Category Archives: scicomm

Life Around a Failed Star..

While NASA’s Parker Probe delves into the mysteries of our own sun, other objects known as brown dwarfs taunt us, adrift in a limbo between star and gas giant.

Could Life Survive Around a Failed Star?

November 2, 2018

To date, a little over 3700 exoplanets have been discovered. Many of these owe their discovery to the Kepler Space Telescope, which as of writing this post has been retired by its masters. Thank you Kepler.

Not all of these planets are habitable. Far from it in fact. Only about 55 “Earthlike” planets have been earmarked for a closer examination. With an estimated 2 trillion planets in the Milky Way galaxy alone, this tiny group of maybes doesn’t seem to hold out much hope for the astrobiology crowd. In order to simplify things a little, researchers generally look for life as we understand it, in environments we can understand. A world with a mild climate, liquid water, with life employing carbon is the rule of thumb.

It’s a big universe though, and life not as we know it could be the norm. What kinds of lifeforms could exist in environments in which life on earth could never arise?

In the atmospheres of gas giants? On frozen worlds? What about rogue planets: worlds not tethered to a solar system. These wanderers could be common in this galaxy. What about brown dwarfs?

What is a brown dwarf ? Often they are referred to as brown dwarf stars, and this gives some clue as to their nature. Literally, a brown dwarf is a failed star. That is to say, a brown dwarf is a former protostar which has failed to reach the critical mass required for star hood. Far from being underachievers though, brown dwarfs are interesting to exoplanet researchers. These mysterious objects exhibit properties of stars and planets.

A rogue planet is a wandering planet: homeless so to speak. How is this important for exoplanet research? In my most recent video I talked a little about some of the difficulties faced by astronomers when attempting to directly image exoplanets.

The images don’t look like much. One problem with direct imaging is that the light from host stars get in the way. Brown dwarfs circumvent this by often being standalone objects, enabling researchers to examine these “pseudoplanets” (pseudostars?) and learn more about exoplanet characteristics and behaviour.

What about their starlike features?

A star is an object which uses fusion of elements such as hydrogen or helium to produce heat and light. Other stars fuse heavier elements, but we’ll just avoid that fork in the road today 😉

This is a red dwarf star at work. The heat and light produced by this little monster could support life in other solar systems. TRAPPIST-1 is a well known example.

This is an artists impression of a typical brown dwarf. Generally much more massive than Jupiter, our own big guy, this object may undergo limited fusion of heavier elements such as deuterium.

Of even more interest to astrobiologists: brown dwarfs could be capable of supporting life! Not in themselves as such, but several brown dwarfs are known to possess their own planetary systems.

Let’s add a planet to this image. A planet in orbit around a brown dwarf may be heated by tidal stresses. Worlds such as Europa in our solar system lie far beyond the habitable zone surrounding our sun, yet may theoretically harbour life in a subsurface ocean heated by tidal forces. Hypothetical worlds orbiting brown dwarfs could experience something similar.

Of course, as I have pointed out to me all the time, life is fairly fussy, and requires a fairly stringent catalogue of conditions and contingencies. We can still dream right? After all, what’s the point of astrobiology if not to colour outside the lines a little?

Or a lot?

Find me on YouTube and while you’re at it, some other posts on this blog require your attention!

For some bizarre reason, I can’t caption images right now. All images produced by Ben Roberts, with the exception of image two, which was produced by the European Southern Observatory Very Large Telescope.

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The Lost Moon

Boom. Image: Ben Roberts

The moon is one thing we all have in common. I’ve always loved looking up at it. Whether it’s from a religious, mythological or scientific perspective, Luna holds a powerful mystique regardless. The story of the moon is written into the story of life itself.

What does the colossal impact taking place in the above picture have to do with the moon? Because it’s likely the moon formed via a process of accretion.

Around four and a half billion years ago, earth itself had only just coalesced from a cloud of gases and dust that eventually gave rise to the entire system.

Image: Ben Roberts

Earth is believed to have formed without a moon. In fact earth as we know it today formed as a result of the moon.

Picture this. Earth is newly formed. It’s a toxic planet with vast tracts of it’s surface covered by a magma ocean.

Image: Ben Roberts

From the outer solar system it comes. An object roughly the size of mars slams into Earth 1.0. The object has been named Theia. This impact is catastrophic, essentially tearing away the outer surface of our world.

