The entire universe in blog form

Jan. 21 2015 7:30 AM

Two New Planets in the Solar System? Not So Fast, Folks.

A team of astronomers made something of a news splash late last week when they announced they have indirect evidence that there could be one or more massive planets orbiting in the solar system well beyond Neptune.

I read their journal paper, and their argument is certainly interesting (I’ll explain it in a sec). But let me be clear here: Their evidence of any possible planets out past Neptune is indirect (they don’t have photos or anything like that), it’s based on a small number of objects, and we do have evidence that there aren’t really big (like gas giant–sized) planets past Neptune. And it pains me to even have to bring this up, but of course this has nothing to do with Nibiru crackpottery, either.

Bottom line: To me, this is an interesting and potentially promising line of research, but right now it is quite inconclusive about the existence of planet-sized bodies past Neptune.

How this works isn’t that hard to understand in principle. (Note: After writing this but before posting it, I found that the AstroBites blog also discusses this topic, with more technical info.) In our solar system we have the Sun at the center, and it pretty much runs everything. It has 98 percent of the mass of the solar system, so its gravity is in charge of how everything else moves. BUT, there are also planets that have gravity as well. Their gravity is weak compared with the Sun’s but is strong enough that, given time, the planets can affect the orbits of other objects.

Out past Neptune is a region occupied by objects that are similar to asteroids but made of ice instead of metal and rock (making them more like comets, really). There are various names for them, but in general they’re called trans-Neptunian objects, or TNOs. Some are on circular orbits, some more elliptical, some have orbits tipped to the plane of the solar system, some don’t.

A handful, about a dozen discovered so far, have really weird orbits. They are highly elongated, and tipped significantly to the plane of the solar system. The authors of the study call them Extreme TNOs.

Their orbits are difficult to explain from what we know about the solar system now. However, the authors note that there is a comet called 96/P Machholz 1 that also has an odd orbit. It goes around the Sun backward (retrograde) relative to the planets, and the shape and orientation of its orbit change over time. This is due to the influence of Jupiter; the comet’s orbit takes it out as far from the Sun as Jupiter’s orbit, so the huge planet pokes and prods the comet over time. This changes the comet’s orbit, making it undergo all sorts of peculiar behavior.

The authors then speculate that the weird TNOs may be explainable in a similar way. The TNOs fall into four groups according to distance, implying a series of planets at distances ranging from 40 to 150 billion kilometers from the Sun. (For comparison, Neptune is about 4.5 billion km out.) They don’t give specifics about the possible masses these planets would need, except to say they would need “at least several Earth masses” to affect the TNOs.

Again, the evidence they present is interesting, maybe even compelling, but it by no means is proof. They only look at the orbital characteristics of about a dozen extreme TNOs, and it’s hard to extrapolate safely from that. It seems clear something odd is going on, but the mechanism behind it isn’t clear. Planets? Maybe. But it could be something else.

I’ll note that a similar study was done with long period comets, which also found weird orbital characteristics that could be explained by a planet or planets past Neptune affecting their orbits. Unfortunately, this too relied on small number statistics and is interesting but not conclusive.

If these planets exist they can’t be too much bigger than Earth. Otherwise they’d have been seen by now; the NASA infrared survey observatory WISE has shown that no more Jupiter- or Saturn-sized planets can exist in our solar system, even way far out.

Personally, I’d love to have direct evidence of such planets. When I worked with Hubble, I spent some time trying to figure out ways of finding such planets! There’s no real theoretical reason they don’t exist, and we see evidence of planets orbiting other stars at great distances. So why not?

In the end, this research is perhaps motivation to keep looking. Even big planets would be terribly faint and difficult to detect at 150 billion km, so it may be quite a while before we have a confidently complete survey of the solar system. And even if they don’t exist, I’m glad people are still thinking about things like this. It’s best in science not to get too complacent with the “current understanding.” Nature is tricky and a lot more clever than we are.

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Jan. 20 2015 12:50 PM

The Hairy Star, the Hunter, and the Seven Sisters

On Jan. 10, 2015, astrophotographer Jerry Lodriguss took what may be my favorite picture of the bright Comet Lovejoy I’ve seen so far. Check this out:

Jan. 20 2015 7:00 AM

Dawn Approaches Ceres

Ceres is the largest asteroid in the solar system—about 970 kilometers in diameter—but so far from Earth that it generally just looks like a blurry disk at best.

