An Accidental Eclipse from 700 Million Kilometers Away
Astronomers keeping an eye on Jupiter’s moon Io got a surprise on Dec. 16 when it looked like something had taken a bite out of it:
What they saw was another of Jupiter’s moons, Europa, passing directly in front of Io, what astronomers call a transit (or more generically a “mutual event”).
Jupiter’s moons orbit the giant planet directly above its equator, and a few times a year everything lines up just right so that, from Earth, we see the orbits edge-on. When that happens the moons can pass in front of each other, creating a transit (or an eclipse if the more distant moon is completely (or nearly completely) covered).
I had to laugh when I saw the animation. My first thought was, why didn’t the astronomers know this would happen? The log records (in the link above) show they really were surprised. So I looked up how often these transits happen, and it turns out to be a little complicated. First, they happen clustered in time when Earth passes through Jupiter’s equatorial plane. Then you might only see a half dozen or so from a given location per month (some happen during the day, or behind Jupiter, when you can’t see them). That’s not very many, and even then they only last for a few minutes at a time.
So really, from a given observatory, it’s pretty unlikely at any given time to accidentally observe a transit. However, in this case, astronomers are engaging in a long-term campaign to observe Io, because the tides from Jupiter cause it to be the most volcanically active object in the solar system. Its volcanoes are constantly erupting, and when they do they’re visible in the infrared. The Gemini telescope, which made these observations, is designed to look at these wavelengths, and in fact you can see an active volcano on the upper left part of Io’s face. Since things on Io change all the time, lots of observations are made, and so it’s inevitable a visible transit would happen eventually.
Europa’s surface is water ice, which is pretty good at absorbing the particular color of infrared observed, so it looks dark. After the transit, the astronomers switched filters so that Europa can be dimly seen moving off to the upper right.
Sometimes there can be serendipitous science from such things; for example, the exact timing can be used to test equations predicting locations of volcanoes on Io and the positions of the moons themselves.
But one thing that I’m pretty sure will come of all this: In the future, I bet the astronomers making these observations will check for mutual events before the observations start!
A Tiny, Faint, Ancient Neighbor
One of the problems with astronomy is best portrayed by an old joke: At night, a cop notices a kid under a street light, looking intently all around him. The cop walks over and asks, “What are you doing, son?” The kid responds, “I lost a dollar, and I’m looking for it.”
The cop looks around for a moment, then asks, “Well, where did you lose it?”
The kid points over to a dark spot across the street. “Over there.”
“Well then, why are you looking over here?” the cop responds, reasonably.
The kid shrugs his shoulders. “The light’s better here.”
Such is astronomy. It’s easy to find the bright stuff, but the fainter objects are tougher, and we sometimes forget about them.
But they’re important. And that’s why the discovery of KKs 3 is so interesting: It’s a dinky spheroidal dwarf galaxy, thought to be the basic building blocks of much beefier galaxies like our Milky Way. Fewer than two dozen are known, so every new one is a gift.
KKS 3 is located about seven million light years away, which is pretty close by—just across the street, so to speak. But it’s fairly isolated, too. The Milky Way is part of a small clump of galaxies called the Local Group, and along with the Andromeda spiral galaxy we’re the two biggest. Most are small dwarf galaxies, and we’re all clustered into a volume of space roughly seven million light years across.
That puts KKs 3 well outside our group. There are other nearby groups, but KKs 3 isn’t a part of them either. It appears to be truly isolated.
It’s small, too: It has a total mass of about 20 million times that of the Sun. The Milky Way’s mass is 10,000 times larger! That makes KKs 3 incredibly faint. It’s amazing it was found at all. It was discovered in 2000, but not conclusively shown to be isolated until this new study using the Hubble Space Telescope. The image at the top of this post shows the galaxy. You can see it as a faint, spread-out smear in this negative image. By coincidence it happens to lie in the sky right next to a globular cluster, a smaller ball of stars presumably orbiting the Milky Way. Not only that but a pair of red stars in our galaxy happens to lie right in the middle of KKs 3.
This shows how hard it is to find these suckers. They don’t exactly stand out. Even faint nearby stars can confuse the surveys.
