Bad Astronomy
The entire universe in blog form

May 3 2016 2:24 PM

Jimmy Kimmel: Climate Hero

I have so much to say about it, but really, just watch this (note: lots of bleeped swearing for comedic effect, including from a kid, if that kind of thing offends you):

There are so many great lines in this segment, but I think my favorite is this:

You know how you know when climate change is real? When the hottest year on record is whatever year it currently is.

Yup. Well, that, plus when it keeps happening year after year. When we've had at least six months in a row of record-breaking heat, when the 16 hottest years since 1880 are all in the past 17 years, when 97 percent of climate scientists agree, and heck, when Sarah Palin thinks it’s wrong, then yes, we’re in serious trouble.

And yet the networks and media still think giving air to a climate change denier is a good idea. Incidentally, as Media Matters points out, there are more climate scientists in that Jimmy Kimmel video than were interviewed on ABC’s top news shows in all of 2015.

And this is why I still focus on the reality of climate change. Because too many people in charge of you getting your information won’t.

We can’t work on solutions until we get our politicians to admit the problem even exists. Remember: November is coming.

May 3 2016 11:45 AM

Three Earth-Size Planets Found Orbiting a Nearby Ultracool Star

The search for Earth-like planets continues, as astronomers scour the sky examining stars for telltale clues of orbiting worlds. Most of the exoplanets found are big, like Jupiter, because they’re the easiest to detect. But our technology has become better and more clever over the years, and smaller planets have been found, including many roughly the size of Earth.

That search took a cool turn this week … literally. A team of astronomers announced they have found not one but three Earth-size planets orbiting a red dwarf, a tiny and cool star just 40 light-years away!


This is very interesting for many reasons: This is the lowest mass full-fledged star ever seen to have planets, it’s relatively close by, and all three planets are (more or less) in the star’s “habitable zone,” where temperatures might—might—support the existence of liquid water on the planets’ surfaces.

The European Southern Observatory put together a nice video explaining this, so give it a view:

The planets were discovered using TRAPPIST (short for Transiting Planets and Planetesimals Small Telescope). This is a 60 cm (24”) telescope that takes images of a select group of 60 nearby red dwarf stars visible from the Southern Hemisphere. The team looks for dips in the stars’ light that are caused by any planets orbiting those stars periodically blocking their host star’s light; this is called the transit method, and most exoplanets have been discovered this way.

TRAPPIST found evidence of planets orbiting a star, called TRAPPIST-1, and follow-up observations were made with much larger telescopes. Three planets were found in total, which is remarkable all by itself. But it gets better.

TRAPPIST-1 is an M8 dwarf, only 0.08 times the mass of the Sun; just barely massive enough to fuse hydrogen into helium in its core. If it were much lower mass we wouldn’t call it a star at all (we’d say it’s a brown dwarf). Its surface temperature is only about 2,550 K—the Sun is literally more than twice as hot—so it's informally called an "ultracool" star. And it’s tiny, only about 0.11 times the diameter of the Sun. That’s roughly the same size as Jupiter!

Yet this teeny star sports at least three planets. Called TRAPPIST-1b, c, and d, the exoplanets were detected as they blocked a small fraction of the star’s light. The sizes of the planets were found by seeing just how much of the starlight they blocked. The best measurements indicate they are 1.1, 1.05, and 1.2 times the size of Earth. We don’t know their masses, but if they have the same composition as our home world—rock and metal—then their surface gravities wouldn’t be all that different than ours.

So they’re Earth-size. But are they Earth-like? That is, nearly the same temperature and composition as Earth?

We have no idea what these planets are made of. They could be rock, metal, watery, airless … with our current technology we don’t know how to determine that. Finding the masses of these planets would be extremely difficult, so we’re out of luck there.

But we can estimate their temperatures. The temperature of a planet depends on its distance from the star and that star’s temperature, of course, but also on how reflective the planet is; a more reflective planet will be cooler than a dark, absorptive one.

Each of the planets orbits ridiculously close to the star compared with the planets in our solar system. In order, they’re 1.7 million, 2.3 million, and 3.3 million–22 million kilometers from the star (the observations of the third planet, d, don’t constrain its distance very well, so there’s a range of possible distances). Mind you, Mercury is 58 million kilometers from the Sun, so all three of these planets would easily fit inside Mercury’s orbit, with a tens of millions of kilometers to spare.

But remember, the star is very cool, so even at those distance the planets aren’t as hot as you might think.

Assuming very dark planets, the inner two would be about 125° and 70° C, far too hot for life as we know it. The outer planet’s distance from the star wasn’t as well determined, but it would likely have a temperature somewhere from -160° - +10° C depending on its distance. The warmer end of that range is close to Earth’s average temperature!

Remember, that’s assuming dark planets. If they’re more like Earth (which reflects about 40 percent of the light that hits it), they’ll be cooler. If they’re reflective enough, the inner two planets might be more like Earth, too (but the outer planet would be a frozen ball of ice).

