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Dark Dust

This wide field image shows extensive dust and small clumps of star formation in part of the Taurus star formation region. A faint star at the centre of this picture is the young binary star system HK Tauri. ALMA observations of this system have provided the clearest picture ever of protoplanetary discs in a double star. The new result demonstrates one possible way to explain why so many exoplanets — unlike the planets in the Solar System — came to have strange, eccentric or inclined orbits. This picture was created from images from the Digitized Sky Survey 2

The Moon Is (Slightly) Flat:

Forty-five years after astronauts landed on the moon, scientists say they have finally discovered its true shape: slightly flattened, with a bulge on one side.

“Like a lemon with an equatorial bulge,” said Ian Garrick-Bethell, a planetary scientist at University of California, Santa Cruz, and an author of the study, being published in the journal Nature. “If you can imagine a water balloon flattening out as you spin it.”

Efforts to pinpoint the moon’s exact shape have long been stymied by the presence of large craters on its surface that formed after the crust solidified. There have also been inconsistencies between its measurements and what we know about its past.

For example, the moon barely spins, yet it appears to have the sort of equatorial bulge caused by rotation. And why would a giant ball of cooled liquid be anything but spherical?

“There’s no plate tectonics like on the earth,” Dr. Garrick-Bethell said. “Why is it so deformed?”

To overcome the crater problem, he and his colleagues used highly accurate maps of the moon’s topography, made with a laser altimeter, then ran calculations to see what the surface could have looked like before the craters formed.

The measurements that emerged help explain how the moon acquired its shape, the researchers say. Its squashed appearance is probably a result of the gravitational process called tidal heating or acceleration, which stretched the moon’s crust as it was being formed. The equatorial bulge probably dates to a later period, when the moon was still spinning but was slowing down and moving away from earth, freezing a tidal surge in place.

The clues, Dr. Garrick-Bethell said, are all in the math.

“There is an expected ratio you get for each of those two tidal processes,” he said. “We found the exact ratios you would expect for each process.”

(Source: The New York Times)

Artist's impression of the misaligned protoplanetary disks around the binary stars in HK Tau. Credit: R. Hurt (NASA/JPL-Caltech/IPAC)

Artist’s impression of the misaligned protoplanetary disks around the binary stars in HK Tau. Credit: R. Hurt (NASA/JPL-Caltech/IPAC)

Astronomers have contemplated planets forming in single flat disks, as in our own solar system, for decades. Misaligned planet disks in a binary star system? Weird! But now they’ve found the best example so far, in the course of conducting a survey of binary stars with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. The young binary star system is called HK Tau. It consists of two stars orbiting a common center of mass. In a system like this, you might imagine any planet-forming disks to be surrounding the two stars, in the same plane as their orbits around each other. But that’s not the case here. In this system, the disks are misaligned – they’re out of sync with the mutual orbit of their host stars – by as much as 60 degrees or more.

And as a result, said astronomer Eric Jensen of Swarthmore College in Pennsylvania:

… we may be seeing the formation of a solar system that may never settle down.

Stars and planets form out of great clouds of dust and gas in space. As material in these clouds contracts under gravity, it begins to rotate. Eventually, most of the dust and gas falls into a flat disk swirling around the central protostar. It’s from these protoplanetary disks that planets like our own Earth are thought to form.

Astronomers say that studying the disks of the two stars in the HK Tau system will help us understand our own solar system’s formation better. Their next step, the researchers say, is to determine if this type of system is typical or not. They note that this is a remarkable individual case, but additional surveys are needed to determine if this sort of arrangement is common throughout our Milky Way galaxy.

The two stars in this system are located approximately 450 light-years from Earth in the direction of our constellation Taurus. The two stars are separated by about 58 billion kilometers, or 13 times the distance of Neptune from our sun.

They are less than 5 million years old, in contrast to some four-and-a-half billion years for our sun.

Rachel Akeson of the NASA Exoplanet Science Institute at the California Institute of Technology in Pasadena, California said:

This clear misalignment has given us a remarkable look at a young binary star system. Though there have been hints before that this type of misaligned system exists, this is the cleanest and most striking example.

Read more about the misaligned disks in the HK Tau system, from NRAO.

