Recently Discovered Extra-Solar Planets
- By applying the Doppler technique. Several groups of astronomers
have discovered the radial velocity signature of planets orbiting other stars.
- There are now many times more planets known in other solar systems than there are in our own!
- By and large these planets are all unexpected oddballs.
- Most of the finds are "Jupiters" and "super-Jupiters"
closer than Mercury is to our Sun.
- This result should not be so surprising since
- massive planets are more easily detected (and "Earth's" are
- the "hit rate" is only about 1 in 30 stars.
- Maybe most of the other 29 have solar systems like our
- Solar system formation theorists are scrambling to
think up ways to form giant planets close to their star.
- Most theories require that the giant planets
form several times the distance of the Earth from the Sun. To get them
so close to their stars they must migrate inward due to interactions with the proto-planetary disk.
- Solar systems may form several Jupiters which get
eaten by the Sun. The last surviving one gets stuck at its
final location when the disk dissipates.
- What about us? Our Jupiter is out where Jupiters are supposed to form.
- The oddballs tend to have stars with a higher heavy element abundance than the Sun - implying they may have built planets more efficiently within denser disks causing more migration.
- Our Sun's disk might have been at the low-mass end of the distribution and Jupiter was assembled just as the available material was running out limiting its migration..
- Some of these super-planets are located in the "habitable
- That is, the temperature is just right for liquid water to exist.
- However, giant planets are all atmosphere.
- The existence of several of these inferred extrasolar
planets has been confirmed by observing the dimming of the star's light as
the planet passed in front of the star.
- Such planetary transits require a special edge-on view of the system -- they are thus
- Such events not only confirm the existence of an extrasolar planet
but provide an opportunity to