Bad Astronomy
The entire universe in blog form

March 29 2015 7:15 AM

Crash Course Astronomy Outtakes

When you watch an episode of Crash Course Astronomy, you no doubt marvel at how clearly cut, professional, and perfect it is. The thing is, what you don’t see are the 18 bazillion times I stumble on a word, say things out of order, realize the grammar is wrong, and so on.

Happily, or embarrassingly, we get a lot of that stuff on camera. A Crash Course tradition is to gather those outtakes every 10 episodes and create a blooper reel. My editor, Nicole Sweeney, was maybe a little too gleeful to do this. But she did, so here you go: the Crash Course Astronomy outtakes from our first 10 episodes.


A lot of folks were asking what I’m doing with my left hand at the end of many of the takes. I’m scrolling through the teleprompter control, resetting it to start again with the line we’re recording. These lines are hard enough to say without a teleprompter!

And oh my word how much do I love Thought Café's title graphic for this episode? If you don't get it, this may help. Next week we’ll start up once again with our regular episodes. Until then, I will endeavor to continue to screw up my lines.

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March 28 2015 7:15 AM

Like Tears in Rain: Our Scars on Mars Fade

When the Curiosity rover landed on Mars, it wasn’t alone. On its way in it also dropped its heat shield, its backshell and parachute, and the rocket-powered sky crane.

That last piece of hardware was pretty much what it sounds like: A platform that used rockets to hover over the surface of Mars, lowered the rover down, then blasted away to a safe distance once Curiosity was firmly down. The sky crane rose in a parabolic arc, then impacted the ground, hard, about 650 meters away. It was still moving horizontally, so it left a blast pattern on the surface, blowing the dust away off the ground. The dust is brighter than the rock beneath, so it left behind a dark splash pattern.


That was about 2.5 years ago, and Mars hasn’t sat still. Weather and winds have beaten at the marks left by Curiosity’s accouterments, and they’ve faded with time. JPL just released this amazing animation composed of images taken by the HiRISE camera on Mars Reconnaissance Orbiter, showing the erosion of the marks over time:

Photo by NASA/JPL-Caltech/Univ. of Arizona

As you can see, the marks have faded, most likely gradually being covered over by dust. The other pieces of hardware show similar changes (though less dramatic, given their smaller impacts)—you can watch the animations for the heat shield, the backshell and parachute, and the rover landing site itself (of course, Curiosity has long since left; it’s a rover).

It’s not as simple as fading, though; the marks from the sky crane have also recently darkened. It’s not clear why, though it’s possible dust blew in, then blew out again. We’ve seen the dust on Mars has done more elaborate and weirder things.

This is more than just interesting: We’re gearing up to send more probes to Mars, and eventually people. Understand the Martian weather will be critical. The dust is extremely fine, like talcum powder, and made of iron oxide: rust. It will get into everything (it coated Opportunity’s solar panels, reducing power until strong winds cleaned it off later). Understanding the dust transport mechanisms will be crucial for living on Mars as well.

And since you’re here, why not: Back when the landing took place, YouTube user Dominic Muller created an amazing video using images taken from the descent camera on the sky crane; he used a technique called interpolation to smooth out the video, and if you haven’t seen it (or it’s been a couple of years), watch it! It’s quite remarkable.

March 27 2015 7:00 AM

The Year of Living Weightlessly

Update, March 27, 2015, at 20:00 UTC: Success! The launch was on time and flawless, propelling the astronauts to orbit. They are scheduled to meet up with the ISS at 01:36 UTC tonight.

Today, at 19:42 UTC (3:42 p.m. Eastern U.S. time), astronaut Scott Kelly and cosmonaut Mikhail Kornienko will ride a Soyuz rocket to the International Space Station. This isn’t an ordinary mission: They will stay aboard ISS for a year, twice as long as the usual NASA expedition length. The purpose is to study long–term effects of microgravity on the human body, to learn more for a possible trip to Mars.*


Expedition 43, as this one is numbered, has a number of different research directions, including seeing how the lengthy flight affects behavior, physical function, eyesight, metabolism, and more—things we know are affected by prolonged low-gravity conditions.

