This site provides information for the community of the Open Time Key Programme (OT KP)
with the Herschel Space Observatory titled "TNOs
are Cool: A Survey of the Transneptunian Region".
Over one thousand objects have so far
been discovered orbiting beyond Neptune. These trans-Neptunian objects (TNOs)
represent the primitive remnants of the planetesimal disk from which the
planets formed and are perhaps analogous to the unseen dust parent-bodies in
debris disks observed around other main-sequence stars. The dynamical and
physical properties of these bodies provide unique and important constraints
on formation and evolution models of the Solar System. While the dynamical
architecture in this region (also known as the Kuiper Belt) is becoming
relatively clear, the physical properties of the objects are still largely
unexplored. In particular, fundamental parameters such as size, albedo,
density and thermal properties are difficult to measure. Measurements of
thermal emission, which peaks at far-IR wavelengths, offer the best means
available to determine the physical properties. While Spitzer has
provided some results, notably revealing a large albedo diversity in this
population, the increased sensitivity of Herschel and its superior
wavelength coverage should permit profound advances in the field. Within our
accepted project we propose to perform radiometric measurements of 139
objects, including 25 known multiple systems. When combined with
measurements of the dust population beyond Neptune (e.g. from the New
Horizons mission to Pluto), our results will provide a benchmark for
understanding the Solar debris disk, and extra-solar ones as well.
Image credits: NASA
Fig. 1. Largest known TNOs of our Solar
Have a look to the latest version of the Poster of "TNOs are Cool" project (PDF).
Fig. 2: Poster of "TNOs are Cool"
Summary of Project Results
Fig. 3: Sizes and albedos derived from the Herschel project (taken from 'Eyes' of Herschel survey enigmatic region beyond Neptune)