Astronomy.com blog : cosmology

Introducing Caltech’s new home for astronomy and astrophysics

Matt Quandt — Thu, 27 Aug 2009 14:34:00 GMT

A guest blog from Lynne Hillenbrand, Caltech’s executive officer of astronomy

The Cahill Center for Astronomy and Astrophysics on the campus of the California Institute of Technology, in Pasadena, California, is home to many of the world's pioneers in astronomical discovery, experiment, and theory. Our new building, opened in January, was designed to incorporate groups from across the campus into a single space and to foster their interactions, collaborations, and new discoveries.

This new crown jewel of Caltech is a hub of education and technology. Cahill's residents operate space- and ground-based observatories; develop next-generation technology and instruments; and simulate, predict, and interpret key astronomical theories. It all takes place at 1216 California Boulevard, not coincidentally the wavelength of the astrophysically important Lyman-alpha line of hydrogen.

A lap around any one of the four approximately 25,000 square-foot floors (three above ground and one underground) is likely to witness conversations on topics ranging from new planets around nearby young stars to high-redshift galaxies to signatures emanating from the early universe.

The building features a modern lecture hall and reading room; offices for more than 220 astronomers and astrophysicists, including graduate students, post-doctoral researchers, and faculty; plus another 100 associated research, technical, and administrative staff members. Cahill features laboratory space for constructing and testing state-of-the art space- and ground-based astronomical instrumentation.

The architectural showcase piece is an impressive "stairway to the heavens" that is meant to evoke a telescopic view from just inside the main entry upward through the building and skyward. It is actually an elaborate beam structure that forms the core support framework of the building.

Caltech's new Cahill Center for Astronomy and Astrophysics has enabled a co-location and cohesion of personnel that will have a major positive impact on astrophysical research worldwide.
Let the discoveries begin!

Thanks, Lynne. We look forward to future updates from Lynne and her colleagues at the Cahill Center.

New video: Dark matter explained

Liz Kruesi — Mon, 24 Aug 2009 18:11:00 GMT

In my newest video, I give you an overview of dark matter, that mysterious stuff that makes up some 90 percent of the universe’s mass. During the last few decades, astronomers have gained convincing evidence that stars, gas, and dust aren’t all there is to the universe. Most of it is “dark” — both dark matter and dark energy. This video focuses on dark matter, and it’s the second video in a series called “Cosmology 101.”

Also check out the video about the Big Bang.

Editor’s note: “Cosmology 101: Dark Matter” is available to registered members of Astronomy.com. Registration is free, so sign up today to watch this video and enjoy other great benefits.

Send us your astronomy questions

Liz Kruesi — Wed, 15 Jul 2009 21:05:00 GMT

Perplexed by planets? Confused by cosmology? Baffled by black holes? Then send in your questions to Astronomy magazine at askastro@astronomy.com.

If you have an astronomy question about observing, the planets, stars, cosmology, or astronomy history, send it in! Five are selected each month for publication in the Ask Astro section of Astronomy magazine. If your question is selected, we will forward it to an expert for his or her response. Then, the question and answer will appear together in a future issue. We may edit or revise your question for clarity.

We aren’t always able to respond to questions individually. But please keep the questions coming — they help us to learn what our readers are interested in, and what topics we should consider for future coverage in the magazine.

New Video: The Big Bang explained

Liz Kruesi — Fri, 17 Apr 2009 14:29:00 GMT

In my newest video, I give you an overview of the Big Bang Theory (the cosmology theory, not the television show), and help clear up a few common misconceptions. Hopefully the crazy world of cosmology will make a bit more sense after you’ve watched the production.

This clip is the first in a series called Cosmology 101. Over the next few months, you’re invited to tune in to watch me discuss additional cosmology topics.

Watch the video, Cosmology 101: The Big Bang.

Relativity rap

Liz Kruesi — Mon, 08 Dec 2008 20:55:00 GMT

It’s great how some people communicate science ideas. A few months ago we heard about the science writer at the Large Hadron Collider who filmed a rap video about the LHC and posted it on YouTube.