That part is more speculative; we have no idea how reflective they are. It’s possible, though I’d think unlikely, that all three planets are somewhat clement.

Again, we don’t know much about them; they might be airless, or have thick atmospheres of carbon dioxide, or some other noxious combination, so don’t start looking into real estate on them just yet. And even if they are Earth-like, 40 light-years is 400 trillion kilometers. That’s a fairly long road trip. It would take 450 million years to drive there at highway speeds. Better pack a lunch.

But don’t be disappointed. The amazing thing to remember here is that these planets exist at all. Even dinky red dwarf stars manage to make planets, including ones the same size as ours. That’s incredibly exciting.

Another reason this is so exciting is because of the host star. Cool red dwarfs are faint and hard to detect, making these observations somewhat difficult, but they also make up the most populous class of star in the galaxy. If they have planets in the same proportion as more massive, hotter stars do, then planets orbiting red dwarfs will outnumber planets orbiting all other types of stars combined. And here we found three Earth-size planets orbiting one nearby.

It’s impossible not to ask, how many planets like Earth exist in the galaxy? We’re not sure, but various methods have been used to estimate that number, and even conservatively their numbers must be in the billions. Billions. In our galaxy alone.

And our tech is getting better. In the coming years we’ll have telescopes able to dissect the light from such planets, looking for the Earth-like conditions: oxygen in the atmosphere, say, and a temperature more like ours. We’ve found a few candidates for Earth-like exoplanets, but nothing yet that we can point to and confidently say, “Earth 2.”

Nothing yet.

May 3 2016 9:00 AM

SpaceX Wants to Go to Mars—and It Actually Can

So, SpaceX wants to send a spaceship to Mars as early as 2018.

Wait. Seriously?


Yup. Last week, Elon Musk, CEO of SpaceX, made the startling announcement on Twitter:

He wrote, “Planning to send Dragon to Mars as soon as 2018. Red Dragons will inform overall Mars architecture, details to come.”

My very first thought when I read this was, “He thinks they can land a three-ton uncrewed Dragon capsule on Mars in the next couple of years? Something heavier than any other payload ever dropped on Mars, and from a company that hasn’t even sent anything anywhere near that far?”

Then I mulled it over for a moment. To my own astonishment, I realized, “Huh. Yeah. In fact they can do this.”

Now look, it won’t be easy, not by a long shot. But Musk’s claim isn’t out of the blue—SpaceX has been working toward this for years. What it comes down to is key pieces of technology still untested in flight but currently being developed, as well as SpaceX maintaining its current launch schedule.

But in the end, it’s feasible that in a few years, a Dragon capsule will sit on the surface of Mars*.

First, let’s take a look at the spaceship that would do the actual landing. The Dragon 2 is an upgraded version of the Dragon capsule currently being used to send supplies up to the International Space Station. Dragon V1 has been sent to space and back successfully many times already.

The Dragon 2 upgrades are extensive, including adding the ability to carry seven astronauts to ISS. But as far as a Mars trip goes, the most important upgrade is the addition of SuperDraco thrusters; four sets of two engines around the outside edge of the capsule. These are powerful, designed to be able to rapidly carry away the capsule in case of rocket failure during flight. But they’re also critical for landing on Mars.

The atmosphere of Mars is very thin, but it’s there. You can’t ignore it if you want to land on the planet; at interplanetary speeds a capsule will burn up as it plows through the air if steps aren’t taken. Sending smaller probes to the surface (like early landers and rovers) used a combination of aerobraking (drag on the spacecraft to slow it down), parachutes, and in the case of Curiosity a rocket crane that slowed to a hover over the surface to deploy the rover.

Dragon at Mars
Artists's illustration of a Dragon V2 aerobraking through the atmosphere of Mars.


A Dragon 2 is too big for any of these options; a parachute big enough to slow it down would be shredded under those stresses. Instead, the plan is to use an advanced heat shield on the bottom to slow it down enough that the SuperDracos can take over, landing the Dragon 2 safely on the surface.

This has never been done before, but SpaceX has been slowly learning how to do it, and you’ve probably seen it happen: the return of the Falcon 9 first stage boosters. To return to Earth, the booster flips around and does a “boostback burn” to slow its motion. Even though there have been many attempts to land the booster, and only two successes, that doesn’t mean all was lost. The data retrieved from all the attempts are precious steps toward understanding how to do a “supersonic retropropulsion” burn to slow a vehicle in air … under conditions very similar to the conditions a Dragon capsule will face entering the Martian atmosphere.

That’s no coincidence. Every booster return is like a real-life simulation of a Mars landing. So SpaceX has been amassing quite a bit of information on how to do this.

In fact, they’ve been sharing that data with NASA in exchange for technical advice on deep space planning and support. No money has changed hands, just the trade of information. NASA has also pledged communications and telemetry support using their Deep Space Network in exchange for the data from an uncrewed mission to Mars using the Dragon 2.

