MAP

Thursday, 23 January 2014

"Heavy metal in the early cosmos" - 9 hours ago by Aaron Dubrow

Ab initio: "From the beginning.“ It is a term that's used in science to describe calculations that rely on established mathematical laws of nature, or "first principles," without additional assumptions or special models.
But when it comes to the phenomena that Milos Milosavljevic is interested in calculating, we're talking really ab initio, as in: from the beginning of time onward.
Things were different in the early eons of the universe. The cosmos experienced rapid inflation; electrons and protons floated free from each other; the universe transitioned from complete darkness to light; and enormous stars formed and exploded to start a cascade of events leading to our present-day universe.
Working with Chalence Safranek-Shrader and Volker Bromm at the University of Texas at Austin, Milosavljevic recently reported the results of several massive numerical simulations charting the forces of the universe in its first hundreds of millions of years using some of the world's most powerful supercomputers, including the National Science Foundation-supported Stampede, Lonestar and Ranger systems at the Texas Advanced Computing Center.
The results, described in the Monthly Notices of the Royal Astronomical Society in January 2014, refine how the first galaxies formed, and in particular, how metals in the stellar nurseries influenced the characteristics of the stars in the first galaxies.
"The universe formed at first with just hydrogen and helium," said Milosavljevic. "But then the very first stars cooked metals and after those stars exploded, the metals were dispersed into ambient space."
Eventually the ejected metals fell back into the gravitational fields of the dark matter haloes, where they formed the second generation of stars. However, the first generation of metals ejected from supernovae did not mix in space uniformly.
"It's as if you have coffee and cream but you don't stir it, and you don't wait for a long enough time," he explained. "You would drink some cream and coffee but not coffee with cream. There will be thin sheets of coffee and cream."
According to Milosavljevic, subtle effects like these governed the evolution of early galaxies. Some stars formed that were rich in metals, while others were metal-poor. Generally there was a spread in stellar chemical abundances because of the incomplete mixing.
Another factor that influenced the evolution of galaxies was how the heavier elements emerged from the originating blast. Instead of the neat spherical blast wave that researchers presumed before, the ejection of metals from a supernova was most likely a messy process, with blobs of shrapnel shooting in every direction.
"Modeling these blobs properly is very important for understanding where metals ultimately go," Milosavljevic said.
Predicting future observations
In astronomical terms, early in the universe translates to very far away. Those fugitive first galaxies are unbelievably distant from us now, if they haven't been incorporated into more recently-formed galaxies already. But many believe the early galaxies lie at a distance that we will be able to observe with the James Webb Space Telescope (JWST), set to launch in 2018. This makes Milosavljevic and his team's cosmological simulations timely.
"Should the James Webb Space Telescope integrate the image in one spot for a long time or should it mosaic its survey to look at a larger area?" Milosavljevic said. "We want to recommend strategies for the JWST."
Telescopes on the ground will perform follow-up studies of the phenomena that JWST detects. But to do so, scientists need to know how to interpret JWST's observations and develop a protocol for following up with ground-based telescopes.
Milosavljevic and others' cosmological simulations will help determine where the Space Telescope will look, what it will look for, and what to do once a given signal is observed.
Distant objects, born at a given moment in cosmic history, have tell-tale signature—spectra or light curves. Like isotopes in carbon dating, these signatures help astronomers recognize and date phenomenon in deep space. In the absence of any observations, simulations are the best way of predicting these light signatures.
"We are anticipating observations until they become available in the future," he said.
If done correctly, such simulations can mimic the dynamics of the universe over billions of years, and emerge with results that look something like what we see... or hope to see with new farther-reaching telescopes.
"This is a really exciting time for the field of cosmology," astronomer and Nobel Laureate Saul Perlmutter said in his keynote address at the Supercomputing '13 conference in November. "We are now ready to collect, simulate and analyze the next level of precision data... There's more to high performance computing science than we have yet accomplished."
Understanding our place in the universe
In addition to the practical goals of guiding the James Webb Space Telescope, the effort to understand these very early stars in the first galaxies has another function: to help tell the story of how our solar system came to be.
The current state of the universe is determined by the violent evolutions of the generations of stars that came before. Each generation of stars (or "population," in astronomy terms) has its own characteristics, based on the environment it was created in.
The Population III stars, the earliest that formed, are thought to have been massive and gaseous, consisting initially of hydrogen and helium. These stars ultimately collapsed and seeded new, smaller, stars that clustered into the first galaxies. These in turn exploded again, creating the conditions of Population I stars like our own, chock full of materials that enable life. How stars and galaxies evolved from one stage to another is still a much-debated question.
"All of this was happening when the universe was very young, only a few hundred million years old," Milosavljevic said. "And to make things more difficult, stars—like people—change. Every hundred million years, every 10 million years—it's like a kid growing up, all the time something new is happening."
Simulating the universe from birth to its current age, Milosavljevic and his team's investigations help disentangle how galaxies changed over time, and provide a better sense of what came before us and how we came to be.