Image: Ben Roberts

Where does all of this crust go? Into space, forming a ring around the newly resurfaced earth. It is this ring, consisting of the fragmentary remains of both our world and Theia, that will accrete to form the moon.

That’s the moon in a nutshell. It’s influence on the course of life has been fundamental, with a critical role in climate and seasonality via the key role it plays in tides. For over four billion years the moon has stared down upon the world, seeing the march of life with all of it’s ups and downs.

Has the moon itself been lifeless all this time? It’s been our closest neighbour for practically forever. We have always thought of the moon as a dead, hostile place. Today it certainly is. With no atmosphere to speak of, negligible water and lethal solar radiation bombarding it’s surface, the consensus of opinion is that the moon is completely devoid of life.

Image Credit: NASA/GSFC/Arizona State University

But it may not always have been like this.

It may be a stretch, but several studies have suggested that at least for a time the moon may have been at least habitable. Perhaps not an oasis of life, but a place that could harbour it.

The moon may not quite have looked like this, but volcanic activity (seen on the limb) would definitely have contributed atmosphere. Images: Ben Roberts

How is this viable? As noted, we all know the moon is hostile to all life. However, the moon is now an inert world, devoid of any geological activity.

Once, though, the moon was anything but inactive. In the period after the moons formation, around four billion years ago it was highly volcanically active.

A habitable moon more likely looked something like this. Image: Ben Roberts

Intense volcanism can be a source of atmospheric gases. This is definitely a factor on earth. Many atmospheric gases, including several trace greenhouse gases are pumped into our skies by volcanoes. Greenhouse gases are pivotal in regulating climate on earth. On the moon all those billions of years ago, volcanoes may have done something similar, bulking up the lunar atmosphere and enabling this tiny world to retain some heat. In addition, a thick atmosphere provided protection against solar radiation and an environment amenable to liquid water. Water is, as we know, crucial to all life on earth. “Follow the water” is one of the central catch cries of astrobiology. Find water, the reasoning goes, and life may be there.

This isn’t always the case though. Water exists almost everywhere in the solar system. There is even water vapour on the sun! There is plenty of water on the moon, locked up as ice in several craters in permanent darkness.

How would all this water have arrived on the moon? Prevailing theory regarding the origins of earth’s water held that much of it was delivered by cometary impacts. This is certainly reasonable. Recent discoveries though hint at vast reservoirs of water locked up deep within the planet itself. Water may be replenished over the eons by outgassing from volcanoes for example. This could have happened on the moon. Several studies of lunar composition have demonstrated that there may be similarly vast amounts of water locked up within the moons core. The ancient moon may have gained a thick watery atmosphere from centuries of volcanic activity partially terraforming it.

So, to put a long story short, water by itself is no guarantee of habitability. The moon, however, may once have been a very different place. With a thick atmosphere providing protection from cosmic rays and allowing pools of liquid water to form, life could have quite easily gained a foothold there. Most likely this life was in the form of unicellular organisms which may have arrived via lithopanspermia. This is a process whereby worlds at close proximity can exchange life or it’s building blocks via impact or volcanic ejecta.

Lithopanspermia: is it a thing? Image: Ben Roberts

This very concept is being applied to crowded systems of exoplanets such as the TRAPPIST-1 system, and is an exciting avenue to explore. In such a system, the possibility of interplanetary ecosystems could exist! This is, of course, very theoretical, but damn what an interesting idea!

What do you think? Was the moon ever habitable?

While you’re at it, check out my tiny little YouTube channel, giving you the universe in plain human!

39 Light Years: Part One

Image: Ben Roberts. Produced with Universe Sandbox

Sometime in the early 2000s, this place was still a speck of data in some astronomers brain. The announcement of a system of seven earth-sized planets was pretty big. The further revelation of three of those worlds sitting within their stars habitable zone was the icing on the cake.

As the first intelligent explorers approach TRAPPIST-1e, we present to you these images: the culmination of decades of waiting, hoping that return transmissions from the TRAPPIST-1 mission wouldn’t get lost in interstellar space. There were those who worried that anything beamed back by the missions wouldn’t even make it out of the system. TRAPPIST-1 is a red dwarf star: a tiny relic of a thing but incredibly ancient. Age estimates range from 8 to 12 billion years old. Red dwarf stars tend to be nasty little suckers, and TRAPPIST-1 is no exception. Extreme solar flare activity sometimes hits the system, as the parent star has a tantrum. Communication from the system is nothing short of a miracle. Nevertheless, here are some of the better images we’ve managed to glean from the stream of data being sent back. Thirty nine years worth. Thirty nine years of waiting.