The reasoning behind this makes sense; a long flight to, say, Mars will seriously hamper astronauts’ ability to move around once they land.

I’ll note this isn’t the longest time people will have spent in space; two Russians spent more time on the old Mir space station, and two others spent a year on Mir as well. But this will still be pretty interesting from a biophysical point of view. A lot of work has been done in this field, of course, but having two people up that long at the same with consistent tests should prove helpful.

Not only that, but Kelly has a twin brother who will stay on Earth to provide a control group of sorts. His brother, Mark, is also an astronaut (the only siblings who have both been in space) who is married to ex-congresswoman Gabby Giffords. Quite a family.

I wonder what the outcome of this mission will be. It may show us that long-term space flight is too debilitating; if that’s the case, then we may need to take seriously the idea of rotating structures to mimic gravity. Those are more expensive and have to be big to avoid the spin making astronauts dizzy. I’d love to see some of those built to test out how well humans can perform on them. I’m sure either way it will help inform longer space missions.

Personal opinion time: This mission is also being billed as a precursor to flights using the Space Launch System with the Orion capsule, a future I think is a dead-end for NASA. SLS is far, far too expensive and NASA doesn’t have the budget to make it sustainable. There are serious concerns that building it will cost so much that there won’t be money left for actually using it.

I agree with space activist and writer John Strickland on this; Scientific American put up an editorial about this one-year mission, and Strickland left a comment there. In it, he wrote that for the same money SpaceX could deliver a lot more. The Falcon Heavy rocket demo launch should happen later this year; I’d like to see that go successfully first before speculating any further. But it does seem like the right move for NASA. I have very serious doubts about SLS.

Anyway, I expect the Soyuz launch of the Expedition will be covered on NASA TV and its Ustream channel. I’ll be watching live, and tweeting about it too.

* Also riding on the rocket will be seasoned cosmonaut Gennady Padalka, who will not be staying for the entire duration of this extended mission.

NASA has a peculiar numbering convention for ISS missions. A new Expedition starts when three of the six crew members on board leave (officially when the door to the return capsule closes), so Expedition 43 started in early March, and there are now three people on ISS. Kelly, Kornienko, and Padalka will join 43 already in progress. The three on there now will leave in May, and that's when Expedition 44 starts. Kelly and Kornienko will stay through Expedition 46, overlapping with the crews from the other Expeditions.

March 26 2015 7:00 AM

The Catastrophe That Must Not Be Named

By now you may have heard that Florida Gov. Rick Scott is a flat-out global warming denier, even though his state is arguably the most vulnerable to sea level rise and other problems that are surely to come if we do nothing.

But even doing nothing is too much for Scott. Four former officials at Florida’s Department of Environmental Protection have claimed that Scott put out an unwritten rule ordering that no one at the DEP even use the phrases global warming or climate change in any of their communications.


There has been some back and forth in various media about whether this was true or not—it’s hard to prove an unofficial decree—but then this video has come along, which pretty much confirms the order was real. It shows Florida’s emergency management director Bryan Koon testifying to the state Senate about receiving funds from the Federal Emergency Management Agency (which has threatened to deny some funding to states with climate change–denying governors). During the Q&A, Sen. Jeff Clemens (D–District 27) has some fun at Gov. Scott’s expense.*

Koon’s visible discomfort during this whole thing makes it pretty clear what’s what. It would be almost painful to watch … except for the obvious delight of the other senators, who cannot stop laughing at the whole ridiculous mess.

I’m glad they recognize that. The rest of the country, the world, is laughing at their governor’s denial of reality. The problem is laughing won’t change their minds, or get these head-in-the-sand politicians voted out of office … or will it? A majority of voters think climate change is an issue we need to deal with, including Republican voters. If those voters go to the polls and make that stance clear, then maybe those politicians would figure out that all that Koch brothers money won’t help them get re-elected.