But that’s about to change. A lot. The Dawn spacecraft is slowly edging toward the asteroid, and on Jan. 13, 2015, it took a series (haha! I love homophones) of images that have been stitched together to make this nifty animation:

Dawn was about 383,000 km (238,000 miles) from Ceres when it took those shots, which is the same distance the Earth is from the Moon. Details are still difficult to make out but you can see a bright spot (I suspect the same one seen in earlier Hubble images) and some large craters. You can also see Ceres is noticeably flattened; it’s about 7 percent wider across the equator than through the poles (though to be fair I think that looks a bit exaggerated due to the location of the terminator, the day-night line).

These images are tantalizing—they rival but don’t quite surpass the best images of Ceres taken by Hubble—but in a little while we’ll be seeing much, much more detailed images of this world. It’ll eventually orbit only a few hundred kilometers over the surface, and the images returned will be quite high resolution indeed.

Dawn launched in 2007 after an interesting history (it was canceled by NASA, then reinstated), and reached the asteroid Vesta in 2011. It orbited Vesta for more than a year, mapping its surface in exquisite detail. It left Vesta in September 2012, and spent the next couple of years moving toward Ceres. It’s approaching now, and is expected to achieve orbit in early March.

Dawn uses an innovative engine called an ion drive. Any engine to move a spacecraft uses Newton’s third law of motion: Every action has an opposite and equal reaction. If you throw something really hard in one direction, it pushes on you equally hard in the opposite direction.

Rockets usually combine a huge amount of chemicals together, which get very hot, expand rapidly, and blow out the back of the rocket. This is a pretty violent effect, and it produces a lot of thrust.

Ion engines are different. They use either magnets or electric fields to accelerate and shoot individual atoms out the back of the engine. The atoms have a lot less mass than what’s used in chemical rockets, but they move a lot faster. The overall effect is a very low but extremely efficient thrust, and you can keep the engine blowing out atoms for years at a time, building up a huge speed. Dawn’s engines use an electric field to fling out xenon ions, and its fuel tank only carries about 425 kilograms (940 pounds) of fuel; in a day it only uses about 280 grams.

But that’s why it’s taken so long to go from Vesta to Ceres; it thrusts low but long. Now it’s approaching the giant asteroid, and soon it will go from a fuzzy disk to a fantastically detailed and amazing world. Stay tuned. This is going to be great.

Correction, Jan. 20, 2015, at 15:30 UTC: Arg! I originally misstated that series and Ceres are homonyms, but they are homophones. Homo=same, nym=name, phone=sound. So two words that are spelled the same way but mean different things are homonyms, but two words that sound the same but are spelled differently are homophones. I blue it their.

Correction, Jan. 20, 2015, at 16:30 UTC: I also originally misstated that these images were from the low-resolution camera, but the framing camera is the only optical-light camera on board Dawn. There is also a spectrometer that can do surface mineralogy, and a gamma ray and neutron detector that can determine elemental composition on and slightly below the asteroid surface.

Jan. 19 2015 12:36 PM

Talking Nerdy to Me

My friend Cara Santa Maria hosts the science podcast Talk Nerdy, where she talks to scientists and science communicators about, well, science. She invited me on, and the episode is online.

We talked about a wide range of stuff: meteorology, clouds, snow, why we love to do and talk about science, as well as (being who we are) the politicization of science and why that’s so dangerous right now. She brought up the recent issue of the QVC hosts trying to figure out what the Moon is and the appointment of anti-science senators to subcommittees that oversee critical science agencies.

It was fun to talk to her (and I apologize—she was in L.A. and I was at home in Colorado, and I don’t have good headphones; she had to edit it a bit to minimize a slight echo of her voice coming through my speakers. I really need to get a good set of headphones!) and let the conversation cover so much ground. I’ve been so busy lately writing and working on other projects that it’s been a while since I just sat and had a random-access conversation about science. I need to do this more!

Thanks for having me on, Cara. It’s always cool to get a little nerdery going.

Jan. 19 2015 7:00 AM

Was 2014 Hot Enough for You?

I’m not a huge fan of “hottest year” type statistics, as I’ll get to in a moment, but this one is important for two reasons: One is that there was no El Niño last year, which tends to drive global temperatures up. (Many record years were ones that had El Niños.) 2014 broke the record without any help. The other is that, according to the NOAA and JMA, 2014 was statistically significant.