So what does this have to do with Astronomy? Well, Rob Wheeldon, a reader and fellow astronomy enthusiast from the U.K., recently sent us a letter that included his own rap. This one, however, doesn’t concern the LHC, but instead a very complex subject: relativity. Wheeldon told me that his inspiration to write about relativity and Albert Einstein is because he, like Einstein, is dyslexic. I hope you enjoy his relativity rap as much as we did!

Relativity rap
There are fools who think they are clever
But check Einstein, he wrote the line
Relativity he found divine

Mass and energy is the same thing
E=mc squared is da bling

E equals energy, M equals mass
And the mc sparks the time to pass

The square root of two holds the whole thing together
And the workings of this process are both elegant and clever

The equation describes the speed of light’s accretion
And properties of mass to energy conversion

From the well of gravity springs space/time
The structure of which creates the world line

A prism’s curved light
gave Newton insight
Into the structure and laws of thermodynamics

The Sun is a changeable force with a moving boundary
which gives heat and light to you and me

Spectral light emissions are part of the effect
that curves space/time to a constant effect

With energy the world resounds
there's always motion where light is found

E and mc squared gets it together
and creates all kinds of cosmic weather

Photons and electrons perform the trick
that lets the clockwork universe tick
It is not clockwork

Newton's bucket is wrong
but try making that into a song

I understood Newtonian physics at school
for every action an opposite, I was no fool

Well, Dense energy equals mass
they didn't teach me that in class

Compressed energy is released in a dance
a physical activity not left to chance

All the sums must balance out
and that's what stars are all about

Nuclear fusion will cause no confusion
If you get over the simple delusion

That everything is in a fixed state
That's not how particles interrelate

A black hole it has no mass, progress and motion, towards its devotion
No light escapes this non-Euclidian potion

Into what dimension does the energy emerge
The whole darn thing is truly absurd

Now please don’t see this as a retraction
Let me illustrate this action

One, two, three, all states emerge, mass and light and energy
Extend from a singularity

Unleashed potential all around
and that was how the light was found

The Lambda principle lets there be light
Who’s to say it’s not cosmologically right?

A balanced creation of energy
that creates everything mysteriously

Electrons and photons like to dance
and will interact given half a chance

With its strange polarity that exists on every scale
The perfect geometry off this tale

The golden ratio that makes every thing go
It’s the strangest thing that we all know

To all of us it’s quite clear
the Earth’s a sphere

You can not see the curve of the Earth
for its mighty girth

The curve of the line resting on the equator
Is the truth of the now in the past and the later?

Now it all seems quite neat these marvels of science
The globe traveling in relative motion and geodesic compliance

But the point of an arrow that curves on a dime
This is the essence of circular time

Gravity curves nature to a constant degree
and even time is a singularity

Come on now, and don't be morons
just innovate your interneurons

The Wheeler-DeWitt equation freezes time, but is quantum gravity
the key to undoing this mystery?

The Tachyon may be faster than the speed of light
and into history it sets flight

I hope this rhyme found the time
to show you that physics is so sublime

Cosmologists issue challenge

Liz Kruesi — Wed, 29 Oct 2008 16:00:00 GMT

Are you good with statistics and interested in cosmology? Well, astronomers have issued a challenge to aid in the understanding of dark matter and dark energy — the mysterious stuff that makes up roughly 95 percent of our universe. Thirty-eight astronomers from 19 international institutions are issuing this challenge, called the GRavitational lEnsing Accuracy Testing 2008 (GREAT08).

Neither dark matter nor dark energy is directly visible — both seem to interact via gravity only. So, astronomers need to use detection methods that do not require directly observing. One of the most promising ways to detect, and analyze, dark matter and dark energy is with gravitational lensing. In this technique, astronomers study minute perturbations in the shapes of distant galaxies to map the universe's dark matter. Sarah Bridle of the University College London explains, “Streetlamps appear distorted by the glass in your bathroom window and you could use the distortions to learn about the varying thickness of the glass. In the same way, we can learn about the distribution of the dark matter by looking at the shapes of distant galaxies.” This dark matter distribution will in turn show the effect of dark energy on the universe’s growth structure.

