Bad Astronomy
The entire universe in blog form

April 21 2016 9:00 AM

Look! Up in the Sky! It’s a Bird, It’s a Plane … Actually, It’s a Bird and a Rocket.

If you look up into the sky long enough, you’ll see the weirdest things.

Astrophotographer Grahame Kelaher was in Western Australia late at night on Feb. 6, and he saw the odd, fan-shaped blue glow in the photo above moving across the sky. He wasn’t surprised, though: He planned for it!

That’s not some nebula—it’s actually the glow from fuel dumped into space by the Centaur upper stage of a United Launch Alliance Atlas V rocket! The Atlas launched from Florida on Feb. 5,* carrying an Air Force Global Positioning System satellite GPS IIF into orbit.

The Atlas was configured for this launch as a two-stage vehicle. The lower, first stage, lobbed the upper stage, called a Centaur, and the GPS sat high above the Earth. The Centaur then burned to put itself into an elliptical “parking orbit,” then it burned again to achieve the desired near-circular orbit 20,450 kilometers from the Earth’s center (roughly 14,000 kilometers above the surface).

Once that happened, it performed three tasks: It released the satellite, it made a “collision avoidance maneuver” to make sure it wouldn’t accidentally hit the satellite, and then dumped the remaining fuel in its tanks into space for safety.

These events occurred when the Centaur was over Australia, and Kelaher captured them on video!

In the video you can see the plume of gas lit by the Sun (it was 03:00 local time, but the Centaur was high enough up to be in sunlight). Because it’s essentially a vacuum that high up, the gas cloud expands without friction and moves along with the Centaur and satellite. You can see (what I presume is) the GPS satellite moving along with the plume, just to the lower left.

Moving across the sky they appear to pass several well-known astronomical objects, including the fantastic globular cluster Omega Centauri and the spectacular Carina Nebula.

Because the launch time and orbit were known in advance, Kelaher could know in advance to see them … as he had been hoping and planning to for six years!

Patience pays off.

I’ve never seen anything like this, though I once saw a rocket booster burn up in re-entry many years ago, and it was amazing. This would really be something to observe! Rocket launches can create all kinds of truly spectacular and bizarre sights. And I’ll add that you can see many satellites with the naked eye (check Heavens Above for local listings of visible satellites), and it can be a real kick to spot one and identify it.

Going out under the night sky is never time wasted. The rewards are many, and if you do it enough, the bonuses can be pretty nice, too.

Tip o’ the payload fairing to the Ice in Space group on Facebook, and to Suzy Webb in particular.

* Correction, April 21, 2016: I originally misstated that the launch was on April 5.

April 20 2016 11:45 AM

The Future Is Here: A Festival Celebrating Science and Science Fiction

Are you a) a science enthusiast, 2) a science-fiction fan, and γ) live near Washington, D.C.?

Then you’re going to love this weekend: Smithsonian magazine is holding a festival called “The Future Is Here,” from Friday to Sunday, April 22–24. It’s a celebration of science and science fiction and how they interact. It’ll be a lot of fun.

Most of the events are free, but some require tickets (which are on sale now). The speakers range from NASA scientists to actors, writers, and producers of television sci-fi. For example, one speaker is a guy named William Shatner, of whom you may have heard. Also speaking is Chris Carter (creator of The X-Files), NASA Deputy Administrator Dava Newman, explorers Céline and Alexandra Cousteau, Arc Attack (Tesla coils playing music!), and seriously a much longer list of very cool people.*

Also, me. I’ll be there in two capacities. On Friday night I’ll be moderating the 12 Monkeys panel, with co-creator Terry Matalas and stars Amanda Schull, Aaron Stanford, and Emily Hampshire. 12 Monkeys is a new series on Syfy, a part of the network’s notable and in my not-so-humble opinion highly successful campaign to put out some seriously high-quality television shows (like The Expanse).