Said Nigel Sharp, program director in the Division of Astronomical Sciences at the National Science Foundation: "These are novel studies using methods often ignored by other efforts, but of great importance as they impact so much of what happens in later cosmology and galaxy studies."

Tuesday, 21 January 2014

Milky Way shaken... and stirred 20 January 2014. A team of scientists headed by Ivan Minchev from the Leibniz Institute for Astrophysics Potsdam (AIP)

Milky Way shaken... and stirred

20 January 2014. A team of scientists headed by Ivan Minchev from the Leibniz Institute for Astrophysics Potsdam (AIP) has found a way to reconstruct the evolutionary history of our galaxy, the Milky Way, to a new level of detail. The investigation of a data set of stars near the sun was decisive for the now published results.
Milky Way shaken... and stirred
Three stages of the evolution of the galaxy simulation used to model the Milky Way. (Credit: AIP)
The astronomers studied how the vertical motions of stars - in the direction perpendicular to the galactic disc - depend on their ages. Because a direct determination of the age of stars is difficult, the astronomers instead analyzed the chemical composition of stars: an increase in the ratio of magnesium to iron ([Mg/Fe]) points to a great age. For this study, Ivan Minchev’s team took advantage of high-quality data regarding stars close to the Sun from the RAdial Velocity Experiment (RAVE). The scientists found that the rule of thumb “the older a star is, the faster it moves up and down through the disc” did not apply to the stars with the highest magnesium-to-iron ratios. Contrary to expectations, scientists observed an extreme drop in the vertical speed for these stars.
To understand these surprising observations, the scientists ran a computer model of the Milky Way, which allowed them to examine the origin of these slow-moving, old stars. After studying the computer model, they found that small galactic collisions might be responsible. It is thought that the Milky Way has undergone hundreds of such collisions with smaller galaxies in the course of its history. These collisions are not very effective at shaking up the massive regions near the galactic center. However they can trigger the formation of spiral arms and as a consequence move stars from the center of the Galaxy to the outer parts, where the Sun is. This “radial migration” process is able to transport outward old stars (with high values of magnesium-to-iron ratio) and with low up-and-down velocities. Therefore, the best explanation for why the oldest stars near our Sun have such small vertical velocities is that they were forced out of the galactic center by galactic collisions. The difference in speed between those stars and the ones born close to the Sun thereby betray how massive and how numerous the merging satellite galaxies were.
AIP scientist Ivan Minchev: “Our results will enable us to trace the history of our home Galaxy more accurately than ever before. By looking at the chemical composition of stars around us, and how fast they move, we can deduce the properties of satellite galaxies interacting with the Milky Way throughout its lifetime. This can lead to an improved understanding of how the Milky Way may have evolved into the Galaxy we see today.”
The article “A new stellar chemo-kinematic relation reveals the merger history of the Milky Way disc” was published in the Astrophysical Journal Letters on January 20.