Let’s say you flip a coin 10 times, and it comes up heads six times. Is that significant? No, it’s very likely just a random fluctuation, because if you flip a coin 10 times you expect pretty big deviations from a 50/50 distribution of heads and tails. If you flip it a million times and get 600,000 heads, then you’re talking significant.

2014 was like that. Sometimes a year isn’t a whole lot hotter than some previous year and may not be statistically significant. But 2014 was hottest by enough of a margin to make the claim.

Even then, I cast something of a skeptical eye when an individual record is broken. Maybe something else happened that was odd, unusual, pushing the temperatures that particular year to new heights. Maybe the next year, things will “regress to the mean,” head back down toward average.

So that’s when you bring in the most important issue here: context. History. Trends. 2014 may be the hottest year on record … but of the 10 warmest years on record, nine of them happened since 2000.

That’s the important issue here: Not that any one year is the hottest, but that they’re all clustered in the past few years.

JMA trend
Goin' up. The gray line is deviation from the average surface temperature (the average is taken from 1981–2010), blue is a five-year running mean, and red the linear trend over the whole period.

Graph by the Japan Meteorological Agency

It’s getting hotter. This brief animation shows it very, very well. No one record is that exceptional, but they happen more and more now than they did a century (or even a few decades) ago. Few records for hottest year happened in the early 1900s, but now every year has a decent shot at it.

So much for the “pause.” As we’ve seen over and over again. If you’re claiming that temperatures haven’t gone up in the past 16 years, you’re looking more silly every year.

Of course, deniers gonna deny, but, like cooler years, they’re increasingly becoming something of the past.

Jan. 18 2015 7:00 AM

The Flashing Eye of a Cyclone From Space

I’ve posted a lot of images of cyclones from space … but I have never seen anything like this! It's tropical cyclone Bansi, which has been blowing in the Indian Ocean, a few hundred kilometers east of the island of Mauritius, which is itself east of Madagascar. Seen in this photo from the International Space Station, it looks like the storm is powering up some sort of weapon.

Jan. 17 2015 7:30 AM

Is the Moon a Planet? QVC Asks, I Answer.

I’m not a big fan of definitions in astronomy. I’ve been pretty clear about this in the past; Nature is way less anal about boundary lines than humans are. Borders between categories of objects are fuzzy, and while it’s OK to put things in boxes (Jupiter is a planet, the Sun is a star, the Milky Way is a galaxy), it can get tougher when you have two similar objects that you nevertheless think should be on opposite sides of the line. It can be confusing.

And then you have what happened on QVC recently.

QVC is an online and TV shopping channel. Recently, host Shawn Killinger was featuring a line of cardigans by designer Isaac Mizrahi. She described the pattern on one: “It almost kind of looks like what the Earth looks like when you’re a bazillion miles away from the planet moon.”

To her credit she laughs at herself and says she just meant to say “looking back at the planet from the Moon,” not “planet moon”. But then the conversation takes an odd turn. Watch:

Killinger at first correctly says the Sun is a star, and the Moon is not a star. But then Mizrahi says the Moon is a planet, and she questions that, saying the Moon was never included when you learn the planets. She also goes back to saying it’s a star.

Someone off screen then gets on Google, and says “the Moon is a natural satellite.” This confuses both Killinger and Mizrahi, who then quickly move on to selling more clothes.

Let me cut through the confusion: The Sun is a star, a huge object that has ongoing nuclear fusion in its core. At the lower mass limit, the definition of “star” can get fuzzy, but the Sun is way to one side of that line, so we’re good.

Is the Moon a star? No. No fusion in its core, and not even close. It’s not a star.

Is the Moon a planet? Well, not really, as a planet is an object that orbits a star, and the Moon orbits the Earth (and yes, wannabe pedants, it really does orbit the Earth and not the Sun).

A satellite is a generic term for an object that orbits another object. You could say the Earth is a satellite of the Sun and be technically correct, though that’s not usually how the term is used. The Moon is a natural satellite of the Earth; it orbits Earth, and is not artificial. Another term for “satellite” is (lowercase M) moon, so the Moon is a moon. A weather satellite is then an artificial moon.

So there. We’re done.

I have to say, the model on the right made me laugh.

