Tuesday
Apr232013

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 That's outdated this meme is.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.

ResearchBlogging.orgL. 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

Tuesday
Apr162013

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

 

 

 

Tuesday
Apr092013

Baby stars around black hole's womb: The story of Sagittarius A* and its protostellar companions

by Sarah Scoles

You've heard it a billion times: Don't go near the supermassive black hole. You'll  shoot your eye out have your entire body stretched into spaghetti-thinness like Mike Teavee post-Television Room. And the same is true for molecular gas that would like to turn itself into stars.

Please don't forget the lessons I have taught you (Credit: Willy Wonka and the Chocolate Factory)Generally, if you are a cloud of molecular gas with ambition to become something more, you'd be well-advised to steer clear of shearing gravitational fields, such as those surrounding the most dense and extreme objects in the universe. Duh.

Or maybe not?
Observations from the new ALMA (Atacama Large Millimeter Array) telescope and CARMA (Combined Array for Research in Millimeter-wave Astronomy) show that fetal stars are gestating while snuggled up against Sagittarius A*, the black hole at the center of the Milky Way, which is a respectable 4 million times the mass of our Sun.

Scientists believed that stars could not form so close to such a massive object, as the effects of its gravity should prevent clouds of molecular gas -- the combined egg/sperm that leads to star formation -- from collapsing under their own gravity to form self-adhesive spheres of plasma.

The data
They believed it was impossible, at least, until they made a detailed map of the millimeter-wave photons coming from right around Sagittarius A*. In this map, they saw the characteristic signal of the compound SiO -- the aptly named silicon monoxide. And the SiO was clumped together in clumps. Eleven distinct and identifiable clumps. They look like and move like this:

Silicon monoxide clumps 1-11 are labeled in this map of the galactic center. Some of the clumps were even lucky enough to have their velocities measured, which is what the plots artistically surrounding the map show (Yusef-Zadeh, et al., 2013)Scientists see SiO where protostars -- objects that are not yet stars but are well on their way -- are shooting "I'm here!" jets into space. The protostars' energy excites the molecules and make them glow at specific wavelengths.

When the astronomers saw the SiO evidence that protostellar jets, and thus protostars, were forming so close to a supermassive black hole, they thought, "Huh?" and then decided to try to answer that question before publishing a paper and then publish a paper with the answer.

The conclusions
For any star -- whether it's next to a supermassive black hole or not -- to form, a cloud of molecular gas has to collapse and become denser and denser and hotter and hotter until it is dense and hot enough to hold itself together and begin nuclear fusion.

Near a supermassive black hole, astronomers thought the shearing gravitation -- tidal forces -- would prevent molecular gas from collapsing, because the gravitational effect of the black hole would always be more than the gravitational effects of molecules on each other.

But when actual empirical evidence contradicts what you made up in your head and on paper/hard drive, you have to adjust what's in your head, because those protostars are way too far away to be adjusted in a reasonable amount of time, and also you'll shoot your eye out.

In their paper (cited below), the researchers put forth two explanations:

  1. Clump-clump collisions: Small clumps of gas were able to form, and then they accidentally hit each other and stuck together, and as more and more clumps stuck to them, they became massive enough for their internal gravity to take over. The problem with this idea is that it requires 60 individual initial clumps.
  2. UV compression: There's a significant UV radiation field around Sagittarius A*. The radiation causes pressure, which can cause compression, which can cause clumps of gas to collapse. The only problem with this explanation is that it takes 50,000 straight years of UV compression to give a clump the kind of mass and collapse that allow its own gravity to win.

So there are problems with both models. There are problems with most models.

Not that dapper Harry Stiles of One Direction is a model, but, you know, you get my point. My point being that Photoshop is amazing and scientific models, like models of teenage popstardom, are rarely perfect.But at least they came up with some ideas, and they (or other teams) can investigate clump-clump collision and UV compression in other situations and on hellasupercomputers to see if tweaking the terms leads to scientific expectations that better match scientific data.

While they do that, you can think about how

  • these protostars formed in the past 100,000-1,000,000 years. Whenever I hear numbers like that in astronomy, it makes me sit up and hit my head on something and listen. Because in terms of the universe, 100,000 years ago might as well be right now. I mean, dude, Homo sapiens existed then.
  • they are big! One is more than 30 times more massive than the Sun is.
  • they are bright! One is more than 40,000 times more luminous than the Sun is.
  • they are hanging out around a gigantic pit of superdense nothingness that has ripped spacetime. If only they could speak, they could tell us what this black hole has been doing while the modern hominid species has been flitting about planet Earth. But they can't. So we'll just have to keep doing science.

