(via APOD: 2012 October 27 - A Halo for NGC 6164)
Image Credit & Copyright: Don Goldman
NGC 6164, though it looks like it is a planetary nebula, is not powered by a star nearing the end of its life. The gas and dust surrounding this star are just parts of the interstellar medium, remnants of the cloud out of which the star probably formed, and are absorbing and then re-emitting massive amounts of radiation from the hot, young O-type star in the middle. It’s actually about half-way through its life already at 3-4 million years, but it is a ways from beginning to throw off its own outer layers.
The image combines narrow band data for the nebular emissions, including the faint halo, and broadband data to capture the starfield.

(via APOD: 2012 October 27 - A Halo for NGC 6164)

Image Credit & CopyrightDon Goldman

NGC 6164, though it looks like it is a planetary nebula, is not powered by a star nearing the end of its life. The gas and dust surrounding this star are just parts of the interstellar medium, remnants of the cloud out of which the star probably formed, and are absorbing and then re-emitting massive amounts of radiation from the hot, young O-type star in the middle. It’s actually about half-way through its life already at 3-4 million years, but it is a ways from beginning to throw off its own outer layers.

The image combines narrow band data for the nebular emissions, including the faint halo, and broadband data to capture the starfield.

(via APOD: 2012 October 25 - The Medusa Nebula)
The Medusa Nebula Image Credit & Copyright: Ken Crawford (Rancho Del Sol Obs.)
Abell 21 is a planetary nebula, the death throes of a low-mass star like the Sun, throwing off the layers left over from giant stages, and, as the star changes into a white dwarf, the ultraviolet radiation causes the gas to glow from ionization and de-ionization.
1500 light-years away in Gemini, the Medusa is about 4 light-years across.

(via APOD: 2012 October 25 - The Medusa Nebula)

The Medusa Nebula 
Image Credit & CopyrightKen Crawford (Rancho Del Sol Obs.)

Abell 21 is a planetary nebula, the death throes of a low-mass star like the Sun, throwing off the layers left over from giant stages, and, as the star changes into a white dwarf, the ultraviolet radiation causes the gas to glow from ionization and de-ionization.

1500 light-years away in Gemini, the Medusa is about 4 light-years across.

(via APOD: 2012 September 29 - NGC 7023: The Iris Nebula)
Out 1,300 light-years, in the direction of Cepheus, the King (who really looks like a kid’s drawing of a house, but don’t mention it to him), is a molecular cloud that may have PAHs, complex carbon molecules. We know for sure, though, that it has given birth to a bright young star, powering this nebula’s glow. The majority is blue, reflected starlight bouncing off the dust and heading our way. However, you can see lovely faint lines of red, where we see evidence of the ultraviolet radiation from the star ionizing hydrogen in the surrounding gas and dust. When it de-ionized, the hydrogen releases a red-wavelength photon.
Gorgeous and scientific all at once, much like its eponymous flower.

(via APOD: 2012 September 29 - NGC 7023: The Iris Nebula)

Out 1,300 light-years, in the direction of Cepheus, the King (who really looks like a kid’s drawing of a house, but don’t mention it to him), is a molecular cloud that may have PAHs, complex carbon molecules. We know for sure, though, that it has given birth to a bright young star, powering this nebula’s glow. The majority is blue, reflected starlight bouncing off the dust and heading our way. However, you can see lovely faint lines of red, where we see evidence of the ultraviolet radiation from the star ionizing hydrogen in the surrounding gas and dust. When it de-ionized, the hydrogen releases a red-wavelength photon.

Gorgeous and scientific all at once, much like its eponymous flower.

(via APOD: 2012 September 24 - NGC 2736: The Pencil Nebula)
Courtesy the awesome folks at @ESO (#ESO50Years), comes this pretty image of the Pencil Nebula.
NGC 2736: The Pencil Nebula Image Credit: ESO
This is the edge of a supernova shock-wave, the Vela supernova (or, perhaps, a younger one that was hard to distinguish from Vela a long time ago, more on that later), and shows the re-ionization of the gasses as they cool after being suddenly compressed and heated by the outgoing shock-wave from the supernova.
This kind of effect will fade, unlike emission nebulae that are powered by stellar winds and radiation, as the material cools slowly. You’ll note there’s a leading and trailing “edge” to the nebula. The blue at the front is hotter oxygen gas that’s begun to cool enough only to allow (in the majority) the oxygen to de-ionize. The red is from hydrogen-alpha emission and is futher “back” in the wave, so it is part of gas that has been cooling for longer. (The shock-wave, in this shot, moves from top to bottom.)
Here’s Hubble’s shot of the Pencil Nebula:

That comes from this great overview of the Vela Supernova from Bill Blair, an astrophysicist at Johns Hopkins.
Trust me, you want to click through and see some of the great x-ray imagery he’s collected together on one page to explain (or problematize) some of the more interesting features of the larger Vela complex of which the Pencil Nebula is a part.

(via APOD: 2012 September 24 - NGC 2736: The Pencil Nebula)

Courtesy the awesome folks at @ESO (#ESO50Years), comes this pretty image of the Pencil Nebula.

NGC 2736: The Pencil Nebula 
Image Credit: ESO

This is the edge of a supernova shock-wave, the Vela supernova (or, perhaps, a younger one that was hard to distinguish from Vela a long time ago, more on that later), and shows the re-ionization of the gasses as they cool after being suddenly compressed and heated by the outgoing shock-wave from the supernova.

This kind of effect will fade, unlike emission nebulae that are powered by stellar winds and radiation, as the material cools slowly. You’ll note there’s a leading and trailing “edge” to the nebula. The blue at the front is hotter oxygen gas that’s begun to cool enough only to allow (in the majority) the oxygen to de-ionize. The red is from hydrogen-alpha emission and is futher “back” in the wave, so it is part of gas that has been cooling for longer. (The shock-wave, in this shot, moves from top to bottom.)

Here’s Hubble’s shot of the Pencil Nebula:

That comes from this great overview of the Vela Supernova from Bill Blair, an astrophysicist at Johns Hopkins.

Trust me, you want to click through and see some of the great x-ray imagery he’s collected together on one page to explain (or problematize) some of the more interesting features of the larger Vela complex of which the Pencil Nebula is a part.

(via Chandra :: Photo Album :: NGC 1929 :: August 30, 2012)
NGC 1929 (star forming region) in N44 (nebular cloud): A Surprisingly Bright Superbubble
Hey all, before I bid you good night (though I wasn’t exactly on this evening, but hey, I had a queue going…for a bit…in the afternoon mostly but you know what I mean…anyway…) I want you to slow your tumblr-scroll for a second and take a look see here. That amazing picture above? That’s an in-depth analysis of an amazing nebular cavity in the Large Magellanic Cloud, one of our Milky Way’s satellite galaxies. What’s going on here is a classic story of a stellar nursery in a dust cloud. When the particles start to create gravitational collection points, they rapidly accrete matter. As the compressed matter pulls in more gas and dust from the surrounding cloud, it also heats up. Continue this process long enough and you start to form a proto-star, then, once the core gets hot enough, and the hydrogen gets friendly enough, you start getting fusion reactions. Suddenly there’s a whole lot of energy at the center that can push back against the force of gravity pulling everything in. A star is born and reaches hydrostatic equilibrium. But the first new stars in an interstellar cloud are often quite massive, burning very hot, which means they throw off a lot of radiation. As this moves out (along with the particles blown out by the nuclear reactions, mostly neutrinos) it creates a stellar wind, which runs right up against the very gas and dust that gave rise to the stars in the first place. This starts to put pressure on the gas cloud, creating new dense points, eventually creating ideal conditions for another generation of stars. These young stars, however, are rather James Dean-ish. They live fast and die young. (And, if you think supernovae are pretty, they also leave a good looking corpse…unless you consider the neutron star to be the corpse, which would also be good looking. I think they’re cool anyway. Oops, digression.)
"So", you say, somewhat bewilderedly, or not, "what’s all that got to do with a weird four-color mosaic of space bubbles?"
I’m glad you asked. Each color is from a different wavelength source. Let’s go through them, and see what they tell us about what’s going on in NGC 1929.

X-ray imaging from the Chandra X-Ray Observatory (a space telescope because x-rays have a hard time getting through our atmosphere…thankfully) shows - in blue - the insanely hot gas (so hot it lights up in x-ray, now that’s energetic!) around the young stars and the where the shockwaves of the supernovae have run into the nebular material.

