Bad Astronomy
The entire universe in blog form

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.

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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












The Swan and the Butterfly

Photo by ESA/Hubble & NASA





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







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?










It also saves lives.


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).


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.

Feb. 21 2015 7:30 AM

Stars of Reality

Y’know, it’s easy to make fun of celebrities who endorse ridiculous nonsense. Certainly Jenny McCarthy has earned the wrath she’s received over vaccines, and Rob Schneider says things that make McCarthy look like an icon of reason. Even Bill Maher, praised on many topics by critical thinkers, says things about vaccinations that make me cringe.

But I think it’s just as important to praise celebrities when they do the right thing. I’m a big fan of Amanda Peet, who is an outspoken supporter of actual, true vaccine information, and of Sarah Michelle Gellar as well.


And now I can add to that list actress Kristen Bell. I’ve always liked her, but now I can add her to my cadre of celebrities I respect. Why? She said this:


Nice! Simple, straightforward, and makes the message clear. And if that weren’t enough, bless her reality-based brain, she went on to say,


Heh. A bit more snarky than I would’ve phrased it, but the sentiment is understandable. I always want to be clear that I distinguish carefully between parents who are being misled, and the ones who mislead them. When I use the word “anti-vaxxer,” overwhelmingly I mean the latter, especially those vocal few who willingly or otherwise grossly distort reality to fit their own views.

It’s easy to be confused by doubt-sowers, especially if it’s in a topic with which you’re not that familiar. And Google will fail you there; leading you many times to the very pages of the anti-vaxxers themselves, instead of more reliable sources (like the Centers for Disease Control and Prevention,  Harpocrates Speaks, Voices for Vaccines, the Autism Science Foundation, and Every Child by Two). And a lot of those anti-vax groups produce dangerous information, ideas that are a clear threat to the public health.

So again, I will continue to praise people in the public eye who take a stand for reality. Good on you, Ms. Peet, Ms. Gellar, and now Ms. Bell. Count me as a fan.

Addendum: Parenting magazine has a list of other celebrities who support vaccination.