Category: General

Chance Alignments

NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama)

As huge as the Universe is, chance alignments between galaxies often happen as in this image of NGC 3314 from the NASA/ESA Hubble Space Telescope.

Zoom into the spiral arms of these two galaxies. What stories or pictures do you see? Leave a note in the comments below.

Looking close at these two galaxies and it appears they are colliding. But it’s just a trick of perspective. The galaxies are in a line from our vantage point although between them there are millions of light-years of nothingness. Scientists looking at the image looked at the shapes of the galaxies to help determine whether the two are interacting. Usually the huge tug of gravity in a galaxy pushes and pulls the spiral arms of another galaxy until it is warped. Like soft taffy, gravity can stretch and squish a galaxy. Spiral arms get bent or stretched into long tails that appear to fly off into space.

One thing this alignment allows is for astronomers to study in detail the spiral arms of the galaxy in front. The dark dust lanes of NGC 3314A stand out clearly in the light of NGC 3314B in the background. Zoom into these dust lanes. NGC 3314A has many hot, young blue stars in the outer reaches of its spiral arms. If we look to the right of this galaxy, it does appear warped and full of new stars. This does point to an encounter with another galaxy in the past.

Look also for many other galaxies dotting the background of the image. These galaxies are hundreds of millions of light-years beyond this pair.

NGC 3314A lies about 117 million light-years from Earth toward the constellation Hydra, the snake. NGC 3314B is a bit farther away at 140 million light-years. Astronomers determined in 1999 that this galaxy was actually two separate galaxies.

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Lollipops and a Wreckage of Stars

NASA, ESA and the Hubble SM4 ERO Team

Galaxies with twisted arms that resemble swirled lollipops come together in a huge stellar wreck in this image from the NASA/ESA Hubble Space Telescope.

What shapes or stories do you see in this image of Stephan’s Quintet? Leave a note in the comments below.

Stephan’s Quintet, also known as the Hickson Compact Group 92, is a collection of five galaxies. Four of the galaxies are interacting. The galaxy in the upper left, NGC 7320, is actually seven times closer to Earth than the others. Zoom into its blue spiral arms. Bursts of star formation are apparent throughout this galaxy with new blue stars and pink nebulae dotting the scene. These nebulae resemble the Orion Nebula and they are star factories. NGC 7320 is a dwarf galaxy just 40 million light-years from Earth. By contrast, light traveling about six trillion miles per year, has zipped along for more than 300 million years from the redder galaxies in the group. The color of these galaxies is much redder either because the stars are older or because of dust stirred up by the interactions.

Starting at the upper right, NGC 7319 is a barred spiral galaxy. The distinct spiral arms nearly encircle the bar. Huge clusters of stars make red and blue dots surrounding the galaxy. The spiral arms of this galaxy are beginning to show the effects of interactions with the other galaxies.

Moving clockwise, the next galaxy looks like a single galaxy. But zoom in close and you’ll see it has two cores. NGC 7318A and NGC 7318B are trapped in each others gravity embrace. Zoom into this galactic merger’s dark dust bands, bright blue star clusters and pinkish clouds of glowing hydrogen. These clouds of gas and dust are the birthplace of new stars and are less than 10 million years old. To the right of these galaxies lies an area of star cluster formation. Gravity interactions has flung this spiral arm away from the main galaxy.

The bright elliptical galaxy at the bottom is called NGC 7317. Zooming in close to this galaxy and we see that it is fairly normal looking. As the galaxies move closer together, this galaxy will become warped and stretched.

Scattered throughout the image, look deep for dozens of faraway galaxies.

French astronomer Edouard M. Stephan discovered the group in 1877. Stephan’s Quintet resides in the constellation Pegasus, the mythical winged horse. It is the first compact group of many that have been discovered.

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Dust on the Edge

ESA/Hubble & NASA

Dust reddens the starlight along the edge of NGC 891 in this image from the NASA/ESA Hubble Space Telescope.

Explore this close-up zoom of the spiral galaxy seen edge-on. What stories or shapes do you along the edge of the galaxy? Leave a note in the comments below.

NGC 891 spans about 100,000 light-years. This view is similar in many ways to our view of the Milky Way as it arcs across the night sky. The biggest difference however is that we see our dust-filled plane of our galaxy from the inside from about 10,000 light-years. Using Hubble’s powerful telescope we gaze into NGC 891 from a distance of about 30 million light-years. The bright galactic central bulge lies just off image at the bottom left. Zoom into the tendrils of dust set against the bright backdrop of the galaxy. Scattered throughout these filaments are areas of blue mist. These are areas of new star formation. Astronomers believe too that supernovae explosions scatter the dust, clearing out vast sections of space and pushing dust into dense pockets where more new stars can form.

NGC 891 is found toward the relatively open constellation of Andromeda, the mythical daughter of Cassiopeia and Cepheus. A few foreground stars from the Milky Way galaxy are seen blazing brightly in the image. Look also for distant elliptical and spiral galaxies scattered throughout the image.

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Ripples and Shadows

NASA/JPL/University of Arizona

Ripples, dunes and shadows create swirling and looping patterns in this image from the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter.

Explore the sprawling Martian dunefield. What stories and patterns do you see? Leave a note in the comments below.

Scientists use images like this one to not only study wind processes on Mars but also to look for fresh impact craters. From time to time, HiRISE takes images of the same part of the Red Planet giving scientists a chance to see what has changed between images. Scientists are not sure whether Martian dunes have evolved over thousands of years or if they are young features. Dunes in this image appear fresh and young. They have sharp crestlines (top of dunes) and active looking slipfaces (downwind slopes of dunes). Most of the dunes point toward the southwest which shows the predominant wind direction in this area. But some dunes show signs of sand being pushed back up the slope making the slopes smooth with few ripples. A quick look around the image shows that no impact craters are present. More dune fields are left to explore.

Launched with MRO in 2005, HiRISE is one of six instru­ments aboard the space­craft orbit­ing Mars. HiRISE’s cam­eras can see objects on the sur­face as small as a beach ball. The cam­era also offers sci­en­tists stereo views of the surface.

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Galaxies in the mist


Faraway galaxies glow through a starry mist as it angles across this image of NGC 2366 from the NASA/ESA Hubble Space Telescope.

Explore the bright star-forming nebula, blue dots and galaxies in this image. What stories or pictures do you see? Leave a note in the comments below.

NGC 2366 is a small dwarf galaxy hanging out only about 10 million light-years from Earth toward the constellation Camelopardalis, the Giraffe. The closest large galaxy is the Andromeda Galaxy, two million light-years away. NGC 2366 is about the same size as two closer and more familiar dwarf galaxies to the Milky Way; the Large and Small Magellanic Clouds. They lie just 170,000 light-years from Earth. But like the Magellanic Clouds, NGC 2366 lacks the internal structure of galaxies like our home, the Milky Way, and the Andromeda Galaxy.

NGC 2366 is still producing stars. As you pan across the image look for bright blue dots throughout the image. These are giant blue stars many times larger than our Sun. Intense ultraviolet radiation from these new stars excites atoms in the nebulae scattered throughout the image causing them to glow. Zoom into the blue nebula in the upper right hand corner. This star-forming nebula is NGC 2363. This nebula is actually has more of a pinkish tint but is blue because of the green and infrared filters used for this image by the Hubble.

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The ancient peoples saw pictures in the sky. From those patterns in the heavens, ancient storytellers created legends about heroes, maidens, dragons, bears, centaurs, dogs and mythical creatures...
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