Infrared imaging from the Spitzer Space Telescope shows - in red - the dust and cooler gas that is glowing from the ultraviolet radiation coming off the stars. UV is not as energetic as x-rays (remember, a longer wavelength = lower energy) and so the light down in the infrared shows those parts of the cloud that aren’t getting superheated.

Optical light from the 2.2m Max-Planck-ESO telescope in Chile shows - in yellow - more of the glowing gas at a lower temperature than the superheated gas, and also gives us our nice background star field.
So, now you see how we learn so much about something so far away by combining the various types of data we can collect at each wavelength on the electromagnetic spectrum.
Buenos noches! Tschuss! Etc.

(via Chandra :: Photo Album :: NGC 1929 :: August 30, 2012)

NGC 1929 (star forming region) in N44 (nebular cloud): A Surprisingly Bright Superbubble

Hey all, before I bid you good night (though I wasn’t exactly on this evening, but hey, I had a queue going…for a bit…in the afternoon mostly but you know what I mean…anyway…) I want you to slow your tumblr-scroll for a second and take a look see here. That amazing picture above? That’s an in-depth analysis of an amazing nebular cavity in the Large Magellanic Cloud, one of our Milky Way’s satellite galaxies. What’s going on here is a classic story of a stellar nursery in a dust cloud. When the particles start to create gravitational collection points, they rapidly accrete matter. As the compressed matter pulls in more gas and dust from the surrounding cloud, it also heats up. Continue this process long enough and you start to form a proto-star, then, once the core gets hot enough, and the hydrogen gets friendly enough, you start getting fusion reactions. Suddenly there’s a whole lot of energy at the center that can push back against the force of gravity pulling everything in. A star is born and reaches hydrostatic equilibrium. But the first new stars in an interstellar cloud are often quite massive, burning very hot, which means they throw off a lot of radiation. As this moves out (along with the particles blown out by the nuclear reactions, mostly neutrinos) it creates a stellar wind, which runs right up against the very gas and dust that gave rise to the stars in the first place. This starts to put pressure on the gas cloud, creating new dense points, eventually creating ideal conditions for another generation of stars. These young stars, however, are rather James Dean-ish. They live fast and die young. (And, if you think supernovae are pretty, they also leave a good looking corpse…unless you consider the neutron star to be the corpse, which would also be good looking. I think they’re cool anyway. Oops, digression.)

"So", you say, somewhat bewilderedly, or not, "what’s all that got to do with a weird four-color mosaic of space bubbles?"

I’m glad you asked. Each color is from a different wavelength source. Let’s go through them, and see what they tell us about what’s going on in NGC 1929.

X-ray imaging from the Chandra X-Ray Observatory (a space telescope because x-rays have a hard time getting through our atmosphere…thankfully) shows - in blue - the insanely hot gas (so hot it lights up in x-ray, now that’s energetic!) around the young stars and the where the shockwaves of the supernovae have run into the nebular material.

Infrared imaging from the Spitzer Space Telescope shows - in red - the dust and cooler gas that is glowing from the ultraviolet radiation coming off the stars. UV is not as energetic as x-rays (remember, a longer wavelength = lower energy) and so the light down in the infrared shows those parts of the cloud that aren’t getting superheated.

Optical light from the 2.2m Max-Planck-ESO telescope in Chile shows - in yellow - more of the glowing gas at a lower temperature than the superheated gas, and also gives us our nice background star field.

So, now you see how we learn so much about something so far away by combining the various types of data we can collect at each wavelength on the electromagnetic spectrum.

Buenos noches! Tschuss! Etc.

(via APOD: 2012 September 9 - Wisps Surrounding the Horsehead Nebula)
Image Credit & Copyright: Star Shadows Remote Observatory
See the little horse-head? That’s the Horsehead Nebula. It’s not exactly a little nebula off by itself. It’s part of a larger molecular cloud complex in Orion.
This show was taken with a very long (7 hour) exposure of hydrogen-alpha in red and overlaid on a broadband (full color) image taken over a 3 hour interval to capture the background star field.

(via APOD: 2012 September 9 - Wisps Surrounding the Horsehead Nebula)

Image Credit & Copyright: Star Shadows Remote Observatory

See the little horse-head? That’s the Horsehead Nebula. It’s not exactly a little nebula off by itself. It’s part of a larger molecular cloud complex in Orion.

