The nature of the highly compressed matter that makes up neutron stars has been the subject of much speculation. For example, it’s been suggested that under extreme gravitational compression the neutrons may collapse into quark matter composed of just strange quarks – which suggests that you should start calling a particularly massive neutron star, a strange star.
However, an alternate model suggests that within massive neutron stars – rather than the neutrons collapsing into more fundamental particles, they might just be packed more tightly together by adopting a cubic shape. This might allow such cubic neutrons to be packed into about 75% of the volume that spherical neutrons would normally occupy.
Some rethinking about the internal structure of neutron stars has been driven by the 2010 discovery that the neutron star PSR J1614–2230, has a mass of nearly two solar masses – which is a lot for a neutron star that probably has a diameter of less than 20 kilometres.
PSR J1614–2230, described by some as a ‘superheavy’ neutron star, might seem an ideal candidate for the formation of quark matter – or some other exotic transformation – resulting from the extreme compression of neutron star material. However, calculations suggest that such a significant rearrangement of matter would shrink the star’s volume down to less than the Schwarzschild radius for two solar masses – meaning that PSR J1614–2230 should immediately form a black hole.
But nope, PSR J1614–2230 is there for all to observe, a superheavy neutron star, which is hence almost certainly composed of nothing more exotic that neutrons throughout, as well as a surface layer of more conventional atomic matter.
Nonetheless, stellar-sized black holes can and do form from neutron stars. For example, if a neutron star in a binary system continues drawing mass of its companion star it will eventually reach the Tolman–Oppenheimer–Volkoff limit. This is the ultimate mass limit for neutron stars – similar in concept to the Chandrasekhar limit for white dwarf stars. Once a white dwarf reaches the Chandrasekhar limit of 1.4 solar masses it detonates as a Type 1a supernova. Once, a neutron star reaches the Tolman–Oppenheimer–Volkoff mass limit, it becomes a black hole.
Due to our current limited understanding of neutron star physics, no-one is quite sure what the Tolman–Oppenheimer–Volkoff mass limit is, but it is thought to lie somewhere between 1.5 – 3.0 solar masses.
So, PSR J1614–2230 seems likely to be close to this neutron star mass limit, even though it is still composed of neutrons. But there must be some method whereby a neutron star’s mass can be compressed into a smaller volume, otherwise it could never form a black hole. So, there should be some intermediary state whereby a neutron star’s neutrons become progressively compressed into a smaller volume until the Schwarzschild radius for its mass is reached.
Llanes-Estrada and Navarro propose that this problem could be solved if, under extreme gravitational pressure, the neutrons’ geometry became deformed into smaller cubic shapes to allow tighter packing, although the particles still remain as neutrons.
So if it turns out that the universe does not contain strange stars after all, having cubic neutron stars instead would still be agreeably unusual.
Further reading: Llanes-Estrada and Navarro. Cubic neutrons.
Universe Today: You’ve been really busy, with writing books, filming two television series and DVDs. Do you have time to do research in particle physics as well?
Brian Cox: Well, I must say I’ve been a bit restricted over the past couple of years in how much research I’ve done. I’m still attached to the experiment at CERN, but it’s just one of those things! In many ways it’s a regret because I would love to be there full time at the moment because it is so genuinely exciting. We’re making serious progress and we’re going to discover something like the Higgs particle, I would guess, within the next 12 months.
But then again, you can’t do everything and it’s a common regret amongst academics, actually, that that as they get older, they get taken away from the cutting-edge of research if they’re not careful! But I suppose it is not a bad way to be taken away from the cutting edge, to make TV programs and push this agenda that I have to make science more relevant and popular.
UT : Absolutely! Outreach and educating the public is very important, especially in the area of research you are in. I would guess a majority of the general public are not exceptionally well-versed in particle physics.
Cox: Well, Carl Sagan is a great hero of mine and he used to say it is really about teaching people the scientific method – or actually providing the understanding and appreciation of what science is. We look at these questions, such as what happened just after the Universe began, or why the particles in the Universe have mass – they are very esoteric questions.
But the fact that we’ve been able build some reasonable theories about the how old universe is — and we have a number 13.73 ± 0.12 billion years old, quite a precise number — so the question of showing how you get to those quite remarkable conclusions is very important. When you look at what we might call more socially-important subjects – for example how to respond to global warming, or what should be our policy for vaccinating the population against disease, or how should we produce energy in the future, and if you understand what the scientific method is and that it is apolitical and a-religious and it is a-everything and there is no agenda there, and is just pure way of looking of universe, that’s the important thing for society to understand.
