Bad Astronomy
The entire universe in blog form

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 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!

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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.

Feb. 26 2015 7:00 AM

Ceres Is Getting Weirder

Dawn approaches Ceres.

The spacecraft Dawn, that is, and the asteroid Ceres, the largest of the rocks orbiting the Sun between Mars and Jupiter. Dawn has been headed slowly toward Ceres for many months now, and only recently has its target been big enough to see as more than a dot. 


On Feb. 19, 2015, Dawn took the image of Ceres above from a distance of 46,000 kilometers (29,000 miles; roughly an eighth the distance of the Moon from the Earth). Earlier pictures already revealed a bright spot on the surface, and now the resolution is good enough to see it’s not one spot, but two. Like a distant car on the highway getting near, and seeing its headlights split from one bright glare to two, Dawn’s proximity to Ceres has allowed us to see the shiny spot is not alone. 

As Ceres rotates Dawn sees more of its surface. It looks like it's had a rough couple of eons.


It’s still too early to say what we’re seeing here. Ceres has a lot of water ice inside it, and it seems likely these spots are related to that. You can also see they’re located in a crater—which isn’t necessarily remarkable; as you can see the whole surface of Ceres is saturated with them. My initial thought was that an impact had revealed ice underneath the surface, digging it up. We see that in some craters on Mars, for example.

But now I wonder. It’s possible that we’re seeing cryovolcanism: literally, ice volcanoes. But it’s hard to understand what would drive that. Ceres is too small to have tectonics and has no moon that might generate tides to warm the interior. 

At the moment, it’s a mystery. And that’s good! We've never seen Ceres in this detail before, so everything we learn about it will be new.

For example, look at the large craters on it. They look to me to be flatter than craters that size would be on other worlds. I suspect we’re seeing either a softer surface, or that ancient, big impacts melted ice under the craters which flooded the floors. We see similar things on the Moon, but in that case it was molten rock, not water, that filled the floors. 

But I’m speculating, based on what we see so far. And these are still relatively low resolution images; compare them with what we saw when Dawn orbited Vesta, its first asteroid target, to get a taste of what’s coming. Dawn will enter orbit around Ceres on March 6, and will continue to orbit the asteroid for well over a year. What mysteries will it unveil that we haven’t even guessed at yet? 

Feb. 25 2015 11:45 AM

Tempest Vermilion

Gavin Heffernan is a photographer who travels to difficult-to-reach locations and shoots simply tremendous time-lapse videos of the landscape and night sky he sees there.

He just sent me a note that he’s created another video, and, well, holy wow. It’s another stunner: “Tempest Vermilion,” shot at the Vermilion Cliffs National Monument in Arizona.


You know the drill: Make it full screen, set it to high-def, crank up the volume, and let your eyes and brain soak it up.

This is the second part of a trilogy of videos Heffernan has created for BBC 2; the first, called “Wavelight,” is online as well. He and his collaborator, Harun Mehmedinovic, are also making a video about the effects of light pollution. Called “Skyglow,” it’ll be on Kickstarter in early April. Stay tuned for that.

In the meantime, take a look at these other amazing videos by Heffernan:

Feb. 25 2015 7:30 AM

A Supermassive Black Hole’s Fiery and Furious Wind

When you think of black holes, you probably think they are chaotic destroyers of all; wandering through space devouring everything in their path, and once something gets too close, it’s gone forever.

That’s a little unfair. Actually, a lot unfair. They only eat stuff that’s nearby, for one thing. And for another, they’re sloppy eaters. Not everything falls straight down their gullet; a lot of it can swirl around the black hole in what’s called an accretion disk. Material in that disk can be heated to terrifyingly high temperatures, millions of degrees, causing it to glow fiercely bright. It can blast out X-rays, and even create an intensely strong wind of material that flows away from the black hole.


