PY 123 - Chapter 6
If telescope A is 160 cm in diameter, and telescope B is 32 cm in diameter, how much more light does telescope A gather than telescope B?
25 times
What is the shape of the segmented mirrors of twin Keck Observatory telescopes, Gran Telescopio Canarias, and the James Webb Space Telescope (scheduled to be launched in late 2018)?
hexagonal
Built in 1963, the Answer telescope in Puerto Rico is the largest single radio dish in the world.
Arecibo
No radio waves penetrate the Earth's atmosphere.
False
All telescopes must be operated on site by an astronomer or a technician.
False
Refracting telescopes use a mirror to gather and focus light.
False
Which is the longest surviving, and most successful, space telescope?
Hubble Space Telescope
What modern-day instrument do astronomers use to record images from telescopes?
charge-coupled device
A optical distortion of refracting telescopes called Answer causes a separation of colors, such as when you focus on one color, the other colors in an image are blurred.
chromatic aberration
What does chromatic aberration separate within refracting telescopes?
color
CCD images captured from telescopes are often ____ to be stored in a computer's memory for later analysis.
converted to numerical data
Space telescopes carrying long-wavelength infrared detectors must carry Answer for their optics to avoid the insides of the telescope and instruments from blinding the detectors.
coolant
What must be used to maintain the optics and operation of an infrared telescope?
coolant
The Chandra observatory uses Answer mirrors in which the X-rays reflect at shallow angles from the polished inside of the mirrors to form images on X-ray detectors.
cylindrical
Light-gathering power and resolving power both depend on what characteristic of a telescope?
diameter
What characteristic of a telescope controls the amount of light captured by the telescope?
diameter of tube
The ____ of a radio telescope collects and focuses radiation.
dish
A lens called the Answer is typically used to magnify the image and make it convenient to view distant objects.
eyepiece
Which part of a telescope is responsible for magnifying an image?
eyepiece
Cosmic rays are made of photons.
false
Gravity waves have never been detected.
false
Reflecting telescopes suffer from chromatic aberration because the light must pass through the glass.
false
Resolving power is measured in nanometers.
false
Radio telescopes are often located near populated areas.
false
Which type of electromagnetic wave is the shortest?
gamma
The energy a photon carries is inversely proportional to __________.
its wavelength
What does a refracting telescope use to gather and focus light?
lens
Astronomers no longer build large observatories in populated areas in order to avoid
light pollution
It is a common misconception that the purpose of an astronomical telescope is to_______ images.
magnify
Which form of radiation has the lowest frequency?
microwave
What unit is used to measure wavelengths?
nanometers
What is a major selecting factor for astronomers looking to place a telescope atop a mountain?
non-turbulent airflow
Two devices that spread white light into a spectrum are Answer and __________.
prisms/grating
Which form of electromagnetic radiation is able to easily reach Earth's surface through an atmospheric window?
radio
Visible light with wavelengths at the long-wavelength end (λ = 700 nm) appears as which color?
red
All large astronomical telescopes built since the start of the 20th century have been Answer telescopes.
reflecting
One way to measure and compare the strength of the radio signal at various places in the sky is to produce a(n) Answer in which each color marks areas of similar radio intensity.
representational-color image
Diffraction, optical quality, and atmospheric conditions all contribute to the limitations of what power of a telescope?
resolving power
Which power of a telescope reveals fine details within an image?
resolving power
What telescope instrument is used to counter the eastward rotation of Earth?
sidereal drive
Space-based telescopes carrying long-wavelength infrared detectors must carry coolant such as liquid helium to chill their optics to near absolute zero temperature.
true
Large doses of Answer light can cause sunburn and skin cancers.
ultraviolet
Optical telescopes are intended for the study of Answer light
visible
A spectrograph spreads out light according to ____ to form a spectrum.
wavelength
Why aren't optical or radio telescopes used in particle astronomy, which studies cosmic waves and gravity waves?
Optical and radio telescopes can only detect electromagnetic radiation.
Where would you most likely find a large radio telescope?
in a mountain valley
The Very Large Array radio telescope in New Mexico is an example of the use of which astronomical technique?
interferometry
A(n) __________ is both an image-recording device and a photometer.
CCD
Which type of focus is most common for larger telescopes?
Cassegrain focus
Which telescope will be launched into solar orbit and eventually replace observations made by the Hubble Space Telescope?
JWST
Jenny, who lives on a farm in a rural part of New York, calls her cousin, Karen, in Brooklyn, to tell her that she can see the Milky Way in tonight's night sky. However, Karen says she can't see it at all. What is preventing Karen from seeing the Milky Way in the night sky?
Karen lives in an area with light pollution.
Why are X-rays and gamma rays considered dangerous forms of light?
Photons of these wavelengths have high energy.
Refracting and reflecting telescopes form an image that is small, inverted, and difficult to observe directly; therefore, an eyepiece is normally used to magnify the image and make it convenient to view.
T
What is so unique about the mirrors of telescopes such as the Keck Observatory, Gran Telescopio Canaries, and the soon-to-be-built Giant Magellan Telescope?
The mirrors are segmented.
What is the function of the receiver antenna of a radio telescope?
To absorb the radio energy collected by the dish
Red light of the visible light spectrum has longer wavelengths than blue.
True
Short-focal-length lenses and mirrors must be strongly curved.
True
The larger the diameter of a telescope, the more light it will collect.
True
What type of electromagnetic radiation does Chandra collect?
X-ray
Which telescope is the largest refracting telescope in the world?
Yerkes Observatory refractor telescope
Light-gathering power is proportional to the Answer of a telescope's primary lens or mirror.
area
What technique often requires the use of a laser guide star?
adaptive optics
James Webb Space Telescope
→ A next generation space telescope that will be placed in a solar orbit
Chandra
→ A space telescope that detects X-rays
HST
→ A space-based telescope that detects visible, UV, and infrared wavelengths
SOFIA
→ An airborne telescope that captures short infrared wavelengths
Very Large Array
→ Radio interferometers in the desert of New Mexico
Yerkes Observatory
→ The largest refracting telescope in the world
Arecibo Telescope
→ The largest single radio dish in the world
Keck Observatory
→ Twin telescopes atop Mauna Kea whose primary mirrors are made of 36 individual hexagonal segments