Photo by QVC, from the video

… except of course we aren’t. It’s not hard to imagine if the Moon were bigger, say the same size as the Earth. Would it be a planet then? You could say we’d be part of a binary planet, two planets that orbit each other while orbiting the Sun.

Now you might remember that a few years ago, the International Astronomical Union tried to write in stone the definition of what a planet is. I think this is a mistake, and a foolish one; as my friend and astronomer (and the man who wrote the book How I Killed Pluto and Why It Had It Coming) Mike Brown points out, a planet is a concept, not a definition. It’s like “continent”; we have no definition for it—it’s more of an idea that helps you categorize things in general terms.

Is Australia an island or a continent? Yes.

By the definition decreed by the IAU, a planet orbits the Sun. But each component of a binary planet orbits the other one. So are they a planet, or two planets, or two satellites, or what? I could argue any and all of these. The fact that the definition falls apart so easily is a pretty good indication that using a definition is a bad idea in the first place.

The center of mass of the Earth-Moon system is inside the Earth, so we can safely say the Moon orbits the Earth. But if the Moon were a bit more massive, it wouldn’t be quite so clear. Ceres, the largest asteroid, was thought to be a planet for a few years before it got reclassified into the new category of “asteroid.” And it’s way smaller than the Moon.

What if the Earth didn’t exist? The Moon is pretty big, and if it orbited the Sun where the Earth is now, would we call it a planet? I don’t think so, since according to the IAU definition, a planet has to be massive enough to gravitationally affect all the objects that share nearby orbits (it’s “cleared the neighborhood around its orbit” is how it’s confusingly stated), and I think the Moon would fail that criterion. But that’s not a great definition either, to be honest. It’s complicated and weird and still mighty fuzzy along the borders. My gut feeling is that if we saw a solar system exactly like ours, but with a Moon-sized thing where the Earth is now, we might call it a planet.

Happily, I have a brain as well as my gut, and my brain says, “So what? That object is a big, round, interesting world, so who cares what you call it? Let’s study it!”

That’s science, and it’s way more interesting than nitpicky semantics.

And one final thought. A lot of folks online are making fun of the Killinger and Mizrahi for their discussion, but I think it’s fine. First of all, they’re curious about astronomy, and it led to getting an answer (even if I might quibble over how it happened). Second, it started a larger conversation about what all this means.

And third, what they were arguing over is a subtle, layered, and difficult concept that had astronomers from all over the Earth arguing for years about what it means. And they’re still arguing over it!

So if you want to feel smug and superior about the TV hosts, hey, that’s your choice. But people in glass planets shouldn’t throw asteroids.

Jan. 16 2015 1:05 PM

SpaceX Releases Dramatic Photos and Video of Rocket Landing Explosion 

Holy cow! Watch this amazing Vine video of the SpaceX Falcon 9 booster crashing as it attempted to land on a barge last week after a successful launch to the space station. Make sure the volume is up, because holy wow.

The Jan. 10, 2015, launch of the Falcon 9 rocket went well, but the attempt to reland the first stage booster vertically on a floating platform/barge in the Atlantic didn’t go quite as planned.

Amazingly, the booster slowed, found the barge, and was able to target it for landing (all autonomously, mind you). But then something went wrong at the last moment. The fins used to steer it ran out of hydraulic fluid. The booster tipped at an angle, and the engines couldn’t compensate. It crashed, released fuel, and exploded.

booster crash
The Falcon 9 booster came in too fast and at an angle, leading to an overly dramatic landing.

Photo by SpaceX

A lot of people are calling this a failure, but as I said in my original post about the landing, it’s more fair to call it a near-success. Most of the procedure to land the booster went nominally, and now the cause of the crash is known. As Elon Musk points out, the next flight will have more of the hydraulic fluid on board, so the fins should continue to work.

Speaking of Musk, I have to hand it to him: He’s a master of PR. His tweets about the crash were good-natured and even funny:

"Rapid Unscheduled Disassembly" may have to become a new phrase in the lexicon.

I liked his next tweet even better:

This was a serious event, and I have no doubt it’s taken very seriously inside SpaceX. But the public sees this differently, and sees Musk differently, so these tongue-in-cheek tweets put a great spin on the event.

The next scheduled launch of a Falcon 9 is no earlier than Jan. 31, when it will loft the Deep Space Climate Observatory over a million kilometers from Earth.