KKs 3 is also old. The majority of stars in it formed about 12-14 billion years ago in one big episode of star birth; that wasn’t long after the Universe itself formed. It had a couple of other, smaller bursts of star formation long ago, but ran out of gas (literally) after the last one, and no new stars have been created.
But this is all great news for astronomers: KKs 3 is a relic, so isolated and old it probably hasn’t changed much in a long, long time. Studying it is like having a time machine to study the ancient Universe. And we think that, billions of years ago, collisions between small galaxies like KKs 3 are what built up much larger galaxies. We know that the Milky Way is currently eating a few other small galaxies, so we can study those events and compare them to what we see in KKs 3 to learn more about how this process may have occurred so far in the past.
I know that photo of KKs 3 doesn’t look like much; splashier galaxies are so much easier and fun to look at. But this doesn’t make it any less important. You can search where the light is bright all you want, but if what you’re looking for isn’t there, well, what are you going to find?
The Orbital Perspective
I do love time-lapse animations of the Earth seen from the International Space Station, and if you do too, this is your lucky week: No fewer than three astonishing videos have been released in the past few days, and all three are absolutely worth your time to watch.
Make sure to set them to hi-def first! You don't want to miss the details...
The first is short, and shows the view from the ISS looking down on Europe and Africa as it passes southeast down the Italy coast, across the Mediterranean, then across Egypt. I think you’ll find Italy and the Nile fairly obvious!
I like how you can see storms peppering the Egyptian and Israeli landscape. Bonus: The scene is lit by moonlight! You can even see the Moon reflected in the sea in the early seconds of the video. Incidentally, the green arc over the edge of the Earth is called airglow—at night, molecules in the Earth's upper atmosphere slowly release the energy they gained from the Sun during the day.
Next is a much longer but even more wonderful video, featuring photographs of Earth taken by astronaut Alexander Gerst.
I love the sequence of the Dragon capsule being manipulated by the CANADARM 2 at 1:30. At 3:00 city lights like stars in space stream below, and then it cuts to the Milky Way above, like a poetic mirror of the cities. You can see parts of the space station lit, but again it’s the Moon not the Sun doing the illuminating.
At 3:36 a the solar panels turn to catch the Sun, watch the sky carefully: A distant satellite can be seen flying across the sky from the lower right to upper left.
One more thing to note: At 4:50 there’s a sequence showing the robotic arm moving the Cygnus resupply ship Janice Voss into position, which then flies away, destined to burn up in Earth’s atmosphere. It appears to move up, away from the Earth, which may strike you as odd since it’s supposed to head down! That’s a consequence of how orbital mechanics work; the ship had to boost to a higher orbit for safety, then do another rocket burn to dip the lower part of its orbit into the Earth’s atmosphere. I was so fascinated by this when that sequence was first released that I wrote an entire post explaining it. Rocket science is cool!
The final video is about astronaut Don Pettit, who was one of the first to start taking dedicated high resolution photographs from the Space Shuttle and ISS missions. He worked very hard to figure out how best to take these photos, and in this video he talks about his work.
You can see more of his images turned into an animation created by Christoph Malin.
At first you might think these animations are just eye candy, but I think they’re much more than that. They show our planet from a perspective the vast majority of us will never see for ourselves. Simply seeing it from above shifts our preconceived notions of it, erases national borders, and shows global phenomena that tie our ideas of a divided Earth together.
There is science to be learned from all this, certainly, and it’s an honor to have the chance to point it out. But I strongly feel that the long-term effects of images and videos like this on our philosophy, our outlook, will have a more profound impact.
Happy holidays, nerds!
And yes, that's our actual tree topper. Proof:
May all your days be filled with geekery.
No, a Planetary Alignment on Jan. 4, 2015, Won’t Decrease Gravity
The very first nonsense I had to debunk in 2014 was a claim that on Jan. 4 of that year a planetary alignment would cause gravity to decrease, allowing you to float momentarily or fall more slowly if you jumped in the air at the right moment: “Zero G Day.” This exact same hoax has resurfaced this week in a couple of places, so I’ve decided to update the debunking to include some new links and repost it, hopefully to stem the tide of silliness at year’s end. It seems fitting that (hopefully) this is also the last debunking I’ll make in 2014. But who knows? There’s still a week left.
