Tag: Astronomy

Yet another study has appeared in an attempt to shed light (pun intended) on the mysterious behaviour of Tabby’s Star.

Regular readers of my Space Sunday columns will recognise this name as belonging to the more formally titled KIC 8462852, an F-type main-sequence star located in the constellation Cygnus approximately 1,480 light years from Earth (and which is also called Boyajian’s Star). This star experiences odd periods of dramatic dimming in its light output every so often (with the Kepler Space Observatory recording a loss of up to 22%), with the fluctuations lasting several solar days before it suddenly resumes its normal luminosity as observed from our solar system.

Many theories have been put forward for what is happening – most of which I’ve covered in these pages. They range from theories about vast alien mega-structures – such as a Dyson sphere, to theories of the star itself suffering what is called “avalanche” activity within itself, to ideas involving huge cometary clouds and giant ringed planets,  or just a single giant ringed planet being responsible.

In the most recent study, Extinction and the Dimming of KIC 8462852, a US / Belgian team of scientists suggest that “none of the above” might actually be the correct answer on why the star goes through its irregular dimming cycle. Instead, they argue it is the result of a huge but thin and uneven dust ring rotating slowly around the star.  What makes this theory particularly compelling is that it draws on three independently gathered sets of data in order to form the hypothesis.

The first of these data sources is NASA’s Spitzer Space Telescope, used to gather data on Tabby’s Star in the infra-red wave band during December 2016. The second is the Swift Gamma-Ray Burst mission, which gathered data on the star in the ultraviolet band during the same period of observation; also at the same time, the Belgian AstroLAB IRIS Observatory’s 68-cm (27-in) reflecting telescope gathered data in the visible light spectrum.

What the team found, essentially, was that Tabby’s Star experienced less dimming in the infra-red band than in the ultraviolet – a strong indication that there was a mass of materials, each particle just a few micrometres in diameter, passing between the star and the observatories. While it had been previously suggested the dimming could be the result of an interstellar dust cloud lying somewhere in space between Earth and Tabby’s star, the team discounted this as a possible culprit.

Instead the team took their findings and charted known periods of dimming witnessed with Tabby’s Star and determined a circumstellar dust ring surrounding the star, and rotating around it one every 700 days would actually account for the majority of dimming periods observed from Earth. However, two types of even still do now fit the model.

The first of these is some very short-term “spurts” of dimming which have been noted during 2017. The second is the really large dips in luminosity seen by the Kepler Space Observatory. One potential explanation for the “spurts” of dimming, confirmed through multiple independent observations, is that they might be the result of a cometary cloud orbiting the star and coming between it and Earth. This was actually one of the earliest theories put forward to account for all of Tabby’s Star’s odd behaviour, but it fits the “spurts” of dimming a lot better.

The really big dimming periods, when the star appeared to lose up to 22% of its brightness pose their own problem. They were only observed by Kepler, and have yet to be seen to the same magnitude during any other period of observation, making quantifying them hard. Kepler itself is now studying stars in another portion of the galaxy, so cannot be used to further observe Tabby’s Star to see if such huge dips can again be seen.

Thus, there may yet be another mystery to Tabby’s Star waiting to be solved – or other theories on the fluctuating brightness which may yet be put forward. But for now, the circumstellar dust ring seems to be the most fitting explanation for much of the star’s odd behaviour.

The Moon’s Ancient Atmosphere

That’s the startling conclusion of a new study, supported by NASA’s Solar System Exploration Research Virtual Institute, and recently published in Earth and Planetary Science Letters.

That the Moon was subject to intense volcanic activity in its early history is evidenced by the massive  volcanic basalt maria (“seas”) on its surface. From Earth, these form the dark patches and patterns we can see with the naked eye. They were created three to four billion years ago, when the interior of the Moon was still hot and generating magmatic plumes. In places, these broke through the lunar crust, flowing outwards for hundreds of kilometres. Analysis of rock sample returned to Earth by the Apollo astronauts has long revealed these lava flows carried with them gases like carbon monoxide and the ingredients for water, sulphur, and other volatile elements.

In the study, work, Dr. Debra H. Needham, Research Scientist of NASA Marshall Space Flight Centre, and Dr. David A. Kring, Senior Staff Scientist, at the Lunar and Planetary Institute (LPI), used the amounts of trace gases and volatiles in the Apollo samples as a baseline for calculating the probable amount of gases released during those ancient lunar eruptions. Their findings suggest that the gases were released is sufficient quantities over a long enough period of time, reaching its peak around 3.5 billion years ago, to form a transient  lunar atmosphere. It then persisted for about 70 million years after the volcanic activity ended, before the bulk of the gases were lost to space.

