Astronomy news round-up

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Crab is emitting super-energetic gamma rays

Here’s another chapter for the books of “Persistence Pays Off” and “Who Woulda Thought?” A team of astronomers has discovered very energetic gamma-ray pulses emanating from the core of the Crab Nebula, in defiance of current theory. The nebula, a remnant of a 1,000 year-old supernova, is a semi-chaotic mass of gas surrounding a type of neutron star called a pulsar, the source of the gamma rays. Like all neutron stars, a pulsar is the tiny, extremely dense, collapsed core of a progenitor star; what makes these objects special is that the axis of rotation is offset from the bright magnetic poles, so that every time they spin they are observed to emit a pulse, like a lighthouse. Given its relative young age and close proximity to Earth — a mere 6,500 light-years — the Crab pulsar has been well-studied by astronomers. Theorists thought it was not possible for a pulsar to emit such energetic gamma-ray pulses, leading some of their colleagues to tell members of the team they were “crazy” for even trying to observe them. But the astronomers’ persistence paid off, and the new discovery is already changing how theorists think about these objects.

“We thought we understood the gamma-ray emission, and this was really becoming a foundational feature of our models, but that’s now thrown out,” [one of the authors of the study, Andrew] McCann explained. “The reason why this is so exciting is that it’s turning things around in the field.”

You gotta love how astronomers and physicists get excited every time a new discovery shoots down current theory. That’s exactly the kind of attitude that moves science forward.

Uranus pummeled by other planets?

The distant gaseous planet has long been a puzzle to astronomers, who have been trying to explain its peculiar axis tilt ever since it was discovered.

Most of the planets in the solar system exhibit axis tilt — this is where the axis of a planet’s rotation is at an angle to an imaginary line that runs perpendicular to the planet’s orbital plane. Mercury is alone in that it has virtually zero axis tilt, though Jupiter’s is also diminutive at just 3 degrees. The Earth’s axis tilt is 23.5 degrees, and Venus is nearly upside down with its rotation axis pointing almost completely downward (this is also somewhat of a mystery to astronomers).

Uranus is the strangest of all, as it rotates flopped over on its side. Some astronomers have hypothesized that Uranus was pummeled by another planet in the early history of the solar system, and this collision resulted in Uranus’ 98-degree axis tilt. However, another collision might be required to explain the spin of Uranus’ moons, which should otherwise spin backwards. A new simulation created by astronomers indicates that collisions with two Earth-sized planets could explain Uranus’ observed configuration. The main problem with this idea, however, is to explain where the two Earth-sized planets came from.

Evidence for water on Mars?

Astronomers have discovered seasonal dark streaks on the surface of Mars that could be signs of melted water running across the surface. Meanwhile, NASA’s Curiosity rover is slated to visit Mars next year to look for signs of water in the Gale crater. The discovery of liquid water on Mars will greatly facilitate any plans to establish future colonies there.

Nobel news

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Physics

Three American scientists have been awarded the Nobel Prize in physics for their discovery that the universe is expanding at an accelerating rate. Saul Perlmutter will share the prize with Brian Schmidt and Adam Riess.

The discovery of the accelerating expansion of the universe followed an unexpected observational discovery in 1998. Astronomers in two different groups — the Supernova Cosmology Project (Perlmutter) and the High-z Supernova Search Team (Schmidt and Riess) — were observing the characteristic light signature of a certain type of supernova, called a Type 1a supernova, to probe the expansion history of the universe.

Let’s pause the story for a moment to explore the significance of these objects. Type 1a supernovae are a special subclass of exploding stars. Other types of supernovae occur when a massive star runs out of fuel, causing the core to collapse; their intrinsic brightness depends on a variety of factors, including the mass of the progenitor star. Type 1a supernovae occur when a white dwarf — the exposed core of a dead less-massive star — reaches a mass limit, called the Chandrasekhar limit. The mass limit can be reached if a white dwarf siphons matter from a companion star (see the header image above) or if two white dwarfs in a binary system collide. Since the resulting explosion always occurs at roughly the same mass, these supernovae always have roughly the same intrinsic brightness. This predictable brightness makes Type 1a supernovae excellent probes of distance and cosmic history.

Back to our story. The astronomers were using Type 1a supernovae to test the idea that the universe was slowing down in its expansion. If their idea was right, then the supernovae would appear to be brighter than expected, meaning they would be closer to the Earth than they would be if the universe had been expanding at a uniform rate. But they found the opposite: the supernovae appeared significantly dimmer than expected, meaning these exploding stars were further away than they would be for a uniform expansion. The astronomers concluded that the expansion of the universe was not slowing down, but rather speeding up. This conclusion was further supported by discoveries from other cosmological experiments, including mapping of the cosmic microwave background.

