Bad Astronomy
The entire universe in blog form

April 21 2015 4:02 PM

Is That Viral Quadruple Rainbow Picture Real?

This morning a picture tweeted by Nineteenth Amendment CEO Amanda Curtis on Long Island quickly went viral: It shows what looks like a quadruple rainbow!

I got some folks asking me if it’s real, and my immediate reaction is: Yup. Seriously, this doesn’t look faked to me, because I’ve seen this sort of thing before.


Double rainbows are fairly common (despite the meme). I’ve seen dozens of them; they’re caused when the sunlight hitting raindrops is particularly bright. The primary rainbow (the one you usually see) can be blazing, and you get a fainter but sometimes still quite bright secondary outside it, with the colors reversed. The primary forms when light is reflected inside a water drop once; the double is when the light’s reflected twice in each drop.

So why are there four rainbows? The angle of the weirder, more vertical bows is what gives it away. If the light forming rainbows reflects off a body of water (say, a lake, pond, or even standing water on a road), you get another set of rainbows cast at a different angle. I’ve never seen this myself, but there are plenty of pictures of it online.

So the picture is real! One thing I’ll add is that I think the colors have been enhanced; they’re a bit too garish to be real. But lots of phones do that, and of course people use filters when posting pictures all the time. But physically, yes, it’s real.

There you go. And it proves, once again, that you should heed my advice: Always look up. You never know what’s going on above your head.

Video Advertisement

April 21 2015 12:44 PM

Sen: Probing an Alien Solar System

In 2008, the nearby star HR 8799 earned a place in the history books: It was the first star orbited by multiple planets directly seen in photographs. This was quite an accomplishment; stars are billions of times brighter than planets, so getting actual direct images of the planets is incredibly difficult. And here, orbiting this star, four have been discovered!

In the years since, the system has been extensively studied, but it’s still difficult. That’s why a team of astronomers created LEECH—the Large Binocular Telescope Exozodi Exoplanet Common Hunt.* This system is optimized to look at the exoplanets around nearby stars and create a base of observations from a single telescope and camera. Most exoplanets are observed by different telescopes, which introduces uncertainties when you try to compare the observations. Using LEECH should reduce that considerably.


I wrote about this, and the conclusions about the HR 8799 system found, in my biweekly column for It’s subscription only, but for about the cost of a magazine subscription you get a lot of good stuff. And, of course, there’s a ton of free content on the site as well. You should check it out.

*"Exozodi" refers to zodical light, the glow due to dust orbiting stars. This happens in our own solar system, and can be seen from exceptionally dark sites.

April 21 2015 7:30 AM

The King and Queen of Planets

Right now, two planets dominate the sky after sunset: Venus in the west, and Jupiter high to the south. Both are amazingly bright, clearly ruling their areas of the sky. Both planets are also in parts of their orbits where they’re relatively close to Earth, providing excellent viewing opportunities.

Danish “amateur” astronomer (and frequent BA contributor) Emil Kraaikamp took full advantage of this, using his custom-made 40-centimeter Dobsonian telescope to take images of the planets that are simply and truly jaw-dropping.


First, Jupiter, as seen on April 6, 2015:

Holy wow! The detail is extraordinary. This kind of image is made in a very clever way: using video to maximize the clarity. Our atmosphere roils overhead, blurring out the small details on very short timescales. Taking even a 0.1 second exposure means losing resolution.

But by taking thousands of much faster video frames, the images are sharper. Then, software can pick out the sharpest details in each frame, and assemble them like a jigsaw puzzle to put together a mosaic of the full image. The results are, clearly, stunning!

I was astonished to see the detail on Io, the moon you can see on the right (and that’s casting its shadow on Jupiter’s cloudtops, too). If you look carefully you can see some surface features on the moon, which is pretty amazing considering it’s about the same size as our Moon and was more than 700 million kilometers away when this shot was taken!

Kraaikamp also got images of Jupiter’s huge moon Ganymede and saw amazing detail on it:

Ganymede, the largest moon in the solar system.

