Bad Astronomy
The entire universe in blog form

Aug. 29 2016 9:00 AM

Grasping Climate Change

These are facts: Global warming is real, and almost entirely caused by human activities. Natural variability in temperature is minor compared with what we’re doing. This increase in temperature is causing the climate to change, in many ways that are not only predictable but actually observed. This in turn is causing other effects, like Arctic and Antarctic ice loss, sea level rise, coral bleaching, more extreme weather, and much, much more.

Again: Those are facts. The vast majority of scientists who have dedicated their lives to studying the climate agree on this.

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And yet a small but vocal minority of people won’t accept that. Why? Some are sponsored by fossil fuel companies, the same ones who for decades have pumped money into disinformation campaigns, as well as politicians’ pockets. And of course some are ideologically inclined to dismiss science, or progressive politics (which has nothing to do with the science).

Still, some people honestly question the existence of global warming and its effects on the climate. Given all these facts, why do they do so?

Part of the problem—outside the general atmosphere of denial the media helps promote—is the scope and scale of climate change itself coupled with our puny brains trying to deal with it.

We humans have a miserable sense of scale. We see what’s immediately around us, and have difficulty extrapolating to the greater world. Even those of us who travel around the country and the world can still easily fail to grasp the scale of humanity’s presence. There are more than 7 billion of us! And billions of cars, millions of buildings, billions of houses, all of which use up energy and contribute to the emission of carbon dioxide.

But we can’t hold those numbers in our hands (why do you think we use the phrase “grasping a situation”?) and so our impact seems like it must be small.

But then look at the other side of the equation. The Earth is huge! So huge, again we can’t grasp it. Five hundred million square kilometers of surface area! Five quadrillion tons of air in the atmosphere! A hurricane is an unbelievable event, releasing as much energy as tens of thousands of nuclear bombs going off over a few days!

How could we possibly have an effect on a planet with scales like that?

And the answer is that we do have an effect, and it is small. But it never stops.

That can be hard to swallow, because time is long and our perception narrow. We have firm memories of recent experiences, fuzzier ones going further into the past, and dim ones going back decades.

And that is the true evil of climate change. It’s slow, and patient. It’s everywhere, but takes its time. It operates every day, but its effects don’t manifest for decades. Weather changes every day, every hour, and that noise washes out the signal of climate change.

Unless, that is, we too are patient, and keep our eyes on the long view. When we do, we see the trend, not the bumps and wiggles. This short, one-minute video frames it the best way I have ever seen: as a person walking a dog:

If we watch the trend, and not the wiggles, we see the impact of humanity on our planet. The temperature trend is actually quite clear now. And that trend is up.

As it will continue to be, unless we act. We put 40 billion tons of carbon dioxide into the air every year, and this is the root cause of all this. We can cut that back significantly if we decide to. It’s not easy, and it won’t be without cost, but it can be done. The alternative is to have the effects of climate change get more and more obvious, on shorter and shorter timescales.

What can we do? We can charge companies that put carbon into the air. We can rely on more renewable energies (solar and wind, of course, but we can also reopen the books on nuclear).

And the most important thing? We can vote.

The Republican Party has made it clear how they feel about climate change. Their official platform only mentions it a few times, and that’s to dismiss it, and their presidential candidate, Donald Trump, calls it a “hoax” and chose a denier as his energy consultant and another as his vice presidential pick. The Democratic Party platform talks about it much more realistically, categorizing it as a threat to our nation and our world. I have issues with Hillary Clinton’s climate change strategy, but those are minor to the point of nonexistent compared with the flat-out denial and active promotion of fossil fuels from the GOP. Accepting there’s a problem is step one, and even a slow approach is better than fueling the fire. Literally.

Look up your senators, your representative. Find out where they stand on this issue. Contact them, write a letter (that’s the most effective means of getting your voice heard), supporting them if they understand the reality of climate change, or briefly and politely letting them know how you feel if they don’t.

