Space Sunday: loss, glides and the avalanche model

Piers Sellers ( April 11th, 1955 – December 23rd, 2016): climatologist and astronaut
Piers Sellers ( April 11th, 1955 – December 23rd, 2016): climatologist and astronaut. Credit: NASA

On Friday, December 23rd, news broke that astronaut Piers Sellers had passed away at the age of 61. His name might not be familiar to some, but British-born Sellers quietly achieved a lot both in orbit and here on the ground.

Born in 1955 in Crowborough, Sussex, Sellers held a bachelor’s degree ecological science and a doctorate in biometeorology. He was regarded as an expert on climate change, studying the relationship between the living world and the atmosphere for the better part of two decades starting in 1982, shortly after he and his wife (they later divorced) relocated from the UK to the United States. At that time he joined  NASA’s Goddard Space Flight Centre in Greenbelt, Maryland, working on climate change computer modelling. He then moved to leading the US team developing the multi-national Terra research satellite, regarded as the flagship Earth Observing System (EOS).

A qualified pilot, having trained as an RAF cadet while at college, he maintained his flight status throughout his first ten years in the United States, repeatedly applying for a position in the NASA Astronaut Corps. However, it wasn’t until 1991, when he gained US citizenship that he met all of the criteria to be considered for a place in the Corps, and he was selected for training in 1996.

After completing two years of training, Sellers was initially assigned technical duties in the Astronaut Office Computer Support Branch, followed by service in the Astronaut Office Space Station Branch, which saw him based in Moscow for periods of time, working with Russian colleges as a technical liaison for the development of computer software for the International Space Station (ISS).

Sellers on EVA during STS-121, his second flight into orbit,
Sellers on EVA during STS-121, his second flight into orbit, July 4th through 17th, 2006. Credit: NASA

In all, Sellers flew in space the times, starting with STS-112 (October 7th – 18th, 2002, Space Shuttle Atlantis), during which he logged a total of 19 hours and 41 minutes of extra vehicular activity (EVA) work, assembling elements of the ISS). In 2006, he flew aboard the Space Shuttle Discovery for the Return To Flight Mission, STS-121, of July 4th through 17th. This mission marked the first flight of the shuttle fleet following the tragic loss of the Columbia and all seven crew on board, on February 1st, 2003. Sellers performed three  further EVAs on that mission, testing the 50-foot robotic arm boom extension as a work platform.

His final flight in space came in 2010 with STS-132, when he once again flew aboard Atlantis in what was to have been its final mission (although it actually flew once more, in July 2011). The mission delivered Russian Rassvet Mini-Research Module along with an Integrated Cargo Carrier-Vertical Light Deployable (ICC-VLD) to the ISS. In total, Sellers logged 35 days, 9 hours and 2 minutes in space, including more than 41 hours on six spacewalks.

In 2011, Sellers resigned from the Astronaut Corps to become Deputy Director of Goddard Space Flight Centre’s Sciences and Exploration Directorate, a position he still held at the time of his death, and later the Acting Director for Earth Sciences at Goddard. He was the author of 70 research papers, and in 2011 he was appointed Officer of the Order of the British Empire (OBE) for services to science. In June 2016 he was bestowed the NASA Distinguished Service Medal, while shortly before his death it was announced he would receive e Gen. James E. Hill Lifetime Space Achievement Award, the highest award the Space Foundation can bestow.

Sellers (l) discusses the realities of climate change with Leonardo DiCaprio in the National Geographic documentary, Before The Flood. Credit: National Geographic
Sellers (l) discusses the realities of climate change with Leonardo DiCaprio in the National Geographic documentary, Before The Flood. Credit: National Geographic

At the start of 2016, Sellers revealed he had been diagnosed with stage 4 pancreatic cancer, and chose to do so by way of an article written for The New York Times entitled Cancer and Climate Change. Commenting on his diagnosis in the piece, he wrote:

I’ve no complaints. I’m very grateful for the experiences I’ve had on this planet. As an astronaut I spacewalked 220 miles above the Earth. Floating alongside the International Space Station, I watched hurricanes cartwheel across oceans, the Amazon snake its way to the sea through a brilliant green carpet of forest, and gigantic night-time thunderstorms flash and flare for hundreds of miles along the Equator. From this God’s-eye-view, I saw how fragile and infinitely precious the Earth is. I’m hopeful for its future.