(Source: earthsky.org)

Our Milky Way galaxy is less massive than astronomers previously thought, according to new research.

For the first time, scientists have been able to precisely measure the mass of the galaxy that contains our solar system. A team led by researchers have found that the Milky Way is approximately half the mass of a neighboring galaxy – known as Andromeda – which has a similar structure to our own.

The Milky Way and Andromeda are the two largest members of a cluster of galaxies which astronomers call the Local Group. Both galaxies have a spiral shape and appear to be of similar dimensions, but until now scientists had been unable to prove which is most massive as previous studies were only able to measure the mass enclosed within both galaxies’ inner regions.

The scientists used recently published data on the known distances between galaxies – as well as their velocities – to calculate the total masses of Andromeda and the Milky Way.

Revealing this for both galaxies, they also found that so-called ‘dark’ matter makes up 90% of the matter in both systems.

Dark matter is a little understood invisible substance which makes up most of the outer regions of galaxies and around 27% of the content of the universe. The researchers estimate that Andromeda contains twice as much dark matter as the Milky Way, causing it to be about twice as massive in total. Their work should help astronomers learn more about how the outer regions of galaxies are structured.

The results were published on July 29 in the journal Monthly Notices of the Royal Astronomical Society.

Read more from the Royal Astronomical Society

(Source: earthsky.org)

"Rebooted" Satellite Loses Thruster Capability:

An ambitious plan to revive a forsaken NASA satellite and return it to Earth orbit ended in disappointment Wednesday when engineers conceded that a failure in the spacecraft’s propulsion system made it impossible to fire thrusters and alter the probe’s flight path.

"There’s only so much you can do before you have to say, ‘It’s dead, Jim,’ " said Keith Cowing, a former NASA astrobiologist and a spokesman for the privately-run ISEE-3 Reboot Project, which operates out of a converted McDonald’s restaurant at NASA’s Ames Research Center in Mountain View, Calif.

Related story:Mechanical 'hiccups' complicate satellite reboot mission

Unable to nudge the aging probe from its orbit around the sun, project engineers say they have switched the spacecraft to “science mode” and will collect data from it for as long as they can — perhaps a couple of months.

NASA launched the International Sun-Earth Explorer 3 in 1978 to study space weather and retired it 17 years ago. As the spacecraft neared Earth on a pre-arranged flyby set for Aug. 10, Cowing and others won permission to take control of the craft, the first time NASA has ever handed over one of its assets to a private group.

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In just three months, the team of former NASA employees, engineers and self-described space cowboys managed to raise $160,000 on crowd-funding websites; wake the probe from an electronic slumber; communicate with it using the massive radio telescope in Arecibo, Puerto Rico; and fire several of its engines.

But the thrusters stopped working Tuesday, just as the team prepared to maneuver the spacecraft into a new orbital path.

On Wednesday, members of the ISEE-3 Reboot Project spent two hours attempting to diagnose the problem by “jiggling” fuel valves on and off. When the thrusters still failed to work, the disappointed engineers concluded that the satellite’s fuel system had lost critical pressure.

"We have exhaustively tested the propulsion system with no good results," project member Dennis Wingo, the chief executive of Skycorp Inc., reported on Twitter.

I’ll know where it is in the sky and at what time, and I’m just going to look up and wave goodbye to my old friend.- Bob Farquhar, member of the ISEE-2 Reboot Project

The satellite, like many others, uses hydrazine fuel. The highly toxic substance is stored in eight tanks and kept under pressure by nitrogen gas. When ground controllers instruct the satellite to open a fuel valve, the gas is supposed to push the hydrazine through fuel lines and into a catalyst. When it reaches the catalyst, the hydrazine should break down and produce an invisible puff of hot gas that propels the spacecraft.

Reboot engineers calculated that it would take about 432 puffs of gas to redirect the spacecraft into Earth orbit. But without fuel pressure, the thrusters will not fire.

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Cowing said it was possible there was a minute leak that allowed the gas to escape slowly — maybe even a molecule at a time — over decades. “There may still be some stuff in there; it’s just not enough,” he said.

The thruster firings that did occur were probably the result of residual gas pressure in the fuel lines, he said.

