Bad Astronomy
The entire universe in blog form

Aug. 13 2015 7:30 AM

Life in the Asteroid Belt Is Rough

Being a large object in the solar system means getting brutalized over the years, pummeled by millions of impacts. Some objects wear it well; Earth, for example, has an active surface built up by volcanoes and eroded by continental subduction, rain, and wind. After a few million years impact craters usually get worn away.

Other objects are active in other ways; undersurface oceans like on Enceladus and Europa tend to erase scars as well.

But airless, static bodies tend to proudly display their scars. And when you live out in the asteroid belt between Jupiter and Mars, you get a lot of them.

A lot.

That picture above is not of the Moon; it’s Ceres, the largest asteroid. At 950 kilometers across, it’s the largest target in the entire belt, and not surprisingly covered in craters. This image was taken by the Dawn spacecraft on June 24, 2015, from a height of 4,400 kilometers above the surface. It shows the part of the asteroid just on the edge of sunlight, the day-night line astronomers call the terminator. The craters on the edge of this region see the Sun low in the sky, so shadows are long, and elevated features (relief) are more easily seen. My favorite part is the one crater rim near the top right just high enough to poke into sunlight; everything else around it is in the shadow of night.

JPL just put out a video tour of Ceres using imagery from Dawn, and it's pretty cool. Watch:

You can also have some fun poking around at an interactive rotating map of Ceres put together by Google engineer Ian Webster. 

There’s a lot about Ceres we don’t know, but Dawn’s journey is our journey to understanding. What are the bright white spots seen, some in craters and some not? Are the reports of hazy features—suggesting outgassing—real, and confirmable?

We may know soon. Dawn has already lowered itself into a tighter orbit, moving a week after the image above was taken to a height of 2,300 kilometers. In mid-December, it will lower itself again down to an altitude of just 375 km. The resolution in the images will increase by a factor of more than 10 over the picture above.

A lot of scientists are hoping that will be enough to get the detail they need to solve some of the nagging questions this gigantic ball of ice and rock has been posing. And they are legion.

If you want to keep up with the mission’s status, check out the Dawn Mission Status Updates, and read the well-written and quite enjoyable Dawn blog. And you can always peruse the phenomenal images taken by Dawn as well. This is a great mission, and it’s doing great work.

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Aug. 12 2015 7:30 AM

Now THAT’S a Supernova

The problem with supernova remnants is that so many of them just don’t look like explosions.

They’re round circles, or disks, or this, or that, (or Ben Grimm, or a blastocyte), but at a glance they don’t convey the awesome magnitude of a supernova, the most catastrophic event the Universe can provide. At the end of its life, a massive star explodes, literally tearing itself to shreds, blasting octillions of tons of matter outwards at a healthy fraction of the speed of light. At peak brightness, they can outshine the Sun by a factor of a billion.

So yeah. They should look like explosions.

One of the very few that does is the Vela supernova remnant, the debris from a star that blew its lid roughly 11,000 years ago. It’s not exactly clear how far way it is, but it’s something like 800 light-years distant. It’s huge, covering a full 8° of sky, more than 15 times wider than the full Moon.

And it looks like this:

Aug. 11 2015 7:00 AM

No, There Won’t Be Two Moons in the Sky on Aug. 27. Or Ever. Ever Ever Ever. Ever.

Oh for Ares’ sake. This again?

Yup, it’s August, and that means it’s time for the annual “two Moons in the sky” Facebook hoax. Maybe you’ve seen it; it starts to go viral around this time of the year. It’s also sometimes sent around with a note saying, “Mars will be as big as the Moon.”

Let’s get this out of the way immediately: No. It’s baloney. It isn’t true this year, it wasn’t true in 2013, or 2009, or 2008, or 2007, or 2006, or 2005, or even when it first began back in 2003.

It can never be true. Mars can simply never get close enough to Earth to be seen as more than a dot by the eye. Despite that, this hoax gets spread all the time—I’ve already been getting questions asking whether it’s true.

Here’s the actual claim going around this year:

viral hoax
I may have annotated it slightly. See if you can spot what I did.

