French nanosatellite to observe planet Beta Pictoris b transiting its star
A small satellite developed by Paris Observatory is currently undergoing final preparations for its exoplanet-observing mission. The nanosatellite, known as PicSat, will observe the transit of the planet Beta Pictoris b as it passes in front of its host star.
Weighing about 7.87 pounds (3.57 kilograms), PicSat is a three-unit CubeSat with dimensions of 11.8-inch × 3.93-inch × 3.93-inch (30 cm × 10 cm × 10 cm). The satellite is equipped with a 2-inch (5-centimeter) optical telescope, which will allow it to fulfill its scientific goals. This telescope is based on an off-axis parabola, reflecting the light coming from the stars onto a folding mirror. The light is then injected into a single-mode optical fiber, placed in the focal plane of the main parabola. The whole optical system has a focal length of 5.3 inches (13.5 centimeters).
“CubeSats are not very reliable in pointing accuracy (typically, of the order of approximately 0.1 degrees). So we had to engineer a dedicated fine pointing system, as you have in camera for image stabilization. It consists of a piezo-actuator, on which we attached our single mode fiber. We use the piezo to perfectly compensate [for] the satellite jitter,” Sylvestre Lacour, principal investigator of PicSat at LESIA, told Astrowatch.net.
A telescope in such a configuration allows for relatively low-cost monitoring of exoplanetary transits. The scientists of Paris Observatory’s Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), who are managing the PicSat mission, will point the telescope at the star Beta Pictoris – located some 63 light-years away from Earth. They expect to gather essential data about the planet transiting the star, what could provide important insights into planetary formation processes.
“The main objective is to use this planet as a ‘test object’ to constrain the model of planetary formation. It is one of the youngest exoplanet[s] we know (about 20 million years old), and if we can know its mass and its density, we can better constrain how it was formed – by accretion of matter, or gravitational collapse of a cloud,” Lacour said.
Discovered in 2008 by the European Southern Observatory’s (ESO) Very Large Telescope (VLT), Beta Pictoris b is about seven times more massive than Jupiter and has a radius of approximately 1.65 Jupiter radii. The planet orbits its star every 21.6 ±2.7 years at a distance of about 9.2 AU (1 AU = Earth-Sun distance), and it has an 8-hour rotation period. Moreover, the Beta Pictoris system contains a debris disk, which is typical for young planetary systems in the process of forming.
Astronomers estimate that the next transit of Beta Pictoris b in front of its star, as we see it from Earth, will take place between July 2017 and March 2018. Therefore, now is the right time to send a satellite with a proper telescope that could observe the upcoming transit.
“We expect to get the photometry data as the planet passes by in front of its star. It will give us a one-dimensional image of the planet. This will tell us how exactly big it is, does it have rings or moons, and many more,” Lacour said.
PicSat scientists underline that a transit of a young star like Beta Pictoris b, orbiting a bright star, is a unique opportunity to obtain crucial astronomical data. This requires continuous photometric monitoring of the star that only a telescope in space can achieve because it avoids atmospheric disturbances as well as the day and night cycle. Such precision photometry observations could also reveal the details regarding the structure of Beta Pictoris’ debris disk.
PicSat is expected to be launched this year. It was initially scheduled to be lofted into orbit by India’s PSLV rocket in late June 2017; however, it was put on hold as the satellite is not yet ready for launch. The team now eyes sometime in September 2017 as a possible date for the start of the mission.
Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.