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Signs have emerged of dark matter interacting with a force other than gravity. Since the most popular explanation for dark matter is of particles that interact only weakly, if at all, with forces other than gravity, the discovery could either refine our understanding of these interactions or force a complete rethink.
The conclusion comes from the observation of anomalous behavior in a galactic demolition derby zone 1.3 billion light-years away where four galaxies are smashing into each other.
Durham University's Dr. Richard Massey reports in The Monthly Notices of the Royal Astronomical Society that the cluster of galaxies known as Abell 3827 is positioned so that it acts as a gravitational lens for more distant objects. This gave Massey and a team from 15 other institutions the chance to map the distribution of matter though the cluster – the more heavily clumped the matter, the more it will bend distant light.
What is the solar system moon with the densest atmosphere? Most space fans know that the answer is Titan; with a surface atmospheric pressure of 1.4 bars, its air is thicker than Earth's. A few of you might know that Triton's is the next densest. But what's the third? Fourth? Do any other moons even have atmospheres? In fact, they do; and one such atmosphere has just been discovered.
No other moon's atmosphere is quite like Titan's smoggy sky. From space, we can see straight to the other moons' surfaces, with no clouds or haze in the way. Most moons' atmospheres are extremely tenuous, so much so that their constituent molecules never collide with each other. Such collisionless atmospheres are called exospheres. The Moon has an exosphere, as does the planet Mercury.
A very few moons have atmospheres that are dense enough for their gas molecules to collide with each other. This can happen even in a pretty thin atmosphere. Triton's had a surface pressure of 14 microbars when Voyager 2 flew by. As the seasons have progressed on Triton the atmospheric pressure has increased by a factor of three or four, but it's still 20,000 times less dense than Earth's. Still, when air molecules can collide, you can have wind, and even weather. Such an atmosphere can also offer a moon's surface some protection from the particles flung around in giant planet magnetospheres. You can see on Triton how upper-level winds blow the tops of its geysers away. If we're very lucky, we'll see similar features when New Horizons passes Pluto this summer. (Pluto's atmosphere is denser than Triton's.)
Triton color global view
Voyager 2 acquired the images for this high-resolution mosaic of Triton on August 25, 1989. The south pole is at the left; several of Triton's famous south polar geysers are visible. Toward the equator at right, Triton is covered with a strange "cantaloupe terrain".
So which moons other than Titan and Triton have weather? We think there are two. The third-densest atmosphere in the solar system is Io's. From observations with the Submillimeter Array, Arielle Moullet and three coauthors measured sulfur dioxide, sulfur monoxide, and sodium chloride in its air. (Yes, salt is a constituent of Io's atmosphere!) Some of these gases, probably including all of the salt, is fed directly to Io's atmosphere by its constantly erupting volcanoes, but there's too much sulfur dioxide for all of it to be volcanic; some of it has to come from sublimating sulfur dioxide frost.
NASA / JPL / SSI / Gordan Ugarkovic
Animation of Tvashtar and Pele's Plumes
This animation, composed of UV3 frames from the Cassini Imaging Science Subsystem (ISS) taken on January 2, 2001 and magnified by a factor of 2, shows plumes from Io's Tvashtar and Pele Paterae (volcanoes).
At the surface, the peak pressure is around 1.9 nanobars -- that is to say, Earth's atmosphere is 200 million times denser than Io's. But it's still an atmosphere, and a variable one. Io's surface breathes over the course of its day, exhaling sulfur dioxide as it warms in sunlight, and pulling it back down to the surface as it cools at night. The volcanoes heat their local areas, making patches of denser atmosphere and out-flowing winds.
One of the weirdest things in Io's atmosphere is a consequence of it having no magnetic field while being embedded inside Jupiter's. Jupiter's magnetic field sweeps across Io's atmosphere once each Jupiter day, slamming into the back of Io's atmosphere. The magnetic field moves the ions in Io's atmosphere, but not the neutral molecules, so the moving ions crash into the neutral molecules, moving as a current through Io's resistant neutral atmosphere. The interaction of Jupiter's magnetic field with Io's ionosphere has a visible manifestation as a glowing Io footprint within Jupiter's aurora. (For further reading, I recommend this PDF of a PowerPoint presentation on Io's atmosphere that had no name on it -- please speak up in the comments if you know whose presentation it is!)
