Tag Archives: Dark Energy

NASA Space Place – Size Does Matter, But So Does Dark Energy

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in August, 2013.

By Dr. Ethan Siegel

2013february2_spaceplaceHere in our own galactic backyard, the Milky Way contains some 200-400 billion stars, and that’s not even the biggest galaxy in our own local group. Andromeda (M31) is even bigger and more massive than we are, made up of around a trillion stars! When you throw in the Triangulum Galaxy (M33), the Large and Small Magellanic Clouds, and the dozens of dwarf galaxies and hundreds of globular clusters gravitationally bound to us and our nearest neighbors, our local group sure does seem impressive.

Yet that’s just chicken feed compared to the largest structures in the universe. Giant clusters and superclusters of galaxies, containing thousands of times the mass of our entire local group, can be found omnidirectionally with telescope surveys. Perhaps the two most famous examples are the nearby Virgo Cluster and the somewhat more distant Coma Supercluster, the latter containing more than 3,000 galaxies. There are millions of giant clusters like this in our observable universe, and the gravitational forces at play are absolutely tremendous: there are literally quadrillions of times the mass of our Sun in these systems.

The largest superclusters line up along filaments, forming a great cosmic web of structure with huge intergalactic voids in between the galaxy-rich regions. These galaxy filaments span anywhere from hundreds of millions of light-years all the way up to more than a billion light years in length. The CfA2 Great Wall, the Sloan Great Wall, and most recently, the Huge-LQG (Large Quasar Group) are the largest known ones, with the Huge-LQG — a group of at least 73 quasars – apparently stretching nearly 4 billion light years in its longest direction: more than 5% of the observable universe! With more mass than a million Milky Way galaxies in there, this structure is a puzzle for cosmology.

You see, with the normal matter, dark matter, and dark energy in our universe, there’s an upper limit to the size of gravitationally bound filaments that should form. The Huge-LQG, if real, is more than double the size of that largest predicted structure, and this could cast doubts on the core principle of cosmology: that on the largest scales, the universe is roughly uniform everywhere. But this might not pose a problem at all, thanks to an unlikely culprit: dark energy. Just as the local group is part of the Virgo Supercluster but recedes from it, and the Leo Cluster — a large member of the Coma Supercluster — is accelerating away from Coma, it’s conceivable that the Huge-LQG isn’t a single, bound structure at all, but will eventually be driven apart by dark energy. Either way, we’re just a tiny drop in the vast cosmic ocean, on the outskirts of its rich, yet barely fathomable depths.

Learn about the many ways in which NASA strives to uncover the mysteries of the universe: science.nasa.gov/astrophysics/. Kids can make their own clusters of galaxies by checking out The Space Place’s fun galactic mobile activity: spaceplace.nasa.gov/galactic-mobile/


Caption: Digital mosaic of infrared light (courtesy of Spitzer) and visible light (SDSS) of the Coma Cluster, the largest member of the Coma Supercluster. Image credit: NASA / JPL-Caltech / Goddard Space Flight Center / Sloan Digital Sky Survey.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

About NASA Space Place

The goal of the NASA Space Place is “to inform, inspire, and involve children in the excitement of science, technology, and space exploration.” More information is available at their website: http://spaceplace.nasa.gov/

Kopernik Winter Star Party – This Saturday, February 23rd

The Kopernik Astronomical Society is hosting its 2013 Winter Star Party this coming Saturday (Feb. 23) from 6:00 p.m. to as late as people are likely to observe from the best equipped society observatory in CNY. A few with CNYO will be there for an evening of lectures, twizzlers, and what we hope will be clear skies. Directions to Kopernik (which also hosts year-long Friday Night observing sessions from March to November) are provided below:

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Event details are reproduced below. But see the Kopernik website for all of the event information!

Winter Star Party

Featuring NASA Scientist Michelle Thaller!

Saturday, February 23, 2013

6:00 PM – Members-Only Reception (light refreshments provided)

KOSC Members are invited to attend this informal reception to meet other members, get some early views through the telescopes (weather permitting), and kick off the Winter Star Party!

6:30 PM – Doors Open to the Public

Enjoy telescope observing (if clear) or tours (if cloudy). Take a tour through part of our galaxy with GeoWall, our special 3D projection system. Kids get to make and take home their own miniature Jupiter model.

7:00 PM – Comet Preview 2013

Roy Williams, KOSC – Enjoy a short presentation about two comets heading this way and learn how to get ready to observe these rare heavenly sights. See a comet made right in front of your eyes!

7:30 PM – Mikolaj Kopernik Birthday Celebration

Polish astronomer and mathematician Mikolaj Kopernik, known in English as Nicolaus Copernicus, was born February 19, 1473. Help us celebrate his 540th birthday with cake and special Polish desserts.

8:00 PM – Things That Go Bump in the Dark

Dr. Michelle Thaller, NASA Goddard Spaceflight Center – Astronomers think that everything we see in the universe makes up less than 4% of what actually is in the universe. How could this be? Is regular matter really such a small part of the universe? Newly discovered dark matter and dark energy are seriously mysterious things, however, experts are getting better at detecting and mapping both. What they are finding out is astonishing. These dark matter maps raise questions about the entire history of the universe, including how galaxies, stars, and planets formed in the first place. Dark energy may determine the fate of all matter, dark or otherwise, that exists.

Come find out about these things that go bump in the dark!


Click on the image for the event PDF