Space Sunday: imaging a star and x-rays from a planet

The M-2 red super giant Betelgeuse, 650 light-years from Earth, as seen by the Atacama Large Millimetre Array (ALMA). Credit: ALMA / ESO / NRAO

Some call it Betelgeuse others call it Beetlejuice. It is the second brightest star in the constellation of Orion and officially designated Alpha Orionis, the ninth brightest star in the night skies over Earth.

A red super giant of spectral type M1-2, Betelgeuse is around 12 times the mass of our own Sun, and is one of the largest and most luminous stars visible to the naked eye. It is also destined to be – in cosmic terms –  very short-lived. At just eight million years of age, it is already approaching the end of its life and will likely go supernova some time in the next few thousand years.

But it is the star’s sheer size which makes it stunning: it’s an estimated 2.6 AU in diameter. To put this in perspective, were it to be dropped into our solar system to replace the Sun, it would extend out towards the orbit of Jupiter.  Such is its size, it is one of the few stars we can observe via telescope large enough to be resolved as anything more than a point of light.

This was brought home at the end of June 2017, when the Atacama Large Millimetre Array (ALMA) captured the star in a series of images taken at the sub-millimetre wavelength range. The images reveal the star’s chromosphere looking somewhat asymmetrical, the result of the star  generating a massive bow-shock as it moves through the interstellar medium. In short, as Betelgeuse travels through the gas clouds at a rate of around 30 kilometres per second, it own equivalent of the solar wind (much denser than anything the Sun generates) which is thrown off of the star at 17 kilometres / second, slams into this gas in the direction of travel at47 km/ sec, generating a massive shock wave about 3 light-years across in front of the star, which curls around it, influencing its chromosphere.

The bow shock preceding Betelgeuse, as seen by the Japanese Akari orbital observatory. Credit: JAXA/Akari

When Betelgeuse goes supernova, it will be in a blink of an eye – although we’ll only know about it 650 years after it has actually happened. When it does so, it will create an unmistakable light in the night sky – and this bow shock of matter will play a role in the supernova process, as it reacts to the sudden influx of matter slamming into it from the exploding star at a large fraction of the speed of light.

As violent as it will be, the Betelgeuse supernova will not threaten life on Earth, as it’s beyond the “harmful” range. And in case you think that’s a bit of a reach, scientists have shown that the Earth has in fact been influenced by supernovae in the past. This evidence comes from the presence of Iron 60 in the deep oceans, an isotope formed within stars, and which has an exceptionally short half-life: 2.6 million years – so the fact we can detect it suggests it originated in other stars that went supernova.

In fact, for the last 5-10 million years, the solar system has been travelling through a region of space called the “local bubble”, an expanding region of gases some 300 light years across, created by a series of supernova explosions which occurred over a relatively short period  of time about 20 million years ago. Within this bubble, the magnetic field is weak and disordered, which could greatly magnify the impact a large supernova occurring within 100 light years from Earth could have on life here.

At the upper end of this distance, research suggests a supernova could lead to climate changes similar to those which caused a rise in glaciation seen in the Pleistocene period, 2.5 million years ago. At the nearer end of this distance – say, 25-30 light years – a supernova could actually be an extinction level event for much of life here due to the radiation levels striking the Earth, altering the climate, impacting the Earth’s biomass, and giving raise to increases in cancers.

The stars of the IK Pegasi system compared to our own Sun (r). IK Pegasi is the large white star on the left, and IK Pegasi B – a potential supernova progenitor – is the white dot below and between the other two stars. Credit: R.J. Hall

Fortunately, the nearest known star to us which is likely to go supernova is IK Pegasi B, a massive white dwarf star which forms part of the binary star system IK Pegasi in the constellation of Pegasus, and 150 light years away. As a massive white dwarf, IK Pegasi is no longer generating energy through nuclear fusion. However, when its companion star, IK Pegasi A, a main sequence star slightly larger than our own Sun and itself a variable star, reaches the latter stages of its life, it will swell up to a red giant, allowing IK Pegasi B to star accrete matter from it, causing it to swell to as much a 1.4 solar masses – at which point it will explode as a supernova.

