SS Cygni: A red dwarf-white dwarf pair that's closer than scientists thought (or, how Hubble got told)

Determining distances to objects in space is no easy task, unless you're some kind of special person with an impossible faster-than-light spaceship and can just measure the miles between Earth and UDFj-39546284. This is what it's like to be in a helicopter above SS Cygni, minus the arrows and text (Credit: J. Miller-Jones [ICRAR], using software created by R. Hynes).But no astronomer I know has such a ship, and so they all are likely to say, "That galaxy is 3 billion light-years away, plus or minus a million light-years."

And that level of uncertainty doesn't apply only to far-away objects. It also applies to relatively nearby stars, such as SS Cygni, a close binary system in which a red dwarf and a white dwarf orbit each other every 6.6 hours. The Hubble Space Telescope had pegged the distance between us and SS Cygni at 540 light-years.

And, well, it's not often that you get to tell the Hubble Space Telescope it's wrong. But when the Hubble Space Telescope is wrong, you gotsta tell it loud and clear. So, "Hubble, SS Cygni is more like 372 light-years away. Take that in your face."

And what instruments were able to so diss the high-res space telescope? The Very Long Baseline Array (VLBA), a combination of 10 radio antennas spread between Hawaii and St. Croix, giving the telescope as a whole an effective diameter of more than 5,000 miles, and the European VLBI Network (EVN), which has antennas in Europe, China, Russia, and South Africa.

Here's the low-down on the SS Cygni system, how scientists used the VLBA to determine its distance from us, and why that 168 light-year revision matters.

What is this binary system like?

The solar flare in the upper left extends 100,000 miles from the Sun's surface, the same distance as the separate between SS Cygni's two stellar components.

Tight. The red and white dwarfs are separated by only 100,000ish miles. If the Sun were that close to another star, the star would begin just at the end of the solar flare in the image to the right.

Such a close sharing of quarters can lead to violent outbursts on the part of the white dwarf. The white dwarf roommate siphons material--Ramen noodles, the last of the Fruity Pebbles, clean underwear--from the red dwarf roommate, and all that stuff forms a disk around the white dwarf. When the white dwarf is taking a lot of material, the relationship is stable (and the analogy totally unravels), but when the transfer rate is lower, the disk destabilizes and undergoes an outburst. 

This burst happens with regularity--in the case of SS Cygni, once every 49ish days. Because of these explosions, it is categorized as a dwarf nova. It's only during the burst period that the system emits radio waves. 

But it didn't appear to work the same way all the other dwarf novae do.

This is what astronomers thought until today: SS Cygni is too bright. It's so bright that lots of mass must be changing hands. So much mass that the disk should always be stable. Meaning SS Cygni should never, ever have an outburst. But it does--often. If SS Cygni is in fact 500 light-years away, and is super bright but does the nova thing anyway, our theories about how dwarf novae work must be wrong.

So when amateur astronomers from the American Association of Variable Star Observers (AAVSO) noticed that it was, in fact, having an outburst, they informed professional astronomers, who perked up and took action because they were eager to prove that their theories were not, in fact, wrong.

When an object emits radio waves, and you have a 5,000-mile diameter radio telescope, you can do science. 

Who are these so called "professional astronomers," and what did they do with that gigantic telescope?

A team led by James Miller-Jones from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) took advantage of the radio emission to watch how it "wobbled" compared to the galaxies behind it (from our perspective).

"The wobble we were detecting is the equivalent of trying to see someone stand up in New York from as far as away as Sydney," Miller-Jones said in a press release.

Why couldn't astronomers do that any old time using the optical light, even if it's not emitting radio waves?

After all, SS Cygni is always putting out visible light.

"Our key advantage was using radio telescopes to observe the system. In visible light, optical telescopes like Hubble see hundreds of different stars, all of which are moving by different amounts, whereas in radio waves the background we compare against is much further away and therefore doesn't appear to move at all," co-author Assistant Professor Gregory Sivakoff from the University of Alberta, said.

Energetic radio galaxies were much more common at the beginning of the universe, so most are extremely far away.

Why are far-off things better for determining distance?