Something you’ll never hear me say: “Well, now I’ve heard it all.”
Long experience has taught me there is always a sillier claim. Always. And you’re hearing that from a guy who has debunked the ideas that the Maya calendar predicted the end of the world, that the “Supermoon” caused earthquakes, and that a magnetic pole flip of the Earth will cause superstorms (and another saying the Earth is already physically starting to flip over).
So what’s sillier than these? Well, we now have the claim that early next year—on Jan. 4, 2015 at 09:47 PST to be exact—due to the combined gravity of Jupiter and Pluto, you will be able to jump in the air and float for just a couple of seconds (or at least fall more slowly, depending on different “sources”).
It’s hard for me to overstate just how wrong this claim is. First off, this exact same hoax was pulled last year, in 2014, by a site called News Hound (now offline, apparently), and a lot of people fell for it. Here we are again, a year later, back at the same spot. This time the joke is being made by a “news” site called Daily Buzz Live (which didn’t even bother to change much of the wording of the original hoax). They even have a picture of a NASA tweet about the event:
There’s only one problem: That picture is completely fake. NASA never tweeted it, and it was presumably made up wholesale for the article on Daily Buzz Live. Whoever did it was clever, adding the number of retweets and favorites, but it’s as fake as a $20 iPhone you can buy on the street in New York City.
After all, the physics of “Zero G Day” is wrong, the claim about Pluto and Jupiter is wrong, and—and this part is the real killer—it’s based on a joke made by an astronomer nearly 40 years ago!
Despite this, it’s spreading around Facebook (and Twitter) so much once again that I got a lot of people asking or telling me about it. That’s why I’m debunking this thing again.
So to get started, here’s the claim:
It has been revealed by the British astronomer Patrick Moore that, on the morning of January 4th 2014, an extraordinary astronomical event will occur. At exactly 9:47 am, the planet Pluto will pass directly behind Jupiter, in relation to the Earth. This rare alignment will mean that the combined gravitational force of the two planets would exert a stronger tidal pull, temporarily counteracting the Earth’s own gravity and making people weigh less. Moore calls this the Jovian-Plutonian Gravitational Effect.
Yeah, except this is all baloney. To be polite. OK, so why is this wrong?
Pluto and Jupiter, Sitting in a Tree …
First of all, the gravitational forces of the other planets in the solar system have essentially zero effect on you personally.
And we’re done. Full stop.
OK, fine, I’ll give some brief details. The planets are big objects with lots of gravity, but that only affects you if you’re close to them. Space, however, is big—that’s why we call it space—and planets are far away. This weakens their gravity on you hugely, reducing it to less than the impact of the flutter of a butterfly’s wing.
If you want the math, then here you go: Even if you add all of the planets together, they pull on you with a force less than 2 percent of that of the Moon! The Daily Buzz Live article mentions tides, too, but that’s even worse: The combined tidal force from the planets is far less, like 0.005 percent of the Moon’s! Simply put, the planets are just too far away to have any real effect on you. By the way, the Moon orbits the Earth on an ellipse, so its own gravity fluctuates far more than the combined strength of the planets every two weeks.
Note that you cannot float in the air every two weeks.
And specifically, the gravity from Pluto is weakest of them all. Pluto is a teeny tiny ice ball, far smaller than even our Moon … and at its closest it’s flippin’ 4 billion kilometers (2.5 billion miles) from Earth. That’s a long way. A car on the road half a kilometer away has more gravitational pull on you than Pluto does.
In fact, doing the math, I find that the Earth pulls on you about 200 trillion times harder than Pluto does. That's about the same ratio as the number of cells in your body to a single cell ... so this claim that you can float is like saying you can shed a single cell and fly away by flapping your arms.
It gets worse (amazingly). The article says Pluto will be “directly behind Jupiter” on Jan. 4, 2015. I checked: On that day they are on nearly opposite sides of the sky. They’re really far apart, about 145°. You couldn’t have picked a much worse date to claim Pluto was behind Jupiter.
So the physics of the claim is ridiculous. But the origin of the claims makes it even funnier.