 

ResearchBlogging.org F. Yusef-Zadeh, M. Royster, M. Wardle, R. Arendt, H. Bushouse, D. C. Lis, M. W. Pound, D. A. Roberts, B. Whitney, & A. Wootten (2013). ALMA Observations of the Galactic Center: SiO Outflows and High Mass Star Formation near Sgr A* The Astrophysical Journal Letters arXiv: 1303.3403v1

Thursday
Apr042013

You are what you eat, when you're 1 day old.

by Brooke Napier

Experiences in my childhood have resulted in me not liking mayonnaise, being scared of bathrooms without windows, and apparently the sensitivity of my colon to inflammation.I'm dead serious about this hate.

The idea of exposure to certain microbes affecting your adult life isn’t a new one, it’s called the “hygiene hypothesis”, which proposes that early-life exposure to specific microbes can result in a lower susceptibility to diseases such as inflammatory bowel disease (IBD) and asthma.

Basically, we (Americans specifically) are so clean as babies we’re making ourselves sick as adults.

But how are these two things tied together?

How does exposure to microbes as a baby influence your susceptibility to colon disease?

There have been tons of studies trying to answer these questions, but I found a beautiful article published in Science Magazine one year ago that enlightens the field by showing that microbial exposure at a young age (think the age of 1 day) can teach your immune system to avoid inflammatory disease in the colon as an adult.

Let’s break-it-down:

They already knew:

Previous epidemiological studies have already shown that exposure to microbes and a very young age is associated with lowered frequencies of immune-mediated inflammatory bowel disease (IBD).

They also knew that after birth, the gut is one of the first sites of microbial contact with human cells.

Basically, they knew there was a super interesting correlation between microbial exposures early in life equals less inflammation in the gut as an adult, but they had no idea why these two things would be correlated.

So what did they do to look at this correlation?

There are two major players in their study, Germ-Free (GF) mice and specific pathogen-free (SPF) mice. GF mice do not have any commensal bacteria in their gut, or anywhere, they’ve never seen a bacterium in their life. SPF mice have normal commensal bacterial cultures.

This is what Germ-Free (GF) mice live in. Yes, they are basically the bubble boy.

There are TONS of differences between these two mice, however this group of researchers was particularly interested in the difference they saw of a cell type that accumulates in the colonic lamina propria (da gut, yo) when the mice has ulcerative colitis.  They can induce ulcerative colitis in mice by administering a chemical that basically beats-up the epithelial lining of the gut, mimicking ulcers.

The infamous (or inflammous, har har) cell type associated with increased inflammation in the gut during this colitis model is known as invariant natural killer T (iNKT) cells.

invariant natural killer T-cell - it looks pretty menacing, don't you think?

Scared yet? I am.

Basically where there are more iNKT cells there is more inflammation, so the fact that GF mice had swarms of these cells in their gut meant that when GF mice had ulcerative colitis they died more frequently, or if not had worse symptoms, then SPF mice that also had ulcerative colitis (but less iNKT cells).

They go on to find that if they take GF mice (with no commensals) and expose them to microbiota at their first day of life they can reduce the frequency of iNKT cells in the gut during inflammation, and this is true throughout the rest of the mouse’s life.

However, when they exposed adult GF mice to microbiota they could not decrease the number of iNKT cells that were in the gut during inflammation – it was too late, the path was already paved for those mice.

Basically, super early exposure to microbiota led to a decrease in a life-time of gut inflammation due to lowered numbers of iNKT cells.

But why are there more iNKT cells in GF mice compared to SPF mice during inflammation of the gut?

Good question, they say.

What they found was that CXCL16, basically a molecule that beckons iNKT cells to the place of inflammation when they’re needed is extremely high in GF mice compared to their SPF friends. This means that the microbes in your colon are directing traffic of inflammatory cells (iNKT cells) by influencing the levels of molecules that attract them!

How can the microbiota tell the human cell to produce CXCL16 in order to influence the iNKT cells to migrate to the colon?

Your DNA is wrapped tightly around what is essentially a group of little protein balls (histones) that have tons of little repressor molecules (called methyl groups) that bind the DNA to the histones. When DNA is wrapped tight around these heavily methylated histones there is no access to the genes, therefore genes cannot be expressed.However, with the modification of removing some methyl groups, the DNA will loosen from around the histones and allow the appropriate machinery to access those genes and be expressed.

This is the bread and butter of eukaryotic genetics, in this one tiny picture.

This group of profound scientific researchers found that under GF conditions the gene that encodes cxcl16 is hypermethylated, therefore there is tons of gene expression, THEREFORE there is tons of the CXCL16 protein being produced and when there is CXCL16 there are iNKT cells!

