AST CHAPTER 13

Assume that the migration hypothesis is the correct explanation for the hot Jupiters. In that case, the revised nebular theory looks just like the old theory, except that it now allows for the possibility of migration. Which of the following statements are consistent with this revised theory?

1. Jovian planets can migrate inward and disrupt the orbits of terrestrial planets. 2. Jovian planets always form in the cold, outer regions of their star system. 3. Terrestrial planets always form in the warm, inner regions of their star system.

Suppose you are using the Doppler technique to look for planets around another star. What must you do?

Compare many spectra of the star taken over a period of many months or years.

Which of the following will allow you to learn something about a transiting planet's atmospheric composition?

Compare spectra obtained before and during an eclipse.

Today, the leading hypothesis for the existence of hot Jupiters is that they formed in their outer solar systems and then migrated inward. Why did this hypothesis gain favor over alternative ideas?

Computer models that simulate planetary formation show that interactions between young planets and other material in the surrounding disk can cause planetary migration.

When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?

In a decade or two, through space observatories now in the early planning stages.

From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?

It causes the Sun to move in a small ellipse with an orbital period of about 12 years.

Each item describes a characteristic that applies to one of the three planet-detection methods shown following. Match the items to the correct planet-finding method. *ASTROMETRIC METHOD*

Measures precise changes in a star's position in the sky, in fractions of arcseconds. (could detect a planet in an orbit face-on to the earth)

Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?

Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?

Our solar nebula must have been blown into space shortly after the formation of the jovian planets.

Each item describes a characteristic that applies to one of the three planet-detection methods shown following. Match the items to the correct planet-finding method. *TRANSIT METHOD*

Planet-detection strategy of NASA's Kepler Mission// Can Potentially detect planets in only a few percent of all planetary systems// Allows for the extrasolar planet's radius to be determined// this method was first to identify earth-sized extrasolar planets// looks for very slight, periodic dimming of a star. 1%

You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?

The planet must be closer to the star than Earth is to the Sun.

Why is it so difficult to take pictures of extrasolar planets?

Their light is overwhelmed by the light from their star.

The discovery of hot Jupiters led scientists to reconsider the nebuar theory. Which of the following best explains why the nebular theory(as it stood before the discoveries of extrasolar planets) had not predicted the existence of hot Jupiters?

There are no hot Jupiters in our solar system.

Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?

These planets migrated inward after being born on orbits much farther from their stars.

Each item describes a characteristic that applies to one of the three planet-detection methods shown following. Match the items to the correct planet-finding method. *DOPPLER METHOD*

Used for most of the first 200 extrasolar planet detections// Currently best-suited to find Jupiter-sized extrasolar planets orbiting close to their stars.

To date, we've found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?

We have not yet been searching for planets at such distances for a long enough time.

In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?

a massive planet that is close to its star

Suppose a planet is discovered by the Doppler technique and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________.

its rotation period

Our modern theory of solar system formation—the nebular theory—successfully accounts for all the major features of our own solar system. However, when the first hot Jupiters were discovered, their existence seemed inconsistent with the nebular theory because this theory predicts that __________.

jovian planets can form only in the cold, outer regions of a solar system

The transit method allows us in principle to find planets around __________.

only a small fraction of stars that have planets

Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that ________.

small planets are more difficult to detect than larger planets.

Based on what we know about our own solar system, the discovery of hot Jupiters came as a surprise to scientists because these planets are __________.

so close to their stars