chapter 10

Briefly describe the Doppler method. Summarize the evidence that the planet orbiting 51 Pegasi is a hot Jupiter.

-(to search for gravitational tugs) it searches for a star's orbital movement around the center of mass by looking for changing Doppler shifts in its spectrum -the data showed that the planet has about half the mass of Jupiter. Scientists therefore refer to this planet as a hot Jupiter, because it has a Jupiter-like mass but much higher surface temperature.

Briefly describe the astrometric method. What is the GAIA mission?

-(to search for gravitational tugs) the use of very precise measurements of stellar positions in the sky to look for the slight motion caused by orbiting planets -has the abitious goal of performing astrometric obervations of billion stars in our galaxy with an accuracy of 10 microarcseconds, which would enable it to detect thousands of extrasolar planets.

How can gravitational tugs from orbiting planets affect the motion of a star? Explain how alien astronomers could deduce the existence of planets in our solar system by observing the Sun's motion.

-Planets exert gravitational tugs on their star, causing the star to orbit around the system's center of mass. -Alien astronomers could detect this orbital movement of the Sun and therby deduce their existence of Jupiter, even without having observed Jupiter itself.

How does the transit method work? What was the Kepler mission?

-searches for transits and eclipses by carefully monitoring a star system's brightness over an extended period of time. -searched for planetary transits from 2009-2013

Based on current evidence, how common are planetary systems?

....

What are the two current major approaches to detecting extrasolar planets indirectly?

1. Observing the motion of a star to detect the subtle gravitational tugs of orbiting planets 2. Observing changes to a star's brightness that occur when one of its planets passes in front of the star as viewed from Earth.

why are extrasolar planets hard o detect directly?

1. planets are extremely tiny compared to the vast distances between stars. 2. stars are typically a billion time brighter than the light reflected by any orbiting planets, so starlight tend sto overwhelm any planetary light in photographs.

An extraterrestrial astronomer surveying our solar system with the Doppler method could discover the existence of Jupiter with just a few days. (sense or no sense?)

False, because Jupiter's orbital period is 11 years, so the wobble it imposes on the Sun is an 11 year cycle, very difficult to detect over only a few days or months.

Some extrasolar planets are likely to be made mostly of gold. (sense or no sense)

False, we know of no process that enriches gold over other metals

Summarize the key features shown in figure 10.12, and briefly describe the nature of planets that would fit each of the model curves shown on the graph.

Graph compares planetary radius and mass of extrasolar planets to those of Earth and Jupiter. Most planets are centered around 1.0 to 10 times Jupiter's mass and are .8 to 1.6 times Jupiter's radius. ???

Within the next few years, astronomers expect to confirm all the planet detections made with the astrometric and Doppler methods by observing transits of these same planets. (sense or no sense)

Idk maybe?????

What is planetary migration, and how may it account for the surprising orbits of many extrasolar planets?

It is when a planet forms away from a star and becomes a gas giant similar to that of jupiter, and slowly over time, spirals into the star until it reaches a closer orbit or collides with the star all together.

What fraction of extrasolar planets could in principle be detected by the transit method?

Less than 1 %

Briefly summarize the planetary properties we can measure with current detection methods.

Orbital Period and Distance: the major detection methods all tell us orbital period, from which we can calculate orbital distance. Orbital Eccentricity: we can measure the eccentricity with the Doppler and astrometric methods. Planetary Mass: A more massive planet will cause its star to move at higher velocity around the center of mass. Planetary Size: Transit observations can detect the size/radius Planetary Density: Can be given with transit method size and dopplers method with mass Atmospeheric Composition and Temperature: ....

Some extrasolar planets are likely to be made mostly of water. (sense or no sense)

True some planets with water have been discovered

Current evidence suggests that there could be 100 million or more planets in the Milky Way Galaxy. (sense or no sense)

True, results from Doppler and transit studies already hint that planets are at least as common as stars in our galaxy

Summarize the current state of knowledge about extrasolar planet masses and sizes. Based on the evidence, is it likely that smaller planets or larger planets are more common?

We can mainly see large planets because of our methods of detection, however based models we know that small planets are more common. When the data is adjusted for the fact that our observations are skewed by the methods we use, we find that statistically small worlds are more common.

which method could detect a planet in an orbit that is face-on to the Earth?

astrometic technique

How do the orbits of known extrasolar planets differ from those of planets in our solar system? Why are these orbits surprsing?

extrasoalr planets have a much wider range of propeties than the planets in our solar system. Many orbit closer to their stars. Surprising orbits: have more eccentric orbital paths.

Based on current data, planetary systems appear to be...

extremely rare

which one of the following can the transit method tell us about a planet?

idk size?

What method has detected the most extrsolar planets so far?

the transit method

Whats the best explanation for the location of hot Jupiters?

they formed farther out, like Jupiter but then were forced to move toward their stars by processes like planetary migration by waves or gravitational encounters

To determine a planet's average density, we can use...

transit and Doppler methods together

Which detection method was used by the Kepler mission?

transit method

For a planet of particular mass, the astrometric method will detect the largest stellar motion if the planet orbits...

very close to its star

Based on the model types shown in Figure 10.12, a planet made almost entirely of hydrogen componds would be considered a...

water world