Thursday, May 31, 2007

Screaming CMEs

Coronal Mass Ejections (CMEs) begin when the sun launches a billion tons of electrically conducting gas (plasma) into space at millions of miles per hour.

A CME cloud is laced with magnetic fields, and CMEs directed our way smash into Earth's magnetic field. If the CME magnetic fields have the correct orientation, they dump energy into Earth's magnetic field, causing magnetic storms. These storms can cause widespread blackouts by overloading power line equipment with extra electric current. But wait; there's more.

Some CMEs also bring intense radiation storms that can disable satellites or cause cancer in unprotected astronauts. As the CME blasts through space, it plows into a slower stream of plasma blown constantly from the sun in all directions, called the solar wind. The CME causes a shock wave in the solar wind. If the shock is strong enough, it accelerates electrically charged particles that make up the solar wind to high speeds, forming the radiation storm.

For animation and more, visit NASA screaming CMEs

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Tuesday, May 29, 2007

Colliding Supergiants

This false-color image from the Curtis Schmidt Telescope in Chile shows a large star-forming region in the Large Magellanic Cloud. The binary system LH54-425 is arrowed. It is located in the star cluster LH54.
Credit: Chris Smith and the University of Michigan Curtis Schmidt Telescope at CTIO.

Using NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite and ground-based telescopes, astronomers have determined, for the first time, the properties of a rare, extremely massive, and young binary star system.

The merger of two massive stars to make a single super star of over 80 suns could lead to an object like Eta Carinae, which might have looked like LH54-425 one million years ago.

Finding stars this massive so early in their life is very rare. These results expand our understanding of the nature of very massive binaries, which was not well understood. The system will eventually produce a very energetic supernova.

The system, known as LH54-425, is located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The binary consists of two O-stars, the most massive and luminous types of stars in the Universe.
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Spectra obtained by Georgia State University astronomer Stephen Williams at the 1.5-meter (4.9 foot) telescope at the Cerro Tololo Inter-American Observatory in Chile show that the two stars contain about 62 and 37 times the mass of our Sun. “The stars are so close to each other - about one-sixth the average Earth-Sun distance - that they orbit around a common center of mass every 2.25 days,” says Douglas Gies of Georgia State University, Atlanta. With a combined mass of about 100 suns, the system is one the most extreme binaries known. The stars are probably less than 3 million years old.

Each star blows off a powerful stellar wind, and FUSE’s observations have provided the first details of what happens when the two supersonic winds collide. The wind collision zone wraps around the smaller star and produces a curved surface of superheated gases that emit X-rays and far-ultraviolet radiation. FUSE is ideal for these measurements because the lines that best indicate the properties of stellar winds show up in the far ultraviolet part of the spectrum, where FUSE is most sensitive.

FUSE project scientist George Sonneborn of NASA Goddard Space Flight Center, presented these results today in a poster at the spring 2007 American Astronomical Society meeting in Honolulu, Hawaii.

The more massive star is shedding material at a rate of 500 trillion tons per second (about 400 times greater than the rate the sun loses mass through the solar wind), with a speed of 5.4 million miles per hour. The smaller star is ejecting mass at about one-tenth the rate of its sibling. The mass loss rate of both stars is consistent with other single stars having the same temperature and luminosity.

As the stars age and swell in size, they will begin to transfer substantial amounts of mass to each other. This process could begin in a million years. The stars are orbiting so close to each other that they are likely to merge as they evolve, producing a single extremely massive star like the more massive member of the Eta Carinae binary system. Eta Carinae is one of the most massive and luminous stars in the Milky Way Galaxy, with perhaps 100 solar masses.

NASA's FUSE Satellite Catches Collision of Titans
by Bob Naeye - Goddard Space Flight Center.

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Monday, May 28, 2007

Solar Radiation Storm

Solar radiation storms are swarms of electrons, protons and heavy ions accelerated to high speed by explosions on the sun. Here on Earth we are protected from these particles by our planet's atmosphere and magnetic field.

Astronauts in Earth orbit are fairly safe, too; Earth's magnetic field extends out far enough to shield them. The danger begins when astronauts leave this protective cocoon. The Moon and Mars, for instance, have no global magnetic fields, and astronauts working on the surface of those worlds could be at risk.

Spacecraft and satellites are also affected. Subatomic particles striking CPUs and other electronics can cause onboard computers to suddenly reboot or issue nonsense commands. If, say, a satellite operator knows that a storm is coming, he can put his craft in a protective "safe mode" until the storm passes.

The type of particle most feared by astronaut safety experts is the ion, that is, an atom which has lost one or more of its charge-balancing electrons. Energetic ions can damage tissue and break strands of DNA, causing health problems ranging from nausea to cataracts to cancer.
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So the goal is to predict when the ions will arrive. The key it turns out, are electrons. Electrons are always detected ahead of the more dangerous ions.

