Taking a different look at a familiar star may still yield surprises. Boggs et al. trained the x-ray vision of the NuSTAR observatory on the well-studied supernova 1987A. Core-collapse explosions such as SN 1987A produce a titanium isotope, 44Ti, whose radioactive decay yields hard x-ray emission lines. All the emission associated with 44Ti appears to be from material moving toward us, with none moving away. This implies that the explosion was not symmetric. These findings help to explain the mechanics of SN 1987A and of core-collapse supernovae in general.
However NASA asked JPL’s scientists and engineers to look at the possibility of attaching a lander to the Clipper, which Culberson has encouraged. The top scientists discussed their preliminary results with him this week.
They found that a “hard” lander could crash into the surface of Europa at about 20 mph, and do some good science. It would weigh about 100 kg and add approximately $700 million to the Clipper mission.
A “soft” lander, hitting at less than 5 mph, could carry a 300-kg payload that would do more science. It could sample the surface, do mass spectroscopy, and carry instruments such as a microscope and imaging camera. It would have the best chance of assessing whether life might exist in the oceans beneath the ice.
Allowing the propagation to continue until decay, results in impact (10 km altitude) on 2015 May 08 near 03:17 UTC. The uncertainty is 6 h, based on the rule of thumb of 20 percent of the estimated time remaining to decay, measured from the epoch of the latter of the two TLEs. Taking into account the USAF’s space weather forecast for this period (much lower geomagnetic activity than today, and a small increase in solar flux), moves the time of impact to 05:41 UTC on the same day.
spacex abort test
The cool white dwarf SDSS J124231.07+522626.6 exhibits photospheric absorption lines of eight distinct heavy elements in medium resolution optical spectra, notably including oxygen. The Teff = 13 000 K atmosphere is helium-dominated, but the convection zone contains significant amounts of hydrogen and oxygen. The four most common rock-forming elements (O, Mg, Si, and Fe) account for almost all the accreted mass, totalling at least 1.2 × 1024 g, similar to the mass of Ceres. The time-averaged accretion rate is 2 × 1010 g s−1, one of the highest rates inferred among all known metal-polluted white dwarfs. We note a large oxygen excess, with respect to the most common metal oxides, suggesting that the white dwarf accreted planetary debris with a water content of ≈38 per cent by mass. This star, together with GD 61, GD 16, and GD 362, form a small group of outliers from the known population of evolved planetary systems accreting predominantly dry, rocky debris. This result strengthens the hypothesis that, integrated over the cooling ages of white dwarfs, accretion of water-rich debris from disrupted planetesimals may significantly contribute to the build-up of trace hydrogen observed in a large fraction of helium-dominated white dwarf atmospheres.
Considerable progress has been made in recent years in observations of atmospheric signatures of giant exoplanets, but processes in rocky exoplanets remain largely unknown due to major challenges in observing small planets. Numerous efforts to observe spectra of super-Earths, exoplanets with masses of 1-10 Earth masses, have thus far revealed only featureless spectra. In this paper we report a 4-σ detection of variability in the dayside thermal emission from the transiting super-Earth 55 Cancri e. Dedicated space-based monitoring of the planet in the mid-infrared over eight eclipses revealed the thermal emission from its dayside atmosphere varying by a factor 3.7 between 2012 and 2013. The amplitude and trend of the variability are not explained by potential influence of star spots or by local thermal or compositional changes in the atmosphere over the short span of the observations. The possibility of large scale surface activity due to strong tidal interactions possibly similar to Io, or the presence of circumstellar/circumplanetary material appear plausible and motivate future long-term monitoring of the planet.
Luo and his colleagues examined data from Chandra for 51 quasars that are located at a distance between about 5 billion and 11.5 billion light years from Earth. These quasars were selected because they had unusually weak emission from certain atoms, especially carbon, at ultraviolet wavelengths. About 65% of the quasars in this new study were found to be much fainter in X-rays, by about 40 times on average, than typical quasars.
The weak ultraviolet atomic emission and X-ray fluxes from these objects could be an important clue to the question of how a supermassive black hole pulls in matter. Computer simulations show that, at low inflow rates, matter swirls toward the black hole in a thin disk. However, if the rate of inflow is high, the disk can puff up dramatically, because of pressure from the high radiation, into a torus or donut that surrounds the inner part of the disk.
Also, by the evening of April 28, NORAD updated orbital elements for the Progress M-27M mission, which finally came to a virtual agreement with the previously available Russian parameters: a 188- by 260-kilometer orbit with an inclination 51.65 degrees toward the Equator.
A new initiative is dedicated to the search for life on planets outside our solar system.
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