APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4205
Joined: Fri Dec 04, 2009 3:27 am

APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by APOD Robot » Mon Jan 20, 2014 5:06 am

Image Baryon Acoustic Oscillations from SDSS III

Explanation: How large do things appear when far away? When peering across the universe, the answer can actually tell us about its average gravitational history and hence its composition. Toward this goal, the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey-III (SDSS-III) has measured slight recurring density enhancements in galaxy densities up to six billion light years away (redshift 0.7), when the universe was about half its current age. These density ripples are known as baryon acoustic oscillations (BAOs) and are expected to emerge from the early universe at a known size scale. BOSS's measurements of this size scale indicate a strong universe component of dark energy, and so bolsters previous indications of this unusual composition. Pictured above is an artist's illustration depicting exaggerated BAOs in the distant universe.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Beyond » Mon Jan 20, 2014 5:20 am

Well, this certainly is a different than usual APOD. :yes:
To find the Truth, you must go Beyond.

User avatar
geckzilla
Ocular Digitator
Posts: 9152
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by geckzilla » Mon Jan 20, 2014 5:26 am

It's also easily one of the most confusing APODs. I can't say I understand it at all even after reading it several times and checking the links. "Cosmic sound" is a new concept to me.
Just call me "geck" because "zilla" is like a last name.

User avatar
Nitpicker
Inverse Square
Posts: 2692
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Nitpicker » Mon Jan 20, 2014 5:37 am

Not sure I even know how to ask an intelligent question about this one. What does the white annotated "dumbbell" indicate?

User avatar
geckzilla
Ocular Digitator
Posts: 9152
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by geckzilla » Mon Jan 20, 2014 5:48 am

BAOs can be used as a "standard ruler" (white line) to measure the distances to all the galaxies in the universe.
I dunno, man. I just don't know. I'd call it a BAO radius. The illustration makes it look like they are all the same distance but the measurement isn't specified. I'm trying to figure out what the connection between this and something like a Cepheid as a standard candle would be. I don't get it! Is it supposed to be distance from our position or distance between any two points?
Just call me "geck" because "zilla" is like a last name.

User avatar
Nitpicker
Inverse Square
Posts: 2692
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Nitpicker » Mon Jan 20, 2014 6:13 am

Thanks geckzilla.

According to: http://en.wikipedia.org/wiki/Baryon_aco ... cillations, the length of the standard ruler is ~490 million light years in today's universe.

So, presumably, the BAO radii -- indicated by regions of higher densities of galaxies -- is measured smaller than today's standard, when you look further away/ago? I'm still missing a few critical details, me thinks.

User avatar
Ann
4725 Å
Posts: 11171
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Ann » Mon Jan 20, 2014 6:30 am

When I was fifteen years old or so, and had just become really, really interested in astronomy, I learnt that the universe might be going to collapse. That was definitely the most frightening piece of news I had ever come across (apart from the time my grandfather told me that I had to prepare for the end of the world). Well, the end of the universe is a bit worse than the end of the world, isn't?

That's why I was jubilantly happy in 1999(?), when it was first announced that the universe appears to be accelerating. So it is not about to collapse, at least not in the foreseeable future!! Woopee!!!

I know... a too-accelerating universe spells doom, too. But I'm a claustrophobiac, so I prefer a universe that just grows larger and larger over one that collapses to a single point.

I don't pretend to understand today's APOD, but I'll happily accept that it portrays a dark energy-dominated universe.

Ann
Color Commentator

User avatar
geckzilla
Ocular Digitator
Posts: 9152
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by geckzilla » Mon Jan 20, 2014 6:49 am

That's very odd, Ann. Heat death has to be the most depressing possible end the Universe could face. The idea that it could one day collapse and then be somehow reborn again in a new big bang was quite cheerful.
Just call me "geck" because "zilla" is like a last name.

User avatar
Nitpicker
Inverse Square
Posts: 2692
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Nitpicker » Mon Jan 20, 2014 6:58 am

I agree geckzilla. I grew up with great hope for the future, based on the supposed Big Crunch theory. I have been slightly more nihilistic ever since learning that this Universe is instead likely to be a fizzer.

