Bad Astronomy
The entire universe in blog form

March 4 2015 9:42 AM

Healthy Google

Sometimes, it’s the little things.

I got an email the other day from someone who works with Google, telling me some cool news: They’ve updated their search results about health conditions. They now provide information that’s curated and vetted by doctors, including the Mayo Clinic!


That’s fantastic. So, for example, when you Google “measles,” the first couple of results are (as usual) news items, then links to the Centers for Disease Control and Prevention, the Mayo Clinic, and Wikipedia. I'll note that when I dug down a few pages in the results list, there still wasn't a single anti-vax site to be seen. Nice.

Another good part is that off to the right there's added information called a "Knowledge Graph" by Google (I took a screengrab, shown above). You can get more about symptoms and treatments, and under a drawing of someone with measles is this wonderful line:

A viral infection that’s serious for small children but is easily preventable by a vaccine.

Emphasis mine. That’s great. Little tidbits like that used casually—especially by Google—can go a long way toward marginalizing views that damn well ought to be marginalized. On the Google blog (linked above), they say that 1 in 20 searches are for health issues, so this update by them is hopefully going to have a very long reach.

I’ll note that Google contacted me because they saw my article about Kristen Bell advocating for vaccination. That too makes me happy. As you can imagine, the comments I get whenever I post about vaccines (in the blog comments as well as on Twitter and Facebook) are not always reality-based. It’s really great to know that Google is on the side of science. That’s not a surprise, but it’s still nice to see them doing their part. They obviously have a vast amount of leverage, and they’re using their powers here for good.

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March 3 2015 12:00 PM

Rosetta Sees Its Shadow on a Comet

I suppose, if you want to be traditional about it, Valentine’s Day is a good time to get as close as you can to the one you love. That may be why the Rosetta space probe dipped to a mere 6 kilometers from the surface of the comet 67P/Churyumov-Gerasimenko on Feb. 14, 2015.

When it did, it saw something remarkable: Its own shadow on the surface of the comet!


I guess that means six more weeks of winter for 67/P. Of course, when your temperature is -70 C, it’s always winter.

A few weeks ago, Rosetta began a series of maneuvers that would take it very close to the comet’s surface, as well as several swings that would take it much farther away. The idea is to sample the environment around the comet in different places to see how things change.

At one point in the low pass, the Sun was directly behind Rosetta, so its shadow was cast on the surface. The spacecraft itself is a boxy shape roughly two meters on a side but has solar panels that extend 16 meters across, which is why the shadow is rectangular. It’s fuzzy because the Sun isn’t a point source—if you were on the comet looking up at Rosetta, it would only be blocking part of the Sun, so the shadow isn’t as deep where the Sun isn’t completely blocked. The same thing happens with eclipses here on Earth.

penumbra shadow
If the Sun were a point source (left) the shadow would be sharp. Instead, it's extended (right) creating a fuzzier shadow.

Drawing by ESA

You can also see a brighter halo around the shadow. That’s called the opposition effect (or opposition surge or—my favorite—heiligenschein). Think of it this way: When the Sun is off to the side, you can see objects and their shadows. But if the Sun is directly behind you when you look at the ground, the shadow of, say, a rock falls behind it, and you can’t see it. On average the scene in that direction looks brighter.

Also, there’s a peculiar property of small grains that they can preferentially scatter light back in the direction it came. If the Sun is directly behind you, that means the light gets sent back at your eyes, making the ground look brighter. Look at dewy grass in the early morning (or dust in a baseball diamond, or similar areas covered in fine particles) and you’ll see a bright halo around your head. That’s heiligenschein.

The brightness of the halo depends a bit on the size of the particles doing the scattering, and that can be used to figure out the sizes of particles on the comet’s surface. So this picture of Rosetta’s shadow is more than just cool: It’s science.

That makes it extra cool.

And the detail! The image is a remarkable 228 meters on a side, the size of a big (American) football stadium. Think of those aerial shots you see during a game, and how you can see people sitting in their seats: That’s about the same scale as this shot. The resolution in the raw data is a stunning 11 cm per pixel. That’s the width of my hand (including my thumb). Wow.

And this mission is still in the early stages. Rosetta will follow 67/P for many more months to come, studying the comet as it nears the Sun. As it does, water ice mixed in with dust on the surface will turn even more vigorously into gas, and the comet will become more active. We’ve never been so close to a comet for so long as it does this. What amazing things will we see in the coming months?

