Detecting Gravitational Waves on the Cheap

Forget building gravitational wave detectors costing hundreds of millions of dollars (I’m looking at you, LIGO), make use of the most accurate cosmic timekeepers instead and save a bundle.

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a proposal that involves closely monitoring the regular flashes of spinning neutron stars (or pulsars) to detect very slight “shimmers” in their signal. Although the physics is crazy-complex, by tracking these shimmers over a suitably distributed number of pulsars could reveal the passage of gravitational waves.

However, there’s a problem with this plan; pulsars are notoriously tricky stellar objects, as my colleague Jennifer Ouellette points out:

The problem is that you need to closely monitor rapidly-spinning millisecond pulsars, which are (a) tough to find (only 150 have been found over nearly three decades since pulsars were first discovered), and (b) not very plentiful in the part of the night sky of interest to scientists (northern hemisphere). They tend to clump together in globular star clusters, which makes them useless for detecting gravitational waves.

However, according to results announced by the National Radio Astronomy Observatory (NRAO) at this week’s American Astronomical Society (AAS) meeting in Washington D.C., they’ve discovered 17 new pulsars with the help of NASA’s Fermi Gamma-Ray Space Telescope.

In addition to recent Fermi telescope pulsar discoveries, it would appear that the number of potential targets for NANOGrav are increasing, making a stronger case for the 10 year, $65 million project…

You have to wonder whether building the Laser Interferometer Gravitational-Wave Observatory (LIGO) was worth it (but you can’t be too careful, some terrorist organizations might want to use gravitational waves for evil, so it would be good if we detected them first).

Source: Discovery News

Prof. Brian Cox Accidentally REVEALS the TRUTH About the LHC!!!!

(Note the clever use of CAPS and excessive exclamation marks in the title. It speaks volumes.)

I guess this confirms I was wrong. Consider this an apology to all the crackpots, doomsayers, cranks and Walter Wagner. I’m sorry I got it all… so… wrong.

While out on the town in London, Bad Astronomer Phil Plait pulled Prof. Brian Cox out of a pub and subjected him to some intense interrogation. Obviously caught with his guard down, Cox folded under the pressure and briefly told the world what we can expect when the Large Hadron Collider (LHC) recommences experiments in November. Wow, just… wow.

This made me giggle. Looks like TAM London was a tonne of fun, hopefully next time I can go.

But for now, sorry Walter, you’re still wrong.

Whatever Happened to Hyper-Velocity Star HD 271791?

One scenario: Exploding star flings binary parter away at high velocity (Max Planck Institute for Astrophysics)

One scenario: Exploding star flings binary parter away at high velocity (Max Planck Institute for Astrophysics)

HC 271791 is a star with a problem, it’s moving so fast through our galaxy that it will eventually escape from the Milky Way all together. However, there is a growing question mark hanging over the reasons as to why HD 271791 is travelling faster than the galactic escape velocity.

So-called hyper-velocity stars were first predicted to exist back in 1988 when astrophysicist Jack Hills at Los Alamos National Laboratories pondered what would happen if a binary star system should stray too close to the supermassive black hole lurking in the galactic nucleus. Hills calculated that should one of the stars get swallowed by the black hole, the binary partner would be instantly released from the gravitational bind, flinging it away from the black hole.

This would be analogous to a hammer thrower spinning around, accelerating the ball of the hammer rapidly in a circle around his body. When the thrower releases the hammer at just the right moment, the weight is launched into the air, travelling tens of meters across the stadium. The faster the hammer thrower spins the ball, the greater the rotational velocity; when he releases the hammer, rotational velocity is converted to translational velocity, launching the ball away from him. Gold medals all ’round.

So, considering Hills’ model, when one of the stars are lost through black hole death, the other star is launched, hammer-style, at high velocity away from the galactic core. The fast rotational velocity is converted into a hyper-velocity star blasting through interstellar (and eventually intergalactic) space.

Hills actually took his theory and instructed the astronomical community to keep an eye open for speeding stellar objects, and sure enough they were out there. HD 271791 is one of these stars, travelling at a whopping 2.2 million kilometres per hour, a speed far in excess of the galactic escape velocity.

