Blanc Inter II SIMI 5-6 - Blanc International II - SIMI 5-6 - Environnement, Terre et Espace

Exploring the outer Solar System with stellar occultations – Beyond Neptune II

Beyond Neptune II

Exploring the Solar Sysem beyond Neptune using stellar occultations

A better knowledge of the outer Solar System

Context: caracterize physically the Trans-Neptunian Objects (TNOs). Constrain the models that describe the formation and the evolution of our Solar System. <br /> <br />Goals: (1) provide the shapes of the large TNOs, (2) derive their albedos, densities and rotaitonal states, (3) detect and probe their atmospheres, (4) provide the size distribution of the small TNOs.

Method: (1) predict stellar occultations by large TNO's woth very high angular accuracy. (2) Detect serendepitous occultations by small TNOs using muilti-fibers instrument at high acquisition rate.
Approaches: (1) organize observation campaigns to detect occultations by large TNOs, (2) use the multi-fibers instrument Miosotys, and the data from the satelite COROT to detect small TNOs (km-sized).

Since January 2012, about 50 campaigns to detect occultations by large TNOs. Detections of 6 occultations by Pluton, and 6 occultations by 2003 AZ84, 2002 KX14, Quaoar, Varuna et Sedna.
Observations at Haute Provence Observatory and at Calar Alto with the multi-fibers instrument Miosotys. Analysis of data from the satellite COROT showing the existence of TNOs of kilometric sizes, and providing constraints on their size distribution.

Monitor Pluto's atmosphere before the flyby of the NASA spacecraft New Horizons (July 2015).
Detect an atmosphere around a TNO other than Pluto.
Detect more occultations by large TNOs to provide their shapes.
Develop other multi-fibers instruments to detect more TNOs of kilometric size.

Publication of a letter in Nature (22 Novembre 2012) on the shape et l'albedo de Makemake, the 3rd largest TNO known to date. Upper limit of its atmosphere of about 10 nanobars.

Submission of an article to Astrophys. J. on the shape, density, albedo and upper limit of its atmosphere.

The outer solar system beyond Neptune’s orbit is a relatively unfamiliar world to the human being, and yet it is believed to contain debris of the primordial solar disk, and therefore carries much information about the early solar system.

We propose to study the trans-Neptunian objects (or Edgeworth-Kuiper Belt Objects, EKBO’s), using the stellar occultation method. We have acquired an experience and leadership in that domain, for which very few teams exist world-wide.

In the last three years, we have been able to become leaders in prediction, observations and analysis of stellar occultations by distant solar system objects. We have also developed or acquired state-of-the-art fast and sensitive instruments for future campaigns.

These achievements are illustrated by our successful recent observations of stellar occultations by (20000) Varuna, 2003 AZ84 and dwarf planet Eris, providing shapes, surface properties and atmospheric limits for those bodies, and breaking records as most distant solar sytem objects ever studied by stellar occultations.

In parallel, we have built an innovative multi-fiber high-speed photometer (MIOSOTYS) which may discover new and exciting astrophysical phenomena.

Building on this expertise, we now propose a two-fold project to pursue and amplify those achievements:

One side of the project is the study of the largest EKBO’s using predicted occultations. This will allow us to (a) monitor Pluto’s (and its twin Triton’s) atmospheric seasonal variations over years, (b) improve the orbital elements of Pluto's and other EKBOs’ satellites, (c) measure sizes and shapes of several EKBO’s at sub-kilometric accuracy, thus pinning down fundamental physical parameters such as densities, albedos and rotational states, and (d) discover new EKBO’s with atmospheres.

The other aspect of the project is the detection of serendipitous EKBO occultations, revealing 0.1 to 1km-sized objects during unpredicted events. This would allow us to (a) reconstruct the EKB (and possibly Oort cloud) structure from statistical studies of those occultations and (b) give the size distribution of those small bodies, an important parameter for constraining formation scenarii.

We now want to develop a Fast Multi Object Photometer (UltraPhot) on the ESO Very Large Telescope « Kueyen » at Cerro Paranal, Chile, for simultaneous fast photometry of one hundred stars, in collaboration with our colleagues of the National Tsing Hua University (NTHU) in Taiwan.


Key words: Astronomical Instrumentation, Optical Observations, Trans-Neptunian Objects

Project coordinator

Monsieur Bruno Sicardy (OBSERVATOIRE DE PARIS) – bruno.sicardy@obspm.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LESIA OBSERVATOIRE DE PARIS

Help of the ANR 352,560 euros
Beginning and duration of the scientific project: December 2011 - 36 Months

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