Bad Astronomy
The entire universe in blog form

March 14 2016 9:00 AM

February 2016: Hotter Than Ever

Writing about monthly temperature records is like playing global warming Mad Libs.

“Another record high global temperature was set for [Month][Year], according to [every measurement available], blowing away the last record from [recent month].”

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And here we are again. February 2016 was the hottest February on the planet on record, a staggering 1.35° C hotter than the average. The previous hottest Februaries were 1998 (0.88° above average) and 2015 (0.87°). That’s a huge jump.

Those numbers are from NASA’s Goddard Institute for Space Studies, one of the premier centers for keeping tabs on our ever-warming globe. They are from temperature measurements over land and ocean going back to 1880. They represent temperature anomalies, that is, deviations from an average. In this case, the average is taken over the range of 1951–1980. That makes comparing temperatures easier, and shows that February 2016 was the hottest recorded February for 136 years.

There’s so much to say here it’s hard to know where to begin. For example:

Scrolling through the anomalies, it’s impossible not to be struck by how they are overwhelmingly negative for the first half of the record, then increasingly positive over the second half. In other words, the temperature trend over time is obviously and overwhelmingly getting hotter.

There’s a huge jump in monthly temperatures starting last year, stomping previous records. October 2015 was the hottest October on record. November 2015 was the hottest November on record. December, January, and now February, all records, and by a wide margin.

Last month, January 2016, had the biggest monthly anomaly ever recorded at the time, at 1.14° C. February destroys that record by a full 0.2°C.

These temperature anomalies are compared with the average from decades ago. But if you compare them with temperatures at the start of the range, we’re now approaching 2° C hotter than the pre-industrial level.

global temperature maps
Almost the whole planet is above the midcentury average ... but look at the Arctic. Wow.

NASA/GISS/Gavin Schmidt

These numbers average over the whole planet. But when you map the temperatures by region, you see the Arctic has been suffering an incredible heat wave, with monthly average temperatures as much as 16° C above average. Sixteen! These heat waves go back for months, such that many places in the extreme north basically didn’t have a winter compared with what they normally experience.

Ah, that word. Normal. It’s hard to say what that means any more. A lot of people trying to downplay all this are saying it’s all due to El Niño, but we know that’s not the case; it accounts for only a fraction of a degree of warming. And the Arctic has been warming at roughly twice the rate of lower latitudes for many years. Also, even if you just look at temperatures during El Niño years, those are getting hotter all by themselves! If this were just due to El Niño, those should be flat.

Gavin Schmidt, the NASA GISS director, tweeted a graph showing the temperatures:

global temperatures Feb. 2016
Up, up, and away.

NASA/GIDD/Gavin Schmidt

That includes January and February 2016. Obviously, we’re seeing those huge jumps in temperature now. But also, ignore small-scale variations and look at the trend. Up, up, up: The anomalies were around 0.4° two decades ago. They’re twice that or more now, even before the spikes at the end.

So much for the “pause.” As we’ve seen again and again and again. Not that this will stop those who deny the climate science.

Come to think of it, that Mad Lib I started with? It should really be,

“Another record high global temperature was set for [Month][Year], according to [every measurement available], blowing away the last record from [recent month]. Yet [Republican politician] still denies [scientific result.]”

Remember, folks, this is your GOP front-runner:

That’s not just denial, that’s nuts (the tweet is from 2012, and Trump has since claimed he was joking, but the facts don't bear that claim fruit). And even if he loses the election, there’s always Sen. Ted Cruz, R-Texas, and Rep. Lamar Smith, R-Texas, who will most likely still be in Congress and still doing whatever they can to almost literally throw gasoline on an ever-increasing fire.

Human-caused global warming has been going on for more than a century, and we’re dealing with the consequences now. And when it comes to planning for the future, Nov. 8, 2016, looms large.

March 13 2016 9:30 AM

An Active Volcano Eruption Caught From Space

Momotombo’s been busy.