The two largest pulses of gases were produced when lava seas filled the Serenitatis and Imbrium basins about 3.8 and 3.5 billion years ago, respectively. The margins of those lava seas were explored by astronauts of the Apollo 15 and 17 missions, who collected the samples that provided the ages of the eruptions.

This new picture of the Moon has important implications for future exploration. The analysis of Needham and Kring quantifies a source of volatiles that may have been trapped from the atmosphere in the cold, permanently shadowed regions near the lunar poles and may well provide a source of ice suitable for a sustained lunar exploration programme. Volatiles trapped in these icy deposits might be used  provide air and fuel for astronauts conducting lunar surface operations.

“We Chose To Go to the Moon, Because That’s What We Were Doing Anyway”

The re-invoked US National Space Council (NSC) held its inaugural meeting n Thursday, October 5th, 2017 at the Smithsonian National Air and Space Museum’s (NASM) Steven F. Udvar-Hazy Centre.

Chaired by the Vice President, the Council was originally  established in 1989 by then-President George H.W. Bush to serve the same purpose as the National Aeronautics and Space Council, which oversaw US space policy between 1958 and 1973. That NSC was disbanded in 1993 by the Clinton administration.

In this first meeting, the NSC sought to overturn NASA’s “Journey to Mars” endeavour in favour of a more focused plan to return to the Moon – or did they?

But how new and bold is this directive?

The reality is, what Pence announced on behalf of the NSC on October 5th and despite all the hurrahs, is pretty much what NASA was already doing anyway, and had been doing since President Obama signed the NASA Authorisation Act of 2010. That is: build the Orion Multi-Purpose Crew Vehicle and the Space Launch System, establish the Deep Space Gateway in cis-lunar space as an “enabler” for lunar missions and missions to Mars, and develop a presence on the Moon while deferring Mars to some nebulous 2030s time frame. The only significant difference is the instruction for NASA to actually flesh-out the lunar outpost element.

On the one hand, this is good, as it means no mass overturning of the apple cart (a favourite past time of incoming administrations)  and a scramble to sort the apples out again. On the other, it still leaves NASA pursuing goals of questionable need – such as the Deep Space Gateway itself. Which, despite all the hype surrounding it, isn’t actually required for either for getting to the Moon or Mars. Rather, it is an objective that’s become fixed in the NASA mindset, and is now being rationalised on the basis that it is part of the mindset, rather than it offering a means to achieve things that cannot be better (and more cost-effectively) achieved through other methods.

What’s in a Name?

At the 68th International Astronautical Congress (IAC) at the end of September, Elon Musk unveiled more of his thinking around sending humans to Mars.

The linchpin of his aspirations is the massive Interstellar Transport System (ITS) rocket SpaceX is developing. This has caused not a few parents some headaches when explaining things to their children, or created a dilemma when explaining the concept in polite company.

It’s not that explaining the ITS concept in complicated. Far from it. Rather, it’s the fact that Musk has chosen to present the ITS launch system using the acronym he originally defined for it: BFR. This, as just about everyone interested in space exploration knows, stands for “big f***ing rocket”. Descriptive yes, given the size of the beast (see right). But suitable for sensitive or young ears? Er, no, possibly not.

So, how does one deal with explaining what “BFR” means to said sensitive / young ears? SpaceX President Gwynne Shotwell recently offered a solution.

While addressing the National Space Council on October 5th, Shotwell – quite probably with a twinkle of humour in his eye –  played on the company’s use of “Falcon” in naming their rockets (the Falcon 9 and Falcon Heavy) to get around the BFR acronym.

“Last week,” he said. “Elon announced — or, basically, gave an update on,” he then paused a bit, before continuing, “the Big Falcon Rocket programme. The Big Falcon Rocket and Big Falcon Spaceship.”

So there you have it, a non-offensive and semi-accurate way to explain “BFR” to the kids!

The 68th International Astronautical Congress (IAC) ran from September 25th to September 29th, 2017 in Adelaide, Australia, and brought forth a plethora of announcements, presentations and updates from all those involved in space exploration.

one of the more attention-grabbing announcements came – unsurprisingly – from Elon Musk and SpaceX. Already leading the way in private sector launches and launch vehicle reusability,  SpaceX has in many respects set the bar for the launch industry as a whole. Musk, meanwhile has raised eyebrows with his longer-term goals, which focus on human missions to Mars and – eventually – the colonisation of the Red Planet. At the September 2016 IAC, he laid the outlines for achieving these goals, and in 2017 he returned to the IAC to offer further updates and insights to the SpaceX approach.