This show was taken with a very long (7 hour) exposure of hydrogen-alpha in red and overlaid on a broadband (full color) image taken over a 3 hour interval to capture the background star field.

(via APOD: 2012 September 7 - IC 4628: The Prawn Nebula)
Image Credit & Copyright: Marco Lorenzi (Glittering Lights)
The world seems intent on putting me on a nebulae and cluster kick of late. Yesterday’s APOD shows the Prawn Nebula (IC 4628), just south of Antares, the heart of Scorpio, an emission nebula being powered the nearby hot, massive, young stars. As the ultraviolet radiation streams out from them, it strips electrons off the gas in the nebular cloud, mostly hydrogen, and ionizes it. As the hydrogen atoms reclaim electrons, they release the energy that was initially absorbed when the UV photon hit the atom and knocked the electron off. The resulting radiation is emitted at the wavelengths in the chemical signature of the atoms. As this gas cloud is mostly hydrogen, and the spectrographic signature of atomic hydrogen is largely red, we see mostly red light being emitted.
This is quite a large nebula, too, 250 light-years across, so that, at its distance of about 6,000 light-years, it appears as big as four full moons across on the sky.

(via APOD: 2012 September 7 - IC 4628: The Prawn Nebula)

Image Credit & Copyright: Marco Lorenzi (Glittering Lights)

The world seems intent on putting me on a nebulae and cluster kick of late. Yesterday’s APOD shows the Prawn Nebula (IC 4628), just south of Antares, the heart of Scorpio, an emission nebula being powered the nearby hot, massive, young stars. As the ultraviolet radiation streams out from them, it strips electrons off the gas in the nebular cloud, mostly hydrogen, and ionizes it. As the hydrogen atoms reclaim electrons, they release the energy that was initially absorbed when the UV photon hit the atom and knocked the electron off. The resulting radiation is emitted at the wavelengths in the chemical signature of the atoms. As this gas cloud is mostly hydrogen, and the spectrographic signature of atomic hydrogen is largely red, we see mostly red light being emitted.

This is quite a large nebula, too, 250 light-years across, so that, at its distance of about 6,000 light-years, it appears as big as four full moons across on the sky.

(via APOD: 2012 August 28 - Colorful Clouds Near Rho Ophiuchi)
Image Credit & Copyright: Tom O’Donoghue
Oooh! A lesson in the forms and varieties of nebulae all in one picture. OK, so there are three main kinds of nebulae:
Reflection
Emission
Dark
They’re produced by different processes too, so here’s what’s going on above:
Rho Ophiuchi, the bright blue star in the center of the top blue nebula is emitting regular light that is being scattered off the dust in the nebular clouds. Dust particles tend to scatter blue light more than any other wavelength of light, so the reflected light from the nebula is blue. Hence, reflection nebulae look blue.
To the lower-right, you can see Sigma Scorpii, a bright blue star in the middle of a red nebula. When the ultraviolet radiation from a star hit gas clouds, made mostly from hydrogen, they ionize the gas, stripping the electrons off the atoms. Atoms don’t stay that way forever, though, and they have a tendency to pull an electron back at some point, de-ionizing themselves. When that happens, it releases energy in the form of electromagnetic radiation, usually as red light. We see the light being emitted from the gas as it de-ionizes.
Finally, in all those spots, mostly in the middle of the picture, where you might be worried that the photographer’s camera has some sensing issues, where we’re not seeing any background starlight, or really anything at all, those are areas where there’s too much dust, in the way, making a dark spot in the sky.
Oh, a couple other things:
Big, bright, red supergiant Antares in the lower middle is so red that even it’s reflected light is yellow-red.
M4 is the globular cluster just to right of Antares, an ancient relic of the universe, as are all the globular clusters we’ve ever seen. They orbit the Milky Way and are generally around 12-13 billion years old.
Boy do I love this astronomy stuff.

