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.
NB: This is a speculative piece.
For 39 years images and data have been streaming across space. A small flotilla of missions to the TRAPPIST-1 system has begun transmittting. Seven small rocky worlds, all at least nominally Earthlike have drawn their share of attention over the decades. They huddle tightly around an angry little red dwarf star, somewhere in the Aquarius constellation.
Some of these planets sit within the habitable zone of TRAPPIST-1, that sweet spot where the temperature is just right: the proverbial bowl of porridge. Just right for what?
For water to exist in liquid form on the surface. And some of these worlds are very watery. Long ago the James Webb Space Telescope spotted water and indications of seasonal change on several of these worlds. Spectroscopic analysis enabled us to see these worlds with different eyes.
The missions now assigning themselves to various locales in this system show us a family of worlds possibly bearing life. TRAPPIST-1e is the prime target, but each world has a story to tell.
First approach showed us a red planet, with signs of vigorous atmospheric activity. There appears to be a purple tinge to the four large landmasses straddling this globe.
This purple haze is a striking feature of the planet. It may be due to native organisms using a photosynthetic pigment such as retinal. This protein may have been employed by early photosynthesisers on earth. Chlorophyll may have been a later card to be added to the deck.
TRAPPIST-1e appears to possess a diverse set of environments. Overall, it is a temperate world, and any life does struggle with sometimes extreme solar flare activity from TRAPPIST-1 .
Dust storms are a feature of TRAPPIST- 1e. In the above image a drone has spotted one such dust storm on the horizon as it flies over a large inland body of water. It is twilight in this image.
The TRAPPIST-1 worlds are close. The orbits of all seven planets would fit within the orbit of Mercury back home.
Traces of green can be noticed on the slopes of this extinct volcano. TRAPPIST-1 is believed to be ancient: on the order of eight to ten billion years. It’s family of seven worlds may have seen life arise more than once. This may have happened on our own world, with an enigmatic array of creatures known generically as Ediacarans appearing before the more conventional forms we see today.
The proximity of the TRAPPIST-1 planets presents an opportunity for researchers to observe lithopanspermia. The Swedish chemist Svante Arrhenius was one of the earliest scientists to suggest that life or it’s building blocks could travel from world to world, hitching a ride on moving objects such as comets or asteroids. Lithopanspermia builds on this. It’s a big idea, and observations on several of the TRAPPIST-1 worlds is showing us something we’ve only speculated on. Life travels between worlds, carried by rocks sent into space by impacts and volcanic eruptions.
Were a visitor to be admiring the sunset on, say, TRAPPIST-1d, they’d be in for a treat.
In this system, life is not restricted to one world. Here, an ecosystem interconnected by space borne life has given rise to an interplanetary ecosystem.
Next time, we visit a frozen world that may be hiding it’s own life, far beyond the habitable zone of TRAPPIST-1.
Read some other posts and tell me what you think! Also, please do me a favour and check out my YouTube channel:
All images: Ben Roberts
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:
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.
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!
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!
It’s a story that began 20000 years ago, and has been waiting for you. Like something out of a “Star Trek” episode. The vista before you hangs in the black like a portal into the fiery underbelly of all that’s good in the Universe.
“Star Trek” You remember it now. The Battle of Wolf-359. It was a classic episode, in which a tattered human military force took on a vastly superior foe: the Borg. These creatures were bloodless and implacable. Truly unsettling bad guys.
This monster is just as unsettling. Wolf-Rayet-124 is real. It’s huge. You’ve come a long way to encounter it. A small fleet of drone-sats has been dispatched to get up close and personal with this Wolf-Rayet star, to see how extreme extreme sports can get.
As soon as humans got comfortable in space and started calling all kinds of dark corners and odd rocks home they were up to their usual mischief. As soon as all the laws were decreed and the soapboxes were all put away, humans got back to the serious business of finding new and bizarre ways to enjoy themselves.
Space tourism didn’t become big business. It became exponentially big business. Extreme sports fans weren’t interested in scuba diving with great white sharks anymore, or parachuting.
Ha! You recall the stories. The One-G-ers were those quaint old extreme sportsters who couldn’t let go of old mother earth. Most of them were toothless and half nuts decades ago, but they still harped on about climbing Mount Everest or wrestling crocodiles.
You look upon Wolf-124, blazing with a luminosity several million times greater than Earths sun back home. Wolf-124 is huge. How huge? These kinds of stars are rare. Of the millions of stars known to humanity only around 500 Wolf-Rayet stars are known to exist in this galaxy.
Wolf-Rayet stars are thought to be the powerhouses driving many planetary nebula or stellar nurseries. How does this work?