“Wonders of the Universe” is a book about the television series. Traditionally these books are quite ‘coffee table,’ image-heavy books. The filming of the series took longer than we anticipated, so actually the book got written relatively quickly because I had time to sit down and really just write about the physics. Although it is tied with the television series, it does go quite a lot deeper in many areas. I’m quite pleased about that. So it’s more than just snapshots of my view of the physics of the TV series.
I should say also, some parts of it are in the form of a diary of what it was like filming the TV series. There are always some things you do and places you go that have quite an impact on you. And I tend to take a lot of pictures so many of the photographs in the book are mine. So, it is written on two levels: It is a much deeper view of the physics of the television series, but secondly it is a diary of the experience of filming the series and going to those places.
(Editor’s note, Cox is also just finishing a book on quantum mechanics, so look for that in the near future)
UT : What were some of your best experiences while filming ‘Wonders?’
Cox: One thing that, well, I wouldn’t say enjoyed filming, because it was quite nerve-wracking – but something that really worked was the prison demolition sequence in Rio. We used it as an analog for a collapsing star, a star at the end of its life that has run out of fuel and it collapses under its own gravity. It does that in a matter of seconds, on the same timescale as a building collapses when you detonate it.
Wandering around a building that is full of live dynamite and explosives is not very relaxing! It was all wired up and ready to go. But when we blew it up, and I thought it really worked well, and I enjoyed it a lot, actually as a television piece.
The ambition of the series is to try and get away from using too many graphics, if possible. You obviously have to use some graphics because we are talking about quite esoteric concepts, but we tried to put these things ‘on Earth’, by using real physical things to talk about the processes. What we did, we went inwards into the prison and at each layer we said, here’s where the hydrogen fuses to helium, and here’s the shell where helium goes to carbon and oxygen, and another shell all the way down to iron at the center of the stars. That’s the way stars are built, so we used this layered prison to illustrate that and then collapse it. That’s a good example of what the ambition of the series was.
UT : You’ve been called a rock star in the physics and astronomy field but in actuality you did play in a rock band before returning to science. What prompted that shift in your career?
Cox: I always wanted to be a physicist or astronomer from as far back as I can remember, that was always my thing when I was growing up. I got distracted when I was in my teens, or interested I should say, in music and being in a band. The opportunity came to join a band that was formed by an ex-member of Thin Lizard, a big rock band in the UK, and the States as well, so I did that. We made two albums; we toured with lots of people. That band split up and I went to university and then joined another band as a side line, and that band got successful as well. That was two accidents, really! It was a temporary detour rather than a switch, because I always wanted to do physics.
UT : Thanks for taking the time to talk with us on Universe Today – we appreciate all the work you do in making science more accessible so everyone can better appreciate and understand how it impacts our lives.
The ‘Snowman’ is a string of three craters and is among the most strange and prominent features discovered on a newly unveiled world in our solar system – the giant asteroid Vesta. It reminded team members of the jolly wintertime figure – hence its name – and is a major stand out in the 3 D image above and more snapshots below.
Until a few weeks ago, we had no idea the ‘Snowman’ even existed or what the rest of Vesta’s surface actually looked like. That is until NASA’s Dawn spacecraft approached close enough and entered orbit around Vesta on July 16 and photographed the Snowman – and other fascinating Vestan landforms.
“Each observation of Vesta is producing incredible views more exciting than the last”, says Dawn’s Chief Engineer, Dr. Marc Rayman of the Jet Propulsion Laboratory. “Every image revealed new and exotic landscapes. Vesta is unlike any other place humankind’s robotic ambassadors have visited.”
The Snowman is located in the pockmarked northern hemisphere of Vesta – see the full frame image below. The largest of the three craters is some 70 km in diameter. Altogether the trio spans roughly 120 km in length. See Image at Left
“Craters, Craters, Craters Everywhere” – that’s one thing we can now say for sure about Vesta.
And soon we’ll known a lot more about the mineralogical composition of the craters and Vesta because spectral data is now pouring in from Dawn’s spectrometers.
After being captured by Vesta, the probe “used its ion propulsion system to spiral around Vesta, gradually descending to its present altitude of 2700 kilometers (1700 miles),” says Chief Engineer Rayman. “As of Aug.11, Dawn is in its survey orbit around Vesta.”
Dawn has now begun its official science campaign. Each orbit currently last 3 days.