Astronomers were trying to find SS Cygni's parallax, which is the numerical measurement of the "wobble"--how much it appears to move relative to a distant background when the observer's position changes.

When you're looking out the passenger window of a car, the road's shoulder is flying by you, but the mountain peak moves slowly across your view. If we can measure the angle by which an object appears to move due to our motion, we can determine how far away it is--this is parallax.Parallax is based on the concept that objects close to you seem to "move" faster when you're moving than far-away objects do. I'm about to plagiarize myself here, but I'm being honest about it. "When you're looking out the passenger window of a car, the road's shoulder is flying by you, but the mountain peak moves slowly across your view." Because of that differential, astronomers can measure the difference between how the "shoulder"and the "mountain peak" change relative to each other and thus determine how far away the "shoulder" is.

Wikipedia user Natejunk2004, aka Best Screen-Named Person Ever, made this animation demonstrating what I clumsily tried to convey above.

Miller-Jones, et al., looked at SS Cygni when Earth was at different, widely separated points in its orbit (see the figure to the left) and observed where it was relative to background radio galaxies from each of those perspectives. The radio galaxies, by the way, are so distant that they don't seem to move at all.

So they used parallax to figure out that SS Cygni is 168 light-years closer than they'd previously thought. So what?

Well, if SS Cygni is closer to us, it's not quite as intrinsically bright as scientists thought. It's just nearby (in the same way that the Sun seems to be really bright compared to Sirius but is really just average and next-door). Which means that the mass transfer rate is low enough to create an unstable disk. Which means that astronomers were right about dwarf novae (or, at least, that they weren't wrong in this particular way).

And we all know how astronomers love to be right. Right?

But, really, using evidence to prove that a physical process does mesh with a theory is truly a significant scientific feat. It is, in fact, what science is all about.

How to see a black hole birth

by Sarah Scoles

What if this was what you did to the space around you? How would you feel? Well, scientists can't answer that, but they now may be able to tell when a black hole is forming. even if its stellar progenitor doesn't explode (Credit: Alain Riazuelo, IAP/UPMC/CNRS).

When really massive stars die, they collapse into black holes. But no one has actually observed this process in action. So what happens, exactly, when a star stops being a star and starts being the universe's weirdest object? How does it look, and what signals would allow scientists to point at some tiny spot in the sky and say, "Hey, right there, a black hole was just born"?

A new paper suggests one such signal, and, almost as importantly, this paper has a great title: "Taking the 'Un' out of 'Unnovae.'" Good job, sole author theoretical astrophysics postdoctoral researcher Anthony L. Piro.

Piro suggests that the death of a star and the subsequent birth of a black hole--the Simba-style circle of cosmic life--is marked by a specific type of flash.

Wait, did you just use the word 'unnova' and proceed to write another sentence before defining it?

Sorry. While some stars-turning-black-holes produce spectacular explosions that are supernovae or supernova-like and/or include ultra-energetic gamma-ray bursts, others may simply implode and disappear without all the fanfare. This "now it's there, now it's not" version is the theoretical-and-as-yet-unobserved unnova. As in, not a nova.

But it is something, even if it is not a nova. When a massive star is turning into a black hole, it collapses into a neutron star first, its protons and electrons so squished together that they combine into neutrons. As the star is essentially cramming itself into a medium-sized city's limits, it is also releasing neutrinos--nearly massless particles that travel almost as fast as light and don't interact much with the rest of the universe. As a result, the star loses about a tenth of its mass in the course of a few seconds.

Consider losing a tenth of your mass. Like you would, the star feels its loss of gravitational strength. While you would probably just run faster or jump higher or be really hungry, the star can no longer hold on to its outer layers. As they expand, they create a shock wave in the star's envelope, which is consequently ejected. When the wave reaches the star's surface, the surface heats up and glows. It's a bit like a slow-mo, low-energy supernova...which is not a supernova at all and is, in fact, an unnova. The resulting light, though it would last for about a year, is too faint for our telescopes to reliably identify at the moment.

Piro's paper asks the question, "Is there a brighter signature within the unnova-ing process that scientists could latch onto?"

The short answer: Yes! A flash.

