A project of the Dark Energy Survey collaboration

Latest

Image

A Universe of Possibilities

ngc_new_v0-1398_20130130.mm1.2-950px

Over the course of billions of years, a new home is built. It will eventually house stars, planets and perhaps civilizations. The force of gravity and the conservation of momentum can transform a dense cloud of cold dust and gas into a menagerie of stars and myriad opportunities for life. The stuff of stars is the stuff of us.

This particular distant galactic home, NGC 1398, lives in the Fornax cluster of galaxies 65 million light-years away (or one billion round trips between New York City and Los Angeles). It is farther away from us each day, moving away at 1400 kilometers per second–over 3 million miles per hour. For comparison, the NASA space shuttle during launch only moves at 35,000 miles per hour.

At 135,000 light-years in diameter, NGC 1398 is just slightly larger than the galaxy we call home, the Milky Way. Like our home galaxy, it has come to burn with the light of a hundred million suns and who knows how many civilizations.

If you’d like to look for this southern hemisphere gem yourself, it lives at RA/DEC: (03 38.9, -26 20).

We close with a question: Who first wrote the now-famous equation that estimates the probability of life in the universe?

Written by: Det. B. Nord [FNAL]
Image Credit: Erin Sheldon [BNL], Martin Murphy [FNAL]

Posted by  |  May 27, 2013 | Categories: Dark Energy Photographs, DECam Images, English, Ingles | Tags: , , , , , | Comments Off on A Universe of Possibilities

Image

Moonrise over Tololo

ctio_moonrise_20130208_reduced

In the east, peeking through a rare mountaintop tree, the Moon rises toward the Milky Way.  Not too far behind, the Sun‘s rays reach over nearby mountains to at once expose the valley fog and cover the escape of distant stellar brethren into the daylight.

To the south (on the right) sits the Blanco telescope, readying for its daytime rest. Across the ridge live neighboring telescopes at the Cerro Pachon site, including world-class telescopes SOAR and GEMINI. Can you spot them on the distant ridge? (Hint: in the far right of the photo). The white lines on the ground are metal walkways that astronomers use during the night to move from one building to the other in the utter darkness; their reflectivity allows someone walking to find their way even before their eyes have fully acclimated to the darkness.

It had been a quiet night. Well, they’re all quiet nights: the loudest sound by far originates in the slow whir of motors as domes turn toward new expanses of polka-dot sky. Earlier in the evenings, the temperature drop as day changes into night causes the metal in the domes to contract slightly, and rhythmically—ka-chunk, ka-chunk, ka-chunk. It’s a reminder that we brought these machines to an alien environment, an outpost between humans and the heavens. Nestled within the dome, Blanco and the Dark Energy Camera (DECam) toil away, far more impervious to the elements and designed to be compatible with such temperature changes.

This was one of the last nights of my 10-day run at Cerro Tololo Inter-American Observatory. The moon rose earlier on nights past; when that happens, that part of the sky becomes too bright for the highly sensitive DECam. Nevertheless, we observed several patches of sky to extraordinary depth in the hopes of finding old, distant exploding stars—one of the types of objects that will help illuminate dark energy’s impact on the fate of the cosmos.

Where does moonlight originate? Hints: the moon is not a star, and it is very reflective.

Written by: Det. B. Nord [FNAL]
Image Credit: Det. B. Nord

Posted by  |  May 20, 2013 | Categories: English, Ingles, Photographs from DES Participants | Tags: | Comments Off on Moonrise over Tololo

Image

Catching Old Light: DECam Style

composite_12-0331-11D_11-0222-13D_v1

A photon is born, its birthplace the heart of a star, billions of light-years away and eons ago. Its brothers and sisters headed off in all directions, but this one—this one found its way in one particular direction, toward a civilization that had just learned to command the elements enough to peek beyond the terrestrial veil. After a long, long journey this photon—this old, old light—encountered a mountain top in the Chilean desert, where it found a new home.

At the Cerro Tololo Inter-American Observatory (CTIO), an old workhorse has learned some new tricks and received some serious cyber upgrades. The Victor M. Blanco telescope (left image) was commissioned in the mid-1970s, along with its near-twin sister telescope, the Mayall, which is located in Kitt Peak, Arizona. The Blanco is a reflector-type telescope with an equatorial mount. Situated on one end of the Blanco is large mirror (left image: just right of center), which collects and redirects light toward lenses made of specially crafted glass. These lenses focus the light on a detector composed of a material that converts light into electrical signals, which are then transformed by software into images visible to the human eye.  The back of the detector is shown in left image (just left of center) and the front of the detector is in the right image.

Blanco’s primary mirror is four meters in diameter, long enough for two tall people to lay across, end to end. From the primary mirror, near the base, to the detectors at the top, one could stack about 15 tall people head to toe across the 28-meter span; this is also roughly the length of a basketball court.

Every time the telescope moves to look at a new patch of sky, the motors have to shift  300 tons of glass and metal. This is the equivalent of 4300 people, 150 cars, 10 Humpback whales or 5 Brachiosaurus dinosaurs. It would take about seven Blanco telescopes to equal the weight of one space shuttle at the time of liftoff.

The telescope’s detectors are known formally as charge-coupled devices (CCDs), which are similar to photographic film, in that they are made of materials that absorb and react to light. They are also the very same kind of detector that is found in digital cameras like in your point-and-shoot, or in your mobile phone.

Over the decades of its life, the Blanco telescope has evolved, and most recently, the Blanco was retro-fitted with many new pieces of instrumentation, including new optical elements, a new shutter and other components. Critical to the mission of the Dark Energy Survey is also a new set of detectors that were developed at the Fermi National Accelerator Laboratory in Batavia, Illinois. These 62 new detectors are state-of-the-art CCDs that make up the 570 Megapixel Dark Energy Camera (DECam), which is shown in the image at the right.

