Atronomy 6, 5.6, and chapter 20

An astronomer wants to observe a cloud of cold neutral (not ionized) hydrogen, far away from any stars. What would be an instrument that could help in this task?

A radio telescope, tuned to a wavelength of about 21 centimeters. ( Cold, neutral hydrogen doesn't give off much radiation. however, it does give off radio waves with wavelength of 21 centimeters)

The comet-hunting astronomer who made a list of over 100 nebulae and galaxies that could be mistaken for comets was

Charles Messier

The first person who regularly turned a telescope to astronomical observations (and published his observations) was:

Galileo Galilei

An astronomer is studying galaxies of stars that are very far away and thus look extremely faint (using visible light). What kind of telescope should she and her graduate students apply for time on?

The telescope with the biggest aperture possible

Which of the following is an advantage that the Hubble Space Telescope has over large telescopes on Earth?

WRONG (find the one that is false)

When astronomers discuss a nebula, what are they talking about?

a giant cloud of gas and dust between or among the stars

In a radio telescope, the role that the mirror plays in visible-light telescopes is played by:

a large metal dish (antenna)

The largest visible-light telescopes in the world use what device to collect as much light as possible before the light is brought to a focus (to act as the light bucket )?

a mirror

What type of telescope can be used routinely on the surface of the Earth during the DAY?

a radio telescope

The Local Bubble is

a region around any exploding star where material is expanding from the explosion

To break up light into the component colors that it contains, astronomers use a device called:

a spectrometer

Where is the outer rim of the Local Bubble located today?

about 200 light-years from the Sun, in the rough direction of the constellations of Orion, Perseus, and Auriga

The size of the device that collects radiation (such as light) is called a telescope's:

aperture

What happens in the process of fluorescence?

atoms absorb ultraviolet rays and convert them to visible light as their electrons cascade to lower energy levels

Why do telescopes have to have a good motorized drive system to move them quickly and smoothly?

because the Earth is rotating, with the telescope attached to it

Why do astronomers prefer to put infrared telescopes on high-flying airplanes or on satellites in space?

because the water vapor in the lower atmosphere is very good at absorbing/ blocking infrared

Astronomers now understand that the dark regions or rifts visible in parts of our Galaxy that are otherwise crowded with stars are caused by:

clouds with a considerable amount of dust which blocks the light of the stars behind them

The most important function of an astronomical telescope is to:

collect as much light as possible and bring it to a focus

The Chandra Observatory orbiting the Earth is designed to

examine sources of cosmic x-rays

Astronomers use the term interstellar matter to refer to:

gas and dust between or among the stars

In order for a cold atom of hydrogen to emit a 21-cm wave, it must first be in a slightly higher energy state. What event usually "kicks" the hydrogen atom up to this higher state?

gas atoms within the cloud collide

The red color we see on a lot of photographs of nebulae comes from which element?

hydrogen

Astronomers have found large quantities of cold, neutral hydrogen gas in our galaxy. How is this gas distributed?

it is found mostly in a flat layer extending throughout the disk of our galaxy

At the largest and most modern astronomical observatories on Earth today, which of the following regularly happens to the image formed by the telescope?

it is recorded using an electronic detector called a CCD for later analysis

When the James Webb Space Telescope is finally launched, what will be its distinguishing characteristic (what about it will really help astronomers)?

it will have the largest mirror aperture ever put into space for observing faint objects

A very wealthy donor decides to give a large sum of money to your college or university to build the world's largest visible-light gathering telescope. From an astronomical perspective, where would be the best location to put such a telescope?

on a tall, dry mountain

When a star or galaxy is moving away from us, we observe the Doppler effect by seeing the lines in its spectrum

red-shifted (shifted toward the red end of the light spectrum)

The earliest telescopes used by astronomers were:

refractors

The amount of interstellar matter present in our Galaxy is always changing. Which of the following processes is NOT a major contributor to that change?

some atoms of gas combine in dusty clouds to make more complex molecules

An astronomer who is observing visible light from a glowing cloud of gas in space uses an instrument which contains a grating with thousands of grooves on its surface. What will this instrument allow our astronomer to do?

spread out the light from into a spectrum

Astronomical observatories have been available since ancient times, and many cultures set aside special sites for astronomical observations. The thing modern observatories have that was missing from these older observatories until about 1610 was:

telescopes

We observe a glowing cloud of gas in space with a spectroscope. We note that many of the familiar lines of hydrogen that we know on Earth seem to be in a different place. They are shifted toward the blue or violet end of the spectrum compared to their positions in the spectrum of glowing hydrogen gas on Earth. From this we can conclude that:

the cloud is moving toward us (blue shifted)

When a knowledgeable amateur astronomer tells you that she has a 14-inch telescope, what does the number 14 refer to?

the diameter of the primary lens or mirror

You are observing a binary star system and obtain a series of spectra of the light from the two stars. In this spectrum, most of the absorption lines shift back and forth as expected from the Doppler Effect. A few lines, however, do not shift at all, but remain at the same wavelength. How can we explain the behavior of the non-shifting lines?

the lines come from interstellar matter between us and the star, not from the stars themselves

What was the major problem with the Hubble Space Telescope when it was first launched into orbit?

the mirror's shape was slightly wrong, so all the light did not come to a single focus

The term baryon cycle, as astronomers use it, refers to:

the movement of interstellar material into the Galaxy and into stars and then the movement out when stars end their lives

Christian Doppler discovered what we now call the Doppler Effect by measuring:

the properties of sound waves coming from a group of musicians on a moving, open railroad car

Astronomers use the term interstellar extinction to refer to:

the scattering and absorption of starlight by dust grains in space

When astronomers do radar astronomy, they

they bounce a radar beam off the surface of solid objects in our solar system

When the twin Keck telescopes were built in the 1990 s, what distinguished them from other very large telescopes of the time?

they used a mirror assembly that was made of 36 smaller hexagonal mirrors working together

Some of the interstellar gas in our Galaxy has been heated to millions of degrees, a temperature that surprised astronomers when it was first discovered. How do we now think that gas between stars gets that hot?

very powerful shock waves from exploding stars (supernovae) heat the gas they come into contact with

Radio telescopes of modest size can't make out as much detail (have a lower resolution) than visible light telescopes. How do astronomers overcome this limitation?

we can connect several radio telescopes some distance apart together electronically to give us the resolution of a larger telescope