Karthik
Ensign
Posts: 20
Joined: Tue Nov 07, 2006 2:38 pm

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Karthik » Mon Jan 20, 2014 7:06 am

Anyone knows how this is related to the large-scale structure of the Universe derived from the Redshift surveys?
In recent studies the universe appears as a collection of giant bubble-like voids separated by sheets and filaments of galaxies, with the superclusters appearing as occasional relatively dense nodes.
- http://en.wikipedia.org/wiki/Large-scal ... _structure
I first thought that the circles shown in the APOD are the "bubbles" but their insides are not void. There is an dense region in the centre of each bubble. Are the bubbles, sheets, filaments and voids present in the central, dense(r) region?

Thanks

User avatar
alter-ego
Serendipitous Sleuthhound
Posts: 897
Joined: Mon Apr 21, 2008 4:51 am
Location: Redmond, WA

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by alter-ego » Mon Jan 20, 2014 7:45 am

geckzilla wrote:
BAOs can be used as a "standard ruler" (white line) to measure the distances to all the galaxies in the universe.
I dunno, man. I just don't know. I'd call it a BAO radius. The illustration makes it look like they are all the same distance but the measurement isn't specified. I'm trying to figure out what the connection between this and something like a Cepheid as a standard candle would be. I don't get it! Is it supposed to be distance from our position or distance between any two points?
As I understand it, cosmological theory requires the size of these slightly higher density baryon bubbles be constrained by the CMB data which lead to a "standard candle". I.e. the evolution over time (hence redshift, Z) of the angular size(s) of the baryon bubbles must correlated to the initial ripple structure seen in the CMB. At recombination the ripple structure is essentially locked in. By looking at the distribution of angular BAO radii (power spectrum) at different redshifts, additional tighter-constraint comparisons to theory can be made. So within the standard ΛCDM model, the data supports an accelerating expansion.

In reality, the ripple pattern is complicated. There are a distribution of sizes like the CMB power spectrum, and the mutual gravitational interaction of mass, e.g. galaxies, over time muddies the water too. But statistically speaking, for large numbers of galaxies, signs of the original acoustic oscillations are observable.

http://arxiv.org/pdf/1312.4877v1.pdf
A pessimist is nothing more than an experienced optimist

User avatar
stephen63
Science Officer
Posts: 304
Joined: Sat Jan 12, 2013 2:53 am
Location: Pa

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by stephen63 » Mon Jan 20, 2014 7:51 am

This link may be a simple analogy. Instead of changing the frequency, maybe changing the volume(of the universe) will determine the size of the spheres.
Then again, maybe not!
Click to play embedded YouTube video.

User avatar
orin stepanek
Plutopian
Posts: 6052
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by orin stepanek » Mon Jan 20, 2014 12:25 pm

:?: :shock:
Orin

Smile today; tomorrow's another day!

BDanielMayfield
Don't bring me down
Posts: 2524
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by BDanielMayfield » Mon Jan 20, 2014 1:12 pm

This is definitely the hardest apod to understand that I’ve seen. I hope this one is omitted from the final exam.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

Tim Kreider

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Tim Kreider » Mon Jan 20, 2014 1:18 pm

I have to agree this is illustration/caption is just about unintelligible, even on slow, word-by-word re-reading. Maybe it's not a concept that lends itself to easy explanation, but I think some editorial feedback from an intelligent layperson a would've helped.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17850
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Hey hey hey, BAOs

Post by neufer » Mon Jan 20, 2014 1:46 pm

BAOs can be used as a "standard ruler" (white line) to measure the distances to all the galaxies in the universe.
http://www.huffingtonpost.com/2014/01/18/national-zoo-panda-bao-bao_n_4623859.html wrote:
[img3="My "precious" : BAOs"]http://images.politico.com/global/2014/ ... 05_605.jpg[/img3]
WASHINGTON, Jan 18 (Reuters) - The nation's capital gained a new star on Saturday when the National Zoo's 4-month-old panda bear cub made her debut to long lines of visitors.