And if you hear someone denying climate change, may I humbly suggest searching this very blog for more info with which to give them facts, and links to more information? Other good sources include NASA’s climate site, NOAA’s climate site, Skeptical Science, DesmogBlog, RealClimate, and Climate Central.

It’s not too late. If we choose wisely, that is.

Aug. 27 2016 9:00 AM

Goaturday

Is Caturday still a thing? I don’t care, because it’s now Goaturday.

That is my goat, Jack Burton.* He is one of four goats we have chez BA, the others being Sam, Batman, and Clayton Forrester. They are all fun and cute and adorable, and you can find lots more pictures of them on my Instagram feed (for all my social media links, go to about.me). For example, here is video of me feeding them apples, and here is Jack yelling, “What what?”

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I’m on travel right now and my wife sent me this photo of Jack to remind me of some of what I’m away from. It makes me homesick, but it also makes me smile that he’s such a dork, chewing with his mouth open. They’re all dorks and I miss them. But look at him! Look!

When I get home I will scratch them all on their heads and pat their bellies and they will in turn belch in my face and poop everywhere, because they are goats. That’s all as it should be.

*Because I know someone will ask: Here ya go.

Aug. 26 2016 9:00 AM

Venus and Jupiter Kiss This Weekend

There’s a real treat in the sky over the next few nights: Venus and Jupiter will be very close together. How close?

Very, very close. Closest approach (what astronomers call the appulse, but is more colloquially and commonly called a conjunction) will be on Saturday at 22:00 UTC (18:00 Eastern U.S. time), and at that time they’ll be an incredible four arcminutes apart. That’s only one-seventh the width of the full Moon on the sky!* In fact Jupiter appears half an arc minute across, so Venus will only be about eight times Jupiter’s diameter away!

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That’s close. Close enough that they’ll barely be far enough apart to separate by eye. The simulated shot at the top of this post shows the view through a telescope at closest approach; you can see Jupiter, its moons, and Venus all together nice and snug.

Now for the not so great news: The two are only a little over 20° from the Sun, so they’ll be low over the western horizon by the time the sky gets dark after sunset. The good news though is that both are so bright they’re visible even while the sky is still bright, especially in binoculars. If you know where to look you can actually see them when the Sun is up, too! But that’s for folks with some experience; do NOT search for them with binoculars; the Sun is so bright it can physically hurt your eyes if you accidentally glimpse it through them.

Venus and Jupiter
In 2012, Venus and Jupiter passed each other, but this weekend's appulse is far tighter.

Guillaume Poulin, used by permission

The conjunction is cool not just because it’s pretty (and it is). It’s also rare. The planets orbit the Sun, moving at different speeds. They all stay in pretty much the same plane—it’s usually called the plane of the solar system—and we’re in it too, so the planets move more or less along the same path in the sky. But not exactly the same path, so they pass each other at various distances. A close pass is pretty rare and in fact this is the closest any two planets get all year.

It’s also cool because of the physical reality of what you’re seeing. Venus orbits the Sun closer than Earth, and it’s on the other side of the Sun right now. So you’re looking past the Sun (which is 150 million kilometers away from us) to Venus, which is about 230 million kilometers away. Jupiter is a staggering 950 million kilometers away!

What amazes me is that even though Jupiter is more than four times farther away, it still appears three times bigger than Venus. That’s because Jupiter is ridiculously huge, a dozen times the diameter of Venus.

And one other thing. I’ve written about Juno, the spacecraft currently in orbit around Jupiter. It currently takes 53.5 days to go around Jupiter once and is screaming back toward Jupiter right now. On Saturday, the same day as the conjunction, Juno reaches perijove, its closest approach to Jupiter—just 4,000 kilometers above the cloudtops! After that it heads back out, moving away from the giant planet once again. In October, it’ll fire its engine and lower the orbit, moving it into its science orbit.

My friend Emily Lakdawalla at the Planetary Society has written about Juno many times, and describes an amazing video showing Jupiter as seen from the spacecraft as it moved away from Jupiter nearly two months ago. Here’s the video, but go read Emily’s write-up, because (as usual) it’s great.

