Day: July 10, 2017

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.

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.

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.

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.

Continue reading “Space Sunday: imaging a star and x-rays from a planet” →