A Cold Ribbon Where Future Stars Are Born
The Universe lights up when you look at it with different eyes. And, in a very real sense, I mean that literally.
Our galaxy, the Milky Way, is more than just a few hundred billion stars. It’s also loaded with gas and dust, the raw materials from which stars are made. And stars are being made: roughly two to four times the Sun’s mass worth of stars are born every year in our galaxy. Usually that means lots of little stars like red dwarfs, but sometimes it means a truly massive star dozens of times heftier than the Sun. But on average, a handful are born every year.
They form in nebulae, clouds of gas and dust, under a variety of circumstances. There are huge cold clouds of dust out there called molecular clouds, and these are key sites of star birth. They can have regions inside them, knots or clumps they’re usually called, where the density of material is pretty high, big enough that gravity is a player. This material can draw itself together, and stars condense out of the resulting collapse.
That material has to be cold, or else its internal heat can prevent the collapse. So, ironically, one of the best places to look for stars about to be born is inside the coldest places in the galaxy.
The image above shows one such place: a ribbon of brutally cold dust and gas, only about 15°C above absolute zero! The image was taken by the ESA Herschel observatory, which is sensitive to light in the far infrared, way way outside what our eyes can see. This sort of light is emitted by very cold objects, such as clouds undergoing collapse.
The ribbon of material, called LDN 914 (or G82.65-2.00 depending on what astronomical catalog you like) is about 50 light-years long and has about 800 times the mass of the Sun in total, plenty of raw material to make stars. Come back in a few million years, and this will look quite different, lit up by the fierce intensity of dozens of newborn stars.
When I saw this image I thought it looked familiar. It turns out I was mistaken; I was thinking of a different ribbon of star-forming nebula I wrote about back in 2013. But that got me wondering what this object looked like in visible light. I had a suspicion I knew, but I wanted to make sure.
I dug around the ‘net but didn’t find anything at first. Then, on an astronomy forum for astrophotographers, I saw a post by Werner Mehl. He had taken a very deep exposure of the sky in the constellation of Cygnus, and in his shot was a ribbon of dark material he was having difficulty identifying. Here’s his photo:
Gorgeous, isn’t it? I grabbed his picture, rotated and resized it, and bingo! It’s a perfect match to LDN 914. I contacted Mehl to ask his permission to use it, and also let him know the name of his find (if you’re curious, LDN stands for Lynds Dark Nebulae, a catalog of such objects first published in 1962).
But perhaps you’ve noticed something weird: In Mehl’s photo, LDN 914 is dark, but in the Herschel image it’s bright. What’s going on?
In visible light, that cold dust is extremely opaque. It’s very efficient at blocking light from the stars behind it, and so Mehl’s image shows it as black, with very few stars in it (those are certainly foreground stars, closer to us than the nebula and so unblocked by it).
But anything above a temperature of absolute zero emits light, and what kind of light depends mostly on its temperature. The Sun is very hot and glows in visible light. A red dwarf is cooler and emits mostly red or infrared light. Cold dust clouds glow in the far infrared, where Herschel can see them.
And that’s what I meant at the top of this post. When you look at the Universe with different eyes, it literally lights up.
My favorite examples of this are when visible and far infrared images are overlaid; you can really see how something dark in visible light glows brilliantly in longer wavelengths. The best ones I’ve seen are the Cat’s Paw Nebula, IC 5156, and this, M78 in Orion:
The blue part of the image is visible light and has very dark dust lanes running through it. The orange is from APEX, which sees light with submillimeter wavelengths, where cold dust glows. I love how they fit together like puzzle pieces. Amazing. And truly lovely.
See how beautiful something can be when you widen your perspective a little bit? If there’s a life lesson there, feel free to take it.
Post script: And oh yes, the reason LDN 914 looked familiar to me? I was able to crack that one pretty easily.
These Dunes Are the Pits. Or Vice Versa.
I love a good coincidence. Especially a series of them. To wit:
Last week I wrote an article about a massively viral optical illusion photo of a brick wall—if you haven’t seen it yet, I won’t spoil it; just go to my post and be amazed.