This volcano, located off Lake Managua (also called Lago Xolotlán) in Nicaragua, has erupted a handful of times in modern history, but starting in March it started popping off hundreds of small explosions, which have thrown an ash plume into the air above it.

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The image above was taken by the Terra Earth-observing satellite on March 2. It’s a combination of visible light (green and red, shown as blue and green) and infrared (shown as red). As I mentioned in an earlier post, vegetation is extremely reflective in infrared, so it looks very red in this image. The plume winds up looking bluish-gray in this combination. Old lava flows are dark brown, and newer ones are more gray-brown.

The plume is roughly 10 kilometers long, to give you some scale. Also, look off to the lower right, in the lake: There lies Isla Momotombito, another stratovolcano. This literally means Little Momotombo Island, which would be adorable if we weren’t talking about a huge pile of rocks surrounding a massive hole that leads down into the Earth’s hellish mantle.

As for Momotombo, the name is Aztec, and apparently means “Big Boiling Summit.” Fair enough.

As regular readers know, I’m fascinated by satellite imagery of volcanoes, but I think that’s a fair thing to be fascinated by. Look at that image! And of course this is terribly useful: Thousands of people live in that area, and satellite images like this one can help authorities understand the situation better, possibly helping in evacuation and rescue efforts if necessary.

That whole part of the world is lousy with volcanoes, many of which are quite active. It’s a populated area, which means they have eyes on the ground, but it’s also helpful to have eyes in the sky, too. Especially with long-term effects: Lava flows and ash plumes can be tracked, vegetation mapped to see what’s affected and where, and more.

We humans have a predilection for living near volcanoes, even when we really should know better. Still, as long as we do, keeping a watch on them from space is a very, very good idea.

March 12 2016 9:30 AM

Why Is There a Huge Mountain on Ceres?

The Dawn spacecraft has dropped itself into its lowest and final mapping orbit around the protoplanet Ceres, and the images it’s now returning are both beautiful and baffling.

We’re still waiting for close-up shots of Occator crater with its bizarre bright spots in it, but in the meantime there’s no lack of weirdness coming from Ceres. The shot above shows Ahuna Mons, a mountain on Ceres 5 kilometers high and 20 kilometers long.

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But what the heck is it?

There’s nothing else quite like it on Ceres, and I wouldn’t expect there to be (to be fair, there are other hills that are similar, but nowhere near as big). Ceres is about 950 kilometers across, with a thin rocky crust overlying a thick water ice mantle and a rocky core. The interior isn’t active like Earth’s, so mountain building isn’t something you’d expect. There are features on the surface indicating the crust has experienced some tectonic activity (cracks, depressions, ridges, and so on), but that was long ago.

The images we’ve seen of Ahuna Mons do give us some clues. The flanks are streaked, indicating what geologists call “mass wasting,” flow of material down the sides. There are bright streaks on the right, possibly due to salt—the bright spots dotting the surface of Ceres may be from briny water squeezed out of the interior; the water freezes, then sublimates (turns directly into a gas) in the sunlight, leaving the brighter salt behind. You can see a couple of small nearby craters that are also bright, and a few bright spots on the mountain flanks, too.

Along the top of the image the material seems to stop rather suddenly, but along the bottom it merges more naturally into the native landscape. That may be an illumination effect (the sunlight is coming from the upper right), but it’s hard to say. Interestingly, there appears to be a slope change in the upper flank; it starts off steep, then halfway down the slope changes to be more gradual. I suspect the steeper material is showing us the original mountain, and where the slope changes is where the debris from landslides has piled up.

The top looks rather flat, like a mesa, but that may be a perspective effect since we’re looking straight down on it. An early image taken from the side does seem to point to a flat top. A 3-D animation made by JPL makes it look pointier, but the relief is exaggerated, so may be a little misleading. The JPL press release describes it more as a dome.