On the left is his final video frame stack, and on the right a simulated view using space probe imagery, scaled to the same size. As you can see, quite a bit of detail is discernible. I’ll note that Ganymede is bigger than Mercury (and almost as big as Mars), but that does nothing to mitigate how cool this picture is.

But even then, the most amazing thing he sent me was this picture of Venus he took on the same night. I could scarcely believe it:

I'm your fire, at your desire.

Venus is famous for having almost no features visible; the planet is enshrouded in thick, featureless clouds. The only way to see details at all is to look in the ultraviolet … which is what Kraaikamp did.

Material in the clouds absorb ultraviolet instead of just reflecting it all away like they do with visible light. This reveals features in the top of Venus’ ridiculously thick atmosphere, including wind patterns. Kraaikamp has many such images of Venus on his site. Go look, and check out his Jupiter pix, too (especially this animation).

In fact, take a moment and just peruse his whole site. He has a ton of great photos there.

April 20 2015 7:00 AM

BA Video: An Electrifying Volcano

In the Mexican state of Colima there lies an active volcano. Actually, Mexico is lousy with volcanoes, but this one has been doing more than its share of rumbling and grumbling lately.

Photographer César Cantú went to the Colima volcano to photograph it recently, and what he got was way more than he hoped for: huge lightning discharges blasting through the ash cloud! This type of event is well-known, but not terribly well-understood. I do love a scientific mystery, which is why this event (and a time-lapse Cantú made) is the subject of this week’s Bad Astronomy Video.


A funny note, too: The other day, on Twitter a friend of mine posted a picture of the lightning in the ash cloud. But it was credited to someone else: Hernando Rivera Cervantes! I immediately wondered if there was a bit of picture pilfering going on, so I sent a note to Cantú via his Facebook page. He replied back almost immediately: Cervantes is a fellow photographer, and was in fact standing next to Cantú taking pictures at the same time.

It wasn’t plagiarism. It was essentially the same photo taken by two different people! I wasn’t expecting that. But I’m glad no one was trying to get credit for Cantú’s photo.

Speaking of which, I’ll soon be back at Kilauea in Hawaii, very near the lip of the Halema’uma’u vent. While I certainly don’t think we’ll see lightning (it’s venting sulfur dioxide, not ash), I can hope to take some more shots of the lava pit illuminating the plume. Volcanoes don't have to be disastrously dramatic to be exceptionally enthralling.

Correction, April 20, 2015: This post originally misstated that Halema'uma'u was on Mauna Kea. It's on Kilauea. 

April 19 2015 12:00 PM

Aloha! Come to Science Luau 2015!

Update, April 19, 2015, at 23:50 UTC: Well, that was fast: We sold out. However, we have a waiting list, so if you want to go, please sign up! You never know.

On Sept. 14–20, come to Hawaii to soak up some science at Science Luau 2015!


I’m pretty excited about this. My wife, Marcella, and I run a company called Science Getaways, where we take normal vacations and make them awesome by adding science. We’ve had many awesome trips over the past few years, and we decided it’s time to up the ante.

And up it we did. Hawaii was the obvious choice; the Big Island has a lot to offer for a week of fun and relaxation, and Science Luau will be equal parts tropical paradise and sciencey goodness.

Fairmont hotel
The view from the Fairmont Hotel. Not too bad.

Photo by the Fairmont Hotel

We’ll go night snorkeling with manta rays, tour a family-owned coffee farm,* hike around the active Kilauea volcano (and stay after dark to watch the lava illuminate the gas plume billowing out of the Halema’uma’u vent—yeah, click that link) and take an optional trip to the Mauna Kea summit to watch the Sun set from over 4,200 meters above the Pacific. After that we’ll drive down to the visitor’s center (at about 3,000 meters) to star gaze, of course! No Science Getaway is complete without that. And my favorite part: We’ll visit a seahorse farm where they’re working to keep the critters from going extinct. You’ll even get to hold one underwater; that’ll be an experience you won’t forget.

Yes, that's me holding a seahorse.

