Category: Letters

A Confused Galactic V


Check out a galactic-sized “flying V in this image of interacting galaxies IC 2184 from NASA’s Hubble Space Telescope.

Explore the two nearly edge-on galaxies as they begin their billion-year-long dance. What shapes or stories do you see in the image? Leave a note in the comments below.

IC 2184 is really two galaxies. Even though space is huge, galaxies graze each other all the time. Gravity is strong with both galaxies. As the galaxies interact, stars, gas and dust are flung out into space forming long tidal tails. Look close for two faint tails. Usually these tails arc far into space but they look straight in this image because we are looking at them from the edge. The tails are arcing toward or away from us.

Also look for bright, fireworks regions. Gravity not only flings stars outward but also it can smash gas and dust. The bright blue and pink bursts are hot regions where new stars are forming, similar to regions in our galaxy such as the Orion Nebula or the Carina Nebula. These areas glow brightly enough that they show up as bright blobs of light in large telescopes.

IC 2184 is found about 160 million light-years from Earth toward the faint constellation Camelopardalis, the Giraffe.

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Dark Banded S


A dark, warped band of dust resembling a shallow ‘S’ curls through the center of galaxy Centaurus A in this image from the European Southern Observatory.

Explore the deepest view of this active galaxy. What shapes or stories do you see? Leave a note in the comments below.

Centaurus A, also known as NGC 5128, is a massive elliptical galaxy. At its heart, lies a supermassive black hole. Scientists think only a black hole 100 million times more massive than the Sun could give off the energy we see coming from the center of this galaxy.

The most prominent feature of this galaxy is the warped lane of dust across the center of the galaxy. This is a strange structure for an elliptical galaxy. The dusty band is probably the mangled remains of another galaxy that was gobbled up by Centaurus A. This dark band contains a huge amount of dust and gas. If you zoom in close along the edges of this band, look for bright young star clusters and red-glowing clouds of hydrogen gas. As dust and gas are smashed together, new stars can form. As we move outward from the center, the elongated shape of the elliptical galaxy is seen in the glow of hundreds of billions of cooler and older stars. They glow more yellow and red than their much younger blue siblings.

In the upper left, look for the long strand of purple and pink gas. This filament is lined up with a jet of material that we cannot see with our eyes. In radio images, however, these jets are bright. More filaments can be seen farther out and toward the bottom right. Scientists think that these filaments are part of jets of material blasted from the central black hole. The closest filament is more than 30,000 light-years from the center of the galaxy. The faint outer filaments are about 65,000 light-years from galaxy’s nucleus.

Centaurus A is one of the most studied galaxies in the sky. The galaxy lies just 12 million light-years from Earth toward the constellation Centaurus. The name Centaurus A was given because it was the first major source of radio waves from that constellation in the 1950s.

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Super S

Credit: ESA/Hubble & NASA

A super “S” traces through sprawling arms of spiral galaxy M100 in this image from the NASA/ESA Hubble Space Telescope.

Zoom into the swirling dusty lanes, pink nebulae and blue supergiants in this image. Leave a note in the comments below telling your stories of this image. The entire starry alphabet spelled out with Hubble imagery can be found here.

Astronomers consider M100 to be a classic example of a grand design spiral galaxy; the ideal spiral galaxy. Similar to our own Milky Way Galaxy, spiral galaxies have bright cores that are probably home to a supermassive black hole. These black holes suck up material. As this gas and dust falls toward the center, it glows brightly.

As you travel from the bright nucleus out along the dust lanes that make up the spiral arms, look for patches of reddish nebulae. These regions are similar to the nearby Orion Nebula. Their pink color come from glowing hydrogen gas, perfect fuel for creating new stars. Blue patches within the spiral arms are groups of young, hot and massive blue stars. These new stars will probably live short lives exploding in supernovae after they quickly burn through their hydrogen fuel. As these stars explode, their shockwaves will push new material together to form new stars. One such bubble is found to the right of the nucleus.

M100 is found just 50 million light-years from Earth toward the dim constellation Coma Berenices, the hair of Queen Berenice from Greek mythology. The sparkling stars have also been related to the end of the tail of Leo, the Lion.

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Stellar Exclamation

Credit: X-ray NASA/CXC/IfA/D.Sanders et al; Optical NASA/STScI/NRAO/A.Evans et al

Colliding galaxies form an exclamation point in this composite image from NASA’s Chandra and Hubble telescopes.

Explore the image of VV 340, or Arp 302. What shapes and patterns do you see in pair of galaxies? Leave a note below.

Although the two spiral galaxies are in the beginning stages of interaction, they are destined to merge far in the future. Scientists study these galaxies with many sensors. Chandra X-ray Observatory data is shown in purple. infrared light is picked up by Spitzer Space Telescope. And visible light in the form of red, green and blue light is combined with light from the other sensors to make this image. One thing of interest to scientists is the bright infrared glow from VV 340. Astronomers call these kinds of objects Luminous Infrared Galaxies or LIRGs. Astronomers do not know why these galaxies emit so much infrared radiation. Infrared is a part of the spectrum of light with a slightly longer wavelength as visible light. We feel infrared radiation as heat. One possibility shown in the Chandra observations is that a growing supermassive black hole powers the galaxy at the top. While only a small amount of infrared light is given off by a black hole, black holes do give off ultraviolet light.

VV 340 is found about 450 million light-years from Earth toward the constellation of Boötes, the Watcher of the Bear. In Greek mythology Boötes guards over both the great bear Ursa Major and Ursa Minor. The constellation contains the third brightest star in the night sky, the red star Arcturus.

Spiral Z

Credit: NASA and The Hubble Heritage Team (STScI/AURA)

Glowing gas and starlight with dark bands of interstellar dust create a cosmic letter Z in this image from NASA’s Hubble Space Telescope. NGC 1300 is considered the typical barred spiral galaxy.

Explore the image of NGC 1300. In a barred spiral, the galaxy arms connect to the ends of a bar of stars that contains the galactic nucleus. Some astronomers believe that the Milky Way Galaxy may be a barred spiral. Check out the newest and hottest stars in the sweeping spiral arms. Dense dust lanes trace out structures within the spiral arms and bar. The bright blue areas at the outside of these spiral arms are actually giant star clusters. In the central bar, older cooler stars reside. Zoom in to the galaxy’s core. The nucleus of NGC 1300 shows what astronomers call a “grand-design” spiral structure. Astronomers see this structure in the largest barred spiral galaxies. Flit from your choice of hundreds of background galaxies. These far-off galaxies are visible even through the densest part of the spiral arms.

NGC 1300 is located about 69 million light-years from Earth toward the constellation Eridanus. The meandering constellation Eridanus represents the Po River in ancient mythology and is the source of waters flowing from Aquarius, the water bearer.


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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