These discoveries led to the hypothesis that a mysterious force, called dark energy, is driving the accelerated expansion. Very little is currently known about this force, but several experiments, including HETDEX, Destiny, and SNAP, are underway to hopefully shed some light (as it were) on the subject.

Chemistry

Israeli scientist, Dan Schechtman, has been awarded the Nobel Prize in chemistry for his discovery of quasicrystals. What makes this award particularly interesting is the degree to which Schechtman persisted to make his discovery known. He worked for years in the face of skepticism and ridicule — two-time Nobel laureate, Linus Pauling, evidently referred to Schechtman as a “quasi-scientist” — before he managed to convince the scientific community that his observations overturned the prevailing model for how atoms and molecules can be arranged in solids.

A crystal is a type of material in which the arrangement of atoms is ordered and periodic. Scientists have probed crystalline structures using electron diffraction experiments in which beams of electrons are passed through crystal layers, producing an interference pattern. When Schechtman performed similar experiments on a different type of material, he found a peculiar interference pattern that seemed to defy the known laws of nature, since it indicated an ordered but non-periodic pattern in the arrangement of atoms. This is similar to the mosaic tile patterns found in medieval Islamic shrines.

Since Schechtman’s discovery, many quasicrystals have been synthesized and studied, and a naturally-occurring quasicrystal was discovered in Russia in 2009. Quasicrystals possess some useful properties, including a non-stick surface, low heat conduction, and hardness, that make them useful material for many products, from frying pans to surgical instruments.

In spite of his vindication and receiving the highest of accolades, Schechtman remains endearingly modest:

“The main lesson that I have learned over time is that a good scientist is a humble and listening scientist and not one that is sure 100 percent in what he read in the textbooks.”

Just as it’s difficult to be a devoted Christian in the face of skepticism, mockery, and exclusion, it’s difficult to be a devoted scientist under such conditions, as well. Schechtman deserves his award all the more for his determination and perseverance.

ALMA opens her eyes

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This wow-inducing image was just released by astronomers at the Atacama Large Millimeter/Submillimeter Array, or ALMA, which has finally opened its eyes to the stunning long-wavelength sky. The image, a combination of submillimeter ALMA imaging and optical imaging from the Hubble Space Telescope, shows the stunning Antennae Galaxies — two spiral galaxies in the process of colliding.

The “millimeter/submillimeter” refers to the range of wavelengths of light to which the ALMA instruments are sensitive. Millimeter and submillimeter wavelengths are much longer than the optical wavelengths our eyes detect, and thus can’t be seen by our eyes; but they can be “seen” by ALMA’s instruments, and translated into understandable data, like the image above. Astronomers are keen to observe the sky at these wavelengths, because some important astronomical processes produce light only at these wavelengths, including the births of stars and planets and the fiery birth of our universe.

ALMA is situated at an altitude of more than 16,000 feet on the Chajnantor plain in Chile’s Atacama Desert, the driest desert in the world. This may seem like a strangely inconvenient location for an observatory, but for observational astronomy you want high and dry. This reduces attenuation (dimming) of astronomical light and absorption by molecules in Earth’s atmosphere — mainly CO2, oxygen, and water.

ALMA is currently only partially operational, and not due to be complete until 2013. Once complete, it will have at least 66 radio antennae. Long-wavelength astronomy (this includes radio wavelengths) frequently makes use of arrays, because this is a relatively easy and cost-effective way to simulate a single gigantic antenna. These antennae, or radio dishes, are arranged in a configuration that can be moved in and out to create baselines of different length, essentially allowing the simulated gigantic antenna to change its size.

When the baseline of the array is small (~160 m), this allows greater sensitivity for extended sources, such as the Antennae Galaxies shown above. When the baseline is large (16 km), it produces exquisitely fine detail. The length of an array’s baseline typically cycles over a period of several months, as it’s quite a job to move the telescopes in and out.

If any of this seems familiar, it may be that you’ve seen a similar facility in the movie Contact. Some of the movie’s scenes were filmed in the fall of 1996 at the Very Large Array (VLA; soon to be the Extended Very Large Array) near Socorro, New Mexico. The VLA is a sibling of ALMA, whose parent organization is the Virginia-based National Radio Astronomy Observatory.

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Travel the Earth in 60 seconds

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Science teacher James Drake assembled this time-lapse video from a series of hundreds of photographs taken by astronauts aboard the International Space Station. See if you can identify geographical features (a full listing is in the YouTube description). Note the yellow line of Earth’s ionosphere and the flashes of lightning.

Physicists apparently break the speed of light

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The big news coming out of CERN is that scientists there have apparently exceeded the speed of light. The experiment, carried out repeatedly over a period of three years, involved the acceleration of neutrinos — tiny, neutrally-charged particles — over a distance of nearly 500 miles and timing their travel. Surprisingly, the neutrinos arrived 60 billionths of a second faster than light would have. It may sound like a miniscule difference, but considering that light travels over 186,000 miles per second, it’s actually quite significant.

