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Exploring the outer solar system beyond Neptune using stellar occultations

Project description

Beyond Neptune: blocked star light reveals shapes, atmosphere, and rings

Neptune, the outermost planet in our solar system, took shape 4.5 billion years ago, likely forming closer to the Sun and moving to the outer solar system about 4 billion years ago. Neptune and the trans-Neptunian objects (TNOs) (minor planets including Pluto orbiting the Sun beyond Neptune) carry essential information about the formation and evolution of our solar system. The ERC-funded LUCKY STAR project will harness its world-leading methods and instrumentation for analysing stellar occultations (obstructions of a star’s light by an object between the star and observer) to study TNOs to gain insight into rings around small bodies, Pluto’s atmosphere, and TNOs from sub-km to thousand-km size.


The solar system beyond Neptune’s contains largely unaltered material from the primordial circum-solar disk. It also kept the memory of the early planetary migrations, and thus contains essential information on the origin and evolution of our planetary system.

Here I propose to study the Trans-Neptunian Objects (TNOs) using the stellar occultation technique. It consists in observing the passage of remote TNOs in front of those “Lucky Stars”, that reveal shapes, atmosphere and rings of bodies from sub-km to thousand-km in size. Very few teams in the world master this method. The European-led network that I coordinate is now leader in predictions, instrumentation, observations and analysis related to stellar occultations, with innovative approaches and unprecedented results.

In the last decade, our group led the field by discovering rings around the asteroid-like object Chariklo, detecting sub-km TNOs and drastic variations of Pluto’s atmospheric pressure. Based on those noteworthy discoveries and unique skills of ours, I will coordinate the following work packages:

(1) Rings around small bodies - Understand the newly found Chariklo’s rings, tackle the theory of rings’ origins and evolutions around small bodies, discover new ring systems around other bodies.

(2) Very small, sub-km TNOs and Oort Cloud objects - Constrain the collisional history of our early outer solar system, and possibly detect Oort Cloud objects.

(3) Pluto’s atmosphere – Explore Pluto’s atmosphere and its atypical seasonal cycle, search for atmospheres around other TNOs.

(4) Explore specific, large TNOs – Provide their sizes, shapes, albedos and densities.

These programs are timely in view of NASA/New Horizons Pluto flyby in July 2015, and the ESA/GAIA mission expected to provide a greatly improved astrometric catalog release in 2016.

Most of the budget will be dedicated to human power to conduct observations and their analysis, plus the associated travel and telescope time expenses.



Net EU contribution
€ 650 000,00
21 rue de l'ecole de medecine
75006 Paris

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Ile-de-France Ile-de-France Paris
Activity type
Higher or Secondary Education Establishments
Other funding
€ 0,00

Beneficiaries (2)