I love how Jupiter is half full, a view we don’t get from Earth.

But our view this weekend (and really for several days) of Jupiter will be amazing, and that’s a pretty good consolation prize. I hope you have clear skies and an unrestricted view of this wonderful event.

Correction, Aug. 26, 2016: I originally misstated that the separation was one-fifteenth the width of the Moon, but the Moon is 0.5 degrees (or 30 arcminutes) across. Thirty divided by four is roughly 7.

Aug. 25 2016 9:00 AM

Follow-Up: Just How Hot Was July 2016?

The other day I posted an article about how ridiculously warm July 2016 was globally. Like every month for 10 months in a row, it was the hottest such month since records have been reliably kept (starting in 1880).

This happens so often now that I just repost the same article, with the dates and numbers updated. That’s one way you know the planet’s getting hotter: When every record hot month or year is the month or year you’re in, it’s getting hotter.

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But there’s more to this. July is generally the hottest month globally in the year, because it’s summer in the Northern Hemisphere, which has more land mass than the Southern one. Land heats up faster than ocean, so northern summer adds more to the overall warmth. This means July was not only the hottest July on record, but the hottest month on record as well.*

The plot at the top of this article shows that, with July clearly in a class by itself. It also shows that 2016 is hugely favored to be the hottest year globally on record, beating the previous two record holders: 2014 and 2015 (and please read the second paragraph above again if that helps you put this in context).

But it’s worse than that. Records being broken is one thing, but even then you have to look at the trend.

There are various ways to do that, but our brains are keyed to see motion. To that point, here’s an animation of that same graph above, showing each year’s monthly temperatures since records began:

NASA's Global Modeling and Assimilation Office

That animations shows temperature anomalies, the deviation from some average (in this case, the annual average over the date range of 1980 to 2015). As you can see, the yearly graph shifts up and down somewhat randomly until just after the mid-20th century, when the average just starts going up. That’s warming. And this plot downplays the data somewhat, because the average is taken so recently, when global warming already had us in its grasp. Had an earlier average been used (say, 1951–1980, which is a commonly used range) then the scale on the left would show higher numbers.

Deniers downplay all this. They say that it’s been hotter in the past, and that the climate changes all the time. Like so many anti-science claims, that’s a tiny parcel of truth surrounded by a huge dollop of crap. Of course it’s been hotter in the past. Of course climate changes. But the rate of global warming we are seeing now is unprecedented, faster by a huge margin than we’ve seen for more than 10,000 years.

That’s why this is scary. It’s how fast the temperature is climbing. The effects we are seeing now are getting pretty obvious, too. Watch this NASA animation of the Arctic ice melting based on satellite observations, starting from its maximum extent in March 2016 to August (note that the minimum extent won’t be reached until September):

While 2016 is unlikely to set a record low extent of ice, every year for the past decade has been far, far below average. How long will it be before we see an ice-free Arctic summer? A few decades. Not centuries, but decades.

I could go on and on, and believe me I have. It’s stunning that people will still deny the reality of global warming, and ignore the slap-in-the-face effects it’s having on our climate. We know this is happening, and politicians fiddle while the Earth burns.

And as I have also said many times: It’s not too late, and there are things we can do. If you’re a U.S. citizen, where this political problem may be biggest, (politely) let your representatives know you care about this issue, and when November comes, vote.

We all live on this planet, and it’s the only one we’ve got. Let’s end this uncontrolled geoengineering experiment while we still can.

*When I tweeted about it, I meant to say “No human alive today has lived through a hotter July. Ever,” but forgot to add the words “alive today.” A lot of pedants jumped over me about that, when still the meaning was clear in the article. I accept I misphrased it, but it would be kinda nice if people actually clicked a link and read an article before going full denial on the internet. A man can dream.

Aug. 24 2016 1:00 PM

Astronomers Discover a New Planet Orbiting the Closest Star to the Sun!

