The scale of things

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Tiny Galaxy Sparkles in Our Back Yard | Phil Plait
Bad Astronomy | 03DEC12

The diversity of nature constantly surprises me. If you asked me what the first thing I’d think of if you shouted the word “galaxy” at me, it would be something like the Milky Way: a large, disk-shaped pinwheel studded with stars, festooned with bright gas clouds, and splotched with dark dust clouds.

Not all galaxies are like that, though. Some are puffy, some are elongated, some are just weird (technically, classified as “peculiar”). And then there’s ESO 318-38, a nearby galaxy that’s something of an underachiever when it comes to size, but that more than makes up for it in, well, glitteriness:


^ Hubble’s view of the tiny but very pretty galaxy ESO 318-38.
Image credit: ESA/Hubble & NASA

Not much is really known about this galaxy. I searched through the professional journals and found only one paper about it, where the astronomers examined 450 nearby galaxies to determine some of their basic physical characteristics (our friend here is listed as “P32250”, if you’re curious). In this case, we know it’s roughly 20 to 30 million light years away, and pretty small. Judging from its brightness it’s only about 1 percent or less the mass of our Milky Way, and as you can see by the picture, it’s mostly stars! There’s not a hint of gas or dust.

For a moment I was thrown by the stars being all blue, since only hot, young, massive stars are that color. That would be pretty weird, because stars are born from huge gas clouds, and there aren’t any that are obvious in this picture! But then I checked and saw that in this picture, what you see as blue is actually light from the orange/red part of the spectrum. In other words, this is false color. The astronomers used two filters to make this picture, one that lets through only orange/red light (shown as blue), and another that lets through only infrared light (shown as red). Those two colors are useful when you’re looking at stars, and they make for a pretty picture, but you have to be careful interpreting the picture!

So this looks to be an ordinary dwarf galaxy, fairly flat, and otherwise unremarkable except for its beauty.

If you grab the bigger version you’ll notice a couple of things. One is that there are lots of stars scattered across the field. Those are foreground stars, ones in our own galaxy. We’re inside the Milky Way, looking out at ESO 318-38, so nearby stars get in the way—think of it as looking out of a slightly dirty window at houses in the distance.


^ A far more distant galaxy seen
right through ESO 318-38.
Image credit: ESA/Hubble & NASAThe other thing you’ll notice is that the picture is littered with lots of far more distant background galaxies. You can easily spot several dozen, many red and smudgy-looking. One, though, is a face-on spiral we can see right through ESO 318-38! That’s another indication our little friend is mostly stars and doesn’t have much gas and dust. If it did, then that more distant galaxy would be heavily obscured, but as it is we can see it pretty well. So this is like looking out a slightly dirty window to a distant house and seeing through its slightly dirty windows to a house even farther away. Except in this case looking isn’t rude or borderline illegal.

It never occurred to me before, but astronomy is the ultimate in voyeurism. We get to peek in on our neighbors, and it’s totally acceptable! In fact, I encourage it.

The metaphorical cosmic neighbors, I mean. Don’t take me too literally. And if you do, you’re on your own.

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Blowing a Cosmic Bubble | Phil Plait
Bad Astronomy | 05DEC12

The Sun is hardly an average star; by mass it’s in the upper 80th percentile of all stars in the entire Universe. But much, much beefier stars exist, like SAO 20575 (or, if you like these alphabet soup catalog names, it’s also called BD+60 2522). It tips the cosmic scale with at least 15 times the Sun’s mass: It’s a hot, luminous star, so energetic it’s blasting out a fierce wind of subatomic particles that’s actually carving a gigantic bubble in the surrounding material.

That all sounds a bit clinical, until you see a picture of what this awesome power means:


^ The Bubble Nebula as seen by the One Degree Imager.
Image credit: T.A. Rector (University of Alaska Anchorage),
WIYN ODI team & WIYN/NOAO /AURA/NSF

This structure is called the Bubble Nebula, and it is literally a cavity, an evacuated region, left behind as the stellar wind from the star expands. It’s huge, roughly 10 light years across. That’s 100 trillion kilometers (60 trillion miles), hundreds of thousands of times the size of our entire solar system.

