SpaceJibe

October 28, 2013

Coldest Known Object In Space Reveals Its Ghostly Figure

Filed under: Big Bang, Cool, Cosmology, Gamma Ray Bursts, Supernova — bferrari @ 5:55 pm
Image Caption: The Boomerang Nebula reveals its true shape with ALMA. The background blue structure, as seen in visible light (HST), shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in red. (FULL IMAGE) (Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai)

Image Caption: The Boomerang Nebula reveals its true shape with ALMA. The background blue structure, as seen in visible light (HST), shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in red. (FULL IMAGE) (Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai)

The Boomerang Nebula, at a crisp one degree Kelvin (-458 degrees Fahrenheit), is the coldest known object in the Universe. In fact, the Boomerang Nebula is colder than the faint afterglow of the Big Bang, which is the natural background temperature of space.

To learn more about this intriguing object, a team of astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to investigate its frigid properties and determine its true shape, which is eerily ghost-like.

The nebula appeared lopsided when originally observed with ground-based telescopes. This lopsidedness is how this nebula got its name. A bow-tie-like structure was revealed when astronomers later used Hubble Space Telescope observations. According to the new ALMA observations, the Hubble data only told part of the story. The twin lobes seen in the Hubble image may actually be a trick of the light as seen at visible wavelengths.

“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” saidRaghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory (JPL). “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”

The results of this study were published in the Astrophysical Journal.

Located approximately 5,000 light-years away in the constellation Centaurus, the Boomerang Nebula is a relatively young example of an object known as a planetary nebula. Contrary to their name, planetary nebulae are actually the end-of-life phases of stars like our Sun that have sloughed off their outer layers. The remaining centers are white dwarf stars, emitting intense ultraviolet radiation that causes the gas in the nebulae to glow and emit light in brilliant colors.

The Boomerang is an example of a pre-planetary nebula, which is a stage in a star’s life immediately preceding the planetary nebula phase. At this point, the central star is not yet hot enough to emit enough electrical ultraviolet radiation to produce its characteristic glow. A pre-planetary nebula is seen by starlight reflecting off its dust grains.

The gas outflow from the Boomerang Nebula’s star is expanding rapidly and cooling itself in the process, in a way similar in principle to the way refrigerators use expanding gas to produce cold temperatures. The astronomers were able to gauge the temperature of the gas in the nebula by seeing how it absorbed the cosmic microwave background radiation, which has a very uniform temperature of 2.8 degrees Kelvin (-455 degrees Fahrenheit).

“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”

Single-dish millimeter wavelength telescopes, however, did not detect the narrow waist observed by the Hubble. Rather, they found a more uniform and nearly spherical outflow of material.

ALMA has unprecedented resolution, which allowed the astronomers to reconcile the discrepancy. The team was able to detect the double-lobe structure that is seen in the Hubble image, but only in the inner regions of the nebula, by observing the distribution of carbon monoxide molecules, which glow brightly at millimeter wavelengths. A more elongated cloud of cold gas that is roughly round was observed farther out.

A dense lane of millimeter-sized dust grains were found to be surrounding the star, providing an explanation for why the outer cloud has an hourglass shape in visible light. The dust grains form a mask that shade a portion of the central star, allowing its light to leak out in narrow but opposite directions in the cloud. This forms the hourglass appearance.

“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”

The current findings also suggest that the outer fringes of the nebula are beginning to warm, even though they are slightly colder than the cosmic microwave background. The warming could be caused by the photoelectric effect — an effect first proposed by Albert Einstein in which light is absorbed by solid material, which then re-emits electrons.

 

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Largest Known Star Self-Destructs While Astronomers Observe

Filed under: Cool, Gamma Ray Bursts, Supernova — bferrari @ 5:35 pm
(European Southern Observatory)

(European Southern Observatory)

A group of international scientists have been observing as the largest known star in the Universe tears itself apart.

Astronomers from the UK, Chile, Germany and the US have watched as W26 in the Westerlund 1 star cluster shed its outer layers and flings a huge cloud of glowing hydrogen gas out to return enriched material back to the interstellar medium.

The latest observation, reported in the journal Monthly Notices of the Royal Astronomical Society, is considered to be a vital step in understanding how massive stars help enrich the space between stars, which is necessary for forming planetary systems.

Westerlund 1 is the most massive cluster of stars in the Milky Way galaxy. The cluster, which is 16,000 light years away from Earth, is home to several hundred thousand stars. Astronomers used the Very Large Telescope (VST) at the European Southern Observatory’s Paranal Observatory in Chile to observe Westerlund 1 when they happened to discover W26.

They realized that the star was probably the largest ever discovered, with a radius 1,500 times larger than our Sun. They also discovered that W26 is one of the most luminous red supergiants ever seen.