There’s no other way to phrase it. This is HUGE news: Astronomers have found a planet orbiting the Proxima Centauri, the closest star to the Sun!

Holy wow. Seriously. Wow.

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Before I get into details, let me sum up what we know:

The planet, called Proxima Centauri b or just Proxima b (exoplanets are given their star’s name plus a lower case letter in order of discovery, starting with “b”), orbits Proxima every 11.2 days. It has a mass of no less than 1.3 times the Earth’s, so if it’s rock and metal like Earth it’s only a bit bigger. It’s a mere 7.3 million kilometers from the star—a lot closer than Earth's distance from the Sun of 150 million kilometers!—but Proxima is so faint and cool it receives about two-thirds the amount of light and heat the Earth does. That means that it’s in Proxima’s habitable zone: It’s possible (more or less) that liquid water could exist on its surface.

Did I mention wow? Because wow.

The European Southern Observatory put together a nice video about the discovery:

There’s some backstory here, and it’s very cool. Proxima Centauri is only 0.14 times the diameter of the Sun and 0.12 times its mass. Its surface temperature is much lower, so it’s cool and red, what we call a red dwarf. It orbits a binary star called Alpha Centauri, made of two stars more similar to the Sun (so the whole system is a trinary star). Proxima is pretty far out from the pair, about 0.1 light-years or so (a trillion kilometers), about 200 times farther than the distance of Neptune from the Sun. So it’s nearly out by itself in space, barely bound to the binary.

The Alpha Centauri binary is easily visible from Earth’s Southern Hemisphere, though they look like one star at their distance of about 4.3 light-years, and are among the brightest stars in the sky. Proxima, even though it’s closer to us, is so intrinsically dim that you need a good pair of binoculars to see it at all.

Because it’s the closest star to the Sun, astronomers have looked at it for decades to see if there’s any evidence of a planet. There have been false alarms over the years, all eventually shown to be errors.

But this time it looks like it’s very much real. The difference is the quality of data, because our technology and techniques have improved mightily recently. Using two different cameras on two different telescopes, the astronomers divided the light from Proxima into a spectrum showing many individual colors. They looked for subtle and periodic changes in the spectrum that would be due to a planet orbiting the star. As the planet moved, it would tug on the star; Proxima would make a little circle as the planet made a bigger one. This creates a Doppler shift in the spectrum, which in principle can be measured.

The faster the planet orbits, the bigger the shift, and usually the easier it is to detect. The motion Proxima b imparts on its star is very small, just one or two meters per second.* That's very hard to detect.

But the eyesight of the cameras was sharp, and the ability of the astronomers to tease out the signal greater. By using other telescopes to observe the star, they were able to account for any change in the star’s brightness that could masquerade as a planet, confounding the results. In the end, the signal from the planet’s motion came out pretty clearly. I have to admit, it looks pretty solid to me.

That’s important to me: A few years back a planet was announced orbiting one of the stars of Alpha Centauri, which was very big news. But later it was found to be a spurious signal, and in reality no planet was seen. Planet discoveries get retracted every now and again, especially ones where the signal is faint. In this case when I heard the news I was pretty skeptical, but after reading the paper it looks good to me. I’m satisfied the planet is real.

There are some caveats, though. For one, we can’t know the true mass of the planet. If we see the orbit edge-on then it has a mass of 1.3 times the Earth. But if the orbit is tipped, the mass has to be greater to cause the star to wobble as observed, and if the orbit is tipped by 45°, say, the planet’s mass has to be 40 percent bigger. If it’s tipped more, the planet has to be even more massive.

We’re not sure of the shape of the orbit. It might be elliptical (aficionados of exoplanets take note; the eccentricity is no more than 0.35), or it might be circular. But either way, it’s at the right distance from Proxima that, given reasonable assumptions about the planet’s composition, it could have liquid water on its surface. This calculation has a lot of caveats—its temperature without an atmosphere would probably be around -40° C, but Earth’s average temperature without the greenhouse effect is only -15°. So yeah, cold, but if it has enough CO2 or other greenhouse gases in the air (assuming it even has air!), it could be clement there.

