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Posts tagged "astrophysics"

afro-dominicano:

World’s Biggest Laser Blasts Diamond to Simulate Planet Cores

The biggest laser in the world was used to crush a diamond, offering insights into how the hardest known material behaves when it is exposed to extremely high pressures. The experiment could also reveal new clues about what happens at the cores of giant planets, where conditions of intense atmospheric pressures exist.

Researchers at the Lawrence Livermore National Laboratory in Livermore, California, led by physicist Raymond Smith, blasted a sliver of diamond with a laser beam at a pressure of 725 million pounds per square inch (51 million kilograms per square centimeter). This is the kind of pressure found near the core of giant planets, such as Jupiter or huge, rocky bodies known as “super-Earths.”

The entire experiment took only 25 billionths of a second. The researchers fired 176 laser beams at a small cylinder of gold, called a hohlraum, with a tiny chip of synthetic diamond embedded in it. When the laser beams hit the cylinder, the energy was converted to X-rays. The hohlraum was vaporized, and in the process, the diamond was exposed to pressures tens of millions of times Earth’s atmospheric pressure.

Theoretical calculations predicted that such high pressures should cause a diamond to change its crystal structure. One way to test if this is true is to measure the speed of sound waves in a material. If this speed changes abruptly as the pressure goes up, then the diamond structure has rearranged itself.

But that didn’t happen — the velocity of sound waves changed smoothly.

"If there was a phase transformation you’d expect a discontinuity," Smith said.

The rate of change in the diamond’s density also didn’t match up with earlier theoretical models. Materials typically become denser at high pressures, and diamond is no exception. But how fast its density changed was a surprise, the researchers said.

The experiment was a breakthrough, in that instead of smacking the diamond with high pressure in a stepwise fashion, such as hitting it with successively heavier hammers, the researchers were able to boost the pressure smoothly. This enabled them to crush the diamond and expose it to intense pressure without the substance becoming too hot and melting. (Diamonds can and do melt at sufficiently high temperatures).

Since diamonds are made of carbon, understanding how this material behaves at high pressures can be important in the study of planets around other stars, said Nikku (Madhu) Madhusudhan, a professor of astrophysics at the University of Cambridge.

spaceplasma:

Spectroscopy and the Birth of Astrophysics

The 3D animation (above) depicts how the light of a distant star is studied by astronomers. The spectrum of the light provides vital information about the composition and history of stars. Now, let’s look into the history of stellar spectroscopy.

In 1802, William Wollaston noted that the spectrum of sunlight did not appear to be a continuous band of colours, but rather had a series of dark lines superimposed on it. Wollaston attributed the lines to natural boundaries between colours. Joseph Fraunhofer made a more careful set of observations of the solar spectrum in 1814 and found some 600 dark lines, and he specifically measured the wavelength of 324 of them. Many of the Fraunhofer lines in the solar spectrum retain the notations he created to designate them. In 1864, Sir William Huggins matched some of these dark lines in spectra from other stars with terrestrial substances, demonstrating that stars are made of the same materials of everyday material rather than exotic substances. This paved the way for modern spectroscopy.

Since even before the discovery of spectra, scientists had tried to find ways to categorize stars. By observing spectra, astronomers realized that large numbers of stars exhibit a small number of distinct patterns in their spectral lines. Classification by spectral features quickly proved to be a powerful tool for understanding stars.

The current spectral classification scheme was developed at Harvard Observatory in the early 20th century. Work was begun by Henry Draper who photographed the first spectrum of Vega in 1872. After his death, his wife donated the equipment and a sum of money to the Observatory to continue his work. The bulk of the classification work was done by Annie Jump Cannon from 1918 to 1924. The original scheme used capital letters running alphabetically, but subsequent revisions have reduced this as stellar evolution and typing has become better understood.

While the differences in spectra might seem to indicate different chemical compositions, in almost all instances, it actually reflects different surface temperatures. With some exceptions (e.g. the R, N, and S stellar types), material on the surface of stars is “primitive”: there is no significant chemical or nuclear processing of the gaseous outer envelope of a star once it has formed. Fusion at the core of the star results in fundamental compositional changes, but material does not generally mix between the visible surface of the star and its core. Ordered from highest temperature to lowest, the seven main stellar types are O, B, A, F, G, K, and M. Astronomers use one of several mnemonics to remember the order of the classification scheme. O, B, and A type stars are often referred to as early spectral types, while cool stars (G, K, and M) are known as late type stars.

Scientists assumed that the spectral classes represented a sequence of decreasing surface temperatures of the stars, but no one was able to demonstrate this quantitatively. Cecilia Payne, who studied the new science of quantum physics, knew that the pattern of features in the spectrum of any atom was determined by the configuration of its electrons. She showed that Cannon’s ordering of the stellar spectral classes was indeed a sequence of decreasing temperatures and she was able to calculate the temperatures.