Caption: Three stages of the evolution of the galaxy simulation used to model the Milky Way. Face-on (top) and edge-on (bottom) stellar density contours are shown for each time. Each square panel has a side of about 117,500 light years. The mass and frequency of satellites galaxies interacting with the disc decrease with time. (Credit: AIP)

Friday, 17 January 2014

What’s On The Far Side Of The Moon? by FRASER CAIN on JANUARY 16, 2014

You probably know we only see one side of the Moon from the Earth. But for the majority of human history, we had no idea what the far side looked like.
Billions of years ago, our Moon was formed when a Mars-sized object smashed into the Earth, spinning out a ring of debris. This debris collected into the Moon we know today. It started out rotating from our perspective, but the Earth’s gravity slowed it down until its rotation became locked with the Earth’s, keeping one half forever hidden from our view.
It wasn’t until the space age that humans finally got a chance to see what’s on the other side. The first spacecraft to image the far side of the Moon was the Soviet Luna 3 probe in 1959, which returned 18 usable images to scientists. And then in 1965, the Soviet
Zond 3 transmitted another 25 pictures of higher quality that gave much more detail of the surface. The first humans to actually see the far side with their own eyes, were the crew of Apollo 8, who did a flyover in 1968.
We now have high resolution cameras imaging every square meter, even the far side. And here’s the amazing surprise….
You would think that the far side of the Moon would look like the near side, but check out the two hemispheres…They’re totally different.
The near side of the has huge regions of ancient lava flows, called maria. While the far side is almost entirely covered in crater impacts. Planetary geologists aren’t sure, but it’s possible that the Earth used to have two Moons.
Billions of years ago, the second, smaller moon crashed into the far side of the Moon, covering up the darker maria regions.
And just to clarify things with Pink Floyd’s reference to the “Dark Side of the Moon”… Except for the occasional lunar eclipse, half of the Moon is always in darkness and half is always illuminated. But that illuminated half changes as the Moon orbits around us.
Just like half of the Earth is always in darkness, and half of every other large object in the Solar System. There’s no permanent “dark side” of the Moon. The side facing towards the Sun is lit up, and the side facing away is in shadows.
There are, however, some spots on the Moon which are in eternal darkness. There are craters at the north and south poles deep enough that the light from the Sun never illuminates their floors. In these places, It’s possible that there are reserves of ice that future space colonies could use for their supplies of water, air, and even rocket fuel.
Pink Floyd was right if you’re talking radio waves instead of visible light. The far side of the Moon is naturally shielded from the Earth’s radio transmissions, so it makes an ideal spot to locate a sensitive radio observatory.

I’ll see you in the permanently shadowed craters of the Moon.

Some Planet-like Kuiper Belt Objects Don’t Play “Nice” by MATTHEW FRANCIS on JANUARY 16, 2014

The Kuiper belt — the region beyond the orbit of Neptune inhabited by a number of small bodies of rock and ice — hides many clues about the early days of the Solar System. According to the standard picture of Solar System formation, many planetesimals were born in the chaotic region where the giant planets now reside. Some were thrown out beyond the orbit of Neptune, while others stayed put in the form of Trojan asteroids (which orbit in the same trajectory as Jupiter and other planets). This is called the Nice model.
However, not all Kuiper belt objects (KBOs) play nicely with the Nice model.

(I should point out that the model is named
named for the city in France and therefore pronounced “neese”.) A new study of large scale surveys of KBOs revealed that those with nearly circular orbits lying roughly in the same plane as the orbits of the major planets don’t fit the Nice model, while those with irregular orbits do. It’s a puzzling anomaly, one with no immediate resolution, but it hints that we need to refine our Solar System formation models.
This new study is described in a recently released paper by Wesley Fraser, Mike Brown, Alessandro Morbidelli, Alex Parker, and Konstantin Baygin (to be published in the Astrophysical Journalavailable online). These researchers combined data from seven different surveys of KBOs to determine roughly how many of each size of object are in the Solar System, which in turn is a good gauge of the environment in which they formed.
The difference between this and previous studies is the use of absolute magnitudes — a measure of how bright an object really is — as opposed to their apparent magnitudes, which are simply how bright an object appears. The two types of magnitude are related by the distance an object is from Earth, so the observational challenge comes down to accurate distance measurements. Absolute magnitude is also related to the size of an KBO and its albedo (how much light it reflects), both important physical quantities for understanding formation and composition.
Finding the absolute magnitudes for KBOs is more challenging than apparent magnitudes for obvious reasons: these are small objects, often not resolved as anything other than points of light in a telescope. That means requires measuring the distance to each KBO as accurately as possible. As the authors of the study point out, even small errors in distance measurements can have a large effect on the estimated absolute magnitude.
The bodies in the Kuiper Belt. Credit: Don Dixon
In terms of orbits, KBOs fall into two categories: “hot” and “cold”, confusing terms having nothing to do with temperature. The “cold” KBOs are those with nearly circular orbits (low eccentricity, in mathematical terms) and low inclinations, meaning their trajectories lie nearly in the ecliptic plane, where the eight canonical planets also orbit. In other words, these objects have nearly planet-like orbits. The “hot” KBOs have elongated orbits and higher inclinations, behavior more akin to comets.
The authors of the new study found that the hot KBOs have the same distribution of sizes as the Trojan asteroids, meaning there are the same relative number of small, medium, and large KBOs and similarly sized Trojans. That hints at a probable common origin in the early days of the Solar System. This is in line with the Nice model, which predicts that, as they migrated into their current orbits, the giant planets kicked many planetesimals out beyond Neptune.
However, the cold KBOs don’t match that pattern at all: there are fewer large KBOs relative to smaller objects. To make matters more strange, both hot and cold seem to follow the same pattern for the smaller bodies, only deviating at larger masses, which is at odds with expectations if the cold KBOs formed where they orbit today.

