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Saturday, 27 August 2016

Exploring Proxima b - 3 possible ways

So, the cat is out of the bag…… if that cat were an Earth like planet orbiting a star just four light years away: Proxima Centauri, the nearest star to Earth, has an Earth like planet (link here)! 

But that phrase ‘Earth-like’ can be a bit misleading: What, at this point, do we actually know? 

Let’s start with the star: Proxima Centauri is a red dwarf, just 4 light years from Earth. The existence of a planet orbiting it has been suspected for a long time, but because red dwarfs are badly behaved stars it has taken until now for the international Pale Red Dot team of astronomers to confirm its existence using the European Southern Observatory's instruments. 

Pale Red Dot haven’t actually clapped telescopes on the planet – they’ve detected it from the way it makes the Proxima star itself wobble as it orbits. That’s a standard way of detecting a dim exoplanet, and the size and length of the wobble gives us some information: 
  • The planet is at least 1.3 Earth masses
  • It orbits close to Proxima, and has an 11 (Earth) day long year. 
  • Because Proxima is a small dim star, that puts the planet in the right distance range for liquid water on its surface.
Which means…. it could have, y’know, the ‘A’ word… 

I'll stop abusing this meme after today, I promise. It's just... look at his hair!

What we don’t know is almost everything else – a Venus-like hell world, or an Io type volcanic planet, would look exactly the same to this detection method. 'At the right distance for water' isn't the same as 'has liquid water'. To add some more uncertainty, red dwarf stars are grumpy little buggers: They’re prone to massive flares, and Proxima b will be getting an unhealthy X-ray dose about 250 times bigger than Earth. 

So we need to find out more. How? 

Planetary transit

Above: The process of a stellar transit. When the planet is in front of the star the star's light shining through the atmosphere can be used to determine the atmosphere's composition.

This method needs a huge dollop of luck but, if it works, could start gathering data on Proxima b this year. The idea is this: If, as seen from Earth, the planet’s orbit takes it across the disc of Proxima itself, the starlight will shine right through its atmosphere (more detail here). That would let us look for changes in the starlight that indicate what he atmosphere is made of. But if nature doesn’t co-operate we’ve still got some good options… 

Use the JWST and E-ELT: 

Above: The anatomy of the James Webb Space telescope, courtesy of NASA.
James Webb Space Telescope will be NASA’s next big space telescope, and the European Extremely Large Telescope is a yet-to-be-built monster, with primary mirror forty meter across. Either one might – just – be able to pick out Proxima B as a single pixel. A single pixel isn’t much, but exo-planet hunters are already experts at picking useful data out of single pixel. Planets spin, so we could slowly build up an image of the planet – a crude one- by watching how the brightness and colour of that pixel changes as the planet turns. We could also get detail on atmospheric composition, presence of surface water, and whether or not there are any icecaps. 

Send a probe: 

Above: An artists impression of the 4 meter wide StarShot miniprobe design. Courtesy of the Breakthrough Foundation.

Now… this one will won’t happen for a bunch of years. But… maybe fewer than we think: Earlier this year I was writing about a project called ‘Breakthrough Starshot’ – a $100,000,000 effort to start developing the technologies needed to send a (very) small spacecraft to another solar system. 
Despite what has been said about it, the project is not trying to actually launch a probe: The basic physics of their laser driven design is sound, but the engineering is rather more unknown. Starshot’s current incarnation is just meant to prove some of the concepts behind it…. and the discovery of possible target like Proxima b, within the range of a Starshot type probe, is a huge boost for the project. 

Even if its air isn’t too thick (like Venus) or too thin (like Mars) and there’s liquid water on the surface, Proxima b would be a strange world to human eyes: Proxima would be a dull orange orb three times larger than our Sun from Earth, but dimmer and cooler, delivering about two thirds as much heat to the surface as our Sun does to Earth. 

Above: An artist's impression of Proxima rising over Proxima b. Courtesy of Pale Red Dot.
The planet is probably ‘tidally locked’: Presenting only one face to the light, so one side would probably be an giant ice cap, doomed to eternal night, and the other would be a desert. Only on a thin strip near the day/night boundary could a human comfortably stand - so this isn’t second Earth, no matter what the papers say. And it’s far too early to say much. But. 