Since ground controllers were able to fire the thrusters initially, the satellite’s flight path has been slightly changed, and there’s a small chance that it may be on a collision course with the moon.

A lunar collision, they noted, would provide scientists with more data than they would collect in a normal flyby.

Related story: Space monkeys: The humanizing of Able and Baker

Reboot project engineers hope to determine the spacecraft’s exact location and new trajectory on Friday, when they will have access to NASA’s Deep Space Network, its powerful telecommunications system.

The propulsion system failure surprised one of the chief architects of the satellite’s orbital path, Bob Farquhar. The former NASA engineer helped send the satellite into space 36 years ago and charted a complex course that allowed it to become the first spacecraft ever to pass through a comet’s tail.

Farquhar was among the engineers working on the reboot project, and although he was highly skeptical they would pull it off, he said he never anticipated an equipment malfunction.

"I always thought the spacecraft would work OK," Farquhar said. "I can’t understand why all the nitrogen would be gone."

The 82-year-old had lobbied NASA for years to reactivate the satellite. He often said he had a supernatural connection to the spacecraft — a belief he developed when he suffered a heart attack at almost the same time ISEE-3 lost function of its only battery.

"I feel deflated," Farquhar joked Wednesday. "I think I’m losing pressure in my lungs."

Despite the failure, Farquhar said he planned to mark the spacecraft’s flyby next month.

"I’ll know where it is in the sky and at what time, and I’m just going to look up and wave goodbye to my old friend," he said.

Found: Most Distant Stars In The Milky Way Galaxy:

Astronomers have discovered the farthest-flung stars yet known in the Milky Way.

The two objects — known as ULAS J0744+25 and ULAS J0015+01 — are about 775,000 and 900,000 light-years from Earth, respectively, making them both about five times more distant than a satellite galaxy known as the Large Magellanic Cloud.

"The distances to these two stars are almost too large to comprehend," study lead author John Bochanski, of Haverford College in Pennsylvania, said in a statement. "To put it in perspective, when the light from ULAS J0015+01 left the star, our early human ancestors were just starting to make fires here on Earth."

The Milky Way extends far beyond its familiar disk, which is just 100,000 light-years or so wide. The galaxy is surrounded by a sparse “halo” of stars — perhaps stragglers left out there after the Milky Way’s many mergers with dwarf galaxies over the eons, researchers say.

Scientists know this halo extends to at least 500,000 light-years away, but its exact dimensions are unknown. Bochanski and his colleagues decided to probe the halo’s outer reaches, hunting for a type of star called cool red giants.

Distant Milky Way Star Uniview by SCISS Data: SOHO (ESA & NASA), John Bochanski (Haverford College) and Jackie Faherty (American Museum of Natural History and Carnegie Institute’s Department of Terrestrial Magnetism)

This simulated image demonstrates how small the Milky Way would look from the location of ULAS J0744+25, nearly 775,000 light-years away. 

Cool red giants are much rarer than red dwarfs, which make up about 70 percent of the Milky Way’s stars. But they’re about 10,000 times brighter, making them much easier to see from a distance.

"It really is like looking for a needle in a haystack," Bochanski said. "Except our haystack is made up of millions of red dwarf stars."

Astronomers watching a supernova may have found out where the dust that makes up much of the Universe came from.

Cosmic dust is crucial to the birth of stars and rocky planets, and provides the elemental ingredients for life. But its origin is obscure. Many astrophysicists think that dust is forged during the explosive supernova deaths of massive, short-lived stars, yet some observations of supernovas near our galaxy indicate that they produce too little material to account for the copious amounts of dust present in the young Universe.

In Nature today, astronomers lift the veil on the mystery, documenting the formation of dust in a supernova from just a few weeks after the explosion to almost 2.5 years after it. The study reveals the formation of oversized dust grains that were able to withstand the shocks of the exploding star. It also shows that dust production was slow at first, but later sped up.

Most previous studies looked at each supernova for short periods of time, so “they did not tell us the full story of how much dust supernovas produce”, says co-author Christa Gall, an astrophysicist at Aarhus University in Denmark. She and her colleagues monitored the supernova SN 2010jl, first spotted in a nearby galaxy in 2010.

