According to my software, this blog post you are reading is the 7000th article I have published on the Bad Astronomy Blog.
That’s a lot of words. It’s also a lot of astronomy, geekery, science, antiscience, web comics, puns, embiggenates, and "Holy Haleakala!"s (61, to be exact, plus this one to make 62).
I am generally not one to wade into maudlin celebrations of arbitrary numbers, so instead I’ll celebrate this milestone by showing you something appropriate: the North America Nebula, taken by Mexican astronomer César Cantú.
[Click to encontinentenate.]
Why is this appropriate? Because the New General Catalog of astronomical objects – familiar to and used by astronomers across the planet – lists it as entry number 7000.
And it should be obvious why it’s named as it is.
Of course, I can’t leave you with just a pretty picture. This nebula is something of a mystery; we don’t know how big it is or how far away it lies. In the sky, it’s very near the star Deneb – which marks the tail of the swan constellation Cygnus – and Deneb is a massive, hot, and luminous star. It’s possible the gas in the nebula is glowing due to the light from Deneb; if so NGC 7000 is about 1800 light years away and over 100 light years across.
It’s the site of furious star formation, too, with stars being born all along the bright sharp region which look like Mexico and Central America. The "Gulf of Mexico" region – the darker area with fewer stars – is actually the location of thick interstellar dust that blocks the light from the stars behind it. Visible light, that is; the dust glow in the infrared, so if you look at it with a telescope that sees IR like the Spitzer Space Telescope, what is invisible becomes ethereally visible:
This mosaic shows the North America Nebula in different wavelengths of light: in the upper left is visible light; the upper right is visible plus infrared, so you can see the two together; the lower left shows infrared light from 3.6 to 8 microns (roughly 5 – 11 times the longest wavelength the human eye can detect), and the lower right is similar but going out to 24 microns, over 30 times the wavelength we can see. The visible light images show the gas, while the infrared show not only the dust, but the warm spots where stars are being born, their new light penetrating the surrounding cocoons of material, reaching across space, and finally ending its journey here on Earth where we can detect it and learn from it.
I’ve struck upon many ideas for this blog over the past seven years, six months, and one week I’ve been writing it, but one of the most important is this: not everything is as it seems. Whether it’s someone’s opinion, a "fact", a picture, an argument, or even a vast sprawling cloud of gas and baby stars a thousand trillion kilometers across, this much is what astronomy and critical thinking has taught me: What you see depends very much on how you see it. And if you want a more complete picture, something that ever-approaches reality, you must view the Universe with different eyes and with an open, but trained mind. Only then will you not get fooled, and not fool yourself.
Thank you honestly and sincerely to everyone who’s been along with me this far into the ride, here on my 7000th milestone. There’s still a long way to go, of course, but it’s the journey itself that’s so much fun!
Image credits: César Cantú; NASA/JPL-Caltech/L. Rebull (SSC/Caltech)/D. De Martin
The wonderful astrophotographer César Cantú takes amazing pictures of the sky, and his shots of the Sun are truly cool. On Wednesday, August 8, 2012, he took this image of the Sun and a sunspot called Active Region 1524:
The Sun is a 1970s orange shag carpet!
Actually, César used an Hα filter, which blocks almost all the light from the Sun except for a very narrow slice of color where hydrogen emits light, and in fact this is preferentially given off by hydrogen under the sway of magnetic fields on the Sun, so this image accentuates magnetic activity. You can see lots of structure like the sunspots and the plasma flowing along magnetic fields – especially along the Sun’s edge, where they’re called prominences.
The Sun looks amazingly different depending on how you look at it. Far from being a featureless white disk, it actually has detail all the way down to the resolution of our best telescopes. The surface of the Sun is fiendishly complex, and the amount to understand is equally daunting. And, as usual with astronomy, with this complexity comes astonishing beauty.
Image credit: César Cantú, used with permission.