We also know that every big galaxy we look at has a supermassive black hole in its very center. If that black hole has gas and matter falling into it, the accretion disk can be huge and ridiculously, soul-crushingly bright. The luminosity of such an object can easily outshine the hundreds of billions of stars in the host galaxy, and make the black hole visible clear across the Universe.

This sets up an interesting problem. When you have a monster in the middle like that, how does it affect the rest of the galaxy? A curious fact was discovered many years ago; the mass of the black hole in a galaxy seems to correlate with how the stars in the galaxy orbit. You might think “duh” to that, but hang on. Even though a black hole can have a mass of a billion times the Sun, that’s a teeny tiny fraction of the mass of a galaxy with a few hundred billion stars in it.

Somehow, the black hole is affecting the galaxy around it on a huge scale. How?

jets from a black hole
Sometimes a black hole wind can be focused into a tight beam.

Photo by NASA/JPL-Caltech

The obvious way is through this wind, this cosmic hurricane of particles blasting outward from it at high fractions of the speed of light. Studying that wind is maddeningly difficult, though. For example, when we look right at the center of the galaxy, all we can see is the extremely narrow slice of gas between us and the black hole. That gas absorbs the light coming from the accretion disk, blocking it. As it happens, different kinds of atoms block different colors of light. One type of iron, for example, that has a lot of its electrons ripped away from the intense energy blasting away nearby, is really good at absorbing a very specific wavelength of X-rays.

That can tell you something about the gas, like how hot it is, and how fast the gas is moving away from the black hole. But what it doesn’t tell you is the overall shape of the wind. Is it blowing out spherically, like an expanding balloon, or is it focused into narrow beams?

Lots of black holes have those beams screaming away from them. We know this because we can see them. But not every black hole has them. So how can you figure out the shape of the wind?

Some astronomers have just announced they found a way. The black hole they observed is a billion-solar-mass beast in the center of the galaxy PDS 456, which is about 2 billion light-years away. It’s fairly well studied, and is a good example of a typical “active galaxy,” one with an actively feeding black hole in its core.

They observed it using two different observatories: XMM-Newton and NuSTAR. Both can sort incoming X-rays into their individual energies (think of that like color in light we see). XMM-Newton could see the gas blocking the black hole directly, but can’t detect any gas anywhere else. NuSTAR, however, is able to see the kind of X-rays that would be coming from gas surrounding the black hole … and it did. Looking at the spectrum of the X-rays, it found the unmistakable signature of gas expanding outward in a sphere (if you want technical stuff, it saw a classic P-Cygni profile).

This is a big deal. The geometry of the expanding wind can tell us its total energy. Think of it this way: Imagine you have a 1-watt light bulb. It looks pretty dim, because it’s sending light out in all directions. Only a little bit of the light is heading into your eye. But if I have a flashlight, it focuses the energy emitted, so it can gather up all the light being wasted in other directions and beam it toward you. The bulb in a flashlight can be a lot dimmer, but still look brighter to you because of that.

A New Look at an Old Friend
Beams from a supermassive black hole can visibly stretch for thousands of light-years. The galaxy Centaurus A has beams that affect it on all scales.

Photo by X-ray: NASA/CXC/U.Birmingham/M.Burke et al.

And that’s the basis of these new observations. They saw that the wind from the black hole is expanding in all directions, which means the astronomers could determine the overall physical nature of the wind. It turns out the black hole is blasting a wind that totals 10 times the Sun’s mass every year—and mind you, that vast amount of stuff is screaming out at tens of thousands of kilometers per second. If I’ve done my math right (and I have; I checked), that means the mechanical energy in that wind is a staggering 10 trillion times the total energy the Sun emits every second.

Ten trillion.

And that wind is blowing outward in all directions, so it can easily affect the gas around it, even thousands of light-years away. This in turn would affect how stars form in a galaxy, and explain the relationship we see between the black hole and the stars in the galaxy around it.

