Today (July 11), the Hayabusa2 spacecraft performed a 2nd touchdown on the surface of asteroid Ryugu. The touchdown occurred at 10:06 JST at the onboard time and was successful
Orphaned Exomoons: Tidal Detachment and Evaporation Following an Exoplanet-Star Collision
Gravitational perturbations on an exoplanet from a massive outer body, such as the Kozai-Lidov mechanism, can pump the exoplanet’s eccentricity up to values that will destroy it via a collision or strong interaction with its parent star. During the final stages of this process, any exomoons orbiting the exoplanet will be detached by the star’s tidal force and placed into orbit around the star. Using ensembles of three and four-body simulations, we demonstrate that while most of these detached bodies either collide with their star or are ejected from the system, a substantial fraction, ~10%, of such “orphaned” exomoons (with initial properties similar to those of the Galilean satellites in our own solar system) will outlive their parent exoplanet. The detached exomoons generally orbit inside the ice line, so that strong radiative heating will evaporate any volatile-rich layers, producing a strong outgassing of gas and dust, analogous to a comet’s perihelion passage. Small dust grains ejected from the exomoon may help generate an opaque cloud surrounding the orbiting body but are quickly removed by radiation blow-out. By contrast, larger solid particles inherit the orbital properties of the parent exomoon, feeding an eccentric disk of solids that drains more gradually onto the star via Poynting-Robertson drag, and which could result in longer-timescale dimming of the star. For characteristic exomoon evaporation times of ~ 1e5-1e6 yr, attenuation of the stellar light arising from one or more out-gassing exomoons provides a promising explanation for both the dipping and secular dimming behavior observed from KIC 8462852 (Boyajian’s Star).
Bennu after Orbital B Insertion
This image of asteroid Bennu was captured on Jun. 13, 2019, shortly after NASA’s OSIRIS-REx spacecraft executed its second orbital insertion maneuver. From the spacecraft’s vantage point in orbit, half of Bennu is sunlit and half is in shadow. Bennu’s largest boulder can also be seen protruding from the southern hemisphere. The image was taken from a distance of 0.4 miles (690 m) above the asteroid’s surface by NavCam 1, one of three navigation cameras that comprise the spacecraft’s TAGCAMS (the Touch-and-Go Camera System) suite. At this distance, details as small as 1.6 ft (0.5 m) across can be resolved in the center of the image.
This second orbital phase, called Orbital B, broke the record for the closest distance a spacecraft has orbited a body in the Solar System. The spacecraft is now in a bound, circular orbit 0.4 miles (680 m) from the asteroid’s surface.
ESO contributes to protecting Earth from dangerous asteroids
The unique capabilities of the SPHERE instrument on ESO’s Very Large Telescope have enabled it to obtain the sharpest images of a double asteroid as it flew by Earth on 25 May. While this double asteroid was not itself a threatening object, scientists used the opportunity to rehearse the response to a hazardous Near-Earth Object (NEO), proving that ESO’s front-line technology could be critical in planetary defence.
Astronomers have put together the largest and most comprehensive “history book” of galaxies into one single image, using 16 years’ worth of observations from NASA’s Hubble Space Telescope.
Prototype of a Future Interstellar Probe was Just Tested on a Balloon
At the University of California, Santa Barbara, researchers with the UCSB Experimental Cosmology Group (ECG) are currently working on ways to achieve the dream of interstellar flight. Under the leadership of Professor Philip Lubin, the group has dedicated a considerable amount of effort towards the creation of an interstellar mission consisting of directed-energy light sail and a wafer-scale spacecraft (WSS) “wafercraft“.
If all goes well, this spacecraft will be able to reach relativistic speeds (a portion of the speed of light) and make it to the nearest star system (Proxima Centauri) within our lifetimes. Recently, the ECG achieved a major milestone by successfully testing a prototype version of their wafercraft (aka. the “StarChip“). This consisted of sending the prototype via balloon into the stratosphere to test its functionality and performance.
Why India’s ASAT Test Was Reckless
India conducted its first successful anti-satellite (ASAT) test, dubbed “Mission Shakti,” on March 27, 2019. Using a so-called PDV Mark II missile, a modified version of India’s Prithvi Defense Vehicle (PDV) anti-ballistic-missile interceptor, India’s Defense Research and Development Organization (DRDO) destroyed the Microsat-r satellite orbiting at 285 kilometers in altitude. Microsat-r (COSPAR designation 2019-006A) was a 740 kilogram satellite launched by India two months earlier to serve as a target for the test.
