Ch. 21

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 Orion Nebula is

a large cloud of gas and dust illuminated by the light of newly formed stars within it

Planets in the habitable zone of their stars:

are at a temperature where water can exist as a liquid

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 spectral type M. 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

When a star settles down to a stable existence as a main-sequence star, what characteristics determines where on the main sequence in an H-R diagram the star will fall?

its 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

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

The telescope that allowed astronomers to discover most of the planets found with the transit method was called

the Kepler mission

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

A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?

to the left