This has been known for years, but only recently has research turned the electrons first aspect of radiation storms into a forecasting tool.

The key to the breakthrough was the COSTEP instrument onboard SOHO. COSTEP is short for "Comprehensive Suprathermal and Energetic Particle Analyzer." Essentially, the device counts particles coming from the sun and measures their energies.

Arik Posner, a physicist in NASA's Science Mission Directorate, looked at hundreds of radiation storms recorded by COSTEP between 1996 and 2002, and was able to construct an empirical, predictive matrix that can be used to forecast the ions' arrival time from the electron data.

Posner's ion storm forecasting matrix.
After testing the results, the matrix was used on COSTEP data gathered in 2003, a year that had not yet been analyzed and formed no part of the matrix itself. The matrix was applied to the electron data and as a result, it successfully predicted all four major ion storms of 2003 with advance warnings ranging from 7 to 74 minutes. The method did, however, also create three false alarms from the 2003 dataset. Improvements will come as Posner works his way through even more of COSTEP's dataset.

The Solar and Heliospheric Observatory (SOHO), is a project of international cooperation between ESA and NASA.
Artist's concept of a radiation storm approaching Earth. Courtesy of Dr. Tony Phillips

Cosmic rays pose a threat to astronauts bound for Mars.
Researchers discuss what a big proton storm might do to someone on the Moon.

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Sunday, May 27, 2007

Reflection Nebula

Credit & Copyright: T. Rector (Anchorage), H. Schweiker, WIYN, NOAO, AURA, NSF

The dust is so thick in the Center of Reflection Nebula NGC 1333 that you can hardly see the stars forming.

Conversely, the very dust clouds that hide the stars also reflects their optical light, giving NGC 1333's predominantly blue glow the general designation of a reflection nebula.

A highly detailed image of the nebula, shown above, was taken recently by the Mayall 4-meter telescope on Kitt Peak in Arizona, and released to honour astronomer Stephen Strom on his retirement.

Visible near the image top are vast blue regions of dust predominantly reflecting the light from bright massive stars. Visible in the thick central dust are not only newly formed stars but red jets and red-glowing gas energized by the light and winds from recently formed young stars.

The NGC 1333 nebula contains hundreds of newly formed stars that are less than one million years old. Reflection nebula NGC 1333 lies about 1,000 light years away toward the constellation of Perseus.

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Horse Head Nebula (NOAO)

The Horsehead Nebula Credit & Copyright: Nigel Sharp (NOAO), KPNO, AURA, NSF

One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s.

The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis.

The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1500 years to reach us from the Horsehead Nebula. The above image was taken with the 0.9-meter telescope at Kitt Peak National Observatory.

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Friday, May 25, 2007

Rogue Black Holes

Astronomers are hunting an elusive target: rogue black holes that have been ejected from the centers of their home galaxies.

Some doubted that the quarry could be spotted, since a black hole must be gobbling matter from an accretion disk in order for that matter to shine. (Image Credit: NASA)

And if a black hole is ripped from the core of its home galaxy and sent hurling into the outskirts, the thinking goes, then its accretion disk might be left behind.

New calculations by theorist Avi Loeb (Harvard-Smithsonian Center for Astrophysics) give black hole hunters a reason to hope. Loeb showed that, generically, a black hole ejected from the center of a galaxy could bring its accretion disk along for the ride and remain visible for millions of years.

"Matter in the disk is swirling around the black hole much faster than the typical black-hole ejection speed. That matter is so tightly bound that it follows the black hole like a herd of sheep around a shepherd," said Loeb.

In the scenario examined by Loeb, two galaxies collide and merge. The spinning, supermassive black holes at the core of each galaxy coalesce, emitting powerful gravitational radiation in a preferred direction. Computer simulations recently demonstrated that the net momentum carried by the radiation gives the remnant black hole a large kick in the opposite direction. The black hole recoils at speeds of up to ten million miles per hour -- fast enough to traverse an entire galaxy in a cosmically short time of only ten million years.
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Although the prediction of recoiling black holes in galaxy mergers has been shown to be robust, it was unclear until Loeb's paper whether the phenomenon could have optically observable consequences. Loeb examined the question of whether the black hole could hold onto its accretion disk while being ejected. He found that as long as the gas within the disk was orbiting at a speed far greater than the black hole ejection speed, the accretion disk would follow the black hole on its journey.

Moreover, the gaseous disk should not be consumed during the earlier binary coalescence phase that precedes the ejection because the black hole binary tends to open a cavity in the disk, like a spinning blade in a food processor.

After the two black holes join to become one, the accretion disk could feed the remnant black hole for millions of years, allowing the black hole to shine brilliantly. Such black holes at cosmological distances are called quasars.

