Astronomy Chapter 10 Flashcards

Questions and Answers

What is an extrasolar planet?

A planet that orbits a star that is not our own Sun.

The first confirmed detections of extrasolar planets occurred in __________.

the 1990's

What do the astrometric, Doppler, and transit methods share in common?

They all search for planets by measuring properties of a star rather than of the planets themselves.

The astrometric method looks for planets with careful measurements of a star's __________.

position in the sky Signup and view all the answers

In essence, the Kepler mission searched for extrasolar planets by __________.

monitoring stars for slight dimming that might occur as unseen planets pass in front of them. Signup and view all the answers

Can we determine orbital distances for extrasolar planets using the astrometric, Doppler, or transit methods?

True Signup and view all the answers

Why do we say that the Doppler method gives a planet's 'minimum mass'?

The size of the Doppler shift that we detect depends on the tilt of a planet's orbit. Signup and view all the answers

Which of the following statements is not true about the planets so far discovered around other stars?

Photographs reveal that most of them have atmospheres much like that of Jupiter. Signup and view all the answers

What do we mean by a 'hot Jupiter'?

A planet that is Jupiter-like in size but orbits very close to its star. Signup and view all the answers

Overall, what do current data suggest about planetary types in other planetary systems?

Planets come in a wider range of types than the planets in our solar system. Signup and view all the answers

Based on current data, about what fraction of stars have one or more planets?

At least about 70%. Signup and view all the answers

Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?

Jovian planets can migrate from the orbits in which they are born. Signup and view all the answers

Which of the following might explain the lack of 'water worlds'—small planets made mostly of water or other hydrogen compounds—in our own solar system?

In our solar system, the solar wind did not clear out gas until relatively late. Signup and view all the answers

How is the GAIA mission relevant to the search for extrasolar planets?

It can detect planets through the astrometric method. Signup and view all the answers

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. Signup and view all the answers

Suppose you are using the Doppler method 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. Signup and view all the answers

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. Signup and view all the answers

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

its rotation period Signup and view all the answers

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

only a small fraction of stars that have planets. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

Study Notes

Extrasolar Planets

Extrasolar planets orbit stars beyond our Sun.
First confirmed detections occurred in the 1990s, with a significant discovery around 51 Pegasi in 1995.

Planet Detection Methods

Astrometric, Doppler, and transit methods measure stellar properties rather than the planets themselves.
The astrometric method analyzes a star's position in the sky for the presence of orbiting planets.
Kepler mission identified extrasolar planets by monitoring stars for dimming caused by passing planets.
All three methods provide orbital period information, allowing calculation of a planet's distance using Kepler's third law.

Mass and Size of Extrasolar Planets

The Doppler method provides a planet's "minimum mass," as the detected Doppler shift is influenced by the orbital tilt.
Hot Jupiters are large planets located very close to their stars.
Current data indicates a broader range of planetary types compared to those in our solar system.

Frequency and Formation of Planets

Approximately 70% of stars are estimated to have one or more planets, confirming the commonality of planetary systems.
Discoveries have led to the idea that Jovian planets can migrate from their original orbits during formation.

Characteristics of Extrasolar Planets

The absence of "water worlds" in our solar system may be due to the solar wind’s late clearing of gas.
GAIA mission will potentially discover thousands of planets using the astrometric method.

Observational Effects

Jupiter causes our Sun to move in a small ellipse with a 12-year orbital period, impacting perceptions from alien astronomers.
The Doppler method requires comparing numerous spectra over extended periods to identify planets.

Observing Transiting Planets

A massive, close planet to its star will produce the largest Doppler shift in its star's spectrum.
Detecting a planet via the Doppler method and later discovering transits does not provide information about the planet's rotation period.
The transit method is applicable to a limited fraction of stars that host planets.

Orbital Conclusions

A star moving slightly every four months suggests an orbiting planet is closer than Earth is to the Sun.
Analyzing spectra before and during a planet’s transit can reveal its atmospheric composition.

Size of Known Extrasolar Planets

Few discovered extrasolar planets match Earth's size, likely due to the difficulty of detecting smaller planets.

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Test your knowledge of extrasolar planets with these flashcards covering key definitions and historical milestones. Explore the methods used to detect these distant worlds and understand what makes them unique. Perfect for anyone studying astronomy or preparing for exams.