A fourth planet orbitingυ Andromedae

Planet–Planet Scattering in Upsilon Andromedae

Doppler spectroscopy has detected 136 planets around nearby stars. A major puzzle is why their orbits are highly eccentric, while all planets in our Solar System are on nearly circular orbits, as expected if they formed by accretion processes in a protostellar disk. Several mechanisms have been proposed to generate large eccentricities after planet formation, but so far there has been little ob...

THE AGE OF THE DIRECTLY IMAGED PLANET HOST STAR k ANDROMEDAE DETERMINED FROM INTERFEROMETRIC OBSERVATIONS

κ Andromedae, an early-type star that hosts a directly imaged low-mass companion, is expected to be oblate due to its rapid rotational velocity (v sin i=∼162 km s). We observed the star with the CHARA Array’s optical beam combiner, PAVO, measuring its size at multiple orientations and determining its oblateness. The interferometric measurements, combined with photometry and this v sin i value a...

The Dwarf Nova Pq Andromedae

Habitability in the Upsilon Andromedae System

We investigate the habitability of the Upsilon Andromedae planetary system as it evolves from a hypothetical four-planet system into what is observed today. We initially considered a fourth planet at a distance of 4.76 AU from the central star. We simulated the dynamics of this system until the fourth planet was ejected due to gravitational interactions with the other planets. Results demonstra...

Apsidal Alignment in Upsilon Andromedae

One of the parameters fitted by Doppler radial velocity measurements of extrasolar planetary systems is ω, the argument of pericenter of a given planet’s orbit referenced to the plane of the sky. Curiously, the ω’s of the outer two planets orbiting Upsilon Andromedae are presently nearly identical: ∆ω ≡ ωD − ωC = 4. 8 ± 4. 8 (1σ). This observation is least surprising if planets C and D occupy o...