Asteroid Physical Properties

Ever since the early days of my PhD thesis, I have been involved in the thermal modeling of thermal-infrared observations of near-Earth objects and other asteroids. Such asteroid thermal models simulate the surface temperature distributions of asteroids utilizing some simplifying assumptions and enabling the estimation of physical properties like size and albedo. In the framework of several large-scale Spitzer Space Telescope observing programs, we have observed more than 2000 near-Earth objects and measured their thermal emission to constrain their diameters and albedos. Now that Spitzer has officially retired, we have finalized our observations and analysis, and compiled all of our results in one large data set. This compilation comprises 2204 diameter and geometric albedo estimates for 2132 different near-Earth objects - the largest homogeneous data set of its kind for this population. The results of these efforts are available GitHub. ...

TESS is the Transiting Exoplanet Survey Satellite, which was launched into space by NASA in 2018 to identify faint brightness variations in stars that are characteristic of planets orbiting around and transiting in front of these stars. A rendering of the TESS spacecraft. The instrument consists of four imaging cameras, each covering 24° x 24° of the sky. Over the course of its nominal two-year mission, TESS will monitor more than 200,000 stars with the photometric accuracy necessary to identify exoplanet transits. In order to observe this huge number of stars, TESS points at different “Sectors” in the sky, amounting to a total of 85% of the entire sky. Each Sector spanning 24° x 96° is observed over a period of about one month. ...

The ESA mission Gaia not only observes a good fraction of the stars in the milky way, but also a huge number of asteroids. Gaia Data Release 2 (DR2) is the first data release to include a number of asteroid observations, limited to G magnitudes (no color information) and a pre-selected sample of 14099 asteroids from different populations. For each asteroids, DR2 contains a median number of 9 observations over the first 9 months of the mission. While this limited data set does not allow for deriving the targets’ rotational periods or constraining their taxonomic types, it is useful for a look into the shape distribution of asteroids. ...

Little is known about the physical properties of the smallest NEOs with diameters of less than 10 meters. Due to their small sizes, they are usually very faint and hard to observe. Hence, only a small number of asteroids in this size regime are known and for only very few of those physical properties like diameter and albedo have been measured. However, small NEOs are much more frequent than larger NEOs, making some of these objects easily accessible spacecraft targets and potential impactors. Traditionally, people believed that these small NEOs have formed through collisions and that they are individual slabs of rock, i.e,. monolithic bodies. ...

Plutinos are a subpopulation of the Trans-Neptunian Objects (TNOs), which are pristine and icy objects on the outskirts of the Solar System. The orbits of Plutinos - which are named after their prototype, Pluto - are in 2:3 resonance with Neptune, meaning that by the time a Plutino performs 2 full orbits around the Sun, Neptune performs 3. This “mean motion resonance” provides a high degree of stability to the orbits of Plutinos. Hence, Plutinos are dynamically and physically pristine objects. ...