Scale is something that’s hard to comprehend when it comes to celestial sized objects. The sheer vastness of space is so far beyond anything that we see in our everyday lives that it becomes incomprehensible. Yet in such scale I find perspective and understanding, knowing that the universe is far greater than anything going on in just one of its countless planets. To really grasp that scale though you have to experience it; to understand that even in our cosmic backyard the breadth of space is astounding. That’s just what the following video does:
In the short time that I’ve been enamoured with all things space our understanding of the universe has changed significantly. Just a few years ago we had no idea how common multi-planet systems like our own were but today we know that a star is far more likely to have several planets than just a few. At the same time we’ve discovered so many more exoplanets that their discovery is now just routine and the count has tripled from the couple hundred to well over 600 confirmed discoveries (not including the multitude of current candidates). At the same time our understanding of how planets form has also been called into question and today brings news that may just turn our understanding on its head yet again.
Astronomers at the Kavli Institute for Particle Astrophysics and Cosmology released a paper back in February that detailed a very interesting idea. Using the observable effects of gravity in our galaxy combined with the observable mass (detected via microlensing events) they’ve deduced that there needs to be many more planets than what can be accounted for. What’s really curious about these planets is that they would have formed without a parent star:
But how can this be? Every star can’t have tens of thousands of planets ranging from Pluto-sized to Jupiter-sized. This planetary “excess” actually suggests the existence of planets that were born without a star – nomad planets. These planetary vagabonds somehow went through the planet-forming process in interstellar space, not in the dusty proto-planetary disk surrounding a young star.
This astonishing number was calculated by extrapolating a dozen “microlensing” events of nomad worlds passing in front of distant stars. When these nomad planets drifted in front of distant stars, they briefly focused the starlight with their gravity, causing the star to brighten. This brightening was captured by astronomers and the microlensing events could be analysed to reveal the characteristics of the nomad planets.
The idea of planets forming sans a parent star is an interesting one as it turns our current ideas of planet formation on their head. The generally accepted idea of planet formation is that a large accretion disk forms a star first, sweeping away a lot of matter away from it. After that the left over accretion belt begins coalescing into planets, asteroids and other heavenly bodies. Nomad planets then would have formed in smaller accretion disks without the required matter to form a star. If the paper is anything to go by this happens extremely often, to the tune of 100,000 times more often than there are stars in our galaxy.
Such planets are incredibly difficult to detect as we have no beacon to observe for wobbles (the radial velocity method). The only way we have to detect them currently is via microlensing and that means that the planet has to pass between us and another star for us to be able to see it. Even with so many planets and stars out there the chances of them all lining up are pretty slim which explains why we haven’t detected any to date. What we have found though are Brown Dwarfs and they’re quite interesting yet again.
Brown Dwarfs are what you’d call failed stars (or over-achieving planets, take your pick) as whilst they’re quite massive, on the order of 13 times the size of Jupiter at minimum, they still don’t have enough mass to ignite and become a fully fledged star. They do however generate quite a bit of heat which they give off as infra-red light. We can detect this quite readily and have identified many of them in the past. What’s intriguing though is that these Brown Dwarfs (or other nomad planets) could be used as stepping stones to the rest of the galaxy.
There’s a couple things that such planets could be used for. We already know that such planets could be used as a gravity slingshot to give current interstellar craft a speed boost en route to their destination. Another highly theoretical use would be to use these planets as refuelling stops if you were using some kind of hydrogen/helium powered craft. Such planets would also make excellent observation posts as they’d be far away from strong sources of light and radio waves, allowing them an extremely clear view of the universe. Indeed nomad planets could be quite the boon for an interstellar civilization, all we need is the technology to access them.
I’m very interested to see where this theory takes us and hopefully we’ll star seeing some nomad candidates popping up in the exoplanet catalogues in the next couple years. We might not yet be able to make use of them but their mere existence would tell us so much about the formation of heavenly bodies in our universe. At the same time it also raises a lot of questions that we haven’t considered before, but that’s the beauty of science.
