Life on our planet faces many threats. Cosmically speaking, the three biggest threats life on Earth faces, are solar flares an coronal mass ejections, Earth-crossing asteroids, and locate supernova events – the violent explosions of stars as they die.
Of these three, Earth-crossing asteroids tend to get the most attention, as they are regarded as the most immediate n terms of potential threat and what we can actually do to actually mitigate that threat if we’re given enough warning. Solar activity is a risk, but fortunately, when even at the peak of its cycle, our middle-aged Sun is rarely viciously violent, and when it does get angry, it’s rare that Earth is directly in the path of an lash-out – although as I noted in my previous Space Sunday article, we have recently come close.
Supernovas are also a mixed bag – we certainly can’t stop them, and if one occurs that is sufficiently violent and close enough to us, then we could be in a spot of bother no matter where we are in our orbit around the Sun. If close enough, supernovas of Type 1a or Type II could go so far as to be extinction level events (ELEs). Fortunately, in order to do so, such a supernova would have to occur in a fairly massive star that’s within a few hundred light years of us – and there are precious few of those. And if if one did explode as a supernova, that are all so far away, we’d see them long before we’d feel the effects.
Take Betelgeuse for example, a star that has caused much speculation among some due to its recent behaviour. Even if we witness the light of its supernova explosion tomorrow, it would be another 100,000 years for the “hard” radiation of the explosion’s cosmic rays to reach us.
But what of smaller stars – white dwarfs – that are also given to going out with a supernova bang? There are a couple on our neighbourhood, but they are nowhere near that stage in their lives, nd by the time they are, we’ll pretty much be beyond the distance from them at which they could do us a mischief.
So, does that mean supernova are not a threat? No; leaving ELEs aside, a local supernova could still trigger long-term havoc with things like the Earth’s climate. In fact, a new study indirectly points to this possibly being the case around 2-3 million years ago, when the Earth was subjected to the effects of a nearby supernova.
The basic evidence for this comes from concentrations of 60Fe, an iron isotope, found in deep ocean sedimentary rock layers called the ferromanganese crusts. What is significant about this is that 60Fe doesn’t naturally occur here, but is a by-product of supernova events, thus leading some to conclude the remnants of such an explosion once washed over us. However, it has also been pointed out that 60Fe can also be synthesised by AGB stars as they approach the end of their lives without ever going supernova, so it is possible the deposits found on the ocean beds were purely the result of distant interaction with one or more AGB stars far back in the time of Earth’s youth.
Because of this ambiguity, a team from the Technical University of Munich gathered several dozen ferromanganese crust samples from four widely separated locations on the floor of the Pacific ocean and at depths of between 1.6 km and 5.1 km beneath the ocean surface. They subjected all of these samples to extensive analysis to see if they could find traces of other elements that could be tied to either a supernova or the output of an AGB star. And they were successful, finding concentrations of the manganese isotope 53Mn. This is significant as this isotope doesn’t naturally occur on Earth, nor is it a product of AGB stars – but it is a product of supernova explosions.
Further, the team’s analysis of both the 53Mn and 60Fe concentrations revealed that both are present in similar amounts and the same ratios throughout all of the samples studied. This suggests that both were present in the Earth’s biosphere at the same time, and were deposited on the ocean floor in similar quantities over the same period of time, again pointing to them having a common origin in a supernova event. What’s more, because 60Fe has a half-live of 2.6 million years before it decays into nickel, said supernova could not have occurred more than about 2.5 million years ago.
In addition, the concentrations of both isotopes proved sufficient for the team to estimate the like size of the star the caused the supernova: between 11 and 25 times the size of our Sun. That’s of a sufficient size for the supernova to create what’s as called a “bubble” or “cavity” in space: a region that appears to be almost completely devoid of matter. Interestingly, for the last 7-10 million years, our solar system has been travelling through just such a “bubble”, called the Local Cavity. It is believed to have formed as a result of number of supernova events that occurred between 20 and 10 million years ago – which creates an interesting overlap with the idea of a supernova affecting Earth some 2.5 million years ago.
2.5 million years ago also marks the start of the of Pleistocene period, a time of considerable climate change that saw repeated cycle of ice ages that in turn saw dramatic shifts in the flora and fauna, with multiple mini extinction events, This cycle then repeated in the late Pleistocene through early Holocene (11,700 years ago), and the planet started to warm up again, leading to further cycles of extinction (notably those mammals that had developed to level in the cold, like the woolly mammoth).
What triggered that sudden cooling is unknown, but while the Munich study doesn’t point it it directly, it has been shown that severe interference by cosmic rays can cause dramatic shifts in climate, particularly towards the colder extremes. So again, the time link between that ancient supernova evidenced in the ferromanganese crusts of the seabed and rise of the ice ages of the Pleistocene is interesting.
Starship SN8 Set for Pressure Tests
The core hull of the SpaceX Starship prototype SN8 was moved to the test stand during the pas week to undergo tank pressure tests. Fitted with the aft aerodynamic flaps that will help the vehicle “skydive” through the atmosphere, but sans the upper section, nose cone and forward aerodynamic surfaces, and currently without motors, the core section was due to undergo a pressure test as this article was being written.
