Bad Astronomy
The entire universe in blog form

Sept. 2 2015 1:38 PM

INTENSE Aurora Display Over Sweden!

Astrophotographer Göran Strand was out on the night of Aug. 26 in Östersund, Sweden, when the sky erupted in auroral flames! He caught the whole thing in both time-lapse and real-time video, and it’s stunning.

Wow! Aurorae are formed when subatomic particles from the Sun are funneled down into our atmosphere by the Earth’s magnetic field. They zip down into our air, energizing atoms and molecules, causing them to glow. Each particle makes a more-or-less vertical line of glow, and huge streams of them make thin sheets of emission.


When we see these sheets edge on they can look like arcs, when seen from the side they look wider. When they’re directly overhead they fan out, creating what’s called a “corona” (you can see that starting at about 1:30 into the video).

I’ve written a FAQ about aurorae with links to how they form, why they have colors, and more.

And I had to laugh: At about 2:10, did you see the giant goblin face flashing pink and green?

aurora goblin

Photo by Göran Strand, from the video

I love stuff like that!

Strand is an amazing sky photographer, and I’ve featured his work many, many times here. Go check it out.

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Sept. 2 2015 9:30 AM

Solar Photobomber

So you’re taking telescopic photographs of the Sun, watching the solar disk seethe under intense forces while blasting huge, towering prominences tens of thousands of kilometers into space, when your photo is completely ruined by a rude photobomber:

Sept. 1 2015 9:45 AM

Satellite Re-Entry Surprises Hawaii

Folks in Hawaii got a shock—or a thrill, depending on how much they knew about what they were seeing—when a very bright and dramatic “shooting star” blew across their skies on Monday.


That’s one example of many (one I saw had a lot of swearing in it, which doesn’t surprise me at all).

Was it an asteroid? A sign of the Apocalypse? Superman?

Nope. It was the re-entry of Cosmos 1315, a Soviet-era satellite launched in 1981. The giveaway for me that this was a satellite and not a natural meteor was how slowly it was moving. Typical meteor speeds are many dozens of kilometers per second, and they zip across the sky in a second or two. Satellites orbit at about 8 kilometers per second, and can take a minute or more to clear the horizon. Also, satellites tend to break apart as the pressure and heat of re-entry take their toll, and you can see that’s what’s going on in the video.

Also, the Aerospace Corp. put the re-entry track right over Hawaii at just the right time. Seems pretty cut and dried.

I’ve seen hundreds of meteors (probably thousands), and only one satellite re-entry, a Russian booster that burned up over the U.S. East Coast back when I was in grad school. It was pretty awe-inspiring, moving slowly and gracefully across the sky, with bits falling off. A meteor usually stays in one piece unless it’s a really big one.

There are a lot of birds up there, and this stuff comes down all the time. Usually they fall over the ocean where no one sees them (the planet is mostly water, after all), but when they come down over populated areas we usually get lots of dramatic video and photographs.

Cygnus reentry
Astronauts on the space station took this photo of the Orbital Sciences Corporation's Cygnus cargo ship re-entering in 2014.

Photo by ESA/NASA

Sometimes these can be a danger—ask this guy who lives downrange of a Chinese rocket launch site—but that’s extremely rare. Still, it’s something aerospace companies and national governments need to be concerned about, especially during test launches; debris from SpaceShipTwo came down in the Mojave after the test vehicle crashed in 2014, narrowly missing bystanders.

But what this tells me is—and stop me if you’ve heard this before—you need to look up! You never know what’s up there … and what’s coming down.

Tip o’ the heat shield to David Dickinson.*

*Correction, Sept. 2, 2015: This post originally misspelled David Dickinson’s last name.

Aug. 31 2015 10:00 AM

Inundated by Global Warming

Do you think global warming is something that only affects us sometime in the future, decades or centuries from now?

Think again. Our planet heating up is affecting us now, and has been for decades. We’re already seeing a lot of serious problems due to it: extreme weather, more devastating hurricanes, wildfires, and sea level rise.


Of all these, the last seems most like science fiction. Seriously, the levels of the ocean are going up? It can’t be much, right?

Think again, again. NASA just released results from several satellite observations going back to 1992. Those 23 years of data show that the oceans of the planet have risen substantially in that time: more than 6 centimeters (2½ inches) on average, with some places on Earth seeing more than 22 centimeters (9 inches)!

This animation shows where the levels are going, and by how much:

The global sea level rise is driven by two major factors: One is that as water warms, it expands, raising the sea level. The other is that Greenland and Antarctica are melting, dumping 450 billion tons of water into the oceans every year. Every year.

glacier rivers
Rivers of water in Greenland created as ice melts. This flows to the bottom of the glaciers through holes, which helps glaciers retreat faster and dumps more water into the ocean.