Photo by some anonymous chucklehead on Facebook

The caption says,

12:30 Aug 27th you will see two moons in the sky, but only one will be the moon. The other will be Mars. It won’t happen again until 2287. No one alive today has ever witnessed this happening.

Well, at least one part is true: No one has ever seen this, because you can’t. Note too this is the exact same Photoshopped picture used in 2013. Blarg.

Here are the facts. Mars is on an orbit outside of Earth’s from the Sun. It’s at its closest when the Earth passes it on the inside. Both orbits are elliptical, so sometimes they get closer than other times, but really the closest they can be is roughly 55 million kilometers (35 million miles) apart. That’s more than 100 times farther than the Moon. Given that Mars is roughly twice the physical size of the Moon, that should set off alarm bells in your head right away. At best, Mars is still only 1/50th as big as the Moon in the sky! On Aug. 27 the Moon will appear 530 times larger than Mars.

Look at the photo at the top of this article. I actually took an image of Mars and scaled it to one of the Moon as they will both look on Aug. 27. Not so amazing, is it?

It’s even worse: Mars doesn’t get very close to Earth this year at all. The last perigee (closest approach to Earth) was in 2014, and the next one won’t be until next year in May. Also, on Aug. 27 they will literally be in opposite parts of the sky, 175° apart. When one rises, the other sets, so in realistic terms they won’t even be in the sky at the same time for more than half an hour.

No one really knows why this hoax got started back in 2003. I know how; I described it: A real note got spread around saying that through a telescope at 75X, Mars would look as big as the Moon does by eye. That part is correct, but it got changed by someone to the current “Mars as big as the Moon” silliness, and now I think some goofball or goofballs spread it around every year, knowing people will continue to spread it without checking.

It’s frustrating to debunk this every year. It’s not so much the act of doing it as having to do it; I wish people understood the sky well enough to know such an event is impossible. I don’t fault anyone for that, really; people are busy and have different interests and so on.

But in this country in particular and worldwide in general, critical thinking isn’t exactly encouraged. Generally not by schools, not by governments, and not by religions, essentially nowhere are children taught these basic skills in a rigorous way. It does happen, of course, but it’s not exactly widespread. If we did teach kids how to think, not just what to think, then maybe a lot of these hoaxes would go away.

And not just inane, innocuous pranks like this, but also serious problems with thinking, like denying the benefits of vaccines, denying the reality of global warming, or believing the Earth is 6,000 years old. These do in fact have serious repercussions.

So I will continue to debunk nonsense like the Moon/Mars thing when they pop up, because every time we chip away at our ability to think critically we lose a piece of our ability to deal with the world as it is, and we actively make it worse.

If we, as a species, knew better how to think, a lot of the very large problems we face today would never have occurred in the first place. That’s a world I’d very much like to live in.

Aug. 10 2015 7:00 AM

How to Watch This Week’s Perseid Meteor Shower

The annual Perseids meteor shower peaks this week, and it should be a pretty good show this year! There’s no Moon in the sky to wash them out, so if you can get to a dark site away from lights, you may see 60 or more shooting stars per hour.

I have details below on what to expect. But for the tl;dr crowd: The best time to go out is Wednesday night/Thursday morning after your local midnight. Find a place with wide-open skies, lie back, and look up. You don’t need a telescope or anything like that. The meteors should zip across the sky about once per minute or so on average, appearing to come from near the constellations of Cassiopeia and Perseus in the northeast.

Meteor showers occur when, as the Earth orbits the Sun, it plows through the debris left by a comet (or, in one case, a weird asteroid) that is also orbiting the Sun. Comets are basically dust and gravel held together by water ice, and as the Sun warms the comet the ice sublimates (turns directly to gas) and the rocky bits are sloughed off. They orbit the Sun in more or less the same path as the comet, and when the Earth rams through them they enter our atmosphere at high speed, heat up, and glow.

And we get a meteor shower.

The Perseids are from the debris shed by the comet Swift-Tuttle, which orbits the Sun once every 130 years. The Earth crosses this path in August. Due to perspective (the same effect that makes raindrops always seem to be coming from ahead of you when you drive a car through a rain shower) the meteors appear to come from a point in the sky in the constellation of Perseus, near the W-shape of Cassiopeia. They radiate away from there, so that point in the sky is called the radiant, and the shower gets its name from the constellation.

