Exoplanetary Circumstellar Environments and Disk Explorer ''(EXCEDE)'' is a proposed space telescope for

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

's Explorer program to observe circumstellar protoplanetary and debris discs and study

planet formation The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting t ...

around nearby (within 100 parsecs)

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s of spectral classes M to B. Had it been selected for development, it was proposed to launch in 2019. The spacecraft concept proposed to use a 70 centimeter diameter telescope-mounted coronagraph called ''PIAA (Phase Induced Amplitude Apodized Coronagraph)'' to suppress starlight in order to be able to detect fainter radiation of circumstellar dust. Characterizing constitution of such disks would provide clues for planetary formation (mostly in habitable zones), while already existing

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s can be detected through their interaction with dust disk. The project's Principal Investigator is Glenn Schneider.

Science goals

The science goals of the concept mission are: * Explore the amount of dust in habitable zones * Determining if such a disk interferes with future planet finding missions (dust-scattered starlight causes noise in images of exoplanets) * Determine composition of material delivered to planets: icy and organich-rich particles are important for life. * Determine fraction of massive planets on large orbits * Observe how protoplanetary disks make Solar System-like architectures * Constrain giant planets' composition by measuring their reflectivity. ''EXCEDE'' would be the first to image (giant) exoplanets distances from their stars similar to ours (0.5-7 AU).

References

Space telescopes Explorers Program Exoplanet search projects {{US-spacecraft-stub