To put it another way, the Nice model as it stands could explain the hot KBOs and Trojans, but not the cold. That doesn’t mean all is lost, of course. The Nice model seems to do very well except for a few nagging problems, so it’s unlikely that it’s completely wrong. As we’ve learned from studying exoplanet systems, planet formation models are a work in progress — and astronomers are an ingenious lot.


Tuesday, 14 January 2014

Why Einstein will never be wrong 57 minutes ago by Brian Koberlein, Universe Today

One of the benefits of being an astrophysicist is your weekly email from someone who claims to have "proven Einstein wrong". These either contain no mathematical equations and use phrases such as "it is obvious that..", or they are page after page of complex equations with dozens of scientific terms used in non-traditional ways. They all get deleted pretty quickly, not because astrophysicists are too indoctrinated in established theories, but because none of them acknowledge how theories get replaced.

For example, in the late 1700s there was a theory of heat known as caloric. The basic idea of caloric was that it was a fluid that existed within materials. This fluid was self-repellant, meaning it would try to spread out as evenly as possible. We couldn't observe this fluid directly, but the more caloric a material has the greater its temperature.
From this theory you get several predictions that actually work. Since you can't create or destroy caloric, heat (energy) is conserved. If you put a cold object next to a hot object, the caloric in the hot object will spread out to the cold object until they reach the same temperature. When air expands, the caloric is spread out more thinly, thus the temperature drops. When air is compressed there is more caloric per volume, and the temperature rises.
We now know there is no "heat fluid" known as caloric. Heat is a property of the motion (kinetic energy) of atoms or molecules in a material. So in physics we've dropped the caloric model in terms of kinetic theory. You could say we now know that the caloric model is completely wrong.
Except it isn't. At least no more wrong than it ever was.
The basic assumption of a "heat fluid" doesn't match reality, but the model makes predictions that are correct. In fact the caloric model works as well today as it did in the late 1700s. We don't use it anymore because we have newer models that work better. Kinetic theory makes all the predictions caloric does and more. Kinetic theory even explains how the thermal energy of a material can be approximated as a fluid.
This is a key aspect of scientific theories. If you want to replace a robust scientific theory with a new one, the new theory must be able to do more than the old one. When you replace the old theory you now understand the limits of that theory and how to move beyond it.
In some cases even when an old theory is supplanted we continue to use it. Such an example can be seen in Newton's law of gravity. When Newton proposed his theory of universal gravity in the 1600s, he described gravity as a force of attraction between all masses. This allowed for the correct prediction of the motion of the planets, the discovery of Neptune, the basic relation between a star's mass and its temperature, and on and on. Newtonian gravity was and is a robust scientific theory.
Then in the early 1900s Einstein proposed a different model known as general relativity. The basic premise of this theory is that gravity is due to the curvature of space and time by masses. Even though Einstein's gravity model is radically different from Newton's, the mathematics of the theory shows that Newton's equations are approximate solutions to Einstein's equations. Everything Newton's gravity predicts, Einstein's does as well. But Einstein also allows us to correctly model black holes, the big bang, the precession of Mercury's orbit, time dilation, and more, all of which have been experimentally validated.
So Einstein trumps Newton. But Einstein's theory is much more difficult to work with than Newton's, so often we just use Newton's equations to calculate things. For example, the motion of satellites, or exoplanets. If we don't need the precision of Einstein's theory, we simply use Newton to get an answer that is "good enough." We may have proven Newton's theory "wrong", but the theory is still as useful and accurate as it ever was.
Unfortunately, many budding Einsteins don't understand this.
To begin with, Einstein's gravity will never be proven wrong by a theory. It will be proven wrong by experimental evidence showing that the predictions of general relativity don't work. Einstein's theory didn't supplant Newton's until we had experimental evidence that agreed with Einstein and didn't agree with Newton. So unless you have experimental evidence that clearly contradicts general relativity, claims of "disproving Einstein" will fall on deaf ears.
The other way to trump Einstein would be to develop a theory that clearly shows how Einstein's theory is an approximation of your new theory, or how the experimental tests general relativity has passed are also passed by your theory. Ideally, your new theory will also make new predictions that can be tested in a reasonable way. If you can do that, and can present your ideas clearly, you will be listened to. String theory and entropic gravity are examples of models that try to do just that.

