extrasolar planets or exoplanets

Since the early 1990s, astronomers have discovered other solar systems, with planets orbiting stars other than our own Sun. These are called "extrasolar planets" or simply exoplanets (see Figure 1.1). Exoplanets are not in our solar system, but are found in other solar systems. Some extrasolar planets have been directly imaged, but most have been discovered by indirect methods. One technique involves detecting the very slight motion of a star periodically moving toward and away from us along our line-of-sight (also known as a stars "radial velocity"). This periodic motion can be attributed to the gravitational pull of a planet or, sometimes, another star orbiting the star. A planet may also be identified by measuring a stars brightness over time. A temporary, periodic decrease in light emitted from a star can occur when a planet crosses in front of, or "transits," the star it is orbiting, momentarily blocking out some of the starlight. More than 1800 extrasolar planets have been identified and confirmed and the rate of discovery is increasing rapidly. Click image to the left or use the URL below. URL:


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how do scientists discover an extrasolar planet?

a) the temporary dimming of a star as the planet crosses in front of it.

b) a stars movement toward and away from us along our line of sight.

c) a state-of-the at space telescope.

-->  d) all of these.

even though they are so very far away, scientists are excited to find earth-like planets because they would like to find

-->  a) evidence of intelligent life.

b) evidence of microbial life.

c) a planet that looks like earth.

d) none of these.

there have been more than 1800 exoplanets identified and confirmed.

-->  a) true

b) false

exoplanets orbit a star other than the sun.

-->  a) true

b) false

what does it mean when a planet is in a stars habitable zone?

a) it has oxygen in its atmosphere.

b) it has a day-night cycle and a seasonal cycle that resembles earths.

-->  c) it has the right temperature to have liquid water.

d) all of the above.

if a planet is not centered on the disk of gas surrounding it, it may mean that

a) the planet does not have a spherical shape.

-->  b) there is another planet that is pulling the gas toward it.

c) the gas is not behaving like gas in our solar system.

d) none of the above.

when did scientists start discovering exoplanets?

a) 1898

b) 1890s

-->  c) 1990s

d) 2000

new extrasolar planets are identified very rarely, only about once per decade.

a) true

-->  b) false

scientists are more likely to detect a giant exoplanet because

-->  a) it has a greater effect on the star it orbits.

b) it appears larger in earth-based telescopes.

c) giant exoplanets are many times more likely to exist.

d) none of these.

according to statistical studies, the milky way galaxy may contain about 100 billion planets.

a) true

-->  b) false

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