So it looks like the Dragon 2 can get down to the surface of Mars from space. But how does SpaceX plan to get it to Mars in the first place?

Right now, the company has contracts with NASA and other groups for launches using its Falcon 9, their workhorse two-stage rocket. The Falcon 9 is a capable booster. There have been 23 launches of Falcon 9 so far, with 22 successes and one failure (that last tracked to a faulty support strut inside the booster; those have been upgraded since that time).

It can even be used to send a payload to Mars, as long as that payload has a mass less than about 4,000 kilograms (8,800 pounds, or four tons). That’s not bad, but not nearly enough to get a Dragon 2 capsule down to the surface—a dry (unfueled) Dragon 2 has a mass of 6,400 kilos.

Clearly, they’ll need a bigger rocket.

Falcon Heavy launch
Illustration of a Falcon Heavy launch, due to become real later this year.


Enter the Falcon Heavy: This beast is essentially three Falcon 9 first stage boosters strapped together, providing a much larger payload capability. It can hypothetically send up to 13,600 kilograms to Mars. That easily covers the mass of the capsule and fuel, and would still have a few tons of capacity left for scientific instruments.

So, great. Use the Falcon Heavy to throw a Dragon 2 at Mars, and use the knowledge gained over the past few years to drop the capsule safely to the surface.

Falcon 9 booster
The trajectory of a Falcon 9 booster from launch to landing. Click to vonbraunenate.


Except, hang on. SpaceX isn’t quite there yet. While all of this makes sense on paper, they haven’t actually tested all this hardware in flight. The Falcon Heavy has never been flown. But at the Satellite 2016 conference held in March, Gwynne Shotwell, president of SpaceX, said that the first Falcon Heavy flight may be late this year, possibly in November. That launch, from Florida, is also planned to include recovery of all three first stage boosters, two on land and one on a floating barge in the Atlantic (this is basically a three-fold test of the single booster relanding after launch). Over the next couple of years there will be more flights as well, which will hopefully work out the bugs and build confidence in the rocket.

Of course, the Dragon 2 hasn’t flown yet either. However, it has been tested extensively on the ground, including a “pad abort test,” a NASA requirement for crew-rated vehicles to make sure it can take astronauts away to safety if there’s a launch emergency:

The capsule should be tested in flight this year as well. SpaceX has said it wants to send a crew to space on the Dragon 2 in the next year or so, and already has an order from NASA to send a crew to ISS (though no date has been specified, 2018 is a decent guess).

So, SpaceX being able to go to Mars depends critically on flight-testing both the rocket and the capsule lander. But both of those tests are in the works and may happen quite soon. And, if they test successfully, SpaceX will turn its eyes to Mars.

Which brings me back to Musk’s tweet. Red Dragon is the name of the mission to send a Dragon 2 to Mars. The information learned from that mission will then be used to figure out how to send larger and more ambitious missions.

And make no mistake, Musk is determined to put people on Mars; I interviewed him on this topic in 2015, and he stated plainly, “Humans need to be a multiplanet species.”

We’re not there yet. SpaceX isn’t there yet either; quite a lot rests on the successful tests of Falcon Heavy and Dragon 2—and more, for that matter. Details of the actual mission profile (for example, what kinds of potential payloads it might carry) haven’t been released yet; the company plans on discussing all this at the International Astronautical Congress in Mexico this September. Realistically, the 2018 goal may get pushed back a year or two due to inevitable delays; there’s a long way to go and a lot to do before this mission literally gets off the ground. But SpaceX is very serious about it.

And, in my opinion, it's quite capable of accomplishing it.

Post script: My colleague Eric Berger wrote two excellent articles on this topic: “Can SpaceX Really Land on Mars? Absolutely, Says an Engineer Who Would Know” and “Why Landing a Flying, Fire-Breathing Red Dragon on Mars Is Huge.” You’ll find a lot more details there. I’ll note we agree that SpaceX can in fact achieve this goal.

* Correction, May 3, 2016: I originally wrote that SpaceX would land a craft on Mars as soon as 2018, but that's not precisely true; they plan on sending one to Mars then. The difference is travel time; it takes about six months to get to Mars from Earth. I updated my wording to reflect that. Also, I wrote that SpaceX hadn't sent anything beyond low Earth orbit, but they did deploy DSCOVR which is in the Earth-Sun L1 point, 1.5 million km from Earth.

Update, May 3, 2016: Originally called the Dragon V2, SpaceX now refers to it as simply Dragon 2. This post has been udated to reflect that.

May 2 2016 12:00 PM

A Galaxy Hidden in Plain Sight

There are times when I glance at an image and right away I know something is peculiar about it. Such was the case for UGC 477, the very lovely but decidedly weird galaxy pictured above.

