Wednesday, October 20, 2010

Hot and bothered, take two.

Last week, I was fortunate enough to interview Professor Mike Shull at the University of Colorado about his recent publication. Although I've reviewed this research before, I thought some revisions were necessary. For more in-depth info about the project, you can check out the transcript of our chat here.

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Imagine our universe - but smaller, hotter, brighter, and more dense. What you are picturing is the cosmos when it was a mere 2 billion years old. A team of astronomers from the University of Colorado at Boulder has devoted years to studying this epoch in an effort to understand a phenomenon that has recently been christened "universal warming." This period of reheating stalled the formation of dwarf galaxies in the early universe and tore tightly-bound electrons from the helium atoms that had been cooked up during the big bang. How does such dramatic warming happen? Professor J. Michael Shull and his team of observers believe they may have the answer.

As it turns out, the epoch of reheating coincides with a time in the past when extremely powerful, outrageously luminous balls of ultraviolet radiation called quasars ruled the universe. "A quasar, or a quasi-stellar object, is a generic active galactic nucleus,” explains Shull. "Something in the center of a galaxy goes haywire." Quasars emit a huge amount of energy, and his team believes this energy is responsible for the 500 million-year period of aggressive warming that halted the growth of small, low-mass galaxies nearly 12 billion years ago.

The team's work centers on a piece of equipment on the Hubble Space Telescope called the Cosmic Origins Spectrograph, or COS. Astronomers use COS to learn about very distant, very energetic objects by analyzing the way their light is absorbed by electrons in the intervening gas. Shull's team used COS to observe incoming light from a quasar as it passed through distant helium gas, and found that there was no absorption of light between 11.7 billion and 11.2 billion lightyears away. "When the absorption goes away, we’re assuming that it’s because now, helium is fully ionized," said Shull. "Once it’s a bare helium nucleus with no electrons, there’s no absorption." Thanks to the blistering energy of quasars, helium was reionized and star-forming gas heated to escape velocity, preventing the growth of dwarf galaxies.

This isn't a new project for the group at Boulder. Students and faculty in the Department of Astrophysical and Planetary Sciences have been working on this research since 1994, and they hope to continue their investigation for many years to come. In the coming months, Shull and his team plan to repeat their observations using a few different sightlines in order to determine whether reheating occurred at the same time in other regions of the universe. The team's research was published in the October 20 issue of The Astrophysical Journal.

Sunday, October 10, 2010

Scientia Pro Publica 42: The Ultimate Answer to the Ultimate Question of Life, The Universe, and Everything.



That's right! I am proud to present to you this particular edition of Scientia Pro Publica, your ULTIMATE guide to the best science, nature and medical writing on the web... the best, that is, until next week.

Let’s get started with the obvious: we all think science is pretty cool, or we wouldn’t be here. Self-proclaimed science lover Julie links us to some great resources to celebrate our collective appreciation of nature (and rockets!) in her posts World Space Week! and A New Website for Rocket Lovers over at Mama Joules. For some more fun, check out Sailing by Starlight: The Lost Art of Celestial Navigation at Southern Fried Science. There, Andrew teaches us all a lesson about living without navigational equipment. That's right. No Google maps, no GPS, no atlas or street names or landmarks; just you, the sea, and the sky.

Thursday, October 7, 2010

Scientia Pro Publica is coming to cosmodynamics!

Hello faithful cosmodynamicists! I am proud to announce that I will be hosting the upcoming edition of Scientia Pro Publica, the biweekly carnival of the best science, nature and medical writing the blogosphere has to offer.

That being said, I'm looking for your submissions! The issue will be published on Monday, October 11th, so you only have a few days left to submit. If you have an interest in science and writing and would like to share your original work with a larger audience, now is your chance! You can either use this handy submission form, or you can send your articles to ScientiaBlogCarnival@gmail.com. The best quality pieces will appear in the 42nd edition of Scientia, here, on Monday.

Happy writing, and make sure to check back after the weekend!

Early universe hot and bothered, says new research.

Imagine a place so hot and so high in energy that there is no such thing as a neutral atom. Instead, electrons are blasted away from their nuclei by radiation so intense that the most abundant elements can exist only as positively-charged ions. In many low-mass systems, thermal pressure outweighs the influence of gravity and galaxies can neither grow nor hold onto their stores of gas. The small "stuff" in the universe becomes inert, and stays that way for hundreds of millions of years.

According to new research released by a team working with data from the Hubble Space Telescope's Cosmic Origins Spectrograph, this is exactly what happened to our universe over 11 billion years ago. The astronomers, working out of the University of Colorado at Boulder, claim that two billion years after the big bang, conditions suddenly changed and the entire universe overheated. That seems... drastic. How does something like that just happen, and on such an enormous scale?


Image courtesy of NASA, ESA, and STScI.
Click to enlarge.