However, the 11 solar mass star didn’t originate from the Milky Way’s supermassive black hole (inside the radio source Sgr. A*), it was propelled from the outermost edge of the galactic disk. There is absolutely no evidence of a supermassive black hole out there, so what could have accelerated HD 271791 to such a high velocity? After all, stars aren’t exactly easy objects to throw around.

If HD 271791 used to be part of a binary pair, its partner would have had to suddenly disappear, releasing its gravitational grip rapidly. One idea is that HD 271791’s sibling exploded as a supernova. This should have provided the sudden loss in a gravitational field — the rapidly expanding supernova plasma will have dispersed the gravitational influence of the star.

However, according to Vasilii Gvaramadze at Moscow State University, the supernova theory may not be sound either; by his calculations a binary pair simply cannot produce such a large velocity. Gvaramadze thinks that a far more complex interaction between two binary pairs (four stars total) or one binary pair and another single star some 300 solar masses. Somehow, this “strong dynamical encounter” caused HD 271791 to be catapulted out of the system, propelling it at a galactic escape velocity.

Although this complex slingshot theory sounds pretty interesting, the supernova theory still sounds like the most plausible answer. But how could a sufficient rotational velocity be attained? As Gvaramadze points out, even an extreme rapidly orbiting binary pair cannot produce a star speeding at 530-920km/s.

This is in contrast to research carried out by scientists at the Max Planck Institute for Astrophysics and the University of Erlangen-Nuremberg. In a January 2009 press release, Maria Fernanda Nieva points out that this hyper-velocity star possesses the chemical fingerprint of having been in the locality of a supernova explosion. This leads Nieva to conclude that HD 271791 was ejected after its binary partner exploded. What’s more, a Wolf-Rayet may have been the culprit.

Up to now such a scenario has been dismissed for hyper-velocity stars, because the supernova precursor usually is a super-giant star and any companion has to be at large distance in order to orbit the star. Hence the orbital velocities are fairly modest. The most massive stars in the Galaxy, however, end their lives as quite compact so-called Wolf-Rayet stars rather than as super-giants. The compactness of the primary leaves room for a companion to move rapidly on a close orbit of about 1 day-period. When the Wolf-Rayet-star exploded its companion HD 271791 was released at very high speed. In addition, HD 271791 made use of the Milky Way rotation to finally achieve escape velocity. —Maria Fernanda Nieva

Even though Gvaramadze’s stellar pinball theory sounds pretty compelling, the fact that HD 271791 contains a hint of supernova remnant in its atmosphere, the supernova-triggered event sounds more likely. But there is the fact that just because this 11 solar mass star was near a supernova some time in its past, it certainly doesn’t indicate that a supernova was the cause of it’s high speed.

For now I suppose, the jury is still out…

Publication: On the origin of the hypervelocity runaway star HD271791, V.V.Gvaramadze, 2009. arXiv:0909.4928v1 [astro-ph.SR]

Original source: arXiv blog

The UK’s Brain Drain (been there, done that)

Professor-Stephen-Hawking-001

Back in 2006, I remember sitting in my local UK Job Centre finding out how I could claim for unemployment benefits.

I can see it now, the moment I explained to my liaison officer that I had been looking for work but received little interest. She looked at me and said, candidly, “Have you thought about not mentioning you have a PhD? It might help.” She smiled.

What? I now need to hide my qualifications if I want to get a job? Isn’t that a little counter-intuitive? Actually, as it turned out, she was right. Many of the jobs I had applied for didn’t require a postdoc to do them; why would a company hire me when they can hire a younger postgrad with lower salary expectations?

Up until that moment, I was still hopeful that I might be able to land an academic position; possibly back in my coronal physics roots, but funding was tight, and I hadn’t done enough networking during my PhD to find a position (I had been too busy scoping out the parties and free booze at the conference dinners).

So there I was, with all the qualifications in the world with no career prospects and a liaison officer who deemed it necessary to advise me to forget the last four years of my academic career. It was a low point in my life, especially as only a few months earlier I had been enjoying one of the highest points in my life: graduating as a doctor in Solar Physics.