The image was taken using Hubble Space Telescope, and only shows two colors; usually these images are the more natural-looking three-color red/green/blue composites. In this case, what you see as blue is actually at a wavelength of 475 nanometers (teal or blue-green to our eyes), and red is 775 nanometers, just at or outside the reddest end of what we can see (it’s fair to call this near infrared). The blue highlights the young, hot, massive stars and red the old, low-mass, cooler stars in the galaxy.


To my eye the galaxy looks, well, raggedy. Most spirals seen edge on are smoother, or if they’re clumpy, the clumps have a pattern to them. This one looks like it just woke up in the morning and hasn’t had its coffee yet. It’s messy, disorganized.

It turns out that’s really the case. But it’s weirder than that: UGC 477 is what we call a low surface brightness galaxy, or LSB galaxy. As the name implies, these are pretty faint galaxies, sometimes actually much fainter than the night sky surrounding them. Our own galaxy is a disk, and would easily swamp the light from UGC 477 if the latter weren’t located well above our own galaxy’s plane, where stars and dust are less populous.

The galaxy is about as big as our Milky Way, 100,000 or so light-years across, and it’s 120 million light-years away. At that distance it should be bright and fairly obvious, but instead is much dimmer than you’d expect. This may be due to a lack of star formation in it; although you can see some bluish clumps where stars are being born, most spirals have big, splashy nurseries in them. UGC 477 seems to have a much larger gas to star ratio than other galaxies, unused material from which to make stars.

Malin 1
Malin 1 is just ridiculously huge. Here it is compared with a drawing of our Milky Way. That's to scale, folks.

Galaz et al., 2016 & NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

LSB galaxies may be isolated from other galaxies, in regions of space called voids. This means they don’t suffer collisions as much, which is one way to build a giant galaxy, and to crash gas clouds together so they can form stars. It’s something of a mystery as to why LSBs can be so big then, though. Malin 1, another LSB galaxy, is a freaking monster, five times or more bigger than our Milky Way! Yet it’s far fainter than you’d expect for such a beast.

Interestingly, LSB galaxies appear to be dominated by dark matter, making them good test beds for models on how this affects galaxy formation, growth, and shape over time. We actually don’t know as much about these galaxies as we do normal ones, since they’re so dim they were only discovered recently, and they’re difficult to observe. Hubble is ideal for this kind of study, though, at least for nearby ones—but even its mirror is too small to collect enough light from ones substantially farther away.

But as telescopes get bigger, and our detectors more sensitive, we’ll learn a lot more about these odd denizens of deep space. What were they like when the Universe was young? Pretty much as they are now, or were they substantively different? Hopefully soon we’ll know, and put into place have yet another piece of the puzzle that is our Universe.

May 2 2016 9:30 AM

The Earth Is Getting Greener … but That’s Not a Good Sign

A new study just published in the journal Nature Climate Change reached an interesting, if not totally surprising, conclusion: The Earth has become significantly greener over the past 33 years.

The main reason? All the extra carbon dioxide we humans dump into the air.


Let me be clear right away: This is a kinda sorta good thing, but don’t celebrate the positive aspect of climate change just yet. The effect almost certainly won’t last, and this small positive is completely buried under a long, long list of negatives.

The research used satellites to examine vegetation growth over time, assuming that the extra green is coming from leaves on plants and trees. Using a computer model to estimate leaf growth, they find the extra greening is equivalent to adding about 18 million square kilometers of vegetated land to the globe, more than twice the area of the mainland U.S. That’s pretty astonishing.

greening Earth
Map showing vegetation across the globe.

Myneni et al.

The growth is due to added CO2 in the air. Plants use sunlight for energy and convert CO2 (plus water) into sugar, which is stored for food. In a naïve sense, more CO2 means more food for plants (this is called carbon dioxide fertilization), so there’s more growth.

The good news, such as it is, is that this means plants are able to soak up more carbon from the atmosphere. The bad news is, it’s not nearly enough. This is made clear by a graph showing atmospheric carbon dioxide content, as measured at the Mauna Loa Observatory in Hawaii:

CO2 levels
Carbon dioxide levels measured at the Mauna Loa Observatory. The increase is accelerating.

Scripps Institute of Oceanography

As you can see, the amount of CO2 in the air is still increasing, even with this extra vegetation. Worse, look at the increase from 1980 (roughly the start of the new study’s time range) to 1995. If you extend that slope, you’ll see that the increase has increased since 1995; in other words, we’re putting out even more CO2 per year than we did 35 years ago.

All that extra plant growth can’t keep up with the 40 billion tons of carbon dioxide humans dump into the atmosphere every year.

Incidentally, some of that greening is in the Arctic. That place is usually covered with snow and ice, except warmer temperatures have been causing it to melt away. That’s not a place we want to see green. White would be way better.

