Bad Astronomy
The entire universe in blog form

April 26 2015 7:30 AM

Rising Rainbow

Aysun Ülger is, like me, someone who loves atmospheric optical phenomena. Halos, glories, aurorae, iridescent clouds … so much so she created a Facebook page where she collects such photos. She just started it, but there are already a few lovely examples there.

And this includes, of course, rainbows. Since I just wrote about that very cool quadruple rainbow in New York, I thought I’d follow up with an example of a fun series of photos Ülger took herself in Izmir, Turkey: a rainbow rising as the Sun set!

A rainbow rises
This may be the tallest picture I've ever posted by ratio.

Photo by Aysun Ülger, used by permission


Those were all taken on the same day, April 6, 2015, except for the bottom one, which she included in the series to show just how high a rainbow can get. In order (top to bottom), they were taken at 3:41, 3:50, 4:24, 4:50, 5:21, and 6:11 pm. The bottom one was taken at 5:58 pm on March 28. But due to a local time change, it corresponds to 6:58 on the later date.

raindrop refraction
Refraction (bending) and reflection inside a raindrop. Click to spectroscopenate.

Drawing by Wikipedia/KES47, adapted by Phil Plait

As I’ve written about many times, rainbows appear in the sky opposite the Sun—to see one, you have to stand with the Sun behind you. That’s because the light from the Sun bends inside the raindrop and is reflected on the drop’s backside, back toward the Sun. But not exactly: The light leaves the drop at an angle of about 138°. Only drops 42° away from the point in the sky directly opposite the Sun send that light toward you (180°–138°).

Also, the colors that make up the Sun’s white light get bent by slightly different amounts, spreading them out across the bow.

Since the arc of the rainbow is centered on the point on the sky directly opposite the Sun, a low Sun means a high rainbow, and a high Sun means a low rainbow. As Ülger waited, the Sun set, so the rainbow got higher. You can even see a double rainbow (called the secondary) and Alexander’s dark band, the darker region between the two bows.

Too bad she couldn’t get a time lapse of this! But she did point me to this one, which shows the increasing (more vertical) angle of the base of a very bright rainbow as the Sun lowers.

We get extremely bright rainbows in Colorado in the spring and summer, once afternoon rain showers clear out. They tend not to last very long, but still, next time I see one I’ll have to try getting a time lapse of it. That’ll be a fun project.

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April 25 2015 7:00 AM

A Crash Course in Transgender Sensitivity

On Thursday, April 23, 2015, the 14th episode of Crash Course Astronomy went live. It’s about our sister planet Venus, and I spent quite a bit of time talking about just how infernally inhospitable it is.

Just as I have with every other episode, I had a lot of fun writing and recording it. A little background: Once we finish getting the footage of me talking, it’s edited and sent around to the team for comments. I then scour the ‘net looking for good images we can use, usually from NASA, ESA, and other public organizations (they have excellent high-resolution images which are free to use). Those images (and sometimes video) are placed in the rough cut, and then it goes off to Thought Café, who does our animations.


Eventually it goes live on YouTube, posted around 3:00 p.m. Mountain Time every Thursday. We promote it, and keep an eye on the YouTube comments for anything useful (did we make a factual error, is the audio good, and so on).

For the Venus episode on April 23 I was in Utah giving a talk at Clark Planetarium. When I got back that evening I checked to make sure the video was up, linked to it for a blog post first thing Friday morning, and then went to bed.

I was out of contact for much of Friday, traveling home. When I landed, though, there was a text from my editor that there was a problem.

If you’ve watched Crash Course Astronomy, you know I like to make jokes, and sometimes I’m the butt of them. The team goes along with it, and it’s usually great. This time, though, we made a mistake without even knowing it.

In one part of the episode, I’m talking about how Venus is really pretty when you look at it from Earth, but up close, it’s an awful place. As I spoke about Venus being pretty, we put up a cute animation of Botticelli’s famous “Birth of Venus”. But then, when I say Venus up close is awful (and say, "Yikes!"), we zoom in on the drawing and it turns out Venus has my face on it.

I thought this was pretty funny, a bit of humor poking fun at me. So we okayed it.