So I’ve decided to try my hand at being a game developer after spending way too many hours thinking about it and wanting to do something more exciting than developing yet another web application. This isn’t the first time I’ve tried my hand at developing games either, I did a semester long course in games development back when I was in university. That course still rates as one of the most fun and interesting semesters I ever spent there, especially when your games were put up against the harshest critics I’ve ever met: the lecturer’s two kids. After finishing that course however I never really continued to try and make games until a mate of mine introduced me to Unity.
For a straight up programmer like myself Unity is a bit of an odd beast. The Unity editor reminded me of the brief foray I had with 3D Studio Max back in college, as it sported many of the same features like the split screen viewport and right hand column with all object’s properties in it. It’s very easy to navigate around and it didn’t take me long to whip up a simple littlesolar system simulator, albeit one that lacks any form of gameplay or semblance of realism. Still being able to go from never having used the product before to making something that would’ve taken me weeks in the space of a single weekend was pretty exciting, so I started about working on my game idea.
So of course the first game I want to make is based in space and the demo I’ve linked to before was the first steps to realizing the idea. It was however very unrealistic as the motion of the planet is governed by simply tracing out a circle, with no hint of gravity to influence things. Additionally the relative sizes and distances were completely ludicrous so I first set about making things a little more realistic to satisfy the scientist in me. Doing some rough calculations and devising my own in game scale (1 unit = 1,000KM) I made everything realistic and the result was pretty tragic.
The sun took up the vast majority of the screen until you zoomed out to crazy levels, at which point I couldn’t find where the hell my little planet had gotten off to. After panning around for a bit I saw it hiding about 4 meters above the top of my monitor, indistinguishable from the grey background it sat on. Considering this game will hopefully be played on mobile phones and tablets the thought of having to scroll like a madman constantly didn’t seem like a fantastic idea, and I relegated myself to ditching realism in favor of better gameplay. My artistic friend said we should go for something like “stylized physics”, which seems quite apt for the idea we’re going after.
It might seem obvious but the idea of suspending parts of reality for the sake of game play is what makes so many games we play today fun. The Call of Duty series of games would be no where near as fun if you got shot once in the arm and then proceeded to spend the next hour screaming for a medic, only to not be able to go back into the mission for another couple weeks while your avatar recuperated. The onus is on the developer however to find that right balance of realism and fantasy so that the unrealistic parts flow naturally into the realistic, creating a game experience that’s both fun and doesn’t make the player think that it’s an unrealistic (or unfathomable) mess.
I’m sure my walk down the game developer road will be littered with many obvious-yet-unrealized revelations like these and even my last two weeks with Unity have been a bit of an eye opener for me. Like with any of my endeavors I’ll be posting up our progress for everyone to have a fiddle with over in The Lab and I’ll routinely be pestering everyone for feedback. Since I’m not going at this solo anymore hopefully progress will be a little bit more speedy than with my previous projects and I’ll spend a lot less time talking about it 🙂
Space travel is on the rough end of the stick when it comes to physics. To get ourselves out of the massive gravity well that keeps us from travelling to the stars we have to expend vast amounts of energy, usually in the form of a chemical rocket. It’s a tried and true system however with chemical rockets powering every single mission that has left the confines of earth. There has been talk of many other forms of propulsion that could potentially perform a lot better than our trusty chemical companions but thanks to their fuel being of the nuclear variety they’ve never made it past the theoretical stage. Still for all their successes chemical rockets still have their draw backs, not least of which is the ungodly amount of fuel they use.
Take a look at any rocket and you’ll notice that the vast majority of it is taken up by a single component, the fuel tank. Whilst the actual cost of the fuel is a rounding error when compared to the cost of developing the rocket itself the fuel still makes up the vast majority of the wet mass of the craft, usually 85% or more. To put in in perspective the biggest rocket ever built, the Saturn V, weighed in at a massive 3 million kg when it was on the launch pad but only delivered 120,000 kg to low earth orbit (with 45,000kg eventually reaching the moon). A mere 4% of the total launch weight made it out of earth’s gravity, a truly staggering figure. This is more commonly referred to as the mass ratio.