12 Monkeys is loosely based on the movie of the same name, about a group of scientists from the future who use time travel to try to prevent a global plague that wipes out nearly all of humanity. The first season has already aired, and the second started this past week. It’s a really good show, atmospheric and clever, and I dig it. On the panel we’ll be discussing the mechanics and philosophy of time travel, how the writers keep up with alternate timelines, and how the actors and crew keep up with what must be a bonkers filming situation. Multiple timelines and multiple time eras can’t be easy to track.

12 Monkeys
My character isn't quite fleshed out yet.

Photo by Syfy / NBC Universal (modified by Phil Plait)

In my second role at the event, I’m very pleased to be interviewing Dava Newman on stage, one on one, about NASA: where it’s going, how it’ll do it, what their plans are. I’ll also be giving a very brief presentation on what NASA means to me, introducing several other NASA speakers, and then also bringing in, via Skype, Andy Weir, the author of the best-selling novel The Martian, which you also may have heard of. I hear a pretty good movie was made about it.

I am very much looking forward to the festivities! I’ve been a science-fiction fan my whole life, and (obviously) also a science aficionado. The two are inextricably linked for me, each urging on and inspiring the other. The recognition this symbiosis gets now warms my heart and makes me hope for the future.

In many ways, that’s what both are about.

So please join me and all these fantastic guests for a weekend of looking up, looking out, and looking forward.

*Correction, April 20, 2016: This post originally misspelled Chris Carter’s last name.

April 20 2016 9:30 AM

So Maybe Not Aliens, but How About Comets?

So it’s been a while. Where are we now with the aliens-building-megastructures star?

A quick recap: As you may remember, citizen astronomers combing through Kepler spacecraft data found a very weird star. Kepler stares at thousands of stars looking for dips in their light, indicating a planet passing in front of the star. This is called a transit and is a massively successful way of finding such exoplanets.

Usually, the light from a parent star will have one dip every few days or weeks or so, as the planet orbits it. But the amateurs looking at the data from the star KIC 8462852 found something very different: Lots of little dips happening at irregular intervals, and the occasional big dip. And by big, I mean like 20 percent or more of the star being blocked. That’s colossal, and doesn’t make a lot of sense at first blush; even a huge planet might block only 2 or 3 percent of a star’s light.

The citizen scientists looking at the data were part of a team from Planet Hunters, an effort to get more people looking at Kepler science. They contacted their team leader, Tabetha Boyajian, who then published the data with a series of possible explanations, including perhaps a swarm of comets passing the star and blocking its light. More on that in a sec.

Another explanation is that aliens live on a planet orbiting that star, and are building giant solar collectors to generate the energy needed to sustain an advanced civilization. To be clear, we know this is incredibly unlikely to be the case, but it’s an intriguing idea. SETI even aimed its radio telescopes at the star to see if they could pick up any signals, but nothing so far.

Boyajian herself gave a TED talk about this star, and it’s well worth watching.

Still, Tabby’s Star, as it’s now colloquially called, is intriguing. I’ve never been convinced by the comet explanation. It seems the least unlikely explanation—faint praise!—but a new paper has come out giving it a bit of a boost. The researchers find that a swarm of comets could explain the clusters of smaller dips of starlight. It would take a few hundred comets if they’re each around 10 kilometers across, or a few dozen if they’re 100 kilometers across.

Their explanation actually works pretty well for the small dips, but it still makes me wonder. The comets would be very hard-pressed to explain the two very large dips in light seen in the star, meaning something else would have to be invoked to explain those. That’s not very parsimonious.

And a swarm of comets isn’t a stable thing; after a few thousand years it should break up. For this to work, you’d need a huge object, like the size of Ceres, breaking up for some reason (a huge impact?) with the pieces becoming these comets. Or it could be that we happened to catch the start of a bombardment, a long period of comets dropping down from the outskirts of their solar system, perhaps disturbed by the gravity of a passing planet.

Scientists don’t like coincidences; they’re like a magic wand, too easy to use to solve problems. But they do happen. And it’s worth remembering that we are seeing something very weird happening at this star, something we’ve never seen before, and all the other explanations are even less likely. We might not like picking the least bizarre explanation, but this star is really blowing the curve on what’s normal.