Of course, this hasn’t stopped the deniers, who tend to ignore inconvenient facts like that, and instead just tout how the Earth getting greener must be a good thing. World News Daily and the Cato Institute were two sources I found pretty easily making this fallacious claim. It’s cherry-picking in the worst sort of way, but then deniers have been making this ridiculous claim for a long time now.

What I find funny is that in the press release, one of the authors of the research pre-emptively smacks down the deniers [emphasis mine]:

The beneficial aspect of CO2 fertilization in promoting plant growth has been used by contrarians, notably Lord Ridley (hereditary peer in the UK House of Lords) and Mr. Rupert Murdoch (owner of several news outlets), to argue against cuts in carbon emissions to mitigate climate change, similar to those agreed at the 21st Conference of Parties (COP) meeting in Paris last year under the UN Framework on Climate Change (UNFCCC). "The fallacy of the contrarian argument is two-fold. First, the many negative aspects of climate change, namely global warming, rising sea levels, melting glaciers and sea ice, more severe tropical storms, etc. are not acknowledged. Second, studies have shown that plants acclimatize, or adjust, to rising CO2 concentration and the fertilization effect diminishes over time," says co-author Dr. Philippe Ciais, Associate Director of the Laboratory of Climate and Environmental Sciences, Gif-suvYvette, France and Contributing Lead Author of the Carbon Chapter for the recent IPCC Assessment Report 5.

Of course, deniers gonna deny. Using this study to say that climate change is good is like getting in a massive car accident and being happy you don't have to vacuum out the car anymore.

But hey, if you’re willing to ignore rising sea levels, more extreme weather, melting polar ice, deoxygenation of the oceans, droughts, floods, acidification of the oceans and coral bleaching, more heat waves, and the displacement of potentially hundreds of millions of people, then y’know, a little more green in your life is just great!

Enjoy it while it lasts.

May 1 2016 8:45 AM

360° View of the SpaceX Booster Ocean Landing

This is just too cool. Click in the video and drag it around. Hint: At the beginning, tilt up.

The Falcon 9 booster landing on April 8 was pretty amazing. It was windy out, as you can see from the video; once the booster made contact, it slid a few meters. A while later, some SpaceX crew went out to the barge to weld it to the surface so it wouldn’t tip over if the seas got rougher. Bear in mind, that booster is more than 40 meters tall. That’s taller than a 12-story building.


The video is neat. Being able to move it around like that is a relatively new thing for YouTube videos; we exploited it for an interactive Crash Course video tour of the solar system. Go play with that if you’d like. The narrator is a close friend of mine.

The next Falcon 9 launch (carrying a Japanese communication satellite) is scheduled for Thursday, with a launch window opening at 05:22 UTC (to be clear, that's 01:22 Eastern U.S. time, or 22:22 Pacific time on Wednesday). A booster landing at sea will again be attempted, but it’ll be much tougher: The launch is to put the satellite in a geosynchronous orbit, which means the booster will be moving horizontally much faster than it did for the previous landing, and will have less fuel to slow and maneuver to the barge. It’s likely not to be successful, but we’ll see.

April 30 2016 9:15 AM

No, Saturn Won’t Be Huge in the Sky on May 1

Another day, another weird Facebook astronomy hoax.

The photo with the caption above have been spread around Facebook quite a bit the past few days; it shows Saturn looming huge in the sky over a city, with the annotation, “On 5/1/16 Saturn will be the closest it ever has been to Earth. It will look like this.”


I got a few notes from readers on Twitter about it. Unlike a lot of other wrong but possibly sincere memes, this one is clearly a hoax. It’s just silly and wrong on every level, so it couldn’t possibly have just been an honest mistake. It’s a joke.

What’s wrong with it? Well, two main things: Saturn isn’t the closest it’s ever been on May 1 (its closest approach to Earth this year is in June), and Saturn can’t get big enough to look like that, ever. Which is a good thing.

The closest Saturn ever gets to Earth is about 1.2 billion kilometers. That’s something of a hike. Saturn is big—120,000 kilometers in diameter, not including the rings, which are 250,000 kilometers across—but from that distance it’s not even big enough to appear as a disk to the eye. Through binoculars you can see the rings as a tiny ellipse, and through a smallish ‘scope you can more clearly see the planet as a disk and the rings circling it.

To be that big, Saturn would have to get as close to us as our Moon! In fact, that’s where the image comes from. It was easy enough to track down; a reverse image search on Google showed it’s from a Russian video intended to show what the sky would look like if the Moon were replaced with the other planets in our solar system:

It’s a fanciful idea, and as far as I can tell first done by my pal Ron Miller, a space artist, in 2012, and again by videographer Yeti Dynamics in 2013. In fact, Yeti Dynamics went ever further and created a wonderful video showing what it would look like if Saturn were actually passing the Earth in the solar system:

As I wrote at the time, that would be the most amazing sight ever witnessed … and also the last thing you’d see. From that distance, Saturn’s gravity would inflict monstrous tidal forces on the Earth, causing apocalyptic floods, massive earthquakes, and generally dealing out death on a global scale.