It should come as no surprise then that the limiting factor for many space missions is weight related. As payloads get bigger so does the rockets and the amount of fuel required to lift them into orbit. This puts an upper limit on how big rockets can get before the amount of fuel required becomes unmanageable and instead many missions will favor multiple, smaller launches in order to get the required payload launched. The International Space Station is a good example of this as its current mass, some 420,000 kg, would have required a rocket of unimaginable size to launch all once. Instead it has been assembled in numerous smaller flights each adding around 20,000 kg each time. Most missions do not have this kind of luxury however and their designs represent a trade off between capabilities and the maximum launch weight they can have.
Most notably this affects missions that want to reach further than earth orbits, such as missions to other planets. Since they have to carry all the fuel required to get into orbit and to get them started towards their destination the payloads they can deliver are far smaller than they could be. Whilst we’ve still been able to do an amazing amount of science and exploration with such vehicles it’s still one of the most limiting factors that keeps more ambitious missions (read: ones with us humans in them) from being realized. There is however one ingenious solution to this problem, and that’s refueling in orbit.
Whilst the notion of flying just fuel up into orbit might seem like a strange idea it’s one that will enable subsequent missions to be far more capable. Indeed the cost of carrying several tons of fuel for pushing out past earth’s orbit adds many times that in launch mass. Thus craft that can refuel once in orbit can be significantly heavier at launch (since they’re not carrying the fuel) and can then fuel up for their trip beyond earth. The idea originally started to get traction back when Obama announced his plan for space exploration back in early 2010 and it seems that it’s finally going to become a reality:
Space explorers who need to top off the fuel tanks on the way to the moon or Mars may soon get their orbital refueling stations. NASA has put out the call for a $200 million mission to show how to store and transfer rocket propellants in space.
NASA wants to look specifically at liquid oxygen and liquid hydrogen, which have powered the main engines of the space shuttle and several commercial rockets. Its proposal calls for “zero boil-off storage” of liquid oxygen, and at least “minimal boil-off storage” of liquid hydrogen.
The proposal comes with the promise of $200 million for the company who wins the opportunity to build the station with an additional $100 million should they be able to demonstrate significant benefits for the additional investment. Whilst there are already companies working on these sorts of ideas NASA’s proposal goes far beyond what they’re currently capable of and is being built with the vision for larger missions beyond earth rather than refueling satellite’s station keeping fuel reserves. The proposal could also have flow on benefits to companies like the United Launch Alliance and SpaceX who could design future crafts around the idea of being able to refuel on orbit.
If we want to get serious about extending our presence beyond our home world (and we’re too afraid to use nuclear rockets) then orbital refueling stations are the key to realizing that vision. We’ve started to make the first steps to commoditizing space travel and the next logical step is to start unlocking access to other parts of our solar system, both for science and the simple prospect of exploring the unknown. Whilst this idea might not be realized tomorrow its a helluva lot more real today than it was yesterday and humanity is one step closer to taking our rightful place amongst the stars.
Humanity, for the longest time, has been aware of planets outside the one that we reside on. Ask anyone today about the planets in our solar system and they’re sure to be able to name at least one other planet but ask them about any outside our solar system and you’re sure to draw a blank look. That’s not their fault however as the discovery of planets outside our solar system (which is by definition, not a planet but an exoplanet) is only recent, dating just over 20 years when the first was discovered in 1988. Since then we’ve discovered well over 500 more planets that exist outside our immediate vicinity and whilst their discovery is great none of them have yet been much like the one we currently call home.
In fact the vast majority of the exoplanets that have been discovered have been massive gas giants orbiting their parent stars at the same distance as Mercury orbits from our sun. This threw scientists initially as back then our current theories on solar system formation didn’t support the notion of large planets forming that close to their parent star. However as time we found more and more examples of such planets, these hot gas giants orbiting at velocities the likes we’d never seen before. The reason behind this is simple, the methods we use to find exoplanets are quite adept at finding these planets and not so much those which we’d consider potential homes.