Light and heat

Using a spectrograph on the Very Large Telescope on Cerro Paranal in Chile, the team measured the amount of visible light absorbed by the dust particles and the infrared radiation that the particles themselves emitted.

The team’s data are particularly compelling because they provide this simultaneous coverage at a range of wavelengths from weeks to years after the explosion, says astronomer Rubina Kotak of Queen’s University Belfast, UK. This provides information about both the size and the composition of the grains.

Such coverage “is difficult to obtain for all but the nearest and brightest supernova events”, she says.

The team concluded that the dust present between 40 and 240 days after the explosion must have been made of material expelled before the star went supernova, because the only other possibility would be the debris hurled into interstellar space by the supernova itself. And this is too hot to condense into dust particles so soon after the explosion, Gall notes. As the expanding shock wave from the supernova swept by in this period after the explosion, it compressed the previously ejected material into a cold, dense shell — the perfect environment for dust to coalesce and grow.

Resistant to shockwaves

To their surprise, the astronomers found that the dust particles were enormous by Milky Way standards, measuring 1 to 4.2 micrometres across — at least four times the typical width of dust particles found between star systems in our home Galaxy. It is harder to form large dust particles, notes Gall, but their size makes them resistant to destruction by shocks associated with the supernova slamming into interstellar material, and probably accounts for their longevity. Large interstellar dust grains have previously been found in our Solar System.

During early observations, the amount of dust around SN 2010jl was relatively small, equivalent to less than one-ten-thousandth the mass of the Sun. But between 500 and 868 days after the explosion, dust formation accelerated and the dust mass increased more than 10-fold.

The revved-up rate marks a transition to a second phase in supernova dust production, says Gall. Once carbon-rich material and other debris generated during the supernova has cooled sufficiently, it begins to coalesce into dust, speeding up production. At day 868, the last time Gall’s team observed the supernova, the amount of dust had increased to 0.04 of the Sun’s mass, or 830 Earth masses.

If the increased dust production continues, in 20 years SN 2010jl will have produced the equivalent of half the Sun’s mass in dust particles, similar to the amount observed in the widely observed supernova SN 1987A. If numerous supernovae early in the Universe produced dust at a similar rate, it could indeed account for the dust observed in the young cosmos, says Gall.

(Source: The Huffington Post)

The Awesome Beauty Of M16, The Eagle Nebula:

The Eagle Nebula, also known as Messier 16 or M16, consists of a star cluster and many emission nebulae and dark nebulae, in the direction of the constellation Serpens. It’s the location of several famous structures including the Pillars of Creation, whose photo you see in this post. Take a look at the photos here, and delve deeper into this region of space, which is one of the most interesting and beautiful we know.

View larger. | Behold the awesome beauty of

View larger. | Behold the awesome beauty of the Eagle Nebula, aka M16. Photo by Martin MacPhee.

Chart showing location of M16, or Eagle Nebula, via Tammy Plotner and Universe Today.

If you can find the famous Teapot asterism of the constellation Sagittarius, look for the Eagle Nebula, or M16, just a bit above and to the left of it, as viewed from a N. Hemisphere location. Chart via Tammy Plotner and Universe Today.

In the late 18th century, when this object began to be catalogued by astronomers, only the star cluster could be seen, and this was designated as M16 in Messier’s catalog of things not to be confused with comets. Later, this star cluster became known as the Snow Queen Cluster.

The advent of astrophotography revealed a large area of glowing hydrogen gas that was invisible to the unaided eye, and that looked somewhat like an eagle with outstretched wings, giving rise to the current common name of Eagle Nebula.

As higher resolution photography and then digital photography began to reveal more and more features, particularly the dark patches (aka dark nebulae), many distinct features within the Eagle Nebula were given individual names. Today, the informal name of the Eagle Nebula is taken as referring to all of these in one collective designation. Some of them are famous, and all are beautiful.

This is a 1995 photo of what has come to be called The Pillars of Creation.  It's located within the Eagle Nebula.

This is a 1995 Hubble photo of the Pillars of Creation. It’s one of the most famous photos ever taken by the Hubble Space Telescope. This feature is located within the Eagle Nebula.