March 3 2015 7:30 AM

The World, Ceres

On March 6, the Dawn spacecraft will ease into orbit around the largest asteroid in the main belt: Ceres.

As it approached Ceres on Feb. 19, Dawn took a series of images creating this amazing animation:


Although the resolution is still a bit low—this was taken from about 46,000 kilometers away, with a resolution of about 4 km/pixel—there are some interesting things you can see. For example, the mysterious pair of bright spots stays very bright even as they rotate into darkness, finally fading once the Sun fully sets for them.

That’s quite different behavior from another bright spot. Watch the animation: When the bright pair crosses over into darkness, turn your attention to the left side of Ceres. The next bright area comes into view after a moment, and as it rotates to the right, you can see it fade quite steadily, resolving into a crater with a bright but indistinct spot in it. For many features on airless worlds (and some with air, too) how bright a feature looks depends on the angle of sunlight hitting it. That bright region fades as it spins to the east and the Sun sets for it, but the very bright spots don’t.

That’s a clue about what they are. But we still don’t know! As Dawn gets closer, and the images get better, scientists will be paying attention to details like that so they can figure out just what they heck we’re seeing.

Another really interesting feature is an as-yet unnamed basin about 300 kilometers across (seen in the image above to the lower right); to give you a sense of scale, that basin would just fit in between Washington, D.C., and New York City. As I pointed out in an earlier post, it’s very flat given its width; I’d naively think it should be deeper. After the impact the floor may have filled in with water ice (Ceres has a lot of ice; it’s cold out there past Mars), or there may have been other forces at work. The edges of the crater don’t look round, either; it looks more like a rounded pentagon. That sometimes happens when a crater’s edge falls near cracks in the surface or the explosion shock wave hits material that’s a different strength. It could also simply be an illusion, caused by subsequent impacts marring the nice circular outline and fooling our eyes. Or it could be something else entirely; I’m guessing. Hopefully we’ll find out more in the coming months.

Excluding some fuzzy Hubble images, Ceres has been little more than a dot in our telescopes for centuries. Dawn hasn’t even gotten there yet and we’re already learning a huge amount about it … and getting even more questions. Of course, that’s why science is so much fun!

And a note: Some people call Ceres a dwarf planet, others a big asteroid. To be honest, I find that all a big distraction from the main point: Ceres is a world, a fantastic and fascinating place worthy of our attention and exploration. Dawn isn’t even really there yet and look what we’ve seen so far!

March 2 2015 4:40 PM

Waterspout Scares Beachgoers in Brazil

File this under terrifying but not as bad as it looks: Around 1 p.m. local time on March 1, a waterspout formed off the coast of a beach in Recife, Brazil. Of course everyone watched it, but then things got substantially more chaotic as the waterspout headed for the beach, scaring everyone and getting them to scatter.


As you can see, it sends palm fronds and sand flying but doesn’t do a lot of damage (no injuries were reported). Waterspouts look like tornadoes, and they’re similar, but usually far weaker. Tornadoes form as air in a supercell starts to rotate, forming a localized and intense vortex that moves down from the cloud. Waterspouts like this one form more like dust devils, where a horizontal flow of air gets lifted up and maintains its rotation. Wind speeds in these so-called fair weather waterspouts—ones that form in calm weather, even if a dark storm cloud is nearby—top out at about 20 meters per second, but a tornado can easily have winds three times that speed.

Video taken from a different vantage point shows the spout while it’s still out off the coast, and you can see why people were freaked out; it does look like a tornado:

Amazing. The spout dies quickly once it’s over land; it probably couldn’t sustain the flow of warm air inward needed to maintain the spin.

While they’re weaker and tend not to do much damage, as you can see, you don’t want to screw around with them; the wind speeds are high enough to knock you down and carry debris. And some waterspouts do in fact form like tornadoes and can be much more severe. I’m glad no one was hurt here! And while the video is amazing, listen: If you see a waterspout heading toward you, it’s probably not the best idea to stop and take video. People will always take risks in weird weather situations, but I wouldn’t recommend it.

And if you see a fire tornado or an ash devil? Run.

Tip o' the beach umbrella to Clovis Tanganelli.

March 2 2015 11:30 AM

Crash Course Astronomy Episode 7: Gravity

I was traveling last week and couldn’t put up a post about Crash Course Astronomy when it came out. So, belatedly, here is Episode 7: Gravity!