As much as I love looking at Saturn, I’m pretty happy it’s more than a billion klicks away.

So where is Saturn right now? It’s currently about 1.37 billion kilometers away, where it always is. It rises around 10:30 p.m. local time, and shines at a magnitude of about 0.2, making it one of the brightest objects in the sky. In fact, it’s very much worth going out and taking a look around midnight; very close to it in the sky is the much brighter and much oranger Mars, and the bright red supergiant star Antares, the heart of Scorpius. Face south and look low to the horizon for the trio; your outstretched fist can cover all three.

Saturn by Damian Peach
Saturn, taken by master astrophotographer Damian Peach with a 35.6 cm telescope on March 18.

Damian Peach

And if you have a telescope, well then what are you waiting for? Saturn is one of the most magnificent objects in the sky. Patience pays off, too: In early June it will be at opposition, opposite the Sun in the sky, which means it rises at sunset and is up all night. As an added bonus, that’s when it truly is closest to the Earth, and appears as big as it can. But then, that means it’ll be 0.3 arcminutes across: Only 1/100th the width of the Moon in the sky.

But through a telescope, it’s glorious. So forget the dumb Facebook hoaxes, and go see the real Universe for yourself. It’s way, way better. 

April 29 2016 9:00 AM

The Warped Path to Understanding the Universe

The Universe is a bit bent.

You’d think that light would travel in straight lines, going directly from point A to point B. But it’s more complicated than that. Space is curved, warped, distorted by the matter lodged within it. It’s hard for our puny three-dimensionally adapted brains to wrap themselves around (so to speak), but what we think of as space is actually a framework that can be bent.


Mass does that bending, and we perceive that bending as gravity.

But we can see the effects of this bending, too. Like a car following a curve in the road, light follows the gravitationally induced curving of space. We poetically call this effect “gravitational lensing,” because a lens bends light as well. 

Sometimes the curve in space is profound, like when a black hole makes a warp so severe it’s almost a puncture in the fabric of reality. The path a beam of light takes can be whipped around quite viciously—we call this strong lensing—or even plunge down into the black hole, never to return. Clusters of galaxies can do this as well, warping light from even more distant galaxies into bizarre shapes.

Other times that curve is more gentle, when the mass is more spread out. Individual galaxies and some galaxy clusters are like that. Instead of an obvious distortion in the direction light takes, it’s subtler, only marginally changing the light’s path.

Although harder to detect, this weak lensing can tell us a lot about the mass doing the bending of space. And that’s why astronomers used Hubble to take that lovely image of the galaxy PGC 54493 seen above.

zoom in on galaxy
A closer look at PGC 54493. Lovely, isn't it?

ESA/Hubble & NASA, Acknowledgement: Judy Schmidt

That galaxy dominates the view, our eyes drawn to magnificent spiral arms, the bar-shaped distribution of stars in its center, the blue patches where massive stars are being born by the thousands. But it’s not the most important thing in this image.

Look around it. See all the smaller, fainter galaxies? PGC 54493 is perhaps 500 million light-years or so away, but these other galaxies are much farther. The light we see from them was emitted when the Universe was far younger, and has traversed billions of light-years of space to reach us.

On that trip, this light passed near PGC 54493, traveling through the region of space subtly distorted by the galaxy’s mass. The shapes of these distant galaxies thus get distorted, too, the amount of change in their shapes determined by the amount of mass in the big spiral galaxy bending space. It’s difficult to determine that for any individual faint galaxy, but if you observe enough of them, you can show statistically how much they’re warped, and therefore where the mass of the intervening galaxy lies and how much there is.

That is critical. We know that normal matter—the kind of matter that makes up you, me, the computer you read this on, and essentially every visible object in the Universe—is in the minority. Dominating the amount of matter in the cosmos is a mysterious form of it that we cannot see, but which has mass, and therefore gravity. Dark matter can’t be observed directly, but its gravity warps space, and that distorts the light from those distant galaxies, and that we can indeed measure.

Astronomers have been mapping dark matter in this way for many years; perhaps most famously in the Pandora Cluster, which showed just how dark matter in clusters of galaxies can affect the light from more distant galaxies. They continue to observe other clusters to make even more maps of the distribution of dark matter in the Universe, and that’s why PGC 54493 was the target of these observations.

Although bright and beautiful, it’s the dark reach of that galaxy that concerns us, invisible matter making invisible bends in space, distorting more distant galaxies in almost, but not quite, invisible ways.

Sometimes the Universe is obvious, ostentatious, perhaps even gaudy. But other times it whispers, hints at us to follow the rules of math and science that shape it, and in so many cases it is following that path—distorted and subtle as it may be—that leads to seeing its underlying structures.

April 28 2016 9:15 AM

Climate Change Is Strangling Our Oceans

As our globe heats up, the effects of those rising temperatures are complex and varied.