The very next post I put up after that had images taken by the Dawn spacecraft of the protoplanet Ceres, showing the cratered surface.
The funny thing is I got a few emails and tweets from people saying they were seeing the craters not as depressions in the surface, but as domes popping up out of it.
I had to chuckle about that. That’s another illusion I know very well, usually called the crater illusion. It was a funny (if minor) coincidence that people saw it in the post following a post about an illusion. It was funnier to me because in the brick wall post, I actually (and also coincidentally) linked to one of my favorite examples of the crater illusion, where dunes in the north African desert look like holes in the ground.
The icing on the coincidental cake? The very next day, the European Space Agency posted a photo of the Rub al Khali desert in the Arabian Peninsula, showing this same illusion, also featuring sand dunes!
The photo at the top of this post shows a part of the (much larger) image, taken by the Sentinel-2A satellite in December 2015. To me, the illusion that the dunes are actually pits in the surface is very strong. Does it look that way to you?
The reason for this is that we evolved to interpret scenes assuming the light is coming from above, like sunlight. When we see a photo, our brains assume the sunlight is coming down from the top of the picture. Something popping up out of the surface (like a sand dune) would be illuminated by that source of light, with the upper part of it (the part nearer the top of the photo) bright and the lower part shadowed.
But in the Sentinel photo, the lower parts of the dunes are bright, and the upper parts dark. That’s because the sunlight is coming from more or less the bottom part of the photo. But our brains have a hard time with that, assume the light is coming from above, and think the dunes must actually be pits. To our addled brains, something with its brighter part toward the bottom must be depressions in the surface, not something popping up out of it. So we see the dunes as pits.
Don’t believe me? I flipped the image over. Take a look:
Now that the light looks like it's coming from the top of the image, do they look like dunes to you? They do to me!
I played with the images for a while and found the illusion to be stronger when I shrank it down quite a bit; if I zoomed in on the dunes I saw them as dunes, and not pits. That was odd. I suspect the wavy lines of dunes give clues to my brain that the lighting doesn’t make sense if they’re pits (especially where the dunes make tight Z-shaped jogs in the lines). Those clues are too small to resolve when the image is smaller, so the illusion is stronger.
As always, while fun, there’s an underlying message here too: Your brain is lying to you. All the time. It does not see the world for what it is, but instead interprets it through a vast number of filters and preconceptions.
What you see is not what you get. It’s a pretty important lesson to remember.
Jupiter May Be Hit by a Half-Dozen Visible Asteroid Impacts Every Year
In 1994, Jupiter was pummeled by the repeated impacts of the comet Shoemaker-Levy 9. The comet had been caught by the planet’s gravity earlier, torn apart by the tidal force during a close pass, and then each chunk slammed into Jupiter’s upper atmosphere and exploded, one by one, over the course of a week.
These impacts were easily seen from Earth (I saw the dark dust clouds peppering the cloud tops of Jupiter myself through a 15 cm telescope!), the first time any body other than Earth had been unambiguously seen to be hit by a comet or asteroid.
Since that time, five more impacts have been seen: in 2009, June 2010, August 2010, 2012, and 2016. In each case, the events were caught accidentally by amateur astronomers when they were taking video of Jupiter!
This raises the question: How often is Jupiter actually hit by an object big enough to make a flash visible from Earth?
At a workshop held earlier in May to encourage amateur astronomers to observe the planet in support of the upcoming arrival of the Juno mission to Jupiter, astronomers announced they have an estimated answer: Jupiter gets visibly hit by six to seven chunks of cosmic debris every year.
Yegads. That’s a lot!
They determined that number not just by the times amateurs have seen impacts on Jupiter, but also by how much they didn’t. If you happen to look at Jupiter and see an impact, you can’t know if you were just lucky; you have to observe the planet for a long time to see just how much it gets hit. In this case, observations from about 60 amateurs totaling more than 56 days of video were analyzed to look for impacts. None were seen, but that provides a valuable baseline for the impacts that were caught by accident by other amateurs.