Fool Me Once, Shame on You
The article on Daily Buzz Live mentions that this claim came from Patrick Moore. He was a real astronomer in the U.K., an enormously popular radio and television science program presenter—he predated Carl Sagan and is still considered an icon of science in England.
The wonderful thing about all this is: Moore actually did make this claim! However, as Snopes.com points out, it was an April Fools' Day joke. Moore made this claim in 1976 on his radio program. To my complete unsurprise, apparently some folks called in to say they did feel the effect! This is called “priming,” where you tell people in advance that they’ll feel something due to some cause, and they will, even if the cause never happened. It’s used by ghost hunters and ghost tour guides quite a bit, to spook people before they actually enter a “haunted house,” guaranteeing they’ll feel chills as they walk from room to room. I’ve seen this myself first hand: People can convince themselves of amazing things that never actually happened.
So there you go: It’s a repeat of a silly claim based on a joke in the first place.
I know a lot of people reading this right now are slapping their foreheads and wondering how people can be so stupid as to fall for this. I understand this reaction, but I don’t share it. Smart people fall for silly things all the time, and intelligence isn’t really the prime factor here.
Skepticism is. In general, schools don’t teach people how to analyze a claim, how to tell if something makes sense on the surface of it, or how to go about looking into the claim. I knew right away to do the math, and to see if Pluto and Jupiter really were aligned as the article says. But all too often, people don’t think carefully (or at all) about these claims, and simply spread them through social media. All it takes is literally the click of a “Share” button. Pseudoscience thrives via this virulence, whereas truth must take a harder path.
In fact, that’s why I bother debunking stuff like this. Sure, this is a silly claim, and probably harmless in practice. But not all of them are; I already mentioned the “Mayan Notpocalypse” from 2012, and I can tick off a dozen other doomsday or scary claims that spread due to a lack of skepticism. And of course there are real issues like global warming denial, anti-vaccination, and more, which live and breathe and spread due to a lack of skepticism in the public.
In my original post about this in January 2014, I said, “This particular bit of fluff will dry up and float away in a day or two, but those others are here to stay for a long time.” I was wrong, and I should’ve known that something like this would resurface again in a year; it’s like the “Mars as big as the Moon” nonsense that comes back year after year.
Still, my hope is that every time we take a moment to inject a bit of (polite) skepticism into people’s everyday lives, it makes the world a slightly better place to be.
If enough of us do it often enough, we can change “slightly” to “magnificently.”
Follow-Up: Celebrities, Science, and Anti-Science
Late last week, I posted an article about Mayim Bialik and the issues of celebrities promoting science—specifically, including her in a picture of four other actresses who hold degrees or have published in scientific fields. In general, I like it when actors/writers/famous people take a shine to science. They’re in the public eye, and if they promote science, then that’s a Good Thing.
But this can come at a cost, when the promoter in question may hold some anti-scientific beliefs. When they promote those as well, what to do? As I wrote at the time, what I try to do is applaud them when they’re right and point it out when they’re wrong.
For the specific case of Bialik, this gets more complicated. She holds a degree in neuroscience, and is an enthusiastic supporter of getting more girls into science, technology, and math. That’s great!
But she also supports a lot of what I would call anti-science. Her statements have made it clear she holds some anti-vaccination beliefs and promotes homeopathy, two stances I am very, very strongly against.
In the end, I felt the good outweighed the bad, though, and said so.
A lot of people agreed, a lot disagreed. Keith Kloor, for example, wrote an interesting piece on his Discover magazine blog Collide-a-Scape, pretty much agreeing with my premise (though he doesn’t really talk specifically about Bialik; he applies it to Dr. Oz).
My good friend Steve Novella wrote a typically thoughtful and smart piece as well. He also agreed with my premise in general—we need to take these promotions of science on a case-by-case basis—but disagreed with my stance about Bialik. He thinks her anti-science stance tips the balance, and we shouldn’t hold her up as a role model:
In the specific case of Mayim Bialik I have to disagree with Phil. I think the bad outweighs the good. Just the mere fact of an actor who is a neuroscientist is not that big a deal. Her views on vaccines and medicine in general, however, are extremely pernicious. In fact, her credentials as a scientist are a negative in this case because they mostly serve to lend weight to her antivaccine views. I would not promote her in any way, and I certainly would not do anything that could possibly lend the imprimatur of legitimacy to her views.