NASA/ESA, John Clarke (University of Michigan)
Satellite footprints in Jupiter's northern aurora
Auroras are curtains of light resulting from high-energy electrons racing along the planet's magnetic field into the upper atmosphere. The electrons excite atmospheric gases, causing them to glow. The image shows the main oval of the aurora, which is centered on the magnetic north pole, plus more diffuse emissions inside the polar cap. Though the aurora resembles the same phenomenon that crowns Earth's polar regions, the Hubble image shows unique emissions from the magnetic "footprints" of three of Jupiter's largest moons. (These points are reached by following Jupiter's magnetic field from each satellite down to the planet). Auroral footprints can be seen in this image from Io (along the left hand limb), Ganymede (near the center), and Europa (just below and to the right of Ganymede's auroral footprint). These emissions, produced by electric currents generated by the satellites, flow along Jupiter's magnetic field, bouncing in and out of the upper atmosphere. They are unlike anything seen on Earth.
Okay, so how about the fourth densest atmosphere? A new paper in press at Icarus by Nathanial Cunningham and five coauthors suggests that there is one more known collisional atmosphere among the solar system's moons. The fourth densest moon atmosphere in the solar system is (drum roll please):
Callisto.
Callisto?
NASA / JPL / Ted Stryk
Callisto in color from Galileo orbit E11
Galileo captured this global view of Callisto on its 11th orbit of Jupiter, on November 5, 1997.
Cunningham and coauthors used the Cosmic Origins Spectrograph on Hubble to detect the telltale ultraviolet emission of atomic oxygen and determine its abundance. Oxygen probably forms at Callisto when water ice molecules at the surface are split into hydrogen and oxygen atoms; some of the lightweight hydrogen escapes from the atmosphere entirely, leaving the heavier oxygen behind. John Spencer (who was second author on the paper) helped me convert from atmospheric column abundances to surface pressures. Cunningham and coauthors' work suggests that Callisto's leading hemisphere has a surface atmospheric pressure of 26 picobars -- that is, it is 40 billion times less dense than Earth's -- but that the air over its trailing hemisphere may be 10 times denser.
A dynamic atmosphere, even though very thin, slightly shifts our view of Callisto. Callisto is the outermost of the Galilean satellites and also, to use a highly technical term, the deadest. Its gravity field suggests that, unlike the other Galilean moons, it never got warm enough to differentiate into a rocky core and icy mantle, remaining instead a primitive mixture of ice and rock all the way down. A couple of years ago, Jeff Moore postulated that Titan might not have internal geological activity and may just be "Callisto with weather." It turns out that Callisto may have weather! Callisto's atmosphere is more than dense enough for its molecules to collide with each other.
Oxygen atmospheres form at Europa and Ganymede for the same reason that they form at Callisto. But their oxygen atmospheres are a factor of a few less dense than Callisto's, making theirs exospheres, not collisional atmospheres. No wind, and no weather. (At least not at present.)
So here you go: the unlikely set of four solar system moons known to have atmospheres dense enough for weather. In order: Saturn's moon Titan; Neptune's moon Triton; and Jupiter's moons Io and Callisto.
NASA / JPL / SSI / Ted Stryk / Jason Perry / Emily Lakdawalla
Moons with atmospheres
There are four moons in the solar system that are known to have collisional atmospheres. In order of decreasing atmospheric column density, they are: Saturn's Titan, Neptune's Triton, and Jupiter's Io and Callisto.
