Monday
Mar182013

Portrait of the supernova as a young supernova remnant

by Sarah Scoles

Rejoice and be glad! Astronomers have found and characterized a relatively young supernova. It looks like this: 

Well, it looks like this if you have eyes that see X-rays as blue, infrared waves as red and "cyan," and radio waves as purple. (Credit: NASA/CXC/Univ. of Michigan/M. Reynolds et al; Infrared: NASA/JPL-Caltech; Radio: CSIRO/ATNF/ATCA)This supernova remnant is (perhaps, about, approximately) 2500 years old, meaning that 2500 years ago (plus however long it took the light to get here) a star exploded. The material from that explosion has been traveling outward ever since, creating the still-moving shell pictured above. It's still moving to the tune of 670 kilometers per second, or about 1.5 million miles per hour. If you were traveling that fast, you could get to the Sun in 2.5 days, and you could also have an brain hemorrhage. And just think--this stellar material has been going that fast or faster 2500 years.

Did you know that you can get supernova remnant contacts? Actually, no, that's a lie. This is Photoshop. But that's a real supernova remnant image in her eye! (Credit: Gemini Moon Designs).

Using X-ray data from NASA's Swift telescope, the researchers also found spectral evidence of Silicon, Sulphur, and Argon. With more data about which atoms are hanging out in this violent gas cloud, they will be able to tell what type of supernova this was--Type Ia or core-collapse? In the former, a white dwarf in a binary system acquires a little more of its companion's mass than it can handle; in the latter, a dying red giant star whose empty-fuel-tank fusion no longer counterbalances its gravity. 

The abundances of elements like oxygen, neon, and silicon would be different in a white dwarf than they would be in a dying red giant star, so the remnants of their explosions would also differ in composition. Currently, it looks like Type Ia is going to be the winner, but, as usual, the scientists need more data

Here's the thing: fascinating as all of that is, it's really just about one supernova remnant, and how important can one supernova remnant be in the scheme of, you know, things? How important is it that this particular supernova has gas traveling at a particular speed? 

Well, it's not particularly important. What this remnant can tell us about how remnants and supernovae themselves work is important. What we can deduce about how this supernova affected its surrounding area (which depends on how supernovae work) is important. It can help explain how these explosions enable star formation and heavy-element infusion. Which is what allows you both to exist and to wear gold chains around your neck.

And the existence of this supernova, though not necessarily its details, is important because it represents a tiny step toward rectifying the discrepancy between how often we think stars in the Milky Way go supernova and how many actual remnants we see. There "should" be about 1,000 supernova leftovers in our galaxy. We know of 309. About 60 stars should" have gone supernova in the past 2,000 years. We know of 20. 

This supernova makes 310 total. Cha-ching.

So do we not understand stellar evolution? Do we not understand intragalaxy interactions? Do we not understand our own home? (hahaha, of course we don't). Or have we just not found these supernova remnants because astronomy needs more funding and more and bigger telescopes in order to be able to see superfaint radiation? Only by continuing to search for -- and either find or not find -- fast, hot gas shells can we tell the difference between telescopic inadequacy and our own mispredictions.

ResearchBlogging.org 

 

Mark Reynolds, Shyeh Loi, Tara Murphy, Jon Miller, Dipankar Maitra, Kayhan Gultekin, Neil Gehrels, Jamie Kennea, Michael Siegel, Jonathan Gelbord, Paul Kuin, Vanessa Moss, Sarah Reeves, William Robbins, Bryan Gaensler, Rubens Reis, & Robert Petre (2013). G306.3-0.9: A newly discovered young galactic supernova remnant Astrophysical Journal arXiv: 1303.3546v1

Tuesday
Mar122013

Science Highlights

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by Brooke Napier

Your brain can out-live you, just give it a chance

Neurons are terminally differentiated. This means that during development once a neuron receives all of the necessary developmental signals to differentiate into a neuron it stays a neuron. No replication, no nothing! So apparently, we’ve just been assuming that neurons age chronologically, like us – we get wrinkled, our neurons get wrinkled.

