The mass and density of the dwarf planet (225088) 2007 OR10

The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e$\approx$0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused by the Kozai mechanism. Dynamical considerations also suggest that the moon is small, D$_{eff}$ $<$ 100 km. Based on the newly determined system mass of 1.75x10$^{21}$ kg, 2007 OR10 is the fifth most massive dwarf planet after Eris, Pluto, Haumea and Makemake. The newly determined orbit has also been considered as an additional option in our radiometric analysis, provided that the moon orbits in the equatorial plane of the primary. Assuming a spherical shape for the primary this approach provides a size of 1230$\pm$50 km, with a slight dependence on the satellite orbit orientation and primary rotation rate chosen, and a bulk density of 1.75$\pm$0.07 g cm$^{-3}$ for the primary. A previous size estimate that assumed an equator-on configuration (1535$^{+75}_{-225}$ km) would provide a density of 0.92$^{+0.46}_{-0.14}$ g cm$^{-3}$, unexpectedly low for a 1000 km-sized dwarf planet.Comment: Accepted for publication in Icaru

Measurement of D/H and 13C/12C Ratios in Methane Ice on Eris and Makemake: Evidence for Internal Activity

James Webb Space Telescope's NIRSpec infrared imaging spectrometer observed the outer solar system dwarf planets Eris and Makemake in reflected sunlight at wavelengths spanning 1 through 5 microns. Both objects have high albedo surfaces that are rich in methane ice, with a texture that permits long optical path lengths through the ice for solar photons. There is evidence for N2 ice absorption around 4.2 um on Eris, though not on Makemake. No CO ice absorption is seen at 4.67 um on either body. For the first time, absorption bands of two heavy isotopologues of methane are observed at 2.615 um (13CH4), 4.33 um (12CH3D), and 4.57 um (12CH3D). These bands enable us to measure D/H ratios of (2.5 +/- 0.5) x 10-4 and (2.9 +/- 0.6) x 10-4, along with 13C/12C ratios of 0.012 +/- 0.002 and 0.010 +/- 0.003 in the surface methane ices of Eris and Makemake, respectively. The measured D/H ratios are much lower than that of presumably primordial methane in comet 67P/Churyumov-Gerasimenko, but they are similar to D/H ratios in water in many comets and larger outer solar system objects. This similarity suggests that the hydrogen atoms in methane on Eris and Makemake originated from water, indicative of geochemical processes in past or even ongoing hot environments in their deep interiors. The 13C/12C ratios are consistent with commonly observed solar system values, suggesting no substantial enrichment in 13C as could happen if the methane currently on their surfaces was the residue of a much larger inventory that had mostly been lost to space. Possible explanations include geologically recent outgassing from the interiors as well as processes that cycle the surface methane inventory to keep the uppermost surfaces refreshed

Natural sciences for schoolteachers. Lesson 2: Earth in the Universe

Apuntes de Ciencias Naturales para Maestros. Curso 2017-2018. Grado de Maestro/a en Educación Primaria / Grado de Maestro/a en Educación Infantil. Este documento forma parte del material docente programado mediante la ayuda del Servei de Política Lingüística de la Universitat de València.La asignatura Ciencias Naturales para Maestros tiene como objetivo principal que los y las estudiantes del Grado de Maestro/a en Educación Primaria y del Grado de Maestro/a en Educación Infantil completen su formación básica en esta disciplina científica y mejoren su capacitación como educadores y educadoras. Es imprescindible que los maestros y las maestras posean los conocimientos básicos de ciencias naturales necesarios para ejercer su profesión; que conozcan y comprendan el papel de la ciencia y de la tecnología en el progreso de la humanidad; y que adquieran interés por la ciencia para que, a través de su labor profesional, puedan a su vez despertarlo en sus alumnos y alumnas y mejoren con él su aprendizaje.The main objective of the subject Natural Sciences for Teachers is that students of the Degree in Primary School Education and the Degree in Preschool Education complete their basic training in this scientific discipline improving their training as educators. It is essential that teachers possess the basic knowledge of natural sciences which is needed to teach; understand the role of science and technology in human progress; and become interested in science so that, through their teaching, can arouse their students’ interest, and thus improve their learning