The panda cub, Bao Bao, went on exhibit at the Giant Bear Habitat, accompanied by her mother, Mei Xiang, said zoo spokeswoman Annalisa Meyer. "She's doing great. She's sleeping right now, she's doing what pandas do," she said. Visitors began lining up well before the 8 a.m. EST (1300 GMT) opening time, with 60 to 80 people being admitted at 10-minute intervals, Meyer said. Bao Bao, whose name means "precious" or "treasure," has been a star since her birth on Aug. 23 was broadcast live on the zoo's panda cam. The cub will be on exhibit for a few hours every day.
Art Neuendorffer

Tszabeau

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Tszabeau » Mon Jan 20, 2014 2:42 pm

In this artist's illustration, does anyone know if the portrayed galaxies are constructed from, actual, astronomical photography or are they painted digitally or by hand?

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17850
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by neufer » Mon Jan 20, 2014 3:04 pm

http://www.sdss3.org/surveys/boss.php wrote: <<The SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS) will map the spatial distribution of luminous red galaxies (LRGs) and quasars to detect the characteristic scale imprinted by baryon acoustic oscillations in the early universe. Sound waves that propagate in the early universe, like spreading ripples in a pond, imprint a characteristic scale on cosmic microwave background fluctuations. These fluctuations have evolved into today's walls and voids of galaxies, meaning this baryon acoustic oscillation (BAO) scale (about 150 Mpc) is visible among galaxies today. This concept is illustrated below (some of the relative scales have been exaggerated for illustration purposes). The baryon acoustic oscillation imprint a fixed scale in the universe just 300,000 years after the Big Bang (shown as white circles). These ripples in the density of matter even remain today in the distribution of galaxies and BOSS is designed to measure the size of these ripples better than any other existing survey.>>
Art Neuendorffer

User avatar
Psnarf
Science Officer
Posts: 316
Joined: Fri Feb 26, 2010 6:19 pm

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Psnarf » Mon Jan 20, 2014 3:23 pm

https://www.sdss3.org/surveys/boss.php
Yes, Boss! In a far, far away place, a long, long time ago, da U propagated sound waves that left imprints on the cosmic microwave radiation? Wow, heavy! Sure, no problem. Them pesky baryons must have been pretty active back then.
A wimp and a wino walk into a bar.... Charming. A proton and neutron are types of baryons, each with three quarks, according to the Ferengi Rules of Acquisition. Unaccompanied by a nucleus, a neutron lasts for about 15 minutes before the W boson decides to leave behind a proton, electron and an anti-electron neutrino. I have to wonder what goes on in the nucleus of a neutron star. I used to think there are not any neutrons near the center of a super-massive neutron star, just free baryons. When a neutron star collapses into a black hole, there can't be any neutrons, just neutron parts, because the gluons aren't strong enough to maintain a crystal structure.
http://arxiv.org/abs/1108.1859v1

Exactly what is a baryon? Is it a point in spacetime that vibrates at a particular frequency? What are the characteristics of a neutron shell that prevents free quarks from zipping about untethered at the center of a neutron star, much like the outer-shell electrons of a conductive metal?
brain.explode.jpg
You do not have the required permissions to view the files attached to this post.

User avatar
Chris Peterson
Abominable Snowman
Posts: 15649
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 3:56 pm

geckzilla wrote:I dunno, man. I just don't know. I'd call it a BAO radius. The illustration makes it look like they are all the same distance but the measurement isn't specified. I'm trying to figure out what the connection between this and something like a Cepheid as a standard candle would be. I don't get it! Is it supposed to be distance from our position or distance between any two points?
I don't believe that this image really shows BAOs as suggested. Rather, I think it shows the consequence of BAOs.

BAOs no longer exist (although I think the term may still be used for the consequential structure in some cases). They were a phenomenon of the early universe, when it consisted of an electron/baryon plasma. At that stage, sound waves introduced structure, in the form of density variations. That structure was preserved once the universe cooled and galaxies formed.

