NASA's Hubble Confirms That Galaxies Are the Ultimate Recyclers

New observations by NASA's Hubble Space Telescope are expanding astronomers' understanding of the ways in which galaxies continuously recycle immense volumes of hydrogen gas and heavy elements. This process allows galaxies to build successive generations of stars stretching over billions of years.

This ongoing recycling keeps some galaxies from emptying their "fuel tanks" and stretches their star-forming epoch to over 10 billion years. 

Distant quasars shine through the gas-rich "fog" of hot plasma encircling galaxies. At ultraviolet wavelengths, Hubble's Cosmic Origins Spectrograph (COS) is sensitive to absorption from many ionized heavy elements, such as nitrogen, oxygen, and neon. COS's high sensitivity allows many galaxies that happen to lie in front of the much more distant quasars. The ionized heavy elements serve as proxies for estimating how much mass is in a galaxy's halo. (Credit: NASA; ESA; A. Feild, STScI)
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This conclusion is based on a series of Hubble Space Telescope observations that flexed the special capabilities of its Cosmic Origins Spectrograph (COS) to detect gas in the halo of our Milky Way and more than 40 other galaxies. Data from large ground-based telescopes in Hawaii, Arizona and Chile also contributed to the studies by measuring the properties of the galaxies.

Astronomers believe that the color and shape of a galaxy is largely controlled by gas flowing through an extended halo around it. The three studies investigated different aspects of the gas-recycling phenomenon.

The results are being published in three papers in the November 18 issue of Science magazine. The leaders of the three studies are Nicolas Lehner of the University of Notre Dame in South Bend, Ind.; Jason Tumlinson of the Space Telescope Science Institute in Baltimore, Md.; and Todd Tripp of the University of Massachusetts at Amherst.

The COS observations of distant stars demonstrate that a large mass of clouds is falling through the giant halo of our Milky Way, fueling its ongoing star formation. These clouds of hot hydrogen reside within 20,000 light-years of the Milky Way disk and contain enough material to make 100 million suns. Some of this gas is recycled material that is continually being replenished by star formation and the explosive energy of novae and supernovae, which kicks chemically enriched gas back into the halo. 

The COS observations also show halos of hot gas surrounding vigorous star-forming galaxies. These halos, rich in heavy elements, extend as much as 450,000 light-years beyond the visible portions of their galactic disks. The amount of heavy-element mass discovered far outside a galaxy came as a surprise. COS measured 10 million solar masses of oxygen in a galaxy's halo, which corresponds to about one billion solar masses of gas -- as much as in the entire space between stars in a galaxy’s disk.

Researchers also found that this gas is nearly absent from galaxies that have stopped forming stars. In these galaxies, the “recycling” process ignites a rapid firestorm of star birth which can blow away the remaining fuel, essentially turning off further star-birth activity. 

This is evidence that gas pushed out of a galaxy, rather than pulled in from intergalactic space, determine a galaxy's fate."

The color and shape of a galaxy is largely controlled by gas flowing through an extended halo around it. All modern simulations of galaxy formation find that they cannot explain the observed properties of galaxies without modeling the complex accretion and "feedback" processes by which galaxies acquire gas and then later expel it after chemical processing by stars. Hubble spectroscopic observations show that galaxies like our Milky Way recycle gas while galaxies undergoing a rapid starburst of activity will lose gas into intergalactic space and become "red and dead." (Credit: NASA; ESA; A. Feild, STScI)
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The Hubble observations demonstrate that those galaxies forming stars at a very rapid rate, perhaps a hundred solar masses per year, can drive two-million-degree gas very far out into intergalactic space at speeds of up to two million miles per hour. That's fast enough for the gas to escape forever and never refuel the parent galaxy.

While hot gas "winds" from galaxies have been known for some time, the new COS observations reveal that hot outflows extend to much greater distances than previously thought and can carry a tremendous amount of mass out of a galaxy. Some of the hot gas is moving more slowly and could eventually be recycled. The observations show how gas-rich star-forming spiral galaxies can evolve to elliptical galaxies that no longer have star formation.

The light emitted by this hot plasma is invisible, so the researchers used COS to detect the presence of the gas by the way it absorbs certain colors of light from background quasars. Quasars are the brightest objects in the universe and are the brilliant cores of active galaxies that contain active central black holes. The quasars serve as distant lighthouse beacons that shine through the gas-rich "fog" of hot plasma encircling galaxies. At ultraviolet wavelengths, COS is sensitive to the presence of heavy elements, such as nitrogen, oxygen, and neon. COS's high sensitivity allows many galaxies to be studied that happen to lie in front of the much more distant quasars. The ionized heavy elements are markers for estimating how much mass is in a galaxy's halo.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency.NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

NEW SCIENCE/ARTS AFFINITY

In February of this year, I had the distinct pleasure of being invited to the STUDIO for Creative Inquiry, a zygote of an institution nestled between departments at Carnegie Mellon University, to work on a strange collaborative project called a "booksprint." A booksprint, I discovered, is a fairly new practice, derived from the world of open-source software "codesprints." In this version, a group of writers work exhaustively for a week on a shared project, which is then made into a book at the conclusion of their session. In seven days, our group of sprinters turned an idea—"let's write a book about the intersection between art, science, and technology!" —into a 190-page, full-color, nattily-designed compendium of the current moment in art/science affinities.