Despite his diagnosis, Sellers continued his work and research almost right up to his death. In October 2016, he appeared with Leonardo DiCaprio in National Geographic’s documentary Before the Flood. He described climate change plainly and simply:

Here are the facts: The climate is warming, We’ve measured it, from the beginning of the industrial revolution to now. It correlates so well with emissions and theory, we know within almost an absolute certainty that it’s us who are causing the warming and the CO2 [carbon dioxide] emissions.

Commenting on Sellers’ passing, NASA Administrator Charles Bowden, himself a veteran of four flights into space, said:

Piers devoted his life to saving the planet. His legacy will be one not only of urgency that the climate is warming but also of hope that we can yet improve humanity’s stewardship of this planet.

Piers Sellers is survived by his ex-wife, his wife of 36 years, Amanda, their son Thomas and daughter Imogen and a grandson, Jack.

Virgin’s VSS Unity Completes Second Unpowered Flight

VSS Unity seen from a chase plane during the December 22nd, 2016 glide flight
VSS Unity seen from a chase plane during the December 22nd, 2016 glide flight

VSS Unity, otherwise known as SpaceShipTwo and built by Virgin Galactic, performed its second unpowered flight test on Thursday, December 22nd – and without the glare of the media.

The sub-orbital spaceplane was lifted aloft by its carrier aircraft, WhiteKnightTwo, departing the Mojave Air and Space Port in California around 13:20 local time. The climb to separation altitude took some 40 minutes, then the Unity was released, and performed a piloted glide back to the space port and a safe landing.

News of the flight only broke after the event, when George Whitesides, chief executive of Virgin Galactic tweeted, “Well done to the pilots and the whole crew. Great way to end the year!”

The company will be entering 2017 with a roster of further unpowered glide tests for SpaceShipTwo, prior to switching to powered flight tests using the vehicle’s entirely new propulsion unit. The precise number of glide flights isn’t known; the company will only commit to saying they’ll carry out as many as are need to complete flight testing.

Some 700 people have now signed-up for flights on the vehicle, which might begin in 2018. The exact price of a seat aboard SpaceShipTwo has never been revealed, but the 700 sign-ups are said to have met the price either in full or have paid a deposit to secure a seat.

Avalanche Model Explains “Tabby’s Star”?

In October I wrote about “Tabby’s Star”, more formally known as KIC 8462852, an F-type main-sequence star located in the constellation Cygnus approximately 1,480 light years from Earth. It came to prominence in 2015 after data gathered by the Kepler exoplanet mission revealed it is experiencing massive and irregular dips in brightness of up to 22% at a time, which last for several days before the star reverts to its “normal” brightness once more.

If you have access to a 15-cm (6-in) or larger telescope you should be able to see "Tabby's Star" if /when Cygnus is above your night-time horizon
If you have access to a 15-cm (6-in) or larger telescope you should be able to see “Tabby’s Star” if /when Cygnus is above your night-time horizon

As I notes at that time, various theories have been put forward to explain the fluctuations, up to and including gigantic alien structures – such as a Dyson Sphere might be responsible for the star’s shifts. Now however, a more “natural” theory is being put forward to account for the changes; and while it may (if right) see an end to the idea of a super-race building the means to harness the total energy output of their star, it is still pretty exotic. In short, “Tabby’s Star” appears to be mimicking what’s known as the avalanche model here on Earth.

The avalanche model essentially states that in regions where large avalanches regularly occur, they are preceded by smaller avalanches – referred to as “crackling noises”, which although they may not be regular, follow a curve of strength and duration, almost leading up to the “big” event.

The significance here is that in studying the much smaller variations in the brightness “Tabby’s Star” between the “big” drops, a team of  scientists at the University of Illinois at Urbana-Champaign have found they almost perfectly reflect the size / duration rhythm found in the “crackling noises” between major avalanche events (“size” in the case of the star being the measurement of comparative dimming).

The fluctuations probably aren't due to alien mega structures, but might they indicate "Tabby's Star" is in a start of transition?
The fluctuations probably aren’t due to alien mega structures, but might they indicate “Tabby’s Star” is in a start of transition?

This is not to say that there is some bizarre form or avalanche occurring on the star; rather than scientists suggest that there is something internal to the star itself which is causing the fluctuations. As well as avalanches, the pattern of smaller events on a growing – if irregular curve – leading to much larger events can be found elsewhere – such as within magnetic systems –  and are generally indicative of a system near a phase transition. In other words, “Tabby’s Star” may be going through some kind of transition from one state to another – although just what that new state might be, if the theory is correct, is still open to speculation. Even more intriguing is the idea that what should be a stable, main-sequence star not too different from our own, is perhaps in a continuous state of transition.