Interestingly, another astronomer found that the star appears to be dimming slowly, over the course of the past century or so at least. I have to wonder if that could be tied to the comets; they tend to be surrounded by clouds of gas and dust, which might contribute to an overall dimming. But other observations showed no signs of these clouds.


So, to answer my first question: Where are we with this star? Still scratching our heads, I think. Comets may explain some of it, but not all. It may be several related things happening at once, or maybe different things happening around the same time. Or it may be just one thing no one has thought of yet.

It’s a mystery, but a fun one. What’s going on? We just don’t know. But more observations (not just of this one star, but as many others as possible, too, to see whether Tabby’s Star is unique), and more people thinking about it are the way to go. The aliens idea may make this seem silly, but the data are real. Something is going on around this star. I don’t know what it might be, but what I can guarantee is that when we do figure it out, it’ll be something pretty amazing.

April 19 2016 12:30 PM

A Sooty Cosmic Spider 

I’m always surprised when I find a picture of a nebula I’ve never heard of before, especially when it’s big and splashy and very cool-looking, as well as scientifically really interesting.

So I got a bit of a shock when I saw this image of IC 417, aka The Spider Nebula, on NASA’s Instagram feed*:

April 19 2016 9:15 AM

Optical Illusion: Are These Lines Moving, or Is This a Spinning Square?

Our brains are a mess.

They evolved step by step, one function added to another in a million small steps that might help in one way, but that conflict with what another part of the brain is trying to do. When you couple that with the fact that our senses bombard our brains with signals, flooding them with input, our ability to make sense of any of the world at all is nothing short of astonishing.

But it doesn’t always work with optimal efficiency, leading to confusion, and sometimes short-circuiting our perception.

That’s why optical illusions are so wonderful. They lay bare these miscues, allowing us to perceive them and understand them.

Here’s a great example of this: Watch this looping animated GIF (adapted from a demo by Michael Bach). You’ll see two sets of parallel lines moving in perpendicular directions … until the green squares pop up.

Motion Binding illusion

Adapted from Michael Bach

Do you see the illusion? At first, the two sets of lines appear to move independently of each other, moving back and forth at a 45° angle, perpendicular to the motion of the other set of lines. When I watch, my brain has no trouble separating them.

But then those squares pop up, and suddenly the four lines are all moving in sync, appearing like the attached sides of a square moving in a circular motion! The illusion is very strong.

This illusion is due to “motion binding.” This is where you see two or more sets of objects moving, and our brains let the motion of one set influence how we perceive the motion of the other. We see the two motions bound together, even if they aren’t.

It’s not a problem when the lines are separate. Those gaps are important, because it’s a clue to our brains that the two sets of lines are indeed different. But cover up the corners, and that piece of information is lost. The brain tries to link them together, and the motion suddenly becomes coherent as a whole.

I’ve seen lots of discussion about this online, but no one points out an important part: the lines themselves. Each line is a single, solid color. That doesn’t matter when the corners are not covered; the lines are moving in and out. But when the corners are covered, our brains interpret the motion as not just in and out, but also side to side a bit, sliding along their own length. But that motion is an illusion. It’s not real. It’s only the green squares covering up the gaps that makes it seem like the lines are sliding.

If the lines were not a solid color, but instead broken up into black and white squares along their lengths, that would be another clue to their motion, and the illusion would vanish, or at least be much harder to sustain (for more about this, read the demonstration on the right column of page 185 of this book).

I find this fascinating, and really engaging to play with. What happens if instead of looking over the whole picture, you instead concentrate on the motion of a single side of the “square”? If I do that, I can see the individual motions again, even when the green squares appear. But my grasp is tenuous, and if I lose my concentration suddenly, it’s a gyrating square again.

Amazing. And a very important lesson: What you see in the world may not be what’s really happening. Our eyes and brains are very, very easy to fool. We see patterns where none exist, no patterns where they do, motions when there are none, and more.

Seeing is not believing. Or at least it shouldn’t be. Remember that when someone reports a UFO, or a ghost, and says, “I know what I saw!” Because I’d be willing to bet they really don’t.