One final remark. I think that the discovery of a collisonal atmosphere at Callisto is an incredibly cool result, the kind of thing you'd see on all the space blogs. The reason that you don't see it on other blogs is because it hasn't been the subject of a press release, and press releases drive most news reporting. If you read other space sites today, you'll probably read about how the moon formed or an observation of organic molecules in an infant stellar system, two cool results that were the subjects of press releases today. You may even read about the discovery (again) of subsurface ice on Mars. But there are lots of other things being discovered out there. You can find out about them by reading the tables of contents of the main planetary science journals, like Icarus, the Journal of Geophysical Research - Planets, Planetary and Space Science, and others. That's how I found out about Callisto's atmosphere!
After spending more than a month in orbit on the dark side of dwarf planet Ceres, NASA's Dawn spacecraft has captured several views of the sunlit north pole of this intriguing world. These images were taken on April 10 from a distance of 21,000 miles (33,000 kilometers), and they represent the highest-resolution views of Ceres to date.
The United Launch Alliance (ULA) has entered the reusable launcher race with its Next Generation Launch System (NGLS), also known as the Vulcan rocket. This replacement for the current generation of launch systems will incorporate a rocket engine assembly that jettisons from the first stage and is snared in mid-air by a helicopter after reentering the Earth's atmosphere
We present the discovery of a transiting exoplanet candidate in the K2 Field-1 with an orbital period of 9.1457 hours: EPIC 201637175b. The highly variable transit depths, ranging from ∼0% to 1.3%, are suggestive of a planet that is disintegrating via the emission of dusty effluents. We characterize the host star as anM-dwarf with Teff ≃ 3800. We have obtained ground-based transit measurements with several 1-m class telescopes and with the GTC. These observations (1) improve the transit ephemeris; (2) confirm the variable nature of the transit depths; (3) indicate variations in the transit shapes; and (4) demonstrate clearly that at least on one occasion the transit depths were significantly wavelength dependent. The latter three effects tend to indicate extinction of starlight by dust rather than by any combination of solid bodies. The K2 observations yield a folded light curve with lower time resolution but with substantially better statistical precision compared with the ground-based observations. We detect a significant “bump’ just after the transit egress, and a less significant bump just prior to transit ingress. We interpret these bumps in the context of a planet that is not only likely streaming a dust tail behind it, but also has a more prominent leading dust trail that precedes it. This effect is modeled in terms of dust grains that can escape to beyond the planet’s Hill sphere and effectively undergo ‘Roche lobe overflow’, even though the planet’s surface is likely underfilling its Roche lobe by a factor of 2.
Japan plans to launch an unmanned mission to the moon as a stepping stone to a future visit to Mars, officials and local media said Monday.
The Japan Aerospace Exploration Agency (JAXA) unveiled the plan for a moon lander to a council of the cabinet office and the ministry of education, culture, sports science and technology, a JAXA official said.
If successful, Japan will be the fourth country to send an unmanned probe to the moon after Russia, the United States and China.
"This is an initial step and a lot of procedures are still ahead before the plan is formally approved," the official said.
Astronomers have probed deeper than before into a planetary system 130 light-years from Earth. The observations mark the first results of a new exoplanet survey called LEECH (LBT Exozodi Exoplanet Common Hunt), and are published today in the journal Astronomy and Astrophysics.
The planetary system of HR8799, a young star only 30 million years old, was the first to be directly imaged, with three planets found in in 2008 and a fourth one in 2010.
"This star was therefore a target of choice for the LEECH survey, offering the opportunity to acquire new images and better define the dynamical properties of the exoplanets orbiting," said Christian Veillet, director of the Large Binocular Telescope Observatory (LBTO).
NASA's Curiosity Mars rover is continuing science observations while on the move this month. On April 16, the mission passed 10 kilometers (6.214 miles) of total driving since its 2012 landing, including about a fifth of a mile (310 meters) so far this month.
While the Indian Space Research Organisation (ISRO) has put the country in global limelight because of its low-cost mission to Mars, its commercial wing, Antrix, has started witnessing a robust growth with more countries approaching it with offers to launch their satellites.
One such proposal of commercial satellite launch is due for June this year in which three DMC-3 earth observation satellites along with one micro and one nano satellite built by UK's Surrey Satellite Technology (SSTL) will be launched into space.