Dawn’s scientific Principal Investigator, Prof. Chris Russell of UCLA, fondly calls Vesta the smallest terrestrial Planet !
I asked Russell for some insight into the Snowman and how it might have formed. He outlined a few possibilities in an exclusive interview with Universe Today.
“Since there are craters, craters, craters everywhere on Vesta it is always possible that these craters struck Vesta in a nearly straight line but many years apart,” Russell replied.
“On the other hand when we see ‘coincidences’ like this, we are suspicious that it is really not a coincidence at all but that an asteroid that was a gravitational agglomerate [sometimes called a rubble pile] struck Vesta.”
“As the loosely glued together material entered Vesta’s gravity field it broke apart with the parts moving on slightly different paths. Three big pieces landed close together and made adjacent craters.”
So, which scenario is it ?
“Our science team is trying to figure this out,” Russell told me.
“They are examining the rims of the three craters to see if the rims are equally degraded, suggesting they are of similar age. They will try to see if the ejecta blankets interacted or fell separately”
“The survey data are great but maybe we will have to wait until the high altitude mapping orbit [HAMO] to get higher resolution data on the rim degradation.”
Dawn will descend to the HAMO mapping orbit in September.
Russell and the Dawn team are elated with the fabulous results so far, some of which have been a total surprise.
How old is the Snowman ?
“We date the age of the surface by counting the number of craters on it as a function of size and compare with a model that predicts the number of craters as a function of size and as a function of time from the present,” Russell responded.
“However this does not tell us the age of a crater. If the crater destroyed all small craters in its bowland and left a smooth layer [melt] then the small crater counts would be reset at the impact.”
“Then you could deduce the age from the crater counts. You can also check the degradation of the rim but that is not as quantitative as the small crater counts in the larger crater. The team is doing these checks but they may have to defer the final answer until they obtain the much higher resolution HAMO data,” said Russell.
Besides images, the Dawn team is also collecting spectral data as Dawn flies overhead.
“The team is mapping the surface with VIR- the Visible and Infrared Mapping Spectrometer – and will have mineral data shortly !”, Russell told me.
At the moment there is a wealth of new science data arriving from space and new missions from NASA’s Planetary Science Division are liftoff soon. Juno just launched to Jupiter, GRAIL is heading to the launch pad and lunar orbit and the Curiosity Mars Science Laboratory (MSL) is undergoing final preflight testing for blastoff to the Red Planet.
Russell had these words of encouragement to say to his fellow space explorers;
“Dawn wishes GRAIL and MSL successful launches and hopes its sister missions join her in the exploration of our solar system very shortly.”
“This year has been and continues to be a great one for Planetary Science,” Russell concluded.
It’s called a Lyman-alpha blob and it’s one of the largest known single objects in the Universe. It first made its presence known in the year 2000 and we know it’s located some 11.5 billion light years away. What will really get your attention is the size. LAB-1 has a diameter of about 300,000 light-years across!
Utilizing ESO’s Very Large Telescope (VLT), a team of astronomers were checking out areas of the early Universe where matter was the most dense – home to huge and very luminous rare structures called Lyman-alpha blobs. While there wasn’t anything in particular they were looking for, what they captured was something unique… evidence of polarization.
“We have shown for the first time that the glow of this enigmatic object is scattered light from brilliant galaxies hidden within, rather than the gas throughout the cloud itself shining.” explains Matthew Hayes (University of Toulouse, France), lead author of the paper.
These super-sized clouds of hydrogen gas stagger the imagination with their sheer dimensions. Some reach diameters of a few hundred thousand light-years – large enough to enfold the Milky Way three times over – and are as luminous as the most powerful galaxy we can observe. Since Lyman-alpha blobs are located so far away, we can only see them as they were when the Universe was a few billion years old, but they have a lot to teach us about their origins. Some theories suggest they shine when cool gas is pulled in by the blob’s powerful gravity and heated. Other conjectures are they are illuminated from within – lit by extreme star-forming events, supernovae or hungry black holes swallowing matter.
Thanks to these recent studies, the latest idea is the illumination comes from embedded galaxies. How do astronomers know this? By measuring whether the light from the blob was polarized. By measuring the physical processes that produced the light with sensitive equipment, researchers can gain insight from scattering or reflecting properties. However, the task hasn’t been easy considering the great distance of Lyman-alpha blobs.