Our changing climate needs to be an issue voters take seriously. What starts with laughter now will hopefully turn into the good kind of change later: changing who’s in office.

*Correction, March 26, 2015: This post originally misspelled Florida state Sen. Jeff Clemens’ last name.

March 25 2015 7:00 AM

Did Jupiter Destroy the Solar System’s First Planets?

Our solar system is weird.

First of all, it doesn’t look much like other ones we’ve been finding. A lot of those have Jupiter-size giant planets orbiting very close in to their parents stars (“hot Jupiters”), closer even than Mercury orbits the Sun. By contrast, our Jupiter orbits the Sun much farther out, more than a dozen times Mercury’s distance from the Sun.


Worse, a lot of these other solar systems are compact. They have several planets orbiting close in to their star, and these planets tend to be “super-Earths,” bigger than our home world but smaller than Neptune. They probably have thick atmospheres, too. A good example of this is Kepler-11, which has six planets that orbit their star inside the size of Venus’ orbit.

So why are we so different than everyone else? The answer may be: Jupiter. A new paper has been released that points an accusatory finger at our solar system’s largest world. Ours may have looked a lot like all the others we’ve seen, but Jupiter came along and wiped it out, setting the stage for what see today: lower mass worlds like ours close in, and bigger ones farther out.

Here’s how this works. When the solar system was very young, just a few million years old, it was basically the Sun in the center surrounded by a huge disk of gas and dust. Jupiter formed probably not too far from where it currently is, a few hundred million kilometers out from the Sun … but it didn’t stay there.

Its gravity interacted with the material in the disk around it. The overall effect of this is to cause Jupiter to start moving inward, migrating toward the Sun. It continued to interact with the disk material, including with actively forming bodies that may have been many kilometers or even hundreds of kilometers in size. It would send them inward, crashing into the Sun. As much as 10–20 times the Earth’s mass worth of material could have been wiped out this way by the time Jupiter got to about 230 million kilometers from the Sun (very roughly where Mars is now).

Something stopped its inward movement at that point. The culprit here is Saturn; models have shown that Saturn and Jupiter would also interact gravitationally through a process called a resonance; Saturn repeatedly tugged on Jupiter, pulling it back out of the inner solar system, placing it where it is today.

When it was all done, there was far less material close in to the Sun than there was initially. The inner planets we see today, Mercury, Venus, Earth, and Mars, formed from whatever stuff was leftover, which wasn’t much.

The idea of Jupiter’s migration has been around a long time, but this new model of how it interacts with the disk explains a lot of the weirdness we see now—including why our planets are smaller than we tend to see in other systems (because of the paucity of material from which they formed). The inner planets are thought to have formed as late as 100–200 million years after the solar system got started, and this explains why, too. They formed after Jupiter bullied its way through the system.

It’s also consistent with the existence of hot Jupiters; in other solar systems where a massive planet like Jupiter forms, but no second, slightly less massive planet outside it like Saturn forms, there’s nothing to reverse the course of the bigger one. It keeps moving in until it destroys the inner disk; at that point it stops migrating and you’re left with a system with a big planet orbiting close in.

The Kepler-11 exoplanet system compared with ours. Did we used to look like this? It's entirely possible.

Photo by NASA/Tim Pyle

And here’s a very cool thing: We think super-Earths may form easily and quickly in solar system like ours, perhaps as rapidly as a million years. That may have even happened in our own solar system. But when Jupiter moved in it would have disrupted the orbits of those planets, dropping them into the Sun. If they once existed, they don’t now! Jupiter wiped the slate clean. Then our familiar planets formed later.

Imagine how different our solar system would look if Jupiter hadn’t formed, or Saturn hadn’t reined it in.

