NATURE: The Laniakea supercluster of galaxies

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MargaritaMc
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NATURE: The Laniakea supercluster of galaxies

Post by MargaritaMc » Fri Sep 05, 2014 4:10 pm

NATURE
The Laniakea supercluster of galaxies
R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède


Nature 513, 71–73 (04 September 2014) doi:10.1038/nature13674
Received 07 April 2014 Accepted 07 July 2014 Published online 03 September 2014


Galaxies congregate in clusters and along filaments, and are missing from large regions referred to as voids. These structures are seen in maps derived from spectroscopic surveys1, 2 that reveal networks of structure that are interconnected with no clear boundaries. Extended regions with a high concentration of galaxies are called ‘superclusters’, although this term is not precise. There is, however, another way to analyse the structure. If the distance to each galaxy from Earth is directly measured, then the peculiar velocity can be derived from the subtraction of the mean cosmic expansion, the product of distance times the Hubble constant, from observed velocity. The peculiar velocity is the line-of-sight departure from the cosmic expansion and arises from gravitational perturbations; a map of peculiar velocities can be translated into a map of the distribution of matter3. Here we report a map of structure made using a catalogue of peculiar velocities. We find locations where peculiar velocity flows diverge, as water does at watershed divides, and we trace the surface of divergent points that surrounds us. Within the volume enclosed by this surface, the motions of galaxies are inward after removal of the mean cosmic expansion and long range flows. We define a supercluster to be the volume within such a surface, and so we are defining the extent of our home supercluster, which we call Laniakea.
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NRAO

excerpt

Newly Identified Galactic Supercluster Is Home to the Milky Way

Astronomers using the National Science Foundation’s Green Bank Telescope (GBT) -- among other telescopes -- have determined that our own Milky Way galaxy is part of a newly identified ginormous supercluster of galaxies, which they have dubbed “Laniakea,” which means “immense heaven” in Hawaiian.

This discovery clarifies the boundaries of our galactic neighborhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe.

“We have finally established the contours that define the supercluster of galaxies we can call home,” said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa. “This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.”

The paper explaining this work is the cover story of the September 4 issue of the journal Nature.
A slice of the Laniakea Supercluster in the supergalactic equatorial plane -- an imaginary plane containing many of the most massive clusters in this structure. The colors represent density within this slice, with red for high densities and blue for voids -- areas with relatively little matter. Individual galaxies are shown as white dots. Velocity flow streams within the region gravitationally dominated by Laniakea are shown in white, while dark blue flow lines are away from the Laniakea local basin of attraction. The orange contour encloses the outer limits of these streams, a diameter of about 160 Mpc. This region contains the mass of about 100 million billion suns. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France


Margarita
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
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Re: NATURE: The Laniakea supercluster of galaxies

Post by rstevenson » Fri Sep 05, 2014 6:16 pm

My mind just stretched. If it keeps stretching like this, it may just float away.

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Re: NATURE: The Laniakea supercluster of galaxies

Post by BDanielMayfield » Sun Sep 07, 2014 2:11 pm

Laniakea looks to be about ten times bigger than what we used to call the Local Supercluster. The Virgo cluster that our itty bitty local group is an outlier of resembles a branch of a much larger tree.

By the way, how is Laniakea to be pronounced?

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Re: NATURE: The Laniakea supercluster of galaxies

Post by bystander » Sun Sep 07, 2014 9:04 pm

Click to play embedded YouTube video.
Hawaii Scientist Maps, Names Laniakea, Our Home Supercluster of Galaxies
University of Hawaii | Institute for Astronomy | 2014 Sep 03

The Laniakea Supercluster of Galaxies - R. Brent Tully et al
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Re: NATURE: The Laniakea supercluster of galaxies

Post by MargaritaMc » Tue Sep 09, 2014 3:22 pm

Two more articles about Laniakea in NATURE: which I missed!

EDITORIAL
Heavenly homes
The discovery of our Galaxy’s place in the Universe adds detail to our address.


As Tim Radford, former science editor of The Guardian newspaper, noted in his 2011 book The Address Book, inquisitive schoolchildren the world over have a certain ritual. Handed a new exercise book and asked to add their name and address, they do so on a Universal scale. House number, street, town and country, postcode even, are followed by their designated continent and the name of our planet. Up the cosmic scale they go, noting the Solar System then the Milky Way, before offering the final identifier: the Universe.
It sounds precise; it is anything but. Most difficult for a deep-space postal service would be the first jump, from the infinite stretch of the known Universe down to our local Galaxy, the Milky Way. Well, things just got a little easier. (Although perhaps not for Radford, who may need to update his book.) This week, scientists add a new line to our planetary coordinates: the Laniakea galaxy supercluster.
NEWS ARTICLE
Earth's new address: 'Solar System, Milky Way, Laniakea'
Analysis of galaxies shows local supercluster to be 100 times larger than previously thought.

Elizabeth Gibney
... Galaxies tend to huddle in groups called clusters; regions where these clusters are densely packed are known as superclusters. But the definition of these massive cosmic structures is vague.

The new study, published in Nature, describes a novel way to define where one supercluster ends and another begins.
... The team used a database that compiles the velocities of 8,000 galaxies, calculated after subtracting the average rate of cosmic expansion. “All these deviations are due to the gravitational pull galaxies feel around them, which comes from mass,” says Tully. ...

This is a completely new definition of a supercluster. Scientists previously placed the Milky Way in the Virgo Supercluster, but under Tully and colleagues' definition, this region becomes just an appendage of the much larger Laniakea, which is 160 million parsecs (520 million light years) across and contains the mass of 100 million billion Suns.

However, this work is unlikely to be the final word on what a supercluster is, says Gayoung Chon, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. Her team works on a different definition, based on superclusters being structures that will one day collapse into a single object. This will not happen to Laniakea, she estimates, because some of the galaxies within it will recede from one another forever. “The definition you use really depends on the questions you want to ask. This latest method is a very good way to chart the large-scale structures of the Universe, but it doesn’t ask what will happen to these superclusters eventually,” she says.
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
— Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: NATURE: The Laniakea supercluster of galaxies

Post by Ann » Tue Sep 09, 2014 3:56 pm

Her team works on a different definition, based on superclusters being structures that will one day collapse into a single object.
Mom, what's that galaxy?

Well dear, that's Virgo.

:shock:

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Re: NATURE: The Laniakea supercluster of galaxies

Post by MargaritaMc » Thu Oct 02, 2014 12:10 pm

Just to note that there is a useful astrobite on this subject today.

http://astrobites.org/2014/10/01/the-bo ... ercluster/
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
— Dr Debra M. Elmegreen, Fellow of the AAAS