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The Labor of Hercules A | Phil Plait
Bad Astronomy | 10DEC12

Black holes may be the most ironic objects in the Universe. They are objects with gravity so fierce that if you venture too close, literally no force in the Universe can prevent you from falling in. Not even light can escape, which is why we call them what we do.

Yet they also power the brightest objects in the Universe. As matter falls in, it forms a disk just outside the black hole that gets infernally hot, blasting out radiation bright enough that it can be seen across the Universe. Not only that, due to forces in the disk like friction and magnetism ramped up to mind-numbing intensities, this disk can focus and blast out two incredibly powerful beams of matter and energy which scream out into space, forming structures both vast and beautiful … like the ones seen in the galaxy Hercules A:


^ Hercules A, a galaxy with a massive black hole blasting out matter.
Image credit: NASA, ESA, S. Baum and C. O’Dea (RIT), R. Perley and
W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Seriously, grab the embiggened version of that. It’s stunning. I’m using it as my computer’s desktop image, in fact. There’s also an incredible 5000 x 3500 pixel version.

In the heart of the galaxy Hercules A is a monster black hole: It’s about 600 times as massive as the black hole in the center of our Milky Way, making it about 2.5 billion times the Sun’s mass. It’s one of the largest known black holes in the Universe, so big we call it “supermassive.”

And it’s hungry. Material is actively funneling down into the maw of that beast, forming a huge disk and blasting out those jets of material you can see in the picture (which is a combination of visible light seen by the Hubble Space Telescope and radio waves—colored pink in the image—detected by the Karl G. Jansky Very Large Array). Focused tightly, those jets march across space at ridiculously high speed, slamming into material around them. Eventually they lose enough energy that they slow and puff outward, forming those twin lobes. When this happens, the material emits light in the radio part of the electromagnetic spectrum. The lobes of Herc A make it one of the brightest sources of radio waves in the entire sky.

The scale of this will turn your brain into goo: Those lobes are well over 1.5 million light years across from tip to tip, 15 times the size of our entire galaxy! And they’re powerful, emitting a billion times the energy our Sun does at radio wavelengths. The energy flowing out of Hercules A is simply insane. In X-rays alone it blasts out 100 billion times as much energy as our Sun does in all wavelengths of light. Replace our Sun with an object that bright and the Earth would vaporize.


^ Artist’s illustraton of the disk around a giant black hole.
Image credit: A. Hobart, CXC

And all of that immensity is powered by the gravity of that black hole, which, massive as it is, is only about the same size as our solar system. The galaxy you can see in the picture, right at the center of the jets, is hundreds of millions of times larger than the black hole itself.

How’s your head? Throbbing yet? I have one more thing to tell you: Hercules A, while being one of the brightest radio objects in the sky, is actually over two billion light years away!

Describing this is getting difficult. I’m running out of adjectives here.

So maybe I’ll just leave you with this: A century ago, we weren’t sure what galaxies really were. Now we have orbiting telescopes, telescopes equipped with amazingly sensitive detectors, and the ability to see across the electromagnetic spectrum such that we can detect these amazing and powerful objects like Herc A. And even more importantly, we’ve built the knowledge in mathematics and physics so that we can study them and even understand them. And we can do it all from a cozy distance of billions of light years, safe and sound, while the Universe thunders around us.

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Hubble Sees Tribe of Galaxies at the Dawn of the Universe | Phil Plait
Bad Astronomy | 12DEC12

An incredibly deep image taken by Hubble Space Telescope has made an amazing discovery: a group of seven galaxies that existed just after the Big Bang itself! One of them may be the most distant galaxy ever seen, a soul-crushing 13.3 billion light years away, and seen as it existed just 380 million years after the Universe itself was born.