The mission is designated as PSLV- C28/ DMC-3 which has been taken under a commercial agreement between Antrix Corporation Limited and DMC International Imaging (DMCII), a wholly-owned subsidiary of SSTL.
Noteworthy, Antrix entered into a launch services agreement with a company from US in 2014 for launching their earth observation micro satellite.
This is the first time when Antrix will be launching a US-built satellite on-board PSLV.
Recently, Antrix also entered into a launch services agreement with another company from US for launching seven nano satellites of US on-board PSLV.
We analyze 37 months of Kepler photometry of 2M1938+4603, a binary system with a pulsating hot subdwarf primary and an Mdwarf
companion that shows strong reflection effects.We measured the eclipse timings from more than 16 000 primary and secondary
eclipses and discovered a periodic variation in the timing signal that we ascribe to a third body in the system. We also discovered a
significant long-term trend that may be an evolutionary effect or a hint of more bodies. Upon the assumption that the third body is
orbiting in the same plane as the primary, we establish that it must be a Jupiter-mass object orbiting with a period of 416 days at a
distance of 0.92AU. This mass is the lowest among all tertiary components detected in similar systems.
SpaceX Chief Executive Elon Musk confirmed a throttle issue was the cause of failed landing attempt of a Falcon 9 first stage last week, and that it plans to make another landing attempt in June.
Though there have been tremendous advances in space technology in recent years, when it comes to getting into space, we're still like cavemen trying to get beyond the breakers on a floating log – at least, that's the view of New Zealand-based company Rocket Lab. In the hopes of increasing the number of satellite launches to over 100 a year and placing constellations of small satellites into orbit numbering in the thousands, the company has developed a "battery-powered" rocket engine to lift its Electron launch vehicle at almost a tenth of the cost of conventional boosters.
Liquid rocket engines are hungry beasts that require huge quantities of propellants for every second of flight. To manage this, engines use turbopumps to feed propellants into the combustion chamber. In a conventional design, a centrifugal or axial-flow turbopump is driven by a gas turbine. This has done the job very well since the first rocket turbopumps were developed in the 1940s, but they're complex, heavy affairs that need their own fuel systems to operate.
Rocket Lab's idea for making a lighter, simpler liquid rocket is its Rutherford engine. Named after New Zealand-born physicist Ernest Rutherford, it's an electric turbopump engine that burns a mixture of liquid oxygen and RP-1 rocket fuel, which is a highly refined type of kerosene. Unlike conventional engines, in the Rutherford, the gas-powered turbine to run the pump is replaced with a brushless DC motor and lithium polymer batteries, and provides enough fuel for the Rutherford to generate 4,600 lbf (20,462 N) of thrust and a specific impulse of 327 seconds.
Abstract: We confirm the planetary nature of KOI-372b (aka Kepler object of interest K00372.01), a giant transiting exoplanet orbiting a solar-analog G2V star. The mass of KOI-372b and the eccentricity of its orbit were accurately derived thanks to a series of precise radial velocity measurements obtained with the CAFE spectrograph mounted on the CAHA 2.2-m telescope. A simultaneous fit of the radial-velocity data and Kepler photometry revealed that KOI-372b is a dense Jupiter-like planet with a mass of Mp=3.25 Mjup and a radius of Rp=0.882 Rjup. KOI-372b is moving on a quite eccentric orbit, e=0.172, making a complete revolution around its parent star in 125.6 days. The semi-major axis of the orbit is 0.4937 au, implying that the planet is close to its habitable zone (roughly 0.5 au from it). By analysing the mid-transit times of the 12 transit events of KOI-372b recorded by the Kepler spacecraft, we found a clear transit time variation, which is attributable to the presence of a planet c in a wider orbit. We estimated that KOI-372c has a mass between 0.13 and 0.31 Mjup, also revolving on an eccentric orbit (e=0.17-0.24) in roughly 460 days, at a mean distance of 1.2 au from the host star, within the boundaries of its habitable zone. The analysis of the CAFE spectra revealed a relatively high photospheric lithium content, A(Li)=2.48 dex, suggesting that the parent star is relatively young. From a gyrochronological analysis, we estimate that the age of this planetary system is 1.0 Gyr.