“These observations couldn’t have been done without the VLT and its FORS instrument. We clearly needed two things: a telescope with at least an eight-metre mirror to collect enough light, and a camera capable of measuring the polarisation of light. Not many observatories in the world offer this combination.” adds Claudia Scarlata (University of Minnesota, USA), co-author of the paper.
According to ESO, the team observed their target for about 15 hours with the Very Large Telescope, and the light from the Lyman-alpha blob LAB-1 showed a centralized ring of polarization – but no central polarized spot. “This effect is almost impossible to produce if light simply comes from the gas falling into the blob under gravity, but it is just what is expected if the light originally comes from galaxies embedded in the central region, before being scattered by the gas. The astronomers now plan to look at more of these objects to see if the results obtained for LAB-1 are true of other blobs.”
If someone were to ask you when fear was first discovered, you could tell them August 11, 1877. That’s when, 134 years ago today, Asaph Hall identified Phobos, the larger of Mars’ two moons. But even though it’s named after the Greek god of fear, there’s nothing to be afraid of…
We just received a note from Andrew Franknoi and the Astronomical Society of the Pacific that they are making available, free of charge, 30 audio and video podcasts from talks given by distinguished astronomers on the latest ideas and discoveries in the field. Speakers include:
* Frank Drake, who began the experimental search for intelligent life among the stars,
* Mike Brown, who discovered most of the dwarf planets beyond Pluto (and whose humorous talk is entitled “How I Killed Pluto and Why it Had it Coming”),
* Natalie Batalha, project scientists on the Kepler Mission to find Earths around other stars,
* Alex Filippenko (national professor of the year) on finding black holes.
Recent topics added to the offerings include: multiple universes, Saturn’s moon Titan (with an atmosphere, rivers, and lakes), our explosive Sun, and whether we should expect doomsday in 2012.
The talks are part of the Silicon Valley Astronomy Lectures, jointly sponsored by NASA’s Ames Research Center, the Astronomical Society of the Pacific, the SETI Institute, and Foothill College.
They are available via the web and ITunes. For a complete list and to begin listening, go to: http://www.astrosociety.org/education/podcast/
There’s a brand new astronomy app for the iPhone, iPod Touch and iPad that provides information on what you should be able to see with different combinations of eyepieces on your telescope. AstroView displays key telescope-eyepiece performance characteristics, provides recommendations on equipment, and with the field of view display, for example, what you see on screen is what you should be able to see through your telescope. Developer George Douvos says this new app is all very intuitive, easy to read, and easy to understand.
Would you like to try a AstroView for free? Universe Today has 10 copies of this new app to give away. Just send an email to [email protected] with the word “AstroView App” in the subject line, and we’ll pick ten winners at random. The contest ends on Thursday, August 18, 2011.
Astro View supports the following gear:
* Telescopes with objective diameter from 50 mm to 610 mm, selectable in 5 mm increments (or diameters from 2 inches to 24 inches, in 1/2 inch increments), and focal ratios from f/3 to f/15.
* Eyepieces with focal lengths from 2 mm to 55 mm and apparent field of view from 30 to 110 degrees.
Thanks to George Duvous for providing us with the apps to giveaway!
When it comes to planets with rings, we know the answer: Jupiter, Saturn, Uranus, and Neptune. But new findings from the PAMELA experiment show that Earth has a ring system, too… One made up of geomagnetically trapped cosmic ray antiprotons.
“The existence of a significant flux of antiprotons confined to Earth’s magnetosphere has been considered in several theoretical works.” says team leader, O. Adriani of the University of Florence Department of Physics. “These antiparticles are produced in nuclear interactions of energetic cosmic rays with the terrestrial atmosphere and accumulate in the geomagnetic field at altitudes of several hundred kilometers.”
The PAMELA experiment – short for Payload for Antimatter Exploration and Light-nuclei Astrophysics – is based on an international collaboration involving about 100 physicists. Its state-of-the-art equipment was designed to investigate the nature of dark matter, the apparent absence of cosmological antimatter and the origin and evolution of matter in the galaxy. Utilizing a permanent magnet spectrometer with a variety of specialized detectors, PAMELA whips around Earth on a highly inclined orbit.
“The satellite orbit (70 degree inclination and 350–610 km altitude) allows PAMELA to perform a very detailed measurement of the cosmic radiation in different regions of Earth’s magnetosphere, providing information about the nature and energy spectra of sub-cutoff particles.” says Adriani. “The satellite orbit passes through the South Atlantic Anomaly (SAA), allowing the study of geomagnetically trapped particles in the inner radiation belt.”