DECam is not just over 50 times larger than your average point-and-shoot camera: it has unprecedented sensitivity. This camera is so sensitive it could detect light from a 100-watt light bulb as far away as the moon.

Thanks to the upgrades at the Blanco, old, travel-weary light from a billion trillion miles away, which happened to makes its way toward Earth long ago, will be welcomed with open eyes and ready minds.

Written by: Det. B. Nord, PhD [Fermi National Accelerator Laboratory]
Image Credit: Reider Hahn [Fermi National Accelerator Laboratory (Visual Media Services)]

Posted by  |  May 13, 2013 | Categories: Dark Energy Photographs, English, Ingles | Comments Off on Catching Old Light: DECam Style

Image

A Family of Galaxies

abell3151_reduced

In a sea of darkness, innumerable points of light come into focus. While there are some stars visible here, nearly all the red, blue and yellow objects are galaxies. In the lower left and upper right, some of the blue galaxies show off their beautiful spirals (similar to our own Milky Way). The blue color and the clear structures (bars, spiral arms, dense clouds) within these galaxies betray their basic nature: newly birthed stars emanate the blue color and the very existence of the structures means that these galaxies live in a pristine environment where gravity is the dominant force acting to clump things together. All in all, these spiral galaxies are thus relatively young.

In stark contrast, the yellower and redder galaxies have stopped forming new stars and are often referred to as ‘red and dead.’ These galaxies have endured turbulent lives: having been rocked by collisions with other galaxies, they are too hot to form stars. What’s more, all the work that gravity did to make structures within has been washed away leaving just bright cores, diffuse outskirts and elliptical shapes (and so they are named ellipticals).

Several elliptical galaxies appear clustered (just left of center of the image). These galaxies are gravitationally bound as a group or cluster. This cluster has 43 galaxies (can you find them all?), and it was one of the clusters discovered by George Abell and collaborators during the 1970’s and 80’s as part of the Southern Sky Abell Catalog (published posthumously in 1989).  Amazingly, these clusters were discovered and measured with the human eye using photographic plates, rather than the electronics that the Dark Energy Survey uses, and they are part of the earliest comprehensive collection of optically observed clusters started by George Abell in 1958.

Our cluster here is Abell Catalog No. 3151 (out of over 4000), located in the Fornax Constellation. It lives just about one billion light years from Earth (actually quite close compared to the most distant clusters) and spans about five million light years from end to end.

What has dark energy done to this cluster?  Galaxies within a cluster gravitate toward one another, because galaxies have mass.  In contrast, dark energy stretches the fabric of space-time, upon which galaxies reside.  Thus, dark energy directly opposes gravity.  Dark energy can affect larger objects like clusters of galaxies, but isn’t strong enough to pull apart stars, solar systems or galaxies (where gravity is much stronger).

If gravity serves to pull massive objects (like galaxies) toward one another, then dark energy will pull them away from each other. There are millions and millions of families of galaxies across the universe, and dark energy will make them smaller.

What’s more, you’ll find small colored streaks randomly dispersed throughout the image. These come from very high-energy (fast!) cosmic rays that hit the camera’s detectors but briefly, leaving small imprints in the image. These cosmic ray streaks are just one type of artifact that have to be cleaned out of the images before cosmological questions can be asked. In future posts, we’ll discuss more about the data reduction process.

If you want to find Abell 3151 yourself, look at coordinates RA (03:38:16.61) and DEC (-28:50:32.28) in units of Degrees:Minutes:Seconds; it may be hard to see if you’re in the the Northern Hemisphere.

What other kinds of cosmological structures do you think will be affected by dark energy? Why is gravity stronger than dark energy amidst smaller structures?
Written by: Det. B. Nord, PhD [Fermi National Accelerator Laboratory]
Image Credit: DECam via Det. Erin Sheldon, PhD [Brookhaven National Laboratory]
Email us at darkenergydetectives@gmail.com if you have clues, questions or comments about anything cosmology.

Posted by  |  May 6, 2013 | Categories: Dark Energy Photographs, DECam Images, English, Galaxy Cluster, Ingles | Tags: , , | Comments Off on A Family of Galaxies

Image

Time to Meet the Neighbors!

ngc0894-rebin2_new_cropped_reduced_v0

Spiral Galaxy NGC 0895 was discovered by William Herschel in 1785. Herschel created the first maps of the Milky Way galaxy by observing and drawing the stars. Herschel also saw galaxies outside the Milky Way, but he didn’t know what they were, so he only referred to them generically as nebulae. That was the common term at the time for diffuse, extended objects – including actual nebulae, which are the gaseous remains of exploded stars.

Galaxy NGC 0895 is located in the constellation Cetus, about 110 million light years away – still a fraction (about 0.2 percent) of the observable universe. The star nearest to us, Alpha Centauri, is 4.3 light years away, and the nearest spiral galaxy, Andromeda, is 2.5 million light years away.

We can tell how many stars are forming by how blue the galaxy appears through the camera lens. Blue galaxies contain many young, newly formed stars. The golden object in the upper right is a redder galaxy, which has many more older red stars, and fewer still forming.

If you want to find NGC 0895 yourself, it is located at coordinates (RA 02 21 36.5, Dec -05 31 16).

This image was taken with the Dark Energy Camera, and shows us this galaxy in sharper detail than we have ever seen it. Check back here every Monday for another image and another story from the Dark Detectives at DES.

Posted by  |  April 29, 2013 | Categories: DECam Images, English, Ingles | Tags: , , , , , , , , | 1 Comment