Astronomy Chapter 21

A graduate student is given the assignment to find stars with dusty disks around them. What type of telescope would be best for her to use for this purpose?

a large telescope that detects infrared radiation

Which of the following extrasolar planets would be the most difficult to detect using the Doppler shift method?

a low mass planet far from its parent star

Which of the following extrasolar planets would be easiest to detect using the Doppler shift method?

a massive planet close to its parent star

Astronomers call a ball of matter that is contracting to become a star

a protostar

When an exoplanet passes in front of its parent star, we call this

a transit

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

in giant molecular clouds

How can we explain the presence of extrasolar planetary systems with Jovian-sized planets at distances at which we normally find terrestrial planets?

the Jovian planets formed farther out and then migrated inward

The telescope that allowed astronomers to discover most of the planets found with the transit method was called

the Kepler mission

With our current techniques, astronomers can typically only measure the minimum mass of a planet orbiting another star. To know the precise mass of the planet they must also be able to determine,

the angle at which the planet's orbit is tilted relative to us

Which of the following are the small regions that are the embryos of stars (where individual stars are most likely to be born)?

the cores within the clumps of molecular clouds

What observations about disks of dusty material around young stars suggest that planets may be forming in such disks?

the disks show lanes that are empty of dust within them

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

A Herbig-Haro (HH) object is

where a jet from a star in the process of being born collides with (and lights up) a nearby cloud of interstellar matter

The first ordinary star (other than our own Sun) around which planets were definitely discovered was:

51 Pegasi

When astronomers carefully examine the planets found by Kepler and draw conclusions from the Kepler sample what do they conclude about planets the size of Earth?

Earth-sized planets are common, but so are planets somewhat bigger than Earth (?)

Our solar system has 8 planets orbiting the Sun. Based on the discoveries of exoplanets so far, what can we say about a star with 8 planets?

Even though planets were only discovered starting in 1995, so we can't yet find planets that take centuries to go around their star, we already know other stars with 8 planets and we are likely to find more

Why was the Kepler mission not able to find planets smaller than Mars even though it was in space (and had no Earth atmosphere to deal with)?

Such planets make dips in the light of the star that are too small for Kepler to detect

Which of the following methods describes the transit method for detecting extrasolar planets?

detection of brightness changes in a star as a planet passes in front of it

If we are eventually able to detect Earth-like extrasolar planets directly, they will be seen very

far from their parent stars and will be very dim in comparison

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 a cooler temperature. 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 believe that disks of material will form around protostars that are spinning. Which of the following observed phenomena is a good indication of the presence of a disk around a protostar?

jets and Herbig-Haro objects

In figuring out the evolutionary tracks on the H-R diagram, astronomers

make model stars on a computer and then follow how their characteristics will change with time

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

Astronomers were surprised to find so many Jupiter-mass planets so close to their stars. According to their best theories and models such "hot Jupiters"

must have formed further out from the star and must have "migrated inward" early on

According to our current theory of planet formation, can a Jupiter-like planet form from a rotating disk of dust and gas close to its parent star?

no, because it would be too hot for gases to condense

For the transit of an extrasolar planet to be observed, the

orbital plane has to nearly concide to our line of sight

The big surprise about the first planet discovered around another regular star was that it

orbited so close to its star it took only 4 days to go around

Which of the following is NOT one of the reasons planets around other stars are so difficult to detect?

planets only form very late in the life of a star just when it is ready to die and thus last only a very short fraction of the star's life

The recently discovered rocky terrestrial-like exoplanets with masses a few times that of the Earth are sometimes called

super Earths

To measure how dense a planet is (to know whether it is made of rock or gas and liquid) they must be able to measure the planet's mass from the Doppler shift and

the planet's radius using the transit method

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

to the left

Stars only exhibit a Doppler shift if they are moving

toward or away from us along the line of sight

Most of the extrasolar planets detected by the Doppler technique are found

very close to their parent stars

Astronomers studying regions like the Orion Giant Molecular Cloud have observed that a wave of star formation can move through them over many millions of years. What sustains such a wave of star formation in a giant molecular cloud?

when massive stars form, their ultraviolet radiation and later their final explosions compress the gas in the cloud and cause a new group of stars to form