China’s Launch Failures

China’s space efforts have been in the news for the wrong reasons of late. In mid-June a Long March 3B rocket – the workhorse of the Chinese fleet – designed to carry a communications satellite to geostationary transfer orbit was declared a “partial failure” when the rocket’s upper stage failed, initially leaving the satellite stranded in a much lower orbit. Since then, mission controller have been using satellite’s manoeuvring motors gradually nudge it up to an operational orbit, although this will drastically shorten its active lifespan.

A slight fuzzy TV image of the Long March 5 launch on July 2nd, 2017. The vehicle suffered “an anomaly” shortly after lift-off and eventually crashed into the Pacific Ocean. Credit: CCTV

Then, on July 2nd, 2017, the second launch of China’s powerful Long March 5, capable of launching 8.4 tonnes of payload to the Moon or placing 25 tonnes in low Earth orbit, suffered a major failure shortly after clearing the launch pad at 11:23 GMT. This booster is key to China’s longer-term ambitions in space, as it is crucial to the development of their own space station, as well as vital for a number of deep space missions.

Following a flawless lift-off from the from the Wenchang Satellite Launch Centre, observers watching in-flight video of the Long March 5’s ascent noticed a plume of gas late in the first stage burn, suggesting a problem with one or both of the engines in the core stage. Mission control later reported they had tried to correct flight problems by changing the rocket’s ascent, but the attempts were unsuccessful and rocket and payload eventually crashed into the Pacific Ocean.

As a result of both issues, launches of both the Long March 5 and the Long March 3 series have been halted while the probable causes of both failures are determined. The next launch for Long March 5 had been due in November 2017, when one of the rockets had been due to lift the Chang’e 5 automated lunar sample return mission to the Moon. It now appears likely this mission will be delayed.

Pluto’s X-Rays

As several of these Space Sunday articles have reported, Pluto is quite a surprising little world – and the more we start to think we understand it, the more it decides to surprise us again. Most recently, data gathered during a survey of Pluto by the Chandra X-ray Observatory has revealed the dwarf planet to be a far stronger emitter of x-rays than should be the case.

Pluto’s tenuous atmosphere is a source of higher levels of x-ray emissions that should be the case – adding a further mystery to the little world Credit: ESO/L. Calçada/Nick Risinger

Natural x-ray emissions from planets is not unusual. Venus and Mars, for example are x-ray emitters as a result of the interaction between solar wind and argon and/or nitrogen in their atmospheres. Pluto has an atmosphere which also contains nitrogen, so prior to the survey, scientists were expecting Chandra to detect them.

Prior to the New Horizons mission flying past Pluto in 2015, it had been theories that Pluto might have a tenuous, but extensive atmosphere during periods of perihelion, when it is closest to the sun, and so under the greatest influence of solar radiation. The last perihelion Pluto enjoyed in its 248 year trip around the Sun was in 1989 – so when the New Horizons vehicle passed it in July 2015, Pluto was still enjoying its “summer”.

However, while the vehicle did detect an atmosphere (one far more active than had been imagined), the data it returned indicated that this atmosphere is far more closely constrained to the planetoid that had been theorised. Thus, it had been assumed Chandra would detect levels of x-ray emissions in keeping with this. Instead, the observatory has revealed the planet’s x-ray emissions are far more in keeping with Pluto have the kind of deeper, more extensive atmosphere as had been originally theorised.

This has left the New Horizons team with a further mystery to explain, and while some theories have already been put forward to explain the Chandra results, they tend to rest on finding some exotic means of almost “lensing” the solar wind in the vicinity of Pluto. Currently, the hope is that the stores of data gathered by the space probe and which have yet to be analysed might offer a key to unlocking the mystery.

Mars: Friendly or Hostile to Life?

It’s an ongoing debate: just how friendly / hostile is the surface of Mars to microbial life? The planet has long been known to have once harboured conditions favourable for microbes, but at the same time it has also long been known that the surface of Mars isn’t exactly friendly to life. It is subject to harmful amounts of ultraviolet (UV) radiation, and it contains minerals which are hostile to many forms of microbe, whilst conversely seeming to offer a potential energy source of organisms.