Photo by NASA Earth Science News Team

So overall sea level is rising, but in some places it’s rising faster than others. For example, in the Pacific, heat travel east to west, so the eastern coasts of the Philippines and Japan have seen huge jumps in sea level the past two decades. Interestingly, sea levels have dropped in some places. Off the northeastern shore of the U.S. you can see a drop. But in that case it’s because the Gulf Stream, a major warm ocean current, has shifted north somewhat, so levels have risen in the north but dropped in its wake to the south.

But those drops are highly localized. Globally, levels are on the rise.

global warming components
Where does all that heat go?

Drawing by Skeptical Science

The cause of all this is obvious and very real: global warming. As human activity—primarily dumping 40 billion tons of carbon dioxide into the atmosphere every year—causes the Earth’s surface temperature to go up, a lot of that energy is absorbed by the oceans, causing them to expand. Some of it is absorbed at the poles, melting ice there.

Sea ice melting at the North Pole is bad enough, but the land ice melting is nothing short of catastrophic. Climatologists have already shown that the melting of the West Antarctica ice sheet may be unstoppable. We may be locked in—that is, inevitably going to suffer from—a full meter of sea level rise, 3 feet. This may take a century or more, but it’s coming. And while that may seem like a long time, think of it this way: A meter per century is a centimeter every year, an inch every 2½ years.

Mind you, that’s vertical rise. Look at the slope of a beach and you can see that a small rise vertically means a lot of horizontal reach to the ocean, too. We’ll see beaches disappear, coastlines changed. More immediately, we’ll see storm surges do far more damage as it takes less rise in the water levels to inundate cities. Remember what the surge from Hurricane Sandy did to NYC? We’ll be seeing more and more of that.

This is the new normal. And the scary thing is not so much that the new normal is bad, it’s that with more warming, rising sea levels, and changing weather patterns, the new normal will continue to get worse. There may not be a normal any more.

Just as a reminder: With only a single exception, none of the GOP presidential candidates has a reality-based view on global warming (the exception is George Pataki, who has no chance of winning), and those views range from unsupportable by facts to unhinged in the extreme. Even those of them who admit it’s real think it’s not human caused, or that we can’t do anything about it without hurting the economy (and that is 100 percent ultra-grade fertilizer; it’s worse to wait). Even this far out it seems certain the House will go GOP again in 2016, so having a climate-change-denying president will mean at least four more years of inaction bolstered by the smoke and mirrors of the noise machine.

And don’t forget that the GOP in the House is still trying to eviscerate NASA’s Earth science budget, which goes in large part to monitoring the effects of global warming. Why? Simply put, they deny the reality all around them.

And all that time, the temperatures will rise, the glaciers will melt, the sea levels will rise, and we’ll be that much deeper into a catastrophe that is already well under way.

Aug. 30 2015 10:00 AM

Space Is Cold, but We Are Not

If you have five minutes—and I think you do—then I urge you to go take a look at this lovely and wonderful comic by French artist Boulet. Yes, there are a few typos in the translation, but it’s charming and sweet, and expresses quite a few points I strongly believe in myself.

Science is not cold, nor scientists unemotional. If we were, we wouldn’t be doing this in the first place. For so many, it is our sense of awe and wonder that drives us.


Tip o' the pen cap to Jesse Anderton.

Aug. 29 2015 10:00 AM

Crash Course Astronomy: White Dwarfs and Planetary Nebulae

I’ll be honest: Every episode of Crash Course Astronomy has been fun to write, edit, and shoot. They all really have. But the past few episodes, and the next few to come, deal with one of my favorite topics in astronomy: what happens when a star decides to give up the ghost.

When stars die all sorts of fantabulous things happen: They explode, they leave behind bizarre ultradense objects, they fling gas into space that creates amazing and breathtaking shapes and colors.


This week, CCA is about what happens after stars like the Sun die: They become white dwarfs, and in the process blow out a series of winds that become one of the most beautiful sights in the sky: planetary nebulae.

I studied the planetary nebula NGC 6286 for my master’s degree at the University of Virginia, investigating a giant circular halo of gas around it from the star’s original red giant wind. I had to simultaneously learn about planetary nebulae, the physics of interacting colliding winds, how gas radiates light, how the digital detector on the telescope worked (this was when such cameras were brand spanking new, so every thing about them was a learning experience), how to use the telescope, and how to write code to analyze the data. It was … interesting. Very difficult, but in the end I got results that were worth publishing.

My adviser, Noam Soker, is the man I mention in the video. I have never met a harder working astronomer in my life; he published a ridiculous number of papers, covering one small topic very well in each, and then moving on. I remember talking to him about why 6826 had an elliptical inner region, and he suggested it could be from a Jupiter-like planet orbiting the star. The problem was it would have to be very close to the star to be enveloped when the star became a red giant, and I thought that wasn’t possible—our Jupiter, after all, is more than 700 million kilometers from the Sun, way too far to get swallowed up! And you can’t form a planet that big that near a star anyway.

Oh, me. This was five years before the first “hot Jupiter” was found, and now I wish we had emphasized this even more in our paper instead of just adding a single line about it! It turns out they may be quite common; they form farther out from the star and migrate inward over time. I was pretty shocked when 51 Peg b was discovered, and seriously my first thought when it was announced was, “PLANETARY NEBULAE! OF COURSE!”