The longer answer: When the shock wave hits the star's surface, he predicts there will be a blast of light. Not nearly as bright as a supernova, but 10-100 (I know, I know, check out that range) times brighter than the "glow."

In other words, if scientists can find instances of this flash, which Piro estimates should occur detectably once per year, they will be able to say, "Look at that unnova! Probably," and will suspect that they have seen a black hole being born. And who doesn't want to be in the delivery room to witness that?

All of a sudden, this emerges from the dying massive star, and everybody's like, "What?" (Credit: DC Comics).

Stats on the flash:

• it would last 3-10 days (so "flash" is perhaps not the best word to describe it, except to astronomers, who think on million-year timescales at the smallest)
• it would equate to a temperature of 10,000 kelvin, or 17,540F
• it would travel at a max speed of 200 km/second or 124 miles/second
• it wouldn't show any evidence of nuclear synthesis, but hydrogen would be prevalent
• it would have a luminosity of 10^40-41 ergs/second, or 2.6 million-26 million times as bright as the Sun
• it would be brightest in UV light but a similarly strong blue component

So keep your transient-identifying, world-class UV-sensitive telescope's eyes open, and maybe you'll be the first one to see a black hole progenitor's final moments, before it Houdinis itself out of the visible universe.

Piro, A. (2013). TAKING THE “UN” OUT OF “UNNOVAE” The Astrophysical Journal, 768 (1) DOI: 10.1088/2041-8205/768/1/L14

Learning: What’s programmed cell-death proteins got to do with it?

by Brooke Napier

A. Healthy Cell :) B. Apoptotic Cell :(Apoptosis is programmed cell death. It is controlled cellular suicide that is responsible for humans not having webbed fingers.  Less dramatically this time - apoptosis effectively and efficiently removes extra and unnecessary cells during development.

Cellular proteins called caspases control apoptosis. Caspases are a family of proteins known as cysteine proteases and they mediate cell suicide by forming protein complexes with activating complexes in the presence of adaptor proteins. They cleave other caspases and other cellular substrates to orchestrate a very controlled cellular destruction.

Humans encode 11 caspases, and while most of them dedicate their folded-life to carrying out apoptosis, some caspases have been known to dabble in immune regulation (ex: containing inflammation during infection to the site of infection) and spermatogenesis (you’ll have to ask a sperm-centric Ph.D. candidate about this one).

Mouse interdigits in utero - red cells are apoptotic. Fingers, ya'll!Although I have previously emphasized the importance of apoptosis/caspases in the development of our digits (I <3 my thumbs), ANTI-apoptotic molecules (members of the BCL-2 family) are extremely important during the development of the brain. There is relatively little turnover in the brain, so maintenance of differentiated neurons (peripheral neurons specifically) is very important.

Since apoptosis is specifically down-regulated in many neurons, one would assume that after development of the human brain caspase proteins are no longer needed in a healthy human. But then why have so many researchers found that caspases are required normal, everyday neural functions?

Caspases are serving a completely different function in the healthy adult human brain.

Ah ha! It turns out caspases can also dabble in other, very important neuronal functions. In fact there is data showing that activation of caspases in neurons can control normal neural physiology.

What are the new roles for caspases in neural physiology?

Ye ole dendrite. Gorgeous as ever.

1) Dendritic pruning, or trimming the hedges, if you will. Dendrites (from the word tree in Greek) are beautifully branched neurons that transmit electrochemical stimulation from other neural cells to the soma, or cell body, of the dendrite, which then makes the executive decision to pass on the electrochemical signals to more dendrites via neurochemical synapses. This is the beautiful orchestra that is neuron-to-neuron communication in the nervous system.

Pruning of the dendrites is important for normal brain functions, it removes neglected or misguided dendritic branches, which would normally get in the way of forming fresh, new, sparkly synapses. Just like learning, the formation of our neural connections are fluid, and caspases grease the spokes.  This mechanism of plasticity is as important as it sounds; Caspase 3 has been implicated in the zebra finch and fly models of learning and memory.

2) Axon guidance and synaptogenesis. Basically if you make a mouse that is caspase-deficient you have successfully made a mouse that has defects in axon targeting and synapase formation during development, which leads to significant developmental delays.