I love illusions, and how they show us not to necessarily trust our senses. Here are some examples that will hurt your brain.

Tip o’ the Necker cube to @nidavellir and to Slate video team member Shon Areih-Lerer for creating that animated GIF.

April 18 2016 11:45 AM

How Do You Get Better Science in TV And Movies? You Have to SEE.

Oh, do I love science fiction on TV and in the movies. I’m grooving on The Expanse, 12 Monkeys, Agents of S.H.I.E.L.D., and more. The science in a lot of these productions may not be perfect, but it’s pretty dang good. Certainly way better than it was even a few years ago.

A big reason for that is SEE: the Science and Entertainment Exchange. This is a program by the National Academy of Sciences—a very prestigious group—to increase the quality of science and the depiction of scientists in the media. I love this idea; most writers of these shows aren’t experts in the science, and when they talk to scientists, they can discover storylines they wouldn’t have even known existed.

The video network Great Big Story just put out a lovely short video showing a great example of this: How SEE got Agent Carter producer Wendy Wimming in touch with physicist Clifford Johnson to add some realism to the second season:

When I watched the second season of Agent Carter I smiled at the physics references; they rang true, and I knew SEE was involved.

I’ve worked with SEE for many years now; they put me in touch with a video game company to help them add real astronomy to the story, I’ve done several panels they’ve put together at San Diego Comic-Con, I’ve spoken at the Director’s Guild in L.A. on a panel they organized about the end of the world (and I got what is shirley the single greatest gift in my life from that), I’ve written for their website, and Rick Loverd, featured in the video above, is a good friend. I even helped him a tiny little bit on his comic book Venus.

So yeah. I’m a big fan of theirs. They do good work, getting more and better science out into the public. And in the end, they help make stories better.

And, as a good doctor once said, “We're all stories, in the end. Just make it a good one, eh?”

P.S. If the Agent Carter storyline of actress-and-scientific-genius Whitney Frost sounds familiar, she was based on real life as well, though I don’t think Hedy Lamarr was infected with a bizarre form of quantum matter.

April 18 2016 9:30 AM

The Taste of Alien Dust

The Cassini spacecraft is the size of a school bus and is loaded with all kinds of detectors to analyze the mighty planet Saturn, its atmosphere, moons, rings, and environment. Apropos of that last bit, one instrument, the Cosmic Dust Analyzer, was designed to let tiny grains of matter slam into it, so it can analyze their composition, mass, and even how fast they were going.

The CDA has sampled millions of dust particles that have flown into its maw, mostly ice and silicates originating from the moons around Saturn (most notably Enceladus).

But 36 of these dust grains stand out. Why? Because they came from interstellar space.

These three dozen bits of cosmic detritus stood out from the millions of others due to their high velocity: They slammed into the detector at speeds of 20 kilometers per second, or 72,000 kph. That’s extremely fast, far faster than you’d expect any dust around Saturn to move. In fact, it’s well beyond the escape velocity of Saturn at the distance of Cassini, so it’s very, very unlikely they originated from there.

Also, the direction these particles came from was another tipoff. They came from the local interstellar cloud.

The Sun orbits the Milky Way galaxy on a vast circular path, taking roughly 240 million years to complete, even though it’s moving along its orbit at a whopping 200 km/sec. There are huge numbers of clouds of gas and dust orbiting the galaxy as well, and it so happens the Sun is in one now. It too is moving rapidly around the galaxy, in a slightly different direction than the Sun is. In the end, it and the Sun are moving relative to each other at a speed of roughly 20–25 km/sec.

Sun direction around the galaxy
The Sun moves one way, the cloud another, so dust coming the cloud is easier to detect.


Aha! That’s why scientists are confident the grains detected by the CDA aren’t from around here. Not only that, but they only see them when the CDA is pointed into the direction of the Sun’s motion relative to the cloud, when you’d expect to see more of them.