Well, it turns out that wasn’t so OK and funny with a lot of viewers. We got some comments that the joke was transphobic, making fun of transgender people.

That’s why my editor had texted me. I called her, and she told me what had happened. As soon as she told me, I had a forehead-slapping moment. Of course this could be seen as transphobic. In retrospect it was obvious. The good news is that the team felt the same way, and had already re-edited the video to remove that part, and had re-uploaded it before I had even called.

Let me be clear: I apologize for myself and on behalf of the team to anyone offended by the joke. None of us would knowingly make a joke at the expense of a group of people, especially one already marginalized and so often mocked in society. That wasn’t at all the intent, and it didn't occur to us it could be seen that way when we put it together. I hope you forgive us, and we’ll try to do better in the future.

Unfortunately, there’s more. In the comments to the (re-uploaded) video, some people are complaining that we are under the thumb of the PC crowd, and the phrase “social justice warrior” is used derisively. Let me address those commenters now:

You’re wrong. First, it’s not up to you to decide what offends or does not offend a group of people you are not a part of. You may feel that this was not an offensive joke, and you are welcome to that opinion; certainly the joke wasn’t intended that way.

But what you don’t get to decide is what offends others, especially in a group you’re not a part of. You may think that offense is undeserved, or that they are overreacting. You have the right to think that, but you cannot dictate it to those others.

Even if there was no harm meant in the joke, people may still take offense at it, and that’s their right. In this case, I can easily see where transgender folks would be put off by it, even angered.

And here’s the important bit: Apologizing and changing it does no harm, and in fact does some good; it helps a group of people see that we can be sensitive to their needs.

There are times when I think people are too sensitive, and times I think others aren’t sensitive enough. I tend to judge these on a case by case basis. But with a group that is historically marginalized and “othered”, well, a little (extra) empathy does a soul good.

And for the other bit, people derisively calling us “social justice warriors”? They may use it as a derogatory term, thinking of SJWs as shrill and overbearing, but to me it’s a term that refers to people willing to go to bat for others who don’t have as big a soapbox. I might prefer the term “ally”, but SJW fits fine, too. This world could use a lot more social justice. I’ll be happy to fight for it when I can.

So to them I say: “Thanks!”

April 24 2015 7:30 AM

Crash Course Astronomy: Venus

There but for the grace of physics goes us: Venus, second rock from the Sun, could be said to be Earth’s twin … but it’s the evil one.

Find out why on this week’s episode of Crash Course Astronomy!


I love the fact that you can learn all about Venus in this week’s episode, and then go outside after sunset and see it for yourself, shining brilliantly in the west. It’ll be close and bright for the next few months, actually, so you’ll have plenty of chances to see it. And in July it’ll start to show its crescent phase even in binoculars. That’s really something, and I hope y’all go out and take a look.

April 23 2015 7:00 AM

Slamming the Door Shut: Vaccines and Autism

Let’s start this off by being very clear: Vaccines don’t cause autism.

They just don’t. Perhaps I should be scientific, careful, technical, and say that no connection between vaccines and autism has ever been found. That’s technically true, because, after all, there is some incredibly small chance that eventually perhaps some connection might possibly be found. But when study after study after study shows no such connection whatsoever, at some point it’s probably OK to close the door on this.


Now it’s time to slam it shut. A new study, reported in the prestigious Journal of the American Medical Association, looked at a group of more than 95,000 children and found no connection between the Measles-Mumps-Rubella vaccine and incidence of autism.

Specifically, it looked at children who had older siblings, looking at the rate of diagnoses of autism spectrum disorder and vaccination. The study is pretty interesting, and I suggest you read it, but the results are pretty clear, as the researchers themselves write: “MMR vaccine receipt was not associated with an increased risk of ASD at any age.”

Emphasis mine, but c’mon. That’s emphatic.

Mind you, younger siblings who have an older sibling diagnosed with ASD are themselves at a higher risk for it (likely due to genetic factors). Despite this, the researchers conclude:

These findings indicate no harmful association between MMR vaccine receipt and ASD even among children already at higher risk for ASD.

In other words, the MMR vaccine is not associated with autism.

