Astronomy Ch 21

Star formation can be triggered by radiation and fast particles from

Young, high-mass stars

The Orion Nebula is

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

A graduate student is given the assignment to find stars with dusty disks around them. What kind of telescope would it be best for her to use for this purpose?

a telescope that detects infrared radiation

If you want to find stars that are just being born, where are the best places to search?

in giant molecular clouds

Which of the following are the small regions that are the "embryos" of stars?

the cores within the clumps of molecular clouds

The radial velocity curve for a star with a large planet seen with its orbit edge-on is shown. At which lettered location could the planet be detected by the transit method?

A(or E)

Exoplanets discovered using the radial velocity technique are most likely to be found in which labeled region in the plot?

E

Easy finds, Separation

Planets closer to their stars, take shorter time to complete their orbit

Easy finds, Mass

Planets that are more massive cause their stars to follow larger faster orbits and cause a doppler shift in their spectrum.

The histogram shows the number of new planets discovered each year up to 2015. The planets in the circle were predominantly discovered by

Radial velocity method

The existence of exoplanets is typically known through

effects on a parent star

Queloz and Mayor

first to discover a planet around a star(51 pegasi)

An astronomer is taking spectra of a star that has a large planet. She makes measurements of the wavelength of the hydrogen-alpha absorption line (reference wavelength 656.3 nm) to identify the radial velocity from the Doppler shift equation shown. When she measures a wavelength of 656.5 nm the star

has a positive radial velocity and is moving away from Earth

Doppler Method

searches for a star's orbital movement around the center of mass by looking for changing doppler shifts in its spectrum(detects massive planets close to stars).

As our part of the early nebula evolved to form our solar system, it

shrank

The radial velocity technique doesn't work well for systems where the

system orbit is seen face-on

When a star is toward us, what happens to its spectrum?

the lines in spectrum show a tiny blueshift

When a star is moving away from us, what happens to its spectrum?

the lines in spectrum show a tiny redshift

To measure how dense a planet is astronomers must be able to measure the planet's mass from the Doppler shift and

the planet's radius using the transit method

Our current theory of planet formation states that planets form as a natural byproduct of star formation. This implies that

there should be very many planets in the Milky Way Galaxy