Other Planetary Systems

Detecting Extrasolar Planets  Extrasolar planets are planets orbiting other stars.  We usually detect these planets by the effect they have on a star. This can be difficult, because stars are far away!  Indirect: Measure star’s position, brightness or spectra.  We can also directly detect planets by the light reflected - this requires a new generation of telescopes.  A Sun-like star is about a billion times brighter than the light reflected from its planets.  Planets are close to their stars, relative to the distance from us to the star.  This is like being in San Francisco and trying to see a pinhead 15 meters from a grapefruit in Washington, D.C.  Extrasolar planets are planets orbiting other stars.  We usually detect these planets by the effect they have on a star. This can be difficult, because stars are far away!  Indirect: Measure star’s position, brightness or spectra.  We can also directly detect planets by the light reflected - this requires a new generation of telescopes.  A Sun-like star is about a billion times brighter than the light reflected from its planets.  Planets are close to their stars, relative to the distance from us to the star.  This is like being in San Francisco and trying to see a pinhead 15 meters from a grapefruit in Washington, D.C.

Extrasolar Planetary Systems In the past decade, telescopes and probes launched into space have returned data and images which have led to the discovery of more than a hundred extrasolar planets. This image is the latest showing a planet much larger than Jupiter circling a star about 200 LY distant.

How can a star's motion reveal the presence of planets?

Gravitational Tugs  The Sun's motion around the solar system's center of mass depends on tugs from all the planets.  Astronomers around other stars that measured this motion could determine the masses and orbits of all the planets.  The Sun's motion around the solar system's center of mass depends on tugs from all the planets.  Astronomers around other stars that measured this motion could determine the masses and orbits of all the planets.

Doppler Measurements  Measuring the Doppler shift of light from an object, such as a star, will tell us how fast it is moving towards or away from Earth. To within 1 meter/second!  A periodic Doppler shift will tell us there is a large planet and how fast it orbits the star.  The planets detected so far have been much larger than Earth (and much larger than Jupiter). They have been gas giants orbiting very close to their star.  Measuring the Doppler shift of light from an object, such as a star, will tell us how fast it is moving towards or away from Earth. To within 1 meter/second!  A periodic Doppler shift will tell us there is a large planet and how fast it orbits the star.  The planets detected so far have been much larger than Earth (and much larger than Jupiter). They have been gas giants orbiting very close to their star.

First Extrasolar Planet  Doppler shifts of the star 51 Pegasi indirectly revealed a planet with 4- day orbital period.  This short period means that the planet has a small orbital distance.  This was the first extrasolar planet to be discovered around a Sun- like star (1995).  Doppler shifts of the star 51 Pegasi indirectly revealed a planet with 4- day orbital period.  This short period means that the planet has a small orbital distance.  This was the first extrasolar planet to be discovered around a Sun- like star (1995).

Transits and Eclipses  A transit is when a planet crosses in front of a star.  The resulting eclipse reduces the star's apparent brightness and tells us planet's radius.  No orbital tilt: accurate measurement of planet mass  A transit is when a planet crosses in front of a star.  The resulting eclipse reduces the star's apparent brightness and tells us planet's radius.  No orbital tilt: accurate measurement of planet mass

The Formation of Other Solar Systems  Recent findings have shown other solar systems are forming as we speak. Space telescopes have shown images of dusty disks around nearby stars.  Astronomers theorize that the process that formed our solar system is common in the galaxy and billions of other solar systems may exist.  Theory predicts gas giants form outside the Frost Line for a solar system, and terrestrial planet closer to the star. Huge gast giants orbiting close to stars are thought to have migrated there after they formed.  Recent findings have shown other solar systems are forming as we speak. Space telescopes have shown images of dusty disks around nearby stars.  Astronomers theorize that the process that formed our solar system is common in the galaxy and billions of other solar systems may exist.  Theory predicts gas giants form outside the Frost Line for a solar system, and terrestrial planet closer to the star. Huge gast giants orbiting close to stars are thought to have migrated there after they formed.

Searching For New Worlds Future telescopes will have dramatically increased range and capabilities, potentially detecting earth sized planets in the next decade. The Kepler mission has discovered 3200 candidates (confirming 132) (6/2013). er/main/index.htmlhttp:// er/main/index.html kepler-mission-data-delivered.htmlhttp://astrobiology.com/2013/06/new- kepler-mission-data-delivered.html

Transiting Exoplanet Survey Satellite (TESS)  TESS is the successor to Kepler  Once launched, the telescope would conduct a two-year all- sky survey, looking for transiting exoplanets around nearby, bright stars.  TESS will have 4 wide-angle telescopes and cameras (192 megapixels)  TESS is planned for launch in 2017  TESS is the successor to Kepler  Once launched, the telescope would conduct a two-year all- sky survey, looking for transiting exoplanets around nearby, bright stars.  TESS will have 4 wide-angle telescopes and cameras (192 megapixels)  TESS is planned for launch in 2017