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# Extrasolar Planets - worksheets

## Data

Table 1 - Extrasolar Planetary Data

 Star 51 Pegasi 47 Ursa Major 70 Virginis Spectral Type of star G2 G0 G4 Luminosity (Lo) Mass of star (Mo) Period of planet (yr) distance (AU) T of planet Liquid Water? Mass of planet

## Questions

1. Is the typical mass of these extrasolar planets greater than the mass of the Earth, or less?

2. Judging from their mass, what kind of planet are these extrasolar planets likely to be (terrestrial/rocky or jovian/gas giant)?

3. Are they likely to have a large atmosphere? Explain.

4. When you consider the mass of the planets and the distance they are orbiting their stars, how are these other solar systems different from our own?

5. While some of the extrasolar planets discovered so far are in the right place in their solar system to have liquid water, they are all gas giants. Do you think it would be possible for life to develop on a gas giant? Why/why not?

6. Could life exist in other solar systems if the planets were terrestrial planets, and not gas giants? What factors not already discussed here might impede the formation of life in other solar systems?

### Looking for Extrasolar Planets

1. Actually finding extrasolar planets is an extremely difficult job, requiring great precision and good telescopes. Let's see how difficult it would be to actually see the planet itself. Assume a planet the size of Jupiter. If this planet was orbiting the nearest star, which is about 4 lightyears away (3.8 x 1016 m), what would its angular size be? Show your work.

2. The Hubble telescope, one of the highest resolution instruments astronomers have, can only resolve objects about .2" in diameter. Can Hubble see this planet?

3. Taking an image of a planet and its host star is also difficult because the planet is quite dim compared to the bright star. If we were to go outside of the solar system and take a picture looking back at the solar system, how much dimmer would the flux of an earth-like planet be than the sun? Show your work.

4. Another method for finding extrasolar planets is by watching the planet transit across the face of the star. As a planet orbits around a star, when it crosses in front of the star the light from the star will be dimmed ever so slightly. We can therefore watch stars for slight brightness changes in order to find transiting planets. Again if we were to go outside of the solar system, and look back towards the sun, what fraction of the light from a star the size of the sun would be blocked by a planet a) the size of Jupiter, b) the size of the earth? Show your work.

Last update: 9/30/05

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