Tag Archives: Milky Way

Colonizing the Milky Way 101


The human race is likely to spend many future generations grappling with the aftermaths of its colonial sojourns across the globe. Almost every race and creed over our documented history has actively pursued encroaching upon and displacing others. By our very nature we are territorial animals, and very good ones at that.

Yet despite the untold volumes of suffering, pain and death wrought on those we colonize our small blue planet is not enough for our fantasies and follies. We send our space probes throughout the solar system to test for habitability. We dream of human outposts on the Moon and on Mars. But even our solar system is too minuscule for our expansive, acquisitive ambitions. Why not colonize our entire galaxy? Now we’re talking!

Kim Stanley Robinson, author extraordinaire of numerous speculative and science fiction novels, gives us an idea of what it may take to spread our wings across the Milky Way in a recent article for Scientific American, excerpted here.

It will be many centuries before humans move beyond our solar system. But, before we do so I’d propose that we get our own house in order first. That will be our biggest challenge, not the invention of yet to be imagined technologies.

From Scientific American:

The idea that humans will eventually travel to and inhabit other parts of our galaxy was well expressed by the early Russian rocket scientist Konstantin Tsiolkovsky, who wrote, “Earth is humanity’s cradle, but you’re not meant to stay in your cradle forever.” Since then the idea has been a staple of science fiction, and thus become part of a consensus image of humanity’s future. Going to the stars is often regarded as humanity’s destiny, even a measure of its success as a species. But in the century since this vision was proposed, things we have learned about the universe and ourselves combine to suggest that moving out into the galaxy may not be humanity’s destiny after all.

The problem that tends to underlie all the other problems with the idea is the sheer size of the universe, which was not known when people first imagined we would go to the stars. Tau Ceti, one of the closest stars to us at around 12 light-years away, is 100 billion times farther from Earth than our moon. A quantitative difference that large turns into a qualitative difference; we can’t simply send people over such immense distances in a spaceship, because a spaceship is too impoverished an environment to support humans for the time it would take, which is on the order of centuries. Instead of a spaceship, we would have to create some kind of space-traveling ark, big enough to support a community of humans and other plants and animals in a fully recycling ecological system.

On the other hand it would have to be small enough to accelerate to a fairly high speed, to shorten the voyagers’ time of exposure to cosmic radiation, and to breakdowns in the ark. Regarded from some angles bigger is better, but the bigger the ark is, the proportionally more fuel it would have to carry along to slow itself down on reaching its destination; this is a vicious circle that can’t be squared. For that reason and others, smaller is better, but smallness creates problems for resource metabolic flow and ecologic balance. Island biogeography suggests the kinds of problems that would result from this miniaturization, but a space ark’s isolation would be far more complete than that of any island on Earth. The design imperatives for bigness and smallness may cross each other, leaving any viable craft in a non-existent middle.

The biological problems that could result from the radical miniaturization, simplification and isolation of an ark, no matter what size it is, now must include possible impacts on our microbiomes. We are not autonomous units; about eighty percent of the DNA in our bodies is not human DNA, but the DNA of a vast array of smaller creatures. That array of living beings has to function in a dynamic balance for us to be healthy, and the entire complex system co-evolved on this planet’s surface in a particular set of physical influences, including Earth’s gravity, magnetic field, chemical make-up, atmosphere, insolation, and bacterial load. Traveling to the stars means leaving all these influences, and trying to replace them artificially. What the viable parameters are on the replacements would be impossible to be sure of in advance, as the situation is too complex to model. Any starfaring ark would therefore be an experiment, its inhabitants lab animals. The first generation of the humans aboard might have volunteered to be experimental subjects, but their descendants would not have. These generations of descendants would be born into a set of rooms a trillion times smaller than Earth, with no chance of escape.

In this radically diminished enviroment, rules would have to be enforced to keep all aspects of the experiment functioning. Reproduction would not be a matter of free choice, as the population in the ark would have to maintain minimum and maximum numbers. Many jobs would be mandatory to keep the ark functioning, so work too would not be a matter of choices freely made. In the end, sharp constraints would force the social structure in the ark to enforce various norms and behaviors. The situation itself would require the establishment of something like a totalitarian state.

Read the entire article here.

Image: The Milky Way panorama. Courtesy: ESO/S. Brunier – Licensed under Creative Commons.