Maybe this is a habitable planet close enough to one day be within humankind's reach...

Maybe…
 

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Wednesday, 24 August 2016

So it's true...


Yes, the European Southern Observatory has confirmed the rumours: They have found an Earth like planet orbiting the nearest star to Earth, at the right distance for liquid water to be stable on its surface. There will be a lot of jumping up an down, speculation, and maybe even a movie or two coming from this news... none of which needs help from me: So I'll simply leave you with the ESO announcement....


 

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Sunday, 21 August 2016

Briefly...

Hi everyone, I'm away this week and so posting may be a bit patchy. But I've got time to  quickly point to a couple of interesting things:
  • First: New evidence from preserved ocean sediments suggests that the early ancestors of humans may have witnessed our planet getting a spectacular near Miss from a supernovam Radiation from the explosion may have altered Earth's climate and influenced human evolution.
  • Second: A little bit of a development on that rumour of an Earth-like planet being found orbiting the nearest star to Earth: German magazine Der Spiegel has published a new article on it, and Chris Lintot from the BBC reports he's filming a top secret Sky at Night episode that may be related to the rumour....
In other news: I'm going to start a fortnightly mailer, with links to the source materials for the most interesting space stories on the internet - there's a lot going on and I personally can only write about so much! It's totally free, and your email address won't be passed on to third parties to bombard you with spam. I'll be putting up a button that you can use to subscribe in the next week or so.  

Take care, and I should be back to normal service in a few days.

John F.


 

Thursday, 18 August 2016

Are we the first?

What about that great silence from the sky? Where are the radio beacons and messages of all the advanced civilisations that have had 13.5 billion years to evolve in this universe? Where are the aliens?


This is probably not the answer. Probably. Image courtesy of Andreas Rocha
That's not a new thought - it's called ‘Fermi’s paradox’, and I’ve recently heard one explanation that has intrigued me, because I’d never really given it serious consideration: 

We are more or less alone. 

That's a bit counter intuitive, given that life clearly can arise (hence, y'know, us) and the universe has plenty of the right ingredients and lots of time for it to happen.  Just, maybe.... not enough time yet.

Above: A probe approaches a long lived red dwarf star.

Let's start at the source (link here): The idea comes from Harvard scientists, who point out that our Sun’s lifespan is actually fairly short compared to the lifespan of the most common kind of star in the Universe, red dwarf stars. Red dwarf stars burn for thousands of times longer than our Sun, and do so much more efficiently. To be habitable a world orbiting one would need to be so close to it that its year might only be a few days long, but there’s no such reason such a world couldn’t exist – and it would have a stable environment for longer than the universe has existed so far. 

The longer a planet is habitable, the more likely sentient life arising there is – more time, more evolution, more rolls of the dice etc. So habitable worlds around red dwarfs have much more chance of eventually hosting thinking life, just because they’ll live longer – and so sentience might be much more common in the distant future. 

This would make our existence, orbiting a fairly hot and short lived yellow dwarf, a bit of freakish accident – hence why we find ourselves (apparently) alone in the sky. 

Above: Earth - just a bit early. Courtesy of NASA

The Harvard team point out that their reasoning might be a bit too simplistic: Life on a red dwarf’s planet would face a lot of challenges…. 
….so it may be that red dwarf planets don’t actually host a lot of habitable worlds. But we don’t know for sure either way yet. To establish that the team’s recommending searching nearby red dwarfs for planets to get an idea of how many might have habitable ones. 

That brings me back to the rumour floating about that an ‘Earthlike’ planet has been discovered orbiting Proxima Centauri – the closest star to Earth and also a red dwarf. The rumour is that the planet is roughly Earth sized and the right distance from Proxima for liquid water. It’s just a rumour, and, even if it’s true…. Earth sized and the right distance for water aren’t definitive proof of a habitable world: Venus fits that description, and it’s surface is a pressure cooker where it rains acid. 

To add some confusion: A group of astronomers called ‘Pale Red Dot’, who have been searching Proxima for planets, have recently submitted a paper, and had it favourably peer reviewed…. but they deny they’re the source of the rumour. The European Southern Observatory, whom the rumour says did make the discovery, have refused to confirm or deny it… read into that what you will. But apparently there will be some sort of announcement at the end of this month.