Turns out not so my friends! Lorenzo Magrassi and colleagues from Italy would like you to know that neuron aging is independent of the organismal (or whole body) lifespan. By transplanting neurons from mice that live ~18 months into embryonic rats that live ~36 months. Turns out these neurons integrated into the rat cerebellum, developed into mature neurons (still lookin’ like a mouse neuron in a rat brain) – however these neurons did not die at 18 months, but they survived as long as 36 months, doubling the average lifespan of the of the mice the neurons originated from. BOO YA!

This is a parasagittal section of rat cerebella at 3, 20, and 36 months of age. All original rat cells in the brain are red, all implanted mouse neurons are in green. There are tons of amazing photos in this manuscript, but I have to control myself… seeing is how this is “highlights”. Scale bar: 25 um

Primary article in PNAS:

Magrassi, L., Leto, K., & Rossi, F. (2013). Lifespan of neurons is uncoupled from organismal lifespan Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1217505110

 

Cellular “nets” can be thrown out to “catch” viruses

Like casting a net into the ocean to catch fish, human immune cells known as neutrophils can literally throw-up their own DNA into the extracellular space to trap bacteria during an infection. These are known as NETs (neutrophil extracellular traps).Here is a beautiful picture of NETs (yellow) killin’ Mycobacterium tuberculosis (red).

This phenomenon was discovered in Arturo Zychlinsky’s lab in 2004 and published in Science (my current boss happens to be on this paper, so that’s pretty bad ass). Since then researchers have been trying vigorously to understand this antimicrobial mechanism. So nearly 10 years after their discovery…

Craig Jenne and colleagues from University of Calgary (yeah Canadians!) have found that not only do neutrophils throw-up their DNA in effort to kill bacteria, but they do this in order to kill VIRUSES too! These NETs protected mice from pox infection. Amazing. Another article in the same journal published that these NETs are also interacting with HIV, but the extent isn’t fully understood.

 

Primary articles in Cell and Cell Host & Microbe:

Jenne, C., & Kubes, P. (2012). NETs Tangle with HIV Cell Host & Microbe, 12 (1), 5-7 DOI: 10.1016/j.chom.2012.07.002

 Jenne, C., Wong, C., Zemp, F., McDonald, B., Rahman, M., Forsyth, P., McFadden, G., & Kubes, P. (2013). Neutrophils Recruited to Sites of Infection Protect from Virus Challenge by Releasing Neutrophil Extracellular Traps Cell Host & Microbe, 13 (2), 169-180 DOI: 10.1016/j.chom.2013.01.005


Last but certainly not least…

Save the Tazmanian devils from transmissible cancer!

I was going to make a cheeky title here, but after looking at pictures of Tasmanian devils with cancer, it’s really not lighthearted topic at all. In fact, I’m glad I didn’t know about this epidemic until now, otherwise I would have had to quit my current PhD and start another one focused on curing Tasmanian devil cancer.

In the last 15 years nearly 60% of Tasmanian devils have died due to the spread of a contagious cancer called “devil facial tumour disease”, which transmits between animals during tussles over food.

Researchers have been in the dark on how the disease spreads and how it invades the host (which can severely deter progress on a potential vaccination!); however, yesterday Hannah Siddle, et al. published in PNAS that they now understand the mechanism of spread.

The contagious cancer is down regulating production of specific proteins in the immune system so that the immune system can no longer react to cancerous cells. Without an immune reaction there is no clearance of cancerous cells, thus tumors and further disease.

So what next? They say they are going to try to artificially introduce these immune regulatory proteins into naïve devils (devils that have not been exposed to the disease).  This introduction of immune proteins will jump start the immune system, allowing “enough of an immune response to tip the balance in favor of the devil”.

My question is… what is causing the disease? A virus? A bacterium? A prion?

Nature News Article

Primary Article in PNAS:

Siddle, H., Kreiss, A., Tovar, C., Yuen, C., Cheng, Y., Belov, K., Swift, K., Pearse, A., Hamede, R., Jones, M., Skjodt, K., Woods, G., & Kaufman, J. (2013). Reversible epigenetic down-regulation of MHC molecules by devil facial tumour disease illustrates immune escape by a contagious cancer Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1219920110


ResearchBlogging.org

 

Tuesday
Mar122013

Infographic about the gender wage gap

Here's a great infographic by Jessica Wallace about the differences that remain between men's and women's payment for work.