MondayMap: Our New Address — Laniakea


Once upon a time we humans sat smugly at the center of the universe. Now, many of us (though, not yet all) know better. Over the the last several centuries we learned and accepted that the Earth spun around the nearest Star, and not the converse. We then learned that the Sun formed part of an immense galaxy, the Milky Way, itself spinning in a vast cosmological dance. More recently, we learned that the Milky Way formed part of a larger cluster of galaxies, known as the Local Group.

Now we find that our Local Group is a mere speck within an immense supercluster containing around 100,000 galaxies spanning half a billion light years. Researchers have dubbed this galactic supercluster, rather aptly, Laniakea, Hawaiian for “immense heaven”. Laniakea is your new address. And, fascinatingly, Laniakea is moving towards an even larger grouping of galaxies named the Shapely supercluster.

From the Guardian:

In what amounts to a back-to-school gift for pupils with nerdier leanings, researchers have added a fresh line to the cosmic address of humanity. No longer will a standard home address followed by “the Earth, the solar system, the Milky Way, the universe” suffice for aficionados of the extended astronomical location system.

The extra line places the Milky Way in a vast network of neighbouring galaxies or “supercluster” that forms a spectacular web of stars and planets stretching across 520m light years of our local patch of universe. Named Laniakea, meaning “immeasurable heaven” in Hawaiian, the supercluster contains 100,000 large galaxies that together have the mass of 100 million billion suns.

Our home galaxy, the Milky Way, lies on the far outskirts of Laniakea near the border with another supercluster of galaxies named Perseus-Pisces. “When you look at it in three dimensions, is looks like a sphere that’s been badly beaten up and we are over near the edge, being pulled towards the centre,” said Brent Tully, an astronomer at the University of Hawaii in Honolulu.

Astronomers have long known that just as the solar system is part of the Milky Way, so the Milky Way belongs to a cosmic structure that is much larger still. But their attempts to define the larger structure had been thwarted because it was impossible to work out where one cluster of galaxies ended and another began.

Tully’s team gathered measurements on the positions and movement of more than 8,000 galaxies and, after discounting the expansion of the universe, worked out which were being pulled towards us and which were being pulled away. This allowed the scientists to define superclusters of galaxies that all moved in the same direction (if you’re reading this story on a mobile device, click here to watch a video explaining the research).

The work published in Nature gives astronomers their first look at the vast group of galaxies to which the Milky Way belongs. A narrow arch of galaxies connects Laniakea to the neighbouring Perseus-Pisces supercluster, while two other superclusters called Shapley and Coma lie on the far side of our own.

Tully said the research will help scientists understand why the Milky Way is hurtling through space at 600km a second towards the constellation of Centaurus. Part of the reason is the gravitational pull of other galaxies in our supercluster.

“But our whole supercluster is being pulled in the direction of this other supercluster, Shapley, though it remains to be seen if that’s all that’s going on,” said Tully.

Read the entire article here or the nerdier paper here.

Image: Laniakea: Our Home Supercluster of Galaxies. The blue dot represents the location of the Milky Way. Courtesy: R. Brent Tully (U. Hawaii) et al., SDvision, DP, CEA/Saclay.

Our Beautiful Galaxy

We should post stunning images of the night sky like these more often. For most of us, unfortunately, light pollution from our surroundings hides beautiful vistas like these from the naked eye.

Image: Receiving the Galatic Beam. The Milky Way appears to line up with the giant 64-m dish of the radio telescope at Parkes Observatory in Australia. As can be seen from the artificial lights around the telescope, light pollution is not a problem for radio astronomers. Radio and microwave interference is a big issue however, as it masks the faint natural emissions from distant objects in space. For this reason many radio observatories ban mobile phone use on their premises. Courtesy: Wayne England / The Royal Observatory Greenwich / Telegraph.

100 Million Year Old Galactic Echo

Cosmologists have found what they believe to be the echoes of a galactic collision some 100 million years ago with our own Milky Way galaxy.

[div class=attrib]From Symmetry Magazine:[end-div]

Our galaxy, the Milky Way, is a large spiral galaxy surrounded by dozens of smaller satellite galaxies. Scientists have long theorized that occasionally these satellites will pass through the disk of the Milky Way, perturbing both the satellite and the disk. A team of astronomers from Canada and the United States have discovered what may well be the smoking gun of such an encounter, one that occurred close to our position in the galaxy and relatively recently, at least in the cosmological sense.

