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Moment that mattered: Scientists announce the discovery of the Laniakea

September saw a fantastic moment in science, but one that went almost completely unreported outside of the journals. A group of astronomers [led by R Brent Tully from the University of Hawaii] revealed that our galaxy [marked with a red arrow on image, left] is part of a supercluster of galaxies. They called it Laniakea – pronounced la-nee-uh-kay-uh – which means ‘immeasurable heaven’ in Hawaiian.

The easiest way to think about it is how kids set about trying to describe their address in the utmost detail. So it’s this house number, on this street, in this city, in this county, in this country, the Earth, the Milky Way, the universe. Well, now they’ve added a new level to that address, between Milky Way and universe – ‘the Laniakea’, our supercluster.

Why does this matter? Because it’s literally another layer to our universe. It’s not as seminal as discovering the Big Bang, but you can’t get much bigger than talking about a supercluster. It helps us better understand the distribution of matter in the universe, which is important for a few reasons. It helps us know what happened during the first moments after the Big Bang. Knowing this might help us, in turn, understand things like why matter and not anti-matter predominates in our neck of the universe, or why dark matter and dark energy dominate the universe overall.

The Laniakea is about 500 million light years wide and contains 100,000 galaxies. On some level we will never get our heads around the size of that – superclusters are just too big and we humans are just too puny. But you can at least get at these things by using analogies. Consider that Laniakea is roughly 160 megaparsecs across. How big is that distance? If you started counting one mile per second, it would take you 95 trillion years to count them all. It’s still mind-blowing, but it gives you a sense of the scales involved.

The discovery of the Laniakea shows how far we can go with these space-age telescopes. How far we can reach back and reconstruct where we came from, what our little area of the universe is like. Tully and his associates were monitoring the other galaxies involved by tracking red- and blue-shifts – the Doppler effect you see when light is moving toward or away from you.

That’s the same basic technique that [the great American astronomer] Edwin Hubble used almost a century ago to discover that the universe is expanding in the first place. So in that way, these astronomers are really following in the footsteps of his work.

The biggest, most cosmic idea out there is the origins of where we came from, and the Laniakea is a key piece of that puzzle. It’s a trick of perspective to think that these seismic moments are rarer these days than before, that we’ve stopped discovering, that the golden age of science is over. If you look back in history it’s easy to pick a decade in the past and say, ‘That was when things were happening; there’s nothing left to discover today.’ But that’s not true. It’s just that it’s not immediately obvious how important these moments are.

There are probably more fundamental discoveries going on now than there ever were before. These moments, these discoveries, will ultimately change how we view the world and thankfully they never stop coming.


Sam Kean is the author of ‘The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness and Recovery’, published by Transworld.

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