(via APOD: 2012 August 28 - Colorful Clouds Near Rho Ophiuchi)

Image Credit & Copyright: Tom O’Donoghue

Oooh! A lesson in the forms and varieties of nebulae all in one picture. OK, so there are three main kinds of nebulae:

  • Reflection
  • Emission
  • Dark

They’re produced by different processes too, so here’s what’s going on above:

Rho Ophiuchi, the bright blue star in the center of the top blue nebula is emitting regular light that is being scattered off the dust in the nebular clouds. Dust particles tend to scatter blue light more than any other wavelength of light, so the reflected light from the nebula is blue. Hence, reflection nebulae look blue.

To the lower-right, you can see Sigma Scorpii, a bright blue star in the middle of a red nebula. When the ultraviolet radiation from a star hit gas clouds, made mostly from hydrogen, they ionize the gas, stripping the electrons off the atoms. Atoms don’t stay that way forever, though, and they have a tendency to pull an electron back at some point, de-ionizing themselves. When that happens, it releases energy in the form of electromagnetic radiation, usually as red light. We see the light being emitted from the gas as it de-ionizes.

Finally, in all those spots, mostly in the middle of the picture, where you might be worried that the photographer’s camera has some sensing issues, where we’re not seeing any background starlight, or really anything at all, those are areas where there’s too much dust, in the way, making a dark spot in the sky.

Oh, a couple other things:

  1. Big, bright, red supergiant Antares in the lower middle is so red that even it’s reflected light is yellow-red.
  2. M4 is the globular cluster just to right of Antares, an ancient relic of the universe, as are all the globular clusters we’ve ever seen. They orbit the Milky Way and are generally around 12-13 billion years old.

Boy do I love this astronomy stuff.

(via APOD: 2012 August 5 - IC 1396: Emission Nebula in Cepheus)
Image Credit: Digitized Sky Survey, ESA/ESO/NASA FITS Liberator Color Composite: Davide De Martin (Skyfactory)
In the constellation Cepheus, the King (which actually looks like a child’s drawing of a house when you connect the main stars), IC 1396 glows as the gas and dust within the stellar nursery is radiated by the newly-born stars, especially the big bright one in the center here.
This impressive compilation comes from black-and-white narrow-band shots composited.
They’re all from the Mt. Palomar Observatory down near San Diego.
Adding some extra interesting detail are the obscuring clumps of dust clouds blocking light.

(via APOD: 2012 August 5 - IC 1396: Emission Nebula in Cepheus)

Image Credit: Digitized Sky Survey, ESA/ESO/NASA FITS Liberator 
Color Composite: Davide De Martin (Skyfactory)

In the constellation Cepheus, the King (which actually looks like a child’s drawing of a house when you connect the main stars), IC 1396 glows as the gas and dust within the stellar nursery is radiated by the newly-born stars, especially the big bright one in the center here.

This impressive compilation comes from black-and-white narrow-band shots composited.

They’re all from the Mt. Palomar Observatory down near San Diego.

Adding some extra interesting detail are the obscuring clumps of dust clouds blocking light.

(via APOD: 2012 June 1 - A Sagittarius Triplet)
At the top is NGC 6559, separated from the Lagoon Nebula by a dust lane, with M8 dominating the frame (that’s the Lagoon’s Messier designation), and the multi-colored Trifid Nebula, M20, off to the right.
All three of these are star-forming regions in Sagittarius, the centaur archer shooting his arrow at Antares, the heart of Scorpio. It happens that Sagittarius sits over the central Milky Way, so there is a lot of dust and gas.
As a final bonus, M21, an open star cluster, is sitting just above the Trifid. (The Trifid, in case you are wondering, is named as such because it shows off all three types of nebulae: emission (red), reflection (blue), dark (lack of light, obscured by dust).)
Image Credit & Copyright: Martin Pugh

(via APOD: 2012 June 1 - A Sagittarius Triplet)

At the top is NGC 6559, separated from the Lagoon Nebula by a dust lane, with M8 dominating the frame (that’s the Lagoon’s Messier designation), and the multi-colored Trifid Nebula, M20, off to the right.

All three of these are star-forming regions in Sagittarius, the centaur archer shooting his arrow at Antares, the heart of Scorpio. It happens that Sagittarius sits over the central Milky Way, so there is a lot of dust and gas.

As a final bonus, M21, an open star cluster, is sitting just above the Trifid. (The Trifid, in case you are wondering, is named as such because it shows off all three types of nebulae: emission (red), reflection (blue), dark (lack of light, obscured by dust).)

Image Credit & Copyright: Martin Pugh