  • More information: here

Credit: ESO, Jesse S. Allen

afro-dominicano:

Markarian’s Chain: M84, M86, M87 in Virgo byMakis Palaiologou, Stefan Binnewies and Josef Pöpsel

Markarian’s Chain is a stretch of galaxies that forms part of the Virgo Cluster. It is called a chain because, when viewed from Earth, the galaxies lie along a smoothly curved line. It was named after the Armenian astrophysicist, B. E.

Ancient Asteroid Destroyer Finally Found, And It’s a New Kind of Meteorite

For 50 years, scientists have wondered what annihilated the ancestor of L-chondrites, the roof-smashing, head-bonking meteorites that frequently pummel Earth.

Image: Credit:

Now, a new kind of meteorite discovered in a southern Sweden limestone quarry may finally solve the mystery, scientists report. The strange new rock may be the missing “other half” from one of the biggest interstellar collisions in a billion years.

"Something we didn’t really know about before was flying around and crashed into the L-chondrites," said study co-author Gary Huss of the University of Hawaii at Manoa.

The space rock is a 470-million-year-old fossil meteorite first spotted three years ago by workers at Sweden’s Thorsberg quarry, where stonecutters have an expert eye for extraterrestrial objects. Quarriers have plucked 101 fossil meteorites from the pit’s ancient pink limestone in the last two decades.

Mysterious find

Geochemically, the meteorite falls into a class called the primitive achondrites, and most resembles a rare group of achondrites called the winonaites. But small differences in certain elements in its chromite grains set the mysterious object apart from the winonaites, and its texture and exposure age distinguish the new meteorite from the other 49,000 or so meteorites found so far on Earth.

"It’s a very, very strange and unusual find," Schmitz told Live Science’s Our Amazing Planet.

The new meteorite was recently reported online in the journal Earth and Planetary Science Letters, and the study will appear in the journal’s Aug. 15 print edition.

(via afro-dominicano)

afro-dominicano:

'Cosmos' Finale Brings a (Big) Bang of Wonder

For astrophysicist Neil deGrasse Tyson, the scientific exploration of our universe is one amazing voyage, and so too has been his run on the new “Cosmos.”

As host of Fox’s science-themed “Cosmos: A Spacetime Odyssey,” Tyson has carried readers back and forth through time, revisited scientists during pivotal discoveries and introduced a new generation to the wonder of space and science. The show debuted in March and airs its 13th and final episode tonight (June 8).

"We end on a note where yes, this is a journey. It’s a look at how far it’s come, look at how much further it can go," Tyson told reporters Friday. “It’s our solar curiosity, if you will, that will keep that pumped. Without it, I don’t know that the country or the world or culture or civilization can go anywhere.”

"Cosmos: A Spacetime Odyssey" is a 21st-century reboot of the iconic 1980 PBS series "Cosmos: A Personal Journey" hosted by the famed astronomer popularizer of science Carl Sagan, who died in 1996. Like that original series, the new show is led by Ann Druyan, Sagan’s widow and longtime partner, who serves as co-writer and executive producer.

But there has been one major difference. This new “Cosmos” has been big. Unlike the 1980 series, which aired on public television, the new “Cosmos” aired Sunday nights on Fox, then again on Monday nights on the National Geographic Channel. The series was beamed out to 181 countries and launched with a tie-in app for mobile devices and well as a vigorous social media campaign.

"I have a feeling that the reaction to the series has exceeded my wildest fantasies," Druyan told Space.com Friday during a conference call. She added that she was stunned last Sunday (June 1), when "Cosmos" came in neck and neck with "The Bachelorette," nearly win the night in ratings with an episode about global warming on Earth.

"I have a feeling of just tremendous satisfaction that Fox and Nat Geo were brave enough to put this show on primetime, which hasn’t happened on a commercial broadcast network such as Fox in recent memory," Druyan said.

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afro-dominicano:

Grand Swirls

This new Hubble image shows NGC 1566, a beautiful galaxy located approximately 40 million light-years away in the constellation of Dorado (The Dolphinfish).

NGC 1566 is an intermediate spiral galaxy, meaning that while it does not have a well defined bar-shaped region of stars at its centre — like barred spirals — it is not quite an unbarred spiral either (heic9902o).

The small but extremely bright nucleus of NGC 1566 is clearly visible in this image, a telltale sign of its membership of the Seyfert class of galaxies.

The centres of such galaxies are very active and luminous, emitting strong bursts of radiation and potentially harbouring supermassive black holes that are many millions of times the mass of the Sun.