Not to anyone’s surprise, when you add back SPF microbiota to neonatal GF mice you no longer see this hypermethylation of the cxcl16 gene, therefore there is no expression of cxcl16 = no iNKT cells = no inflammation = no hurry up go the bathroom dance!

These data really drive home the idea that the first moments of our life can influence our adult lives in more ways then we can imagine.

It also drives home the “hygiene hypothesis”, which proposes that early-life exposure to specific microbe-enriched environments decreases susceptibility to diseases such as IBD and asthma. 

 

 

 

 

 

ResearchBlogging.org Olszak T, An D, Zeissig S, Vera MP, Richter J, Franke A, Glickman JN, Siebert R, Baron RM, Kasper DL, & Blumberg RS (2012). Microbial exposure during early life has persistent effects on natural killer T cell function. Science (New York, N.Y.), 336 (6080), 489-93 PMID: 22442383

Wednesday
Mar272013

Background this, background that: Planck, C-BASS, and the history of the universe

by Sarah Scoles


This is where you live (Credit: ESA/Planck).On March 21, the Planck space telescope team released their first round of data, which reveals (or, rather, clarifies and gives more precision to previously researched) secrets of the early, early universe. The European Space Agency-run mission looks at the cosmic microwave background (CMB) radiation--the earliest light we can possibly see from the timeline of the universe. Telescopes like Planck look for tiny fluctuations in the CMB. These peaks and valleys in the cosmos' baby picture eventually grew into clusters, galaxies, stars.

 

From the state of the universe in this old portrait, scientists can figure out how old it is now and what it's made of.

I won't go into detail about the process or meaning of the results, as many have already (Discover, JPL, Nature, Cosmic Log NBC, NYT Science), but the summary is that the universe

  • is 13.8 and not 13.77 billion years old.It's so dark in here (Credit: ESA/Planck).
  • is 26.8 percent and not 24 percent dark matter.
  • is 68.3 percent and not 71.4 percent dark energy.
  • is 4.9 percent and not 4.6 percent regular matter.
  • has a Hubble constant (which descibes its expansion) of 67.15 and not 69.32 km/s/Mpc

In short, it's still expanding really fast, it's still really old, and it's still really dark and handsome and mysterious.

But are these numbers final?

(Are any numbers final? Does your life have any stability?)

The calculations are based on the first 15.5 months of Planck data, or 10% of the amount scientists plan to gather before 2014. 

This is where all the stuff we can see is. Lighter = more regular matter. The line in the middle is the plane of our Galaxy, removed (Credit: ESA/NASA/JPL-Caltech).Right now, the Planck results mostly deal with how bright the CMB is and not its more subtle characteristics. Later, the team will tell us all about the ancient light's polarization--the orientations of the light waves. Do they look up-and-down perpendicular to the way the light is moving? Are they all arranged that way? Or are they randomly jumbled in all directions?

The conditions of the universe in its earliest state determine the directions the light waves are oscillating, so from observing the CMB's polarization, scientists can learn about what our home-verse was like right after the Big Bang. Specifically, they are interested in seeing how well the waves have lined up into the same polarizations and what/where deviations are. Deviations, in this case, come from gravitational waves travling through and variations in the density of the early universe.

But our home galaxy gets in the way of our exploration of the larger world outside the nest.

The Milky Way's radiation obscures the polarized CMB signal. UH OH. In order to figure out what's from the old universe and what's from annoying gasduststarsprocesses nearby, all of the annoying nearby stuff must be subtracted out, leaving behind a pristine CMB signal. To do that subtraction, though, scientists will have to know exactly what our galaxy's polarized signals look like.

And the team in charge of a new telescope called C-Bass says, "We'll halp."

C-Bass stands for "C-band all-sky survey," where C-band means the longer end of the microwave spectrum.

Dr Angela Taylor of Oxford University said in a press release: "C-BASS acts like an extra frequency channel for Planck, hugely extending the range of radio wavelengths we have available. C-BASS will measure the polarization signal from our galaxy with great accuracy, and will hugely improve our ability to remove the galactic signal from Planck data, revealing the true CMB signal."

C-BASS is made of two telescopes--one in the Northern hemisphere (California) and one in the Southern (Johannesburg)--originally meant to talk to satellites. They have now been repurposed to do science instead of communicate. They will take pictures of the whole sky's longer microwave emission, which will provide a map of Milky contamination.

After that, and after, you know, many more years of Planck data, we'll take a look at all those revised numbers again. Though we won't find that--gasp--the universe is only 5% dark energy or anything crazy like that, some 1s and 1/10ths digits may change.