Before the black hole's fuel is exhausted, it could travel more than 30,000 light-years from the center of its galaxy. At typical cosmological distances, that would equate to a separation on the sky of about one arcsecond (the size of a dime viewed from one mile away). Such separations are challenging to detect, since the quasar's brightness may overwhelm the fainter galaxy.

The powerful release of energy by a quasar shapes the evolution of its host galaxy. Previous theoretical calculations assumed that a quasar is pinned to the center of its galaxy where most of the gas concentrates. "However, the feedback from a recoiled quasar would be distributed along its trajectory, and would resemble the visible track of a subatomic particle in a bubble chamber," commented Loeb.

His paper argues that although most of the kicked black holes would remain bound to their host galaxies, their feedback and growth would be different than previously envisioned.

"Most importantly, this work is a good motivation for observers to search for displaced quasars," added Loeb.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

How to Spot the Speediest Black Holes CfA press release.

Survival time inside the event horizon of a black hole from Universe Today
No Way Back: Maximizing survival time below the Schwarzschild event horizon
GRB's active longer than previously thought from Science Daily

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Thursday, May 24, 2007

Brown Dwarf joins Jet Set

Image Credit: Copyright ESO

Jets of matter have been discovered around a very low mass 'failed star', mimicking a process seen in young stars. This suggests that these 'brown dwarfs' form in a similar manner to normal stars but also that outflows are driven out by objects as massive as hundreds of millions of solar masses down to Jupiter-sized objects.

The brown dwarf with the name 2MASS1207-3932 is full of surprises. Its companion, a 5 Jupiter-mass giant, was the first confirmed exoplanet for which astronomers could obtain an image , thereby opening a new field of research - the direct detection of alien worlds. It was then later found that the brown dwarf has a disc surrounding it, not unlike very young stars.

Now, astronomers using ESO's Very Large Telescope (VLT) have found that the young brown dwarf is also spewing jets, a behaviour again quite similar to young stars.

The outflows were discovered using an amazing technique known as spectro-astrometry, based on high resolution spectra taken with UVES on the VLT. While in normal young stars - known as T-Tauri stars for the prototype of their class - the jets are large and bright enough to be seen directly, this is not the case around brown dwarfs: the length scale of the jets, recovered with spectro-astrometry is only about 0.1 arcsecond long.

The jets stretch about 1 billion kilometres and the material is rushing away from the brown dwarf with a speed of a few kilometres per second. Astronomers had to rely on the power of the VLT because the observed emission is extremely faint and only UVES on the VLT could provide both the sensitivity and the spectral resolution they required.

Using the same technique and the same telescope, the team had previously discovered outflows in another young brown dwarf. The new discovery sets a record for the lowest mass object in which jets are seen.

Outflows in the Universe, are observed rushing away from the active nuclei of galaxies (AGNs) and emerging from young stars. These observations show the outflow mechanism extends over an enormous range of masses, from several tens of millions of solar mass (for AGNs) down to a few tens of Jupiter masses (for brown dwarfs).

VLT Finds Smallest Galactic Object with Jets ESO press release
A Brown Dwarf Joins the Jet Set from Science Daily
Brown Dwarf with jets discovered from Universe Today
Merging Stars create a new class of explosion from Universe Today

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Tuesday, May 22, 2007

A Close Neighbour

Andromeda, the nearest major galaxy to the Milky Way, is shown here in this wide-field optical image from Kitt Peak.

Located in the constellation of Andromeda (the Princess), the Andromeda Galaxy is a large spiral galaxy over 65,000 light years in diameter and approximately 2.9 million light years from Earth.
(Credit: NOAO/AURA/NSF/T.Rector & B.A.Wolpa)

The central region of Andromeda is shown in a composite image, with X-rays from NASA's Chandra X-ray Observatory (blue) combined with the optical image. Astronomers believe that Andromeda, also known as Andromeda Galaxy (M31), and the Milky Way will merge in a few billion years.

In the composite image (insert), hot, X-ray bright gas is seen to envelop the middle of Andromeda. Point sources are also prominent, which mostly reveal pairs of stars that are interacting with each other. Many of these double stars are thought to include white dwarfs pulling large amounts of material away from a companion star. When the amount of gas being dumped onto the white dwarf gets too high a thermonuclear explosion occurs on the surface of the white dwarf, emitting bright X-rays. (Credit: NASA/CXC/MPE/W.Pietsch et al)

Andromeda Galaxy (M31):
A New Look at a Close Neighbor
from Chandra

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Monday, May 21, 2007

Solar System goes for a Ride

When Galaxies Collide, our Solar System Will Go for a Ride


Illustration: NASA/CXC/M.Weiss

For decades, astronomers have known that the Milky Way galaxy is on a collision course with the neighboring Andromeda spiral galaxy. What was unknown until now: the fate of the Sun and our solar system in that melee. New calculations by theorists T.J. Cox and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) show that the Sun and its planets will be exiled to the outer reaches of the merged galaxy. Moreover, the collision will take place within the Sun's lifetime, before it becomes a burned-out white dwarf star.

