Astronomy Chapter 21

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

very close to their parent stars

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

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

a transit

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

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

In an extrasolar planetary system containing a single planet, the parent star is measured to move about its center of mass every 24 years. Given this, what is the orbital period of the planet?

24 years

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 the main kind of planets found by far; Jupiter and Neptune sized planets are so rare they almost never show up in our discoveries

The star now called Kepler-444 is 11 billion years old (much older than the Sun) and has five planets orbiting close to it. What has this system taught astronomers about the history of star formation?

If such an old star has planets close to it where it's really warm those planets must be made of heavier elements. So heavier elements must have formed before the time this star formed.

Which of the following is a reason that astronomers have not found Doppler or transit giant planets with the orbit of Neptune around other stars?

Neptune takes 165 years to go around the Sun; getting information about just one cycle of such a planet's orbit around another star would take astronomers 165 years

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

The great insight gained from the discovery of exoplanets is that planetary systems

appear to be common

Planets in the habitable zone of the stars:

are at a temperature where water can exist as a liquid

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

If a star has an extrasolar planet, the amplitude of its radial velocity curve is related to the planet's

mass

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 be nearly concide to our line of sight

If a star has an extrasolar planet, the symmetry of its radial velocity curve is related to the planet's

orbital shape

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

Which of the following methods uses astrometry to detect extrasolar planets around other star systems?

regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky

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

The radial velocity curve of a star with an extrasolar planet is a plot of radial velocity against

time

Stars only exhibit a Doppler shift if they are moving

toward or away from us along the line of sight

Many of the extrasolar planetary systems discovered to date are

very different than our own solar system having Jovian-size planets close to their parent stars

The few extrasolar planets that have been detected directly to date are

very large and far from their parent stars

By monitoring the changing brightness of a terrestrial exoplanet directly we could, in principle, determine the

weather pattern and/or the distribution of inhomogeneous surface structure