Space Sunday: reborn stars, icy worlds and air propulsion

A symbiotic X-ray binary of an ageing red giant (l) and relatively young neutron star (r – not to scale). Interaction between the two may have helped the neutron star to be “come back to life”. 

Astronomers have witnessed an extraordinary stellar event – a star “coming back to life” thanks to its nearby neighbour.

The two stars are from different points in the stellar evolutionary process. The “dead” star is a neutron star, all that remains of a massive star  – possibly with 30 times the mass of the Sun – which ended its life in a violent explosion, leaving whatever matter was left so densely packed, a sphere of the material just 10 km (6.25 mi) in diameter could have a mass 1.5 times that of the Sun.

The “donor” star is a red giant. This is a star similar to the Sun which has reached the latter stages of its life. With the hydrogen in its core exhausted, the star has swollen in size as a result of heat overcoming gravity, and has begun thermonuclear fusion of hydrogen in a shell surrounding the core. When this happens, the star sheds stellar material from its outer layers in a solar wind that travels several hundreds of km/sec.

In this particular case, the two stars – red giant and neutron – form what’s called a symbiotic X-ray binary system – one of one 10 such binaries of this kid so far discovered. There are also some oddities about this particular pairing which makes it somewhat unique. For one thing, while most neutron stars spin at several rotations per second, the neutron star in this pairing takes around 2 hours to complete one rotation. In addition, this star has a much stronger magnetic field than is usual for neutron stars, suggesting it is relatively young.

The ESA INTEGRAL observatory was the first to spot the “re-animation” of the neutron star. Credit; ESA

The “re-animation” of the neutron star occurred in late 2017, and is the subject of a paper published in the Journal of Astronomy and Astrophysics. It was spotted by the European Space Agency’s  INTEGRAL mission on August 13th 2017, which detected high-energy emission from the dead stellar core of the neutron star. These emissions were quickly picked-up by other observatories, such as ESA’s  XMM Newton observatory and NASA’s NuSTAR and Swift space telescopes, and a number of ground-based telescopes, confirming the event.

Its discovery has prompted two main questions: what exactly happened, and how long will this process go on? In answering the first question, astronomers believe that as the neutron star is relatively young, it rate of rotation may have been held in check by the solar wind from the red giant. Over time, the interaction between the red giant’s solar wind and the neutron star’s magnetic field resulted in ongoing high-energy emissions from the dead stellar core.

As to whether this it a short-lived phenomenon or the beginning of a long-term relationship, Erik Kuulkers, ESA’s INTEGRAL project scientist, notes:

We haven’t seen this object before in the past 15 years of our observations with INTEGRAL, so we believe we saw the X-rays turning on for the first time. We’ll continue to watch how it behaves in case it is just a long ‘burp’ of winds, but so far we haven’t seen any significant changes.

So for now, we’ll just have to wait and see.

Air-Breathing Electric Thruster Tested

While it is true the that densest part of the Earth’s atmosphere extends to the edge of the mesopause, just 85 km (53 mi), and the Kármán line –  representing the boundary between Earth’s atmosphere and “outer space” sits at 100 km (62 mi) altitude above the surface of the planet – the fact is that Earth’s atmosphere extends much further from Earth – out as far as 10,000 km (6,200 mi) from the planet’s surface.

This means, for example, that the space station, which operates at an altitude of 400-410 km  (250-256 mi) is operating within the thermosphere, and despite the tenuous nature of the atmosphere at that altitude it is subject to drag which requires it periodically boosts its orbit. This atmospheric drag also extends to low-Earth orbit satellites (which operate up to 2,000 km (1,200 mi), requiring they also periodically need to adjust their orbits. The problem here is that while the ISS can be refuelled – satellites in low-Earth orbit have finite supplies of fuel they can use, which can limit their operating lives.

Now – in a world’s first – the European Space Agency has tested an electric thruster was can ingest scarce air molecules from the thermosphere as fuel, potentially allowing satellites in very low orbits around Earth to have greatly extended operating lives.

Ram-Electric Propulsion is a potential means of providing propulsion for low-orbiting satellites uses extremely rare air molecules in the upper reaches of the Earth’s atmosphere as a means to generate electric thrust. Credit: ESA

A test version of the air-breathing thruster (technically referred as Ram-Electric Propulsion) was recently tested in a vacuum chamber simulating the environment at 200 km altitude. In the test, the thruster was initial fired using xenon gas – a common fuel supply for electric thruster systems – generating a distinctive blue-green plume. A “particle flow generator” was then used to simulate the influx of rarefied air molecules into the thruster system as if it were moving in orbit around Earth, causing the exhaust plume to turn a milky-grey – a clear sign the thruster was burning air as propellant, rather than xenon.

Once the initial thruster burn was completed, the thruster was shut down, purged and than restarted a number of times only using the air molecules provided by the “particle flow generator”, proving the engine can be successful fired – and fuel – by upper atmosphere trace gases.