"You could say that we're being sent to a retirement home in the country," said Cox. "We're living in the suburbs of the Milky Way right now, but we're likely to move much farther out after the coming cosmic smash-up."

Computer simulations by Cox and Loeb show that big changes are coming in only 2 billion years, when the Milky Way and Andromeda experience their first close pass. A viewer on Earth would see the night sky evolve from a strip of stars (the Milky Way seen edge-on) to a muddled mess as Andromeda's powerful pull flings stars from their stately orbits.

At that time, the Sun will still be a hydrogen-burning main-sequence star, although it will have brightened and heated enough to boil the oceans from the Earth.

The two galaxies will swing around each other a couple of times, intermingling their stars as gravitational forces stir them together. CfA animation movie

About 5 billion years from now, Andromeda and the Milky Way will have completely combined to form a single, football-shaped elliptical galaxy. The Sun will be an aging star nearing the red giant phase and the end of its lifetime. It and the solar system likely will reside 100,000 light-years from the center of the new galaxy - 4 times further than the current 25,000 light-year distance.

Any descendants of humans observing the future sky will experience a very different view. The strip of Milky Way will be gone, replaced by a huge bulge of billions of stars. Future scientists may look back on today's research as the first prediction of things to come.

"This is the first paper in my publication record that has a chance of being cited five billion years from now," joked Loeb.

The paper describing this research has been submitted for publication to the Monthly Notices of the Royal Astronomical Society.
A Galactic Collision, and the Sun’s Future from Centauri Dreams

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Saturday, May 19, 2007

Cat's Eye Nebula

The Cat's Eye Nebula from Hubble Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA) Click on Image to Enlarge

Staring across interstellar space, the alluring Cat's Eye nebula lies three thousand light-years from Earth. A classic planetary nebula, the Cat's Eye (NGC 6543) represents a final, brief yet glorious phase in the life of a sun-like star. This nebula's dying central star may have produced the simple, outer pattern of dusty concentric shells by shrugging off outer layers in a series of regular convulsions.
But the formation of the beautiful, more complex inner structures is not well understood. Seen so clearly in this sharp Hubble Space Telescope image, the truly cosmic eye is over half a light-year across. Of course, gazing into the Cat's Eye, astronomers may well be seeing the fate of our sun, destined to enter its own planetary nebula phase of evolution ... in about 5 billion years.

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Friday, May 18, 2007

Blackholes in Colliding Galaxies

Adaptive Optics Pinpoints Two Supermassive Black Holes In Colliding Galaxies

Astronomers have used powerful adaptive optics technology at the W. M. Keck Observatory in Hawaii to reveal the precise locations and environments of a pair of supermassive black holes at the center of an ongoing collision between two galaxies 300 million light-years away.

NGC 6240 is an ongoing collision of two gas-rich disk galaxies. Using adaptive optics at the Keck II Telescope, researchers have resolved young star clusters formed because of the merger (small blue dots), and have identified which features within the twin nuclei are associated with the two supermassive black holes known to inhabit the nuclear regions. The green vertical line represents one second of arc, or 1,600 light years at the distance of NGC 6240.
(Credit: C. Max, G. Canalizo, W. de Vries)
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The new observations of the galaxy merger known as NGC 6240 reveal that each of the black holes resides at the center of a rotating disk of stars and is surrounded by a cloud of young star clusters formed in the merger, said Claire Max, professor of astronomy and astrophysics at the University of California, Santa Cruz.

"People had observed this pair of colliding galaxies at different wavelengths and seen what they thought were the black holes, but it's been very hard to make sense of how the observations at various wavelengths correspond to each other," Max said. "The adaptive optics results enabled us to tie it all together, so now we can really see it all--the hot dust in the infrared, the stars in the visible and infrared, and the x-rays and radio emissions coming from right around the black holes."

Adaptive Optics (AO) enables astronomers to counteract the blurring effects of turbulence in Earth's atmosphere, which degrades images seen by ground-based telescopes. Max, who directs the Center for Adaptive Optics at UC Santa Cruz, is the lead author of a paper describing the new findings published by the journal Science. Her coauthors are Gabriela Canalizo, who worked with Max as a postdoctoral researcher at Lawrence Livermore National Laboratory (LLNL) and is now at UC Riverside, and Willem de Vries, a physicist with LLNL and UC Davis.