A bright meteor reflects on its fate.

Photo by Randy Halverson, used by permission

I’ve written guides to watching meteors showers before, and specifically for the Perseids in 2013 and 2007, and both are still valid for this year’s shower. Even so, I tend to get a lot of questions via email and social media about how to watch the shower. Below are some of the questions I usually see—the answers make a pretty good guide to experiencing the shower, so check ’em out.

By the way, I did a whole episode of Crash Course Astronomy on meteors. It’s not specific to the Perseids, but it’s chock full o’ fun science.

Now, on to the FAQ!

When is the best time to watch?

Technically, the meteor shower starts around July 17 and lasts until late August. Realistically, though, it peaks over the week centered around Aug. 12–13. This year, the best time to watch is Wednesday night after local midnight (that’s when your part of the Earth is facing into the oncoming meteoroids and you see more). However, Tuesday or Thursday night will be fine, too. The later you wait in the evening the better, but even a couple of hours after dark will be fine. Even better, the Moon is near the Sun this whole week, so it won’t blanket the night sky with light like it does some years. That means darker skies all night long. 

Incidentally, astronomer Jeremie Vaubaillon, who models the streams of debris that come off the comet, predicts there may be an enhanced number of meteors at 18:40 UTC on Wednesday, Aug. 12. That’s during the day for the U.S., so blarg. But if you’re in Asia that’s perfect! See if you can catch the bump in numbers (it’s not clear how many additional meteors there may be). If you do, take note: Those bits of comet were sloughed off by Swift-Tuttle back in 1862! They’ve been traveling around the Sun together for 150 years, and we’re just now meeting them.

The 2014 Quadrantids put on a fine show over the Great Wall of China.

Photo by Leo Lam, used by permission

How many will I see, and how often?

The Perseids average about 60–100 meteors per hour. I usually see a lot fewer than that because my skies aren’t particularly dark. Meteors are random, in that you may see three in a row in a few seconds, then nothing for five more minutes.

A lot of people have the misconception that you’ll see meteors zipping across the sky everywhere like fireworks. It’s not like that; expect to see one per minute or so. Trust me, it’s still wonderful!

Speaking of which, don’t expect to go outside and see tons of meteors right away. Your eyes take a few minutes to adjust to the darkness (it takes about a half hour to get fully adapted) so give it a few after going out. Patience!

What direction should I face?

Up! Seriously, meteors can appear anywhere in the sky (though they tend to head in a direction away from Perseus), so the more sky you can see the better. Try to get away from buildings and trees. I have a spot in my yard with fewer trees and where my house blocks the light from nearby towns. See if you can find something similar.

Do I need a dark sky?

Being away from city lights helps a lot. Many meteors are fainter and get washed out if the sky is bright from light pollution. However, I grew up in the Washington, D.C., suburbs and usually saw quite a few meteors, so incredibly dark skies aren’t critical. Just nice.

Do I need a telescope or binoculars? A camera?

I think this comes up due to movies and TV shows (and commercials in fact) where they show people out in a field looking through a telescope during a shower. But this is a terrible idea! Meteors zip across the sky from random spots, so you want to see as much sky as possible. A telescope only lets you see a tiny part of the sky at once. Bent over an eyepiece, you’re likely to miss everything. It’s like trying to watch fireworks through a soda straw.

Having said that, if you have binoculars or something else, why not use them every now and again just to see the sky? You’re outside, it’s dark, and the wonders of the heavens await! Just be aware you’re trading off seeing some meteors if you do, but scanning the Milky Way with binoculars for a few minutes is totally worth it.

As for taking pictures, getting good shots of meteors can be a bit tricky. I suggest reading the guides at the American Meteor Society, Sky and Telescope, and PetaPixel. What you get out of the effort depends on what you put in, usually. But even inexpensive digital cameras can do the trick.

Geminid and Orion
One of my favorite photos of a meteor: a Geminid against the background of Sirius and the lower half of Orion. Framing can really make a shot if the meteor cooperates!

Photo by Babak Tafreshi, used by permission

Meteors, meteoroids, meteorites? What?