Ahuna Mons
A wider view gives some context. If that helps any.

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Finally, besides the crater to the upper left, the landscape around Ahuna Mons is pretty flat, with gentle, rolling topography. The mountain really sticks out, both literally and figuratively.

So what does all this say? Beats me! But let me speculate a wee bit.

There are a couple of possible explanations. One is that it’s actually the remnants of another asteroid that had a low-speed impact on the surface. But this is pretty unlikely; most impacts are fast enough to do a lot of damage (look at the zillions of craters in the shot!) and getting things just right to leave so much of the impactor intact is just asking too much. Plus, there’s no other damage to the surrounding landscape, which (again due to all the craters seen) must be pretty old. It doesn’t show any resurfacing or anything like that.

The other idea is that it’s some sort of upwelling event from the interior, similar to a volcano on Earth. Maybe there was a crack in the crust there, or it’s just thinner. Water ice from the mantle squeezed up, forming the mountain. Maybe the impact that formed the big crater nearby helped crack the crust down to where the ice could leak out.

Again, I am totally speculating here. Whatever Ahuna Mons is, it’s weird. Pretty much by definition, since it’s unique on Ceres!

We’ll be seeing more data from Dawn over time; it just got into this final mapping orbit a couple of months ago. I’m anxious to see this mountain in different lighting conditions and from different angles. That way a good, high-resolution topographical map of it can be built up, and hopefully its secrets will be revealed.

March 11 2016 9:00 AM

DSCOVR an Eclipse Seen From Space

Earlier this week, the Moon passed directly in front of the Sun to create a solar eclipse … but only if you were in a very specific place on the planet at the right time. The Moon’s shadow on the Earth is small, so if you weren’t on the eclipse path, you saw a partial eclipse, or none at all.

… unless you weren’t on the Earth in the first place. The DSCOVR satellite is 1.5 million kilometers away from our planet, between the Earth and Sun. It looks back at us to provide a stunning and scientifically important four megapixel natural-color view of the world. It had just about the best seat in the house to view the entire event:

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Holy wow. Thirteen images taken over the duration of the eclipse were assembled to create that animation. The Moon’s shadow is the dark spot that moves from left to right. The eclipse took place over the Pacific, and you can see China, Australia, and more under the clouds.

One thing I love about this is that it shows how a solar eclipse is a local event; it only happens where the shadow falls on the Earth, and because the Moon is smaller than Earth and far away, the shadow is small. If you’re on the wrong spot on the Earth, you miss it.

The motions here fascinate me, too. The Earth is rotating left to right (west to east). The Moon is moving in the same direction, off-frame, as it orbits the Earth. It moves around us at about 1 km/sec, so its ground track (the speed it moves across the ground) is actually faster than the Earth’s rotation (which at a maximum is about 0.5 km/sec; there’s a lot of detail here I’m skipping to make the point). So the shadow moves left to right as well, outpacing the surface below it.

DSCOVR orbit
DSCOVR relative to the Earth, Sun, and Moon.

NOAA

And all this is seen from a satellite that appears stationary but isn’t. DSCOVR is in what’s called a halo orbit around the L1 point. This point is in between the Earth and Sun, where the gravitational balance of the Earth and Sun is equal, when you also account for the centripetal acceleration (or centrifugal force if you prefer) of the satellite’s orbit. The point is, all the forces balance and the satellite stays near that spot in space.

Kinda. It actually orbits the L1 point (I refer you to an article at the Planetary Society for more on that), moving around it. If DSCOVR were exactly in the L1 point, then the Earth, Moon, and Sun and satellite would have all been in a line, and you would have seen the Moon pass over the Earth in the animation. But DSCOVR was off that line a bit, so you don’t see the Moon, just the shadow.