Overall, we call these effects “climate change,” but that’s an umbrella phrase that covers a vast number of changes. Melting polar ice, glacial melt, changing weather patterns, more extreme weather, rising sea levels, ocean acidification … these are the topics we hear about quite a bit. But there are other changes going on, and these are every bit as much a cause for concern.


For example, global warming is strangling our oceans.

By that I mean that oxygen levels in the oceans are affected by global warming, too. This occurs in two general ways. One is that warmer water has a harder time holding on to dissolved gases—that’s a basic law of chemistry. So oxygen levels drop as water warms. The other is that as surface waters warm, they expand, and mix less with deeper water. Surface water gets most of its oxygen from phytoplankton that breathe it out. That water sinks and mixes with deeper water. As the water becomes more stratified due to global warming, less of that oxygenated water gets to lower depths.

The question then becomes, when will we start to see the effects of global warming on the oceans’ oxygen content? Like so many other aspects of climate change, we’re seeing that deoxygenation due to human-generated global warming occurring now. Not sometime in the distant future. Now.

That’s the result of a new study done by a team of scientists led by Matthew Long, an oceanographer at the National Center for Atmospheric Research in Boulder, Colorado. He and his fellow scientists used a sophisticated computer model that calculates the amount of oxygen dissolved in the oceans over the globe and with ocean depth. The model accounts for a great number of factors, including air temperatures, water temperatures, layers in the water, sea ice, and much more.

Global warming changes the air temperature, which affects the model. In the past, global warming was small, and natural variations in the environment changed the oxygen levels far more than human-made warming. But, as the world warms more and more, the effect of warming increases, and at some point becomes noticeable over the natural variations.

Think of it this way: Imagine being in a loud room, with many people talking, and someone nearby whispers at you. You can’t hear them at first over the ambient noise, but if they keep speaking more and more loudly, at some point you can distinguish their voice from the crowd.

The scientists running the model wanted to know when they could hear the voice of warming over the babble of the natural variations. They ran the model many times, varying the air temperature a small amount with each run. This gave them a range of outcomes that they could compare to physical measurements; that gave them a check to make sure they had real-world testable outcomes.

ocean oxygen level map
A map showing when the signal from human-caused global warming emerges from the noise of natural variability. Blues are where it's already being seen; by 2040 all colored regions are affected. Gray shows no predicted signal by the year 2100.

Matthew Long/NCAR

What they found is sobering. Deoxygenation due to human-made global warming is already detectable in the southern Indian Ocean, and in some regions in the eastern tropical Pacific and Atlantic. By 2030 to 2040—two decades from now—they expect to see more and more widespread deoxygenation over the globe. By the year 2100 (which is how far into the future they ran the models) a significant fraction of the global oceans will see some deoxygenation due to human activity.

This is, obviously, bad. The amount of deoxygenation may not be very much, just a drop of a few percent. But as we learned with increasing carbon dioxide levels in the atmosphere, and rising temperatures, it doesn’t take much change to destabilize a system.

The worst effects will come from areas already low in oxygen, called hypoxic zones, where the levels can be as much as 70–90 percent lower than average, and in suboxic zones, where it’s even lower. In those regions, a few percent drop can mean the difference between life barely holding on, and death.

Even when the change isn’t so dramatic, it can be devastating. You might think of the ocean as one big fish tank, but it’s actually incredibly diverse, depending on water temperatures, currents, pressure, and more. Changes in oxygen levels in the water reduce marine life habitats, stressing the inhabitants there. Changes in regional oxygen levels have caused migrations of fish, and even massive die-offs. Besides the effect on the life there, this has an impact on human activity including fishing, on which many countries depend.

Mind you, about half the oxygen we breathe comes from ocean phytoplankton. Messing with their habitat is like setting fire to your own house. Which is pretty much what we’re doing.

So you can add this to the list of deleterious effects of global warming to our planet. And don’t forget that the past six months have all had record-breaking high temperatures, with many scientists already expecting 2016 to be the hottest year on record globally, and carbon dioxide levels still rising.

Global warming is our future, but it’s also our present. It’s now. Once again, Americans, I implore you to consider this, what is perhaps the greatest long-term threat facing humanity, when you go to the voting booth in November. And for the rest of the world, know that most of us here in the U.S. are aware of the problem and doing our best to urge our leaders to take action as well. We can minimize the damage of global warming, but first we have to make sure our government is facing reality.

April 27 2016 8:30 AM

A Moon for Makemake

Well now, this is very cool: Astronomers have just announced that Makemake has a moon!

Makemake (pronounced MAH-kay-mah-kay; it’s named after a Rapa Nui god who created humanity) is a Kuiper Belt object (or KBO), a large icy world orbiting the Sun way out past Neptune. It’s what’s called a “classical” KBO, because its orbit is far enough from Neptune’s that it can orbit the Sun stably for billions of years (Pluto actually gets closer to the Sun than Neptune does, but their orbits are timed such that they never get very close together). At 1,430 kilometers across, it’s the biggest known classical KBO, and the third biggest such body known past Neptune. Only Pluto and Eris are bigger.


