Tag Archives: planet formation

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!

Planet Building: Possible?

If you don’t want to read, then listen! I have put this post up on a podcast I’m doing, available on Anchor FM, as well as certain other outlets.

https://anchor.fm/astro-biological/embed/episodes/Planet-Building-e1ff39

If anyone has read “The Hitchhiker’s Guide to the Galaxy” quadrilogy they would have been struck by some of the big ideas hidden within Douglas Adams’ deadpan humour. One of the heavy concepts that stuck with me was the idea of planet building. According to the story, Earth as we know it today is a planet sized super computer, built to perform one task: to figure out the meaning of life. A planetary architect named Slartibartfast is entrusted with overseeing the rebuild of Earth after it’s destroyed due to a galactic scale clerical error.

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Planet building.

Possible? Why not? According to prevailing theories, planets mainly form via the process of accretion. Simply put, particulate matter adrift in molecular clouds clumps under the inexorable pull of gravity, forming ever larger clumps that clump to ever larger clumps and so on. Eventually a planet or star is the inevitable result.

A newly formed exoplanet (in the dotted circle) orbits a newly formed, newly discovered star: CS Cha. Image: Space.com

Why couldn’t this be done artificially? Would it be even possible? If it’s just a matter of throwing lumps of crud at other lumps of crud and hoping they stick, then why couldn’t it be?

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Scenario:

It’s the future. Humanity lives and works in space. The asteroid belt is the new frontier or wild west. Chunks of formerly useless rock are now homesteads or villages. Distances are not overly tyrannical. An asteroid is typically only a few light seconds from another. However, asteroids can be moved. Bigger asteroids like Ceres, Vesta or Eros would comprise the main hubs of commerce and trade in this new world.

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A new frontier… Image: Maciej Rebisz

Smaller settlements such as these “homesteads” could make life easier for themselves in terms of travel times (and therefore fuel costs) to larger, more important settlements by moving closer. In the frictionless, zero gravity environment that is space this wouldn’t be too technically difficult.

Scenario:

Time has moved on. The asteroid belt is a thriving collective of trade networks and conglomerates of smaller settlements. Smaller asteroids now cluster around larger ones like space junk in low earth orbit. Economically, this proximity is making things easier for everyone, and lots of people are getting rich.

Just imagine though if humans disappeared. The zombie apocalypse hit outer space and spread to all corners of the solar system.

(That’s the fun explanation)

Every living human is gone, and the asteroid belt is now a vast ghost band, forming a wreath around the sun, somewhere between Mars and Jupiter. There are all these swarms of asteroids now adrift, all artificially brought closer together by generations of enterprising human beings No course corrections keep them from colliding and so many of them are doing just that. Orbits decay, and tiny chondrite specks plough slowly into larger planetesimals.

See where I’m going with this? Over time, natural accretion would naturally lead to planets forming, or at least a large moon sized object. In millions of years the solar system could have a tenth planet (let’s just sneak Pluto back into the club. Don’t tell anyone!)

Planet Building! Essentially a garbage planet could form from the artificially placed asteroids and other objects now in very close proximity and drawn by the slow but inescapable pull of gravity.

I think it’s an exciting idea: a real megastructure! The ultimate megastructure!

What next?

This post was inspired by a chance statement in a video discussing space colonies on Isaac Arthur’s Science and Futurism youtube channel. Check it out. Isaac has a huge catalogue of lengthy discussions on some really interesting concepts. Here is a link to the relevant video if you’re interested:

Last but not least, here are links to the social media for Maciej Rebisz, the talented artist behind some fantastic space artwork, including the asteroid colony about halfway down the post.

facebook – https://www.facebook.com/maciej.rebisz

twitter – https://twitter.com/voyager212 – general updates

artstation – https://www.artstation.com/mac – art

society6 – https://society6.com/macrebisz – prints

Join me on my facebook group:

https://www.facebook.com/groups/AstroB/

And on YouTube. I’m not quite up to the standard of the venerable Mr Arthur (yet), but I’m working on it. Help me on this journey and subscribe!

http://www.youtube.com/c/BensLab