If so, that makes it not just the closest exoplanet known, but the closest potentially habitable one known.

Again: wow.

Sun and Proxima compared
Although Proxima is about 1/7th the size of the Sun, Proxima b is so close to it the star would appear three times bigger in the sky than the Sun does from Earth.

ESO/G. Coleman

Mind you, we know nothing of its composition, or even its size. It may be completely uninhabitable, or it might be Eden. There’s no way to know. So be cautious here: It’s likely to be Earth-size, but we don’t know if it’s Earth-like.

Either way, it’s more than 40 trillion kilometers away, so we’re not going there any time soon. The fastest spacecraft we’ve ever launched would take many tens of thousands of years to get there. Don’t pack your underthings just yet.

Still, this is terribly, terribly exciting. We’ve only known for sure about the existence of exoplanets—worlds orbiting alien suns—since 1992. The first found were orbiting a dead star, a pulsar. The first planet orbiting a Sun-like star wasn’t found until 1995, and in the next two decades we built telescopes dedicated to looking for them, and as of today we know of over 3,000 such strange, new worlds.

Quite a few are Earth-size, and fewer possibly Earth-like. Still, we can make estimates that there are billions of Earth-size planets in the galaxy.

And now we know that it’s possible that the nearest one is, on a cosmic scale, right next door.

People say that it’s a curse to live in interesting times. But with science, it’s not. It’s amazing.

*Correction, Aug. 24, 2016: I originally misstated that this was the speed the planet goes around the star, not the speed of the star itself. The velocity of the star as it moves in a small circle is much smaller than the velocity of the planet, which is making a much bigger circle in the same amount of time.

Aug. 23 2016 9:00 AM

Super Slow-Motion Beauty of SpaceX Rockets

Every now and again, I think, everyone can use a little eye candy. In this case, though, it’s more than that: It’s also hope for the future. Watch this high-speed footage of SpaceX rocket launches and landings, and see what the future looks like now.

So cool.

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The first part shows the launch, booster separation, and landing of the first stage booster from the launch on May 4 of the Japanese communication satellite JCSAT 14 on a Falcon 9 rocket. The odd fireworks display in that section of the video is the interplay between the plumes from the first and second stages as they separated.

The landing of this particular booster was a big deal: Although it was the third successful landing (and the second at sea), it was the first time it was done from a launch designed to put a satellite into a geosynchronous orbit, which is much higher off the Earth than a low orbit, and required a higher than usual velocity. Landing this booster was therefore particularly difficult, and marked a big milestone for the company.

The next landing seen in the video was an even bigger milestone: It was the first successful vertical landing of a Falcon 9 first stage booster, accomplished on Dec. 22, 2015, (it was Dec. 21 Eastern time) for the ORBCOMM-2 launch.

I love that part of the footage. The booster used one of the nine Merlin engines to slow its descent, and you can clearly see the single engine burning while the other eight are dark, the dance of the flames playing over them as its blown back up toward the rocket’s back end.

The final part of the video shows the first stage rocket landing back at Cape Canaveral after launching a Dragon capsule to the International Space Station on the CRS 9 mission, launched on July 18. Again, you can see the single engine burning as the booster lowers itself to the pad. The landing legs are folded up during launch, and are deployed on the way back down; you can see the unscorched sections of the booster showing where they were stowed until needed at landing.

Even though the footage is shot in high speed and therefore looks like it’s in slow motion, I suggest playing it back at 0.5 or even 0.25 times the normal speed (on YouTube, click the gear icon on the lower right, then change the speed setting). You can clearly see the play of the flames and the detail of the rocket engines. It’s really astonishing.