I’ll admit I hadn’t considered that her credentials could be used by anti-vaxxers and the like to promote their incorrect (and dangerous) beliefs, and that gave me pause. Thinking that through, I have to say that does sway me; if she were promoting something like astrology, I’d probably just roll my eyes a bit and carry on. But these medical health issues are serious, and I’ve been very vocal for a very long time about vaccines and homeopathy.
Because of that, I’ll be clear: I’ve changed my mind; given the opportunity again, I’d say using her as a science role model is not a net benefit. I’d have left her off the picture.
Mind you, I’m talking about this one case where someone promoting science and/or rationality may have beliefs or opinions that bump up against the evidence*. There are many others, and both Steve and Kloor bring them up (including Bill Maher, Bill Nye, Richard Dawkins, and more). I’m not surprised. The main thrust of my article is that we all have things we believe that may not hold up to scrutiny.
There’s a line attributed to Penn Jillette: “Everybody’s got a gris-gris.” Putting people up on a pedestal without reflection is a bad idea; feet of clay tend to crumble. Where we draw the line is an interesting and fruitful topic of discussion, and I imagine for many it will be a subjective judgment call.
I will, however, disagree with Steve on one thing. I do think that an actor with an advanced science degree is remarkable, and it is reason to praise them (all other things being equal). Like it or not, a lot of people listen to celebrities (the word is a cognate of “celebrate”, after all), so when some of them are clearly pro-science, I’m happy to support them.
On a case-by-case basis, of course.
Correction (Dec. 23, 2014): Keith Kloor's blog is on Discover magazine's blog, not Discovery as originally written.
* Update (Dec. 23, 2014 at 17:30 UTC): I rephrased this sentence to make it clear I was not talking specifically about the same issues as with Bialik; i.e. anti-vax and homeopathy.
Twinkle Twinkle Little Star, an Astrophysically Correct Book and Song Are Now What You Are
This is so fun: my friends Zach Weinersmith of SMBC and Henry Reich from Minute Physics have written an astronomically corrected version of the song “Twinkle Twinkle Little Star” for kids!
They also put together a totally adorable short video with Henry singing the song:
When I first saw it I thought I saw a mistake in it, but I was wrong. I point it out so others don’t misunderstand it the way I did. The lyric is about a pulsar: “Out away from Earth your drift, this is known from your redshift.” I mistook this line to say we know its distance from its redshift, but that only works for very distant galaxies, not pulsars, which are inside our own galaxy. But I misunderstood; they’re saying we know it’s moving away from Earth by its redshift, and that’s technically correct. So there.
Anyway, this has come out just in time for the holidays. Go buy it, and turn more kids into little science pedants!
So a Galaxy Walks Into a Bar ...
Adam Block is one of my favorite astrophotographers. Now, he has a bit of an unfair advantage: the 0.81-meter Schulman Telescope at the top of a mountain in Arizona at his disposal. He’s also really good at finding interesting but lesser-known objects and has a serious knack for creating incredible images of them.
I’ve featured his images many, many times on this blog, but I think this may be the very best I’ve ever seen: the spiral galaxy NGC 1398.
Today the Sun Stands Still
Today is the real reason for the season: It’s the winter solstice! If you’re a purist, then raise your glass at 23:03 UTC (18:03 Eastern U.S. time), because that's the moment the solstice occurs.
There are a lot of ways to look at this, but they all boil down to the Earth’s axis being tilted with respect to its orbit. You’ve seen this with classroom globes; they’re tipped by about 23.5°. As it orbits the Sun, the North Pole of the Earth’s axis is always pointed pretty close to Polaris in the sky, which means that sometimes the axis is tipped toward the Sun, sometimes away. When it’s tipped as far from the Sun as it can be, that’s the moment of the winter solstice.
Illustration by Tfr000 on Wikipedia, Creative Commons License. In this animation, the winter solstice occurs when the Earth is to the far left part of its orbit, and the northern axis points away from the Sun.
Of course, when the northern pole is tipped away the Sun, the southern pole is tipped toward it, so it’s summer down there. In that sense, it’s better to call today the “December solstice” rather than “winter solstice.” Nearly 900 million people live south of the equator, so it’s probably a good idea to keep them in mind when we name things.