^ Hubble’s Ultra Deep Field, with the extremely distant galaxies marked. The most distant is 13.3 billion light years away. Click to embiggen, or grab the very high resolution version. Image credit: NASA/ESA, R. Ellis (Caltech), and the HUDF 2012 team

The image is a result of 100 hours of Hubble staring at one spot in the sky. They chose the location of the previously-observed Hubble Ultra Deep Field (HUDF), a region of the sky where Hubble had already taken a very long look, taking a census of thousands of galaxies at all different distances. This new observation, though, looked in the infrared, where we expect the most distant galaxies to shine most brightly.

The picture above shows the HUDF. The locations of the seven extremely distant galaxies are indicated by colored diamonds; a close-up of each one is shown on top (click the image to get a high-res version). The number listed with each galaxy is a measure of its distance using its redshift: Because the Universe is expanding, more distant galaxies appear to move away from us faster than nearby ones. That can be used (with some fairly complex physics) to determine the distance to each galaxy. I explain this technique in more detail in an earlier post about redshifts.

The redshift is noted by the letter z, and the bigger the number, the farther the galaxy. A z of 8.6 is a galaxy about 13 billion light years away. The most distant galaxy seen was at a redshift of 11.9, which means the light we see from it left a whopping 13.3+ billion light years ago. Since the Universe is 13.7 billion years old, this means we are seeing this galaxy as it was only about 380 million years after the Big Bang. That’s a stunning observation.

Let me be clear: These distances are not confirmed. They should be pretty solid, though. The only way to be sure is to take a spectrum of each galaxy, breaking its light up into thousands of different wavelengths (colors) and carefully analyzing them. For this new discovery, astronomers examined the light of each galaxy using different filters instead, which is quite accurate, but not exact. I’ve used this method myself, and it’s pretty good, so I suspect these numbers will hold up.

The reason this observation is important is that we know very little about what galaxies were like so far back in time. Galaxies like our Milky Way are big, sedate, and fully-formed, but that wasn’t always the case. When the Universe was only a few hundred million years old, there were no galaxies; they were just starting to form. The first stars forming from vast clouds of gas would, we think, be extremely massive—well over 100 times more massive than the Sun—and very hot. They would’ve flooded the Universe with ultraviolet light, making the surrounding gas glow at a very specific color in the UV. These baby pictures of the seven galaxies tell us what those conditions were like back then, including potentially how many of these ginormous stars existed at the time.


^ Closeup of some of the distant galaxies seen in the Hubble Ultra Deep Field. They are much easier to see in the higher-resolution version of this image. Image credit: NASA/ESA, R. Ellis (Caltech), and the HUDF 2012 team

One big result is that it looks like these stars didn’t suddenly all turn on at once everywhere, but instead this took some time to unfold. Galaxies grew rather slowly, and stars formed at different times. Interestingly, that farthest galaxy may be not just the most distant galaxy Hubble has seen, but the most distant one it can see. Even cooler, this baby galaxy appears to have been already chugging along, clearly born some time even earlier than we see it here. It seems likely that with a bigger telescope that has sharper vision in the infrared, we’ll see many more of these galaxies, and a handful even farther away (and therefore younger).

Mind you, Hubble was pointed at what was essentially an “empty” region of the sky, chosen specifically because it was boring, lacking previously visible objects. But with Hubble’s sharp, sensitive vision, thousands of galaxies billions of light years away appear, and when it’s seriously focused on one spot it can see all the way to the thin hairy edge of the Universe.

And yet even this isn’t all we can do. With James Webb Space Telescope, due for launch in a few years, we’ll do even better. It has a bigger mirror, more sophisticated cameras, and is tuned specifically to look in the infrared. This little tribe of baby galaxies is just the first taste of what’s to come.

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I LOVE the video at the bottom. The zoom onto
the nebula is s-l-o-w, rather like drawing you
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Behold! Hubble’s Heavenly Holiday “Ornament”
Universe Today, Jason Major | 18DEC12


^ Planetary nebula NGC 5189 as seen by Hubble’s Wide Field Camera 3.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

It may be just a tad too big to hang on your tree but this bright, twisted planetary nebula would make a beautiful holiday ornament… if scaled a bit down to size, of course.