Meteoroids are the solid bits of debris. Meteors are what we call them as they shine brightly, ramming through our air. Usually they burn up, but if they make it to the ground we call them meteorites. So a meteorite is a meteoroid that survives being a meteor.

How fast are the meteors traveling?

A typical Perseid is moving at about 60 kilometers/second (35 miles/sec) when it enters our atmosphere. That’s 200,000 kph (130,000 mph)! That’s incredibly fast; rapid enough to get from the Earth to the Moon in just two hours.

Geez, that’s fast! Are we in any danger from the meteors?

Nope. These are generally not much more substantial than snowflakes or grains of sand. They burn up 90–100 kilometers above the ground, far, far above your head.

Are astronauts in danger from meteors?

Not really. The odds of the space station getting hit are incredibly low, even over the course of many years. But in 2011 astronaut Ron Garan got a photo of a Perseid meteor burning up in the air below him. How cool is that?

Perseid from space
Did I say look up to see the meteors? If you're an astronaut on the ISS, ignore that advice.

Photo by NASA

Why do they leave a smoke trail?

That’s not really smoke; it’s vaporized meteoroid bits! As the meteoroid screams through the air, it gets hot because it’s violently compressing the air ahead of it—when you squeeze a gas it gets hot, and the meteoroid is squeezing the air hard. Bits of the particle melt and blow off (astronomers call this “ablation”) forming the long trail (technically, we call it a “train”) and can take a few seconds to cool and fade.

One meteor got really bright and I thought I saw a puff of smoke that lasted for a few minutes. What was that?

Pushing through our air at high speeds puts the meteoroid under incredible pressure. It can break apart, and the pieces burn up much more rapidly. This can cause a pulse or multiple pulses of light, basically explosions. The meteoroid can disintegrate, creating a big puff of ionized particles that sometimes last for several minutes (this is called a “persistent train”), which then gets twisted in high-altitude winds. It’s rare, but spectacular. I’ve never seen one.

persistent train
reddit user -545- got a great sequence showing a meteor leaving a persistent train. Click for more info.

Photo by reddit user -545-, used by permission

Why are some meteor trains long and some short?

The length of the train depends on the angle of the meteor toward you. If it’s headed right at you it will appear foreshortened, so it looks really short. If it’s headed tangentially from you, more or less across the sky, it’ll appear longer.

Its like someone throwing a ball right at you to catch versus watching two people play catch from the side. Perspective counts.

Can I listen to the shower?

This may seem like a weird question, but the answer is yes, kinda. They happen so high up that any sound they might make will never reach your ears, so in that sense, no.

But, meteors are so hot they ionize the air around them, stripping the electrons from the atoms and molecules. Ionized air makes an excellent reflector of radio waves, and so a meteor will make a radio “ping” as it zips through the sky. You can listen to this live at the Space Weather Radio site. It’s eerie.

I have more info about this in an earlier post.

Where can I get find out more about meteors?

I’m glad you asked. Here are a bunch of links that’ll keep you occupied until the show starts. Enjoy!

Aug. 9 2015 7:00 AM

Set Phasers to Buy

I don’t generally review products on the blog, for a lot of reasons. Mostly it’s because I don’t want to waste my time or yours with negative reviews of stuff that made me cranky somehow (like a sky mapping app I tried recently that refused to let me use my current location, instead insisting I was in Australia)—especially when I have a sneaky suspicion the problem is my fault, but I can’t trace it.

On the other hand, sometimes truly cool stuff comes along, and it’s a pleasure to write something about it. When that something comes from ThinkGeek, well, that’s even easier.

And if it’s a Star Trek prop? C’mon.

I am a bona fide Star Trek dork (I present Evidence A and Evidence B), but I don’t have a lot of swag to prove it. So when I saw the replica Hand Phaser prop at the ThinkGeek booth at San Diego Comic-Con, I knew I had to have it.

Two things. First, tl;dr: This prop is very well made, and the sounds it makes are great. It’s also a universal remote control, but a bit clunky for use that way (though fun). If you buy it, it’ll be because it’s just really cool, and not because you need a new remote. It’ll set you back $149.99.

Second, the good folks at ThinkGeek gave me this prop to review it. However, I cannot lie to you: I like TG’s stuff, and the phaser really is all that. If I didn’t like it, I’d say so.