Fortunately for me, I had another option. My girlfriend (now lovely wife) was living in the US, and although searching for a job in the UK was a priority for us (we were planning on living in the UK at the time), I knew I could try my luck in the US as well. So after a few months of searching, I cancelled my Job Centre subscription and moved to the other side of the Atlantic.

I had just become a part of the UK’s “brain drain” statistic. I had qualifications, but I was in a weird grey area where companies thought I was over-qualified and funds were in short supply for me to return to academic research.

A lot has happened since those uncertain postdoc times, and although I tried (and failed) to pick up my academic career in solar physics in the US (it turns out that even the sunny state of California suffers from a lack of solar physics funding), the job climate was different. Suddenly, having a PhD was a good thing and the world was my oyster again.

To cut a long story short, I’m happily married, we own five rabbits (don’t ask), we live just north or Los Angeles and I have a dream job with Discovery Channel, as a space producer for Discovery News.

Although I’d like to think that if I was currently living in the UK, I might have landed an equivalent career, I somehow doubt I would be as happy as I am right now with how my academic qualifications helped me get to where I am today.

Why am I bringing this up now? Having just read about Stephen Hawking stepping down as Lucasian professor of Mathematics at Cambridge University and the Guardian’s report about the risk of losing British thinkers overseas, I wonder if employment opportunities have improved since 2006. What’s most worrying is that there appears to be this emphasis on making money as quickly as possible, rather than pursuing academic subjects. However, in my experience, having a PhD doesn’t mean you can even land a job in industry, you might be over-qualified.

Giving up on that tradition of deep intellectual discovery in favour of immediate economic benefit is a huge mistake. You lose the gem of creative, insightful, long-term thinking. That is what Britain has done so spectacularly in the past, and to give that up is a tragedy.” —Neil Turok

A special thanks to Brian Cox, who tweeted the inspiration to this post.

Life is Grim on the Galactic Rim

The White Star approaches the Shadow's homeworld of Z'ha'dum on the Galactic Rim.

The White Star approaches the Shadow’s homeworld of Z’ha’dum on the Galactic Rim.

It would appear that scientists have confirmed that the outer edge of the Milky Way is a bad location for life to even think about existing.

This research reminded me of the “Galactic Rim” in the 90’s sci-fi TV series Babylon 5. The Rim is the mysterious region of space right at the edge of our galaxy where only the hardiest of explorers dared to venture. As explained in the season 2 episode of B5, “In the Shadow of Z’ha’dum,” Captain Sheridan (Bruce Boxleitner) discovers that his wife (when exploring The Rim) went missing on a planet called Z’ha’dum. It turns out that an angry ancient alien race — called the Shadows — lived on this mysterious world and their discovery led to them being used in all kinds of plots during the latter four seasons of this awesome sci-fi show.

However, the existence of any kind of life (let alone life as complex as the evil Shadows) in the badlands of the Milky Way is looking very unlikely.

Located some 62,000 light years from the core of our galaxy (over twice the distance of the Earth from the galactic centre), two very young star clusters in the constellation of Cassiopeia have been studied. Chikako Yasui, Naoto Kobayashi and colleagues at the University of Tokyo, Japan, found these clusters in a vast cloud of gas and dust called Digel Cloud 2. The stars inside these clusters are only half a million years old, and the majority of them should possess proto-planetary disks (which is characteristic of local star-forming regions). However, it would appear that these stars contain very little oxygen, silicon or iron (i.e. they have very low metallicity) and only 1 in 5 of the 111 baby stars analysed in both clusters have disks.

If proto-planetary disks are rare, this means there will be a rarity of planets. This is an obvious bummer for life to form. After all, Life As We Know It™ is quite attached to evolving on Earth-like planets.

So why are these young stars lacking proto-planetary disks, when local star forming regions don’t seem to have this affliction? The authors of the paper, soon to be published in the Astrophysical Journal, suggest that these stars did have disks, but some mechanism is rapidly eroding them.

The most likely scenario is that low metalicity proto-planetary disks are more susceptible to photoevaporation. Simply put, these disks evaporate when exposed to EUV and X-ray radiation from their parent stars far more rapidly than disks that are metal-rich.