We present the detection and characterization of the transiting warm Jupiter KOI-12b, first identified with Kepler with an orbital period of 17.86 days. We combine the analysis of Kepler photometry with Doppler spectroscopy and line-profile tomography of time-series spectra obtained with the SOPHIE spectrograph to establish its planetary nature and derive its properties. To derive reliable estimates for the uncertainties on the tomographic model parameters, we devised an empirical method to calculate statistically independent error bars on the time-series spectra. KOI-12b has a radius of 1.43±0.13RJup and a 3σ upper mass limit of 10MJup. It orbits a fast-rotating star (vsini⋆ = 60.0±0.9 km s−1) with mass and radius of 1.45±0.09 MSun and 1.63±0.15 RSun, located at 426±40 pc from the Earth. Doppler tomography allowed a higher precision on the obliquity to be reached by comparison with the analysis of the Rossiter-McLaughlin radial velocity anomaly, and we found that KOI-12b lies on a prograde, slightly misaligned orbit with a low sky-projected obliquity λ = 12.6−2.9+3.0∘. The properties of this planetary system, with a 11.4 magnitude host-star, make of KOI-12b a precious target for future atmospheric characterization.
2M1938+4603 (AB)b - Circumbinary planet in a sdB+M dwarf system
A circumbinary planet orbiting a sdB+M system in Kepler's field.
Detection of a planet in the sdB + M dwarf binary system 2M1938+4603
We analyze 37 months of Kepler photometry of 2M1938+4603, a binary system with a pulsating hot subdwarf primary and an Mdwarf
companion that shows strong reflection effects.We measured the eclipse timings from more than 16 000 primary and secondary
eclipses and discovered a periodic variation in the timing signal that we ascribe to a third body in the system. We also discovered a
significant long-term trend that may be an evolutionary effect or a hint of more bodies. Upon the assumption that the third body is
orbiting in the same plane as the primary, we establish that it must be a Jupiter-mass object orbiting with a period of 416 days at a
distance of 0.92AU. This mass is the lowest among all tertiary components detected in similar systems.
2M1938 4603 AB b - Circumbinary planet in a sdB M dwarf system
Titan has deep convective clouds driven by the release of latent from methane condensation. As on Earth, the presence of convective available potential energy (CAPE), which quantifies the amount of energy available through condensation, is required for storms to develop. While CAPE is a requirement for storms, the dynamics, morphology, and longevity of storms on Earth is controlled by both CAPE and wind shear, often expressed as a ratio in the form of the bulk Richardson Number. The impact of CAPE and wind shear on storms in a Titan-like environment are explored through numerical simulation. Model results indicate that Titan storms should respond to changes in the Richardson Number in a manner similar to storms on Earth. Very long-lived storms (>24 h) propagating for 1000 km or more might be possible on Titan when CAPE and wind shear are properly balanced. Some of the simulated storms exhibit dynamics similar to squall lines. Varying amounts of shear in the Titan environment might explain the variety of convective cloud expressions—varying from short-lived single cell storms to longer-lived linear features and large cloud bursts—identified in Cassini orbiter and ground-based observations. The varying amounts and spatial distribution of precipitation, as well as surface winds associated with storms, should have implications on the formation of fluvial and aeolian features and on the exchange of methane with the surface and lakes.
As the Hubble Space Telescope celebrates 25 years in space this week, NASA and its international partners are building an even more powerful tool to look deeper into the universe than ever before.
The James Webb Space Telescope will be 100 times more potent than Hubble, and will launch in 2018 on a mission to give astronomers an unprecedented glimpse at the first galaxies that formed in the early universe.
"JWST will be able to see back to about 200 million years after the Big Bang," NASA said on its website.