Photo by Phil Plait

We’ll be staying at the luxurious Fairmont Orchid hotel on the west side of the island, right on the Kohala coast. And because we’re doing this during the off-season, the hotel and beaches are likely to be relatively quiet, giving us a cozier feel to the event. We also got very good group rates for the hotel, so if you’ve ever wanted to visit the area this is the way to do it.

Best of all, you’ll be spending a week with like-minded nerds sharing all this beauty and wonder. We’re always amazed at how many friendships blossom from these Getaways. It’s really wonderful.

For details, go to the Science Luau 2015 page. I hope to see you there! Mahalo!


Photo by Phil Plait

*Ask any professional: Science runs on coffee.

I’ll note that Science Luau starts right after HawaiiCon, the island’s only and very fun science-fiction convention. I went last year and had a great time; we are not affiliated with each other in any way, but I figure if you’re interested in the Luau, HawaiiCon might geek you out as well.

April 18 2015 7:30 AM

Aurorae Out an Airplane Window

It’s fun to look out an airplane window at night and try to identify stars above and cities below. But I’ve never had as good a view as this:

That time-lapse video is by Paul Williams, a systems designer based in London. He flies to San Francisco many times a year, and the shortest route takes him over northern Canada (it may not seem like it should at first, but check out the geometry of great circles; this may help too). Armed with a Canon 6D and a small, flexible tripod he can attach to his backpack, he took 1,200 photos out the window to create that animation.


He’s done this many times, and I’ve written about his work before. I like this video, too, since it shows a reddish/purple tinge to the light, caused by nitrogen and oxygen molecules in the upper atmosphere getting slammed by subatomic particles from the Sun.

And because why not, here's some footage from "skydivephil" showing the aurorae from Iceland ... in real time. It's amazing how quickly they can move. Make sure watch to the very end for a surprise (which was shot in Lapland).

I have a page with tons of links all about what causes aurorae, why they get the colors they do, and more. Lots of fun science there. And of course, watch more of Williams’ videos and check out his Flickr page, too. The aurora season is far from over, so there may be more lights in the sky to come.

And if you’re on a night flight, grab a window seat. Who knows what you’ll see?

April 17 2015 11:15 AM

Crash Course Astronomy: Mercury

Quick: What’s the hottest planet in the solar system?

You might think Mercury, because it’s the closest to the Sun. But in fact, it’s not! Venus is hotter due to its runaway greenhouse effect.


But that’s not to say Mercury isn’t loaded with astronomical goodness. It’s got a lot going on: craters, rupes, a swollen iron core, and a frosty surprise in its boreal craters.

So please watch, listen, and enjoy this week’s episode of Crash Course Astronomy: Mercury.

And a side note I can’t help but mention: Right now as I write this, NASA’s MESSENGER probe has but weeks to live. Out of propellant, by the end of April it’s destined to slam into Mercury’s surface after more than 4,000 orbits of service to science.

Crash Course Mercury, indeed.

April 17 2015 7:00 AM

Ceres Spins Under Dawn

The Dawn spacecraft recently slid ever so gently into the embrace of Ceres, the largest asteroid in the main belt between Mars and Jupiter. It actually flew past Ceres, slowing itself with its ion engine in a long, looping trajectory that kept it over the tiny world’s unilluminated half.

But then, a few days ago, it got close enough and in the right geometry to begin observations of some sunlit real estate on Ceres. It did this by peeking over the north pole of the asteroid, and the result was an amazing animation of Ceres rotating:

The rotation of a distant world.



That’s phenomenal! These images were taken on April 10 from a distance of 33,000 kilometers and are the highest resolution images we’ve seen so far.

Ceres is a mess. It’s heavily battered, as you might expect for the largest airless body in its neighborhood surrounded by a few billion smaller ones. As I wrote about before, a lot of the craters look to have flat floors, which is what you expect on a world where there’s lots of ice under the surface; that stuff can flood in and fill the crater after an impact (materials with lower tensile strength tend to leave flatter floors, but the ice could also melt and flow in as well).