Therefore, if an alien race was able to form, they’d be very rare or they’d be very different from what we’d expect “life” to be like (i.e. they thrive in low metalicity star systems). Sounds like the mysterious Shadow homeworld of Z’ha’dum would be a very rare sight on The Rim of our Milky Way after all.

Publication: The Lifetime of Protoplanetary Disks in a Low-Metallicity Environment, Chikako Yasui et al., 2009. arXiv:0908.4026v3 [astro-ph.SR]
via New Scientist

There’s a Fractal in My Brazilian Rainforest

Lago Erepecu and Rio Trombetas, Brazil (NASA)

Lago Erepecu and Rio Trombetas, Brazil (NASA)

The shapes of fractals appear in nature all the time, but when I saw this Earth Observatory image from the International Space Station, I thought I was looking at a zoomed-in portion of the famous Mandelbrot set graphic. This picture wasn’t formed by the calculations of a computer, however. This is what nature does when chaos comes out to play.

Imaged from orbit on August 25, 2009, an astronaut was able to get the timing just right with his/her Nikon D2Xs digital camera (plus 180 mm lens) so that sunlight was reflecting off Brazil’s Lago (Lake) Erepecu and Rio (River) Trombetas. Usually, water masses in the Brazilian Rainforest are too dark to be picked out in any detail, so this sunglint was very useful to pick out the fine detail of the waterways.

Source: Earth Observatory Program

Say Hello To My Little Friend: The Atom, Imaged

atom_photo

I am fascinated with outer space, this is true. But if you stop to think about it, the inner space between the atoms is just as awe-inspiring as the vast distances separating the planets, stars and galaxies. In actuality the volume inside an hydrogen atom is essentially empty; the single electron “orbits” (if we consider the simple Bohr model of the atom) the central proton at a huge distance. It’s analogous to a quantum star system, where a planet orbits its parent star, hundreds of millions of miles away.

However, atoms aren’t as simple as Niels Bohr’s famous model (although Bohr’s model is none-the-less important as it always has been). The electrons occupy a cloud, rather than specific orbits, and the electron’s position cannot be defined as a point, more a statistically defined volume. As dictated by quantum theory these clouds vibrate at certain frequencies, depending on the electron energy. These electron energies are analogous to the simple electron “shells” physicists refer to in the textbooks; each progressively higher shell occupying a higher energy state. In reality, in the slightly fuzzy quantum world, the frequency of electron oscillation increases with energy.

Examples of electron atomic and molecular orbitals. The "lobes" are representative of the electron clouds surrounding the nuclei

Examples of electron atomic and molecular orbitals. The lobes are representative of the electron clouds surrounding the nuclei (source)

When I was in university, I loved seeing the different modes of electron energy in 3D visualizations of the atom (pictured right). Lobes of electron clouds vibrating at different energies seemed to make sense. But now, for the first time, the clearest photographs of a single atom have been taken, with lobes of electron clouds — as predicted by quantum theory — intact.

This research soon to be published in the journal Physical Review B, demonstrates detailed images of a single carbon atom’s electron cloud (pictured top). Taken by Ukrainian researchers at the Kharkov Institute for Physics and Technology in Kharkov, Ukraine, these images clearly show the electron cloud in two energy states.

This amazing feat was accomplished using a field-emission electron microscope. Although this microscope has aided physicists since the 1930’s to image the vanishingly small, the Ukrainian researchers have developed a new way of making the tool so sensitive, single atoms can be imaged. After arranging a ridged chain of carbon atoms (only tens of atoms long) inside a vacuum chamber, the researchers passed 425 volts through the atoms. At the tip of the chain, the end carbon atom emitted its electrons and a surrounding phosphor screen captured an image. This image was of the electron cloud surrounding the single carbon atom.

Up until this point, field emitting microscopes have only been able to resolve the arrangement of atoms in a sample. This is the first time physicists have been able to see the structure of an electron cloud around an atom.

It’s always nice to validate a bedrock physics theory with photographic evidence, it’s exciting to think what the Kharkov Institute scientists will do next…

Source: Insidescience.org