomical unit (AU) is the average
distance between Earth and the sun it is about
150 million kilometers.
Planet Revolution
22.1 Early Astronomy
? Galileo Galilei
He developed his own telescope and made
important discoveries
1. Four satellites, or moons, orbit Jupiter.
2. Planets are circular disks, not just points of
3. Venus has phases just like the moon.
4. The moons surface is not smooth.
5. The sun has sunspots, or dark regions.
22.1 Early Astronomy
? Sir Isaac Newton
Although others had theorized the existence of
gravitational force, Newton was the first to
formulate and test the law of universal
? Universal Gravitation
Gravitational force decreases with distance.
The greater the mass of an object, the greater
is its gravitational force.
Gravitys Influence on Orbits
Retrograde Motion
Retrograde motion is the apparent westward
motion of the planets with respect to the stars.
24.1 The Study of Light
? The electromagnetic spectrum is the arrangement
of electromagnetic radiation according to
24.1 The Study of Light
? Nature of Light
In some instances light behaves like waves,
and in others, like particles.
? Photons
A photon is a small packet of light energy.
24.1 The Study of Light
? Spectroscopy is the study of the properties of
light that depend on wavelength.
An absorption spectrum - produced when white
light passes through a cool gas under low
pressure. The gas absorbs selected wavelengths
of light, and the spectrum looks like it has dark
lines superimposed.
24.1 The Study of Light
An emission spectrum is a series of bright
lines of particular wavelengths produced by a hot
gas under low pressure.
When the spectrum of a star is studied, the
spectral lines act as fingerprints. These lines
identify the elements present and thus the stars
chemical composition.
Multi-spectrum image of a jet from a
super-massive black hole in thelower left galaxy
slamming into the galaxy in the upper right
Formation of Spectra
24.1 The Study of Light
? Doppler effect - apparent change in frequency
of electromagnetic or sound waves caused by the
relative motions of the source and the observer.
used to determine whether a star or other
body in space is moving away from or toward Earth.
24.2 Tools for Studying Space
? A refracting telescope is a telescope that uses
a lens to bend or refract light.
? Focus
The most important lens in a refracting
telescope, the objective lens, produces an image
by bending light from a distant object so that
the light converges at an area called the focus
(focus central point).
A chromatic aberration is the property of a
lens whereby light of different colors is focused
at different places.
Keck Telescope
24.2 Tools for Studying Space
? A reflecting telescope is a telescope that
reflects light off a concave mirror, focusing the
image in front of the mirror.
? Advantages of Reflecting Telescopes
Most large optical telescopes are reflectors.
Light does not pass through a mirror, so the
glass for a reflecting telescope does not have to
be of optical quality.
24.2 Tools for Studying Space
? Properties of Optical Telescopes
Both refracting and reflecting telescopes have
three properties that aid astronomers in their
1. Light-gathering power
2. Resolving power
3. Magnifying power
24.2 Tools for Studying Space
? Radio Telescopes
A radio telescope is a telescope designed to
make observations in radio wavelengths.
A radio telescope focuses the incoming radio
waves on an antenna, which, just like a radio
antenna, absorbs and transmits these waves to an
24.2 Tools for Studying Space
? Advantages of Radio Telescopes
Radio telescopes are much less affected by
turbulence in the atmosphere, clouds, and the
No protective dome is required, which reduces
the cost of construction.
Radio telescopes can see through
interstellar dust clouds that obscure visible
24.2 Tools for Studying Space
? Space telescopes orbit above Earths atmosphere
and thus produce clearer images than Earth-based
? Hubble Space Telescope
The first space telescope, built by NASA, was
the Hubble Space Telescope. Hubble was put into
orbit around Earth in April 1990.
Hubble Space Telescope
24.2 Tools for Studying Space
? Other Space Telescopes
To study X-rays, NASA uses the Chandra X-Ray
Observatory. This space telescope was launched in
Another space telescope, the Compton Gamma-Ray
Observatory, was used to study both visible light
and gamma rays.
In 2011, NASA plans to launch the James Webb
Space Telescope to study infrared radiation.
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