We know quite a bit about Makemake from previous observations. It takes about 7.77 hours to rotate once, and must have a very reflective surface. Spectra show it has a lot of frozen methane on it, too, more than any other object out past Neptune. Its orbit is elliptical, taking it as close to the Sun as 5.8 billion kilometers and as far as 7.9 billion kilometers out. Right now it’s almost at aphelion, the point in its orbit when it’s farthest from the Sun.

It’s been observed many times, but until now no moon had been found. The discovery was made using Hubble Space Telescope, which observed Makemake exactly one year ago, on April 27, 2015. The moon—which for now has the cumbersome designation S/2015 (136472) 1—was seen very close to the KBO, almost lost in its glare.

That may be why it hasn’t been seen before. For one thing, it’s much fainter than Makemake, making it hard to detect. The astronomers who discovered it also propose that we may be seeing its orbit edge-on, which means it spends much of its time too close to Makemake to easily detect from Earth. From its brightness it's probably very roughly 200 kilometers in diameter, so seeing it at all is remarkable, especially from more than 7 billion kilometers away!

discovery images
The raw, unprocessed discovery images showing Makemake and its moon (arrowed in the first panel). The streaks and dots are cosmic rays, different in every frame, but the moon persists.

Parker, et al.

The observations were split into two “visits”; one on April 27 and the next on April 29. The moon was seen in the first visit but not the second, meaning it was too close to Makemake to see in the second set. Each visit consisted of six long exposures, and the moon was seen in all six images on the first visit.

The problem is the time between the first and last images in the first visit was only a couple of hours, which was not enough to show any motion of the moon. That means the orbit isn’t well-known. The best the astronomers could do was say that the orbital distance is at least 21,000 kilometers, but may be as much as 300,000! For comparison, the Moon orbits the Earth at a distance of about 380,000 kilometers. The moon orbits Makemake with a period somewhere between 12 and 660 days.

Those are pretty wide ranges. And that’s too bad, because the orbit of a moon is really critical: It tells you the mass of the object it orbits. Gravity depends on mass of the primary object and the distance to the moon, so if the orbital period of S/2015 (136472) 1 had been measured, the mass of Makemake could have been found.

What makes this even more frustrating is that we know how big Makemake is, because in 2011 it passed directly in front of a star as seen from Earth; the length of time it blocked the star combined with its known orbital speed yielded the diameter of 1,430 kilometers. With that number, plus the mass, its density could be determined, and that gives a huge clue about what it’s made of. Rock is denser than ice, for example, so just knowing Makemake’s density would constrain its composition.

However, the good news is that now that we know the moon exists, more observations can be made. It may take Hubble to see it once again—Hubble’s really good at spotting faint things near bright things—but it can be done. And if carefully planned (which it will be), the moon’s orbital period and shape can be found.

There are some interesting implications of this, too. Earlier infrared observations of Makemake indicated the surface had at least two different materials on it, which had different thermal properties (darker material, for example, gets warmer than more reflective stuff). If that were the case, though, the brightness of Makemake should change enough to measure as it spins, but no such change was seen.

The moon may solve this problem! If it’s darker than Makemake, then that would throw off the infrared observations. Those telescopes couldn’t separate the moon and the KBO, so they merged together, confusing the interpretation.

Pluto and Charon
Pluto and its much darker moon Charon (relative sizes to scale, relative distances not to scale).


I find that very interesting indeed. As you may remember from last year, Charon, Pluto’s moon, is much darker than Pluto as well. If this new moon is indeed dark, that might indicate a similar origin story. Future observations with the James Webb Space Telescope, due to launch in 2018, may help figure this all out; it has the keen vision in the infrared to separate the two objects and determine how reflective the moon is.

Just the fact that the moon exists is interesting, too. Pluto has a moon, as does Eris and Haumea (another large trans-Neptunian object a bit smaller than Makemake). Are they ubiquitous? Two other such objects, Sedna and 2007 OR10*, have no known moons. Perhaps we just haven’t seen them because they’re too close to their primaries. Clearly, more and deeper observations are needed.

And let’s not lose sight of the more general nature of this: We’re still learning basic information about our solar system! Finding a moon like this gives precious insight into what the outskirts of our celestial neighborhood are like, a region that is terribly far away and dark, and very difficult to explore. Each discovery about it is a clue to how it came to be, how it changed over time, and why it looks the way it does now.

All of this tells us more about our existence, and informs us about our own world. A cold and distant moon orbiting a smallish ice ball may not seem like much, but it’s another piece of the puzzle, one worth investigating and understanding.

* Correction, April 27, 2016: I orginally wrote that object's name as 2010 OR10.