NGC 5189 is a planetary nebula that lies 1,800 light-years away in the southern constellation Musca. The gorgeous image above, acquired by Hubble’s Wide Field Camera 3 on October 8, 2012, shows the glowing streamers of oxygen, sulfur and hydrogen that are being blown far into space from the hot star at its heart — HD 117622 (at right.)

The expelled gas forms a double structure, with a series of central blue lobes surrounded by a twisted helix of bright streamers, called radial filaments. These filaments are the result of fast-moving material from the star impacting previously expelled, slower-moving gas, which becomes visible due to ionizing radiation.

The twisted shapes — as opposed to the circular or spherical structures found in many planetary nebulae — may be the result of an unseen binary partner to HD 117622, which over time would affect its rotational orientation.

“The likely mechanism for the formation of this planetary nebula is the existence of a binary companion to the dying star,” said scientist Kevin Volk in a Gemini Observatory article from 2006. “Over time the orbits drift due to precession and this could result in the complex curves on the opposite sides of the star.”

The surrounding stars in the image were captured in visible and near-infrared light.

Read more on the Hubble site here, and check out a video below that zooms into the region of the sky where NGC 5189 is located:

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One of the Largest Astronomical Images Ever Made
Universe Today, Jason Major | 18DEC12


^ The northern portion of the Cygnus Loop, as seen in an enormous new
panorama from the National Optical Astronomy Observatory (NOAO) and
WIYN partners

Looking for a stunning new desktop image to wrap up the year? Try this: it’s an amazing panorama of the Cygnus Loop, a supernova remnant located 1,500 light-years away in the constellation (you guessed it) Cygnus. The full-size image, acquired with the wide-field Mosaic camera on the WIYN 0.9-meter telescope at Kitt Peak, Arizona, is a staggering 600 million pixels in size — over 1.68 gigabytes — making it one of the largest astronomical images ever made!

See the full image (and links to download larger versions) below:


^ 2000-pixel-wide version of the full Cygnus Loop panorama

The entire structure of the Cygnus Loop, the gaseous remains of a supernova that occurred 5,000 – 10,000 years ago, covers an area nearly 45 times the size of the full Moon in the sky.

In the image, hydrogen alpha, sulphur, and oxygen ions correspond to the red, green, and blue color values, respectively.

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The Top Astronomy Pictures of 2012 | Phil Plait
Bad Astronomy | Wednesday, 19DEC12


^ The Top Astronomy Pictures of 2012: Click to go to the gallery.
Image credit: NASA/JAXA/Hinode/Phil Plait

Astronomy is a beautiful science.

I mean that literally and figuratively. Of course, astronomy is literally telling us our place in the Universe, how everything works, how it fits together … and it’s done on the grandest of scales. There’s a beauty in the tapestry of the cosmos.

But it’s also just beautiful. Nebulae, galaxies, stars, planets, aurorae; from the near sky to the most distant realms, the Universe is filled to overflowing with pure, simple beauty.

That’s why, every year, I gather together my favorite images taken over the past twelve months and present them to you, my readers. It’s a difficult task, winnowing down the thousands of pictures taken of the sky that I’ve seen, gathering them into groups, picking the best of the best, and then putting them together. It’s a tough but admittedly joyful process: I’m sifting through gorgeous depictions of the science I love! And in the end I have a collection of polished gems to share with you. I pick them for their beauty, of course, but also for their remarkableness, their outstanding nature. Something different, something unique, something just plain cool.

This year, as always, we had an amazing crop of pictures from all over—and above—the world. So, from our Earth’s atmosphere to quite literally the very edge of the observable Universe, may I present to you: The Top Astronomy Pictures of 2012.

I hope you enjoy them as much as I do.

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Music is usually distinctly audible, but for these few moments, it’s neither distinct nor audible. I’ve been starring at the first photo below of the star Zeta Ophiuchus for several minutes. Music is in that image! It’s beautiful to me. I’d express it better if I were a poet.

