Space Sunday: solar systems, flying telescopes, and spaceplanes

An artist’s impression of the Epsilon Eridani system, which might be very similar to our own. Credit: NASA/JPL

To Babylon 5 fans, Epsilon Eridani is (will be?) the home to our “last, best hope for peace”. To some loosely versed in Star Trek lore, it is credited as being the star orbited by the planet Vulcan (although somewhat more officially, Vulcan is placed in the 40 Eridani star system). To astronomers, it is a very Sun-like star some 10.5 light years away, which may be the home of two (or more) planets. And now it appears it is something of a younger version of our own solar system.

The star has long been of interest to astronomers as  the possible location of exoplanets, and in 1987, it appeared as if a Jupiter-sized planet had been discovered orbiting Epsilon Eridani at roughly seven times the distance of the Earth from the Sun, and with an orbital period of some 7 terrestrial years. Initially called Epsilon Eridani b, the planet has been strongly contested over the decades for assorted reasons – even though in 2016 it was granted a formal name: AEgir (sic).

Observations of the system also revealed that the star appears to be surrounded by a cometary ring, somewhat akin to out own Kuiper Belt, and in 2008, the Spitzer Space Telescope revealed that the Epsilon Eridani system may have two major asteroid belts. the first of which correlates to the position of the asteroid belt in our own system, and the second, much broader and denser belt lying roughly at the same distance from the star as orbit of Uranus around the Sun.

The Epsilon Eridani system compared to our own. Credit: NASA/JPL

Like Epsilon Eridani’s planets, the existence of the debris material surrounding the star as two distinct asteroid belts has been contested.Because the Spitzer data failed to indicate a clearly defined band of “warm material” of gas and dust within each of the rings, it has been hypothesised that rather than being two individual belts, they might actually mark the inner and outer boundaries of a single accretion disk.

The difference here is important. If the debris exists as to separate rings of material, it raises the prospect that there are planetary bodies orbiting Epsilon Eridani which may have both helped order the rings and remove debris from the space between them. If there is only one extended accretion disk around the star, it reduces the potential for planets having formed. Now the results of a 2-year study, published in the April edition of Astronomical Journal, sheds new light not only on the asteroid belts, but on the Epislon Eridani system as a whole.

The study, led by Kate Su, an Associate Astronomer with the Steward Observatory at the University of Arizona, used data gathered during a 2015 observation of Epsilon Eridani by the remarkable Stratospheric Observatory For Infrared Astronomy (SOFIA) observation platform developed by NASA and the German Aerospace Centre, DLR. This is a specially modified 747 jet aircraft designed to carry out extended studies of celestial targets.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) observation platform developed by NASA and the German Aerospace Centre, showing the open observation bay at the 2.5 optical telescope. Credit: NASA

Operating at almost 14 kilometres (45,000 ft) altitude, SOFIA flies well above the major distorting effects of Earth’s atmosphere, allowing it to use a 2.5 metre optical telescope with 3 times the resolution power of Spitzer, together with an ultra-sensitive infra-red imaging system called FORCAST, the Faint Object infraRed CAmera for the SOFIA Telescope, to observe targets.

Su and her team used the data gathered by SOFIA’s 2015 observations of Epsilon Eridani, coupled with the Spitzer data and the results of other ground-based observations of the star to build a series of computer models of the system. The results of the models tend to very much confirm that Epsilon Eridani does have two asteroid belts, each with its own distinct “warm band”, and that there could be at least three Jupiter-sized planets within the system helping to organise the rings.

Inside SOFIA. Credit: USRA / NASA / DLR

Not only that, but the study suggest that the Epsilon Eiridani system might be directly comparable to our own as it was not long after the inner planets formed.  If this is the case, the study of Epsilon Eridani could help astronomers gain greater insights into the history of our own Solar System.

