This is the iconic North America Nebula, named for what should be an obvious reason: its remarkable resemblance to the continent, complete with Florida and the Gulf of Mexico!
Located in Cygnus, it's high in the sky near the bright star Deneb for northern hemisphere observers in the summer. I've seen this myself; it's big enough to spot with binoculars from a very dark site. The shape can difficult to see that way, but really pops out in pictures.
The image above is a combination of infrared shots by Spitzer (red and green) and visible light images taken as part of the Digitized Sky Survey is included (blue). As you can see it's the visible light that creates the illusion of North America.
Note how the "Gulf of Mexico" region is very dark; dust is quite thick there, blocking visible light. As it turns out, this is also where stars are busily being born, as you'll see in the next image in the gallery...
Original press releaseImage credit: NASA/JPL-Caltech/L. Rebull (SSC/Caltech)
I had to laugh when I saw first this image: it shows Spitzer's view of the famous North America Nebula, renowned because of its resemblance to the continent... when seen in visible light. But the glowing gas seen by our eyes is nearly invisible in the infrared, where dust rules supreme. So this Spitzer picture was something of a shock to me (the previous picture in the gallery is to the same scale and shows the shape more clearly, where the visible light view is combined with an IR picture ).
I also had to smile because this image was taken by my old friend Luisa Rebull, who studies young stars. Clouds like the North America Nebula churn out stars, but in visible light they're mostly hidden by dust. Only about 200 baby stars were known before Spitzer took a look, but Luisa has found more than 2000!
You can see some of them yourself in the picture; look to the left and just below center. There are dark features there studded with very red dots: those dots are young stars! The dust littering the cloud absorbs the visible light from the stars, but lets through the far-infrared, color coded as red in this picture. In visible light, this is the "Gulf of Mexico" region which defines the continental resemblance of this nebula.
You can also see the wispy pillowy structures surrounding the cloud, where winds of subatomic particles and the flood of ultraviolet light from the young stars eats away at the material there. In visible light the dust makes the iconic shape that our brains perceive as that of a continent, but it's in the infrared where the underlying science really shines.
Original press releaseImage credit: NASA/JPL-Caltech/L. Rebull (SSC/Caltech)
The Milky Way, our home galaxy, has two small irregular satellites: the Large and Small Magellanic Clouds. Visible to the southern hemisphere observers with just the naked eye, they look like two fuzzy patches hanging in the sky (I've seen them myself, which was an extraordinary experience).
But they are entire galaxies in their own right! This Spitzer image of the Small Magellanic Cloud (SMC) allows astronomers to study the stars and dust in infrared, so they can trace the life cycles of stars as they are born, grow old, and die. The SMC is a place of active star birth and death, so it's loaded with dust across its entire body.
Having a galaxy so close and open to observation is, for astronomers, like having a fully-stocked lab sitting in space. By studying the SMC we learn about all types of stars at all points in their lives, including stars like our Sun. I always get a thrill knowing that by looking out, away from our home, we get to learn more about our own galaxy, our own star, and ourselves.
The Orion Nebula is one of the most famous objects in the entire night sky. It can be seen as the fuzzy middle star in Orion's dagger, and even with binoculars reveals itself to be a cloud of gas and dust.
I've spent many hours myself gazing at this nebular masterpiece through a telescope. Even my relatively modest 'scope lets me see wisps of gas, brilliant stars, and gives me a glimpse of the overall structure of this vast cloud.
And Spitzer shows us this same view, but differently: in infrared, the dust which blocks our visible view is seen to glow, revealing the structure underneath: an enormous complex of cold molecular gas, dust, and stars. It's one of the galaxy's biggest star-forming factories, and Spitzer can trace the filaments and ribbons of dust, slammed by stellar winds and the fierce light of hot, massive, newborn stars.
The Orion Nebula is one of the largest star birth factories in our galaxy, easily seen to viewers in other galaxies (assuming there are any). It's a wonderful circumstance that we have front-row seats to it - it's a mere 1350 light years away or so, making it the nearest such large-scale structure. It's a fantastic opportunity for astronomers to learn so much about how stars are formed... but it also serves to simply allow us to look upon it and soak in its beauty.
700 light years away in the constellation of Aquarius lies the Helix nebula, the expanding shell of gas from a dying star. This nebula is huge, 2.5 light years across, and so close that it's roughly the same size as the full Moon in the sky!
Spitzer's ability to see in the infrared becomes critical here; even though this is a well-studied nebula, this view of IR light invisible to our eyes reveals something never seen before in the Helix: a circular disk of dust surrounding the star (seen as the red circle immediately outside the star). Astronomers think this dust may have come from trillions of comets that orbited the star; they would've been vaporized when it expanded into a red giant.
The tendrils on the outer ring ironically look like comets but are actually caused when the hot, fast stellar wind from the central star caught up and collided with a slower, denser wind ejected earlier by the star. The gas fragmented in the collision, forming clumps, which erode away and blow off those long tails as the hot wind eats into them. To give you a sense of scale, each one of those clumps is bigger than our solar system, and the tails are a hundred billion kilometers long!