The method by which the vast majority of exoplanets have been discovered is called the Radial Velocity method. As a planet orbits around its parent star the parent star also moves in tandem, tracing out an elliptical path that’s pinned around the common centre of mass between the two heavenly bodies. As the star does this we can observe changes in the star’s radial velocity, the speed at which the star is moving towards or away from this. Using this data we can then infer the minimum mass, distance and speed required to induce such changes in the planet’s radial velocity which will be the exoplanet itself. This method is prone to finding large planets orbiting close to their parent stars because they will cause larger perturbations in the star’s radial orbit more frequently, allowing us to detect them far more easily.
More recently one of the most productive methods of detecting an exoplanet is the Transit method. This method works by continuously measuring a star’s brightness over a long period of time. When an exoplanet crosses in front of its parent relative to us the star’s apparent brightness drops for the time it is in transit. This of course means that this method is limited to detecting planets and stars whose orbits line up in such a way to cause a transit like this. For earth like exoplanets there’s only a 0.47% chance that such planets will line up just right so we can observe them but thankfully this method can be done on tens of thousands of stars at once, ensuring that we discover at least a few in our search. Exoplanets discovered this way usually require verification by another method before they’re confirmed since there are many things that can cause a dip in a star’s apparent brightness.
There are of course numerous other methods to discover planets outside our solar system but for the most part the vast majority of them have been discovered by one of the two methods mentioned above. For both of them they are heavily skewed towards discovering big planets with short transit times as these produce the most observable effects on their parent stars. Still this does not preclude them from finding exoplanets like earth as shown with the recent discovery of Kepler10-b, a small rocky world in torturous conditions:
The planet, called Kepler-10b, is also the first rocky alien planet to be confirmed by NASA’s Kepler mission using data collected between May 2009 and early January 2010. But, while Kepler-10b is a rocky world, it is not located in the so-called habitable zone – a region in a planetary system where liquid water can potentially exist on the planet’s surface.
“Kepler-10b is the smallest exoplanet discovered to date, and the first unquestionably rocky planet orbiting a star outside our solar system,” said Natalie Batalha, Kepler’s deputy science team leader at NASA’s Ames Research Center in Moffett Field, Calif., at a press conference here at the 217th American Astronomy Society meeting.
Kepler-10b is the smallest transitioning planet to be confirmed to date and shows that it’s possible to discover worlds like our own using current technology. As time goes on and the amount of data increases I’m certain that we’ll eventually find more planets like these, hopefully a bit further out so they’ll be in the habitable zone. The Kepler mission is just a few months shy of its 2 year anniversary with at least another 1.5 years to go and if all goes well it should be returning swaths of data for us for the entire time to come.
I’m always fascinated by the latest discoveries in space even when they’re something like a molten mercury 564 light years away. Our technology is becoming more advanced with every passing day and I know that future missions will end up discovering millions of planets at a time with thousands of potentially life supporting worlds. It’s amazing to think that just 3 decades ago we couldn’t be sure that planets existed outside our solar system and today we know for sure there are more than 500 of them out there.
Ain’t science grand?
For all the exploration of space we’ve done to date we have still found no evidence of life outside our own biosphere. We’ve found many of the building blocks scattered around our solar system but all our attempts to find even the most simplistic of life forms have been met with failure. Still with the raw ingredients being so common in just our own back yard it follows that there’s a high likelihood that somewhere in the deep blackness of space lies another planet that teams with life like our own. Still with the number of exoplanets only numbering in the hundreds and the technology strongly skewed to finding large gas giants close to their parent stars we had yet to come across another planet that life as we know it could call home. That was until just recently.
An enticing new extrasolar planet found using the Keck Observatory in Hawaii is just three times the mass of Earth and it orbits the parent star squarely in the middle of the star’s “Goldilocks zone,” a potential habitable region where liquid water could exist on the planet‘s surface. If confirmed, this would be the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one. The discoverers also say this finding could mean our galaxy may be teeming with prospective habitable planets.