Images of NGC 6240 in visible light from the Hubble Space Telescope show the outer parts of the colliding galaxies distorted by their ongoing merger into long tidal tails of stars, gas, and dust. In the bright central region, two distinct nuclei can be discerned, but clouds of dust obscure much of the visible light from the core. The presence of two supermassive black holes in NGC 6240 was first demonstrated by x-ray observations from NASA's Chandra X-ray Observatory in 2002. Two pointlike radio sources were also detected in the central region.

But trying to match up the data from one instrument with those obtained at different wavelengths by other instruments is very difficult because there are few common reference points in the various wavelength regimes, Max said. The infrared images her group obtained using the AO system on the 10-meter Keck II Telescope provided the high spatial resolution needed to identify features in NGC 6240 that can be seen in different wavelengths.

"With the infrared images we got at Keck, we were able to line up the information from all the different wavelengths to determine which features in the images are the black holes," Max said.

The infrared wavelengths are less affected by dust than visible light, and the Keck infrared images show distinct nuclei with complex substructure surrounded by many faint point sources. The faint point sources are young star clusters produced in a burst of star formation triggered by the collision of the two gas-rich galaxies. Pinpointing which of the features in the infrared images correspond to the positions of the black holes involved several steps and required Keck adaptive optics observations at different infrared wavelengths.

"We uncovered it piece by piece, until we were able to make the correspondence between the black holes and the features seen at different wavelengths, as well as the stuff around them," Max said. "It really shows how powerful the Keck adaptive optics system is. We were also fortunate to have an extraordinarily good observing night."

Galaxy mergers are thought to play a major role in the evolution of galaxies and may help explain many of their properties. For example, astronomers have found that the mass of the black hole at the center of a galaxy is highly correlated with large-scale properties of the galaxy itself. The "coevolution" hypothesis explains this correlation as the result of both the black hole and the galaxy around it growing incrementally in repeated merger events over cosmic timescales.

"The gravitational influence of the black hole is actually limited to a relatively small region right around it, so how can it affect the rest of the galaxy" But if the black hole and the galaxy around it evolved together through the same sequence of merger events, that would explain the correlations," Max said. "That's why people are so excited about understanding galaxy mergers, and here we're seeing it in action."

The two black holes in NGC 6240 will eventually, in 10 million to 100 million years, spiral into each other and merge, producing a powerful burst of gravitational radiation, she said.

Story adapted from University of California - Santa Cruz news release

X-rays provide a new way to investigate exploding stars from ESA
Slicing the Universe with HARP/ACSIS - A New Look at Orion from SciTech

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Wednesday, May 16, 2007

Weighing Blackholes

Artists Impression of Black Hole. Credits: NASA

ESA's XMM-Newton has helped to find evidence for the existence of controversial Intermediate Mass Black Holes. Scientists used a new, recently proven method for determining the mass of black holes.

Nikolai Shaposhnikov and Lev Titarchuk, at NASA’s Goddard Space Flight Center (GSFC), have used the technique to determine the mass of the black hole, Cygnus X-1, located in the constellation Cygnus (the Swan) approximately 10 000 light years away in our Galaxy, the Milky Way.

The elegant technique, first suggested by Titarchuk in 1998, shows that Cygnus X-1, part of a binary system, contains 8.7 solar masses, with a margin of error of only 0.8 solar masses. Cygnus X-1 was one of the first compelling black hole candidates to emerge in the early 1970s. The system consists of a blue supergiant and a massive but invisible companion.

Credits: NASA / Honeywell Max-Q Digital Group / Dana Berry

Artist’s impression of a binary system akin to Cygnus X-1. It consists of a blue supergiant star (right) and a black hole. The black hole is surrounded by a gaseous accretion disk that is fed by the star. Some black holes emit jets along the polar axis, as shown here.

The existence of IMBHs is controversial because there is no widely accepted mechanism for how they could form. But they would fill in a huge gap between black holes such as Cygnus X-1 - which form from collapsing massive stars and contain perhaps 5 to 20 solar masses - and the 'monsters' (up to thousand million solar masses) that lurk in the cores of large galaxies.

Titarchuk’s method takes advantage of a relationship between a black hole and its surrounding accretion disk. Gas orbiting in these disks eventually spirals into the black hole. When a black hole’s accretion rate increases to a high level, material piles up near the black hole in a hot region that Titarchuk likens to a traffic jam.

Titarchuk has shown that the distance from the black hole where this congestion occurs scales directly with the mass of the black hole. The more massive the black hole, the farther this congestion occurs and the longer the orbital period.

In his model, hot gas piling up in the congestion region is linked to observations of X-ray intensity variations that repeat on a nearly, but not perfectly, periodic basis. These Quasi-Periodic Oscillations (QPOs) are observed in many black hole systems. The QPOs are accompanied by simple, predictable changes in the system’s spectrum as the surrounding gas heats and cools in response to the changing accretion rate.