If confirmed, the discovery would undermine Albert Einstein’s 1905 theory of special relativity, which says that the speed of light is a “cosmic constant” and that nothing in the universe can travel faster.

To be specific, Einstein’s theory says that particles with mass can be accelerated to speeds arbitrarily close to the speed of light in a vacuum — say, 99.9999999999% of the speed of light — but never at the speed of light in a vacuum, and certainly not exceeding it. In some cases, particles with mass can exceed the speed of light in certain types of material, for example high-energy electrons traveling through water in pool-type nuclear reactors. When this happens, the particles emit an eerie glow called Cherenkov radiation. (Fun fact: As you can see below, this glow is blue in color, not neon-green as seen on The Simpsons.)

As for the implications of breaking the speed of light, some physicists are holding off on scrapping the theory of relativity until the results are confirmed at other facilities.

Alvaro De Rujula, a theoretical physicist at CERN, the European Organization for Nuclear Research outside Geneva from where the neutron beam was fired, said he blamed the readings on a so-far undetected human error.

If not, and it’s a big if, the door would be opened to some wild possibilities.

The average person, said De Rujula, “could, in principle, travel to the past and kill their mother before they were born.”

Even in the face of such wild possibilities, I admire the restraint and humility of the CERN research group that conducted the experiment:

But Ereditato [spokesman for the CERN research group] and his team are wary of letting such science fiction story lines keep them up at night.

“We will continue our studies and we will wait patiently for the confirmation,” he told the AP. “Everybody is free to do what they want: to think, to claim, to dream.”

He added: “I’m not going to tell you my dreams.”

Compared with the wild speculation of some other scientists over similarly startling results in the recent past, this is refreshing.

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Astronomers find several new “Super-Earths”

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Is our planet alone in its ability to host life? So far, it’s unique in the Solar System, which is dominated by apparently lifeless bodies, but it may not be unique in the universe. Astronomers have long speculated about the presence of extraterrestrial life elsewhere in the cosmos, but thanks to two planet-searching projects — ESO’s HARPS project and NASA’s Kepler mission — they are closer than ever to finding suitable candidate hosts orbiting other stars. Teams for both have announced intriguing discoveries in the last year, the latest of which includes detection by HARPS of a planet that is only 3.6 times the mass of Earth.

While Kepler is a space-based mission that searches for planetary transits — planets periodically passing in front of their host stars — HARPS (High Accuracy Radial velocity Planet Searcher) is part of the land-based La Silla telescope located in the Atacama Desert of Chile. The HARPS spectrograph looks for periodic shifts in the light from stars, tell-tale signs of gravitational tugs by orbiting planets. Most of the planets discovered by Kepler are orbiting distant stars; the planets discovered by HARPS, however, are orbiting nearby stars, and will be much easier to observe in follow-up projects to detect, for instance, spectral signs of water and other substances necessary for life as we know it.

The HARPS team at ESO recently announced the discovery of 50 new extra-solar planets, or exoplanets, including 16 planets designated as “Super-Earths.” A Super-Earth is a planet 2-10 times the mass of the Earth, but not necessarily rocky in composition; such planets could also be gas dwarfs without any discernible solid surface. One of the recently-discovered Super-Earths, designated HD 85512 b, is a rocky planet located just within the habitable zone around its parent star. The habitable zone is the orbital proximity to a parent star that allows the presence of liquid water on a planet’s surface. The holy grail, as it were, of planet searches is an Earth-like planet with the presence of liquid water — the essential ingredient for life as we know it. The mass of HD 85512 b is tantalizingly close to that of Earth — about 3.6 times greater. Professor Dimitar Sasselov, an astronomer at Harvard University (and the scientist who coined the term “Super-Earth”), speculates that such planets may be even better suited for life than our own Earth due to increased tectonic activity and stable rotation.

Astronomers point out that the frequency of exoplanet discoveries is increasing, and we seem to be on the verge of discovering that the universe is awash in potential hosts for life. So what does all this mean for Christians? Personally, I do not rely on the uniqueness of Earth to bolster my belief in a Creator. It may well be that many planets suitable for advanced life exist elsewhere in the universe, and such planets and life would be part of God’s purpose, as the many different continents and the variety of life on Earth are undoubtedly part of God’s purpose. Furthermore, the existence of many potentially life-supporting planets in the vast universe in no way diminishes the power of the fine-tuning argument, which says that the many physical constants and parameters that permit the existence of life as we know it — nearly 100 characteristics as identified by Hugh Ross — are so finely tuned that even the ostensibly atheist astrophysicist, Fred Hoyle, concluded “the universe looks like a put-up job.”