The beauty of this model, too, is that it doesn’t just explain what we see, it also makes predictions. For example, if we see an exoplanet system with lots of close-in super-Earths, we should not expect to see a Jupiter-size planet farther out. If it were there it should’ve wiped out the inner planets. If there is a Jupiter-size planet farther out, you should expect to find 1) a second massive planet outside the first, but slightly less massive than the first (if it’s more massive, then it becomes the one to control the situation), and 2) smaller planets like ours in the inner region, not super-Earths. Or maybe nothing at all, if all the material got wiped out.

We’re not quite at the stage yet where we can go through the exoplanets catalog and check that statistically, but we’re getting there. A new planet-finding orbiting observatory is in the works called TESS, which should yield huge numbers of such solar systems, allowing us to check the hypothesis. The Kepler mission, which discovered more than 1,000 planets, has been retooled and may also provide data to confirm or negate this study.

Oh, how I love this. This idea is still just a hypothesis, but it appears to be a good one, and better yet, it can be tested. And here’s the best part: By studying other solar systems, we learn more about ours. An example of one is a poor sample; you need many more to compare and contrast. The early discovery of hot Jupiters threw our ideas of planet formation for a loop, and then super-Earths messed with it more. But we use that data in planetary diversity to expand our models, refine them, and come to a better and greater understanding of ourselves.

Huh. Sounds like a pretty good lesson to me.

March 24 2015 12:26 PM

Sen: Ancient Radioactive Lunar Volcano

For my fortnightly column at this go-round, I had a lot of fun writing about an ancient lunar volcano’s explosive eruption eons ago, the extent of which was mapped using gamma rays from radioactive thorium buried under billions of years of impact-produced lunar dust.

So yeah, I had a lot of fun. Sometimes just researching an article is pretty cool.


As I’ve said before, while the news and other sections at Sen are free, the blogs are subscription only. But if you look at the bloggers there, you’ll find that the price is totally worth it. You’d spend more than that on a book by just one person. And for that you’ll get to read lots of people covering lots of space. Literally.

March 24 2015 7:30 AM

Flying High During a Solar Eclipse

I should know better by now: Whenever I post a bunch of pictures from some astronomical event and say they were the best I saw, someone comes along and proves me wrong.

This photo was taken by frequent BA Blog contributor Geoff Sims, who was flying on a plane chartered to observe the March 20 solar eclipse (the flight was planned by my old friend and dedicated umbraphilic astronomer Glenn Schneider). They were over the north Atlantic at 35,000 feet when he took that shot of the eclipsed Sun, the moon’s shadow darkening the Earth below.

March 23 2015 12:00 PM

Bad Astronomy Video: The Pink and Purple Crab

Take equal parts 1) supernova, 2) Hubble Space Telescope, and 3) Herschel infrared observatory. Mix well. What do you get? Purple (and pink) majesty.

This video is based on an article I wrote about this observation. And yeah, you want to go take a look; the high-res picture is pretty phenomenal.


I love this image of the Crab Nebula, if only because the colors are almost electric. But also because this has been an intensely scrutinized object; people have dedicated their careers to it, and lots of astronomers have done at least some work on it. I have too; I did a bit of coding for a Hubble observation years ago, and developed/updated a classroom education exercise based on the observable expansion of the gas. And, of course, I’ve observed it a zillion times with binoculars and telescopes.

But when you get new tech, like Herschel, you learn new things. Even familiar faces have something to teach us when we see them in a new way.

If there is a life lesson in there somewhere, feel free to find it. 

March 23 2015 7:15 AM

Pluto Naming Rights

In a few months, Pluto’s gonna get a lot less fuzzy.

Right now, the distant world is a scant three pixels across in the camera of the New Horizons space probe. But it’s fast approaching; New Horizons recently crossed the distance where it was closer to Pluto than the Earth is to the Sun. Given that Pluto is 40 times farther from the Sun than the Earth is, you can see that the probe is nearing the goal of its mission.


