Posts Tagged‘galaxy’

Earth, Milky Way Galaxy, Laniakea Supercluster.

How much do you know about where we are in the universe? I’d hazard a guess that nearly everyone can say that we’re the 3rd planet from our sun and that we reside in a large spiral galaxy called the Milky Way. You might not know though that we’re towards the end of one of the Milky Way’s tendrils and that we’re part of a larger group of galaxies called the Local Supercluster. However the definition of what constitutes the Local Supercluster had always been a little loose, essentially just a sphere of space in which all contained galaxies were defined as part of it. Scientists in Hawaii though, led by R. Brent Tully, have come up with a new way of defining superclusters and have dubbed our new home Laniakea.

It’s reminiscent of when the International Astronomical Union refined the definition of what constitutes a planet. Sure the new definition might mean that some previously neighbouring galaxies will get excluded, and new ones included, however rigorous definitions like these are what form the basis of good science. We might feel some kind of attachment to the ideas (I was honestly surprised by how many people were outraged by Pluto losing its planet status) however science abhors hand waving and sometimes we have to accept some loss in order to make further progress.

However I find the science behind Laniakea to be incredibly beautiful. Instead of our local group of galaxies being defined by some arbitrary points we’re now a group of celestial bodies all sharing the same journey. We might not ever see each other, nor ever cross paths, but the idea that we’re sharing the same galactic journey with billions and billions of other balls of matter is, to me, incredibly poetic.

Incomprehensible Scale.

Want to feel really insignificant for a bit?

I don’t know what it is but things like the galaxy IC1101, VY Canis Majoris and all other heavenly bodies that are just beyond anything that I’m capable of imagining captivate me completely. I think it’s probably due to the possibilities that arise from such scale. Just think about it, if one planet in one lonely solar system was able to produce a species like us what kind of life could have formed in these other places. Could it even happen? Would we be able to recognise it if we saw it? The possibilities are nearly endless and that, for me at least, is wildly fascinating.

It’s that desire to find out what’s out there that fuels my passion for transhumanist ideals. Whilst many will argue that ageing and death are a natural part of life that should not be circumvented I instead ask why you want to limit your experience to one life time, especially when the universe is so vast as to provide nearly limitless opportunities for those who wish to explore it.

Some find that incomprehensible scale intimidating, I find it invigorating.

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.