telescopes and spacecraft
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Telescopes and Spacecraft. Astronomy 311 Professor Lee Carkner Lecture 7. How Do We Learn About The Solar System?. View from Earth: View remotely: Other methods: visit in person (Moon only) find pieces of solar system that have visited us (meteorite). How Do Telescopes Work?. - PowerPoint PPT PresentationTRANSCRIPT
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Telescopes and Spacecraft
Astronomy 311Professor Lee
CarknerLecture 7
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How Do We Learn About The Solar System?
View from Earth:
View remotely:
Other methods: visit in person (Moon only) find pieces of solar system that have
visited us (meteorite)
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How Do Telescopes Work?
Telescopes: Focus light to produce an image
Light gathering ability (not magnification) is the most important attribute of a telescope
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Lenses
Lenses bend light (refraction) and
focus all of the light incident on the front to a point (focus) a certain distance behind the lens (focal length)
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Lenses and Refraction
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Refracting Telescope
If you put a second lens (eyepiece) behind the first lens(objective), you can magnify the image
Magnification is equal to the ratio of the focal lengths in practice the magnification you can achieve is
limited by the blurring effects of the Earth’s atmosphere
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Refracting Telescope
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Giant Refractor at Yerkes Observatory
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Refractors and Reflectors
It is hard to make large refracting telescopes
A curved mirror can be used to gather and focus the light instead (reflecting telescope)
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Reflecting Telescopes
Problem: The focal point is between the mirror and the sky
Cassegrain Telescope -- secondary reflects light through a hole in the primary, most common type of large telescope
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Cassegrain Reflecting Telescope
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The Hobby-Eberly Telescope
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Types of Detectors Eye --
Photographic plate --
Charge Coupled Device (CCD) -- more sensitive and easier to use than a plate, allows you to store and reduce data electronically Today, light is moved around with fiber optic cables and
data is moved electronically
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The Electromagnetic Spectrum
Every photon (light particle) has a wavelength which places it in the electromagnetic spectrum
The wavelength relates to energy
We see different wavelengths of visible light as colors
We want to view all types of electromagnetic radiation
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The Electromagnetic Spectrum
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Telescope Taxonomy Radio and Millimeter -- penetrates atmosphere and
everything else
Example: The VLA (Very Large Array)
Infrared (IR) -- we feel as heat
Example: IRAS (Infrared Astronomical Satellite)
Optical -- what our eyes can see
Example -- Hubble Space Telescope
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More Telescope Taxonomy Ultraviolet (UV) -- high energy radiation, causes
sunburn
Example -- IUE (International Ultraviolet Explorer)
X-ray -- very high energy
Example -- Chandra X-ray Observatory
Gamma Ray -- the highest energy
Example -- Compton Gamma Ray Observatory
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The VLA
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Hubble Space Telescope
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Spacecraft Since the 1960’s we have sent probes to study
the planets close up Types of spaces probes:
Fly-by -- Example: Voyagers I and II
Orbiter --
Example: Mars Global Surveyor
Lander --
Example: Mars Pathfinder
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Getting to The Planets
Spacecraft don’t zoom around the Solar System like in science fiction
Use small thrusters to maneuver (remember Newton’s First Law -- Inertia)
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Least Energy Orbit
After that it follows Kepler’s Laws
An orbit that intersects the Earth’s orbit at one point and the other planet’s orbit at another point (on the opposite side of the Sun)
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Least Energy Orbit to Mars
Sun
Earth
Mars
Spacecraft Orbit
Time to get to Mars P2=a3
aEarth = 1 AU Time = =
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Summary
Refracting Telescopes use a lens to bend light to a focus
Reflecting Telescopes use a mirror to reflect light to a focus Most large research telescopes are
reflectors Astronomers today record and
analyze data digitally
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Summary To observe the entire
electromagnetic spectrum you need many different types of telescopes, some of them in space
Spacecraft have allowed close up study of the planets Spacecraft reach their destinations by
using the gravity of the Sun (or sometimes planets)
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Next Time
Read 15.1-15.4, 6.7 Quiz #1 on Monday
Study hard!