Happy Holidays to All.

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Happy Holidays from the Whole Universe | Phil Plait
Bad Astronomy | Tuesday, 25DEC12

I was wondering what to post for today; a short philosophical piece, a longer discussion of holidays and family, a pretty picture, or something quick and funny.

Then the Universe delivered unto me a picture perfect present: Behold!


^ The massive star Zeta Oph making waves.
Image credit: NASA/JPL-Caltech

Trust me, you want to see this bigger! This is a Spitzer Space Telescope view of the star Zeta Ophiuchus (or Zeta Oph to its friends), a massive star plowing through the gas and dust floating in space. Zeta Oph is a bruiser, with 20 times the Sun’s mass. It’s an incredibly luminous star, blasting out light at a rate 80,000 times higher than the Sun! Even at its distance of 400 light years or so, it should be one of the brightest stars in the sky … yet it actually appears relatively dim to the eye.

That’s because it’s sitting in a dust cloud, dense opaque material that absorbs the light from the mighty star and diminishes it. However, infrared light can penetrate the murk, allowing us to peer into the cloud and see what’s going on.

Zeta Oph is blasting out a fierce wind of subatomic particles (think of it as a super-solar wind) that expands around the star. Not only that, but the star itself is moving rapidly through the dust at a speed of about 25 kilometers per second (15 miles per second), so it’s violently compressing the material ahead of it. This creates that wave structure, which is similar to the wave off the bow of a boat, though more like the supersonic shock wave generated as a fighter jet screams through the air.

That curving wave is roughly four light years long: That’s 40 trillion kilometers! The colors we see here represent different wavelengths of infrared light, well outside what the human eye can see, but are very clear to the Spitzer telescope, designed to see this flavor of light.


^ Zeta Oph as seen by NASA’s
WISE spacecraft. Image credit:
NASA/JPL-Caltech/UCLAI love this shot; if it had been released just a week earlier, I would’ve included it in my list of the Best Pictures of the Year! In fact, an image of it from WISE, another infrared ‘scope, did make my Top Pictures list in 2011.

This is one of my favorite objects of all time, so it was easy to decide to post it today. And c’mon: It’s red and green, and is literally wrapped in bow. How could I resist?

The Universe is simply amazing, and is the gift that keeps on giving. Enjoy your holidays, folks.

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The Milky Way’s Old (and Huge) Faithfuls | Phil Plait
Bad Astronomy | Thursday, 03JAN13


^ Combined optical and radio image of two huge eruptions of material flowing out of the Milky Way galaxy. Combined optical and radio image of two huge eruptions of material flowing out of the Milky Way galaxy. And you very much want to click it to embiggen. Image credit: Ettore Carretti, CSIRO (radio image); S-PASS survey team (radio data); Axel Mellinger, Central Michigan University (optical image); Eli Bressert, CSIRO (composition).

The Milky Way galaxy—our home galaxy—is erupting. Two monumental geysers are blasting out of its heart in opposite directions, and astronomers recently got the clearest view of them ever seen.

The image above shows the Milky Way in visible light, as we see it on a very dark night—stars, gas, and dust strewn across the sky. Superposed on that is the radio emission from those vast winds of material blasting outward (which is invisible to the eye; it’s colored blue so you can see it). Those radio waves were detected by the Parkes radio telescope in Australia. These winds been seen before using both radio telescopes and Fermi, an orbiting observatory that detects gamma rays (the highest energy form of light), but only at low resolution. Until now they haven’t been mapped so clearly and in such detail.

The scale of this image is difficult to grasp. I’ve cropped it here to let you see the structures, but if you look at the original image it shows the whole sky…and you can see these eruptions of matter are so vast they stretch across two-thirds of the entire sky!

I’m actually rather stunned at this. If you had radio-vision, and you could see these streams of matter, you’d have to physically turn around to see the whole thing end-to-end. In real numbers, the material is about 50,000 light years long—half the length of the galaxy itself—and is rushing away from the center of the galaxy at a mind-numbing 1000 kilometers per second!