This can get a little head-scratchy because of all the angles. For example, it’s possible that from DSCOVR’s viewpoint it does see the Moon pass in front of (what we call transiting) Earth, but there’s no eclipse! That happened in August of 2015:

Amazing. Next year, on Aug. 21, there will be a total solar eclipse that passes right across the U.S. I’m hoping this will be my very first one I’ll ever see; I’ve never been in the right place at the right time. I’ll be writing a lot more about that as the time approaches.

I’ll be on the Earth’s surface when that happens, and I hope we’ll also get images from space by DSCOVR. But you can also be in between: A few lucky people were on an Alaska Air flight which diverted a bit to fly into the path of this last eclipse, and passengers got to see it from the air. The result is, well, see for yourself, in a video that is as delightful in the reactions you hear as the view is stunning.

March 10 2016 12:00 PM

How Do We Know Global Warming Is Real?

If you read the comments of any global warming blog post I write—and I don’t recommend it, unless pain is something you enjoy—you see a lot of people have a very, very fundamental misunderstanding of how global warming and climate change work.

At this point, it’s clear that this must be ideologically driven; the scientific evidence is so overwhelming that there must be some other reason people still deny the reality of both. Still, seeing the sorts of comments deniers make shows that even the most basic concepts of how it all works are being misinterpreted. Willfully or otherwise.

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So here’s some good news: On the blog Open Mind, Tamino has put together an astonishingly well-done, simple explanation of global warming. It starts with temperature measurements but goes into how they are done, how the seas are rising, how flooding has increased, how the poles are melting and glaciers retreating, and then how and why this is tied to human-produced carbon dioxide in the atmosphere.

It’s great, and you should read it.

Will Tamino’s piece slay the zombies of climate science denial? No, of course not. Like I said, facts are irrelevant to deniers unless they can be used as a blunt weapon on reality. But having the facts at your fingertips is always a good thing, and they’re laid out well there. I know I’ll be linking to this quite often in the future.

March 10 2016 9:00 AM

No, That’s Not a Photo of Earth From Hubble

The image above has been getting a lot of attention on social media lately—I’m getting notes on Twitter and Facebook about it even now, a couple of weeks after it went viral. The caption varies from place to place but generally doesn’t have much info, simply stating a variation of “The Earth as seen from Hubble Space Telescope.”

OK, first, read the title of this article again.

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Great. Now, second, this image is in reality CGI created by Mike Kiev (it’s actually part of a very cool animation). I won’t go into details about that aspect of it since Snopes has, as is its usual way, done so capably.

I want to add to what they wrote, though. First, this is nothing like what the Earth would look like from Hubble. For one thing, clouds like the ones depicted tend to be below about 6,000 meters, and the Earth is nearly 13,000 kilometers across. That’s 2,000 times wider! If you saw the Earth as a ball like this, the clouds would barely be discernible from the surface at all.

Also, note the waves in the “ocean.” Those would have to be several kilometers high, which is something I prefer not to think about too realistically. The last time the planet saw waves like that, a huge asteroid or comet had hit off the coast of the Yucatan and the dinosaurs (along with 75 percent of all other species on Earth) were about to have a very bad day.

Also, Hubble orbits the Earth at an altitude of about 570 kilometers. From that height, you can see a swath of Earth roughly 5,000 kilometers across, about the width of the U.S. The edge of the Earth would look curved, but not as severely as shown in the image. I suppose it could have used a fish-eye wide-angle lens, but I don’t think Hubble has anything like that on board.*

Here’s the funny thing though: Hubble used to routinely take images of the Earth. As I wrote on Hubble’s 20th anniversary, some of the cameras used observations of Earth to create a calibration image used to correct the images, a sort of planetary white balance. Hubble orbits at about 8 kilometers per second, so it can’t track the Earth. Instead, the surface streaked by below it, and a time exposure was made to create the calibration data. They looked like this before being processed:

streak flat
The actual Earth from Hubble.