NGC 1097 is a magnificent barred spiral galaxy 50 million light years away. In this false-color image (like they all are from Spitzer, since infrared is invisible to the human eye), stars shine blue and red is the glow from dust.
Unlike many galaxies, this one has star formation actively ongoing in its heart; you can see it as the red ring glowing smack dab in the galaxy's middle. That's dust generated from the stars as they are born. Jutting out from that ring are two faint linear arms which connect to the elliptical ring of dust; again these are loctions of active star birth. Finally, surrounding those, are two long spiral arms stretching out for tens of thousands of light years.
Interestingly, the arm on the left breaks up, seemingly right around that elliptical galaxy. I would've thought that was a distant background galaxy, but I wonder. I've not been able to find any information about it, and its location might just be a cosmic coincidence.
The spiral arms of our Milky Way galaxy are studded with clouds of gas and dust called nebulae. GL490 is one such nebula, and inside stars are busy being born.
In this image, a combination of Spitzer shots with those from the infrared survey 2MASS, what you see as green is light emitted from molecules called PAHs, or Polycyclic Aromatic Hydrocarbons... soot! These long-chain carbon molecules are opaque in visible light, but are warmed by the nearby stars to temperatures of about 100K. That's about -170 Celsius, or -280 Fahrenheit! So maybe "warm" isn't the best word, but to an infrared astronomer that's about right.
The hi-res version of this picture reveals stunning details, including newborn stars shooting out long jets of gas (you can see one here just above and to the right of the yellowish star in the center). I'd also urge you to take a closer look at the yellow patch at top center; that is where dust is reflecting infrared light from a nearby star. The filaments, sheets, and tendrils in that area are simply stunning.
NGC 6240 is a galaxy. Well, almost a galaxy: it's actually two galaxies that have collided and are well on their way to merging and becoming one galaxy.
When two galaxies collide like this, it's very rare for stars to physically smack into each other. But the gas and dust clouds are light years across, and encounters are inevitable (resistance, as they say, is futile). When they do the protean galaxy undergoes a burst of star formation, blasting out light and creating scads of dust.
This image, like the galaxies that make it, is the merging of two shots from Spitzer (colored red) and two from Hubble (green and blue). The red is dust, and you can see how turbulent and chaotic the collision is. In a few million more years the action will be over, and what will remain is a single, large galaxy. Our own Milky Way probably suffered several collisions like this in its 12-billion-year history.
Globular clusters are magnificent balls of millions of stars packed into a relatively small, roughly spherical volume. And Omega Centauri is the grand daddy of them all, so huge and relatively close that it can be seen with the naked eye.
Omega Cen is also very old, and a lot of the stars in it have aged to the point where they have become red giants. This image is a combination of visible light taken with a 4-meter telescope in Chile (colored blue) combined with images from Spitzer (green and red).
Stars like the Sun - still happily churning away, fusing hydrogen into helium in their cores - appear blue, but the red and yellow stars are older, and have become red giants. These stars are well on their way to dying, as our own Sun will... in another 6 billion years or so.
This is one of my favorite Spitzer images of all: W5, a gas cloud 6000 light years away in Cassiopeia. To give you an idea of the scale, the full Moon could fit three times across this image!
What looks like a Valentine's Day heart to us is actually a gigantic cavity more than 150 light years across, carved out by the intense winds and ultraviolet light of the stars forming inside it. The fingers of material on the edges are being eroded away by those stars like sandbars in a current, and so they point right back to those stars' locations.
Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA
Spiral galaxies make beautiful targets in the infrared. Dust, normally opaque and dark in visible light, comes alive in the IR. M66 is a bright, nearby, barred spiral galaxy. In this Spitzer image, the arms of the galaxy are littered with dust, formed when stars are born and when they die. This happens primarily in the spiral arms, which is why the cold dust there is obvious (seen here in red). The inner region of the galaxy is very old, and star formation there ceased ages ago.
At 35 million light years away, M66 is an easy target for small telescopes, and is one of the best-studied galaxies in the sky. But images like this from Spitzer provide new insights into how galaxies form and maintain their shape. In astronomy, there's no such thing as "having seen it all". Whenever new eyes are used to peer upwards, we learn new things.
This lovely image shows the region of sky around the star Rho Ophiuchi, an area of the galaxy rich in gas and dust. This star forming factory is only about 400 light years away, making it one of the closest and best-studied objects in the sky.
Blobs of gas light years across are visible, as well as wisps and sharp shock fronts as stellar winds from new stars slam into the surrounding material. Much of this is blocked from view to visible light telescopes due to the dust, but Spitzer peers through that veil to see what lies underneath. Young stars still shrouded in dust appear red in this image, while older stars that have blown away their birth cocoon appear bluer.