NGC 1566 is not just any Seyfert galaxy; it is the second brightest Seyfert galaxy known. It is also the brightest and most dominant member of the Dorado Group, a loose concentration of galaxies that together comprise one of the richest galaxy groups of the southern hemisphere. This image highlights the beauty and awe-inspiring nature of this unique galaxy group, with NGC 1566 glittering and glowing, its bright nucleus framed by swirling and symmetrical lavender arms.

afro-dominicano:

Chandra Helps Explain “Red and Dead Galaxies”

NASA’s Chandra X-ray Observatory has shed new light on the mystery of why giant elliptical galaxies have few, if any, young stars. This new evidence highlights the important role that supermassive black holes play in the evolution of their host galaxies.

Because star-forming activity in many giant elliptical galaxies has shut down to very low levels, these galaxies mostly house long-lived stars with low masses and red optical colors. Astronomers have therefore called these galaxies “red and dead”.

Previously it was thought that these red and dead galaxies do not contain large amounts of cold gas - the fuel for star formation - helping to explain the lack of young stars. However, astronomers have used ESA’s Herschel Space Observatory to find surprisingly large amounts of cold gas in some giant elliptical galaxies. In a sample of eight galaxies, six contain large reservoirs of cold gas. This is the first time that astronomers have seen large quantities of cold gas in giant elliptical galaxies that are not located at the center of a massive galaxy cluster.

kenobi-wan-obi:

Magnetar Formation Mystery Solved?

Magnetars are the bizarre super-dense remnants of supernova explosions.

They are the strongest magnets known in the Universe — millions of times more powerful than the strongest magnets on Earth. A team of European astronomers using ESO’s Very Large Telescope (VLT) now believe they’ve found the partner star of a magnetar for the first time.

This discovery helps to explain how magnetars form — a conundrum dating back 35 years — and why this particular star didn’t collapse into a black hole as astronomers would expect.

When a massive star collapses under its own gravity during a supernova explosion it forms either a neutron star or black hole. Magnetars are an unusual and very exotic form of neutron star.

Like all of these strange objects they are tiny and extraordinarily dense — a teaspoon of neutron star material would have a mass of about a billion tonnes — but they also have extremely powerful magnetic fields. Magnetar surfaces release vast quantities of gamma rays when they undergo a sudden adjustment known as a starquake as a result of the huge stresses in their crusts.

The Westerlund 1 star cluster, located 16 000 light-years away in the southern constellation of Ara (the Altar), hosts one of the two dozen magnetars known in the Milky Way. It is called CXOU J164710.2-455216 and it has greatly puzzled astronomers.

“In our earlier work (eso1034) we showed that the magnetar in the cluster Westerlund 1 (eso0510) must have been born in the explosive death of a star about 40 times as massive as the Sun.

But this presents its own problem, since stars this massive are expected to collapse to form black holes after their deaths, not neutron stars. We did not understand how it could have become a magnetar,” says Simon Clark, lead author of the paper reporting these results.

Astronomers proposed a solution to this mystery. They suggested that the magnetar formed through the interactions of two very massive stars orbiting one another in a binary system so compact that it would fit within the orbit of the Earth around the Sun.

But, up to now, no companion star was detected at the location of the magnetar in Westerlund 1, so astronomers used the VLT to search for it in other parts of the cluster. They hunted for runaway stars — objects escaping the cluster at high velocities — that might have been kicked out of orbit by the supernova explosion that formed the magnetar. One star, known as Westerlund 1-5, was found to be doing just that.

(via afro-dominicano)

kenobi-wan-obi:

A Star Cluster in the Wake of Carina

This colourful new image from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile shows the star cluster NGC 3590.

These stars shine brightly in front of a dramatic landscape of dark patches of dust and richly hued clouds of glowing gas. This small stellar gathering gives astronomers clues about how these stars form and evolve — as well as giving hints about the structure of our galaxy’s pinwheeling arms.

NGC 3590 is a small open cluster of stars around 7500 light-years from Earth, in the constellation of Carina (The Keel). It is a gathering of dozens of stars loosely bound together by gravity and is roughly 35 million years old.

This cluster is not just pretty; it is very useful to astronomers. By studying this particular cluster — and others nearby — astronomers can explore the properties of the spiral disc of our galaxy, the Milky Way.

NGC 3590 is located in the largest single segment of a spiral arm that can be seen from our position in the galaxy: the Carina spiral feature.

(via afro-dominicano)

thenewenlightenmentage:

Starshade Could Help Photograph Distant Planets

As a planet orbits near its sun, the bright stellar light interferes with observations made from Earth. To block the excess light, NASA scientists want to launch into space a large instrument called a starshade that will allow a space telescope to directly image an Earth-sized planet in an Earth-like orbit.

“A starshade removes most of the starlight by blocking it outside the telescope. It creates a shadow much like the Moon does during a solar eclipse,” said Jeremy Kasdin of Princeton University in an email.