Approach: A New Red Planet

The very first direct images of TRAPPIST-1 and it’s rocky retinue were messy little blobs of pixels.

Of course, many exoplanets (and exomoons) had been imaged directly using a variety of techniques. The use of coronagraphs to scrape together images from points of light across impossible distances was revealing new vistas for a long time. The following image was taken all the way back in 2004:

A disc of debris around the red dwarf star AU Microscopii. Image: Hubblesite.org

Of course, progress marched on, and as missions approached the system the world waited for new images. A first blurry image sped across the galactic neighbourhood:

A TRAPPIST-1 planet caught in transit across the host star. The faded object to left of centre is an artifact of the imaging process.

This image was a first test. As the mission approached the system, we began seeing more. High quality imaging was held off until final approach, in the interests of energy efficiency.

An infrared and monochromatic direct light image, taken from a distance of approximately 11 AU. Images: Ben Roberts

TRAPPIST-1e was waiting for us.

Image: Ben Roberts

Imaging of exoplanets is explored in a new video, presenting the concept of coronagraphy. Help astrobiology reach the world (this and others) by checking it out. Subscribe and share if you like.

This post is the first of a series taking us on a trip to a real alien world, and speculating on just what it could be like, using real world astrobiology. I hope you like it!

The Last Ecosystem

Fragments of ancient life, spotted by explorers in a new system..

I’ve been working on some more astrobiology art. It’s taken on a life of its own, and I have to say, I’m paying more attention to these images than my YouTube channel!

I’ve been enamoured lately of dead or dying worlds. A recent video on my channel talked about the amazing possibility of limestone fragments orbiting the white dwarf star SDSSJ1043+0855. Ever since reading of this it’s captured my imagination. The notion that life has existed long ago, possibly before life began on earth bears thinking about.

Limestone is a mineral produced primarily by organisms which produce shells, using a matrix that incorporates calcium carbonate. In the early days of multicellularity, as the predator-prey paradigm took hold of Darwinian evolution, an ancestor of today’s molluscs discovered how to make use of an upsurge in calcium levels in the oceans. It used it to produce a protective suit of armour. This trick was so successful that molluscs became incredibly abundant. So abundant, in fact, that their remains ended up as vast deposits of limestone.

To the present day.

Using spectroscopy, the three elements that comprise calcium carbonate: carbon, oxygen and calcium have been detected in the upper atmosphere of this particular white dwarf. By themselves they aren’t a smoking gun. It’s also fair to point out that limestone can form abiotically. Limestone deposits in subterranean caves are one example. However, the vast majority of limestone on earth is biologically produced.

The “limestone” orbiting this star is believed to be embedded in the fragments of a large rocky object. We know nothing about this world, only that it probably existed and (possibly) limestone comprised part of it. Is it a fossil, spotted across the light years by modern humans? How long ago did this world harbour life? White dwarf stars (which aren’t technically stars! Find out why here) have been discovered which are nearly as old as the universe.

Earth is 4.6 billion years old. What of the world currently being torn up by the immense gravity of this white dwarf?

Dead worlds could be scattered across the galaxy.

It would be interesting to look forward and see how our own world eventually will die. For now, this white dwarf star and it’s companions are a way to look ahead at what may befall us. It’s believed that eventually the earth will become incapable of supporting life, as the sun begins to undergo senescence billions of years from now. What iterations will the terrestrial biosphere take over such a vast stretch of time? Will life start over? Are these “fossil” fragments within this unnamed rocky world pieces of its last ecosystems?

What will the last ecosystem on earth be?

Keeping a Lid on Life?

A comment on a facebook post I put up a few days ago got me thinking about habitability. Moreover, I got to thinking about the parameters of habitability.

We think that life here on earth is fragile, holding on to a thin silicate crust within a fairly narrow range of temperatures and conditions. For the most part it is. Life needs a fairly stable environment in order to keep on keeping on. However, there are plenty of examples of oddballs: extremophiles, that seem to do quite well in some pretty horrible places. The recent discovery of Antarctic microbes that derive energy from air itself expands the catalogue of organisms that could have analogues on other worlds.