Closest approach will be in mid-July 2015. A bit more than a month before then Pluto will be more than a dozen pixels wide in images. Still not much, but enough to start seeing major features, coloration or brightness differences from spot to spot on the surface. Closing in at 14 kilometers every second, Pluto will grow rapidly, and details will clear.

The transformation of Pluto from a fuzzy blob to a sharp and clear world will be so rapid, in fact, that there won’t be time to name all the new surface features seen. Thinking ahead, the scientists involved have decided to create a list of potential names for features not yet seen. That’s pretty clever, but what names should go on that Plutonic list?

That, it turns out, is up to you. Seriously. The New Horizons team, in coordination with the International Astronomical Union (the official keeper of cosmic names), has a website called Our Pluto where you can suggest names and vote for the ones you like.

The names fall under several themes, including explorers (real and fictional), the underworld (Pluto was, after all, the god of the underworld, and the moons are named after various related characters), scientists, engineers, starships and spaceships, and more. They make a special note: “We particularly welcome suggestions that come from the ancient past and from the world’s many diverse cultures.”

This is an interesting idea. It’s not a free-for-all, so that should prevent the usual irritating responses expected from the underbelly of the Internet, and in the end the names from the public are suggestions, not mandatory. But with the IAU involved, the ones chosen will eventually become official.

So here’s your chance to help name a feature on another world! Voting ends on April 7, so hurry. Orbital mechanics wait for no human.

March 22 2015 7:30 AM

Where Are the Pictures of Ceres?

I’ve been getting some emails and tweets asking why, if the Dawn spacecraft entered orbit around Ceres on March 6, haven’t we seen any new close-up pictures for nearly three weeks?

The answer is not that NASA is covering up alien bases or Obama’s birth certificate or any other such nonsense. It’s actually due to gravity and chemistry.


Dawn doesn’t use conventional chemical rocket thrusters. While these can provide a lot of oomph, the fuel is heavy, which means you need to carry more fuel to carry that fuel, and so on. You can change directions quickly, but the cost is dedicating more of your precious payload mass to fuel instead of scientific equipment.

Instead, Dawn uses ion thrusters, which use complex electric fields to fling ionized atoms out the back end at high speed. The thrust is a lot lower, but you use fuel so efficiently you can literally keep your engines on for months at a time. In the end, you get the same ability to change the direction and speed of your spacecraft; it’s just a lot more gentle and takes a lot longer.

The orbital insertion path for Dawn is not an easy one. The new trajectory is in green, and the tick marks are Dawn's positions one day apart. Note the long, looping path designed to save fuel over the old trajectory (red). Right now, Dawn is at the apex of the long loop.

Diagram by NASA/JPL

So instead of blasting toward Ceres and blasting into orbit, it’s more like Dawn is sliding into orbit, catching up with the asteroid slowly and easing its way closer. To do that it flew past Ceres a bit, and is now on the side of Ceres away from the Sun. From its vantage point it’s looking down on the dark side of the asteroid. It’s also on a trajectory that took it farther away from Ceres, and is now falling down closer to it (like tossing a rock in the air, and having it fall back down into your hand).

In fact, a problem with Dawn’s reaction wheels (which are used to turn the spacecraft) caused engineers to put it on an orbital insertion path that’s even more fuel-efficient, to make sure they have extra fuel on hand if they need to compensate for the loss of the wheels. The diagram above shows this, and here's a nifty animation of the insertion as well:

So, though it’s been under the influence of the gravity of Ceres for a few weeks now, it’s not in a low orbit just yet. It will be soon though, and we’ll start getting lovely high-resolution images. I can’t wait. I’m dying to know just what those bright spots are; speculation is rampant among scientists, but really we won’t get definitive answers until Dawn gets close and can watch Ceres over time.

When will that finally start? April, so in just a couple of weeks. Patience, young Padawans. A new Ceres is coming.

Tip o' the electrostatic grid to Rachel WW for the link to the orbit video.