Writing these episodes can be a tightrope walk. Gravity is an interesting topic; since we’re still early in the series, I wanted to go over the aspects of gravity we’ll need to talk about planets and moons, asteroids and comets. That means discussing it as a force, how it makes things move, how orbits work, and the difference between mass and weight. That also means not getting into things like how gravity curves space, and why massless photons are still affected by gravity. I mention it but don’t go into details. Think of it as a teaser for a later episode.


I wrestled over discussing how gravity is a force that accelerates things. This is part of Newton’s Second Law of Motion: A force acting on a mass will accelerate it.* The gravity of the Earth is independent of the mass it’s working on; it’s a property of the Earth itself. If you drop two objects of different weights, they’ll fall at the same rate (ignoring air resistance). My friend Brian Cox demonstrated that quite ably.

The objects will accelerate, which means that the longer they fall, the faster they’ll go. That acceleration is a property of Earth’s gravity, and will be the same for any object. Drop a ball near the ground, and it will accelerate at a rate of about 9.8 meters per second for every second it falls. After one second it’s moving at 9.8 m/s. After two seconds it falls at 19.6 m/s, and so on.

But the force it feels is different than a ball that has a different mass. That’s the weird part that can be confusing. Gravity accelerates everything the same, but if you have more mass you feel more force. When it comes to gravity, we call that force weight. Because the force is bigger we think a more massive ball will fall faster, but it doesn’t because the acceleration is the same as it is for a less massive ball.

But if you want to stop a heavier ball, you’ll have to apply more force than you would on a lighter ball. When the heavier ball hits the ground, it hits harder than the lighter one, even though they’ll impact at the same speed.

cheese balloon
The holes make it lighter.

Photo by Shutterstock/Olga Ivanova

Now, did you notice the verbal switcheroo I just pulled? I talked about the more and less massive balls in one paragraph, then called them heavier and lighter in the next. That’s sloppy (though I did it on purpose to prove a point)! In deep space, with no (or negligible) forces acting on them, they both weigh the same: nothing. But their masses are different. Wheee!

If you think you get this now, yay! Good. But here’s a test: What weighs more: a 5 pound helium balloon, or a 5 pound block of cheese? The answer may seem obvious, but explaining it isn’t all that easy.

Maybe I’ll need to make a bonus video with that. I’ll need a big balloon. I wonder if I can get George Clooney and Sandra Bullock to guest star?

*Actually an unbalanced force; if you have another equal but oppositely directed force acting on it, the object won’t accelerate. If it’s moving it’ll still move, but if it’s just sitting there it won’t start to move. See why you need to simplify sometimes? You just need to be careful that you don’t oversimplify and make things worse. That’s another reason writing these episodes can be tricky.

March 2 2015 7:15 AM

The Week in Political Buffoonery

As someone who understands science and math, I know that when you look into a particular population looking for instances of a particular behavior, sometimes those behaviors will cluster in time. You might go a few weeks with very few instances, and then suddenly see a big clump of them happening at the same time.

Of course, when we’re talking anti-science buffoonery in politics, there is a vast, vast sample size. The statistics are pretty good.


Still, last week there were a large number of forehead-smackingly nonsensical ridiculosities. Out of them all, here are three guaranteed to put a dent in your desk where your head slams into it.

1) James Inhofe Disproves Global Warming Because Snow

Sen. James “Global warming is a hoax” Inhofe (R-Oklahoma) has never met an argument against climate change too silly and obviously wrong not to repeat. Last week, he actually stood on the floor of the United States Senate, and talking about global warming, he—and I can’t believe I’m typing this—pulled a snowball out of a plastic bag and said,

I ask the chair, you know what this is? It’s a snowball, just from outside here. So it’s very, very cold out. Very unseasonal.

Yes, Sen. Inhofe, it snows, because it’s winter. The planet is warming up, but it still gets cold in the winter (at least it does for now). If your average low temperature in February is, say -10° Celsius, then it can warm up a few degrees and still be below the freezing point of water. That’s grade-school math.

Clearly, Inhofe is an Axial Tilt Denier, too. I wonder how he’d feel knowing that he has a lot in common with a Saudi cleric.

As Stephen Colbert has said, the idea that winter disproves global warming is like nighttime disproving the existence of the Sun. If you want details, Jon Stewart did a great job slam-dunking the it’s-cold-outside-therefore-no-global-warming dumbosity.