As Wallace says, "It’s 2012 and close to four years after the Lilly ledbetter Fair Pay Act was signed into law. Surely, the gender wage gap has been closed, right? Wrong.

"Even with moves toward equalizing pay between men and women, men still make almost 20% more than women in nearly all industries. This is despite the fact that women receive the same education, with the same tuition price tags and levels of debt upon graduation. The only major differences are that there are more ladies in college and they have better average GPAs to boot. The benefits of paying women their fair share include increasing the GDP while reducing the poverty rates for families.

Check out the infographic below to see what else the gender wage gap affects."

Created by: LearnStuff.com

Equal_Education_Unequal_Pay

Tuesday
Mar052013

The universe's gamer humor

While digging through the Hubble Hidden Treasures archive, regular citizen Nick Rose found a space invader. Or, actually, a Space Invader. As in, from that video game that came into existence before I did. The actual objects in space do not look like cartoon aliens. But their light makes them appear so by the time it gets to us.

A massive galaxy cluster, Abell 68, between the objects and Earth is skewing their light. Acting like a cosmic "funhouse mirror" (props for apt simile go to NASA), the cluster's gravitation and our particular line-of-sight led to this circus shot:

If only those galaxies could see themselves the way we see them.

So why do we see them this way?

If the checkerboard is spacetime, and the yellow ball is a massive object, this illustration shows how substance changes the local shape of the universe. If the checkerboard is not spacetime and the ball is not massive, I have no idea what it means (Credit: DJ Sadhu).

Relativity, short answer.

Long answer:

The universe doesn't make sense without relativity. Massive stuff and fast stuff just doesn't behave the way Newton's old-school gravity says it should. 

According to general relativity, mass bends spacetime -- the Spandex "fabric" of the universe.

The more mass an object has, the more it warps the universe. Anything that travels within the warped volume has to follow the warps -- it can't just go in a "straight line." If I sent a laser beam across the squirrely space in the illustration to the left, it would curve down into that bowl and arc back up the other side. 

 

 

We can often tell, if the curvature is significant enough, that light has had the traumatizing experience of riding the gravitational roller coaster on its way to our telescopes.

One way the evidence of curvature presents itself is called "gravitational lensing."

When spacetime is hella warped between a galaxy and our telescopes, the galaxy's image and position also appear warped (Credit: NASA).In the illustration to the right, we have a galaxy (upper right, with death lasers coming out of it) and a massive object (center, the blue glowing angel ball). The death lasers, grey, are the galaxy's light. As it nears the glowing angel ball, it can't follow a straight path because spacetime is not straight or flat. The spacetime acts like a lens, changing the projection that reaches Earth, similar to the way a regular magnifiying glass can project a distorted image of your eyeball.

Consequently, the image we see on Earth is much different from a nice, normal spiral. The orange "bananas," as NASA called them in its official caption, are what telescopes actually see. So the galaxy is not only a stretched-out fruit, but it has also turned into twins. The twin orange arrows show the galaxy's apparent position(s), different from the actual position, show by where the grey arrows land on Earth.

Sometimes, the stars galaxies align and make weird-looking images that happen to look like Earthly cultural icons. Sometimes they don't. It sounds like a lesson or a metaphor. You can pretend it is.

Friday
Feb222013

Black hole super(computer)models

by Sarah Scoles

This is a black hole's self-portrait.

Black holes are the strangest objects in the universe. Spaghettification, singularities, the speed of light's embarrassing status as "lower than the speed required to escape gravitation's pull." Black holes allow us to investigate the kinds of extreme science that we can't replicate here on Earth. Extreme mass, extreme spacetime curvature, extreme energy, extreme density, extreme gravitation.

Scientists like to test their ideas about mass, spacetime, energy, density, and gravitation on black holes and see how they hold up in this fringe case.

But before they can determine whether their theories produce results that hold up in the real world, they have to come up with what "holding up in the real world" looks like.

That's where models come in.

Yeah, sure. Those models. They come in. To a supercomputing facility. Sure.