NASA/Mark Clampin

How weird is that? The streaks are actually things on Earth’s surface. They could be rocks, buildings, trees, what-have-you. Maybe you, though that’s a tad unlikely. It’s a big planet.

So that’s what Earth really looks like from Hubble. Perhaps the artist’s image is more fanciful, but to me the reality is just as cool.

*In fact, the widest-angle camera on board Hubble has a field of view roughly equal to the size of a grain of sand held at arm’s length, so yeah. No.

March 9 2016 1:30 PM

FRB Update Part 2: Repeating Fast Radio Burst Opens Up the Playing Field

When I first wrote about fast radio bursts (FRBs—and please read the follow-up on that)—sudden cosmic blasts of radio waves that come and go in milliseconds—I mentioned that lots of different unrelated phenomena can probably produce them. Radio waves are generated by planets, stars, gas clouds, black holes, and a host of other astronomical objects, so there’s no reason to limit ourselves when we think of what their source might be.

Not only that, but gamma-ray bursts, the second most energetic bangs in the Universe since the Big one, are similar in nature, but also come from a variety of different objects. Again, the Universe is telling us to be open-minded.

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And now that looks like it’s the case! A fast radio burst detected in 2012 has now been seen to repeat.

That’s big news. Every other FRB detected has been a one-off kind of thing: Now you see it, now you don’t. But FRB 121102 (named after the date it was first seen, Nov. 2, 2012) has been seen to repeat not just once, but 10 separate times. Whatever is causing it is a pretty eager attention hound.

The repetitions were seen using the Arecibo radio telescope in Puerto Rico over the course of 16 days. Some of the bursts were just minutes apart, but no obvious periodicity (like, one every 10 minutes) was seen over the 10 events.

My first thought when I read this was that maybe we were seeing different bursts from the same area of sky. However, one characteristic of an FRB is its dispersion; at longer radio wavelengths the pulse gets here slower. The amount of dispersion has to do with the amount of material between us and the burst, which is why the pulse spreads out in time. In the case of FRB 121102, each repeated blast has a dispersion consistent with the first one.

So it seems pretty likely these bursts are all coming from the same source.

So what is it? The one-off bursts are probably singular, catastrophic events; explosions of some kind that may destroy the source (or disrupt it so much we don’t see it repeat for a long time). Given the energies and short pulse duration involved, it seems likely that a neutron star is at the heart of this FRB.

A neutron star is a fantastically dense object left over from when a medium-massive star explodes as a supernova. The outer layers of the star are flung off, creating the tremendous display of energy, and the core collapses into a ball of exotic material just a few kilometers across. 

They’re born with ridiculously strong magnetic fields, and they spin very rapidly. They can be pulsars, sending out twin lighthouse beams of energy that sweep around every spin cycle, which we see as blips of energy here on Earth. Some pulsars have such strong magnetic fields they’re called magnetars, and they’re one of the few objects in the Universe that terrify me on every level of my being; they’re capable of truly epic blasts of energy.

Sometimes pulsars have what are called giant pulses, an occasional outburst much larger than normal. It’s not entirely clear what causes them, but such an event from a magnetar might explain the repeating FRB. Clearly, more observations are needed.

One thing that really bugs me about this repeating burst, though: It sits almost exactly in the galactic plane. Our galaxy is a pretty flat disk, and we’re in that disk but offset from the center, so we see the Milky Way as a broad splash across the sky. Massive stars tend to be born very near the galactic midline, and we therefore see most pulsars close to it (what we call “low galactic latitude”).

If this FRB were coming from another galaxy, odds are very high it would appear randomly in the sky. But if it comes from inside the Milky Way I’d expect it to be sitting right on the galactic plane … which it does. So that makes me highly suspicious.

What’s really weird is that the authors of the new observations make a good case that the source really is extragalactic. I mentioned the dispersion, which tells you how much material lies between the FRB and the Earth. FRB 121102’s dispersion indicates a lot of material is between us, more than you’d expect to be in the Milky Way alone. But I wonder; it’s possible that this thing sits on the other side of a dense molecular cloud or some other object that, on a small spatial scale, skews the statistics.