While this is an estimate (and has not been through the peer-review process), it jibes with the numbers I was coming up with based on the impacts we’ve seen; on the order of once per year (meaning one to 10 times). And that’s only the impacts we can see; we miss half because they hit the far side of Jupiter, facing away from Earth, plus some when they occur within a few weeks of the time Jupiter is behind the Sun as seen from Earth.
Clearly, what we need here is a bigger team of astronomers across the Earth observing Jupiter, so we cover it as much as possible. The folks at the Juno workshop are working on that, as well as improving software that will allow analysis of video taken.
Why video? Well, it gives better time coverage of the planet—a single exposure is generally less than a second (Jupiter is bright through a telescope!), and a video can run for a long time. Also, Earth’s atmosphere boils and seethes, blurring out small details in astronomical targets. Video frames can be very short exposures, helping minimize that blur. Plus, one part of Jupiter might be relatively unaffected in one frame, while a different part of the planet looks better in a different frame. Sections of different video frames can be cropped out and reassembled to create a single, high-resolution shot of the planet. This is a relatively standard technique used by amateurs these days, and was how those more recent impacts were discovered.
As for the science, that part is pretty interesting. The impacts we see (with the exception of Shoemaker-Levy 9) are from pretty small asteroids, probably just a few dozen meters across. Jupiter’s ridiculously strong gravity pulls them in so hard that they are moving five times faster than impacts on Earth on average, making them 25 times brighter (energy released goes as the square of the impact velocity). In that case, even a smaller body can make a bright flash.
Asteroids that small are impossible to see directly from Earth because Jupiter is so far away. So the impacts on Jupiter give us an indirect way to figure out how many such objects are out there. Also, we don’t see too many impacts on other objects (pretty much just the Moon), so the more we see the more we can understand these events. I’m all for that.
As an aside, astronomy is one of the very few fields of science where amateurs* can make valuable contributions. Big professional telescopes are oversubscribed, and can’t afford the time to sit and stare at Jupiter for nights on end. In cases like this (and in many, many others) people with their own ‘scopes really fill a big gap in our understanding.
As someone who considers himself both an amateur and a professional astronomer, I love this. Science should be for everyone, whether you just want to learn more about it, enjoy it yourself, or participate in it directly. Astronomy is a fantastic way to do all of these things.
*Like so many other things in astronomy, there’s no good definition of what an “amateur” is. Someone who isn’t paid? Someone who does it as a hobby, or once a year when they haul a ‘scope out to look at the Moon, or who has done it for so long they know the sky like the back of their hand and write their own software to analyze their observations and create gorgeous images or scientific data? Yes.
A Dozen (or So) Ways to Die in Space
Macabre? Sure. But my sense of humor runs dark sometimes, and I love science fiction, so this (very) short animation (very) briefly depicting a bunch of ways hapless space explorers can undergo Death in Space cracked me up.
I could nitpick the science—you won’t explode if you crack your helmet, but it won’t exactly be fun either—but that’s not really in the spirit of the thing. And that’s coming from a guy who literally wrote the book on this subject.
Tip o’ the spacesuit helmet to io9.
Now’s a Good Time to Look Up as Mars Looks Back at You With Its Red, Baleful Eye
The other day I was puttering around in the house a couple of hours after sunset and happened to glance out an open window. There, shining over the horizon in the east like a glowering eye, was an intensely bright red-orange “star.” I stopped for a moment, surprised, then realized what was going on: The star was a planet, specifically Mars, and it’s nearing opposition.
If you have a telescope, know someone who does, or live near an astronomy club (click here to find out!) or observatory, now’s the best time all year to see the Red Planet. It’s up all night and about as close as it can get to Earth. On May 30, it’ll be just a hair more than 75 million kilometers away, which as planets go is pretty close.
No, Mars won’t be as big as the Moon in the sky! Mars is only about 6,800 kilometers across, about half the width of Earth, and from 75 million kilometers away it looks pretty small. Still, it’ll be close enough that with a decent ‘scope you’ll see surface features. Maybe not as nice as that Hubble Space Telescope picture at the top of this post, but it’s pretty amazing to be able to see detail on the planet with your own eyes. If you get a chance to use a telescope over the next few weeks and observe Mars, take it!
