Detecting extrasolar planets under formation
Detecting planets circling other stars is a particularly difficult task. In order to answer fundamental questions about planetary systems, such as their origin, their evolution, and their frequency in the Universe, scientists need to find and study many more extrasolar planets. ALMA provides valuable information on the planetary systems that orbit stars other than the Sun during all stages of evolution.
Millimeter/submillimeter-wave observations offer a number of advantages in the search for extrasolar planets. Multi-antenna millimeter/submillimeter-wave telescope such as ALMA can provide much higher resolving power, or ability to see fine detail, than current optical or infrared telescopes. Moreover, these observations would not be degraded by interference from the "zodiacal light" reflected by interplanetary dust, either in the extrasolar system or our own Solar System.
Another important advantage is that, at millimeter and submillimeter wavelengths, the star's brightness poses less of a problem for observers because, while it is still brighter than a planet, the difference in brightness between the two is far less. Because of the physical nature of the objects themselves, protoplanets in different stages of formation can be easily detected by ALMA.
ALMA is capable of imaging planetary systems in the earliest stages of their formation. It will also be able to detect many more young, low-mass stellar systems and to examine them to determine if they have the disks from which planetary systems are formed. In addition, ALMA could be used to examine the properties of these disks in detail. The properties that could be examined include size, temperature, dust density and chemistry.