After poking my nose into this research, it seems like not a lot is understood about how caspases effect axon guidance or synapse generation – but there is preliminary data that suggests without some specific caspases axons show delayed/misguided maturation and some proteins required for synapse generation are impaired.

3) Normal synaptic physiology, turns out low levels of caspase 3 activation are required for synaptic changes that underlie memory.

Related, long-term depression (LTD), where synapses become less sensitive to stimulus (and the dendritic branches shrink or get eliminated), is associated with local activation of Caspase 3. Turns out, if you block caspase 3 or 9 activation you can effectively stop LTD! Follow the Figure legend below to learn more about this mechanism.

Too bad we can prescribe caspase 3 inhibitors for patients diagnosed with LTD (remember all the other things caspases do?).

The once infamous rapid-cell-death associated family of proteins has now relinquished its former title and should now be referred to as: Caspases: the we-can-help-you-learn family of proteins. In the words of Bradley Hyman and Junying Yuan:

“In addition to being a signal of acute, inexorable death, caspase activation in other circumstances (at least within the CNS) might instead be a pivotal event for responding to ever-changing environmental stimuli.”

Hyman, B., & Yuan, J. (2012). Apoptotic and non-apoptotic roles of caspases in neuronal physiology and pathophysiology Nature Reviews Neuroscience, 13 (6), 395-406 DOI: 10.1038/nrn3228

Bursting the bubble around "water worlds" Kepler-62e and -62f

by Sarah Scoles

Recently in the astronomy world, a press release about exoplanets -- and the news reports that subsequently tumbled out into the world -- committed a faux pas: overstating the conclusion of a scientific paper.

On April 18, the Harvard-Smithsonian Center for Astrophysics issued a press release entitled "Two Water Worlds for the Price of One."

First of all, what price?This is how much an exoplanet costs. This is why you got socks for Christmas (Credit: 123rf).

Second of all, the actual scientific paper does not ever say the planets are water worlds.

The press release says:

• "Modeling by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) suggests that both planets are water worlds, their surfaces completely covered by a global ocean with no land in sight."

And the lead author's direct quote in the press release is:

• "'These planets are unlike anything in our solar system. They have endless oceans.'"

Not to be so 2004, but ORLY? I got this original ORLY owl from a place that gives Myspace embed codes. That's outdated this meme is.

In "Water planets in the habitable zone: Atmospheric chemistry, observable features, and the case of Kepler-62e and -62f," to be published in a future issue of The Astrophysical Journal, the authors are not trying to prove that 62e and 62f are awash in Caribbean beauty (without the beach umbrellas). The paper takes an idea -- that water planets in the habitable zone (HZ) can exist -- and presents a model for how they could exist, how their atmospheres and oceans would interact, and how we could tell from thousands of light-years away that Earth-sized orbs were not dirty deserts but "beautiful blue planets" (Kaltenegger).

Within the paper, the team then tests their model using 62e and 62f. The authors essentially ask, "Hey, what characteristics would these planets need to have hypothetical 'endless oceans'? And by tweaking that list of available characteristics can we actually make our models of these two planets acquire and maintain 'endless oceans'? All within the framework of the assumptions we made about planets that have endless oceans?"

What the paper did not ask is, "Do these planets have endless oceans?" What it did ask was, "Could they, and would we be able to tell?"

The answer the authors come up with is, "Yes, ma'am." 62e and 62f could be water planets. They are "the first viable candidates," given their diameters and their distances from their star.

But paper states, "Other possibilities remain open until their actual masses are measured." And in a Science paper reporting the planets' actual discovery, the authors say, "Theoretical models of Kepler-62e and -62f ... suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk" (Borucki, et al., 2013).

It's cool that they're Earthish-sized and in the habitable zone! It's cool that they could work as water planets, if we "assume they are indeed water planets with low-eccentricity orbits" (Kaltenegger, et al., 2013). It's really cool! 

But that is not what the CfA's press release said, not what the batted-around, poetical quote says, and not the general character of the news releases based on the press release/conference. Oddly, no one mentioned whether the model of planetary CO2 cycling included Kevin Costner (Credit: Waterworld).