Placed in a vacuum chamber simulating the mix of atmospheric gases at 200 km altitude, the thruster was initially fired using xenon gas as a fuel, causing a distinctive blue-green exhaust plume (l). It was then fired – with the aid of a “particle flow generator” to simulate its movement through the upper atmosphere – purely using the available air molecules as a fuel supply (r). Credit: ESA

The test firing is the culmination of almost a decade’s worth of research into electric thruster systems. While there is still a way to go before it is ready for practical use, the approach has the potential to benefit more than just low-Earth orbit satellites.

With minimal adjustment the system could in theory be adapted for use on satellites intended to operate in orbit around Mars or even Titan, both reducing the amounts of on-board propellants such a vehicle would require and increasing the mass allowance for science systems.

Continue reading “Space Sunday: reborn stars, icy worlds and air propulsion”

Aliens, a Quiet Man and celebrating Seanchai’s first decade

Seanchai Library

It’s time to highlight another week of storytelling in Voice by the staff and volunteers at the Seanchai Library. As always, all times SLT, and events are held at the Library’s home at Holly Kai Park, unless otherwise indicated.

Sunday, March 11th, 18:00: The Not-Just-Anybody Family

When Junior Blossom wakes up in the hospital, his last memory is of crouching on the barn roof with cloth wings tied to his arms, and of Maggie and Vern in the yard below, urging him to fly. That had been just before Junior spotted a police car approaching the farm in a cloud of dust.

Meanwhile Pap, the children’s grandfather, sits in disgrace in the city jail. He was arrested for disturbing the peace after his pick-up truck accidentally dumped 2,147 beer and soda cans on Spring Street.

With their mother away on the rodeo circuit, it’s up to Maggie and Vern to find a way to rescue Pap and Junior. How will they solve their family problems?

Join Caledonia Skytower at the Golden Horsehoe for this Magicland Storytime reading of this Betsy Byars classic.

Monday, March 12th 19:00: Sentenced to Prism

Prism is a planet with a uniquely crystalline environment and which supports both silicon and carbon-based life forms. It is a planet where even the tiniest creatures are living jewels.

For some time, the Company has been illegally exploiting Prism, but now all contact has been lost with the research team there, leaving the Company with a problem. Any attempt to launch a rescue mission will draw unwanted attention both to Prism and to the Company’s activities. Something else must done; so they call on the talents of Evan Orgell.

A smart, self-confident and successful problem-solver, Orgell has access to the best equipment available within the Commonwealth. Unfortunately, and as Orgell discovers, Prism is a harsh and hard place – a lot harder than his state-of-the-art environment suit. When that succumbs to the local flora/fauna, Orgell finds himself exposed to the hostile environment and fighting for his survival without any protection, dependent upon little more than his wits.

Then help arrives from an unexpected quarter: a sentient life-form native to Prism calling itself A Surface of Fine Azure-Tinted Reflection With Pyroxin Dendritic Inclusions – which Orgell decides to call “Azure”.

Join Gyro Muggins as he reads a standalone story from Alan Dean Foster’s Humanx Commonwealth series.

Tuesday, March 13th 19:00: Mist Nests

An original story by Aoife Lorenfield.

Wednesday, March 14th 19:00: The Quiet Man

quiet-manReleased in 1952, John Ford’s The Quiet Man is regarded as a classic Irish-American romantic comedy / drama. Starring John Wayne, Maureen O’Hara (and assorted members of their RL families!) and Barry Fitzgerald, it is a popular choice among critics and film-lovers.

The screenplay for the film was drawn in a large part from a short story of the same name originally published in 1933 in the Saturday Evening Post, and penned by Irish author, Maurice Welsh. Together with a number of other short stories by Walsh, The Quiet Man was gathered into a single volume of his short stories, The Quiet Man and Other Stories, which dealt with many recurring characters living in rural Ireland of the 1920s, and set against the backdrop of the civil unrest which affected the country at that time, while examining the complexities and occasional intrigues of life, love and Irish traditions.

Join Caledonia Skytower as she reads Walsh’s original tale of The Quiet Man, Paddy Bawn Enright.

Seanchai’s Volume 10: Celebrating a Decade of Seanchai Library

Part 1 of a special series of events to mark Seanchai Library’s 10th anniversary. See here for the full schedule.

Thursday, March 15th, 19:00: The Architect of Newgrange – Part 1

With Shandon Loring – arrive at the Library on Holly Kai early to teleport to the special setting for the event.

Saturday, March 17th:

11:30: Corwyn Allen & Wald Schridde Play Celtic Music, Live! 

A special celebration at  Ceiliúradh Glen on Holly Kai  (in homage to Glens na hEirean in the old West of Ireland Estate).

13:00: The Storyteller’s Path

With Caledonia Skytower at  Ceiliúradh Glen broadcast on Fantasy Faire Radio.

Sunday, March 18th

12:30 Prelude to A Bagpipe Challenge

With Caledonia Skytower at  Ceiliúradh Glen followed at 13:00-14:00 by Beyond Loud – music with Elrik Merlin, Gabrielle Riel, and Ktahdn Vesivino broadcast on Radio Riel Main Stream.


Please check with the Seanchai Library’s blog for updates and for additions or changes to the week’s schedule.