When I read that, the hair on the back of my neck stood up. My first thought was, “What the frak could power something that vast?”

And then I found out: the geysers contain the energy equivalent of a million exploding stars!

At that point I may have blacked out for a moment or two. If you want to know what humbles an astronomer, then this is pretty much your go-to scenario.

It’s hard to express the colossal nature of this. Think of it this way: Take all the energy the Sun emits every second (enough to power the entire Earth’s needs for nearly a million years). Now multiply that by 31 million, the number of seconds in a year. Now multiply that by 10 billion, the numbers of years the Sun will be around. It’s a huge number, staggering, and that’s still only about 1% of the energy output of a single supernova. That means these geysers contain a hundred million times the Sun’s entire lifetime supply of energy.

See? That’s why I was overwhelmed.

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Milky Way, Meteor, Meteorology | Phil Plait
Bad Astronomy | Wednesday, 26DEC12

Photographer Randy Halverson is good. Very, very good. So much so that I picked one of his shots to go in my gallery of the year’s best astrophotos.

But had I known about this picture, I might’ve picked it instead:


^ Storm, sky, and shooting star over South Dakota.
Image credit: Randy Halverson, used by permission

Click that to embiggen it! When you do, you’ll see why I like it. The Milky Way glows over the landscape, the combined might of billions of stars, their vast distance reducing their luminosity to a mere whisper. In the foreground a storm rages, lightning illuminating the clouds to a red and purple glow.

And above it, apparently attempting to connect the two, the brief flash of a shooting star: A bit of cosmic debris no bigger than a grain of sand, heated to luminescence by its tremendous speed as it rams through our air.

As an added bonus, on the right is the ruddy glow of Antares, a red supergiant star that marks the heart of Scorpius, the scorpion. One day that star will explode, and from its distance of only about 500 light years it will shine about as bright as the full Moon! But that may not happen for hundreds of thousands of years.

I love the sense of scale in this shot: The clouds a few kilometers away, the meteor a few hundred, Antares a few thousand trillion, and the merged stars of our galaxy deep in the background, a hundred thousand trillion kilometers further yet.

If there’s one thing I love about astronomy—and there are far more, I assure you—it’s the sheer size of it. From here to eternity, indeed.

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The Wobbly Beam of the Vela Pulsar | Phil Plait
Bad Astronomy | Tuesday, 08JAN13


^ Image credit: X-ray: NASA/CXC/Univ of Toronto/M.Durant et al; Optical: DSS/Davide De Martin

The Universe is a weird place. I mean, seriously, how else would you describe something like the Vela pulsar? It used to be a massive star, far larger than the Sun. Then it exploded, blasting away an octillion tons of debris at high velocity. But even as the outer layers blew away, the core collapsed. Enough material to make an entire star like the Sun got squeezed down into a tiny ball just a few kilometers across.

This neutron star, as this object is called, is a place of mind-crushing extremes: a surface gravity billions of times that of Earth, a temperature in the millions of degrees, and a magnetic field billions of times Earth’s as well. And it spins, oh, how it spins, that entire mass whirling madly more than 11 times every second!

And we’re not done: All of these forces combine to generate two beams of matter of energy that scream away from the poles of the star, blasting outward at 70 percent of the speed of light! That’s fast enough to get to from the Earth to the Moon in two seconds flat, in case you were still not flabbergasted by all this. New observations of this beam indicate it’s not steady, either. It appears to make a corkscrew pattern every 120 days as it floods away from the pulsar. Here’s a video made from the observations:

Isn’t that bizarre? What we think is happening is that the pulsar is wobbling as it spins. If you’ve ever spun a top, you’ve seen that as it slows down it starts to wobble, the axis making a slow circle even as the top itself continues to spin. This is called precession, and happens when a spinning object has an off-center force on it. For the top, it’s friction with the floor. For a pulsar, it could be that the material in the star is a bit off-center, making it lopsided, throwing off the spin. But whatever the cause it, it forces the axis of the pulsar to make that slow wobble once every 120 days or so.