New technique for ‘weighing’ black holes ESA Press Release
Echoes from darkness by Louise Riofrio
A Ring of Dark Matter from Centauri Dreams
Hubble finds Ring of Dark Matter? Hubble Press Release

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Monday, May 14, 2007

Bow Shocks

Credits: NASA/ESA and The Hubble Heritage Team STScI/AURA

The shock wave that sits above the Earth’s surface is a natural phenomenon. It is located on the side facing the Sun, at approximately one quarter of the distance to the Moon, and is caused by the flow of electrically charged particles from the Sun.

This flow of electrically charged particles known as solar wind is emitted in a gusty manner by the Sun. When it collides with the Earth’s magnetic field, it is abruptly slowed down and this causes a barrier of electrified gas, called the bow shock, to build up. It behaves in the same way as water being pushed out of the way by the front of a ship.

On 24 January 2001, the four Cluster spacecraft were flying at an approximate altitude of 105 000 kilometres, in tetrahedron formation. Each spacecraft was separated from the others by a distance of about 600 kilometres. With such a distance between them, as they approached the bow shock, scientists expected that every spacecraft would record a similar signature of the passage through this region.

Instead, the readings they got were highly contradictory. They showed large fluctuations in the magnetic and electric field surrounding each spacecraft. They also revealed marked variations in the number of solar wind protons that were reflected by the shock and streaming back to Sun.

The detection has implications for the way astronomers investigate larger bow shocks around distant celestial objects. Bow shocks are related to some of the most energetic events in the Universe. Exploding stars and strong stellar winds from young stars cause them. Reforming bow shocks can also accelerate particles to extremely high energies and throw them across space.

Although the conditions that cause the reformation of a shock wave are rare around the Earth, they are common around these other celestial objects.

Cluster makes a shocking discovery ESA Press Release
New Horizons & Other Starships - Where are they now? from Astroprof

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Friday, May 11, 2007

Cosmic Clock

The Star, HE 1523-0901. Credit ESO Click Image to Enlarge

Using ESO's VLT, astronomers recently measured the age of a star located in our Galaxy.

"It is very hard to pin down the age of a star", the lead author of the paper reporting the results, Anna Frebel, explains. "This requires measuring very precisely the abundance of the radioactive elements thorium or uranium, a feat only the largest telescopes such as ESO's VLT can achieve."

The technique is analogous to the carbon-14 dating method that has been so successful in archaeology over time spans of up to a few tens of thousands of years. In astronomy, however, this technique must obviously be applied to vastly longer timescales.

For the method to work well, the right choice of radioactive isotope is critical. Unlike other, stable elements that formed at the same time, the abundance of a radioactive (unstable) isotope decreases all the time. The faster the decay, the less there will be left of the radioactive isotope after a certain time, so the greater will be the abundance difference when compared to a stable isotope, and the more accurate is the resulting age.

Yet, for the clock to remain useful, the radioactive element must not decay too fast - there must still be enough left of it to allow an accurate measurement, even after several billion years.
Large amounts of these elements have been found in the star HE 1523-0901, an old, relatively bright star that was discovered within the Hamburg/ESO survey. The star was then observed with UVES on the Very Large Telescope (VLT) for a total of 7.5 hours.

For the first time, the age dating involved both radioactive elements in combination with the three other neutron-capture elements europium, osmium, and iridium. "Until now, it has not been possible to measure more than a single cosmic clock for a star. Now, however, we have managed to make six measurements in this one star"," says Frebel.

HE 1523-0901, estimated to be 13.2 billion years old was clearly formed very early in the life of our own Galaxy. Born at the dawn of time in the observable Universe, estimated to be 13.7 billion years old.

Nearby Star A Galactic Fossil ESO Press Release

This research is reported in a paper published in the 10 May issue of the Astrophysical Journal "Discovery of HE 1523-0901, a Strongly r-Process Enhanced Metal-Poor Star with Detected Uranium", by A. Frebel et al.

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Wednesday, May 09, 2007

First Stars

Artist impression of the first stars. Image credit: Hubble

An interesting look at how first stars may have formed in the early universe from Universe Today

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Monday, May 07, 2007

Brightest Supernova

U.S. astronomers say an exploding star first observed in September 06 has become the largest and most luminous supernova ever seen.

According to observations by NASA's Chandra X-ray Observatory and ground-based optical telescopes, the supernova SN 2006gy is the brightest and most energetic stellar explosion ever recorded and may be a long-sought new type of explosion.