And here’s the really cool thing: We think those big black holes form at the same time as the galaxy itself. As the zillions of tons of gas swirl around in the proto-galaxy, assembling itself into stars, some of it is falling into the nascent black hole in the center of that maelstrom. It forms a disk around the black hole, heats up, and starts to blast out a wind. This wind slams into the gas around it, all around it, blowing it hither and yon.

When the galaxy finally coalesces as a massive island universe of billions of stars, the motions of the stars themselves still have the fingerprint of the black hole’s wind imprinted on them, even billions of years later. And that wind may have helped trigger more stars being born as it rams into and compresses the gas around it, just as it can also shut down star formation by blowing that gas away.

Our galaxy, the Milky Way, has such a black hole in the middle. It’s not a big one as they go, a mere 4 million times the mass of the Sun. But 10 billion years ago, when our galaxy was forming, it may have been active, and may have affected the young galaxy around it as well.

When you go outside at night and look at the stars, think on that. If you can see Sagittarius, you’re looking toward the center of our galaxy, where that monster dwells. It’s surrounded by billions of stars, so distant from us their light merges into a soft glow. But they’re there, those myriad stars, and their motions, their formation, even their existence itself may have been profoundly influenced by a black hole that we didn’t even know existed until a few decades ago.

Ah, science. It allows us to wonder about the inner workings of the Universe we live in, and then shows us how the pieces fit together. If there is a grander, more exhilarating adventure than that, I don’t know what it is.

Feb. 24 2015 7:30 AM

Why Do Some People Refuse to Get Vaccines?

There’s been a lot of discussion in the media (both mainstream as well as social) about vaccinations, spurred because of the current measles outbreak in the U.S. I’m unhappy about the cause, of course, but I welcome the discussion. I’m just sorry it took an outbreak from Disneyland to get this conversation rolling.

A lot of people are blaming anti-vaxxers for the outbreak, but the truth is more complicated than that. Certainly Jenny McCarthy, Andrew Wakefield, and the organized groups spreading dangerous misinformation about vaccines have their share of it, but their influence isn’t almighty. There’s more to this story. 


Hank’s overview is pretty good, and very well laid out! But I want to add a few things.

One is that this is not just a hippie, liberal thing. Very conservative people, including libertarians, don’t want the government telling them what to do, so state-required vaccinations for children to allow them in schools is anathema to them. I’m not saying they’re right—in fact, they’re very, very wrong—just that this is what they think. Anti-vaccination sentiment is well distributed throughout the political spectrum.

Another is that overall in the U.S., vaccination rates haven’t fallen in recent times. But that casts a mighty wide net. If, instead, you look on smaller scales, you see pockets of low vaccination, regions where rates have dropped dramatically. Sure, some are liberal bastions like Northern California, but other places are affected for other reasons, like the Texas town influenced by a megachurch.

And, as always, I want to point out that I understand how parents feel here. I have a daughter myself, and my wife’s and my concerns for her health were and are strong. So I want to distinguish between parents out there trying to figure this all out, and the people who are actively and vocally trying to confuse them over this issue.

I know how important vaccines are, and my entire family is up-to-date with their vaccinations. I’m walking the walk

Hank’s audience for SciShow tends to be younger folks, and I hope they take this lesson home (literally as well as figuratively). This issue of bias and evidence goes well beyond vaccinations, into the very trust we have of science itself. That’s something I’d love for younger folks to understand. Science is pretty cool, and the most important tool humans have to understand everything around us.

It also saves lives.

Addendum: Germany is facing a large-scale outbreak of measles as well, with nearly 600 cases since late last year (the population of Germany is one-fourth that of the U.S.). One boy, an 18-month-old, recently died from complications due to measles. My heart aches over this, which is why I write so frequently about vaccination. My thanks to Mat Johnson for alerting me to this.