Now, extremophiles do well in extreme environments. No brainer there, and there is no shortage of extreme environments in our solar system alone.

Venus is an example, and a good one. Analogous to Earth in size, density, gravity and composition, it differs markedly in others. No magnetic field, no water (at 0.002% of the atmosphere not worth mentioning), surface temperatures that melt lead, and atmospheric pressure ninety two times what we’re used to here. It’s horrible.

Why?

No plate tectonics. On earth we slowly sail about the globe on slabs of continental crust, which happen to be more buoyant than the thicker, denser oceanic crust. Driven by convection of magma in the mantle, crust is slowly pushed hither and thither by tectonic processes such as seafloor spreading.

To understand what this is, imagine a pot of something thick like soup or porridge on a stove top. As the contents of the pot heat up they begin to stir. Have you ever noticed when this begins to happen that as the surface begins bubbling the top layer is forced aside as new material wells up from below? This is seafloor spreading in a nutshell. Magma from within the earth wells up, heated by a radioactive core, and pushes the seafloor aside as it breaks through, forming new crust. The continental plates, perched atop this moving crust, slowly journey across the planet.

Why is this so important to life on Earth? Because our planets interior is so hot, plate tectonics (along with volcanism) is the primary means by which excess heat is released over time. If this didn’t happen, well, you wouldn’t be here reading this and there would be two Venuses in our solar system instead of one.

Venus, or any one of billions of hellish worlds in the Galaxy? Studying worlds like this gives us insights into life here on earth, because it shows just how unlivable other places can be.

For reasons unknown, Venus shut down. It’s core stopped spinning, it’s magnetic field dwindled to nothing and radiation from the sun began a process of stripping the planet of water. Water is a true miracle ingredient. Not only is it a solvent for biological processes, it’s also a lubricant for plate tectonics. Venus seized up and overheated: exactly like a car without oil will do.

A stagnant lid world is one which has no plate tectonics. Climate is seriously affected by such a situation. With no means of escape, heat builds up within, and eventually it becomes an exo-Venus: scorching hot.

Researchers looking at the issue of habitability on exoplanets have looked at the implications of a stagnant lid regime for the possibility of life. Whilst it would obviously be different to life on earth, other factors can lend habitability to a planet.

These other possibilities are exciting indeed. I’ve been exploring astrobiology through images, producing a bunch of pictures. They will be appearing over the next few posts, so I hope you enjoy them. They’re doing well on Instagram!

Thank you for reading the ramblings of a space nerd. The universe is just too intetesting to ignore.

Talk later!

P.S.

Check out my channel!

All images: ©Benjamin Roberts

Sailed the Ocean Blue

It’s been estimated that a good percentage of planets beyond our solar system may be water worlds.

We here on mother Earth like to think of our blue green marble as a water world. Indeed it is watery, and water is pretty much the reason anything lives here at all. That’s why astrobiologists naturally seek signs of water on exoplanets. “Follow the Water” is a central tenet in the search for extraterrestrial life.

But compared to some worlds, earth really isn’t that waterlogged at all. It’s 0.002 percent water by mass. Only a tiny fraction of that water is available to terrestrial life. That water which isn’t directly involved in biological processes is linked to them, linking life to the planet via seasons and climate.

Some exoplanets are believed to be up to fifty percent water! These are true ocean worlds. To date, up to thirty five percent of exoplanets larger than may be covered by vast layers of water that may or may not harbour life. The jury is well out on that, but the idea is intriguing (and tempting) as the traditional definition of habitable zones is being stretched and reinterpreted.

A water world with a thick atmosphere of steam.

For now, we have only our imaginations with which to explore these worlds…

An aerial view of remote coastline on a hypothetical watery exoplanet.

A new video!

Life in Transit

Interstellar pollution. Free floating organics infused by starlight and beginning their ascension towards life.

Imagination is an important part of science, for without it there would be no curiosity. Here we ponder the theory of panspermia. At it’s essence panspermia is a theory which posits that life on earth (or at least it’s building blocks) came from space. How did it get here? Ancient earth was infected in a sense. Compounds and molecules useful to life were brought here by comets or asteroids and dispersed by impacts.

It is only a theory, but it makes sense in several ways. Recent research gives some credence to it. Decide for yourself. I personally believe that terrestrial biogenesis and panspermia can both contribute equally to debate over the origin of life.

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