The book in its developmental stages.

We wrote collaboratively in shared, networked documents, ensuring that the finished book would have no single author. Of course, we all have our specialities:Régine Debatty the international new media blogger was our encyclopedia of projects, Andrea Grover the project leader our thesis synthesizer, Pablo Garcia the image-hounding art history scholar, and, well, you can see my pawprints all over the sections on science fiction, utopian architecture, and visionary philosophy.

We worked passionately, discussed endlessly, enlisted the research assistance of dozens of interns, and the finished project emerged (relatively) without incident. I still can't believe that a group of erstwhile strangers could so swiftly and seamlessly brainstorm, structure, research, and design something of such substance from nothing.

That said, it's been many months since we left Pittsburgh to return to the hectic pace of our normal lives. What was created in a week has taken nearly a year to fine-tune, but I'm immensely proud to announce that we're finally finished. Behold,NA/SA: New Art/Science Affinities, a book about the intersection between art, science, and technology.

The book includes meditations, interviews, diagrams, letters and manifestos on maker culture, hacking, artist research, distributed creativity, and technological and speculative design. Sixty international artists and art collaboratives are featured, including Agnes Meyer-Brandis, Atelier Van Lieshout, Brandon Ballengée, Free Art and Technology (F.A.T.), Rafael Lozano-Hemmer, The Institute for Figuring, Aaron Koblin, Machine Project, Openframeworks, C.E.B. Reas, Philip Ross, Tomás Saraceno, SymbioticA, Jer Thorp, and Marius Watz.

NA/SA was designed as it was written by Jessica Young and Luke Bulman of Thumb Projects. Immeasurable credit is due to them for organizing the endless flow of text into readable, beautiful documents at the end of each workday. Doubtless we would've had an arduous time marshaling our ideas had Thumb not been involved from the get-go.

More about the book and its process at Carnegie Mellon University's Miller Gallery website. New Art/Science Affinities can be bought printed on demand at Lulu.com, or you can download a free, full-text PDF of the book right here. I encourage you to browse, study, and print the free PDF, but the tactile book is a joy to hold.

Posted by Claire L. Evans at 2:09 PM • 0 Comments

SEPTEMBER 13, 2011

UNIVERSE Q&A: FRANK WHITE

Category: Earth • Human • Interview • Planets • Politics • Space • Systems

A couple of months ago, I wrote a piece here on Universe exploring the ideas of the futurist Gerard K. O'Neill, who designed far-out but ultimately quite pragmatic environments for human habitation in space in the mid-1970s. In that article, I touched briefly on the notion of the "Overview Effect," a phrase coined by the writer Frank White to describe the profound insight -- characterized by a sudden awareness of life's interconnectedness and the frailty of our planet -- experienced by astronauts gazing down at the Earth from space.

Frank White is the author of The Overview Effect: Space Exploration and Human Evolution, a book that has completely changed the way I think about our planet and its position within the larger systems of the Universe. The book is an amalgam of space history, environmentalist philosophy, and starry-eyed futurism; it weaves White's observations about the nature of systems, the future of space travel, global communications, and cosmic spirituality with interviews with dozens of astronauts from all over the world. In short, it should be mandatory reading for all passengers aboard the Spaceship Earth.

Frank White was gracious enough to lend his time and considerable mind to a battery of questions from Universe, the full transcript of which is below. It's long, but I promise it will blow your mind.

[I'm greatly indebted to Jonathan Minard, of deepspeed media and the STUDIO for Creative Inquiry at Carnegie Mellon University, for his help in brainstorming many of these questions.]

Part One: The End of the Space Age

Universe: Following the retirement of the shuttle program this summer, some have labeled this the "end of the space age." Others argue that it's simply the age of human exploration that's over, and that robots are the path forward. How do you respond to these assessments?

Frank White: I would suggest that both assessments are incorrect. Space exploration is a global enterprise with increasing private involvement, and the end of one program for one national space agency is neither the end of the "space age," nor of human exploration.

Media reports have linked the shuttle program with space exploration in a way that obscures some of the more positive aspects of the new US space policy. For example, it encourages more private investment in space at a time when more private companies, like Virgin Galactic, are making those commitments. It also encourages more international cooperation, extends the life of the International Space Station, and sets our sights on Mars, which many space advocates consider the most logical next objective for human exploration.