The top panel of this graphic is an artist's illustration that shows what SN 2006gy may have looked like if viewed at a close distance. The fireworks-like material in white shows the explosion of an extremely massive star. This debris is pushing back two lobes of cool, red gas that were expelled in a large eruption from the star before it exploded. The green, blue and yellow regions in these lobes shows where gas is being heated in a shock front as the explosion material crashes into it and pushes it backwards. Most of the optical light generated by the supernova is thought to come from debris that has been heated by radioactivity, but some likely comes from the shocked gas.

The bottom left panel is an infrared image, using adaptive optics at the Lick Observatory, of NGC 1260, the galaxy containing SN 2006gy. The dimmer source to the lower left in that panel is the center of NGC 1260, while the much brighter source to the upper right is SN 2006gy.

The panel to the right shows Chandra's X-ray image of the same field of view, again showing the nucleus of NGC 1260 and SN 2006gy. The Chandra observation allowed astronomers to determine that SN 2006gy was indeed caused by the collapse of an extremely massive star, and not the most likely alternative explanation for the explosion, the destruction of a low-mass star. If the supernova was caused by a white dwarf star exploding into a dense, hydrogen-rich environment, SN 2006gy would have been about 1,000 times brighter in X-rays than what Chandra detected.

NASA's Chandra Sees Brightest Supernova Ever

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Saturday, May 05, 2007

COROT detects Oscillations

COROT discovers its first Exoplanet and detects oscillations in a Sun-like star

COROT has detected its first seismic oscillations in the light curve of a sun-like star. The research team for spacecraft COROT revealed the first discoveries of this major European mission on 3rd of May.

The satellite has also found a very hot exoplanet and provisional estimates indicate it has a very large radius.

Based on the quality of this initial data, our knowledge of planets outside our own solar system, known as exoplanets, and of the interiors of stars should be vastly improved over the next three years.

The exoplanet, which has been named COROT-exo-1b, orbits around a yellow dwarf star similar to our Sun in about 1.5 days. It is situated roughly 1500 light years from us, in the direction of the constellation of the Unicorn (Monoceros). The oscillating star is of a similar type and located in the same region of the sky, but much nearer to us.

The satellite has two main advantages over ground-based projects. Firstly, it can observe the same stars continuously, without interruption, for up 150 days (60 days so far). Secondly, its position above the Earth’s atmosphere enables it to measure the brightness variations of stars much more precisely.

COROT detects planets by looking for transits, small dips in the apparent brightness of a star caused by a planet passing in front of it. While its first planet is large, the quality of the data suggests COROT will be able to identify rocky planets only a few times larger than our own Earth.

COROT may also be able to observe variations in the amount of stellar light reflected towards us by planets as they go around their orbits, giving some indication of their atmospheric properties.
SciTech Press Release 3rd May 2007.

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SOHO & Sun Ripples

The Solar and Heliospheric Observatory (SOHO) may have glimpsed long-sought oscillations on the Sun’s surface.

The subtle variations reveal themselves as a miniscule ripple in the overall movement of the solar surface. Astronomers have been searching for ripples of this kind since the 1970s, when they first detected that the solar surface was oscillating in and out.

The so-called ‘g-modes’ are driven by gravity and provide information about the deep interior of the Sun. They are thought to occur when gas churning below the solar surface plunges even deeper into our star and collides with denser material, sending ripples propagating through the Sun’s interior and up to the surface. It is the equivalent of dropping a stone in a pond.

Unfortunately for observers, these waves are badly degraded during their passage to the solar surface. By the time g-modes reach the exterior, they are little more than ripples a few metres high.

Until now, the rotation rate of the solar core was uncertain. If the the Global Oscillation at Low Frequency (GOLF) - instrument on SOHO -detection is confirmed, it will show that the solar core is definitely rotating faster than the surface.

The rotation speed of the solar core is an important constraint for investigating how the entire Solar System formed, because it represents the hub of rotation for the interstellar cloud that eventually formed the Sun and all the bodies around it.

The next step for the team is to refine the data to increase their confidence in the detection, by incorporating data from other instruments, both on SOHO and at ground-based observatories.

SOHO's quest for solar ripples from ESA
A Massive Explosion on the Sun from NASA

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Photo courtesy of Pandabonium. Copyright @ Pacific Islander

Yabusame - ritual mounted archery
Yabusame was designed as a way to please and entertain the myriad of gods that watch over Japan, thus encouraging their blessings for the prosperity of the land, the people, and the harvest.

Animals are sacred in Shinto, acting as messengers between the gods and humans. The white horse represents purity and is believed to drive off evil spirits.

Click for more on May celebrations and archery competitions
from Pandabonium @ Yabusame & Rice Planting festival from Japan

Friday, May 04, 2007

Protostars in Cosmic Cloud

Click Image to Enlarge - Credit: NASA/JPL-Caltech/T. Bourke (CfA)

Two young stars are destroying their natal dust cloud with powerful jets of radiation, in an infrared image from NASA's Spitzer Space Telescope. The stars are located approximately 600 light-years away in a cosmic cloud called BHR 71.