Commenting on the study in a press release issued at the time of its publication, co-author Massimo Marengo, an Associate Professor with the Department of Physics & Astronomy at Iowa State University, said:

This star hosts a planetary system currently undergoing the same cataclysmic processes that happened to the solar system in its youth, at the time in which the moon gained most of its craters, Earth acquired the water in its oceans, and the conditions favourable for life on our planet were set.

Su herself added:

The high spatial resolution of SOFIA combined with the unique wavelength coverage and impressive dynamic range of the FORCAST camera allowed us to resolve the warm emission around eps Eri, confirming the model that located the warm material near the Jovian planet’s orbit. Furthermore, a planetary mass object is needed to stop the sheet of dust from the outer zone, similar to Neptune’s role in our solar system. It really is impressive how eps Eri, a much younger version of our solar system, is put together like ours.

It is hoped that Epsilon Eridani will become a focus for studies by the James Webb Space Telescope (JWST), due for launch in 2018, and which will enter operations in 2019.

SpaceShipTwo Completes First Feathering Flight Test

On Monday, May 1st, Virgin Galactic took a significant step towards offering a commercial service to tourists wishing to experience a sub-orbital flight above the Earth, when their SpaceShipTwo vehicle, VSS Unity,  successfully carried out the first flight test of its “feathering” system, a critical part of the vehicle’s flight systems.

An unusual view of the VSS Unity suspended beneath the payload boom between the twin fuselages of the White Knight Two carrier aircraft as the mated pair are rolled out of the Virgin Galactic hanger complex ahead of the May 1st test flight

When activated at the start of the vehicle’s decent from its peak altitude of around 110 kilometres (68 mi), the feathering system “unlocks” the spaceplane’s fuselage from its twin boom tail, allow aerodynamic pressures pitch the body of the vehicle up, increasing the drag it experiences. .This in turn slows the vehicle much earlier in its descent than would otherwise be possible, allowing it to re-enter the denser layers of the atmosphere at much lower speeds, reducing the thermal loads it would otherwise be exposed to.

The first SpaceShipTwo vehicle, VSS Enterprise, was destroyed in a powered test flight on October 31st, 2014, when the feathering system was deployed by the vehicle’s co-pilot during the vehicles ascent, causing it to immediately break-up, killing the co-pilot and severely injuring the pilot. While unpowered, the May 1st flight successfully demonstrated the improved feathering system, and tested the new safeguards designed to prevent the system being incorrectly deployed.

Virgin Galactic hope to start operating their service from 2018, with six passengers at a time paying around US $250,000 each to experience a few minutes of micro-gravity each flight.

A Fist Full of Sand – and a Scarcity Of Life?

NASA’s Mars Science Laboratory (MSL) rover Curiosity is once more “on the road” again, heading up the slope of “Mount Sharp” towards its next science destination, having spent the last three months examining the upper reaches of a dune field dubbed the Bagnold Dunes.

The dunes were first encountered in later 2015 / early 2016, and are significant in that they are active – a combination of the wind and the natural slope of “Mount Sharp” means they are changing / moving over time. Since then, the rover has continued up the mound, exploring other areas of interest, although its route eventually brought it back to the dune field around 1.6 km (one mile) from the point of the original encounter.

Study of the dune field is important, as it gives insight into things like wind erosion on Mars and the role wind plays in distributing minerals over the planet  – including minerals which might help basic life get a foothold on the planet. To help with this, Curiosity has been observing the different dune formations, monitoring wind movements over them, and gathering samples of the material in the dunes for analysis.

In fact, as it resumes its climb higher up “Mount Sharp”, the rover carries with it a fistful of “sand”  taken from the dunes, held within the sample scoop that forms a part of suite of tools on the end of its robotic arm. At some point, the sample will be transferred to the rover’s on-board science suite for detailed analysis. However, this transfer has been deferred for the time being as a result of an issue involving the associated drill feed mechanism.