I like it.

The phaser comes in a hard plastic shell protective carrying case, with molded foam interior for storing the parts. The case is labeled “U.S.S. Enterprise NCC-1701 Standard Issue Phaser,” in case you forgot what ship you’re pretending to be on.

You have to do a tiny bit of assembly, basically just attaching the handle (a screwdriver is included). For those of you who sadly are not Trekkies, the small weapon is called a Type I phaser, and that can snap into the larger handled Type II phaser pistol. In this prop, the Type I phaser has the rechargeable battery in it (a micro-USB cable is included, though any will work). The whole assembly comes with a metal display stand that grips it using rare-Earth magnets, which is pretty slick.

The phaser has a wide array of modes and sounds. The instructions were unusually lucid for such a thing; the closest I’ve ever come to desiring murder is reading instructions for assembling or using some device or another. In this case, the directions are quite clear, with only a slight bump due to unfamiliar parts (you’ll need to know the difference between the Mode Selector Button, the Phaser II dial, and so on, but the diagram included in the instructions is very helpful).

The phaser is lovingly crafted metal and plastic, with high attention to detail. It feels good in your hand, like a well-designed tool should. It’s not a lightweight piece of junk; it feels solid.

The phaser sounds are great; it makes nine different sounds replicated loudly and clearly. Trying to be a smug know-it-all jerk at Comic-Con, I asked the ThinkGeek rep who was showing it to me if it would do a “forced chamber explosion,” a setting in the show that overloads the energy source of the phaser, causing it to explode.

He smiled, turned the dial to 9, and hit the button. To my delight, the familiar whining sound started, building up. He then unscrewed a small plastic knob on the side of the phaser, and I could see the “dilithium crystal” going through a series of color changes, the sound building, until the weapon “exploded” (well, made a “kaboom” sound). Pretty much at that point I was shouting “shut up and take my money!

Here's a quick video I made showing you the features:

As a prop/toy/collectible, it’s seriously top notch. But wait! There’s more!

It’s also a universal remote control. Sort of.

The phaser can be programmed to control a TV set (or cable box). These are all done using hand gestures; you can pump the phaser forward, backward, right, left, up, down, or tilt it left and right for a total of eight gesture commands (plus just using the trigger, giving you nine options). There are four color-coded “memory banks” for storing gestures, so you can have up to 36 such remote control commands.

It took me a few minutes to understand how to program it, but once I got it the commands stored easily. The thing is, there’s no way to check which gesture (or which memory bank it’s in) does which remote command. Was the tilt left changing the channel, or was that trigger/pump forward? Without that sort of guide, the phaser’s use as a remote is limited, unless you have a very good memory (or want to have a written list mapping gestures to commands).

But seriously. I don’t think people will buy this phaser only because they need a remote. That’s just silly fun added to what’s already a pretty amazing prop. And I’ll admit: It’s fun to set it to turn on and off the TV by firing at it. That will prove amazingly satisfying when commercials come on.

It’s not cheap, but quality comes at a price. If you’re a die-hard Trek fan or you know one, and you’ve got the cash, then you want this.

Aug. 8 2015 8:55 AM

The Depths of the Lagoon

The Lagoon Nebula is a vast, 100-light-year-wide star factory. It’s a huge cloud of gas and dust, and inside of it stars are born out of that material. It’s very active, and has been for a long time; embedded in it is a cluster of more than 1,000 stars that are only a few million years old. They formed from the gas in and near the nebula.

Star forming nebulae are typically a mess, with massive stars blasting out radiation and fierce winds of subatomic particles. This slams into the material floating between the stars, lighting it up and sculpting it into fantastic and frankly weird shapes.

So when you point Hubble Space Telescope at the Lagoon, you see just what gorgeous chaos it is:

Aug. 7 2015 7:00 AM

Crash Course Astronomy: To Explore Strange, New Worlds

One of my favorite topics in astronomy is exoplanets: planets orbiting other stars.

Astronomers have been looking for them for decades, and there were lots of false alarms, but no true planets found … until 1992, when pulsar planets were found, and then just a few years later when planets orbiting stars like the Sun were first detected.