“Our findings offer a very compelling case for a potentially habitable planet,” said Steven Vogt from UC Santa Cruz. “The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common.”
Vogt and his team from the Lick-Carnegie Exoplanet Survey actually found two new planets around the heavily studied red dwarf star Gliese 581, where planets have been found previously. Now with six known planets, Gliese 581 hosts a planetary system most similar to our own. It is located 20 light years away from Earth in the constellation Libra.
Gliese 581 is one of the most studied stars in our sky with no less than 6 exoplanets being discovered orbiting it. It’s a red dwarf star meaning it’s much less bright than our sun and is quite a bit less massive. Still the planets that are orbiting it look very familiar with one of it’s planets being very much like Venus (very close to the sun, probably a planetary hot house) and another quite like Mars (much further out, could potentially have or hosted life). The Gliese 581 system provides evidence that our kind of solar system, one with a diverse range of planets and several habitable candidates, is quite possibly very common. Gliese 581g is exciting because unlike it’s two sister planets it’s right smack bang in the middle of the habitable zone, and with that comes the chance of life.
In this picture Gliese 581 resides right near the bottom with the habitable zone being quite close to the parent star, right up to a mere 10% of the distance from earth to our star. Gliese 581g lies right in the middle of this zone and due to the close proximity this leads to a few interesting characteristics. A year on Gliese 581g is a little over 36 days long which is amazing when you consider Mercury, the closest planet to our star, still takes around 88 days to complete one rotation around our sun. Because of this close proximity to its parent Gliese 581g is also tidally locked to it, forcing the same side of the planet to always face the red dwarf star. Because of this I do not believe that life as we know it could exist on this planet. However that does not mean life could not survive (or even thrive) there.
Our version of life is the only model we’ve got to go on right now since we really haven’t come across anything different. Whilst many forms of life might look completely alien to us they all shared the same basics that enabled other life to thrive on earth. The key to all life as we know it is water as nearly everywhere on earth where there’s some form of water we tend to find life teaming there, even in the most inhospitable conditions. Gliese 581g is big enough that it should be able to hold onto a tenable atmosphere and the temperatures at the surface should be sufficient to support liquid water. However the weather on the surface would be anything but calm as cold wind from the night side of the planet would be constantly blowing thanks to the constant heating of the day side. The terminus boundary between eternal night and day could serve as a habitable strip all across the entire planet, but this is where things get tricky.
The day/night and seasonal cycles of this planet have greatly influenced how life formed on this planet. Gliese 581g would have none of these things with no orbital tilt to speak of to generate the seasons and either constant day or night depending on which side of the planet you were on. This means that any life that evolved there would have to cope with such conditions, eliminating the need for a circadian rhythm and any kind of seasonal behaviour. Since nearly all species of life on earth rely on both these mechanisms for survival the life on Gliese 581g would be wildly different from our own, probably lacking the need for sleep and being almost constantly active. Of course there would be other selection pressures at work here as well, leading to even more alien forms of life.
Is life guaranteed to exist there as so many articles claim? Not in the slightest. There are so many factors that lead up to the development of life that we just can’t be certain one way or another. There are some theories that the Moon played a large part in kick starting life on earth and right now we can’t tell if Gliese 581g even has one. There’s also the real possibility that our new celestial cousin has a thick, acidic atmosphere killing any early stages of life well before they had the chance to adapt. Until we can get more data on the planet anything we say about life there is purely speculative and really it will always be that way until we send a probe there to investigate.
Still Gliese 581g means so much to us for what it symbolises. It shows us that our solar system isn’t unique in the galaxy and gives evidence to support the idea that there are untold numbers of planets that are potentially habitable. We’re on the brink on discovering many, many more of planets like Gliese 581g and each one will give us some insight into the formation of our universe and ultimately life itself. We’re still a long way from being able to explore them for ourselves but I know that one day we mere humans will journey to those stars and revel in their beauty.