Your little drone sats are tasting the cloud of ionised gas and interstellar gunk that swirls around the star. This cloud is nearly 6 light years across; a dusty miasma flung outwards by the intense solar winds radiating from the star within. From your vantage point out here, looking down into this slow maelstrom you see chunks of the star heading outward. Earth sized pieces of WR-124 soar through the cloud like the volcanic rage of a demon tearing itself apart.
You write that last line down. The tourists will love it.
Sometime around 20000 years ago, when human beings were first discovering Europe WR-124 began tearing itself apart. Scientists never really ascertained why, but it’s made for some great observations over the years. Tourists will love this. You got here first, to set up the first fleet of solar sailing yachts. The winds from the star crack along at 1600 km per second, fast enough to twist the most iron stomachs.
These stars have unusual emission spectra. Many of the space tourists won’t care what this is, but there’s always someone in every group who just has to understand what they’re leaping into. Fair enough. What it means is that like any other star a Wolf-Rayet star burns up fuel. Our star, a relatively youthful star somewhere near middle age, is still burning hydrogen via the process of stellar fusion. As a star ages it’s supply of hydrogen becomes depleted, and it must burn heavier elements in order to survive.Wolf-Rayet stars are often seen to have high levels of quite heavy elements or “metals” such as carbon or nitrogen in their upper atmosphere. This is due to nearly complete depletion of hydrogen fuel so as a result heavier elements are being used up.
What does this have to do with spectra? Well, as elements transition from higher to lower energy states, ie when they’re being burned up inside a star, photons of particular wavelenghts are given off. It’s possible to tell just by analysing the wavelengths of light radiating from a star (it’s emmision spectra) what’s going on in and immediately around the star. This is why scientists know WR stars are old, and what they’re burning off in place of hydrogen. It’s also the reason they can infer the presence of extreme solar winds. The luminosity and heat given off by a WR star is extreme. At it’s surface a WR star can reach temperatures of between 30000 and 200000 Kelvin; hotter by far than most other stars. Such radiative pressure literally manifests as a “wind”, with the abilty to exert pressure on objects, such as solar sails!
Most of the drone sats are keeping a safe distance from WR-124. This might just be an imaginary blog post, but you have imaginary operating costs, you know?
So you’ve staked your claim here. Now, all that’s left to do is wait for the money to fly in!
Still, you’re thinking of your next venture. There’s an exoplanet out there somewhere: HD 189733B where it rains glass! Now that sounds like fun…..
While you’re here, join me on the AstroBiological YouTube channel. I’m hard at work sprucing it up. What do you think of this intro sequence?
One last thing!
Hop onto WeCreateEdu: an online community for educational you tubers. There is a galaxy of stuff to learn and explore here. Very much worth a look:
Small YouTube channels are feeling the squeeze from some draconian new measures by Google which effectively punish small creators and make it almost impossible to gain traction. Some thoughts on the matter from a fellow YouTuber.
A few months ago I was watching a YouTube video which steered me towards the topic of this post. I am a (very small time) youtuber myself, and spend a lot of time looking for ways to tweak my content and make it more polished. The YouTube video mentioned above was made using screen capture software and the simulation package Universe Sandbox. The video featured all kinds of hypothetical scenarios being imagined and allowed to play out within the simulation. For example, the questions were asked: what if Saturn was moved closer to the sun? What if Earth passed through its rings on this inward journey? What if Saturn and Jupiter made a close approach to each other?
It was fascinating to watch. Simulating actual physics and real world parameters you could see what actually could happen if such scenarios actually took place. It got me thinking about my own video content, and about these simulation software packages. I of course had to get my hands on some!
Currently I am producing videos using both my laptop and my smartphone. In this post I will focus on the capabilities of a smartphone to produce videos about outer space.
Animations for this video were produced entirely on my smart phone, using several apps available on Google Play. My phone is an Android device, but I’m assuming there are equivalents over at the enemy camp.
First off, these apps are great educational tools. Perhaps where they are the most effective is getting people to explore from the palm of their hand. In this device obsessed era this is a big deal and also a drawcard for the digit generation. This video explores some mobile apps I’ve been using for my YouTube channel. It’s really amazing what you can do with amazing most nothing! I’ll also include a video about Uranus. All of the planetary animations came from mobile apps.
The Uranus video:
Here is another earlier video briefly introducing the moons of Mars…
And in this one I discuss Enceladus and some promising signs of habitability there:
These videos were extremely easy to make and perhaps the point of this post is that anyone can communicate something they care about. Enjoy!