Space is big, really big! Finding new asteroids which are usually dark against the inky blackness of space is harder than looking for a needle in a cosmic haystack. Back in 1991 an astronomer discovered a kilometre wide asteroid which was subsequently found to have a smaller moon half its size. It was given the snappy name of 1991 VH which , after follow up observations was revealed to have a tumbling, chaotic rotation. This was the first binary asteroid that has been seen to exhibit this behaviour. A paper just published suggests that a close encounter with Earth as recently as 12,000 years ago could have started its tumbling motion.
Asteroid 1991 VH was discovered by Robert McNaught at the Siding Spring Observatory. The asteroid was subject to high resolution imaging from Goldstone and the Arecibo Observatory in 2008 and showed a roughly spherical object. There is an equatorial ridge which gives the whole thing the appearance of a classical spinning top. It’s shape is not what makes the system unique, instead it is the chaotic tumbling nature of the binary system.
The Arecibo Radio Telescope Credit: UCFThe satellite of 1991 VH has been dubbed S/2008 (35107) 1 and it was discovered on 27 February 1997 by a team of astronomers at Ondrejov Observatory. It was detected through photometric observations of the system’s dip in brightness caused by the eclipses and occultations as the two components rotate about each other.
The binary asteroid pair have captured attention of astronomers because it comes from a class of asteroids known as Near Earth Binary Asteroids. Usually they consist of an oblate primary asteroid that is rotating rapidly and around it is a tidally locked elongated secondary asteroid. The tidal locking of the system is the result of tidal forces just like those that have tidally locked the Moon to Earth.
In a paper published by Alex J Meyer from the University of Colorado Boulder and the team of researchers discuss that a past close encounter with Earth could have provided the necessary gravitational influence to disturb the binary system. It has been known that near-Earth asteroids develop chaotic orbital; properties at some point in their life. This is due to orbital resonances with some of the outermost gas giants and on occasions close passages by terrestrial planets.
The team theorise that a single close passage by Earth could have been enough to impose a chaotic nature to the asteroids orbit. To facilitate their research, the team undertake a series of Monte-Carlo simulations where a stable binary asteroid is perturbed by a series of different orbital geometries. The resultant orbital parameters from the simulations are then compared with real observations from 1991 VH.
Their results showed that a close fly-by of Earth by 1991 VH could most definitely alter the state. They propose that the flyby would have occurred within the last 100,000 years, possibly as close as within the last 12,000 years. The new altered chaotic state could remain until current day unless further encounters counteract the perturbations.
Source : An Earth Encounter As the Cause of Chaotic Dynamics in Binary Asteroid (35107) 1991VH
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Being trapped in space sounds like the stuff of nightmares. Astronauts on board the International Space Station have on occasion, had their return delayed by weather or equipment malfunction. We find ourselves again, watching and waiting as two astronauts; Juni Williams and Butch Wilmore have been stuck for months instead of their week long mission. The delays came as the Starliner system required fixes to be implemented. NASA successfully fired up 27 of its 28 thrusters in a hot-firing test and now, ground teams are preparing finally, to bring them home.
The Boeing Starliner spacecraft is officially known as the CST-100 Starliner. It was developed by Boeing as part of NASA’s Commercial Crew Program. Its purpose is to transport astronauts to the International Space Station and other low orbit craft. Starliner hit the headlines with its reusable design aimed at reducing costs and increasing launch frequency. It was first launched on 20 December 2019 as an uncrewed test flight to demonstrate docking capability with ISS.
Boeing’s CTS-100 Starliner taking off from Cape Canaveral, Florida, on June 5th, 2024. Credit: NASASince 2019 Starliner has had issues along the way but has largely seen a successful progression to becoming a key part of NASA’s launch capability. Just recently however there have been issues with the manoeuvring jets used to adjust the attitude. Engineering teams at NASA and Boeing have been working on and running tests with Mexico a new configuration. Part of the thruster system controls the flow of helium, these are the helium manifolds and they were opened to allow engineers to monitor any helium supply issues and leaks.
The team ran a hot fire test of the reaction control system jets on 27 July to see if there were any problems with the propulsion system. They test fired 27 out of 28 jets while astronauts Wilmore and Williams sat inside the docked Starliner. The tests involved firing the jets for short bursts, one at a time. They revealed that all thrusters were back to performing well and the helium manifolds were within operational margins that were needed for a return trip from ISS. The engineering teams closed the manifolds ahead of undocking and returning the astronauts home.
The work is not over for the engineering teams however as they are now reviewing data from the tests and from ground based testing at the White Sands Test Facility in New Mexico. Once the review of data is complete, NASA and Boeing will identify a date to return the astronauts.
Meanwhile back on board the ISS Wilmore and Williams wait. They have been checking other Starliner systems in preparation for return, working with other Boeing teams to prepare and have been undertaking pressure tests of their space suits. They have been working alongside Expedition 71 members and have recently helped setup the BioServe centrifuge in the Harmony Module. The centrifuge supports a wide range of biological, physical and materials science projects. Facilitating the separation of substances with different densities it can work with cell cultures, DNA, protein, blood and sedimentary samples.
Source : NASA, Boeing Complete Second Docked Starliner Hot Fire Test
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