So what’s going on? Mars and Earth both orbit the Sun like two cars going around a racetrack at different speeds; the Earth is on the inside track and moves a little faster. When Earth passes Mars on the inside curve, they’re as close together as they can be. When that happens, from Earth, we see Mars on the opposite side of the sky from the Sun—hence the term opposition. Because of that it rises when the Sun sets, and is up all night. It’s a twofer: Mars is as close as it gets, and it’s up at a convenient time to see it.
Things do get a bit complicated in the details. For example, Mars is on a fairly elliptical orbit that takes it as far as about 250 million kilometers from the Sun and as close as 207 million kilometers. That means some oppositions are better than others; the closest approach can range from 100 million to as little as 57 million kilometers from Earth. That means this one is fair to middlin’.
Because of its elliptical path, it also means opposition and perigee (the time it’s closest to Earth) don’t fall on the same day; opposition is May 22, over the weekend, but perigee is a week later.
Still and all, it’ll be bright and pretty for the next few weeks, so you don’t have to rush out and see it only on May 30! Any time through June and even July will be cool.
And if you want to impress people with your knowledge of Mars as you observe it at a star party, then may I suggest watching my episode of Crash Course Astronomy about the planet? Take notes if you want; there’s no test. The only goal is to understand the Universe around you better and appreciate it a little more.
Of Course Trump Chose a Global Warming Denier as His Energy Adviser
Donald Trump has announced his new energy adviser: Rep. Kevin Cramer (R–North Dakota).
I hope you’re sitting down for this shocker: Cramer is a global warming denier. And to be clear, he’s not just a denier. He’s a crackpot.
First, watch this video put together by the folks here at Slate to get an overview of this guy’s view on science:
Trump’s grave misunderstanding of the difference between weather and climate doesn’t surprise me; he’s a buffoon when it comes to such topics (case in point: he said global warming is a hoax manufactured by the Chinese). Given his history, his choice of a crackpot for energy adviser isn’t terribly surprising.
Cramer has a long record of climate change denial (apropos of nothing, over his career Cramer has received more than a half million bucks in funding from the fossil fuel industry, more than twice as much as any other industry). That’s also not surprising given that North Dakota is one of the largest producers of oil and coal in the nation. The burning of excess natural gas fracked in the state is so intense it’s easily visible to satellites in space. Given all that, Cramer denying climate change is de rigeur.
It’s the degree (so to speak) to which he denies it that’s staggering. He’s part of the tiny, tiny head-in-the-sand deniers who won’t even acknowledge the planet’s heating up. That line in the video where he says, “We know the globe is cooling; number one we know that” is from 2012, just a few years ago. We’ve known since long before then the planet is heating up, and the past few years the warming has gone into overdrive; each of the past seven months have been the hottest of those months globally. To actually say out loud that the Earth is cooling would make Orwell blush.
But he wasn’t done; he also added, “… the idea that CO2 is somehow causing global warming is on its face fraudulent.”
Holy. Baloney. He’s not just denying global warming, he’s denying a link between carbon dioxide and the planet’s increasing temperature. For the record, carbon dioxide being a greenhouse gas has been a matter of scientific fact since 1896.
The conservative party really is conservative. When it comes to science, Trump and Cramer want to wind the clock back to the nineteenth century. At least.
Cramer has made it clear that if Trump gets elected, he’ll be no friend to the environment, rolling back regulations and reversing the Clean Power Plan. Trump himself has said he’ll back out of (or “renegotiate”) the Paris climate treaty, a claim he makes based on 100 percent utter nonsense.
It couldn’t be more clear: If Trump does indeed take the White House our planet is, basically, screwed.
So, there you go. Nothing about this is at all surprising from the candidate who put away the dog whistle years ago, bringing out into the open the contempt he has for women, people of color, Muslims, gays, decorum, facts, and science. This is what the modern GOP hath wrought, and come November, hopefully they’ll reap what they’ve sown.