SpaceX is getting very, very good at landing the first stage boosters, and has been test-firing them to see how they might perform when reused. This will lower the cost of launch by a large margin, making access to space much cheaper. I’ll add that Blue Origin, Jeff Bezos’ rocket company, has made several suborbital launches and landings with the same rocket, and will be soon attempting orbital launches with a next generation rocket. Several other companies (like Sierra Nevada and Boeing) are also on their way to making spacecraft that will eventually be used to carry supplies and people into space.

The future. We are very nearly in it.

Aug. 22 2016 9:00 AM

Global Warming Has Now Made the Northwest Passage a Thing

More than a century ago, explorers dreamed of a Northwest Passage, a route from the Pacific Ocean to the Atlantic by plying the waterways north of Canada, threading through the Canadian Arctic Archipelago, huge icy islands north of the Canadian mainland.* Such a trip was fantastically dangerous and well-nigh impossible, since in the winter and even most of the summer, the waterways were either frozen solid or littered with huge blocks of ice.

Roald Amundsen was the first to successfully make his way through. It took him three years in a small ship starting in 1903, and included getting stuck in ice three times.

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Fast-forward. On Aug. 16—just days ago—a 250-meter-long, 1,070 passenger cruise ship, the Crystal Serenity, set sail, and is expected to make its way through the Northwest Passage in just eight days.

How can it do so? Global warming.

Over the past few years, the Arctic has warmed so much that the fabled passage has become a reality. The ice melts so much in the summer that it’s not only possible for ships to make their way through the archipelago, but it may be commercially viable to do so.

To be clear, quite a few ships have made the passage since 2007, the first year the ice had melted enough to make it far easier to cross. But it’s been a struggle, and bigger ships have a more difficult time. On average, every year it gets easier as the ice melts away due to the increased heat in the Earth’s northern regions.

Deniers of global warming will make sidetracking claims, talking about how Antarctic ice is increasing (it isn’t), or other non sequiturs (note: In a massive irony, even the fossil fuel companies funding so much climate change denial accept that the Arctic is melting, and are scrambling for rights to drill for oil there). The reality is that the Arctic is warming at a rate twice as fast as the rest of the planet—temperatures in the Arctic have been more than seven degrees Celsius higher than average—and the ice up there is melting so fast that it’s been called a “death spiral.”

And understandably so. Watch:

There are two ways to measure Arctic ice: extent and volume. Volume is obvious enough; it’s literally the volume of ice. Extent is similar to the area covered by ice but is technically defined as the amount of area covered by more than 15 percent ice in a given region. Both have decreased dramatically in the past couple of decades, but the extent is more important for the Northwest Passage. Warmer summers mean the ice doesn’t freeze as much in the winter, so it’s thinner and melts more easily the next summer. That makes getting through with a ship easier.

The record low extent for Arctic ice was in 2012. That was an unusual year; an ice dam collapsed, allowing warmer waters to move north, melting ice far more than normal. Arctic ice hits its minimum extent in September every year, and this year is on course to be among the lowest ever seen.

ice extent
The extent of Arctic ice each month over time. The grqy area shows the average (± two standard deviations; think of it as anything outside this region being statistically significant). The year 2016 is on course to be one of the lowest minimum extents in recorded history.

NSIDC

If you click that graph, you’ll be taken to an interactive version. Click the years to see the ice extent over time. You’ll note that 2012 was indeed the record low, but every year over the past 10 years has been far, far below average.

That’s because of global warming. Experts predict we’ll see our first ice-free Arctic summer around 2040, and given the downward trend of ice extent, that sounds about right. Mind you, this is inevitable; even if we stopped burning fossil fuels today, stopped pouring carbon dioxide into our air, the damage is already done. Warming would continue for decades, perhaps centuries, and the Arctic ice will melt. The same is true for Antarctica; the trajectory of warming means that the western glaciers of that continent are almost certainly doomed to melt away no matter what we do now.

It’s not too late to save our planet, though. There are things we can do. Enact a carbon tax, for one. Switch to renewable energy for another, which is completely doable.

And third? Vote science deniers out of office. They inhabit not only the U.S. Congress but also political seats all over the world.