Glowing hydrogen-gas clouds like the one seen around W26 are rarely found around massive stars, and are even rarer around red supergiants. This was the first ionized nebula ever discovered around such a star. While W26 is too cool to make the gas glow, the astronomers believe the source of the ionizing radiation could be either hot blue stars or possibly a companion star.

The nebula around W26 is similar to the nebula surrounding SN1987A, which is the remnant of a star that exploded as a supernova in 1987. SN1987A was the closest observed supernova to Earth since 1604, and it gave astronomers a chance to better understand the properties of these explosions.

Astronomers will be able to use the new nebula around W26 to better understand the mass loss processes around massive stars. Stars with masses tens of times larger than the Sun live very short and dramatic lives, with some having lifetimes of less than a few million years before they exhaust all of their nuclear fuel and explode as a supernova.

When a massive star reaches the end of its life it becomes highly unstable, ejecting a considerable amount of material from its outer envelopes. This material has been enriched by nuclear reactions deep within the star and includes many of the elements necessary for forming rocky planets like Earth. Knowing more about how this material is ejected and how it affects the evolution of the star would enable scientists to better understand the evolution of our universe.

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October 9, 2013

Meet the asteroid that might hit Earth in 2880

Radar image of 1950 DA acquired by the Arecibo Observatory on March 4, 2001. (NASA/JPL/S. OSTRO)

Radar image of 1950 DA acquired by the Arecibo Observatory on March 4, 2001. (NASA/JPL/S. OSTRO)

There are over 10,000 near-Earth objects (NEOs) that have been identified so far — asteroids and comets of varying sizes that approach the Earth’s orbital distance to within about 28 million miles. Of the 10,000 discoveries, roughly 10 percent are larger than six-tenths of a mile in size — large enough to have disastrous global consequences should one impact the Earth.

This is one of them.

First discovered in February 1950, 1950 DA is a 1.1-kilometer-wide asteroid that was observed for 17 days and then disappeared from view. Then it was spotted again on Dec. 31, 2000 — literally on the eve of the 21st century. Coupled with radar observations made a few weeks later in March 2001 it was found that, along with a rather high rotation rate (2.1 hours), asteroid 1950 DA has a trajectory that will bring it very close to Earth on March 16, 2880. How close? Close enough that, within a specific 20-minute window, a collision can not be entirely ruled out.

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The image above was made from radar observations by the Arecibo Observatory in Puerto Rico in March 2001, when 1950 DA passed within 4.8 million miles of Earth. Is this the mug shot of a future continent-killer?

Radar analysis and research of 1950 DA performed by NASA’s Jet Propulsion Laboratory scientists J.D. Giorgini, S. J. Ostro, Don Yeomans and several others from JPL and other institutions revealed that the impact probability from 1950 DA in March 2880 is, at most, 1 in 300 based on what is known about the asteroid so far.

1 in 300 may sound like a slim chance, but actually this represents a risk 50% greater than that of the average hazard due to all other asteroids from now to then.

However, that’s a maximum value. The study also noted the collision probability for 1950 DA as being in the range from 0 to 0.33%. That upper limit could increase or decrease as more is learned about the asteroid. (The next opportunity for studying 1950 DA via radar is in 2032.)

There are many factors that influence the path of an asteroid through space. Its spin rate, reflectivity (albedo), composition, mass, terrain variations… gravitational interactions with other bodies, some of which may not even have been discovered yet… all of these can affect the movement of an asteroid and, more specifically, its exact position at a future point in time. While many of these things still aren’t precisely known for 1950 DA, one in particular could end up being the saving grace for our descendants: the Yarkovsky effect.

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A small but important force acting upon asteroids, the Yarkovsky effect is a “nudge” created by thermal emission. As an asteroid gathers heat energy from the sun, it releases some of that energy back into space. Thanks to Newtonian mechanics the sheer act of doing so creates a physical push back on the asteroid itself, altering its course ever so slightly. Over a long span of time, this slight alteration could result in the relocation of 1950 DA away from the spot in space where Earth will be on March 16, 2880… at least enough so that a miss is certain.

In fact, recent research by JPL scientists D. Farnocchia and S.R. Chesley have taken into consideration the Yarkovsky effect on 1950 DA based on known values from previous observations, as well as new research suggesting that the asteroid has a retrograde rotation. While their latest assessment does put the risk of an impact in 2880 within the lower end of the probability spectrum (4×10^-4, or -0.58 on the Palermo Scale) it is still far from zero, and in fact remains higher than any other known potential impacts.

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So what would happen if the half-mile-wide 1950 DA were to hit Earth? While that depends on a lot of things, such as its composition, speed, angle of impact, where it impacts, etc., needless to say it would cause a lot of damage across a large area. I’m talking an energy release upwards of half a million megatons, which, were it to strike say, New York City, everything within at least a 100-mile radius would be flattened by the force of the impact alone — that’s halfway to Boston and Washington, DC. And that’s not even taking into consideration the air blast, atmospheric dust cloud, secondary impacts from debris, or damage from any resulting tsunami (if the impact were in the ocean)… the destruction would easily extend out many more hundreds of miles, and the repercussions — physical, financial, economic, and emotional — would extend around the globe.

