Saturday, May 27, 2017

French Nanosatellite to Observe Planet Beta Pictoris b Transiting Its Star

Artist's rendering of PicSat. Image Credit: Paris Observatory/LESIA

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 lbs. (3.57 kilograms), PicSat is a three-unit CubeSat with dimensions of 11.8 x 3.93 x 3.93 inches (30 x 10 x 10 centimeters). The satellite is equipped in a 2-inch 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 on a folding mirror. The light is then injected into the single-mode 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 the satellite jitter,” Sylvestre Lacour, Principal Investigator of PicSat at LESIA, told Astrowatch.net.

A telescope in such configuration allows 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 the 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 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.

PicSat nanosatellite with its solar panels deployed. Photo Credit: Paris Observatory/LESIA
PicSat nanosatellite with its solar panels deployed. Photo Credit: Paris Observatory/LESIA

Discovered in 2008 by 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 20-21 years at a distance of about 9.2 AU from the host. 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 as it avoids atmospheric disturbances, as well as the day and night cycle. Such precision photometry observations could also reveal the details about the structure of Beta Pictoris’ debris disk.

PicSat is expected to be launch this year. It was initially scheduled to be lifted off by India’s PSLV rocket in late June 2017, however it was put on hold as the satellite is not ready yet for the launch. The team now eyes September as the most possible date for the start of the mission.

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