Scientists must use precise image analysis to measure the perturbations in galaxy shapes through blurring, pixilation, noise and also theoretical uncertainty about the undistorted shapes of galaxies. Statistical tools needed to analyze the gravitational lensing images are not only related to astronomy, which is why the GREAT08 astronomers have issued the challenge.

Yes, astronomers have ways to analyze this type of data — these tools are adequate for current data. However, future dark energy surveys will require analysis techniques that are about 10 times more precise. Cosmologists will use methods developed for the GREAT08 challenge to analyze future dark energy survey data.

This challenge will take time. Those participants who are serious about the challenge are asked to work through 27 million galaxy images (in sets of 10,000) from 170 gigabytes of data. Including supplementary data, GREAT08 contains 200 gigabytes of simulated images with 30 million galaxy images.

If this is a challenge you think you’d be interested in, check out the GREAT08 handbook (PDF file). The competition deadline is April 30, 2009, and the results will be announced June 2009 at the latest. The GREAT08 challenge will award two winners, where the prize is a trip to the final workshop, to be held around June 2009.

Why I love cosmology

Liz Kruesi — Fri, 26 Sep 2008 15:18:00 GMT

Yesterday I spent a bit of time reading through the scientific paper regarding the flow of galaxy clusters pulled by possible dark matter beyond the universe’s horizon. I don’t know what it is about cosmology, but I find it fascinating. It’s weird stuff, completely crazy ideas, and very difficult to understand, but something about it just gets me. Maybe it’s the knowledge that we (well, scientists) are learning so much about our universe. Not just the small neighborhood around us, but the far reaches of the universe. (Maybe it’s the same reason I crave travel, not to other states in the Midwest, but international travel to Australia, India, Switzerland, and other faraway locales.)

Granted, quite a bit of cosmology is a whole lot of theory, but those ideas come out of observations. Some of those concepts are so weird, you just can’t make them up. I don’t know if I’d say it’s the abstraction of cosmology that I enjoy. I’m not really one for abstract ideas. For example, quantum mechanics was my most dreaded subject in school.

Maybe my interest in cosmology is related to the beauty in the universe (and the scientific process). Astronomers observe something and can find a place for it in the structure of science. Galaxy surveys and structure simulations all show an incredible organized natural beauty to our universe. Cosmology — and really all areas of astronomy — have a way of combining the analytical with art.

And a quick look at the cosmology discussion thread in our online forums, many of you are as intrigued in this topic as I am.

LHC gets hip

Karri Ferron — Thu, 11 Sep 2008 16:15:00 GMT

For those of you physics and cosmology enthusiasts who are into learning through alternative methods (or you’re just someone who likes some clever music and lyrics), you’ve got to check out the Large Hadron Rap video on YouTube. Of course, that’s if you aren’t one of the more than 1.5 million people who’ve viewed it already.

The nearly 5-minute scientific rap goes to the credit of Kate MacAlpine, a 23-year-old American trainee at CERN. She wrote lyrics explaining the goals of the Large Hadron Collider and how it works on her bus rides to and from work, before putting them to music and producing a music video around CERN’s headquarters along the Franco-Swiss border.

The video is funny, informative, and entertaining — a great way to learn about the particle accelerator that passed its first test September 10. MacAlpine says she wants to be a science writer, and from her work with this rap, I would say she has a promising future.

Read "Astronomy previews the Large Hadron Collider's big day" to learn more about what scientists hope to learn from the LHC.

John Archibald Wheeler (1911–2008)

Francis Reddy — Mon, 14 Apr 2008 21:27:00 GMT

Best known to astronomical trivia buffs as the man who coined the term “black hole,” University of Texas physicist John A. Wheeler died this morning at the age of 96.