 

Scientists have these theories (well-established explanations of how/why things happen in nature), and scientific theories provide predictions about how objects and forces behave in the real world. Sometimes, those predictions are simple to determine.

Newton's law of universal gravitation (okay, it's a law and not a theory, but you get my point), for instance, predicts that if I throw this banana toward the hallway, it will eventually fall to the ground. If the banana instead floated into my coworker's office, the real-world evidence would not match the prediction, we would all have to stop throwing bananas and take a second look at gravitation.

But somebody already did take another look at gravitation: Einstein, who made the theory of general relativity. While Newton's conception of gravity works for middleweights, it doesn't work for the extremes. It also has no idea about spacetime, though if Newton had somehow come up with the idea of some "fabric" of the universe warping all over the place, he probably would have freaked out.

To test Einstein, though, you can't just throw a banana around. It's not massive enough. It is, after all, just a fruit. In fact, we don't have anything lying around Earth that can test the edges of general relativity. Which is why we turn to black holes.

And models. Black holes and models.

Before scientists can find out whether black holes obey Einstein's theory, they have to figure out how a black hole obeying Einstein's theory would look. This is an example of a theory's implications being un-simple to sort out. 

To determine how a perfectly generally relativistic black hole would look, scientists have to use supercomputers like the ones at the Texas Advanced Computing Center, which, wouldn't you know, produced black-hole models published in a January Science paper.

The article "Alignment of Magnetized Accretion Disks and Relativistic Jets with Spinning Black Holes" has warped ideas about ...

... jets and accretion disks. 

Where is the black hole? In the middle of all that stuff. (Credit: NASA).

Jets and disks are made of fast-moving materials that is falling into (disks) or being shot away from (jets) the black hole. Because of the material's high energy and temperature and magnetic interactions, it emits radiation--X-rays, radio waves, gamma rays...the usual. The disk swirls around the black hole (which we can't see, as it's black), and the jets are perpendicular to it.

Or are they?

As a press release from the computing center says, "For decades, a simplistic view of the accretion disks and polar jets reigned. It was widely believed that accretion disks sat like flat plates along the outer edges of black holes and that jets shot straight out perpendicularly."

Not true, says this new study by J. McKinney, et al. They found the picture is not consistent at different distances from the black hole, and also that it is actually more like a movie than a picture.

Specifically, like this movie.

Where the jet is close to the black hole, it is aligned with the black hole's spin. For the parts of the jet that are farther away, though, the jet is parallel to the disk's rotation axis, an interaction that causes a warp in the disk itself. 

The scientists also turned up the magnetism, so that the field lines "threading" the black hole were as strong as the black hole's gravitation (read: curiously strong). When the field is this strong, it powers the jet. Which is potentially an answer to the age-old question, "What powers black hole jets?" The powerful jet then is so powerful that it can influence the disk, instead of only the other way around.

The paper's lead author provided a multi-metaphor quote that is potentially more confusing than enlightening but is funny nonetheless:

"People had thought that the disk was the dominant aspect," McKinney said. "It was the dog and the jet was the wagging tail. But we found that the magnetic field builds up to become stronger than gravity, and then the jet becomes the dog and the disk becomes the wagging tail. Or, one can say the dog is chasing its own tail, because the disk and jet are quite balanced, with the disk following the jet — it's the inverse situation to what people thought."

Yes, like that. 

So we have a theory, and we have a model of how that theory looks when applied in a specific situation.

Now what?

Test time! Time to look at a real black hole and see if it really looks like the supercomputed model. If it does, 1 point for the model and the theory. If it doesn't, perhaps the model is not complex enough or has a flaw, or maybe the theory has flaws. But using the Event Horizon Telescope, scientists will be able to look at actual gas around actual black holes and determine how model-like it is.

The only minor issue left to figure out is how the modeled black hole would actually look if you saw it through a telescope from billions of light-years away. It's the difference between seeing the paths of fast-moving matter, as we do in the simulation, and seeing the resultant photons, as we do through telescopes. As McKinney said, "We're in the process of making our simulations shine."

It puts a new meaning on the old song "Black Hole Sun."

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