We don’t just need more observations, we need to nail the position of this thing on the sky as precisely as possible. That might help us understand what were seeing.

I’m seeing lots of articles about FRBs now, which is great! It’s a whole new field of astronomy, a new class of objects that we’re just now starting to get a grip on. Things will be messy for a while as we observe more of them. Eventually, I suspect we’ll start to classify them, make zoological sense of them … and then things will get messy again as more details come in. This is what happened with their cousins, gamma-ray bursts (and yes, click that; the discovery and understanding of GRBs is my all-time favorite astronomy story).

When I studied GRBs a few years back, we had a saying: If you’ve seen one gamma-ray burst, you’ve seen one gamma-ray burst. Each burst is unique in some way. FRBs are similar enough as a class to GRBs that it’s a safe bet we’ll go through the same thing with them. They may come from a variety of objects, but the only way to find out more is to find more of them. And you can bet we will.

March 9 2016 11:30 AM

Climate Whirlwind: Severe Tornado Outbreaks Are Increasing

A new study just published in Nature Communications shows a worrisome trend: The number of severe tornado outbreaks is increasing with time.

Many tornadoes appear on their own, but the majority are associated with severe storms that spawn multiple tornadoes. These outbreaks can span many hours and cover a lot of territory, and are obviously extremely dangerous. They kill more than 100 people per year on average and cause billions of dollars in damage.

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The study looked at tornadoes from 1954 to 2014, applying some statistical analysis to the number and strength of each. What they found is interesting, and a little bit non-intuitive, and also may have implications for the effects of climate change.

First off, they found that the total number of outbreaks per year is fairly steady across the date range, at roughly 20 per year (with lots of fluctuations year to year). The total number of individual tornadoes is also steady, roughly 500 per year (again, with lots of variation).

But that’s not the whole story. The researchers looked at the outbreaks themselves, and found that the number of tornadoes that occur in outbreaks is increasing. It’s going up by about 0.66 percent per year, from about 10 per outbreak in the 1950s to 15 today. That rise is statistically significant (that is, very unlikely to be from random chance).

In other words, we’re seeing more clustering of tornadoes in outbreaks. The researchers looked into this, and show that this is a real change in the nature of outbreaks, stating, “… the changes in the number of tornadoes per outbreak reflect changes in the physical environment.”

Something is going on with the climate that is causing outbreaks of tornadoes to be more severe. I’ll get back to that in a moment.

There’s another odd thing going on that’s a bit more subtle. The researchers looked at the variance of the number of tornadoes, too. That’s the number that shows how the number of tornadoes varies from outbreak to outbreak. If every outbreak had the exact same number of tornadoes, the variance would be 0. If some had very few tornadoes, and others had tons, then the variance would be high.

Weirdly, they found that over time, the variance itself is increasing. Comparing more recent years to the past, we’re seeing the same number of outbreaks, but we see more of them with more tornadoes each, as well as more of them with fewer. I know, that sounds odd. Think of it this way: In the past most outbreaks were close to average in the number of tornadoes they spawned, but now we see the distribution spread out; we see more extreme outbreaks as well as more with fewer tornadoes.

tornado statistics
The number of outbreaks per year is steady within statistical uncertainty (top), but the number of tornadoes per outbreak is on the rise (middle), and the variance is increasing rapidly.

Tippett, M. K. & Cohen J. E. (from the paper)

That’s disturbing. That means any given outbreak might fizzle and have few tornadoes … or it means there could be far more than average. These are high stakes, and we’re rolling the dice betting double or nothing. 

In general, seeing the variance in the number of tornadoes increase as the number of tornadoes per outbreaks increases is natural; it’s seen in other systems in biology and physics as well. But the variance is increasing four times faster than the mean number of tornadoes per outbreak, and that is unusual. According to the study authors, in most systems the variance increases roughly twice as fast.