I remember the next few years, the arguments that raged over whether these planets were real or not, until an independent observation of one transiting its star clinched the deal. Now, just 23 years later, we have a roster of thousands of such exoplanets, so many that zoological-type classification is possible. The range of planet flavors is huge, showing us that stars make planets with relative ease.

How wonderful is that?

It’s why this week’s Crash Course Astronomy episode on exoplanets was so much fun to put together. Just thinking about this topic gets my brain fired up. Maybe I can share that feeling with you:

As you may recall, this episode was supposed to go up last week, and in fact did, but we quickly took it down after we discovered an error in one of the animations. We’d rather get things right, so we fixed it and here it is all shiny and fully functional.

As a planet orbits its star, the star moves, too.
A planet and star orbit their mutual barycenter.

llustration by NASA/Spaceplace

If you’re curious, the problem came about due to barycenters. When a massive object like a planet orbits another massive object like a star, it’s more correct to say they both orbit around their common center of mass, called the system barycenter. The animation you see here demonstrates it.

As you can see in the animation, the planet makes a big circle and the star makes a small one. And if you watch closely you’ll see they’re always on opposite sides of the barycenter; when the planet is on the left of its orbit, the star is 180° around on its right.

The problem we had was that we mistakenly had the two objects on the same sides of their respective orbits, so (for example) both were on the left at the same time. It was a subtle enough mistake that I totally missed it, but of course the more eyes you have on something the more likely someone will notice, and many commenters did. I personally thank those who pointed it out and freely admit we screwed that part up.

Part of science, you see, is owning up to errors. The whole point of the scientific endeavor is to approach the truth, the reality of things, ever more closely. If you can’t admit your mistakes, you’ll carry them along with you, and you’ll wind up moving in the wrong direction. In this case our error was one of display, not (directly) content, but the concept still applies.

And we certainly didn’t want to confuse anyone watching and trying to figure this out! You’re on this journey, too, and the reason I do all this is to take you along, share my joy of science, and hope that you too will delight in learning more about the Universe and seeing it as it is.

Per gaudium, ad astra.

Aug. 6 2015 7:00 AM

Experimenting With Megan Amram

Being funny is hard. But Megan Amram is good at it.

She was a writer for Parks and Rec, and I could probably stop there because cripes, do you need anything else on your CV? But it’s important to note that the show straddled a fine line between satire and sweet, snarky and sincere, and did so masterfully.

Amram is continuing that tradition: She has a new Web series called “Experimenting With Megan Amram,” which just started up on Amy Poehler’s Smart Girls YouTube channel. The premier episode is up, and I really enjoyed it:

I laughed a lot watching this; Amram skates perfectly on the line between parodying terrible and fatuous women’s talk shows and actually presenting good science info in a positive and funny way. And she does all this while also supporting women in STEM (science, technology, engineering, and math). That’s quite a balancing act.

Not only that, but she also provides instructions on how to make the potato clock (which is a real thing, and a staple of middle school science classes).

She’ll have a female STEM professional as her guest every week,* which is terrific; women are underrepresented in almost all STEM fields, and I think just giving a higher profile to them will help. Getting more role models in front of young girls at the very least can’t hurt. Besides Amram herself, of course; while not technically a working scientist (though she wears a lab coat!) she loves science and math, and grew up in a science-oriented family. And she does have a degree from Harvard University, apparently, which is probably worth something.

New episodes come out every Monday, and the only thing I don’t like about the series is that only six episodes are planned. Happily, Amram has a book out called Science … for Her!, which I have not read yet but I will because (full disclosure) she’s sending me a copy so I kinda have to. Honestly I’ve been meaning to read it anyway, because it looks really funny and has enough snark to power a small town.

You also should follow Amram on Twitter, if only because of her avatar. And check out Poehler’s Smart Girls website, especially if you are or know a young woman who’s interested in STEM. And really, even if she isn’t interested. Maybe it’ll change her mind.

P.S. While I'm at it, this Kickstarter for a STEM video series/investigation kit designed specifically for girls looks very cool. It has about a day left and is already funded, so it'll go for sure, but I imagine a lot of teachers out there might be interested in signing up. Hat tip to my pal Tara Theoharis.

*Hopefully one will be a cartographer so she can look for Miami, England. I won’t give away who the guests are, but hint hint.