Some of the craters have central peaks, which is also common in larger impacts as material pushed out by the huge energy of the impact rushes back into the center (like a drop of milk or water that splashes up from the center when you pour the liquid into a glass—this is called isostatic rebound).

Soon enough there will be a lot less guesswork, once Dawn settles into its mapping orbit. We’ll see much better images then and get a much better understanding of this weird little world.

April 16 2015 7:00 AM

To Mars

Why is Elon Musk so hellbent on going to Mars?

There are two answers to this. One is the actual answer. The other isn't exactly wrong—it’s technically correct—but it’s incidental. And it turns out that’s not even really the right question.


Bear with me a moment. You need a little background.

I’ve been interested in SpaceX for a while now. Years ago, when Musk announced he was going to launch the first privately funded liquid fuel rocket into orbit, I figured he might be able do it—it’s a daunting but not impossible task. Still, I was pretty skeptical. But he did have a bit of a leg up: He’d been pouring money into SpaceX, a personal fortune made from running earlier companies like PayPal and (and now SolarCity and Tesla).

It takes more than money, of course, to build a successful rocket program. But my doubts were lessened considerably in September 2008, when, after three previous rockets had failed to achieve their mission goals, a Falcon 1 rocket reached orbit around the Earth. Now, years later, with the Falcon 9 proving to be a reliable vehicle and several successful launches to the International Space Station and beyond under its belt, SpaceX has shown it can look even farther.

This was all on my mind when I got a chance recently to take a tour of the SpaceX construction factory and corporate HQ in Hawthorne, California. I had been invited by Musk, who, to my surprise, follows me on Twitter and reads this blog. (Full disclosure: SpaceX paid for the trip.) I was excited by the prospect—duh—and the place did not disappoint.

As I walked in, for a brief moment it felt more like a company office than a factory. But after a short walk from the front door and past the lobby it’s like, seriously, the scene in Willy Wonka when everyone steps off the elevator into the chocolate factory.

Phil Plait and Dragon
The very first Dragon capsule that went to space. Note the scorch marks.

Photo by Phil Plait, with an assist by SpaceX

Hanging from the high ceiling is the actual first Dragon capsule to be sent into orbit, scorch marks from its atmospheric re-entry licking up the sides. Nearby, two other capsules are in various stages of construction. A half dozen Merlin engines are lined up, already tested once under fire, now being retooled and checked out for their next launch. Two enormous Falcon 9 boosters lie side by side in one corner of the factory. From the café on the mezzanine I can see twin enormous nose cones sitting in the next room, waiting to be used on the demo flight of the Falcon Heavy, a huge rocket that is the next generation of SpaceX boosters. And all this is open, on the floor, available to be gawked at.

During the tour I also saw dozens of people working on the various components of the Falcons 9 and Heavy. It was hard not to notice that they all seemed to be in pretty good spirits—smiling, laughing, talking, gesticulating. Looking around, that wasn’t too surprising. A sense of pride and excitement would be natural working in such a place. But there was something else, too, that I couldn’t quite put my finger on.

Before the thought could crystallize, the tour was over. I was brought over to the admin section of the factory to meet with Musk. I’ll spare you the personal details; you can find those all over the Web. What impressed me the most was his matter-of-fact attitude; not surprisingly he is a man who knows what he wants and how to achieve it. With his track record, he’s earned that confidence.

We talked about various topics for a while—the movie Interstellar, the history of SpaceX, terraforming Mars … and that was when I said something dumb.

“I know Mars is a long-term goal for SpaceX,” I started. Then, pretty much as an aside, I said, “because you want to retire on Mars … ”

Musk got a pained look on his face. “No, that’s wrong. That’s not why I want to get to Mars. That quote is from an article in the Guardian. They pushed me for a sound bite, asking if I wanted to retire on Mars. I eventually said yes. When I retire—hopefully before I go senile—and eventually die, then Mars is as good a place to die as any.”

That line made me laugh; it’s far better than anything printed in the Guardian article.

But still, I was taken aback. “OK then, the article wanted a sexy quote and got one. But if that’s not the reason, what is it?”