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kenobi-wan-obi:

Starbursts In The Wake Of A Fleeting Romance

This image shows galaxy NGC 4485 in the constellation of Canes Venatici (The Hunting Dogs). The galaxy is irregular in shape, but it hasn’t always been so. Part of NGC 4485 has been dragged towards a second galaxy, named NGC 4490 — which lies out of frame to the bottom right of this image.

Between them, these two galaxies make up a galaxy pair called Arp 269. Their interactions have warped them both, turning them from spiral galaxies into irregular ones. NGC 4485 is the smaller galaxy in this pair, which provides a fantastic real-world example for astronomers to compare to their computer models of galactic collisions. The most intense interaction between these two galaxies is all but over; they have made their closest approach and are now separating. The trail of bright stars and knotty orange clumps that we see here extending out from NGC 4485 is all that connects them — a trail that spans some 24 000 light-years.

Many of the stars in this connecting trail could never have existed without the galaxies’ fleeting romance. When galaxies interact hydrogen gas is shared between them, triggering intense bursts of star formation. The orange knots of light in this image are examples of such regions, clouded with gas and dust.

(via afro-dominicano)

kenobi-wan-obi:

Could Tiny ‘Black Hole Atoms’ Be Elusive Dark Matter?

Dark matter, the invisible and mysterious stuff that makes up most of the material universe, might be hiding itself in microscopic black holes, says a team of Russian astrophysicists.

No one knows what dark matter is. But scientists do know that it must exist, because there is not enough visible matter in the cosmos to account for all the gravity that binds galaxies and other large-scale structures together.

Astronomers have been on the hunt for dark matter for decades now, using detectors both on Earth and in space. The new hypothesis, formulated by astrophysicists Vyacheslav Dokuchaev and Yury Eroshenko at the Institute for Nuclear Research of the Russian Academy of Sciences in Moscow, suggests that dark matter could be made of microscopic — or quantum — “black hole atoms.”

The concept is not entirely new; others have suggested that various types of miniature black holes could make up dark matter, which is so named because it apparently neither absorbs nor emits light, and thus cannot be detected directly by telescopes.

Physicists have also long believed that microscopic black holes must have existed in the early universe, because quantum fluctuations in the density of matter just after the Big Bang would have created regions of space dense enough to allow the formation of such tiny black holes.

Some researchers believe that the universe could still be full of such “primordial black holes.”

ohstarstuff:

MODEL UNIVERSE RECREATES EVOLUTION OF THE COSMOS

Astronomers have created the first realistic virtual universe using a computer simulation called “Illustris.” Illustris can recreate 13 billion years of cosmic evolution in a cube 350 million light-years on a side with unprecedented resolution.

The computer simulation began a mere 12 million years after the Big Bang. When it reached the present day, astronomers counted more than 41,000 galaxies in the cube of simulated space. 

The model requires a huge amount of computing power: running it on even a state-of-the-art desktop computer would take almost 2,000 years. Even run across more than 8,000 processors, the simulation still took several months.

VIDEO SIMULATION


CREDIT:
http://www.illustris-project.org/
http://www.cfa.harvard.edu/news/2014-10
http://www.nature.com/news/model-universe-recreates-evolution-of-the-cosmos-1.15178

(via afro-dominicano)

kenobi-wan-obi:

NOAO Presents New View of Messier 8

This image was obtained with the wide-field view of the Mosaic camera on the KPNO 0.9m-meter telescope at Kitt Peak National Observatory.

M8 is a giant star forming region. It is so big that it is faintly visible to the naked eye. The gas in the nebula is energized by a massive star at its center, causing the gas to glow.

The dark objects within the nebula are called Bok globules, and are dense clouds of gas in which new stars are forming. The image was generated with observations in Hydrogen alpha (red), Oxygen [OIII] (green) and Sulfur [SII] (blue) filters.

In this image, North is left, East is down.

kenobi-wan-obi:

The Changing Colors of the Universe

We know we live in an expanding universe but it’s also changing colour and has been doing so for billions of years.

Take a look at a Hubble image (above) of the distant universe and you will see hundreds of galaxies that come in a variety of shapes and colours. So what are we seeing?

Stretching light

In our expanding universe, galaxies are rushing away from us at vast speeds. Nearby galaxies, only millions of light years from Earth, are speeding away at hundreds of kilometres every second. More distant galaxies, billions of light years away, are rushing away at speeds in excess of 100,000 kilometres every second.

A natural consequence of this rapid expansion is the stretching of light via the Doppler Effect.

This stretching of light is similar to the stretching of sound waves here on Earth. The pitch of the sound from a motorcycle is lowered as it moves away from you. Just as sound waves are stretched (lower pitch) as a motorcycle races away, the light waves are stretched (redder light) as a distant galaxy races away.

(via afro-dominicano)