Aug. 5 2015 12:00 PM

An EPIC View of the Moon Transiting the Earth!

Just a few days ago I wrote about the DSCOVR satellite delivering gorgeous views of the Earth from space, but it just massively one-upped itself: Here’s an animation of the Moon passing in front of the Earth as seen by the satellite’s Earth Polychromatic Imaging Camera, or EPIC! And it’s even cooler than that: In the animation, you’re seeing the fully illuminated far side of the Moon!


The Deep Space Climate Observatory, or DSCOVR, was launched on a SpaceX Falcon 9 rocket in February. It was put into an orbit around the Sun that’s about 1.5 million kilometers smaller than Earth’s, in a direction toward the Sun. This region of space is called the first Lagrange point, or L1 point, and due to a quirk of gravity this is a stable configuration, like sitting in the trough between two hills. At this spot, DSCOVR points toward the Earth with the Sun behind the satellite, so it perpetually sees the sunlit day-side of the Earth. Update, Aug. 5, 2015: Oops! I meant to add a link to a description I did of Lagrange points, because they're cool. Also, technically, the L1 point is metastable, not stable; if nudged, an object there will fall away from the L1 point.

DSCOVR sits in a gravitationally balanced point between the Earth and Sun, 1.5 million km closer to the Sun.

Diagram by NOAA

The Moon goes around the Earth once a month on an orbit tilted to the Earth’s orbit around the Sun. DSCOVR is four times farther away from the Earth than the Moon is, so it’s well outside the Moon’s orbit. Twice a year or so everything lines up just right, and Earth, Moon, and DSCOVR form a perfect line. If the timing is right, DSCOVR will then see the Moon pass directly in front of or behind the Earth, what astronomers call a transit.

In this case, with the Moon in front of the Earth, DSCOVR sees the Moon’s far side, the side always facing away from the Earth, where we landlubbers never see it. That gives the Moon an odd appearance, since there are fewer large dark features on the far side than the one we see.

Also, we tend to think of the Moon as being very bright, silvery, and shiny, but in fact the Moon’s surface is quite dark. At night, with nothing to challenge it, the Moon looks incredibly bright, but in reality the surface is quite gray. You can see that in the DSCOVR animation, too.

I’ll note this isn’t the first time we’ve seen such a transit from space; back in 2008 the EPOXI spacecraft took a very similar series of shots. This one is much higher resolution, of course, with everything looking much sharper. Here’s the EPOXI animation:

Still pretty neat. I’ve been interested in the DSCOVR mission for a long time, ever since Al Gore proposed it (as Triana) as a way to raise awareness of our planet and its environment. I think that’s a fantastic idea, and animations like this are a lovely and exciting bonus. Remember, that’s us down there, every single one of us on (and off) the planet.

We see the Moon moving across the sky all the time from Earth, and it’s a beautiful thing. But when we see it from space, from quite literally the other side, why, it takes on a new dimension, a new perspective, and becomes even more awe-inspiring. The clockwork of the heavens is a wonder to behold, and now we can see it from many angles. We’re a part of that mechanism, and I think that’s an excellent thing to be reminded of from time to time.

Aug. 5 2015 11:19 AM

Update: Science Luau Has Five Openings

Do you like science? (Of course you do.) Do you like taking vacations in a tropical paradise? (Of course you do.) Do you want to hold a seahorse in your hand, sit near an active volcano, look at sunspots through a telescope, go night diving with manta rays, and hang out with other like-minded folks?

(Oh yes. Yes, you do.)

I have some good news for you. My wife and I run the company Science Getaways, where we take normal vacations and add science, so you can take a vacation with your brain. We’re calling this year’s trip a Science Luau, since it’ll be on the Big Island of Hawaii.

Science Luau sold out immediately (we keep them small and personal, so everyone gets to share in everything and really soak in the experience), but we just had a family cancel, so we have room to take five more people.

The Luau is from Sept. 14 to 20. You can read my previous post to get all the information about it. One note: The trip to the Mauna Kea summit is still full, so that option isn’t available. But everything else is!

If you’re interested, contact us via email using the link on the Science Getaways website (the registration page is no longer available, so the first five to email us get the spots). Mahalo!