The Sun has been in a bit of a mood lately, spitting out some pretty big flares (including the second largest one of the current magnetic cycle). Alan Friedman, one of my favorite astrophotographers, caught the culprit sunspot, Active Region 1429, as it was nearing the edge of the Sun on Monday:
Doesn’t look like your normal shot of the Sun, does it? [Click to ensolarnate.]
Alan uses an Hα filter, which cuts out almost all the light from the Sun except for a narrow slice of color emitted by warm hydrogen. This reduces the glare hugely, and reveals delicate structures in the Sun’s plasma. He then inverts the image, so bright things appear dark, and vice-versa. That’s an old astronomer’s trick that makes fainter things easier to see. He also used a false color palette to make it appear reddish. That’s actually a good idea, since the color of light emitted by the hydrogen is at 6563 Angstroms, right in the middle of the red part of the spectrum!
In this case, doing all this makes the Sun look like a 1970s shag rug. It’s a technique he uses to great effect. Just click on the Related Posts links below to see how!
Andf you’re wondering what the whole Sun looked like instead of just this closeup, then feast your eyes on this:
César Cantú is an astrophotographer in Mexico. I follow him on Twitter, and hardly a week goes by without him posting a link to some amazing picture he’s taken of a celestial object.
And this is no exception: here is his image of Comet Garradd, a chunk of ice and rock that’s currently about 200 million kilomertes (120 million miles) from Earth:
[Click to encomanate.]
Isn’t that lovely? The comet itself is a bit smeared out since it moved over the time as the picture was taken. But even so, wait a sec — you may have noticed something else odd about this picture. Comets have a tail, right? So why do you see two tails, a blue one pointing off to the left and the other reddish, pointing off to the right?
Aha! Oh, I love a chance to lecture a bit. Bear with me. This is cool.
As I said, comets have a lot of ice in them. As they near the Sun that ice warms, and turns directly into a gas (that process is called sublimation). This gas expands away from the solid nucleus, forming a fuzzy cloud called the coma (Latin for "hair").
Now this is where things get interesting. This coma has both gas in it as well as dust and grains of rock carried off as the ice goes away. The Sun blows out a wind of subatomic particles called the solar wind. This ionizes the gas — strips off one or more electrons — and that gas then gets dragged along with the solar wind. That wind is moving, traveling at several hundred kilometers per second, far faster than the comet moves. So that tail gets blown directly away from the Sun. It tends to be blue (or sometimes green), due to the ionized gas in it.
But the dust and rock isn’t affected as much. As it moves off the comet, it tends to lag behind a bit, following the comet in its orbit. This material reflects sunlight and also reddens it a bit, so that makes the dust tail look yellow or red.
And that’s why there are two differently colored tails pointing in different directions! You can read more about this here.
In fact, I can show you what’s going on even better. The JPL website has an orbit simulator for comets and asteroids, and I created a diagram for Comet Garradd for when César took his picture:
The Sun is in the center, and the planets are labeled; I deleted the orbits for all the planets except Earth and Jupiter so you can get a sense of the plane of the solar system. The comet is in blue, and as you can see its orbit is not at all aligned with the planets; it punches upward through the plane on the right, and then plunges back down on the left. It may be hard to get a 3D image of this in your head, but I added in the two tails: the blue ion tail pointing away from the Sun, and the redder dust tail lagging behind the comet itself. From the viewpoint of the Earth, "underneath" the comet, the tails appear to be on opposite sides of the comet and pointing in opposite directions! It’s just perspective making it look that way; at this point in the comet’s orbit the tails are actually closer to 90° apart.
Strange, isn’t it? I’ve found that three-dimensional thinking is one of the tougher barriers to people really understanding how objects move in space (that, and the vast physical scale of space that crushes our minds to dust). But perspective counts! In astronomy, as well as life itself. And when you get a little perspective, why, sometimes things are even cooler than you first thought.
Image credit: César Cantú.
As the Sun rotates roughly once per month, we see different features come into view… and the latest is an enormous sunspot system which just came around the limb of the Sun:
[Click to magneticfieldentanglenate.]