Jan. 16 2015 12:22 PM

Beagle 2, Lost on Mars a Decade Ago, Has Been Found

In late December 2003, the European Space Agency’s Mars Express spacecraft entered orbit around the red planet. Part of the mission was to send a lander, the Beagle 2, down to the surface to study the geology and other conditions at a site where water was known to have existed long ago.

Things didn’t go as planned. The lander went down but never sent a signal back home. Efforts to recover anything were for naught, and no one even knew if it landed successfully or if it had crashed onto Mars. The lander was declared lost in February 2004.

But now it’s been found! Using images from the HiRISE camera on the Mars Reconnaissance Orbiter, the Beagle 2 has definitely been spotted on the surface. Not only that, but it looks intact; that is, it didn’t crash into the surface. It appears to have landed safely … but it also looks like the solar panels needed to power it didn’t fully deploy.

That spelled doom for two reasons. It couldn’t get all the juice needed to operate, but also the panels, which were supposed to open like flower petals, needed to be fully deployed to uncover the antenna used to communicate back to Mars Express and therefore to Earth. With the antenna blocked, the mission was doomed.

Beagle 2
A wider angle view shows what may be more of the landing equipment on the surface. Click this for an animated GIF showing slight movement over time as the Sun angle changed.

Photo by NASA/JPL/University of Arizona

In some sense this is, well, not good news, but welcome. The lander, sadly, is dead and has been for a decade; there’s nothing that can be done about that. But, it shows that the mission did touch down safely, and that’s a very big deal to the engineers who designed the mission and who want to know what went wrong. Follow-up images will hopefully show which panels opened and which didn’t, and that may lead to a better understanding of why they failed.

It’s taken so long to find it because the lander is just a couple of meters across, and it landed in a region more than 15,000 square kilometers in size. Here’s an image that has the Beagle 2 in it. See if you can find it. Have fun.

It’s awful that this part of the mission failed—and mind you, the Mars Express Orbiter itself has been running beautifully and taking images and data of Mars for 11 years now!—but this is not the last time the ESA will want to land on Mars. A failed mission is a learning opportunity, and finding Beagle 2 means the chances of the next landing being a success just went up.

I tip my hat to the Beagle 2 team and to the lander itself. May its travails lead to better fortunes down the line.

Jan. 16 2015 7:00 AM

Welcome to Crash Course Astronomy!

It is my pleasure to introduce you to the very first episode of my new online video series, Crash Course Astronomy.

I’m not gonna lie to you: I’m pretty happy about this. It was a lot of fun to write, and a lot of fun to film it. I hope y’all like it.

We have a lot more episodes planned, going from naked-eye astronomy (hubba hubba), through the solar system, out to the stars, to the galaxies and the Universe itself. There’s a lot of stuff out there, so there’s a lot of cosmos to cover.

And allow me to indulge myself for a sec here. I’m really excited about this series. I’ve wanted to do something like this for years, but lacked the resources to do it myself (also, I’d rather pull my own head off than edit video). Working with the Crash Course team has been fantastic. They’re dedicated, talented, smart, fun, curious—pretty much all the characteristics I like to see in human beings.

And the thing is: They’re honestly excited and motivated to work on these series (which also include SciShow and Sexplanations). Visiting Montana to film these episodes is like pure fuel for the brain; seeing everyone work so diligently makes me want to work harder to make better content.

So my sincere thanks to Hank and John Green, and to the folks who work on my show: Blake de Pastino, Nicholas Jenkins and Michael Aranda, Nicole Sweeney, and of course my dear friend Dr. Michelle Thaller, who has been essential in helping me not forget to mention obvious stuff in the videos (and correcting me when—rarely, of course—I’m totally off base). Thanks also to Derek Muller of Veritasium for being there at the very start, and to the folks at Thought Café, who make the adorable videos, including me as, apparently, a Canadian from South Park.* And of course, thanks to PBS Digital Studios for making this all possible (read this to see how).

And don’t forget to subscribe to Crash Course on YouTube! You can also support us on Subbable if you’d like.

But mostly, just thanks for watching. I was pleased to find I learned things writing these episodes. I hope you do too.

*Update, Jan. 16 at 22:00 UTC: Somehow Derek Muller originally didn't get listed in my thanks to folks, so I added him.