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So here we are on Earth, which is in the solar system, which is in the Milky Way galaxy.  But where is that, exactly?  The quick answer is, "in a big cluster of galaxies."  But until September 4th, we couldn't say how big our cluster was, or what it actually looked like, and it didn't have a name.

But now, astronomers at the University of Hawaii at Manoa can tell us exactly what our galactic neighborhood looks like.  And it turns out, it's a hundred times more massive than we thought!  

The astronomers have named it the Laniakea Supercluster, meaning "Immense Heaven" in Hawaiian.  The discovery is rooted in our basic understanding of the structure of the physical universe.  Over time, matter has attracted and collected with other matter due to gravitation.  This has created a kind of marbled looking universe with large clumps and long ribbons of matter grouped together and empty gaps in between.

In this cosmic tangle of matter, astronomers have had a hard time defining where one supercluster of galaxies begins and another ends.  To help tease out an answer, the Manoa astronomers took inspiration from geography.  On Earth, water also collects into deposits like rivers and lakes because of gravitation.  When rain falls, it either flows down one side of a mountain range or the other, and this allows us to draw dividing lines between watersheds.  

By the same logic, since galaxies are attracted toward the nearest center of gravity, we should be able to draw dividing lines between superclusters.  One one side of the line, galaxies flow toward one center of gravity, and on the other side, they flow toward another.

So the team looked at a database of 8,000 galaxies that have been observed moving either away from us, with their light giving off a Doppler shift toward red, or in the other direction, toward us, with a Doppler shift toward blue, and mapped them all out.

Our galaxy, along with a hundred thousand others, is being pulled toward a dense region astronomers call "the Great Attractor", while the others are being pulled toward another gravitational center in another direction.

So the research revealed that we're near the edge of our celestial watershed, so to speak, along with the entire Virgo Supercluster, which, until now, we thought was the supercluster that we were in.  But it turns out, that's just a little appendage of the whole, huge Laniakea Supercluster.

In addition to helping put a "You Are Here" sticker in space for us, this map demonstrates a new way some astronomers are using to study the structure of the universe.  By setting the flow of galaxies, we can better map gravity, and that can help us map matter, whether it's visible or not.  

Another exciting first step this month was the Rosetta mission's first "data baby".  Rosetta is the European Space Agency probe that's set to rendezvous with a comet known as 67P/Churyumov-Gerasimenko.  And earlier this month, it took it's first spectrographic readings of the comet using a NASA instrument called "ALICE".  It detected hydrogen and oxygen in its atmosphere.  Not surprising, because comets tend to be rich in both of these elements.  

But what did surprise scientists was that ALICE revealed no visible ice.  The thing has been sweating out water at a rate of two glasses a second, and it's too far from the sun to be full of water in liquid or vapor form.  So where is this water coming from?

No answers yet, but another surprise was that ALICE's ultraviolet scans revealed the comet to be unusually dark, described as being "darker than charcoal", which could mean it's rich in complex organic compounds, including substances that could resemble tar.

More answers about 67P await us November, when Rosetta will set its lander on the comet's surface, so check back in to learn more.  

In the meantime, thank you for watching SciShow Space News.  If you want to keep exploring the universe with us, check out subbable.com/scishow to learn how you can help support us.  And don't forget to go to YouTube.com/scishowspace and subscribe.

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