Snark aside, Inhofe’s head is quite firmly in the sand, and he’s an embarrassment to the Senate.  I hope this is his “Michael Dukakis in a tank” moment. Thank heavens another Senate member, the wonderful Sheldon Whitehouse (D–Rhode Island), took him to task for this.

2) House Science Committee Member Doesn’t Vaccinate

Speaking of dangerous rhetoric, on the House side, Rep. Barry Loudermilk (R-Georgia) took a moment in a public town-hall meeting to let everyone know he didn’t vaccinate his kids:

Great, huh? He tried to follow up later saying he’s not against inoculation, but it’s clear he doesn’t understand the issue (and by the way Jenny McCarthy says she’s not anti-vax, either). And we know Tea Partiers tend to be anti-vax as well, though it’s usually about being anti-government, not anti-science per se.

Did I mention Rep. Loudermilk is on the House Science, Space, and Technology Committee? It may be past time to change its name.

And Rep. Loudermilk, when a GOP strategist tells you to resign over something ridiculous that you’ve said, you really, really need to rethink your position.

3) A Load of Taurus

American politicians don’t hold the monopoly on anti-science nonsense. Unhappily, facing away from reality knows no country’s borders. Case in point: Tory MP David Tredinnick thinks that a lot of the U.K.’s health problems could be helped by turning to astrology.

Just go to that link and see if you can count how many logical fallacies he relies on to back up this sentiment. Have a calculator handy. In the meantime, I’ll just leave this here.

So yeah, I’m being a bit snarky, but remember, these are critical topics—the environment, public health, and the health of science itself. If these politicians are willing to dump evidence-based reasoning by the side of the road, then what else are they willing to do? And they make our laws.

It’s time to dump them. If your representatives don’t believe in reality, then next election time it’s your responsibility to show it to them.

March 1 2015 7:30 AM

Me vs. Hank Green: SciShow Quiz Show

Part of the vast Hank and John Green video empire includes SciShow, a YouTube channel that has a variety of different science shows on it, like SciShow Dose (quick videos on interesting topics), News, Infusion (longer videos, like the vaccine one I posted about recently), and many more.

They also have Quiz Show, where two sciencey-type people go head to head in a snarky contest to see who knows more science, but which in reality just shows who can guess the answer better than the other.


When I was up at the HQ last time filming some episodes of Crash Course Astronomy they asked if I wanted to be on Quiz Show, and never one to give up an opportunity to make a fool of myself on camera, I said sure. So they pitted me against the man himself, Hank, in a battle of brains. Who will win? Find out for yourself:

So, congrats, Ian! I hope you enjoy your swag. And yes, I was very pleased with myself for deducing the answer to the second question, getting it right for the right reason. SCIENCE!

Feb. 28 2015 7:30 AM

Ticket to Space

My friend Dan Durda is many things: an astronomer, a planetary scientist, an artist, a pilot.

He’s also an astronaut. Or he will be, very soon.


He works at Southwest Research Institute here in Boulder, Colorado, which is a company that does a lot of work in space; the New Horizons Pluto probe instruments were developed there, for example, and the principal investigator, Alan Stern, is there. Dan’s very interested in the behavior and structure of asteroids, which is difficult to study here on Earth.

So he and his fellow scientists at SwRI got an idea: Go into space.

We’re at the doorstep of cheaper, more reliable access to space. Ticket prices are within reach of wealthy individuals and, perhaps more importantly, companies that do science. A lot of Dan’s experiments can be done easily in the few minutes of weightlessness these suborbital flights provide.

What he said is true: We’re just starting off doing this work, and we don’t know where it will lead. There have been setbacks, for sure; the loss of the Virgin Galactic vehicle and its pilot last year, and the explosion of the Antares rocket upon liftoff.

As I have written many times before, while tragic, these sorts of losses are inevitable. They are the price we pay for pushing boundaries, and you’ll find most astronauts understand these risks. To use an analogy Dan made in the video, where would be now if airplane crashes grounded the airline industry in the early 20th century?

We’ll continue on, pushing our way into space. Again, as Dan points out, we cannot know where this will lead … except up. And that’s a direction I think we should go.

Feb. 27 2015 7:30 AM

Psychedelic Crab

The benefits of cleaning out your inbox: I somehow completely missed this spectacular image when it came out a while back, but now that I’ve found it I can share it!

Ye. Gads.

That's the Crab Nebula, one of the most well-studied and famous objects on all the sky. It the expanding gas cloud left over from a titanic supernova explosion, in this case the death of a very massive star. The light from this explosion reached Earth in 1054, and in the subsequent millennium the debris has reached a size of well over 10 light-years.