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Comet Elenin is not a threat to Earth

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Comets have historically been regarded as omens, but whether good or bad is not always clear. Halley’s Comet appeared to observers in England in 1066 and was believed to be an omen. Harold II was defeated at the Battle of Hastings later that year, but William the Conquerer prevailed. Bad omen for Harold, good omen for William? In later centuries, Halley’s periodic appearance sometimes coincided with other historically significant events in Christendom, leading some — even prominent Church leaders at the time — to believe that the comet was a harbinger of doom.

We can forgive these people for their superstitions, given how little was known at that time about natural science. But in the 21st century, it is surprising (to me anyway), when so much is known about the natural causes of celestial events and how little physical influence they have on the Earth, that they are still regarded as omens. Take, for instance, the conspiracy theories involving the recently-discovered Comet Elenin. These “theories” mostly seem to predict cataclysmic events on Earth, yet are not based on any of the known facts about Elenin.

Motivated by the strange press surrounding the comet’s appearance, NASA’s Jet Propulsion Laboratory has compiled a list of answers to the most popular questions about Comet Elenin, and explains why it is not a threat to Earth. In short:

  • It is one of many comets that are discovered each year.
  • It is a smallish comet.
  • It will remain far away. Its closest approach, in mid-October, will bring it 35 million km from Earth — that’s 90 times the distance from the Earth to the Moon. (Ed. note: Comet McNaught, pictured above, came even closer to Earth — 26 million km — in January, 2007.)
  • Its gravitational influence on Earth, even at closest approach, will essentially be zilch.
  • It will not block out any light from the Sun as it passes by.

There is no shortage of genuine disasters — both man-made and natural — that we can worry about. Strike Comet Elenin from the list.

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A supercomputer-simulated Milky Way galaxy

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Astrophysicists working in California and Zurich have created a virtual Milky Way galaxy using a sophisticated supercomputer simulation that took an astonishing eight months to run.

Even without the need for all that computing time, it’s not easy to create a spiral galaxy. Previous attempts yielded awkward results, but the astrophysicists working on this simulation were able to account for important processes — like supernova winds that push hydrogen gas out of a galaxy and shut down star formation — to produce a galaxy that has the right proportions.

The main challenge was to create the galaxy in the context of current cosmology, which says that the universe is mostly made up of stuff we can’t even see — dark matter and dark energy. Cosmologists (physicists who study the overall structure and evolution of the universe) have calculated what percent of the total ‘stuff’ of the universe is comprised of each major component — visible matter, dark matter, and dark energy. Astrophysicists who study galaxy formation were then tasked with figuring out how to create a Milky Way-like galaxy given these proportions. Here is the model of the universe they were given:

Data from sky surveys, such as the Sloan Digital Sky Survey, show that the universe appears on large scales to be comprised of giant sheets and chains surrounding enormous voids. Galaxies are the visible building blocks of this cosmic web-like structure. Dark matter is posited to be the main gravitational component in creating these sheets and chains, drawing hydrogen gas in to eventually create galaxies. Notice in the simulation how big globs slammed into the galaxy from all directions as it was forming — those were flows of cold hydrogen gas and smaller galaxies crashing into the nascent spiral galaxy.

The following is an excellent (and incredibly beautiful) series of simulations showing the large-scale structure of the universe and how this cosmic web likely formed:

Note: Gpc = gigaparsecs (a billion parsecs); Mpc = megaparsecs (a million parsecs); one parsec = approximately three light-years. (The ‘h’ is a parameter for the Hubble constant, which basically says how fast the universe is expanding. Its value is approximately 1.) The Milky Way is about 100,000 light-years across. The initial scale of the Millenium simulation is therefore HUGE. It’s not until the sim zooms in to the smallest scales that you can discern individual galaxies.

This most recent supercomputer simulation of the Milky Way-like spiral galaxy is a step forward, because it demonstrates that it’s possible to create such a galaxy given the known laws of physics and what we understand about the overall structure of the universe.

Higgs boson running out of places to hide

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I’m starting to get whiplash from all this back-and-forth on the Higgs boson (aka the “God particle”), but now its existence is really looking doubtful:

Scientists chasing a particle they believe may have played a vital role in [the] creation of the universe indicated on Monday they were coming to accept it might not exist after all.

But they stressed that if the so-called Higgs boson turns out to have been a mirage, the way would be open for advances into territory dubbed “new physics” to try to answer one of the great mysteries of the cosmos. …

“Whatever the final verdict on Higgs, we are now living in very exciting times for all involved in the quest for new physics,” Guido Tonelli, from one of the two LHC detectors chasing the Higgs, said as the new observations were announced.

You have to admire their willingness to drop the Higgs hypothesis if it doesn’t work out. The idea has been around for decades, and a lot of hopes were pinned on it being right. But the willingness to go where the data take you is what moves science forward.

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