“We have found evidence that our Milky Way had an encounter with a small galaxy or massive dark matter structure perhaps as recently as 100 million years ago,” said Larry Widrow, professor at Queen’s University in Canada. “We clearly observe unexpected differences in the Milky Way’s stellar distribution above and below the Galaxy’s midplane that have the appearance of a vertical wave — something that nobody has seen before.”

The discovery is based on observations of some 300,000 nearby Milky Way stars by the Sloan Digital Sky Survey. Stars in the disk of the Milky Way move up and down at a speed of about 20-30 kilometers per second while orbiting the center of the galaxy at a brisk 220 kilometers per second. Widrow and his four collaborators from the University of Kentucky, the University of Chicago and Fermi National Accelerator Laboratory have found that the positions and motions of these nearby stars weren’t quite as regular as previously thought.

“Our part of the Milky Way is ringing like a bell,” said Brian Yanny, of the Department of Energy’s Fermilab. “But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo.”

Adds Susan Gardner, professor of physics at the University of Kentucky: “The perturbation need not have been a single isolated event in the past, and it may even be ongoing. Additional observations may well clarify its origin.”

When the collaboration started analyzing the SDSS data on the Milky Way, they noticed a small but statistically significant difference in the distribution of stars north and south of the Milky Way’s midplane. For more than a year, the team members explored various explanations of this north-south asymmetry, such as the effect of interstellar dust on distance determinations and the way the stars surveyed were selected. When those attempts failed, they began to explore the alternative explanation that the data was telling them something about recent events in the history of the Galaxy.

The scientists used computer simulations to explore what would happen if a satellite galaxy or dark matter structure passed through the disk of the Milky Way. The simulations indicate that over the next 100 million years or so, our galaxy will “stop ringing:” the north-south asymmetry will disappear and the vertical motions of stars in the solar neighborhood will revert back to their equilibrium orbits — unless we get hit again.

[div class=attrib]Read the entire article after the jump.[end-div]

The 100 Million Year Collision

Four billion, or so, years from now, our very own Milky Way galaxy is expected to begin a slow but enormous collision with its galactic sibling, the Andromeda galaxy. Cosmologists predict the ensuing galactic smash will take around 100 million years to complete. It’s a shame we’ll not be around to witness the spectacle.

[div class=attrib]From Scientific American:[end-div]

The galactic theme in the context of planets and life is an interesting one. Take our own particular circumstances. As unappealingly non-Copernican as it is, there is no doubt that the Milky Way galaxy today is ‘special’. This should not be confused with any notion that special galaxy=special humans, since it’s really not clear yet that the astrophysical specialness of the galaxy has significant bearing on the likelihood of us sitting here picking our teeth. Nonetheless, the scientific method being what it is, we need to pay attention to any and all observations with as little bias as possible – so asking the question of what a ‘special’ galaxy might mean for life is OK, just don’t get too carried away.

First of all the Milky Way galaxy is big. As spiral galaxies go it’s in the upper echelons of diameter and mass. In the relatively nearby universe, it and our nearest large galaxy, Andromeda, are the sumo’s in the room. This immediately makes it somewhat unusual, the great majority of galaxies in the observable universe are smaller. The relationship to Andromeda is also very particular. In effect the Milky Way and Andromeda are a binary pair, our mutual distortion of spacetime is resulting in us barreling together at about 80 miles a second. In about 4 billion years these two galaxies will begin a ponderous collision lasting for perhaps 100 million years or so. It will be a soft type of collision – individual stars are so tiny compared to the distances between them that they themselves are unlikely to collide, but the great masses of gas and dust in the two galaxies will smack together – triggering the formation of new stars and planetary systems.

Some dynamical models (including those in the most recent work based on Hubble telescope measurements) suggest that our solar system could be flung further away from the center of the merging galaxies, others indicate it could end up thrown towards the newly forming stellar core of a future Goliath galaxy (Milkomeda?). Does any of this matter for life? For us the answer may be moot. In about only 1 billion years the Sun will have grown luminous enough that the temperate climate we enjoy on the Earth may be long gone. In 3-4 billion years it may be luminous enough that Mars, if not utterly dried out and devoid of atmosphere by then, could sustain ‘habitable‘ temperatures. Depending on where the vagaries of gravitational dynamics take the solar system as Andromeda comes lumbering through, we might end up surrounded by the pop and crackle of supernova as the collision-induced formation of new massive stars gets underway. All in all it doesn’t look too good. But for other places, other solar systems that we see forming today, it could be a very different story.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image: Composition of Milky Way and Andromeda. Courtesy of NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas, and A. Mellinger).[end-div]