This is very cool; we get to sample dust from between the stars! This isn’t the first time we’ve seen them, I’ll note: Ulysses and Galileo, two earlier spacecraft, also found some, and the aptly named Stardust, a mission to capture particles from a comet’s tail, also found seven grains likely to be from interstellar space. We also have some locked in meteorites that formed when the solar system was still forming, but those aren’t as pristine as ones captured in space.

As you can tell, we don’t see many of these particles, so adding 36 to the sample size is a big deal. The scientific bounty here is rich.

For example, the CDA could also tell what the grains are made of. The particles have magnesium, silicon, iron, and calcium in them at around the same ratio as they appear in the Universe at large, as well as carbon and sulfur in lower abundances. Interestingly, it was expected that any grains found would be diverse, each grain different than all the others. Instead they were surprisingly uniform. This may be because they’ve been “processed,” suffering repeated passages through shock waves generated by exploding stars. This would vaporize and recondense the grains, making them more uniform.

Imagine! These grains were formed millions or billions of years ago, possibly tens of thousands of light-years from Earth. During that time they’ve been moving around the galaxy at high speed in their home cloud, buffeted and jostled by exploding stars, until finally they found themselves moving through our solar system. A giant ringed planet loomed ahead, tens of thousands of kilometers across, but they missed that … only to fall into the cosmic bull’s-eye of Cassini’s dust instrument and vaporize against its detector.

An ignominious fate? Not at all, at least, not from our point of view. We may be stuck on Earth, for a time perhaps, but we have sent our proxies out into space, and we have tasted the stars.

You can fault humanity for a lot of ills, but sometimes, when we reach beyond ourselves, when we yearn to understand the Universe, we can truly be a wonderful species.

April 17 2016 9:30 AM

Spectacular Drone Ship (and Rocketcam!) View of SpaceX Booster Landing

Apropos of nothing, I just want to show you this amazing photo from SpaceX showing the Falcon 9 first stage booster landing on the drone ship, as seen from that ship:

Seriously. C’mon.

There are more photos like this on the SpaceX Flickr page.

April 16 2016 9:30 AM

The New World: March 2016 Is the Sixth Temperature Record-Breaking Month in a Row

October. November. December. January. February. And now March.

For the sixth month in a row, we’ve had a month that has broken the global high temperature record. And not just broken it, but shattered it, blasting through it like the previous record wasn’t even there.

According to NASA’s Goddard Institute for Space Studies, March 2016 was the hottest March on record, going back 136 years. It was a staggering 1.28°C above average across the planet.* The previous March record, from 2010, was 0.92° above average. This year took a huge jump over that.

Welcome to the new normal, and our new world.

As you can see from the map above, much of this incredible heat spike is located in the extreme northern latitudes. That is not good; it’s this region that’s most fragile to heating. Temperatures soaring to 7° or more above normal means more ice melting, a longer melting season, loss of thinner ice, loss of longer-term ice, and most alarmingly the dumping of billions of tons of fresh water into the saltier ocean which can and will disrupt the Earth’s ability to move that heat around.

What’s going on? El Niño might be the obvious culprit, but in fact it’s only contributing a small amount of overall warming to the globe, probably around 0.1° C or so. That’s not nearly enough to account for this. It’s almost certain that even without El Niño we’d be experiencing record heat.

Most likely there is a confluence of events going on to produce this huge spike in temperature—latent heat in the Pacific waters, wind patterns distributing it, and more.

And underlying it all, stoking the fire, is us. Humans. Climate scientists—experts who have devoted their lives to studying and understanding how this all works—agree to an extraordinary degree that humans are responsible for the heating of our planet.

JMA temperatures
The Japanese Meteorological Agency measured similar temperatures as GISS (though it uses a different baseline for the average). Note the trend. See a "pause"? I don't.

Japanese Meteorological Agency

That’s why we’re seeing so many records lately; El Niño might produce a spike, but that spike is sitting on top of an upward trend, the physical manifestation of human induced global warming, driven mostly by our dumping 40 billion tons of carbon dioxide into the air every year.

Until our politicians recognize that this is a threat, and a very serious one, things are unlikely to change much. And the way I see it, the only way to get our politicians to recognize that is to change the politicians we have in office.

