Astronomy, Quiz 1; Chapter 6

The world's largest refracting telescope has a lens of __ meter(s) in diameter

1

Arecibo's angular resolution is about

1 arcminute

Human eye has an angular resolution of ____________; if two dots are separated by less than that, our eyes will not be able to distinguish them individually

1 arcminute

Two most fundamental properties of any telescope:

1) Light collecting area 2) Angular resolution

Images made with invisible light cannot have any natural color because

"Color" is a property only of visible light

Beams of light can interfere with one another because they are waves; this interference limits a telescope's __________

Angular resolution

The smallest angle over which we can tell two dots are distinct

Angular resolution

Long wavelengths of radio signals means that radio telescopes need to be very ______

Big

the fact that lens brings different colors of light into focus at slightly different places

Chromatic aberration

The process of linking two or more individual telescopes to achieve the angular resolution of a much larger telescope

Interferometry

Through _________, radio telescopes can work together to achieve much greater angular resolution

Interferometry

Today, many astronomical images are made from

Invisible light

Radio telescope consisting of 27 smaller dishes, combined area equivalent to 130 meters across or, at times, 40 kilometers

Karl G. Jansky Very Large Array (JVLA)

Picture elements

Pixels

Turbulence tends to limit the angular resolution of ground telescopes to ________________, regardless of their diffraction limit

0.5 arcsecond

The diffraction limit depends on what two criteria:

1) diameter of telescope's primary mirror 2) wavelength of light being observed

Most observations fall into three basic categories:

1) imaging, yields photographs 2) spectroscopy, obtain and study spectra 3) time monitoring, track how an object changes with time

Two reasons that reflector telescopes are mainly used today:

1) light passes through the lens of refracting telescope, so lenses must be made from exceptional material 2) large glass lens are extremely heavy and difficult to stabilize 3) chromatic aberration

Our atmosphere creates 3 other problems that inevitably affect observations:

1) light pollution 2) turbulence in atmosphere 3) fact that most forms of light can't reach Earth's surface

Three types of "cosmic messengers"

1) neutrino, produced by nuclear reactions 2) cosmic rays 3) gravitational waves

Only what kinds of light can be observed from the ground?

1) radio waves 2) visible light 3) the longest wavelengths of UV light 4) small parts of infrared spectrum

Three particularly important telescope sites:

1) summit of Mauna Kea on the Big Island of Hawaii 2) La Palma in Spain's Canary Islands 3) Paranal Observatory site in Chile

Galileo first turned his telescope to the heavens in

1609

A 10-meter telescope has 5 times the diameter of a 2 meter telescope, so its light-collecting area is __ times as great

25, or 5^2

World's largest digital camera

3200 megapixels

Technology that can eliminate turbulence and the blurring associated by making mirrors bounce opposite of blurred stars

Adaptive optics

A point of light in Earth's atmosphere created by a laser

Artificial star

At its most basic, an imaging instrument is simply a

Camera

Offers the best angular resolution of any X-ray telescope yet built; better for making images

Chandra

X ray telescopes

Chandra X-Ray Observatory, NuSTAR mission

Cells within the retina

Cones and rods

Most obvious problems with observing from the ground

Daylight and weather

Technical term for the effects of interference that limit telescope resolution

Diffraction

the angular resolution that a telescope could achieve if it were limited only by the interference of light waves is called its

Diffraction limit

What is one problem of infrared telescopes?

Earth and even the telescope itself emit infrared thermal radiation

Parallel rays of light converge to a point called the

Focus

The place where the image appears in focus is called the

Focus plane

Fermi Space Telescope used to detect what kind of light

Gamma-ray

____________________ observatories use massive detectors to capture photons and determine from whence they came

Gamma-ray

Specially designed mirrors can deflect X rays; X rays merely graze their surface as the rays are directed toward the focal plane

Grazing incidence mirrors

Spectral resolution depends on

How widely the spectrograph spreads out light

Presently, this telescope is the only major space observatory capable of observing ultraviolet observations

Hubble Space Telescope

What is the most famous observatory in space

Hubble Space Telescope

NASA's SOFIA carries a 2.5 meter _____ telescope that looks out through a large hole cut in the body of a 747

Infrared

The atmosphere glows at many ____________ wavelengths

Infrared

How much total light a telescope can collect at a time

Light collecting area

We characterize a telescope's size by the diameter of its

Light collecting area

The results of time monitoring are often shown as __________________: graphs that show how an object's intensity varies with time

Light curves

Our atmosphere scatters bright lights of cities at night, creating ________________

Light pollution

Basic components of the human eye

Pupil, lens, retina

The Arecibo telescope stretches 305 meters (1000 ft) across a natural valley in Puerto Rico and is the world's largest single telescope; it is what kind of telescope?

Radio

The atmosphere does not scatter most __________________, so these telescopes can operate day and night and under cloudy skies

Radio

To which kind of telescope would the Moon be useful (acts as a shield to block out Earth's interference)

Radio

A ______________ telescope uses a curved primary mirror to gather light; this mirror reflects light to a secondary mirror that reflects light to a focus point where eyes and instruments can observe it

Reflecting

Nearly all telescopes used in research today are ________________

Reflectors

A ___________ telescope operates much like an eye, using glass lenses

Refracting telescope

Kind of telescope that Galileo used

Refracting telescopes

A change in direction in which light is travelling

Refraction

The most common kind of telescope in the world

Satellite dish

The information we can glean from a spectrum depends on the

Spectral resolution

Instruments called ________________ use diffraction gratings to separate the various colors of light into spectra, which are then recorded with a detector

Spectrographs

The ever changing motion in the atmosphere, or _____________ bends light in constantly shifting patterns

Turbulence

What causes the twinkling of stars?

Turbulence

Image formed by a lens is

Upside down

What kind of light rays have sufficient energy to penetrate many materials, including ordinary mirrors

X rays

Has largest collecting area of any other X-ray telescope; better for making spectra

XMM-Newton

The ultimate limit of a telescope's resolving power comes from

the properties of light