Here's an analogy. Ripples form on the surface of a pond because of the way sound travels in water. By studying the ripples, you can learn a lot about the physical nature of water. Suppose a burst of hail hits a pond, creating thousands of individual ripple rings. These run into each other, producing a complex surface that we can observe. We'd certainly not see anything like circles in that surface (which is what the APOD somewhat incorrectly shows). But if we measured carefully, we'd see certain recurring wavelengths, certain periodic structures. And from those, we could work backwards to the sound velocity in water. What we see in the Universe when we look around is a filamentary structure, and by looking at it the same way, we can work backwards to infer conditions in the early plasma universe, and confirm that they are consistent with our cosmology models (which include dark matter and dark energy).

My analogy would be better if I added a geothermal source under the pond that evaporated it into steam after the ripples formed, so we'd be looking for structure in one phase state in order to infer something about an earlier phase state.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Ron-Astro Pharmacist
Resistored Fizzacist
Posts: 889
Joined: Thu Jan 03, 2013 10:34 pm
AKA: Fred
Location: Idaho USA

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Ron-Astro Pharmacist » Mon Jan 20, 2014 4:26 pm

In this tutorial Mark Whittle gives us a bit of the repercussions of the acoustic universe.

http://www.astro.virginia.edu/~dmw8f/BB ... _home.html
Make Mars not Wars

FearNot

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by FearNot » Mon Jan 20, 2014 4:36 pm

Ann wrote:When I was fifteen years old or so, and had just become really, really interested in astronomy, I learnt that the universe might be going to collapse. That was definitely the most frightening piece of news I had ever come across (apart from the time my grandfather told me that I had to prepare for the end of the world). Well, the end of the universe is a bit worse than the end of the world, isn't?

That's why I was jubilantly happy in 1999(?), when it was first announced that the universe appears to be accelerating. So it is not about to collapse, at least not in the foreseeable future!! Woopee!!!

I know... a too-accelerating universe spells doom, too. But I'm a claustrophobiac, so I prefer a universe that just grows larger and larger over one that collapses to a single point.

I don't pretend to understand today's APOD, but I'll happily accept that it portrays a dark energy-dominated universe.

Ann
From The Hubble Site:

"The universe that was born in a violent expansion could end with an even more violent expansion called the Big Rip."

http://hubblesite.org/hubble_discoverie ... iverse.php

"I have loved the stars too fondly to be fearful of the night." http://answers.yahoo.com/question/index ... 959AAliPAj

The end of the universe is nothing to fear.

BDanielMayfield
Don't bring me down
Posts: 2524
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by BDanielMayfield » Mon Jan 20, 2014 5:02 pm

With the help of above comments from alter-ego, nuefer, and Chris the fog is beginning to lift. Even though this is a tough subject to rap one’s brain around, I’m glad it was included, because it takes mental effort to understand the universe. While it’s fun to grouse about the lack of clarity of this APOD’s illustration and description, how could this topic have been clearly explained with only one picture and one short paragraph? Clearly, it needed more :blah:, which has been provided.

Also, Psnarf, you have out Psnarfed yourself. Excellent comment. I could understand every bit of it. So clear, so insightful! It was delightful. :lol2:
:thumb_up: :thumb_up:

Bruce
Just as zero is not equal to infinity, everything coming from nothing is illogical.

User avatar
Anthony Barreiro
Turtles all the way down
Posts: 793
Joined: Wed May 11, 2011 7:09 pm
Location: San Francisco, California, Turtle Island

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Anthony Barreiro » Mon Jan 20, 2014 5:39 pm

Ron-Astro Pharmacist wrote:In this tutorial Mark Whittle gives us a bit of the repercussions of the acoustic universe.

http://www.astro.virginia.edu/~dmw8f/BB ... _home.html
Thanks, Ron. I was going to make the same suggestion. Whittle explains big bang acoustics very clearly and accessibly. He even includes sound clips of what the universe would sound like if it were in a frequency range perceptible to human ears.
May all beings be happy, peaceful, and free.

Jamesosb

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Jamesosb » Mon Jan 20, 2014 5:43 pm

My theory is that the artist didn't have a full grasp of the concept. So far, it's the best explanation I can come up with.