Again, this implies very strongly that something is going on in the environment that is energizing these outbreaks.

The obvious something to consider is global warming. Storms use heat as fuel; it causes more evaporation of water and stronger convection, both of which are critical to generate storms. Increase the heat content of the atmosphere and that will have an effect on storm generation.

Scientifically, though, we cannot pin this new result on global warming just yet. But it’s certainly a prime suspect! More evidence is needed. As one of the researchers, Joel Cohen, put it:

Variance is growing faster than I would have guessed, and we don't know why it's so different from what we find elsewhere. If I were to speculate, I would say that certain physical drivers are accelerating, leading to increased energy in the atmosphere, which affects the forces behind tornadoes. Our results do not directly link climate change to the increasing severity of outbreaks, but we've found an indicator of change that's hard to explain otherwise.

This reminds me of the study showing an increase in top wind speed in hurricanes over time. The number of hurricanes isn’t increasing over time, but the top speeds of the most severe ones are getting faster. Global warming is certainly behind that, but the environment in which hurricanes grow is complex (for example, wind shear can curtail their growth). This sounds a lot like what we’re seeing here. The environment to grow a tornado is also complex, and global warming may stir that up further, so we see the same number of tornadoes overall, but outbreaks are getting worse.

I suspect this study will be cited by climate science deniers, and that they’ll look no farther than “the number of tornadoes hasn’t increased” (one thing you can always count on with deniers is that they will cherry-pick their data). But the total number is not the whole story. Climate is complex, and subtle. We can’t just stick our noses outside, say, “It’s cold outside” and deny what’s happening to our planet.

We have to learn to read the nuances, find the connections, understand the underlying principles. The good news is, that’s precisely what scientists are doing.

The bad news is, getting this through to the politicians is nearly impossible … except in November. It would be nice to see the climate science deniers in Congress have to weather that storm.

March 9 2016 9:00 AM

Does Pluto Have Clouds? Well …

The surprises from Pluto keep on coming. This time: Clouds.

Maybe.

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An article in New Scientist gives some of the details. Briefly, images of Pluto taken during the July 2015 close encounter by the New Horizons spacecraft show tantalizing hints of clouds over the surface. I’ll be honest: The evidence is interesting, but I’m not convinced.

Let me start off right away by saying I sent an inquiry about this to scientists with New Horizons, but they’re not ready to comment yet; obviously and understandably they want more time (and probably more images too) before issuing an official statement. I also could not find the images in the New Horizons raw images database, but there are thousands of images there, and I may have simply missed it (for the sake of discussion I'll assume it's real). Given all this as a caveat, in my opinion the New Scientist headline (“Exclusive Photos: Clouds Seen on Pluto for First Time”) is misleading in this regard (and they've been guilty of this sort of thing before). It’s not at all clear that’s what we’re seeing here. Possible, but not conclusive.

Pluto has an atmosphere, but it’s thin. I mean, really thin; atmospheric pressure at the surface is about 0.00001 (one one-hundred thousandth!) that of Earth’s. The air there is mostly nitrogen, which is oddly similar to the air here on Earth. However, temperatures on Pluto peak at roughly -220°C (-360° F), so don’t get too cozy comparing our climate with Pluto’s.

Still, there’s enough atmosphere to have effects we can see. For example, there are haze layers, a dozen of them or more, above the surface, seen best when New Horizons passed Pluto and saw its atmosphere backlit by the Sun (and yes, the sky there really is blue, for the same reason ours is).

And therein lies the issue. How do you distinguish between haze and clouds? The haze over Pluto is probably mostly made of carbon-based molecules, created by ultraviolet light from the distant Sun zapping simpler molecules in the air and on the surface. Are the “clouds” seen—if they are seen—similar to that, or a different phenomenon?