Update, May 20, 2016: Due to a production error, an incomplete version of this post was originally published.
Cards Against Humanity Just Paid for a Young Woman’s College Tuition
In April 2015, I wrote about a new expansion pack for the ridiculously popular game Cards Against Humanity. The new pack was the brainchild of Zach Weinersmith, who asked me to help come up with some of the funny science-based questions and answers to the party game.
That was an easy decision on my part, but it was made even easier because the CAH folks decided to take all the money—yes, all of it—that was made from the science pack and create a full-ride scholarship for young women attending college for a STEM (science, technology, engineering, and math) degree. This is a fantastic cause and something that can really help address the imbalance between men and women in STEM.
The call went out for video submissions, and more than 1,000 young women applied. The panel of 60 professional women in STEM went through them, and they have announced a winner: Sona Dadhania, a freshman at the University of Pennsylvania! She wants to study nanotechnology, and she put together this video as her submission:
Nice! She’s a freshman now, so CAH will pay for her tuition for the next three years (a sum of about $150,000). You can read more about her in an article on Philly.com. As for how she reacted to the news, well, see for yourself:
Yes, that may have choked me up just a little. I’m so happy for her, and proud of my friends for what they’ve done here.
But they’re not done here! The pack has so far raised more than $880,000—yes, you read that correctly—to help women get a STEM degree. That means there’s plenty left over for more scholarships, and applications for Round 2 will be opened this fall. Stay tuned.
Congratulations, Sona! Go make the world a better, cooler, and smarter place. And, y’know, just throwing this out there: The science pack is available at the CAH online store. If you already bought one, then thanks. Look what you helped do!
Tip o’ the Erlenmeyer flask to my friend Kim Arcand.
White Spots Blemish the Face of Ceres
A new image of the protoplanet Ceres from the Dawn spacecraft caught my attention recently. It shows the western rim of a crater called Azacca (named after the Haitian god of agriculture; Ceres was the Roman goddess of agriculture). Only a portion of the 50-kilometer-wide crater is shown, but there’s a number of interesting features lurking there.
The most obvious is the small crater right on the rim. It’s younger than Azacca; it overlays the rim, so the impact that formed it must have happened after Azacca was already there. It’s fresher looking, with a sharp rim, though it has smaller craters inside, which implies it’s not exactly young. It’s been around long enough to collect some later impacts of its own.
The bright streaks along the young crater’s rim caught my eye. Once a crater is made, material along the walls can slide down into it, revealing material that was once under the surface. In this case, those brighter streaks are tantalizing. Are we seeing the same sort of bright material that has captured the imagination of so many people since Dawn first approached Ceres back in January of 2015?
The most likely culprit for these bright features is salt. Maybe magnesium sulfate, a common mineral. We know Ceres has a lot of water ice in it, which may have been a subsurface ocean, a mantle of water, early in its history. Salts would have dissolved in it, sticking around even today, long after the undersurface water froze. If so, some sort of process may still be bringing it to the surface to create the bright features we see now.
Look around that crater. See all the bright spots? Here’s a closer view:
Each pixel in the original (1,024 x 1,024) image is about 35 meters on the surface, and many of those spots are 2–10 pixels across, so 70 to 350 meters in width. At least some look like small impact craters. It’s likely there’s ice just under the surface, excavated when small asteroids impact Ceres.
Interestingly, I found an image of Azacca itself that also shows small white spots in it. I’d expect a large impact would vaporize the ice underneath the crater, yet there are those spots. Is ice from deeper within Ceres coming up through cracks/vents in the crust? There are much larger cracks in the floor of Azacca, possibly due to pressure underneath the crater pushing the floor up (though cracks in the surface have many different sources). Hmmmm.
As my friend Emily Lakdawalla wrote on her blog at the Planetary Society, the key to understanding the surface of Ceres is to understand what lies beneath. There are plenty of clues! With Dawn continuing to map this weird little world in high resolution, the evidence will continue to come in. I hope planetary scientists can make sense of the place. I do love a mystery, but I also love it when it’s solved. There are always more to take its place.