^ The Vela pulsar looks a bit
like Brak from Space Ghost.
Image credit: X-ray: NASA/
CXC/Univ of Toronto/M.Durant
et al; Optical: DSS/Davide De
Martin; Cartoon NetworkThe observations to make the animation were from the Chandra X-ray Observatory. The material blasting away from the star is so hot it generates X-rays which can be detected from Earth. It’s amazing, even from a distance of 1000 light years, that you can easily see the emission from the pulsar in the center, the beam itself, and the gas near the pulsar being heated up by the fierce wind of subatomic particles from the star—that gas actually looks a bit like a distorted face, doesn’t it? I keep thinking it looks like Brak from Space Ghost.

I’ll note that the reason we call this a pulsar is because at some wavelengths of light (usually radio, but also sometimes visible light as well) the neutron star sweeps a hot spot around as it spins, toward and away from the Earth, like the beam of a light house. When it’s on the side facing us we see a blip of light, and when it turns to the other side we see the light dim. This happens several times per second for many of these objects—making the term “pulsar” fairly apt.

I’ve been fascinated by pulsars and neutron stars since I was a kid. I mean, seriously: it’s the mass of an entire star, and it spins a dozen times per second. Some are even faster; millisecond pulsars spin hundreds of times per second, faster than the blades on a kitchen blender! And it’s a whole freakin’ star!

Like I said: The Universe is a weird place. But it’s fun, isn’t it?

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The Orion Nebula as You’ve Never Seen it Before:
Jaw-dropping New Image from Gemini
Universe Today, Nancy Atkinson | 09JAN13


^ This image, obtained during the late commissioning phase of the GeMS adaptive optics system, with the Gemini South AO Imager (GSAOI) on the night of December 28, 2012, reveals exquisite details in the outskirts of the Orion Nebula. Gemini Observatory/AURA

This is the part of the Orion nebula. Recognize it? You may not, as this stunning new image comes from the Gemini Observatory’s recently-commissioned advanced adaptive optics (AO) system named GeMS. It shows clumps of gas ejected from deep within the Orion Nebula which are nicknamed ‘Orion Bullets.’

“The combination of a constellation of five laser guide stars with multiple deformable mirrors allows us to expand significantly on what has previously been possible using adaptive optics in astronomy,” said Benoit Neichel, who currently leads this adaptive optics program for Gemini. “For years our team has focused on developing this system, and to see this magnificent image, just hinting at its scientific potential, made our nights on the mountain – while most folks were celebrating the New Year’s holiday – the best celebration ever!”

The team took the image on December 28, 2012.

About five years ago, astronomers took an image of the Orion Bullets using a previous version of adaptive optics called Altair. Gemini’s instrument scientist for Altair, Chad Trujillo, pointed out that in one shot GeMS covers a significantly larger field-of-view than Altair and a higher quality image.

“The uniformity and performance across the image is amazing! In this new image, the pixels are 2.5 times finer and there are about 16 times more of them,” he said. Both the correction quality and the field-of-view are considerably better than the previous generation of AO systems.”


^ Detailed views of the Orion Bullet region.
In each image pair, left is the Altair 2007 image and
right is the new 2012 GeMS image. Credit: Gemini
Observatory/AURA

Read more about the GeMS system at the Gemini Observatory website.

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Behold: The Largest Known Spiral Galaxy
Universe Today, Nancy Atkinson | 10JAN13


^ This composite of the giant barred spiral galaxy NGC 6872 combines visible light images from the European Southern Observatory’s Very Large Telescope with far-ultraviolet (1,528 angstroms) data from NASA’s GALEX and 3.6-micron infrared data acquired by NASA’s Spitzer Space Telescope. Credit: NASA’s Goddard Space Flight Center/ESO/JPL-Caltech/DSS

Astronomers have long known that a spectacular barred spiral galaxy named NGC 6872 is a behemoth, but by compiling data from several space- and ground-based observatories and running a few computer simulations, they have now determined this is the largest spiral galaxy we know of.

Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy.

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