Most surprisingly, given the company’s reliance on it for revenue generation, Musk indicated that he is prepared to phase out all Falcon 9 launch operations, including the yet-to-fly Falcon Heavy, at some point in the near future in order to focus the company on the development and operation of its Interplanetary Transport System (ITS), which Musk still likes to refer to as the BFR (for “Big F***ing Rocket” on account of its overwhelming size).

Fabrication of parts of the first ITS launcher – which is the linchpin for Musk’s Mars ambitions – has been in progress for some time, and SpaceX hope to start on the assembly of the first vehicle in the series in mid-to-late 2018. Musk is now so confident in the vehicle’s development status, he is hoping to have two of the launch vehicles ready to fly cargo missions to Mars during the 2022 launch opportunity – although he emphasised this time frame is “aspirational” rather than a fixed deadline.

This version of the ITS will be slightly scaled-down from the version announced last year, reducing the overall launch height and mass of the vehicle, and the number of main engines it will require – 31 instead of 42. The 2022 mission will have a two-fold purpose: deliver core components required for human operations on Mars to the surface of the planet; located subsurface water / water ice which could be extracted and used to generate oxygen which could be used within the atmosphere of a future base, and as an oxidizer in fuel used by vehicles making the return flight to Earth.

According to Musk, should this mission proceed to plan, it will be followed in 2024 by four craft carrying a mix of equipment, supplies and crews to Mars to commence human exploration of the planet.

All of this is highly ambitious, technically and financially. On the technical front, there are significant issues to be addressed, most notably – but not limited to – that of the radiation threat posed by Galactic Cosmic Rays (GCRs). As I’ve pointed out in past Space Sunday articles on this subject, solar radiation – often seen as “the” radiation threat – can be managed relatively well, simply because it is generally low-energy radiation.

GCRs, however, are high-energy particles which are much harder to deal with: and there is a lot of them in interplanetary space to deal with. Data from the Mars Science Laboratory’s flight to Mars in 2012 revealed that an unprotected astronaut on a similar flight would face the equivalent radiation dose as having a full-body CAT scan every 5-6 days for six months – definitely not a healthy proposition. There are technologies  being developed which can mitigate GCRs, such as such as hydrogenated boron nitride nanotubes (BNNTs), but these are still some way from being available for general use in spacecraft and spacesuit designs. Musk didn’t expand on how SpaceX plan to handle things like GCRs.

He was, however, more forthcoming on how SpaceX would finance the construction and operation of the ITS system. firstly, SpaceX will build up a “stock” of Falcon 9 units which could be used (and re-used) as launchers and components for Falcon Heavy launchers. Secondly, and once available, the revised ITS will be offered as a commercial launch vehicle capable of placing 100 tonnes into low Earth orbit and delivering objects to geostationary orbit or the moon; payloads could be single large items or multiple items. The plan is to use the stock of Falcon boosters through until customers have confidence in the ITS launcher (which will also be reusable) in order to switch over to using it, after which, all Falcon operations will be phased out.

In addition, and with usual Musk showmanship, the entrepreneur indicated further revenue could be obtained by offering sub-orbital aerospace flights between major cities in record time. According to his calculations, he claimed that such flights could ferry customers between Bangkok and Dubai in just 27 minutes, or between Tokyo and Delhi in 30 minutes, using a smaller variant of the ITS.

Quite how these system would work or how the necessary support infrastructure needed to support launch / recovery / refurbishment operations around the globe would be financed was not made clear – nor was the potential cost of tickets.

Continue reading “Space Sunday: Mars visions, gateways and James Webb” →

At 12:55 UT (13:55 BST, 08:55 EST, 05:55 PDT) the very last signal was received from the NASA / ESA Cassini spacecraft as it entered the upper reaches of Saturn’s atmosphere before disintegrating and burning-up. It was received 83 by NASA’s ground station near Canberra, Australia, 83 minutes after being transmitted – by which time the probe had already been destroyed.

At mission control, at the Jet Propulsion Laboratory, operated jointly by NASA and Caltech in Pasadena, California, it was an emotional moment. For many, the mission had been a part of their daily lives for nigh-on 20 years.

“The signal from the spacecraft is gone and, within the next 45 seconds, so will be the spacecraft,” Cassini programme manager Earl Maize announced, his voice catching, to the team gathered in mission control. “I’m going to call this the end of mission.” He then turned to Spacecraft Operations Team manager Julie Webster and hugged her, before giving Linda Spilker, the Cassini Project Scientist a hug as well. That loss of signal came within 30 seconds of the time predicted ahead of Cassini’s final dive.