But even if someone succeeds in creating a theory better than Einstein's (and someone almost certainly will), Einstein's theory will still be as valid as it ever was. Einstein won't have been proven wrong, we'll simply understand the limits of his theory.

Monday, 13 January 2014

Getting our hands on dark matter

My conversation in Quantumdiaries [blog]- CERN


SHREEKANT says:

The location[condition] where we are searching ‘the high impact of DM’ is correct? Our atmosphere is now almost STABLE.
At present condition, it is true that little more impact seen in
Xe than Ge/Si [here interaction with Nucleus taken, not Atom].
It is also true that DM is more near the GALAXY & …., but what about other places?
DA,DM are not far away to feel & their interactions with Baryon is not too complicated to
understand.Is only air comes out when we fill water in empty bottle?
The role of DE energy is interesting. The role of 94-96% is very important in this universe. Our present theory is only based on the knowledge of 4-6%

CERN says:

Hello,
of course, it is hard to say we know how to look for dark matter. Nobody know yet if and how it may interact with matter. So we test many hypotheses.
Dark matter is also seen to be concentrated in galaxy centres so indeed, it is a good place to look.
Outside a galaxy centre, the density of dark matter is much reduced. For example, in our Solar system, far away from the galaxy center, the quantity of dark matter within the Solar system amounts to 0.0000000000001 times the mass of the sun. So yes, when you fill up a bottle, it is essentially just air coming out. There is very little dark matter here to start plus it permeates regular matter anyway.
I hope this helps, Pauline
SHREEKANT says:

Tnx. for such a quick response.
It means our immediate surrounding [invisible part] contain only air? Then what about SUPERSYMMETRY & 96%?

SHREEKANT says:

Telecommunications expert suggests Earth may have dark matter disc
Jan 03, 2014 by Bob
Yirka


It is true that dark atoms are present everywhere including near the earth. But the sizes of resulting dark matters are smaller near the earth with respect to that found near galactic cores or stars.
It is also true that the size of dark matters near equator is little larger than at other places on the earth except inside the earth. Dark atoms are always balancing white atoms to maintain super-symmetry. If we put water in a bottle, both dark atoms & air (white atoms) comes out. White atoms are swimming in the ocean of dark atoms. Dark atoms & dark matters have been continuously adjusting them self in universe. Stars are not the source of dark atoms but they are the warehouse of dark atom.


CERN says:

Well.. while it is true that dark matter is more concentrated in the center of galaxies (and therefore there is less dark matter around us on Earth since the Earth is far from the galactic center), I doubt anyone can confirm that there is more around the equator than the poles. And you are talking about dark matter atoms: we do not know if dark matter forms composite objects like regular matter. And when you say: smaller, you mean in fact less concentrated or fewer dark matter. But I am afraid many of your assertions there are pure speculations. And you might well be right when you say that stars are not the source of dark matter (not atoms) but just warehouses for them. In fact, I think this statement is more tru for galaxies than for stars. Dark matter palyed a role in galaxy formation but not in star formation.
Cheers, Pauline

SHREEKANT says:

Kindly refer to your response dated January 8, 2014 at 7:29 am, I want to contradict on following points:

1. Dark matter is also made up of dark atom.

2. Dark matter is more concentrated in the centre of galaxies but it is not the warehouse of them, it is the PRODUCTION HOUSE.