View larger. | The Eagle Nebula suddenly burst upon the World's collective consciousness in 1995, when the Hubble telescope focused its attention on the dark nebula in the center of the Eagle, which you can see in this view. The dark protrusions of dense gas were found to be the site of new star and solar system formation, and the resulting photograph became known as

View larger. | A closer look at the Eagle Nebula. Photo by Martin MacPhee.

The Eagle Nebula suddenly burst upon the world’s collective consciousness in 1995, when the Hubble Space Telescope focused its attention on a dark nebula in the center of the Eagle, which you can see in the photos above and below.

The dark protrusions of dense gas were found to be the site of new star and solar system formation, and the resulting photograph became known as the Pillars of Creation and gave most people their first view of new stars and solar systems at the dawn of their creation.

Similar areas, such as the Stellar Spire on the left side of the Eagle, are also forming new stars, through a combination of processes. The cold, mostly hydrogen, gas of the nebula has already fueled the formation of a series of young, hot stars. As the gas continues to collapse under its own gravity into the dark forms we see, new stars and solar systems are formed and continue to grow as they attract more and more gas to them. However, the intense light pressure from the new stars that have formed and their solar winds are eroding away the dense, cold gas pockets, diminishing new star formation and dispersing the nebulae.

At the same time however, the shock waves where the light and solar wind impacts the cold gas, heat and compress some of the cold gasses at the same time, resulting in a new set of star forming environments

View larger. | Here is a labelled map showing both the

View larger. | Labelled map showing both the Pillars of Creation and the Stellar Spire, within the Eagle Nebula. Photo and labels by Martin MacPhee.

I am very pleased I can see these structures in my ‘scope, which is only 8″ in diameter, especially given that they are located around 7,000 light-years away, and the Stellar Spire is roughly 9.5 light-years (~ 9 trillion kilometers) tall – about twice the diameter of our solar system. In seeing them from my driveway in the heavily light-polluted Maryland suburbs of Washington D.C., I’m doing very well. And for approximately $10,000,000,000 less than the Hubble telescope cost, which makes my wife very happy too!

Enjoy the view while you can. Sadly, data from other telescopes has shown that the Pillars and Spire are likely already gone, victims of a massive shock wave from a supernova explosion that happened 8,000 to 9,000 years ago. Its light has already gone past us, but the slower-moving shock waves would have taken thousands of years more to sweep through the Eagle Nebula, destroying the delicate structures we find so entrancing.

The light of that destruction is already on its way to us, so in a few thousand years, people will be seeing a very different Eagle in the ever-changing sky.

Stellar Spire, also located in the Eagle Nebula, as seen by the Hubble Space Telescope.

Stellar Spire, also located in the Eagle Nebula, as seen by the Hubble Space Telescope.

Bottom line: What we know today as the Eagle Nebula, or M16, once was thought to be a simple star cluster. Astrophotography revealed the structure that resembled an eagle and gave the Nebula its current name. The Hubble Space Telescope revealed even more detail, so that today the Eagle Nebula is known as home to at least two famous structures: the Stellar Spire and the Pillars of Creation.

(Source: earthsky.org)

Big Pic:  A Portrait Of Saturns Best Features:

Like a photo of the New York City skyline with both the Empire State and Chrysler buildings in view, this image of Saturn shows off its most iconic landmarks. There’s the hexagon-shaped jet stream feature at its north pole, plus its rings. The spacecraft Cassini took this image on April 2.

Cassini recently celebrated the tenth anniversary of its arrival at Saturn. Now, its engineers are looking toward its final missions. In 2015, NASA plans to send Cassini to sample the water geysering out of Saturn’s moon Enceladus. This will be humanity’s first and only sample of that alien water. Then, in late 2016, Cassini will begin a series of 22 orbits around Saturn that will send the spacecraft between Saturn’s upper atmosphere and its innermost rings. Such close encounters with the planet will help scientists measure Saturn’s magnetic field and the mass of Saturn’s rings—another first.

illustration showing the orbits NASA plans for Cassini in its Grand Finale mission
The 22 orbits Cassini will make around Saturn in its final mission
NASA/JPL-Caltech

Finally, Cassini will plunge into Saturn’s atmosphere to avoid contaminating the planet’s moons, which scientists think may harbor alien life.

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