As I reported last week, The Cassini-Huygens mission has been an incredible voyage of discovery, revealing so much about Saturn, its rings and retinue of moons, including hints on the evolution of life itself and revealing how moons Titan and Eceladus may have all the right conditions to support basic life while Tethys could – like Enceladus – have a liquid water ocean under its ice.

Cassini’s final approach commenced on September 11th, as it started back towards Saturn having made a final pass between the planet and its rings and looping away from both the week before. Passing by Titan, and once more using the moon’s gravity to push it into the correct trajectory, the probe headed back for its final encounter with Saturn. The Titan fly-by presented a last opportunity to image and study the moon before Cassini’s imaging system was focused on Saturn for the first part of the final approach. Imaging Saturn ended on Thursday, September 14th as the vehicle re-oriented itself to gather as much data on its brief passage into the upper reaches of Saturn’s atmosphere.

As I’ve previously noted in my Cassini mission updates, the primary reason for sending the probe into Saturn’s atmosphere was because it had exhausted almost all of its on-board fuel supplies used to orient itself and to adjust its flight through the Saturnian system, and the mission team didn’t want to leave the probe tumbling around Saturn’s moons where it might one day impact one of them and contaminate it with both Earthly microbes which may be dormant inside the vehicle, and which radioactive debris from its electrical power generators.

However, an alternative would have been to use the last of the vehicle’s fuel to boost it away from Saturn and out into space, but the scientific return promised by a final plunge into the planet was too good to refuse. “Saturn was so compelling, so exciting, and the mission we finally came up with was so rich scientifically that we just couldn’t — we had to finish up at Saturn, not some place else.” Earl Maize stated during a press conference after the probe’s fiery end.

There are currently no planned missions that will follow Cassini-Huygens to Saturn, although there are proposals to send missions to Titan. However, while the active part of the mission has come to an end, it’s not an end of the mission’s science.

“We have collected this treasure trove of data, so we have decades of additional work ahead of us,” Linda Spilker, the Cassini Mission Scientist said. “With this fire hose of data coming back basically every day, we have only been able to skim the cream off the top of the best images and data. But imagine how many new discoveries we haven’t made yet! The search for a more complete understanding of the Saturn system continues, and we leave that legacy to those who come after, as we dream of future missions to continue the exploration we began.”

As a closing note – for now – it’s not often that a space mission gains an official music video; but Cassini-Huygen has been a major inspiration for many over the past two decades, it has earned not one, but three official music videos which form a suite of music by three composes: Iniziare (Italian: “to start” by Sleeping At Last, aka Ryan O’Neal), Kanna (Icelandic: “Explore” by Sarah Schachner) and Amaiera (“end” or “stop” by Joseph Trapanese). I’ve embedded the first part below.

SpaceX Launch X-37B

On Thursday, September 7th, a SpaceX Falcon 9 booster launched the US Air Force X-37B secret mini-shuttle into orbit ahead of the Florida coast being hit by hurricane Irma. It marked the 13th Falcon 9 launch of 2017, and the fifth flight overall for the X-37B.

OTv-5 (Orbital Test Vehicle flight 5) saw the automated spaceplane placed into a higher inclination orbit than previous missions – thus expanding the vehicle’s flight envelope. However, in keeping with previous missions, the USAF has remained mostly silent on the mission’s objectives or its intended duration, revealing only that one experiment flying is the Advanced Structurally Embedded Thermal Spreader II (ASETS-II), which will measure the performance of an oscillating heat pipe.

Previous OTV missions have been long-duration flights, with the maiden flight in 2010 lasting 224 days and 9 hours, which each mission lasting longer than the last, with the last mission completed, OTV-4,  totalling 717 days and 20 hours in orbit. The flights have, up until now, alternated between the two known X-37B vehicles, so although it has not been confirmed, it is believed this mission is being carried out by the first X-37B to fly in space.

The launch took place from Kennedy Space Centre’s Launch pad 39A, which SpaceX has leased from the US space agency and refurbished to handle Falcon 9 and Falcon Heavy launches – and which is now liable to be the pad from which the company’s massive ITS super-heavy rocket will depart when it enters operations in the 2020s. After separating from the upper stage and its cargo, the Falcon 9 first stage performed a “burn-back” manoeuvre and flew back to SpaceX’s dedicated Landing Zone-1 (LZ-1) at Cape Canaveral Air Force Station alongside Kennedy Space Centre, offering spectators a superb view of the landing.