The dichotomy between human and robotic exploration is also unnecessary. The two complement one another, especially if we want to not only explore but also begin to create human communities off the Earth. It is not an either/or choice.

Universe: The establishment of permanent habitation in space is no longer a question of technical feasibility, but political and social will. There are those who believe humans must explore space to avoid extinction and those who deem it foolish to waste resources on projects distracting us from our responsibilities at home. How do you see the two sides of the argument for and against space settlement? 

The key to the question is, "What do we consider our home?"

Frank White: I understand the two sides of the argument, but I consider human evolution to be the imperative behind our expansion into the universe, and I think it will continue. By this, I mean evolution in terms of politics, sociology, economics, and other aspects of human society, not just biology. The key to the question is, "What do we consider our home?" If it is the solar system and beyond, then space settlement is not a distraction. And even if our home is the Earth alone, there are many elements of space exploration and settlement that have already been beneficial to the Earth. For example, most people would agree that the Overview Effect triggered or at least enhanced the environmental impulse. This has proven to be beneficial to the Earth in ways that would have been difficult to predict in advance. The same can be said of how the Overview Effect has influenced our views on war and peace, also to the benefit of the people on Earth.

I find it somewhat puzzling that when we talk about problems on Earth, such as the so-called "population problem," we never include the dimension of our larger environment, i.e., the solar system and beyond. And when we talk about the "energy problem," only a few people are willing to even consider the promise of satellites that could beam solar energy to the Earth. We discuss almost every major human problem as if we were confined to one planet, rather than being on "Spaceship Earth," which is a part of the solar system, galaxy, and universe.

Universe: Are the goals of caring for the biosphere on the one hand, and on the other of establishing artificial ecospheres in space, necessarily mutually exclusive?

Frank White: No...this is a choice as well. In my book, I talk about the Human Space Program as a "central project" for all of humanity. It involves establishing a planetary civilization with a high priority on protecting the biosphere as well as a commitment to exploring the universe as a global (rather than national) enterprise. The Human Space Program could become a unifying force for humanity as we expand beyond Earth. We can create any future that we choose to create as a species. Caring for the biosphere can be in conflict with creating new ecospheres, or the two goals can be in harmony with one another.

How to understand big bang theory??

Big Bang model

Main articles: Big Bang, Timeline of the Big Bang, Nucleosynthesis, and Lambda-CDM model

The prevailing Big Bang model accounts for many of the experimental observations described above, such as the correlation of distance andredshift of galaxies, the universal ratio of hydrogen:helium atoms, and the ubiquitous, isotropic microwave radiation background. As noted above, the redshift arises from the metric expansion of space; as the space itself expands, the wavelength of a photon traveling through space likewise increases, decreasing its energy. The longer a photon has been traveling, the more expansion it has undergone; hence, older photons from more distant galaxies are the most red-shifted. Determining the correlation between distance and redshift is an important problem in experimental physical cosmology.

Chief nuclear reactions responsible for the relative abundances of light atomic nuclei observed throughout the universe.

Other experimental observations can be explained by combining the overall expansion of space with nuclear and atomic physics. As the universe expands, the energy density of the electromagnetic radiation decreases more quickly than does that of matter, since the energy of a photon decreases with its wavelength. Thus, although the energy density of the universe is now dominated by matter, it was once dominated by radiation; poetically speaking, all was light. As the universe expanded, its energy density decreased and it became cooler; as it did so, the elementary particles of matter could associate stably into ever larger combinations. Thus, in the early part of the matter-dominated era, stable protons andneutrons formed, which then associated into atomic nuclei. At this stage, the matter in the universe was mainly a hot, dense plasma of negative electrons, neutral neutrinos and positive nuclei. Nuclear reactions among the nuclei led to the present abundances of the lighter nuclei, particularly hydrogen, deuterium, and helium. Eventually, the electrons and nuclei combined to form stable atoms, which are transparent to most wavelengths of radiation; at this point, the radiation decoupled from the matter, forming the ubiquitous, isotropic background of microwave radiation observed today.

Other observations are not answered definitively by known physics. According to the prevailing theory, a slight imbalance of matter overantimatter was present in the universe's creation, or developed very shortly thereafter, possibly due to the CP violation that has been observed by particle physicists. Although the matter and antimatter mostly annihilated one another, producing photons, a small residue of matter survived, giving the present matter-dominated universe. Several lines of evidence also suggest that a rapid cosmic inflation of the universe occurred very early in its history (roughly 10⁻³⁵ seconds after its creation). Recent observations also suggest that the cosmological constant(Λ) is not zero and that the net mass-energy content of the universe is dominated by a dark energy and dark matter that have not been characterized scientifically. They differ in their gravitational effects. Dark matter gravitates as ordinary matter does, and thus slows the expansion of the universe; by contrast, dark energy serves to accelerate the universe's expansion.