Musk didn’t hesitate. “Humans need to be a multiplanet species,” he replied.

And pretty much at that moment my thinking reorganized itself. He didn’t need to explain his reasoning; I agree with that statement, and I’ve written about it many times. Exploration has its own varied rewards ... and a single global catastrophe could wipe us out. Space travel is a means to mitigate that, and setting up colonies elsewhere is a good bet. As Konstantin Tsiolkovsky (the father of modern rocketry) said, “The Earth is the cradle of humanity, but one cannot live in the cradle forever.”

Moon and Mars bootprint
From the Moon to Mars.

Photo by NASA

So I hardly needed to mull that over. But what did happen is that two things became clear in my head simultaneously. One was that Musk’s answer was simply stated, plainly obvious to him, but to the public it’s not. It seems like science fiction.

But with his immense factory sitting directly behind me, there was no doubting this was not the wild dream of a sci-fi fan. This is reality. The dichotomy between public perception and what was really happening here was never clearer to me.

The second was the crystallization of what had been nagging me during the tour.

The overall atmosphere in the factory was one of working at a progressive company on an exciting project. Of course: They build rockets. But the feeling I couldn’t put my finger on before suddenly came into focus. The attitude of the people I saw wasn’t just a general pride, as strong as it was, in doing something cool. It was that they were doing something important. And again, not just important in some vague, general way, but critical and quite specific in its endgame: making humans citizens of more than one world. A multiplanet species.

It’s easy to dismiss this statement, think of some snark as a way to minimize it and marginalize it as the thinking of a true believer. But—skeptic that I am—I’ve come to realize this is not minimal. It is not marginal. This is a real, tangible goal, one that is achievable. And SpaceX is making great strides toward achieving it.

That’s when I also realized that the initial question itself was ill-posed. It’s not why Elon Musk wants to get to Mars. It’s why he wants humanity to get there.

I think that's a pretty good idea.

Days later, back home in Colorado, I went out on my porch just after sunset and took a look at the sky to the west. Venus was shining like a beacon, brilliant and beguiling. Just below it, close in the sky but much farther away in reality, was Mars, a duller red in color and far fainter. But of the two, my gaze kept returning to Mars.

How long before we go there? Is the first human to make their bootprint in the ochre dust already leaving footprints here on Earth?

I suspect so. And it may not be all that long before they’re on their way.

Postscript: There’s been some discussion lately among space and science communicators about the way we talk about space exploration and how it relates to different cultures (for example, DNLee has thoughts on this). This took place, coincidentally, around the same time I wrote this article, and it’s an interesting line of discussion, one I’m mulling it over. I’ll have more to say about this in the near future, I think.

April 15 2015 7:00 AM

Video of the SpaceX Booster Landing ... Kinda

Update, April 15, 2015, at 22:15 UTC: SpaceX has released a full video of the booster landing on the barge! Watch it below. You can see it land, but it appears to have a bit of a tilt when it sets down. There's a small plume coming from the top, an apparent attempt to compensate, but it's not enough. The booster tips over and explodes. You can see debris arcing all over the place. Very dramatic! 

On Tuesday, SpaceX successfully launched a Falcon 9 rocket with a Dragon capsule loaded with supplies for the International Space Station. Astronaut Samantha Cristoforetti will grapple the capsule on Friday and berth it to the ISS.


The launch was also the second try at landing the first stage Falcon 9 booster on a floating barge in the Atlantic. The first attempt in January was almost successful, but the steering fins ran out of hydraulic fluid causing a spectacular crash-and-burn of the booster.

This second attempt nearly made it as well. The booster found the barge, and actually seems to have landed vertically, but came in with a little bit too much sideways motion, tipping it over.

The video stops just short of the booster heeling over and falling.

Mind you, this is still pretty good. Remember, no one has ever tried anything like this before during a launch, and almost everything went correctly. Clearly, of course, there are still a few things to be ironed out.

Elon Musk himself knows this. After the video came out, he tweeted this:

It’s always nice to treat oneself.