final module 7

If a star is 20 parsecs away, its parallax must be:

1/20th of an arcsecond

The _____ is the region of ionized hydrogen in interstellar space

H II region

An astronomer wants to observe a cloud of dust in a relatively close part of the Galaxy. Unfortunately, this dust cloud is not located in the direction of a crowded region of stars. What instrument would be the most help in finding this cloud.

a sensitive infra-red telescope in orbit around the Earth

A _____ is a star that belongs to a class of yellow supergiant pulsating stars; these stars vary periodically in brightness, and the relationship between their periods and luminosities is useful in deriving distances to them

cepheid

_____ are atomic nuclei (mostly protons) and electrons that are observed to strike Earth's atmosphere with exceedingly high energies

cosmic rays

An _____ is a planet orbiting a star other than our Sun

exoplanet

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

hydrogen

You are an astronomer whose supervisor has just forbidden drinking alcoholic beverages near the observatory. In frustration, you under¬take a search for alcohol molecules in space. Where would your search be most likely to succeed?

in an interstellar cloud of gas and dust

If you want to find stars that are just being born, where are the best places to search?

in giant molecular clouds

_____ consists of tiny solid grains in interstellar space thought to consist of a core of rocklike material (silicates) or graphite surrounded by a mantle of ices; water, methane, and ammonia are probably the most abundant ices

interstellar dust

Which of the following descriptions of interstellar dust is FALSE?

interstellar dust must be at a temperature equal to the outer layers of a star

The closest star to the Sun, Proxima Centauri, was recently found to have a planet in its habitable zone. Proxima Centauri is a main sequence star with spectral type M. How would its habitable zone differ from the habitable zone of our Sun?

it would be significantly closer to Proxima Centauri than ours is to the Sun

Astronomers must often know the distance to a star before they can fully understand its characteristics. Which of the following properties of a star typically requires a knowledge of distance before it can be determined?

its luminosity

When a star settles down to a stable existence as a main-sequence star, what characteristics determines where on the main sequence in an H-R diagram the star will fall?

its mass

A _____ is a graph that displays the time variation of the light from a variable or eclipsing binary star or, more generally, from any other object whose radiation output changes with time

light curve

What technique did astronomers use to make the first confirmed discovery of a planet around another star like the Sun?

measure the Doppler shift of the lines in the star's spectrum and look for periodic changes in this shift due to the pull of the planet as it orbits the star

An astronomer is observing a single star (and one which does not vary) which she knows is located about 30 light-years away. What was the most likely method she or her colleagues used to obtain that distance?

measuring the star's parallax

A _____ is a planet that is intermediate between the largest terrestrial planet in our solar system (Earth) and the smallest jovian planet (Neptune); generally, they have sizes between 2.8 and 4 times Earth's size

mini-Neptune

Cosmic rays differ from other forms of interstellar matter by

moving much faster, at typical speeds of 90% the speed of light

A _____ is a cloud of interstellar gas or dust; the term is most often used for clouds that are seen to glow with visible light or infrared

nebula

_____ is an apparent displacement of a nearby star that results from the motion of Earth around the Sun

parallax

A _____ is a very young star still in the process of formation, before nuclear fusion begins

protostar

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

Which type of star has the least amount of pressure in its atmosphere?

supergiants

A light curve for a star measures how its brightness changes with

time

The dust in the dust clouds in interstellar space consists of

tiny solid grains

A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?

to the left

Astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?

when nuclear fusion reactions begin inside its core

The luminosity class of a star tells an astronomer

whether the star is a supergiant, a giant, or a main-sequence star

What is the baseline that astronomers use to measure the parallax (the distance) of the nearest stars?

½ the diameter of the Earth's orbit around the Sun