But again, precisely where 1950 DA will be in another 866 1/2 years (and whether or not it will occupy the same point in space as our planet) relies on many factors that aren’t well known — even though its orbit is pretty well understood. More in-depth observations will need to be made, and that is why asteroids like this must be carefully — and continually — watched.

Luckily, 35 generations offers plenty of time to improve our knowledge. According to JPL’s Near-Earth Object program, “If it is eventually decided 1950 DA needs to be diverted, the hundreds of years of warning could allow a method as simple as dusting the surface of the asteroid with chalk or charcoal, or perhaps white glass beads, or sending a solar sail spacecraft that ends by collapsing its reflective sail around the asteroid. These things would change the asteroids reflectivity and allow sunlight to do the work of pushing the asteroid out of the way.”

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Still, whether because of ongoing research, faith in future generations of scientists, or just sheer probability, JPL remains confident that 1950 DA should cause little concern. “The most likely result will be that St. Patrick’s Day parades in 2880 will be a little more festive than usual as 1950 DA recedes into the distance, having passed Earth by.”

Let’s just hope the luck of the Irish is with our planet big time that year…

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October 8, 2013

Massive laser inching closer to mastering fusion power

Filed under: Big Bang, Black Holes, Cool, Gadgets, Wierd — bferrari @ 2:15 pm
A service system lift allows technicians to access the target chamber interior at the National Ignition Facility for inspection and maintenance. (LAWRENCE LIVERMORE NATIONAL LABORATORY)

A service system lift allows technicians to access the target chamber interior at the National Ignition Facility for inspection and maintenance. (LAWRENCE LIVERMORE NATIONAL LABORATORY)

Researchers have reportedly taken one small yet giant step towards “perfect power” — fusion, the process that powers the sun and may ultimately solve the world’s energy problems.

Fusion is similar to fission, where atoms are split releasing massive amounts of energy. But instead of being torn apart, fusion welds atoms together. It’s a perfect power because more energy is released than used, and a sort of holy grail for physicists.

To attempt it, scientists at the National Ignition Facility at Lawrence Livermore Labs in California use an ultrapowerful laser system, which melds 192 laser beams into a single incredible burst of energy that heats and compress a capsule of hydrogen fuel to the point at which fusion take place.

The result of a late September test: the amount of energy released through the fusion reaction was greater than the amount of energy used, the BBC reported.

Reached on the phone by FoxNews.com, a NIF spokeswoman was unable to comment on the record due to the government slimdown.

The achievement was just one small part of the reaction needed to achieve fusion, a state NIF labels “ignition.” But along with other successes, it moves the chains closer to the ultimate goal.

In mid-August, the National Ignition Facility passed another milestone: The facility was activated for 14 billionths of a second and its power pointed at a tiny capsule of fuel. They generated approximately 350 trillion watts of power — hundreds of times more than the entire United States consumes at any given instant.

“We’re working in a place where no human has ever gone before,” Ed Moses, principle associate director for NIF and Photon Science, told FoxNews.com at the time. “We’re working on the bleeding edge of fusion physics.”

In the August test, NIF dialed down the laser beam’s power and tweaked it, for tremendous results.

We lowered the energy a tiny bit — about 5 percent — but more important, we changed the shape of the energy pulse. We moved energy from the back of the pulse to the front. We got three times the energy out,” Moses told FoxNews.com.

“Our goal is to get fusion burn — more energy out than we put in.”

The September success was likely due to a similar tweak to the energy pulse.

Because the laser is on for the merest fraction of a second, it costs little to operate — between $5 and $20 per blast. Still, the cost of the facility has raised temperatures in Washington. The gigantic laser lab was built in California for $3.5 billion in 2008, and ran up approximately $1.5 billion more in operating costs over the past five years.

Despite the latest success, ignition hasn’t happened, and NIF’s managers admitted to Congress in December of 2012 that they can’t guarantee that it will ever succeed.

“At present, it is too early to assess whether or not ignition can be achieved at the National Ignition Facility,” wrote Thomas P. D’Agostino, administrator of the National Nuclear Security Administration (NNSA) in a report requested by Congress last year.

Congress had given the facility until the end of 2012 to achieve its goal of ignition. The NNSA report proposed instead a three-year program to better understand why the actual implosion does not agree with scientific models.

And three years may not be enough. “The three-year plan culminates in a comprehensive review at the end of FY 2015. At that time, NNSA will have an assessment of the likelihood and schedule for achieving ignition,” the report said.

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