Here's the flavor of the coverage:

Press release: But what if our Sun had not one but two habitable ocean worlds? Astronomers have found such a planetary system orbiting the star Kepler-62. 

Space.com: Computer models suggest both planets are covered by uninterrupted oceans.

Huffington Post: While nobody knows what the two exoplanets look like, a separate modeling study suggests they're both probably water worlds covered by endless, uninterrupted global oceans.

Wired.com: Endless oceans cover newly discovered, possibly habitable, planets.

Some articles expressed such certitude about the planets' wetness and then later said, without finding the statements contradictory, that all of this was hypothetical pending more information. Time magazine was reliable and admitted, "Borucki and the other Kepler scientists were quick to say they had no direct evidence that either planet actually has liquid water on its surface."

What to do?

I'm all for presenting scientific results in such a way that people become excited about them. That is, after all, the point of this blog. But science is our very human attempt to find out the truth about the universe. And exaggerating claims, even if it makes some teenager in Freeport, Kansas (pop: 6), run upstairs to her mom and proclaim that science is awesome she wants to become the most successful exoplanet hunter ever when she grows up and her mom decides to donate the $1 billion inheritance she got when her grandfather died to the Kepler space telescope's successor -- even if exaggeration leads to such grand results, it's not the way we should be talking about scientific results. 

As surgeon/scientist/blogger Orac said in a post entitled "Misrepresenting Science" on his ScienceBlog, "[Scientists] want to justify the press release. Too many caveats and cautions make our work sound less important (or, more accurately, less certain) to a lay audience, and if it’s one thing that’s hard to explain to a lay audience it’s the inherent uncertainty in science. We can’t avoid that; we have to embrace it and work to explain it to the public."

Better to say, "Look, scientists are figuring out how to tell what other planets are made of. Isn't that cool? Aren't you excited? And these planets? They might not be so different from ours. Someday we'll know more. For now, we found out that they could be covered in water. Regardless of what they're wrapped in, they're a present from Kepler, and we'll take them."

Just as we will take Kepler's next discoveries -- which will surely be of even smaller, even more habitably zoned, even bluer or greener or browner, even BETTER exoplanets.

In the meantime, let's go lasso an asteroid.

L. Kaltenegger, D. Sasselov, & S. Rugheimer (2013). Water Planets in the Habitable Zone: Atmospheric Chemistry, Observable Features, and the case of Kepler-62e and -62f The Astrophysical Journal DOI: arXiv:1304.5058v1

Borucki, W., Agol, E., Fressin, F., Kaltenegger, L., Rowe, J., Isaacson, H., Fischer, D., Batalha, N., Lissauer, J., Marcy, G., Fabrycky, D., Desert, J., Bryson, S., Barclay, T., Bastien, F., Boss, A., Brugamyer, E., Buchhave, L., Burke, C., Caldwell, D., Carter, J., Charbonneau, D., Crepp, J., Christensen-Dalsgaard, J., Christiansen, J., Ciardi, D., Cochran, W., DeVore, E., Doyle, L., Dupree, A., Endl, M., Everett, M., Ford, E., Fortney, J., Gautier, T., Geary, J., Gould, A., Haas, M., Henze, C., Howard, A., Howell, S., Huber, D., Jenkins, J., Kjeldsen, H., Kolbl, R., Kolodziejczak, J., Latham, D., Lee, B., Lopez, E., Mullally, F., Orosz, J., Prsa, A., Quintana, E., Sanchis-Ojeda, R., Sasselov, D., Seader, S., Shporer, A., Steffen, J., Still, M., Tenenbaum, P., Thompson, S., Torres, G., Twicken, J., Welsh, W., & Winn, J. (2013). Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone Science DOI: 10.1126/science.1234702

Science Highlights: Neuro-Addition

By Brooke Napier

These next few stories are going to remind you why neuroscience is so cool, as if we don’t always do that on this blog…

Bench-pressing neurons

The minute I learned that we have a neuron that stretches up to a meter long from our spine to our toes I became extremely nervous to bend over too fast or to do the splits, scared that I could rupture a neuron. But then again, who has ever heard of a ruptured leg neuron?