Feb. 23 2015 7:30 AM

Mooning Pluto

Pluto is an interesting little world. Smaller than our Moon, it still boasts no fewer than five moons discovered so far. The first, Charon, was discovered in 1978, but the second through fifth were found just a few years ago using Hubble data.

How many does Pluto have? It’s not known, because smaller, fainter moons may yet be undiscovered. But as the New Horizons probe nears Pluto, we may find more.


Charon is big and relatively bright and has been seen in New Horizons images since 2013. But now two of the smaller moons, Nix and Hydra, have been spotted as well!

Pluto animation
Moons in motion: with stars (left) and without (right).

Photo by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The animation on the left shows Pluto heavily overexposed (the bright tail off to the right is called blooming, and it’s an artifact of some digital detectors), with stars in the background. The moons have boxes around them to make them easier to spot. The animation on the right has the stars subtracted off, making it easier to see the moons’ orbital motions around their parent body. To give you a sense of scale, Nix and Hydra orbit about 50,000 and 65,000 kilometers out from Pluto. The moon’s physical sizes are unknown, though less than 100 km across. They’re unresolved in these images, and in the Hubble images as well. When New Horizons gets closer it will certainly give us a far better idea about these little guys.

Each frame of each animation is a total of a 50 second exposure, which is pretty impressive. New Horizons is moving pretty fast, about 14 km/sec, so it needs to take short exposures as it flies through the Pluto system or else there will be motion blur.

These images are mere tastes of what’s to come. In the months ahead we’ll see Pluto resolved, surface features revealing themselves, and more detail on these moons as well. Perhaps the probe will discover more moons circling Pluto, too.

Hopefully it will shed light on how the moons formed; one current theory is that Pluto and Charon formed at the same time, out of the material that formed all the icy bodies past Neptune. Then, later, an impact on Pluto blasted chunks into space, which formed the other moons. Pluto doesn’t have a lot of gravity, but it also lacks nearby neighbors, so it can hold on to several moons without losing them due to perturbations from other massive bodies. We know many asteroids and other big icy objects past Neptune have moons, so seeing these close up may be able to help us understand how they came to be in the first place.

Feb. 22 2015 7:30 AM

Conspiracy Revealed: The Simpsons Has Been Lying to You

I’ve been a fan of The Simpsons for a long time. Obviously. So when I heard that SpaceX’s head guy Elon Musk was guest-starring on the show, I hoped it would be a good episode. And it was! As I watched I marveled at how funny the show was even after all these decades and laughed quite a bit as the story unfolded.

… Until a scene came up that chilled me to the bone. I was so shocked that I had to rewind and watch it again, then freeze frame it to make sure I wasn’t hallucinating.


This is the moment that changed everything for me. The frozen moment of time when I realized that for 26 years, The Simpsons has been lying to us.

This shows Musk standing at the dining room window of the Simpson’s house, looking out and pontificating at the night sky as the family behind him eats dinner.

But look at the Moon. LOOK AT THE MOON!

It’s backwards. The scene is clearly at dinner, early evening, so that’s the setting crescent new Moon. But in the Northern Hemisphere, the tips of a waxing crescent Moon point to the left, away from the Sun (that link describes how the phases of the Moon relate to the time of day and the Moon's position in the sky). Here’s a photo I took myself in November 2013:

Moon and Venus
The Moon and Venus, as not seen from Springfield.

Photo by Phil Plait, northern hemispherean

See? I took that picture shortly after sunset, around dinnertime. It was new Moon, and the crescent's tips point to the left. But in that scene with Musk, they point to the right! How can that be?

There’s only one way. Springfield is not in the United States at all. It’s not even in our half of the world. Springfield is in the Southern Hemisphere!

I don’t even know how to react to this information. It’s as if … my whole world has been turned upside down.

*Correction, Feb. 23, 2015, at 16:30 UTC: I originally misstated that The Simpsons has been on TV for 22 years. It's in its 26th year, which is actually pretty astonishing.