From its subdetectors, PAMELA dished up a serving of antiprotons, but it wasn’t an easy job. “Antiprotons in the selected energy range are likely to annihilate inside the calorimeter, thus leaving a clear signature.” says the team. “The longitudinal and transverse segmentation of the calorimeter is exploited to allow the shower development to be characterized. These selections are combined with dE/dx measurements from individual strips in the silicon detector planes to allow electromagnetic showers to be identified with very high accuracy.”
For 850 days, the detectors collected data and compared it against simulations. The trapped antiprotons were highly dependent on angular collection, directional response function on the satellite orbital position and on its orientation relative to the geomagnetic field. “All the identified antiprotons, characterized by a pitch angle near 90 deg, were found to spiral around field lines, bounce between mirror points, and also perform a slow longitudinal drift around the Earth, for a total path length amounting to several Earth radii.” said the team. “PAMELA results allow CR transport models to be tested in the terrestrial atmosphere and significantly constrain predictions from trapped antiproton models, reducing uncertainties concerning the antiproton production spectrum in Earth’s magnetosphere.”
Original Story Source: Astrophysical Journal Newsletters.
This weekend should be the peak of the 2011 Perseid meteor shower. If you have any luck taking images of the event, we’d love to see them and share them with the world! To enable this, Universe Today has started a Flickr Group, where people can upload their astrophotos, which will make it easier for us to share everyone’s photos. If we use your image, we will give you full credit and link back to your Flickr account. Or if you’d rather submit your images via email, send them to Nancy, along with a little info about it (where/when/equipment/etc.)
We hope to soon begin a new ‘Amateur Astrophoto of the Day’ feature where we will use pictures people have sent us via Flickr as well, so look for more info on that soon.
In the meantime, get out and enjoy the Perseids, and remember you can share the experience with others via Twitter with MeteorWatch, led by UT’s Adrian West! Follow the #Meteorwatch hashtag, and Adrian’s @VirtualAstro Twitter feed.
And just where have your buckyballs been lately? More technically known as fullerenes, this magnetic form of carbon shows some pretty interesting properties deduced from laboratory work here on Earth. But even more interesting is its cousin – graphene. And guess where it’s been found?!
When you picture a fullerene, you conjure up a mental image of carbon atoms arranged in a three-dimensional configuration with two structures: C60 which patterns out similar to a soccer ball and C70 which more closely resembles a rugby ball. Both of these types of “buckyballs” have been detected in space, but the real kicker is graphene. Its technical name is planar C24 and instead of being geodesic, it’s the thinnest substance known. Just one atom thick, this flat sheet of carbon is a portrait in extraordinary strength, conductivity and elasticity. Graphene was first synthesized in the lab in 2004 and now planar C24 may have been detected in space.
Through the use of the Spitzer Space Telescope, a team of astronomers led by Domingo Aníbal García-Hernández of the Instituto de Astrofísica de Canarias in Spain have not only picked up a C70 fullerene molecule, but may have also detected graphene as well. “If confirmed with laboratory spectroscopy – something that is almost impossible with the present techniques – this would be the first detection of graphene in space” said García-Hernández.
Letizia Stanghellini and Richard Shaw, members of the team at the National Optical Astronomy Observatory in Tucson, Arizona suspect collisional shocks generated in stellar winds of planetary nebulae could be responsible for the presence of fullerenes and graphenes through the destruction of hydrogenated amorphous carbon grains (HACs). “What is particularly surprising is that the existence of these molecules does not depend on the stellar temperature, but on the strength of the wind shocks” says Stanghellini.
So where has this discovery taken place? Try the Magellanic Clouds. In this case, using a planetary nebula “closer to home” is not part of the equation because science needs to be certain the material they are looking at is indeed the by-product of a planetary nebula and not a mix. Fortunately the SMG is known to be metal-poor, which enhances the chances of spotting complex carbon molecules. Right now the challenge has been to pinpoint the evidence for graphene from Spitzer data.
“The Spitzer Space Telescope has been amazingly important for studying complex organic molecules in stellar environments” says Stanghellini. “We are now at the stage of not only detecting fullerenes and other molecules, but starting to understand how they form and evolve in stars.” Shaw adds “We are planning ground-based follow up through the NOAO system of telescopes. We hope to find other molecules in planetary nebulae where fullerene has been detected to test some physical processes that might help us understand the biochemistry of life.”