Ok, so maybe theirs is longer than ours... but they shouldn't be doing splits either.What keeps neurons this long sturdy enough to not tear or break while humans go along their dynamic everyday lives?

Yuyu Song et al. published in Neuron last week that the microtubules, a main component of the cytoskeleton in cells, in neurons are more “sturdy” than microtubules found in any non-neuronal cell type. Generally, microtubules are constantly undergoing rearrangements, building up and building down the cytoskeleton of the cell in order to support the dynamic cellular lifestyle; however, neuronal microtubules are unusually stable.

The secret to the stability is modification to the microtubule structure by the addition of polyamines, positively charged molecules, in the weak sites of the microtubules. These researchers also found the enzyme transglutaminase was responsible for this modification of the microtubules.

Interestingly, the stability of microtubules increases with age and correlates with lower neuronal plasticity, which can be detrimental if you consider we’re always aging, but we’re also at higher risk of neurodegenerative disease as we age – therefore, with increased neuronal stability you also get an unwanted side-affect of not being able to recover fully from neuron damage or neurodegeneration.

Can we block neural stability to increase recovery from neuron damage? I guess we’ll have to see in their next paper.

Primary article: Transglutaminase and Polyamination of Tubulin: Posttranslational Modification for Stabilizing Axonal Microtubules, Neuron, 2013

Pavlov says tasting beer (without alcohol) makes you happy

Too real? Yeah, probably.Brandon Oberlin, et al. published in Neuropsychology that the taste of beer induces a release of dopamine (in the absence of alcohol) in 49 men, ranging from social to heavy drinking, with a mean age of 25. After administering beer flavor (or Gatorade, as a control) there was a significant increase in desire to drink, as reported by the subjects, and induced dopamine release.  Sadly, larger inductions of dopamine were seen in subjects with first-degree alcoholic relatives.

Therefore, the taste of beer not only makes people want to drink more, but the taste of beer triggering this need is genetic. 

Pavlov isn’t so funny when it’s us and not dogs.

Primary article: Oberlin, B., Dzemidzic, M., Tran, S., Soeurt, C., Albrecht, D., Yoder, K., & Kareken, D. (2013). Beer Flavor Provokes Striatal Dopamine Release in Male Drinkers: Mediation by Family History of Alcoholism Neuropsychopharmacology DOI: 10.1038/npp.2013.91

New Insight into Schizophrenia

When I was in college (it was only 6 years ago, sheesh) we learned that people with schizophrenia had increased levels of dopamine – that was it. By the time I was graduating college I remember a paper coming out saying that there was increased neurodegeneration (or neuronal atrophy) in multiple portions of the brain in people with schizophrenia. Now, meaning probably right now, people are now understanding this architecture of the schizophrenic brain will tell us something if we listen.

We are twins. (Left) Healthy twin, (right) schizophrenic twin. Note the big, black empty spaces (atrophy) in the right brain.Researchers new that the hippocampus, the area of the brain that is involved in long-term and short-term memory, has increased metabolism and reduced size in schizophrenic patients. Scott Schobel, et al. hypothesized that these two symptoms may be related and this might shed light on the mechanisms behind schizophrenia. He suggested that perhaps the elevations of extracellular glutamate (due to increased metabolism) might drive the tissue atrophy – he was right.

Their mouse model of schizophrenia included administration of the N-methyl-D-aspartate (NMDA) receptor agonist, ketamine (Special K, anyone?), that induces positive and negative symptoms of schnizophrenia. In this model, they mapped extracellular glutamate within the hippocampus and used “postmortem analysis” (cutting open the brain?) to map the atrophied areas of the hippocampus within the same mice, and found that these areas overlapped significantly. Not only that, but the glutamate-driven hypermetabolism occurred before the atrophy.

This data has not only revealed a potential mechanism of disease, but also this increase hypermetabolism could be potentially be used as a biomarker for early psychotic disorders, like schizophrenia.

Primary article: Imaging Patients with Psychosis and a Mouse Model Establishes a Spreading Pattern of Hippocampal Dysfunction and Implicates Glutamate as a Driver, Neuron, 2013