In the aftermath of the test, accusations quickly emerged — including from NASA administrator Jim Bridenstine — that the debris generated by the test endangered other satellites. India was quick to claim it had acted “responsibly.” The Indian government pointed out that the test was performed at low altitude, below 300 km, in order to avoid creating debris at the altitudes of operational satellites in Low Earth Orbit (many of which orbit at altitudes between 400 and 1200 km).
New Hubble measurements confirm universe is expanding faster than expected
The new measurements, published April 25 in the Astrophysical Journal Letters, reduce the chances that the disparity is an accident from 1 in 3,000 to only 1 in 100,000 and suggest that new physics may be needed to better understand the cosmos.
“This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This is not what we expected,” says Adam Riess, Bloomberg Distinguished Professor of Physics and Astronomy at The Johns Hopkins University, Nobel Laureate and the project’s leader.
The Halo Drive: Fuel-Free Relativistic Propulsion of Large Masses via Recycled Boomerang Photons
Gravitational slingshots around a neutron star in a compact binary have been proposed as a means of accelerating large masses to potentially relativistic speeds. Such a slingshot is attractive since fuel is not expended for the acceleration, however it does entail a spacecraft diving into close proximity of the binary, which could be hazardous. It is proposed here that such a slingshot can be performed remotely using a beam of light which follows a boomerang null geodesic. Using a moving black hole as a gravitational mirror, kinetic energy from the black hole is transferred to the beam of light as a blueshift and upon return the recycled photons not only accelerate, but also add energy to, the spacecraft. It is shown here that this gained energy can be later expended to reach a terminal velocity of approximately 133% the velocity of the black hole. A civilization could exploit black holes as galactic way points but would be difficult to detect remotely, except for an elevated binary merger rate and excess binary eccentricity.
On the Anomalous Acceleration of 1I/2017 U1 `Oumuamua
We show that the P∼8h photometric period and the astrometrically measured Ang∼2.5×10−4cms−2 non-gravitational acceleration (at r∼1.4AU) of the interstellar object 1I/2017 (`Oumuamua) can be explained by a nozzle-like venting of volatiles whose activity migrated to track the sub-solar location on the object’s surface. Adopting the assumption that `Oumuamua was an elongated a×b×c ellipsoid, this model produces a pendulum-like rotation of the body and implies a long semi-axis a∼5AngP2/4π2∼260m. This scale agrees with the independent estimates of `Oumuamua’s size that stem from its measured brightness, assuming an albedo of p∼0.1, appropriate to ices that have undergone long-duration exposure to the interstellar cosmic ray flux. Using ray-tracing, we generate light curves for ellipsoidal bodies that are subject to both physically consistent sub-solar torques and to the time-varying geometry of the Sun-Earth-`Oumuamua configuration. Our synthetic light curves display variations from chaotic tumbling and changing cross-sectional illumination that are consistent with the observations, while avoiding significant secular changes in the photometric periodicity. If our model is correct, `Oumuamua experienced mass loss that wasted ∼10% of its total mass during the ∼100d span of its encounter with the inner Solar System and had an icy composition with a very low [C/O]≲0.003. Our interpretation of `Oumuamua’s behavior is consistent with the hypothesis that it was ejected from either the outer regions of a planetesimal disk after an encounter with an embedded Mp∼MNep planet or from an exo-Oort cloud.
The International Space Station (ISS) is a closed system inhabited by microorganisms originating from life support systems, cargo, and crew that are exposed to unique selective pressures such as microgravity. To date, mandatory microbial monitoring and observational studies of spacecraft and space stations have been conducted by traditional culture methods, although it is known that many microbes cannot be cultured with standard techniques. To fully appreciate the true number and diversity of microbes that survive in the ISS, molecular and culture-based methods were used to assess microbial communities on ISS surfaces. Samples were taken at eight pre-defined locations during three flight missions spanning 14 months and analyzed upon return to Earth.
Engineers designing ESA’s Hera planetary defence mission to the Didymos asteroid pair are developing advanced technology to let the spacecraft steer itself through space, taking a similar approach to self-driving cars.
“If you think self-driving cars are the future on Earth, then Hera is the pioneer of autonomy in deep space,” explains Paolo Martino, lead systems engineer of ESA’s proposed Hera mission. “While the mission is designed to be fully operated manually from ground, the new technology will be tested once the core mission objectives are achieved and higher risks can be taken.”
kreuzaderny