So…. Saddle up your scepticism and doubt, but pack some wonder along with it - there could be some big announcements in the near future..
 

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Saturday, 13 August 2016

Martian stromatolites?

Tabby's star has gotten weirder - the mystery star that showed behaviour so strange that some people looked to alien mega-structures as an explanation - has showed yet more strange behaviour.

But I'm not posting on that today. Why? Because Tabby's star was doing unexplained things before. The interesting bit is the explanations people will come up with... and that's going to take a while to develop. I've already posted plenty on the subject, here, here, here, and here.

Sorry, I couldn't resist putting this in again ('cause it's probably not aliens)...

All the Tabby's star fuss has reminded me of something I read last year, and never got the chance to follow up on: That the Curiosity Mars rover may (and I cannot over emphasis that 'may') have spotted signs of stromatolites .

It's well worth following that link. If you're not down with the microbial terminology: Stromatolites are stone structures built by colonies of microbes for protection, often in lake beds. The colonies build them by trapping floating dust particles and cementing them into a solid structure.

Above: Stromatolites: Odd swirly rocks made by microbes....

On Earth some stromatolites are so well made that they've survived nearly 4 billion years, and are the oldest unambiguous evidence of life on earth.  And on Mars...

Martian microbe houses:
Nora Nofke is Mrs Stromatolites - she has spent her whole career studying them - and some of the rock structures photographed by the Curiosity rover bear a striking resemblance to fossilised stromatolites, as she reported to the journal Astrobiology.

Above: Some of the rocks seen by Curiosity resemble (weathered by billions of years)  stromatolites. Image courtesy of JPL.


Nofke isn't claiming to have found definitive evidence of Martian life. Like the micro tunnels in martian rocks that I wrote about a few weeks back, this looks like something made by life, but 'looks like' ain't proof. The rise and fall of the claims of Martian microbes being found fossilised in the ALH84001 meteorite show just how cautious anyone advancing such a claim needs to be.

That said... according to someone who has spent their whole career studying stromatolites... these rocks look very like a stromatolite formation.

Nofke's peers are sceptical because that's the job of a scientist. But they agree she's done a good job with the data to hand:

“I’ve seen many papers that say ‘Look, here’s a pile of dirt on Mars, and here’s a pile of dirt on Earth,’” says Chris McKay, a planetary scientist at NASA’s Ames Research Center and an associate editor of the journal Astrobiology. “And because they look the same, the same mechanism must have made each pile on the two planets.That’s an easy argument to make, and it’s typically not very convincing. However, Noffke’s paper is the most carefully done analysis of the sort that I’ve seen, which is why it’s the first of its kind published in Astrobiology.”

The only way to get a definitive answer would be to bring samples of the possibly-stromatolites back to Earth and subject them to the full battery of analysis we have here - and that's not likely to happen any time soon. Even so, together with recent finds of organic carbon and (tiny amounts of) liquid water on modern Mars, Nofke's analysis adds fuel to speculation that Mars might have once been called home by something.

Nofke's paper from last year can be found here.
 
Above; Stromatolites  growing in a shallow lake on Earth. Mars once had shallow lakes like this so.... maybe...

 

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Sunday, 7 August 2016

More evidence for water on Ceres....

There's yet more evidence to add to the growing pile of oddness and geological mystery that is the 'king of the asteroid belt': The dwarf planet Ceres.

Above: The battered and unassuming surface of Ceres - yet one that has turned out to be baffling. Image courtesy of NASA/JPL.

We've already found out, from space telescopes and the phenomenally successful Dawn mission, that there's evidence of water vapour escaping it's surface, that surface having been modified by ammonia, and bizarre bright spots and fogs in some of its craters.

Above: Dawn's close up of the strange bright deposit at the centre of the Occator crater - a patch that seems to be associated with water-related geology, and ephemeral mists..

Now we can add to that geochemical evidence for there having been briny flowing water near the surface, for at least some of it's history. The evidence comes as carbonate deposits in Occator crater which, not coincidentally, is the one with both the  bright spots and the mysterious fog patches. These deposits suggest that briny liquid water flowed near the surface at some point. That water could have been due to heat from major impacts, or warmth from the little worlds own warm core.