This test involves the tanks within the section being filled to operating pressures with inert liquid nitrogen. A hydraulic ram under the stand the exerts pressure on the base of the structure to simulate the stresses the three Raptor engines that power the vehicle will place on the structure in order to verify its fitness for flight.
Should this test be successful, SN8 will have the upper sections added, and its engines mounted. It will then go through further tests, including actual fuelling and a static firing of it motors. Once all these tests have been completed, the vehicle will be ready for its 15 km high “hop”, which is likely to take place before the end of the month.
At the same time as SN8 is undergoing its tests, prototype SN9 is also being readied for its first flight.
CHEOPS and the Wasp: Characterising an Exoplanet
CHEOPS, the Characterising Exoplanet Satellite (CHEOPS), lunched by the European space Agency in December 2019, is the first space-based mission that is intended to provide us with more information on the nature of exoplanets we’ve discovered and catalogued – particularly those ranging in size from roughly equivalent of Earth up to about the size of Neptune, or four times Earth’s diameter.
Following its commissioning tests in early 2020, the satellite formally commenced operations in April 2020, when it turned its attention to the planet WASP-189b, first detected in 2018, and a curiosity among exoplanets.
At 1.6 times the size of Jupiter, Wasp-189b is larger than the intended specimens for study by CHEOPS, bit is an ideal candidate for study due to its oddness. It orbits a very hot blue star called Wasp-189 (or HD 133122) some 322 light years away in the constellation of Libra. One of the more notable aspects of the planet is that it is – when “seen” via electronic means – unusually bright, allowing it to be monitored as it passes behind its parent in is orbit, as well revealing information about itself and its star as it transits in front of its parent.
By observing the planet in April, May and June, CHEOPS gathered significant data on both it and its parent star. This data both confirmed the planet’s size and its orbital period – just 2.7 terrestrial days. It also revealed that the planet has one of the hottest surface temperatures of any exoplanet, the upper layers of its atmosphere reaching an incredible 3,200º C – hot enough to instantly turn iron into gas, prompting questions as to what might lay at its core, and whether it even has a solid core.
CHEOPS also revealed that Wasp-189b isn’t so much reflecting the light of its parent the way most planets do, but is actually absorbing the light of the star. This is heating the atmosphere to a point where is is actually radiating light on its own – which is in itself quite remarkable.
Unlike most planets, Wasp-189b doesn’t orbit around its parent’s equator, but rather at an angle that almost carries it from pole to pole. This has led to speculation that it formed much further away from its parent, but the gravitational influence of a passing star upset its original orbit, dragging it into the high axial tilt and pushing it in towards its parent until equilibrium between the two was achieved.
Nor is that all. The data from CHEOPs has revealed the star is itself an oddball, spinning so fast, it is clearly an oblate spheroid, bulging outwards at its equator in an exaggerated manner. It is also far hotter in its polar regions that its equatorial regions,. Quite why this should be has yet to be understand.
These first results from CHEOPS indicate that the satellite has enormous potential for increasing our understand of exoplanets and charactering the nature of many of the worlds orbiting nearby stars during its initial 3.5 year mission period.
NASA Warned On Plans
The Aerospace Safety Advisory Panel (ASAP) has warned that a combination of over-ambitiousness and funding problems could result in exposing NASA’s Artemis lunar programme to “significant engineering and human risk”.
The panel notes that the funding issues are not NASA’s fault, but lie with Congress attempting to defer certain budget appropriations in the wake of the SARS-COV-2 pandemic and its economic impact. This has meant, for example, that of the US $3.2 billion NASA requested in the next year to fund development of the Human Landing System (HLS) – the vehicle and life support systems needed get crews to the surface of the Moon and back -, only $600 million has thus far been approved; enough to fund the programme until February 2021.
While that funding gap will likely be improved as both the House and the Senate complete their budget deliberations, the ASAP remains concerned that, given the funding issues that do exist, that NASA’s determination to stick to the goal of landing humans on the Moon before the end of 2024 no matter what will lead to unwanted consequences as programmes are forced to suspend and resume as a result of funding shortfalls – a situation that could get worse as time goes on.
The panel has an ongoing concern that with each continuing resolution comes directly related and significant budget challenges which, when combined with the direction to be on the moon by 2024, just increases the pressures to make engineering compromises in order to stay on schedule. That pressure is only going to go up as launches in 2024 become closer.
– Paul Hill, ASAP Committee member.
With regards to testing in particular, the panel is particularly concerned about NASA’s suggestion that integrated testing of things like SLS booster avionics could be avoided (saving time) in favour of separate lab testing of the individual elements and e.
The panel has great concern about the end-to-end integrated test capability and plans, especially for flight software. As much as possible, flight systems should be developed for success with the goal to test like you fly.
– Paul Hill, ASAP Committee member.
Committee chair Dr. Patricia Sanders further noted that while NASA had created an Office for Systems Engineering and Integration for its human space flight systems, that office isn’t actually focused on the on technical and engineering integration requirements of the different hardware and software systems needed for human space flight, but rather on the broader brush strokes of mission architecture, and should therefore be redirected in its operations.
In response, NASA has stated it is confident of the level of accountability with the Artemis programme, but will take the panels concerns into consideration.