Haze tends to be widespread, and clouds more localized. But the haze isn’t distributed evenly, and could be thicker in some places than others. That makes it hard to distinguish from a cloud. The images of features on Pluto’s limb are hard to clarify.

clouds
More cloudlike features (circled).

NASA/JHUAPL/SwRI/New Scientist

However, there is a bright feature in one photo that seems to cut across both a brighter smooth and a darker bumpy region on the surface, which is interesting. If that were surface ice or something like that you wouldn’t expect it to overlap both regions. And it does look cloudlike … but looks can, as you might expect, be deceiving.

I’d love to see two shots taken a few minutes apart of the same area. That could settle it. The cloud may not move much in that time, but the motion of New Horizons, barreling past Pluto at 14 kilometers/second, might literally give us some perspective on it. As the spacecraft took images from different angles, a cloud well above the surface could be IDed due to its parallax.

Perhaps we’ll know more soon. Images are still being sent back to Earth from New Horizons (data rates from 5 billion kilometers are a tad on the slow side), so hopefully some will reveal more about these features.

So again, to be clear, we don’t know if these images show clouds on Pluto or not. However, I do hope this pans out. Clouds over Pluto! What a thought.

March 8 2016 12:00 PM

FRB UPDATE Part 1: Yeah, So About That Fast Radio Burst …

Recently, I wrote about an exciting astronomical discovery: The location and distance of a fast radio burst, or FRB, a tremendous cosmic flash of radio-wave energy. Quite a few of these have been detected, but they last literally for milliseconds, making it extremely difficult to nail down their position (and, hopefully, their distance).

In April 2015 an FRB went off, and some very fast work by astronomers nailed the position of it by finding the fading glow from the event. It was found to overlap an elliptical galaxy 9 billion light-years away. This was a huge step for astronomy!

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But now we may have to take a step back.

The FRB itself was real, to be clear. After the burst, the astronomers used a different radio telescope to scan that part of the sky looking for a signal that appeared to be fading away, indicating the dimming afterglow of the burst. They found one and showed it could be from the FRB.

But two astronomers have looked at the data and are not convinced an FRB afterglow was actually seen. In a paper that is online and will be submitted to the Astrophysical Journal Letters (and not yet peer reviewed), they suggest the astronomers looking for the afterglow were instead fooled by the elliptical galaxy itself.

All big galaxies have a supermassive black hole in their cores. If enough material is pouring into that black hole, it can form a disk outside the hole. This disk gets very hot, and glows. Galaxies like this are said to be active galaxies.

They’re notoriously variable, too, changing in brightness over relatively short periods of time. In the new report, the astronomers argue convincingly that this matches the data better than a fading FRB afterglow. The galaxy does appear to be active and variable, for one thing, which could easily explain the fading source seen. They also show that the way the light dimmed in the galaxy doesn’t match what is known about the way huge explosive events like this fade, again throwing some cold water on the claim.

I’ll note that this is interesting, even compelling, but not conclusive. More observations are needed, and given how important this finding is, I have no doubt they’ll be made. This is science in progress, folks, and things change as more eyeballs and brains chew over the data.

I have to note another issue, too: If the afterglow was not from the FRB, then the distance was not necessarily accurately determined. The FRB may have been in another galaxy entirely, or even in our own! And the distance was the key ingredient for the next bit of news: Half the “missing mass” of the Universe had been found. Using the way the radio signal from the FRB was shifted in wavelength/frequency, the original astronomers were able to estimate how much matter was between us and the FRB. If the distance isn’t known, then that measurement can’t be made. So until we know for sure where that FRB was in the Universe, we can’t say anything about the amount of material the signal passed through on its way to Earth.

Still, the news isn’t all bad. We’ve learned more stuff about FRBs in the past week as well … which I’ll cover on Part 2. Stay Tuned.

Tip o’ the dew shield to Nadia Drake.

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