But for us in the north, today is the day the Sun stands still (the literal meaning of “solstice”). What does that mean? If you go outside every day at local midday (literally, halfway between sunrise and sunset) and note the position of the Sun in the sky, it changes during the year. It’s lower in the winter and higher in the summer.
Today is the day it gets as low as it can at midday—that’s why it “stands still”; it’s dipped as low as it can go and has stopped its decline. It’s the shortest day and longest night of the year. If you go out tomorrow it will be a wee bit higher at midday, and the day will be a tad longer.
The change is slow at first, then speeds up, accelerating the most at the vernal equinox in March. On that day, the days are lengthening as quickly as they can, usually by a couple of minutes or so per day. Then, at the June solstice, the Sun is as high in the sky as it can get, days are at their maximum length, and the Sun stands still once again. It reverses course, and starts getting lower every day at midday until late December.
Lather, rinse, repeat. Unless you're in the Southern Hemisphere, where this is all upside-down, so for you austral folks: repeat, rinse, lather.
And this is why we have seasons: In the summer the Sun gets higher in the sky, heating us more efficiently, and the day is longer, so there's more time to warm up. In the winter it's lower, and the days are shorter, so it gets cold.
Some people call today the first day of winter, but I prefer to think of it as midwinter’s day. After all, today the Sun starts getting higher in the sky, so why say that’s the first day of winter? Weather is regional, anyway, so trying to tag a definition of when winter starts is pretty silly.
Instead, use today to think about astronomy, cycles, the motion of the Earth, the patterns of the sky, and the amazing nature of our Universe.
Or, honestly, why not every day?
Detecting an Exoplanet … Without a Telescope
Years ago, when the first transiting exoplanet (HD 209458b) was found, I was startled to realize that it could be easily detected using a small, inexpensive telescope.
Transiting exoplanets are planets that orbit other stars, and from Earth we just so happen to see their orbit edge-on. That means the planet passes in front of its parent star (that’s the transit bit), blocking a fraction of its light. A tiny fraction, usually far less than 1 percent. But if the star is bright, this dip in brightness can be spotted in small telescopes. I remember doing the calculations and finding that a 30 cm telescope could detect HD 209458b in a single night’s observations. Tough, but possible.
That meant an amateur astronomer could detect exoplanets! What didn’t occur to me at the time is that you don’t necessarily need a telescope to do so.
David Schneider, an editor at IEEE Spectrum, has described a setup using a digital camera and 300mm telephoto lens that has allowed him to detect the transit of the exoplanet HD 189733b, a so-called hot Jupiter, a massive planet orbiting very close to its star. The transit depth is about 2.6 percent, and his data look pretty good to me. He based his work on an amateur astronomer (vmsguy on the Cloudy Nights forum) who has also posted data that look pretty convincing.
Basically, the idea is to take several exposures over the course of the transit, taking care to make sure you get pictures taken before and after the transit. That’s your baseline. Using software to align the images and examine the stars (both vmsguy and Schneider used IRIS, which is Windows only, but other packages exist), you measure the brightness of the star over time to see the transit.
Not that it’s that easy! In reality you do relative photometry: You measure the brightness of many stars at the same time, so that a passing cloud doesn’t dim your star and make you think you’ve found an exoplanet. You also have to take other calibrations (like darks and flats), and apply them carefully. But it’s not impossible, and in fact sounds like fun.
Mind you, Schneider went all-in, even to the point of building his own gear to track the stars, but if you have a telescope you can always just use the motor drive that does that for you. The point is, you can detect exoplanets using just a camera, a good long lens, and a solid mount!
That’s amazing. I’ve been thinking of trying this sometime using my own 20 cm ‘scope; a lot of exoplanets are within range. But I’m still figuring out how to take astrophotographs, and believe me, I know how addicting this can be. I used to do this for a living, and if I get the software and start observing, I’ll be down the rabbit hole pretty quickly!
But in some ways, that’s the point. If you have the time and resources, it’s pretty amazing what you can do. You can even observe alien worlds.
Tip o’ the lens cap to James Walker.