Yes, I think in all caps sometimes. It’s very funny to me that planets and planetary nebulae are in fact connected, especially since, despite their names, they are very, very different objects. But in science you find that everything’s connected in one way or another. It’s a tapestry, and every thread counts.

Aug. 28 2015 10:00 AM

Make Me Dream, Under the Stars

One of the things I love best is when someone looks through a telescope for the first time. Even better when it’s a kid; a simple glance through the eyepiece, a single moment, and a lifetime of joy and wonder is theirs.

During the week of the Perseid meteor shower in August 2015, two dozen high school students participated in an Astronomy Camp held by the Oregon Museum of Science and Industry. They traveled to the high desert in that state to learn how to observe the sky, and then joined up with 600 other astronomers to participate in the Oregon Star Party.


Astrophotographer Ben Canales followed them, and took footage of the events. He created this wonderful video, “Make Me Dream,” which made my heart very happy indeed.

Some technical detail: Canales used the new Sony A7 mirrorless camera, which uses new technology allowing it to shoot video at—get this—ISO 100,000 (it goes even higher, but Canales said that's the highest he could go and get acceptable noise levels, even with some fancy post-processing techniques). That’s incredible; such a high setting means the camera was phenomenally sensitive to light, which is how he was able to get scenes showing both the young students and stars of the Milky Way in the background, even out of focus (which spreads the light out, making them even dimmer). I have got to try one of those.

The last shot, showing the persistent Perseid train, is fantastic. Make sure you watch all the way to the end of the video, too.

All the sky footage was nice, but what really made my smile grow was the expressions on the faces of the students as they set up and used their telescopes. It gives a real sense of accomplishment to learn how to use a telescope; they can be finicky, and frustrating. But when things start to click, the whole sky becomes yours. When you know your way around the night sky it’s a treasure map … but it’s also the treasure itself.

Canales captures this perfectly. But what else do I expect from someone who took this picture, one of my all-time favorite astrophotos?

looking up

Photo by Ben Canales, used by permission

That is how I feel all the time when I am out under the stars. I highly recommend it. 

Aug. 27 2015 10:00 AM

Bubbly Hurricane

I used to play a lot with soap bubbles. Long after I grew up, I mean.

Scientifically, they’re very interesting; they explore such topics as thin film surfaces, optical interference, least-area surfaces, shape packing, and all kinds of chemistry.


Also, they’re pretty and silly and fun.

But one thing that never occurred to me in all that time is that soap bubbles make a pretty good stand-in for hurricanes. It might surprise you that such a delicate and fragile structure might analogize one of the most powerful and destructive events on the Earth’s surface, but sometimes in science scale isn’t a problem. It doesn’t matter if it’s small or big, the interacting forces are what matter.

My friend Dianna, aka Physics Girl, explains in this great video:

Dianna’s a great science communicator; she has a knack for making complex issues simple, but not too simple. You should check out her other videos, especially this one on mirrors flipping right and left (… or do they?), and this one on vortices in swimming pools.

Bubbles are a lot of fun, and the science they show us is astonishing and beautiful. Especially, in my not-so-unbiased opinion, when they’re on the ten trillion kilometer or so scale.

As an aside, congratulations to Dianna for now being a part of the PBS Digital Studios family! They’re partners with Hank and John Green in producing Crash Course Astronomy, so I’m a big fan of them. 

Aug. 26 2015 10:00 AM

OK, How’d That Mountain Get There?

Ceres is the largest asteroid in the solar system*. The Dawn spacecraft has been orbiting it since early this year, and a few months ago, it spotted something really weird: a 6-kilometer tall mountain just sitting all by its lonesome on the surface.

Since that time Dawn has lowered itself closer to the surface of Ceres, where it can take higher-resolution images. A new photo of the mountain has only made things weirder:


Aug. 25 2015 12:05 PM

A Sun-Diving Neighbor

I suspect that when most people think about asteroids approaching Earth, they picture them coming from deep space, out past Mars and Jupiter.

But there’s a substantial population of asteroids where the rocks spend most of their time inside Earth’s orbit, closer to the Sun. These little beasties are hard to find because they tend not to stray too far from the Sun in the sky, so they’re up mostly during the day or twilight hours.


For my biweekly column at, I wrote about a newly discovered asteroid called 2015 QM3 that is on such an orbit, swinging it past not just Earth, but also Venus and Mercury! It’s a curious object, getting close enough to all three planets that over millions of years its orbit is certainly unstable. Not many such asteroids are known (just 17!) so any time we find a new one it helps us understand the complicated dynamics of near-Earth objects.

My articles for are subscription only, but for $5 a month you get access to a lot of pretty cool astronomical info. I check it for news and interesting photos every day. You should too.

My thanks to my friend and esteemed astronomical colleague Amy Mainzer for her help with some info about QM3 … and also for announcing the asteroid in the first place