Above: An artists impression of the interior of Ceres.

It makes yet another indication that the teeny dwarf planet probably had conditions suitable for life's chemistry at some point.
Why is that so exciting? Because conditions suitable for life's chemistry - even relatively brief ones near the solar system's dawn - are an opportunity for us to peer into how that chemistry evolved. That can inform us to how nature progresses from complex organic chemistry to life. And, most exciting of all, it might mean there are geological remains of an environment that supported simple life there. And Ceres is not much further away than Mars - but much more easy to return samples from, thanks to its low gravity....
 

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Thursday, 4 August 2016

Things that might be due to aliens, part 4: Tabby's star....

When we talk about the idea of finding alien life – whether that’s a galactic empire or a single microbe – people often get frustrated by the prevarications and grey-area language scientist use. There’s a good reason for that though: Every time a mistaken or false claim gets into the papers it damages the reputation of all scientists. 

So making a claim as big as first contact, only to have someone else prove you wrong, can end a career. That means research into anything remotely connected to the idea of alien life gets super, super, cautious. But there are a few odd, unsolved, mysteries in space that researchers will admit might – just might as an outside chance – turn out to be alien in origin. In the last post looking at the four most tantalising of these we'll be talking about...


Tabby's Star:

If you follow this blog, or have interest in astronomy at all, this mystery has probably crossed your radar at some point: Informally named for Tabetha S. Boyajian, the lead author of the paper that first drew it to world wide attention, this stars real full name is KIC 8462852 – and it’s still just possible that hideous string of alphanumeric gibberish will go down as the most important in human history. 

Just - it's looking shaky but the jury's still out.

The star first came to attention as part of an exoplanet hunt carried out by the Kepler space telescope. Kepler spots possible exoplanets by looking for the way a stars light dips as a planet passes in front of it. But when it looked at Tabby's star... things went a bit wrong:... 

This is the mystery: If you graph the light output of a star as a planet passes in front of it you’ll get a signature something like this:


That signature will repeat regularly, as the planet goes around it’s star – and although some exoplanets have been directly imaged by powerful telescopes, this is still one of the best methods for picking up the majority of exoplanets - they're mostly too close to their stars or too faint to image. 

Above: Images of  extrasolar planets - rare, and usually not showing more than a faint spot of light.

However, when Kepler looked at Tabby’s star, it saw a pattern of dimming like this: 


The dips in the stars brightness don’t follow any predictable pattern, and are so deep that something much bigger than a planet must be causing them. Instrumental error, the star itself somehow dimming and dust from planetary collisions were all ruled out. A swarm of disintegrating comets was proposed to be the cause, but this too would need special pleading (i.e. it’s incredibly unlikely to happen in such a way as to cause this dimming)... 

...And so, we get to that explanation, a very out there one but which was too exciting to ignore completely: Tabby’s star could be home to a heavily industrialised civilisation that was building a ‘Dyson swarm’. 

I'm fairly sure you'll have met this meme at some point....

A Dyson swarm is a huge cloud of solar energy collectors, which encircle a star and convert a huge chunk of it’s light output into usable power. Although the scale of such a project is totally beyond humanity today, the science and engineering principles are not – space platforms that turn sunlight from space into major amounts of useable electricity have been seriously proposed for decades. 

What made things even more exciting was that further investigation suggested that Tabby’s star had been steadily dimming for the last hundred years – exactly what you’d expect if a Dyson swarm were being constructed around it . That claim has been seriously questioned, and it looks like the apparent dimming is down to changes in telescope technology and observing methods.

SETI has also tried to tune into any possible radio or microwave transmissions coming from this solar system – and found nothing. If there were a huge construction project going on near the star you might expect to pick up some sort of chatter.... although our radio technology is only sensitive enough to rule out a very loud radio chatter (the star is 1500 light years away after all). 

Above: The Atacama Large Millimeter Array (ALMA)..

Debunking the long term dimming, and finding no clear radio signals, may weaken the case for the dips in Tabby’s star’s output being artificial but they don’t rule it out – the only way to do that is to actually come up with a plausible natural explanation for the dips, and prove it. So, if you fancy a challenge….
 

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