That’s 100 trillion kilometers, just so’s you know. 

Feb. 26 2015 10:45 AM

Kepler-432b: A Doomed Planet Orbiting a Doomed Star

Two independent teams of astronomers have just announced the discovery of an unusual planet with a grim future: Kepler-432b.

The planet orbits a star nearly 3,000 light-years away and was discovered using the Kepler observatory, which looks for telltale dips in star light as a planet orbits a star; if the planet’s orbit is seen edge-on from Earth, then once per orbit it blocks a small fraction of the star when it passes directly between the star and Earth.


Measuring the timing of the dip (and knowing some of the properties of the star) yields a lot of information about the planet, including its size, and the size and shape of its orbit. They also took spectra of the star, breaking its light up into thousands of individual colors, which yields one more crucial piece of information: the mass of the planet. The planet and star orbit a common center of gravity, and as the star moves in its orbit its spectrum changes due to the Doppler shift. This effect is pretty dang small, but measurable using precision instruments.

The results are pretty cool: The planet Kepler-432b is roughly five times more massive than Jupiter, but only about 1.1 times as wide. This makes it pretty dense, about as dense as Earth! Gas giants have a weird property that as they get more massive their size doesn’t increase much—instead, the pressure inside them increases, and their density goes way up. Jupiter is right at about the lower limit where that happens, so planets can be much beefier than Jupiter but not much bigger.

But what makes this system special is the star itself. It’s a little more massive than the Sun, but it’s what we call a red giant: A star that is starting to die.

At some point in the past, the star Kepler-432 ran out of hydrogen fuel in its core. The core of the star is shrinking and heating up, dumping all that heat into its outer layers. What happens to a gas when you heat it up? It expands. And so Kepler-432 has swollen up to a size about four times wider than our Sun. As it got bigger its surface area increased, too, and so, weirdly, the amount of energy coming through its surface per square centimeter has actually dropped, lowering its temperature. Cooler stars are red, so Kepler-432 is a red giant.

It will continue to grow as it ages, swelling to a much larger size than it is now. Much larger. Will it engulf the planet?

It may not grow enough to swallow the planet directly. However, as it gets bigger, it interacts with the planet via tides, and (through a complicated series of steps) will actually drop the planet closer in to the star.

It looks like this one-two punch is enough to doom the planet. The star will grow larger, the planet’s orbit will shrink, and then … doom. The planet will fall into the star, where it will plunge deeper and deeper, until it evaporates completely.

But don’t despair too much. As the planet falls inside the star, it takes a while to disintegrate. It orbits much faster than the star spins, so it may churn up the insides of the star like a whisk in a mixing bowl of batter. The star’s rotation will increase. As the star continues to age, it will fling off its outer layers, exposing the hot core at its center. This very dense, very hot object, now called a white dwarf, will blast ultraviolet light into space, illuminating and exciting the gas it ejected, causing it to glow. Because the star was spinning, this gas can take on fantastic shapes, including double-lobed patterns reminiscent of butterfly wings.

The Swan and the Butterfly
The future of Kepler-432b? This is NGC 7026, a planetary nebula: a gas cloud expelled and stimulated to glow by a dead star.

Photo by ESA/Hubble & NASA

Scientifically, this system is fascinating; we don’t have too many examples of giant planets orbiting red giant stars (which may be in part due to the fact that they tend to fall into their stars!), so every one we find is important. The planet orbits the star on a long ellipse, too, which is unusual and difficult to explain. There are many mysteries to plumb here.

And metaphorically, well, this transformation is almost too on-the-nose: Like a caterpillar, the planet and star will transform into something magnificent, literally a butterfly shape. And it will glow fiercely like that for centuries, its beauty visible easily from telescopes even thousands of light years away.

The Universe is all about change, birth, destruction … and given that, perhaps Kepler-432b’s eventual fate isn’t such a bad one.

Postscript: You can read the papers published by the two teams who studied this planet: Ciceri et al., and Ortiz et al. Their results match pretty well, though, interestingly, Ciceri et al. find no evidence for a second planet orbiting the star, while Ortiz et al. do. Also, Ciceri et al. conclude the planet won’t be engulfed. I don’t think they included the work showing the planet’s orbital radius will shrink, though, which was considered by Ortiz et al., so I tend to agree with Ortiz’s team. The planet is doomed.