week 10 ch 21
The first main sequence star other than our own Sun found to have more than one planet orbiting it is called
Upsilon Andromedae
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 large telescope that detects infrared radiation
Astronomers call a ball of matter that is contracting to become a star
a protostar
Which of these stars will take the SHORTEST time to go from the earliest protostar stage to the main sequence?
a star ten times the mass of our Sun
If you want to find stars that are just being born, where are the best places to search
in giant molecular clouds
The telescope that allowed astronomers to discover most of the planets found with the transit method was called
the Kepler mission
With our current techniques, astronomers can typically only measure the minimum mass of a planet orbiting another star. To know the precise mass of the planet, they must also be able to determine
the angle at which the planet s orbit is tilted relative to us
You are an astronomy graduate student and you are observing the big Orion Nebula from an airplane that has a good-sized infrared telescope built into it (there really is such a plane.) On an infrared image of the Nebula, what would particularly stand out?
the clouds of the nebula that have a lot of dust in them
Which of the following are the small regions that are the embryos of stars (where individual stars are most likely to be born)?
the cores within the clumps of molecular clouds
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 Herbig-Haro (HH) object is
where a jet from a star in the process of being born collides with (and lights up) a nearby cloud of interstellar matter
The first ordinary star (other than our own Sun) around which planets were definitely discovered was:
51 Pegas
The star now called Kepler-444 is 11 billion years old (much older than the Sun) and has five planets orbiting close to it. What has this system taught astronomers about the history of star formation?
If such an old star has planets close to it, where it s really warm, those planets must be made of heavier elements. So heavier elements must have formed before the time this star formed.
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 even for Kepler to detect
Planets in the habitable zone of their stars:
are at a temperature where water can exist as a liquid
Why is it so difficult for astronomers to see new stars in the process of birth?
birth happens very quickly, so it is hard to "catch" stars "in the act" most stars are born inside dusty clouds, which block any light that may be coming from the stars the size of a newly forming star is typically quite small and thus hard to make out protostars which are not yet doing fusion do not give off a lot of visible light all of the above
a planet orbiting a star other than the Sun
exoplanet
a large cold interstellar cloud with a diameter of dozens of light years
giant molecular cloud
a Jupiter sized planet that orbits close to its star
hot Jupiter
Astronomers believe that disks of material will form around protostars that are spinning. Which of the following observed phenomena is a good indication of the presence of a disk around a protostar?
huge pillars of dust, like those seen by the Hubble in the Eagle Nebula
How did astronomers determine that the planet orbiting the star HD 209458 is a gas giant like Jupiter and not made mostly of rocks or metals?
it took more than one of the above measurements to figure out this problem
The closest star to the Sun, Proxima Centauri, was recently found to have a planet in its habitable zone. Proxima Centauri is a cooler red 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
In figuring out the evolutionary tracks on the H-R diagram, astronomers
make model stars on a computer and then follow how their characteristics will change with time
Astronomers were surprised to find so many Jupiter-mass planets so close to their stars. According to their best theories and models, such hot Jupiters
must have formed further out from the star and must have migrated inward early on
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
a very young star still in the process of formation
protostar
the energetic outflow of gas from a star
stellar wind
a planet larger than Earth found around another star
super Earth
To measure how dense a planet is (to know whether it is made of rock or gas and liquid) they must be able to measure the planet s mass from the Doppler shift and
the planet s radius using the transit method
A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram
to the left
when one astronomical object moves in front of another
transit
Astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?
when nuclear fusion reactions begin inside its core