Mind you, the entire modern anti-vax movement is based on the idea that the MMR vaccine somehow causes autism; that was the conclusion drawn by Andrew Wakefield in a paper published in the British journal the Lancet … a paper that was retracted, that had several of Wakefield’s team members asking to have their names removed from it, that established a clear conflict of interest for Wakefield who stood to make hundreds of millions of dollars replacing an MMR vaccine with his own alternative, and that prompted the BMJ to call Wakefield’s methods “fraudulent.”

Yeah, that paper.

This new study is getting some press, which is nice, but I’m seeing here and there some folks hoping this will be the last nail in the anti-vax movement. It won’t be. That’s because the anti-vaxxers are not basing their decisions on science, they’re basing them on emotion. We’ve seen this over and again; as I pointed out before, this isn’t the first study showing no link between vaccines and autism.

People simply don’t make decisions based on facts. That’s not how we’re wired. Fear is an incredibly strong motivator, and many of the anti-vax groups use it to their advantage. Look at the truly atrocious Australian Vaccination Skeptic Network, who actually and truly compare vaccination to sexual assault (and seriously, survivors of such assaults may want to have a care clicking that link; the AVSN graphic is abhorrent and brutal).

And look no further than someone like Robert F. Kennedy Jr., who believes that vaccines cause autism, and compared this to the Holocaust. Yes, the Holocaust. He backed off that analogy when called out on it, yet few seem to remember this isn’t the first time he’s made this despicable claim. I’ve written about Kennedy before, taking him to task on his unfounded claims, and wrote a follow-up after he doubled down on it.

So yeah. The folks who beat the drums about vaccines and autism will never stop. My hope is that they will eventually be marginalized, like Moon Hoax believers.

The good news is that action is being taken. California is looking at stricter rules for parents who want to opt out of vaccinating their children, for example, and in Australia, the religious exemption is being removed.

And of course the forces of good are still at work, promoting vaccination. The Bill and Melinda Gates Foundation has put out a lovely campaign using art to show how important vaccines are. Called The Art of Saving a Life, it features works of film, literature, music, photography, and more.

As someone who loves classical music, especially Debussy, one video in particular struck me. Called Afternoon of a Faun, it’s a powerful piece about Tanaquil LeClercq, principal dancer at the New York City ballet. Before a European tour in 1956, she declined getting a polio vaccine. She contracted polio in Copenhagen and became paralyzed. She never danced again. Chinese pianist Lang Lang performs the pas de deux from Debussy’s Afternoon of a Faun, with images of LeClercq in the background.

I would like to personally thank Mr. and Mrs. Gates for supporting this project. It is extraordinarily difficult to discuss this topic with people who lean toward being against vaccinations, and it’s all too easy to reinforce their beliefs. I think that by continually putting forth a positive message, together with presenting the facts, we can get vaccination rates in this country up to where they need to be to protect us all.

As a father myself, and with an immunocompromised family member, I know how important this is. When you get vaccinated, the life you save may be your own, and it may also be someone you know and love. But it may very well be someone you don’t know, but who is loved by others.

To those of you who vaccinate: I thank you too.

April 22 2015 7:00 AM

25 Years of Cosmic Treasures: Hubble’s 12½ Greatest Hits

On April 25, 1990, the world—the Universe—changed.

That was the day the crew of STS-31 deployed the Hubble Space Telescope into orbit. This magnificent observatory has a special place in my heart. When it launched I was in graduate school in astronomy, and had just received my master’s degree. I was looking for Ph.D. research, and my adviser mentioned he was on a project to use Hubble to observe exploding stars … and now, 25 years later this week, Hubble is still going strong, doing astronomy.

And in my way, I am too.

I worked on Hubble one way or another for a decade, including being on a team that built one of the cameras that was installed on Hubble in 1997. I’ve written so much about Hubble over the past 2½ decades I don’t think there’s much more I can say about it. At the bottom of this post there are links to some of my favorite articles.

But I can still show you pictures. 

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.

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.

Dutch “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.

Correction, April 22, 2015, at 3:15 UTC: I originally misstated that Emil is Danish. He's Dutch.

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.