Posts Tagged‘formation’

Ice Crystal Formation on a Soap Bubble.

Thanks to our northern hemisphere counter-parts I’ve been privy to all sorts of interesting cold weather things from making instant snow to the ingenuity that people come up with when they’re snowed in. Here in Australia we do get the up on the other end of the spectrum quite often during summer however although that doesn’t really drive us to do much more than sit around a pool and drink copious amounts of beer. So you can imagine then that anything involving sub-zero temperatures is going to be somewhat intriguing to us, especially something as cool as this:

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There’s nothing particularly complicated about what’s going on here but the demonstration is quite novel. What you’re seeing is the formation of ice crystals on the surface of a soap bubble which starts off slow but ramps up significantly as more crystals form. I think this is partially due to the way crystals form as they usually need a rough surface to attach to. This is how those instant ice videos work as the bottles don’t have any anchor points for the crystals to form but once you shake it up a bit you give them a surface to attach to.

There was one question that was left unanswered due to the video cutting off at the end however: whether or not it’d still float after it was frozen.

Now the bubble isn’t increasing in mass, it’s simply changing forms. There’s the possibility that some of the moisture from the air outside the bubble will condense onto the crystalline surface however I don’t think that’d change the mass by an appreciable amount. The density would also be going down as well thanks to water’s intriguing property of getting less dense as changes into ice. All those factors together would indicate that a frozen soap bubble would behave in much the same way as a regular one but I’d still like to see this hypothesis tested.

Although I do much prefer warmer climates, so this will have to be an exercise that’s left up to the reader.

Nomad Planets: Our Intergalactic Truck Stops.

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.

An Earth With Two Moons.

Our Moon has been a constant source of amazement and wonder for the human species. For as long as we’ve been able to observe it from our earthly bounds it has only ever shown us one side and wobbling ever so slightly as if to tease us as to what we couldn’t see. For the longest time we speculated about what could be on the other side of our closest celestial partner with theories ranging from the mundane to the outright fantastical. Of course since 1959 when Luna 3 first photographed the far side of the moon most of that mystery and wonder has since evaporated, but even today it still manages to throw a couple curve balls our way.

One of the most puzzling aspects is the distinct difference in terrain between the near and far sides of the moon. Comparatively the near side of the moon is quite smooth with many “maria” or land seas covering its surface. The far side on the other hand is deeply cratered with a considerably more rough appearance than the side we’re all familiar with. There are many explanations for this with the most accepted being that the near side contained a higher concentration of radioactive elements when it was first formed, and this has been confirmed from data from orbiting craft. There is however a new theory that’s come out and it depicts a story of an Earth that once had two moons:

The moon is thought to have formed when a Mars-sized body slammed into the infant Earth. This threw a cloud of vaporised and molten rock into orbit, which coalesced into the moon.

Simulations have previously shown that additional moons could have formed from the debris cloud, sharing an orbit with the one large moon that survives today. Eventually, gravitational tugs from the sun would destabilise the moonlets, making them crash into the bigger one.

Building off the most accepted theory of the Moon’s formation (the Giant Impact) this new theory about the far side of the moon’s appearance postulates that the impact also created another, smaller Earth bound satellite. Now usually smaller bodies are quickly engulfed by their bigger neighbours but this smaller moon stabilized into an orbit long enough for it to fully form. However millions of years later it impacted with the current moon at a relatively slow pace of about 8,000KM/H (for reference, the International Space Station orbits at around 25,000KM/H). So instead of smashing each other to bits they instead squished together forming a turbulent far side of the moon. Such a hypothesis also explains some discrepancies between mineral concentrations on either side of the moon as such an impact would have pushed the moon’s magma to the other side.

Now whilst this theory would explain some of the phenomena we’re seeing with our celestial sister there’s not a whole bunch of direct evidence to support it. The heavily crated far side of the moon could easily be explained by the tidal locking with Earth, which means any incoming asteroids are far more likely to hit the side facing outwards. This is made all the more difficult by the fact that there has been no landed exploration of the far side of the moon and definitely no sample return missions. Getting some rock samples from the far side of the moon would provide the answers we need to rule out or pursue this theory further.

I always find it amazing how we can think we’ve explored something so thoroughly yet it can still surprise us. The moon is something we’re all so familiar with yet it’s still so foreign when you get up close and it’s origins are as mysterious and intriguing as our own. I love that these ideas could lead to us sending a sample return mission to the far side of the moon and what’s even more exciting is that such a mission would probably lead to many more questions than answers. That’s the beauty of science, it’s a never ending journey of discovery into the origins and mechanics of the universe that surrounds us.

MESSENGER: Mercury’s First Artificial Satellite.

Mercury is a strange little beast of a planet. It’s the closest planet to our sun and manages to whip around it just under 88 days. Its “days” are 59 earth days long and whilst it’s not tidally locked to our parent star (like the moon is to us, always showing the same face to the earth) it is in a 3:2 spin-orbit resonance. This has led to some interesting phenomena when we’ve sent probes to image it as the only probe to ever visit it, Mariner 10, only managed to image 45% of the planet’s surface on it’s 2 encounter trip with the tortured little planet. That all changed a few years ago when MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) made its first approach to Mercury in January 2008 and sent back images of the as of yet unseen side of the planet. Ever since then MESSENGER has been on a long trajectory that will eventually bring it into orbit with Mercury and it will begin it’s year long mission of observations.

It just so happens that that day is today.

MESSENGER has been in space for an extremely long time, almost 7 years. You might be wondering why it has taken this craft so long to reach Mercury and the answer requires that you understand a little about orbital mechanics. You see as a heavenly body, in this case a satellite, moves closer to another body it will tend to speed up. This is known as the conservation of angular momentum and it’s the same principle that governs the increase in speed when you bring your arms in closer whilst you’re spinning. Thus for a satellite that’s launched from Earth to be able to orbit Mercury it has to shed all that extra speed so it can match up to it, otherwise it would just whiz right past it. Since doing this with a rocket is rather expensive (the fuel required would be phenomenal) NASA instead opts to shed velocity by a complicated set of maneuvers between planets, each of which removes a portion of the satellite’s velocity. This is cheap fuel wise but means the space craft will have to endure many years in space before it reaches its destination.

As I write this MESSENGER is making its final preparations to insert itself into an orbit around Mercury.  MESSENGER hopes to demystify the diminutive planet by providing hi-resolution imaging of the planet (there’s still 5% we haven’t seen yet), doing chemical analysis to determine the planet’s makeup and attempting to figure out why Mercury has a magnetic field. Probably the most interesting part of MESSENGER will be the last part as our current theories on planet formation point to Mercury being much like our moon with a solid core and no magnetic field to speak of. The presence of one there suggests that part of Mercury’s core is still molten and raises a number of questions over how planets and natural satellites like our moon form. It will also be the first ever artificial satellite of Mercury, something that still eludes many of the other planets in our solar system.

This is the kind of science that NASA really excels at, the stuff that just hasn’t been done before. It’s really amazing to see NASA flex their engineering muscle, designing systems that survive in the most unforgiving environment we know for decades and still function as expected. The next year will be filled with all kinds of awesome discoveries about our tortured little cousin Mercury and I for one can’t wait to see how the analysis of its magnetic field changes the way we model planet formations in the future.

 

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Gliese 581g: The Tantilizing Possibility of Life Elsewhere.

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.

The news spread like wildfire when astronomers at the Keck Observatory in Hawaii released information regarding a planet who’s characteristics looked very familiar:

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.