BYU Physics and Astronomy

The dwarf planet Haumea has two large satellites, Namaka and Hi'iaka, which orbit at relatively large separations. Both moons have significant eccentricities and inclinations in a pattern that is consistent with a past orbital resonance. Based on our analysis, we find that the present system is not consistent with satellite formation close to the primary and tidal evolution through mean-motion resonances. We propose that Namaka experienced only limited tidal evolution, leading to the mutual 8: 3 mean-motion resonance which redistributed eccentricities and inclinations between the moons. This scenario requires that the original orbit of Hi'iaka was mildly eccentric; we propose that this eccentricity was either primordial or acquired through encounters with other trans-Neptunian objects. Both dynamical stability and our preferred tidal evolution model imply that the moons' masses are only about one-half of previously estimated values, suggesting high albedos and low densities. Because the present orbits of the moons strongly suggest formation from a flat disk close to their present locations, we conclude that Hi'iaka and Namaka may be second-generation moons, formed after the breakup of a larger past moon, previously proposed as the parent body of the Haumea family. We derive plausible parameters of that moon, consistent with the current models of Haumea's formation. An interesting implication of this hypothesis is that Hi'iaka and Namaka may orbit retrograde with respect to Haumea's spin. Retrograde orbits of Haumea's moons would be in full agreement with available observations and our dynamical analysis, and could provide a unique confirmation of the "disrupted satellite" scenario for the origin of the family.

We present new planet candidates identified in NASA Kepler Quarter 2 public release data by volunteers engaged in the Planet Hunters citizen science project. The two candidates presented here survive checks for false positives, including examination of the pixel offset to constrain the possibility of a background eclipsing binary. The orbital periods of the planet candidates are 97.46 days (KIC 4552729) and 284.03 (KIC 10005758) days and the modeled planet radii are 5.3 and 3.8R(circle plus). The latter star has an additional known planet candidate with a radius of 5.05R(circle plus) and a period of 134.49 days, which was detected by the Kepler pipeline. The discovery of these candidates illustrates the value of massively distributed volunteer review of the Kepler database to recover candidates which were otherwise uncataloged.

We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate trans-Neptunian objects for the New Horizons spacecraft to fly by during an extended post-Pluto mission. This Neptune Trojan, 2011 HM102, has the highest inclination (29 degrees.4) of any known member of this population. It is intrinsically brighter than any single L5 Jupiter Trojan at H-V similar to 8.18. We have determined its gri colors (a first for any L5 Neptune Trojan), which we find to be similar to the moderately red colors of the L4 Neptune Trojans, suggesting similar surface properties for members of both Trojan clouds. We also present colors derived from archival data for two L4 Neptune Trojans (2006 RJ(103) and 2007 VL305), better refining the overall color distribution of the population. In this document we describe the discovery circumstances, our physical characterization of 2011 HM102, and this object's implications for the Neptune Trojan population overall. Finally, we discuss the prospects for detecting 2011 HM102 from the New Horizons spacecraft during its close approach in mid- to late-2013.

NASA's Kepler Mission has revealed two transiting planets orbiting Kepler-68. Follow-up Doppler measurements have established the mass of the innermost planet and revealed a third Jovian-mass planet orbiting beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit, has M-P = 8.3(-2.4)(+2.2) M-circle plus, R-P = 2.31(-0.09)(+0.06) R-circle plus, and rho(P) = 3.32(-0.98)(+0.86) g cm(-3), giving Kepler-68b a density intermediate between that of the ice giants and Earth. Kepler-68c is Earth-sized, with a radius R-P = 0.953(-0.042)(+0.037) R-circle plus and transits on a 9.6 day orbit; validation of Kepler-68c posed unique challenges. Kepler-68d has an orbital period of 580 +/- 15 days and a minimum mass of M-P sin i = 0.947 +/- 0.035M(J). Power spectra of the Kepler photometry at one minute cadence exhibit a rich and strong set of asteroseismic pulsation modes enabling detailed analysis of the stellar interior. Spectroscopy of the star coupled with asteroseismic modeling of the multiple pulsation modes yield precise measurements of stellar properties, notably T-eff = 5793 +/- 74 K, M-star = 1.079 +/- 0.051 M-circle dot, R-star = 1.243 +/- 0.019 R-circle dot, and rho(star) = 0.7903 +/- 0.0054 g cm(-3), all measured with fractional uncertainties of only a few percent. Models of Kepler-68b suggest that it is likely composed of rock and water, or has a H and He envelope to yield its density similar to 3 g cm(-3).

Since the discovery of the first exoplanets(1,2), it has been known that other planetary systems can look quite unlike our own(3). Until fairly recently, we have been able to probe only the upper range of the planet size distribution(4,5), and, since last year, to detect planets that are the size of Earth(6) or somewhat smaller(7). Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury(8). This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.