A Fantastic Optical Illusion: Just Another Brick in the Wall?
I love optical illusions, especially ones that really twist your brain around. I saw one recently that really had me going for a minute. And it’s not so much the illusion itself that really gets me, but my own brain’s reaction to it.
Click through for the photo. I saw it on a Facebook post from this week, though it’s been around since at least 2014*. It shows a brick wall, seen at a shallow angle, with somewhat large gaps between the bricks. The bricks are red, and it appears that there’s a small, gray rock stuck in between them just above center.
So what’s the illusion? I couldn’t see it at all, even after a good 30 seconds of staring at it. I was starting to suspect there was no illusion, and it’s a gag to fool people, when I read the comments and realized what I was missing.
If you still haven’t seen it, then what follows will spoil it for you. If you don’t want to know then don’t read any further until you’ve figured out the illusion!
Watch the Expansion of Debris Hurled Into Space by a Supernova
When you look at the image above, you may be reminded of a cell undergoing mitosis. Certainly, even if you knew it was an astronomical object, you’d be excused if you missed the idea that it’s actually one of the most catastrophic events in the Universe: a supernova.
The violence of a supernova is almost too huge to overstate. When a star explodes (an entire star! Exploding!), the energies involved crush our human perspective into dust. There are two general types of supernovae; one where the core of a massive star collapses, generates ridiculous amounts of energy, and the outer layers explode outward. The other — the kind we are concerned with here — is when a white dwarf (the dead, dense core of normal star) steals matter from a nearby companion, compresses it, and eventually explodes. In both cases, a vast amount of material, as much as an octillion tons of vaporized star-matter, is hurled outward at a significant fraction of the speed of light. This debris covers millions of kilometers in seconds, billions in hours, detonated by a blast that’s equivalent to the entire lifetime’s supply of energy from a star ignited all at once*.
We have observed literally thousands of these events, but, even for the closest, the fantastic speeds of their motions are dwarfed by their distance from us, seemingly frozen in time when you see their images.
Only, that is, if you aren’t patient. In a single image that motion is invisible, but wait a few years, and even the chilling remoteness of a galactic supernova cannot erase the motion of its debris.
And we do have the sharp eyes and glacial endurance of telescopes. In the case of the image above, the Chandra X-ray Observatory (together with radio observations from the Very Large Array in New Mexico) observed a supernova remnant over the course of several years, and when those images are put together in an animation, the expansion of the vast cloud of matter is visible. Behold!
Let that animation repeat a few times; the motion is most apparent in the outer blue ring, the glow from electrons heated to 10 million degrees Celsius by the exploded star’s shock wave. The debris itself is turbulent, bubbling away from the center, and its motion too can be seen over the decade and a half of observations.
As the animation plays, let this thought run through your brain: These observations indicate that in some places in the cloud, the debris is expanding at a numbing 5,000 kilometers per second. In the time it takes you read this paragraph, the gas will have traveled comfortably farther than the diameter of the Earth.
The star that gave up its life for these observations lies between 6,000 and 9,000 light-years from us—60,000 to 90,000 trillion kilometers—and when its light reached Earth in 1572, it was bright enough to outshine every other star in the sky, and even be visible during broad daylight. Astronomer Tycho Brahe was captivated by it, documenting his detailed observations made before telescopes were commonly used to peer into the sky. Had he been able to see its motion, he may have guessed what it was.
To me, this is thrilling. Astronomical objects are so distant and so vast that change in them seems impossible; it feels as if they will appear now as they always have, and always will. But the Universe changes at its own pace, and that evolution is perceivable by humans due to our own curiosity and sense of exploration. Despite its appearance over the puny duration of a human life span, the cosmos is neither eternal nor static. But we only notice if we’re paying attention.
*Correction, May 19, 2016: I originally described only a core collapse supernova, but this particular event was from a Type Ia, where a white dwarf explodes. My thanks to Peter Edmonds for pointing this out to me!