NASA Picks SpaceX to Launch New Exoplanet Mission

NASA announced on Monday afternoon (Feb. 10) that it has picked SpaceX to launch Pandora, a 716-pound (325-kilogram) satellite designed to help scientists better understand how our understanding of exoplanets' atmospheres are affected by changes in their host stars.  Launch is expected No Earlier Than (NET) "this fall." 

Considering that the 716 lb figure is a small fraction of the lift capability of the Falcon 9, I'll SWAG that it'll be part of a ride share mission of some sort.  Once in orbit...

...the satellite will observe at least 20 known transiting exoplanets — worlds that cross the face of their parent star from the telescope's perspective. It will observe these planets 10 separate times, staring at them for 24 hours on each occasion.

"The satellite will use an innovative 17-inch (45-centimeter)-wide all-aluminum telescope to simultaneously measure the visible and near-infrared brightness of the host star and obtain near-infrared spectra of the transiting planet," NASA officials said in Monday's statement.

This is much like the way the very first exoplanets were discovered in the early 1990s. When the planet transits (passes in front of) the star it orbits, that star dims proportional to the amount of the star's disk that gets blocked out (astronomers refer to this as occultation or being occulted).  As the star's light reaches the telescopes here on Earth, they frequently measure the spectrum of the starlight.  By measuring the spectrum when not occulted and comparing it to when the planet comes between us, the chemical composition of the planet's atmosphere can be deduced.  

Artist's depiction of the drop in measured light as the planet (black circle) occults the star.  The light curve is the bottom middle line with a big "notch" (dip in brightness) during the occultation.  Image credit: NASA

Pandora will be seeking out planets with atmospheres dominated by hydrogen or water.

However, this process depends on the star itself. If the star has regions that are particularly dark or bright, much like sunspot groups or plages seen on our own Sun, they can cause the star’s spectrum to vary over time in ways that can mimic or suppress features in the planet’s spectrum. 

Pandora aims to disentangle the star and planet spectra by monitoring the brightness of the exoplanet’s host star in visible light while simultaneously collecting infrared data. Together, these multiwavelength observations will provide constraints on the star’s spot coverage to separate the star’s spectrum from the planet’s.