First revealed five months ago, the problem with the drill feed mechanism is still being investigated, and the concern is that vibrating the arm mechanism at speed – the technique used to transfer samples into the hoppers feeding Curiosity’s on-board science labs – might further adversely affect it before a suitable resolution for the problem can be determined.

Extant life on Mars might actually be harder to locate than previously thought. Credit: NASA/JPL / MSSS

In the meantime, a new study suggests that if there is microbial life on Mars, it is potentially very rare.

Steven Sholes, an astrobiologist at the University of Washington has been examining the amount of carbon monoxide in the Martian atmosphere – which is considerable. On Earth, many microbes can convert carbon monoxide to carbon dioxide to yield energy for growth.

“It’s a free lunch, just sitting in the atmosphere, that microbes could be eating,” he states, but the persistence of carbon monoxide in the atmosphere suggests this in not the case.

Sholes arrived at his conclusion by building a model of how quickly solar radiation generates carbon monoxide in the Martian atmosphere, and how fast the gas diffuses down to the planet’s surface and into subsurface rocks, where any Martian life sheltering from deadly radiation might devour it. Then he used these estimates to calculate the maximum subsurface microbial biomass that could be consuming the carbon monoxide, yet still leave the observed amount of leftovers.

His results were not promising, suggesting that Mars could have less than one microbial cell per cubic centimetre of soil – that’s around a billionth of the equivalent biomass on Earth. While these calculations do not take microbes which might use other metabolic pathways in to consideration and neither confirms nor denies the potential of extant life on Mars, they do suggest is that Mars has 100 times fewer organic cells than the least productive environments on Earth. If so, this would make the already tough job of locating them potentially even harder.

US Air Force X-37B Lands

It is a vehicle shrouded in mystery, and it has now returned to Earth after a record-breaking 718 days in space.

I’ve previously written about the US Air Force X-37B “mini-shuttle” – more correctly called the Orbital Test Vehicle (OTV), built by Boeing and operated by the US Air Force (USAF). An uncrewed vehicle some 8.9 metres (29 ft) in length and with a 4.5 metre (15 ft) wingspan, the purpose of the vehicle has never been fully disclosed. This has led to speculation that the vehicle is some kind of weapons / weapons testing platform, although in rare statements made about it, the USAF has insisted this is not the case, but that the craft is designed to test advanced spaceflight technologies.

The USAF’s X-37B Orbital Test Vehicle (OTV) on the runway at Kennedy Space Centre, May 7th, 2017, being “safed” by a Boeing team in protective suits to guard against harmful fumes and gases given off by the vehicle’s manoeuvring systems. Credit: USAF

The return of the vehicle – launched on Thursday May 20th, 2014 atop an Atlas V booster – marked the successful conclusion of the OTV programme’s fourth flight. The previous three missions, launched between 2010 and the end of 2012, lasted 225, 469 and 675 days respectively, all as classified missions which landed at the USAF’s Vandenberg Air Force Base.

The current mission has been slightly different. For one thing, part of the X-37B’s payload was disclosed prior to its 2014 launch. For another, it returned to Earth to land at the 4 km long shuttle landing runaway at Kennedy Space Centre (KSC), Florida, marking the culmination of Boeing’s work consilidate X-37B operations at KSC, where the company has converted the former space shuttle facility, OPF-1, to enable the USAF to land, recover, refurbish, and re-launch the X-37B.

The vehicle’s return to Earth was publicly announced when sonic booms were heard over Brevard County on Florida’s Space Coast at around 07:45 local time, on May 7th. A few hours after the vehicle had touched-down, a video of its landing was issued by NASA / the USAF.

The unclassified elements of the mission were supplied by NASA, comprising a Hall-effect thruster (a form of ion propulsion) and a materials experiment that exposed almost 100 different materials samples to a space environment for more than 200 days.

The USAF currently has two X-37B vehicles. The first to make a flight into space is expected to be launched on a fifth OTV mission later this year, while this craft, the second of the two vehicles, will be overhauled at the Kennedy Space Centre facilities.

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