3. Dark matter do not play a major role in galaxy formation, it is a part of GALAXY.

4. Earth has less dark matter but it is not due to very large distance from galactic core.

5. When I say smaller dark atom it means size not its concentration.

6. Dark matter do not plays a direct role in star formation but its alignment will help in star formation just away the galactic core in DISC not in HALO.

Yes, my assertions are appearing as pure speculation but all my comments (very short) on black holes, dark matter, supernova, gravity etc.(ref-below links) are on the basis of dark matter & dark energy.

I can explain the cause of lots of phenomenon on which our scientists are working. I can give the evidences of my speculation by explaining the causes of gravity, formation stars, formation of planets, formation of moon, formation of dark atom, formation of dark energy, how dark atom are continuously interacting with the environment, why dark matter is more near galactic core?, what is the destination of dark atom formed in galactic core?, formation of electron ring around the earth, why comet is not the source of life on earth, why neutrino found more near Antarctica, why a molded metal object remain in the same shape ….. these are only the few.

I am delighted if you or your team member will guide me, where & how I can place my detailed work to cross check or amend.

US experiment to vote on dark matter 16 Oct 2013 | 01:10 BST | Posted by Eugenie Samuel Reich | NATURE NEWS BLOG

New Kind of Dark Matter Could Form ‘Dark Atoms’ by Charles Q. Choi, SPACE.com Contributor Date: 10 June 2013 Time: 05:32 PM ET

“Fat gravity particle gives clues to dark energy” Force-carrying ‘gravitons’ with mass could help to explain Universe’s accelerating expansion. Zeeya Merali 10 September 2013

Observations reveal carbon monoxide “snow line” in exosolar system Posted on July 22, 2013 by Physics Today

Hidden mantle material may help explain Earth’s origins Posted on July 17, 2013 by Physics Today

The Earth’s Gold –”A Neutron Star Collision Was the Source” -The Daily Galaxy via CfA, July 18, 2013

“An Unknown Force of the Universe is Acting on Dark Matter” (4th of July Feature)-July 04, 2013

White dwarf star throws light on possible variability of a constant of Nature [2 hours ago-in Phy.org]


Astronomers discover pulsations from crystalized dying star This discovery will allow scientists to see below the white dwarf’s atmosphere and into its interior. By McDonald Observatory at University of Texas, Austin — Published: June 24, 2013

Spectacular Sun Storm Sheds Light on Star Formation by Mike Wall, SPACE.com Senior WriterDate: 20 June 2013 Time: 02:01 PM ET

Giant Black Hole’s Dust Oddity Surprises Scientists by Clara Moskowitz, SPACE.com Assistant Managing EditorDate: 20 June 2013 Time: 06:00 AM ET

Study explains decades of black hole observations 19 hours ago by Susan Gawlowicz

Alien Life Unlikely Around White and Brown Dwarfs, Study Finds Charles Q. Choi, Astrobiology

Magazine Contributor Date: 05 June 2013 Time: 07:00 AM ET
A Rare Opportunity to Watch a Blue Straggler Forming by SHANNON HALL on JUNE 11, 2013

Theorists weigh in on where to hunt dark matter May 22, 2013 by Lori Ann White


CERN says:

Hello again,
it’s great to hear that you have the answers or assertions to all these questions.But what matters most in science is tangible proofs. A theory, as elegant as it might be, remains just hypothetical until it is proven by hard facts. This is exactly what happened with the Higgs boson and the Brout-Englert-Higgs field. It all remained pure speculation until the LHC experiments discovered a type of Higgs boson in 2012. I agree with you: it seems logical to suppose that dark matter is also made of dark atoms, themselves being built of dark particles. This is a widely accepted idea in the physics community but no one can say it is so until he or she has proven it.
The best place to expose your ideas is to submit your paper to the Physics archives:http://arxiv.org/ The whole physics community will then be able to see your ideas. It is certainly a more suited place than this blog. It is indeed the policy of the Quantum Diaries site to only accept short comments on the topics addressed in blogs.

Cheers, Pauline