That shot was taken by the Mexican "amateur" astronomer César Cantú, and shows the spots — called Active Region 1339 — from November 4. The size of this system is staggering; the whole thing is well over 100,000 km (60,000 miles) across, and the dark cores are each about the size of our entire Earth!
They’re active, too: On November 3rd they popped off a pretty big X 1.9 class flare:
That image was taken by NASA’s Solar Dynamics Observatory in the ultraviolet, where violent activity is easier to see. NASA made a video of the flare, and you should take a look. It’s pretty amazing.
So we have a recipe for some action here: big spots, known to be active, and they’re riding the Sun’s surface as it rotates them more fully toward us. Over the next week and a half we might get some more flares from them, and maybe some coronal mass ejections… and that means we might get more aurorae. Stay tuned here; if any occur I’ll report them as soon as I hear. Also keep your browser pointed at SpaceWeather.com, which always has the latest info as well.
Image credits: César Cantú; NASA/SDO
Yesterday, "amateur" astronomer César Cantú took an amazing mosaic image of the Sun, showing our star boiling and writhing under its own dynamic forces:
[Click to unGdwarfenate.]
That hardly looks like the Sun, does it? That’s because he used a filter that blocks all the light we see except for a very narrow slice of color in the red part of the spectrum. That filter lets through only light from warm hydrogen, at just the right temperature to allow the electrons in the hydrogen atoms to drop from the third energy level to the second. You can picture the electron in an atom like it’s on a staircase, and only allowed (by quantum mechanics) to sit on a step, or move from one to the other. It takes energy to move it up a step, and gives off energy when it moves down. When it jumps down from the third to the second, it emits a photon — a particle of light — at a wavelength of 656.3 nanometers, and astronomers call this light Hα (H alpha).
The gas on the Sun’s surface emitting Hα is under furious stirring due to magnetic fields and other forces, and you can see that in the twisted, roiling appearance in this photo. I particularly like the dark arc just left of center: that’s a filament, an eruption of gas off the surface. It’s about 150,000 kilometers (90,000 miles) long! It’s a bit cooler than the surface material, so it’s darker, and we see it in silhouette. When those happen on the limb of the Sun they’re called prominences, and you can see several of those in this picture too.
Amazingly, this picture (which is really a mosaic of six separate shots) was taken using a telescope with only a 90 mm (3.5 inch) lens. The Coronado 90 mm telescope is a favorite of sidewalk astronomers, since it shows the Sun in amazing detail, but is totally safe to look through since it blocks almost all the Sun’s light. It’s common to see them at planetaria and museums, set up where passers-by can get a quick glimpse of the Sun. For most, it’s the first time they ever see the might and power of a star only 150 million kilometers away.
And if you want a sense of scale here, in the picture above the Sun is about 450 pixels across. On the same scale, our entire planet Earth would be only about 4 pixels across.
Just in case you were feeling big and important today.
Credit: Image used by permission of César Cantú.
I’ve been an astronomer a long, long time. Even so, I still sometimes get surprised at how different the same object can look when imaged in different ways. I just saw an excellent example of this… W5, aka the Soul Nebula:
[Click to ennebulanate.]
Pretty, isn’t it? It was taken by César Cantú, an amateur astronomer in Mexico. It’s not a true color picture. Not even close! For one thing, he used three filters which let through extremely narrow wavelengths of light (that is, the filters reject all light except for a very thin range of wavelengths; I’ve written about them before). Our eyes see broad ranges of colors, so immediately these filters change the very nature of the picture. Different atoms in space emit at different colors, and the filters he chose select for hydrogen, oxygen, and sulfur, which tend to emit light very strongly in gas clouds.
Not only that, he mixed and matched the colors. The hydrogen filter lets through red light, but he colored it green in the picture; oxygen is usually green but he made it blue*; and sulfur is red which he actually did color red. This throws off my usual sense of what I’m seeing in a picture (I really am used to hydrogen being red and oxygen green) so it forces me to re-evaluate how I see this gas cloud.