Wheeler “was legendary for his way with words, coining such terms as wormholes, quantum foam, black holes, and the wave function of the universe,” writes Wheeler’s former student and current University of Chicago physicist Daniel Holz over at Cosmic Variance. Wheeler’s scientific resume extended from quantum mechanics — he collaborated with Niels Bohr on early nuclear fission research — to cosmology, but he’s best known for his contributions to general relativity.

“For the first half-century of its life, general relativity was a theorist’s paradise, but an experimentalist’s hell. No theory was thought more beautiful, and none was more difficult to test.” That summary comes from the 1973 edition of Gravitation, the bible of relativity, written by Charles W. Misner and Kip S. Thorne — two former students of Wheeler’s — and, of course, the man himself.

The chapter concludes that relativity “has emerged from each of its tests unscathed — a remarkable 1973 tribute to the 1915 genius of Albert Einstein.” It’s a remarkable 2008 tribute as well, for relativity still reigns supreme.

Following the implications of relativity’s equations led physicists to ponder black holes. In 1939, J. Robert Oppenheimer and Hartland Snyder at the University of California, Berkeley, used them to show that when a big enough star runs out of fuel, it must collapse to densities so great even light cannot escape it. Moreover, the collapse continues forever.

At first, Wheeler fought the notion that a collapsing mass could cut itself off from communication with the rest of the universe. But, by the mid-1960s, intense theoretical work showed there was no way of avoiding these so-called “frozen stars.” In 1967, Wheeler hit on a more dramatic — yet scientifically justified — term: black hole.

By then, astronomers had already identified a candidate — now considered a confirmed — black hole. The object, named Cygnus X-1, is one of the brightest X-ray sources in the sky. The radiation arises as gas stolen from a blue supergiant streams onto a disk of matter gathered around a stellar-mass black hole. A few dozen such systems are known.

These are small-fry compared to their supermassive brethren at the cores of galaxies. The black hole at the Milky Way’s center weighs in at 3 to 4 million Suns.

But back to Wheeler. Those interested in hearing these developments in the physicist's own voice should consult his science autobigraphy, Geons, Black Holes, and Quantum Foam: A Life in Physics, written with Kenneth W. Ford (W. W. Norton & Co., 2000).

Light, mirrors, gravity!

Francis Reddy — Mon, 10 Mar 2008 21:40:00 GMT

Yesterday’s Milwaukee Journal Sentinel ran a nice summary of efforts by the University of Wisconsin - Milwaukee to detect gravitational waves. The article focuses on NEMO, the $1.8 million, 1,560 CPU, Beowulf-class computing cluster built and operated by the school’s gravitational-wave group. (Ah, I love that kind of talk.)

NEMO was commissioned in 2006. Since then, it’s been chugging through data produced by the Laser Interferometer Gravitational Wave Observatories (LIGO) in Hanford, Washington, and Livingston, Louisiana. Here’s an informative cartoon of the setup.

These facilities bounce lasers back and forth to track length changes smaller than the diameter of a hydrogen atom. Such changes would occur when gravitational waves pass by and ripple through our local space-time. Relativity predicts such things, but so far, no one has detected them.

Scientists continually are improving the reach and sensitivity of these observatories. Sooner or later, they’ll detect signals from things like inspiraling pairs of neutron stars or black holes, core-collapse supernovae, and possibly even gravitational waves from the Big Bang.

You can participate, too. Since early 2005, LIGO data has been distributed to personal computers and processed using the Einstein@Home project’s nifty screensaver. This gives users eye candy in return for background use of their computers (more about it here).

Einstein@Home lets users “compete” as teams. I formed Team Astronomy as soon as the project went public. We now boast 69 members with computing credits, which are points awarded based on the amount and speed of data processing by each computer.

Team Astronomy now ranks in the top 45 in terms of recent average credits, but I think we can do better. Feel free to join us in search of gravitational waves. It may be the closest you’ll get to a Nobel prize.