That’s a new world we need, and one I sincerely hope we make happen.

*GISS uses the temperatures from 1951–1980 to calculate the average. The Japanese Meteorological Agency uses 1981–2010, which gives different anomaly numbers, but the trend remains the same. Realistically, the range GISS uses is better; by 1981 global warming was already causing average temperatures to rise.

April 15 2016 9:15 AM

A Tale of Three Jupiters, Part 4: Great Jupiter’s Ghost!

Three recent news stories have come out, all dealing with exoplanets—alien worlds—that have something in common with Jupiter. Part 1 was on a solitary starless exoplanet, Part 2 was about a double of our own Jupiter, and Part 3 was about a planet in a triple-star system. I was going to end it there, but then realized I could do another installment of this increasingly inaccurately named trilogy. So here’s the final chapter, appropriately enough about a planet that’s no longer there.

Thousands of years ago, a star died.

It was running out of nuclear fuel in its core, sending paroxysms throughout the star. It blew off a wind of gas and dust, material that had once been part of its outer layers. It did this again and again, until the white-hot core itself was exposed. This dense ball of compressed matter—a nascent white dwarf—emitted fierce amounts of ultraviolet light, exciting the atoms in the expelled material, causing it to glow.

Thus NGC 3242 was born, a new object from the ashes of the old.

This object is nicknamed the Ghost of Jupiter because it’s roughly the same apparent size as the planet when seen through a telescope. In fact, it belongs to a class of objects called planetary nebulae because they resemble planets in small ‘scopes.

NGC 3242 is about 1,000 light-years away, and a couple of light-years across—20 or more trillion kilometers—so it may be a tad larger than Jupiter physically.

The image above was taken by the Spitzer Space Telescope in 2013, and shows the nebula in infrared. What you see as red is actually light with a wavelength of 8 microns—10 times longer than what our eyes can see. At that wavelength, cold dust glows strongly, so you’re seeing the complex carbon and silicate molecules blown out by the star millennia ago. You can even see concentric circles; those are actually shells of material ejected whenever the star had one of its spasms as its fuel ran out.

Overall the nebula is circular (really spherical), but the inner core is noticeably elliptical. Why? Oh, this is where irony comes in quite strongly.

Hubble image of the nebula
The inner region of the nebula seen by Hubble. Much of the structure here must be due to something that spun up the dying star.

Danny LaCrue & the ESA/ESO/NASA Photoshop FITS

The noncircular inner regions of planetary nebulae were a mystery for a long time. I studied these objects for my master’s degree, in fact, and in 1990 we didn’t really know why the inner parts were shaped the way they are. In the paper we published, my adviser, Noam Soker, made an aside in one section that, at the time, was a weird claim: Perhaps the star had planets.

When it began to run out of fuel, the star expanded into a red giant. Planets close in would be consumed. They orbited faster than the star spun, so they would spin it up, making it rotate faster. Centrifugal force would flatten the ejected gas and dust, creating a more (American) football-shaped object. The outer parts of the nebula were ejected before this happened and would be more spherical.

Then an amazing thing happened: Five years later the first exoplanet orbiting a Sun-like star was found. Not only that, but it was a planet more massive than Jupiter, orbiting extremely close in to its star. Over the next few years more such “hot Jupiters” were found, and now we know they’re actually rather common.

Voilà! That likely explains the inner regions of elliptical planetary nebulae! Noam was right. At least partially; it’s also possible these stars were binary, and consumed their partner star. But massive close-in planets work too, and we know they exist.

That may very well have been the case for the central star of NGC 3242. Perhaps it had planets, maybe even a hot Jupiter making a tight orbit around it. It expanded, got spun up by the planet, and started emitting that flattened wind which formed the elliptical shape we see. As for the planet itself it would fall to the star’s center, evaporating fiercely, until it merged with the star itself, eaten by its parent.

Do you see the irony? The Ghost of Jupiter may actually very well be the ghost of a Jupiter-like planet!

And that, it seems to me, is a fitting way to end this four-part trilogy.