When it comes time to vote, vote. Climate change is important enough to make it a one-issue election, but some people feel that’s not enough to sway them. But really that’s a matter of framing. Chances are those who deny the reality of climate change deny lots of other science, too. When that one issue is reality itself, then damn straight this is a one-issue election.

*Correction, Aug. 22, 2016: I originally wrote the islands were north of Canada, implying (unintentially) that they are not part of Canada, when they actually are.

Aug. 20 2016 9:00 AM

The Day a Cloud Wore a Cheery Hat

I’ve written many times about summer clouds in Colorado; moisture-laden air blows over the Rockies to the west, flowing to the east. The Midwestern plains butt up against the hills, and as the afternoon Sun heats them, warm air rises vigorously and meets the eastward-flowing wave. Within a few dozen kilometers, this creates towering pillars of massive, wet air, punching upward into the sky.

A cumulonimbus cloud is born.

The drama and sheer energy of these storm clouds is terrifying and awe-inspiring. But even in their brute force, a delicate veil can be created.

Aug. 19 2016 9:00 AM

A Cosmic Flower Blooms and Sends Its Seeds Into the Void

NGC 7129 is a fascinating and terribly lovely object. It’s a stellar nursery, a site of active star formation, buried deep within an invisible cloud of very cold molecular gas and dust. Luckily for us, a handful of massive stars were born near the edge of this cloud, carving a blister in its side and exposing their fierce light and beauty to us:

Holy wow! That image is a combination of observations using the giant 10-meter Subaru telescope, the 0.81 meter Schulman Telescope (from my old friend Adam Block), and a 35 cm telescope, all of which were processed by Robert Gendler and Roberto Colombari.

It’s a spectacular photo to be sure, but there’s a lot of science in it, as well as a surprise.

Aug. 18 2016 9:00 AM

So What Exactly Is an “Alien Megastructure”?

Last week, I wrote another article about KIC 8462852, aka Tabby’s Star, which is behaving very oddly indeed. It shows sharp dips in brightness that last for hours, as well as much longer ones that last for days (or longer) that indicate something is blocking a substantial fraction of the star’s light.

The most likely explanation is a cloud of dust with comets or asteroids embedded in it, which can cause the star to dim. However, it’s been maddeningly difficult to explain all the star’s behavior with this natural model. So, ever since its discovery and perhaps a bit sheepishly at first, astronomers have toyed with the idea that maybe what we’re seeing is evidence of an advanced alien civilization.

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To be clear, no one is saying that’s what’s going on. But it’s a cool idea, and worth investigating at least a little. No radio signals have been seen from the star, though, and no other indication of aliens has been found.

Still, it’s fun to think about. The premise is that aliens are building huge panels of some kind around the star in order to capture more of its light to power their civilization (imagine it like the ultimate work of a Little Green Elon Musk). The idea of alien megastructures has been around a while, and has some merit as a thought piece.

Astronomer David Kipping, who studies Tabby’s Star, made a short video explaining all this simply and engagingly. He does a great job summing up what we know:

Kipping studies exoplanets and moons, and he and I agree strongly on this topic. It’s fun, it’s interesting, no astronomer really thinks this is what’s happening for sure, but it’s a compelling idea and well worth looking into. You know, just in case.

For more details and insight into what’s going on with Tabby’s Star, astronomer Jason Wright also made a video diving into the topic more deeply:

Back when all this started I had a long and very engaging conversation with Jason about it, and his take on it is grounded in reality and firmly based on evidence. His conclusion, like all the rest of ours, is that this is a highly intriguing star, its behavior is almost certainly natural, but it’s stimulating and perhaps even rewarding to look into more speculative explanations. They’re unlikely to turn out correct, but they stretch our imaginations and exercise our brains in a way that can be helpful in solving mysteries.

So, as usual, I’m still not saying aliens. But no matter what this turns out to be, it’s wonderful and stimulating, and just good old fashioned fun for a scientist to think about.

More about Tabby's Star:

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