Perchlorates, for example, appear to be widespread across Mars, having been detected by a number of missions. They are formed by ultraviolet radiation from the sun reacting with chlorine compounds in the Red Planet’s soil (regolith). These are both a potential source of energy for micro-organisms and deadly danger for them. The question has been just how much of each they might be.

The surface of Mars could be far more hostile to microbial life than previously thought

It’s a question Jennifer Wadsworth and Charles Cockell of the UK Centre for Astrobiology at the University of Edinburgh have sought to answer, and their findings are not encouraging – at the very least for Earthly bacteria. In tests, the pair exposed the bacterium Bacillus subtilis, a common spacecraft contaminant, to perchlorates and UV radiation at levels similar to those found at and near the Martian surface. They discovered the bacterial cells lost viability within minutes. Further, when they added iron oxides and hydrogen peroxide, two other common components of Martian regolith, to the mix they found the B. subtilis death rate by a factor of 10.8 in less that 60 seconds after cultures were exposed to the mix.

“These data show that the combined effects of at least three components of the Martian surface, activated by surface photochemistry, render the present-day surface more uninhabitable than previously thought,”  Wadsworth and Cockell state in publishing their findings. However, they point out that other strains of bacteria might not be similarly affected, particularly extremophile bacteria which might be expected to arise on Mars, and further research is required. Nor is it clear how deep below ground the effect might be felt.

On a brighter note, the study does offer some good news as it means there is much less risk posed by bacteria like B. subtilis contaminating the surface of the planet, as they are highly unlikely to surface more than a minute or two of exposure to surface conditions.

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5 thoughts on “Space Sunday: imaging a star and x-rays from a planet

  1. Hi Inara! I love your posts and Space Sunday is always fun. I notice a small error regarding the diameter of Betelgeuse:
    But it is the star’s sheer size which makes it stunning: it’s an estimated 0.6 AU in diameter. To put this in perspective, were it to be dropped into our solar system to replace the Sun, it would extend out beyond the orbit of Jupiter. Such is its size, it is one of the few stars we can observe via telescope large enough to be resolved as anything more than a point of light.

    Since an AU is the distance from the Sun to the Earth, I knew something was off about this; 0.6 AU would put its diameter within the orbit of Venus. Wikipedia claims the radius of Betelgeuse is 887 Solar radii, plus or minus 203 Solar radii. Now a solar radius is about 1/215 of an AU (good lord, the Sun is big!), so multiplying that out gives us an average of 4.12 astronomical units. More than Mars and less than Jupiter. At it’s maximum of 1090 SR (5.0698AUs), that would still come inside of Jupiter’s mean orbital distance by about a tenth of an AU. Which is pretty close to the point of your paragraph: Betelgeuse is big!

    I hadn’t seen that image of the star yet; what do you suppose is the source of that odd lump? A massive prominence?

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    1. You’re right – I actually should have said, “2.6 AU” (rounded from a parallax value of around 2.58 AU), and “out towards Jupiter. My mistake, now corrected! Not entirely sure where my head was in that I didn’t pick that up in re-reading the piece!

      The asymmetrical form is thought to be a massive storm passing through the Chromosphere in reaction to the the bow shock reaction with the interstellar medium.

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      1. Oh, neat! So Betelgeuse is so massive that its interaction with the interstellar medium is do much more intense than that of our own Sun that it causes distortions in the star’s outer layers? The dynamics of that system must be incredible. The heliopause of our system extends roughly 120 AUs out — I would expect the influence of Betelgeuse to extend farther. But this suggests it does not and ‘local’ space around the red giant is somehow pinched. I can’t wait to see what the James Webb reveals about that star!

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        1. Betelgeuse is apparently moving through a more concentrated region of interstellar gas than the Sun (despite the local bubble), and its own “solar wind” is far more dense than that Sun’s, so the two clash more violently, and this is being somehow reflected in the violence of the storms in the chromosphere. Like you (and me!) astronomers are hoping the JWST will reveal a lot more about precisely what is going on.

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