You may recall from a previous post or two that quasars are extremely distant, outrageously luminous balls of radiation that were born of cataclysmic galaxy collisions in the early universe. They can emit all sorts of radiation, from radio waves to visible light to x-rays. When photons given off by a quasar interact with intensely hot material falling into a central supermassive black hole, they become energized and propagate as x-rays across the expanding universe. Of course, objects this powerful didn't form right after the big bang. It took a good couple of hundred million years for the first stars to form, and then a few hundred million for those stars to condense into galaxies, and then a few hundred million more for those galaxies to become abundant enough to encroach on each others' space, collide, and create the supermassive black holes responsible for the x-ray output of quasars. Once all of this happened, however, it wasn't long before the universe was filled with x-rays and all of its intergalactic gas heated accordingly.


Gas in the interstellar medium is excited by photons at all energies.
Image courtesy of NASA/JPL-Caltech.

You might be wondering how in the world astronomers can know all of this, given that it all occurred over 7 billion years before our solar system even existed. As it so happens, astronomers can use the blazing brilliance of quasar light to study the gas and dust between us and them. When an energetic photon interacts with an atom, it can transfer some of its energy to one of the atom's electrons, causing the electron to temporarily "jump" to a higher energy state. The energy transferred to the electron will always be a discrete amount, and corresponds to a particular wavelength of light (e.g., radio, visible, x-ray). When astronomers study the spectrum of a sample of gas that lies between a photon source (such as a quasar) and a detector (such as a telescope), any absorbed photons will show up as specific lines in the spectrum. Each line, or transition, corresponds to a particular energy and a particular atom, so scientists can automatically tell what type of atom was energized, how much it was energized, and whether enough energy was present to ionize the atom.


The electromagnetic spectrum. Image courtesy of OSHA.

In this case, the CU-Boulder team spotted a hallmark transition of helium in the gas present between 11.3 and 11.7 billion lightyears away. Knowing how much energy is needed to ionize helium, the researchers were able to extrapolate the harsh and stagnant circumstances our early universe may have faced at that time.

Mapping the conditions of the toddler universe: just one more way Hubble gotchu!


Milky J, Hubble aficionado, seen here with an image of the Eagle nebula, M16, courtesy of the Hubble Space Telescope.

Friday, October 1, 2010

Earth-like planet discovered, may support life.

Big news: Astronomers have discovered another planet that could support life as we know it. Over the last few years, the number of planets found to orbit nearby stars has increased exponentially. Finding planets is no great shakes anymore. But coming across one that falls within the so-called "Goldilocks zone" of a star (not too hot, not too cold, etc.. get it?) is something entirely different.


Artist rendering of an Earth-like planet in the Gliese system.
Image courtesy of ESO.


The new planet goes by the romantic name Gliese 581g and is part of a system of six known planets orbiting the same red dwarf star about 20 lightyears away from Earth. Two of these planets, 581c and 581d, orbit on either side of 581g - on the warmer and cooler edges, respectively, of the habitable zone (HZ). Meanwhile, planet g lies smack dab in the middle of the HZ, with a presumed equilibrium surface temperature of around 228 K (-45 C). That's pretty cold. Keep in mind, however, that the equilibrium temperature of the Earth is actually about 255 K (-18 C). We can thank Earth's atmosphere and the resulting greenhouse effect for keeping our planet nice and toasty. The same goes for Gliese 581g. A greenhouse effect would support liquid water, one of the cosmic benchmarks for potential development of life. There is an important difference, however: planet g is tidally locked to its star, much like the way our moon is tidally locked to the Earth. This means that one side of the planet always faces its star, while the opposite side always faces away. According to Steven Vogt, an astronomer from the UC - Santa Cruz team, a temperate and liveable climate would probably only exist at the boundary between the blazing hot sunny side and the frigid, perpetually dark side. This might be a card in life's favor, however. To quote Vogt, "Any emerging life forms would have a wide range of stable climates to choose from and to evolve around, depending on their longitude."


Habitable zone of the Gliese system as compared with that of our solar system. Gliese 581g has been discovered in the HZ between planets c and d.
Image courtesy of ESO.


Altogether, there are many factors that distinguish Earth from planetary newcomer Gliese 581g. For instance, the planet is at least three times as massive as Earth, and thus orbits its parent star far closer than we do the sun. Its surface gravity is likely stronger than ours, and it may not necessarily have the same rocky composition or protective atmosphere as we do. But it's a start, and it is certainly conceivable that life could have developed there. Unfortunately, since planet g never transits its star relative to our line of sight on Earth, researchers currently do not have the technology necessary to analyze its composition or exact mass. That being said, the discovery of planet g is the first of its kind, and it gives astronomers and astrobiologists hope of finding many more planets like it. As Vogt put it, "If these are rare, we shouldn't have found one so quickly and so nearby. The number of systems with potentially habitable planets is probably on the order of 10 or 20 percent, and when you multiply that by the hundreds of billions of stars in the Milky Way, that's a large number. There could be tens of billions of these systems in our galaxy." His brazen comments are currently catching a lot of flack on the airwaves, but in theory, he's right. We'd be silly not to acknowledge the likelihood of life elsewhere in the universe, and this discovery is as good a start as any.