Continue reading “Space Sunday: the last goodbye, super-Earths and spaceplanes” →

Since the February 2017 announcement on the discovery of seven rocky planets orbiting the nearby red dwarf star TRAPPIST-1, multiple studies have been conducted to ascertain whether any of the planets might harbour conditions suitable for life. The nature of their parent star would suggest this to be unlikely. However, an international team utilising the Hubble Space Telescope (HST) to study the TRAPPIST-1 system believe they’ve found evidence that some of the planets have the right conditions to allow liquid water to exist.

Vincent Bourrier, from the Observatoire de l’Université de Genève in Switzerland, and his team used the  Space Telescope Imaging Spectrograph (STIS) to study the amount of ultraviolet radiation each of the TRAPPIST-1 planets receives. If there were too much UV light, no water could survive on the surface because the water molecules would break up and escape through the top of the atmosphere as hydrogen and oxygen gas.

The team found that the inner planets in the system – TRAPPIST-1b and 1c – receive so much UV radiation from their sun, they may have lost more than 20 Earth-oceans worth of water in the course of their history, estimated to be between 5.4 and 9.8 billion years old. Thus, they are almost certainly devoid of water, and their surfaces are likely sterile. However, the findings also suggest the outer planets in the system – including the three within TRAPPIST-1’s habitable zone, may have lost less than three Earth-oceans’ worth of water throughout their history, and could possibly still possess liquid water, making them more amenable for life to rise.

As well as suggesting some of the TRAPPIST-1 planets may have liquid water present, the study has broader implications for the potential of other exoplanets harbouring life. Up to 70% of the stars in the Milky Way are believed to by M-class red dwarfs – and the majority of rocky exoplanets thus far found are orbiting such stars. So this study might indicate that many more of the exoplanets orbiting such stars could support liquid water and, perhaps, conditions suitable for life. However Bourrier and his colleagues emphasise that the study is not conclusive, and further research is needed to determine if any of the TRAPPIST-1 planets are actually watery.

SNC Prepares Dream Chaser for Glide Flight Testing and UN Mission

Sierra Nevada Corporation (SNC) carried out a “captive / carry” test of a Dreamer Chaser Cargo vehicle test article on August 31st, 2017. The flight, with the vehicle slung beneath a helicopter forms the first step towards the Dream Chaser Cargo carrying out glide flights and landings.

During the test, SNC collected data on the vehicle’s performance in flight, including operation of radar altimeters, air data probes and other systems that cannot be fully tested on the ground. The captive /  carry test followed a series of ground tests where the vehicle was towed behind a truck down a runway at speeds of up to 100 kph to ascertain its ground handling on landing.

SNC developed Dream Chaser to transport astronauts to and from the ISS. However, NASA selected capsule designs by SpaceX and Boeing. After a protest over the decision, filed with the U.S. Government Accountability Office, failed, SNC turned their attention to other potential uses for Dream Chaser.

One of these has been the development of a cargo variant to service the International Space Station (ISS) alongside existing resupply contractors,  Orbital ATK and SpaceX, and in 2016, NASA confirmed Dream Chaser Cargo has been selected to fly resupply missions to the ISS between 2019 and 2024.

On July 19th, 2017, it was announced that SNC had signed a contract with United Launch Alliance for the first two launches of these resupply missions, using the Atlas 5 552 launch vehicle. The first launch is scheduled for 2020 and the second in 2021, although NASA has yet to formally order any Dream Chaser flights.

A Dream Chaser Cargo vehicle will also be used in 2021 to launch the first United Nations mission into space. The United Nations Office of Outer Space Affairs (UNOOSA) said an agreement between them and SNC to fly the dedicated Dream Chaser mission is part of a broader effort by the office to increase access to space to emerging nations.

The mission will be open to all nations, but with a particular emphasis on those that don’t have the capabilities to fly their own experiments in space. UNOOSA are in the process of soliciting payload proposals with a goal of selecting payloads by early 2018 so that the winning countries have time to build them for a 2021 launch.

Unlike the majority of Dream Chaser Cargo missions, which will focused on ISS resupply work, the UNOOSA flight will see the vehicle placed in orbit around the Earth, and SNC have indicated the vehicle will be capable of operating freely in orbit for extended periods of time, should the UN desire a longer mission.

While billed as the UN’s first space mission, the Dream Chaser flight is part of UNOOSA’s Human Space Technology Initiative, launched in 2010 with the goal of providing developing countries the possibility to access space in microgravity conditions. Currently, the initiative includes two other major projects. The first is a cooperative project with the Japan Aerospace Exploration Agency (JAXA), designed to give developing nations the opportunity to launch cubesats from the ISS. Another programme, to be operated in cooperation with China’s space programme, will allow UN-backed missions to be flown aboard China’s space station, when it becomes operational in 2020.

Continue reading “Space Sunday: water, spaceplanes and clockwork rovers” →