The visible light image (left) was taken by the European Space Agency's ground-based Very Large Telescope. In this image BHR 71 is just a large black structure. The burst of yellow light toward the bottom of the cloud is the only indication that stars might be forming inside.

In the infrared image (middle), the baby stars are shown as the bright yellow smudges toward the center. Both of these yellow spots have wisps of green shooting out of them. The green wisps reveal the beginning of a jet. Like a rainbow, the jet begins as green, then transitions to orange, and red toward the end.

The jets' changing colors reveals a cooling effect, and may suggest that the young stars are spouting out radiation in regular bursts. The green tints at the beginning of the jet reveal really hot hydrogen gas, the orange shows warm gas, and the wisps of red at the end represent the coolest gas.

The fact that gas toward the beginning of the jet is hotter than gas near the middle, suggests that the stars must give off regular bursts of energy - and the material closest to the star is being heated by shockwaves from a recent stellar outburst. Meanwhile, the tints of orange reveal gas that is currently being heated by shockwaves from a previous stellar outburst. By the time these shockwaves reach the end of the jet, they have slowed down so significantly that the gas is only heated a little, and looks red.

The combined visible-light infrared composite (right) shows that a young star's powerful jet is responsible for the rupture at the bottom of the dense cloud in the visible-light image. We know this because the burst of light in the visible-light image overlaps exactly with a jet spouting out of the left star, shown in the infrared image.

The combination of views also brings out some striking details that evaded visible-light detection. For example, the yellow dots scattered throughout the image are actually young stars forming inside BHR 71. Spitzer also uncovered another young star with jets, located to the right of the powerful jet seen in the visible-light image.

Spitzer can see details, that visible-light telescopes don't, because its infrared instruments are sensitive to "heat."

The infrared image is made up of data from Spitzer's infrared array camera. Blue shows infrared light at 3.6 microns, green is light at 4.5 microns, and red is light at 8.0 microns.

CfA Press Release >>>
Spitzer Digs Up Hidden Stars

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Tuesday, May 01, 2007

Morning Star Ritual

The Pawnee paid very close attention to the movement of the universe, but they also felt that for the universe to continue functioning, the Pawnee people had to perform regular ceremonies.

The most important ceremony of the Pawnee culture, the Spring Awakening ceremony, which was meant to awaken the earth and ready it for planting, can be tied directly to the tracking of celestial bodies. “The position of the stars was an important guide to the time when this ceremony should be held. The earth lodge served as an astronomical observatory and as the priests sat inside at the west, they could observe the stars in certain positions through the smokehole and through the long east-oriented entranceway. They also kept careful watch of the horizon right after sunset and just before dawn to note the order and position of the stars.”

The ceremony must be held at exactly the right time of year, when the priest first tracked “two small twinkling stars known as the Swimming Ducks in the northeastern horizon near the Milky Way”. The ceremony was a recreation of the events that led to the creation of the world, the forced mating of Morning Star with Evening star.

Pawnee Mythology
Aztec Mythology - Windows on the Universe
Famous Quotes Who loves not women, wine and song
remains a fool his whole life long. -
Martin Luther

Please note the quote is in no way meant to offend or disrespect other Cultures, Traditions or Women. It simply means we should all know how to love - and love the good things life on Earth offers.
Wishing you all a bright sunny day and a fine Month of May!

Sombrero Galaxy M104

The Sombrero, also known as M104, is one of the largest galaxies in the nearby Virgo cluster, about 28 million light years from Earth. This Great Observatories view of the famous Sombrero galaxy was made using NASA's Chandra X-ray Observatory, Hubble Space Telescope and Spitzer Space Telescope. The main figure shows the combined image from the three telescopes, while the three inset images show the separate observatory views.

The Chandra X-ray image (in blue) shows hot gas in the galaxy and point sources that are a mixture of objects within the Sombrero as well as quasars in the background. The Chandra observations show that diffuse X-ray emission extends over 60,000 light years from the center of the Sombrero. (The galaxy itself spans 50,000 light years across.) Scientists think this extended X-ray glow may be the result of a wind from the galaxy, primarily being driven by supernovas that have exploded within its bulge and disk. The Hubble optical image (green) shows a bulge of starlight partially blocked by a rim of dust, as this spiral galaxy is being observed edge on. That same rim of dust appears bright in Spitzer's infrared image, which also reveals that Sombrero's central bulge of stars.

Chandra featured stories
If light travels the shortest distance between two points,
even if from the remotest parts of the observable universe
and all things being equal there is nothing between point A & B
what exactly would Carl Sagan et al have us tunneling thru
that would get us to point B from point A - faster than light.

Nova, It's String Theory - The Elegant Universe

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