A project of the Dark Energy Survey collaboration

Dark Energy Photographs


In the air tonight


Sometimes, you can feel it coming in the air of the night.

Weather is fickle, but when a night of observing begins, we usually know how it will go. The first part of this season was often rainy and gray. The last several weeks, however, have allowed for new records in precision the precision of DECam data.

On Nov 11 and Nov 18, 2014, the Dark Energy Survey took exquisite data of all of our supernova fields – the regions of sky selected specifically to look for exploding stars. It was clearer than anything we’d seen previously. The video above is from a night early in this season, when the weather was also extremely good (but only for a few days). It is a view, from inside the dome, of DECam and the Blanco Telescope scanning the sky over the course of one night in August, 2014.

After a few nights of clouds or rain, it usually takes another night or two for the atmospheric turbulence to die down. This turbulence deflects light as it comes through the layers of Earth’s atmosphere, effectively blurring an image. But when this turmoil is no longer there, the conditions can be pristine.

Sometimes, you can feel it coming in the air of the night. It’s the final moment for so much starlight.

We are here to see what it did, see it with DECam’s 570 million eyes. DECam’s been waiting for this moment all of its life. Now we know where you’ve been, traversing the dark night skies.

The light of distant galaxies and stars has been waiting for this moment all that time.

Now forever, we remember where the light has been, how could we forget. When our detectors capture it, it’s the first time, the last time, we’ve ever met. We know the reason you kept your silence up. When it was cloudy, how could we know. When it’s clear, the signal still grows, the universe no longer a stranger to you and me.

Sometimes, you can feel it in the air of the night.




Det. B. Nord

[Hat tip to Phil Collins.]


Afluentes del tiempo: hojas de otoño

DES2111-0124_20140923_03_gri_20140923_000.cut.edit1.6-1000pxEn el hemisferio norte, a medida que comienza la transición hacia el invierno, vemos los síntomas de este proceso en los cambiantes colores de las hojas. El animado tono verde del verano da paso a los amarillos, naranjas, rojos y morados del otoño. Las células vivas de las hojas tienen instrucciones sobre cómo reaccionar a ambientes más frescos y fríos. Esta reacción reduce la producción del pigmento verde, la clorofila, lo que permite que otros colores (creados por los pigmentos de los carotenoides y antocianinas ) prevalezcan. Cuando regrese la primavera, también lo harán las hojas, de nuevo con abundante clorofila productora de oxígeno. Año tras año, vemos este ciclo de muerte y renacimiento en el follaje a nuestro alrededor .

Pero… ¿y si fuéramos insectos? ¿Qué pasaría si, al igual que la moscas, viviéramos durante sólo uno  o dos días? ¿Tendríamos alguna forma de entender el inmenso tapiz en evolución que nos rodea? Imagina un único día en la Tierra, observando las hojas por todo el mundo – en diferentes ambientes y en diversos estados de salud y edad. Con sólo este día para crear una imagen coherente, ¿seríamos capaces de reconstruir el funcionamiento interno de este ciclo con estas pistas?

Este es el reto al que nos enfrentamos en la comprensión del ciclo de vida de las galaxias, las hojas de nuestro árbol cósmico de materia y luz. Para estos objetos celestes, de hecho somos como las moscas, que sólo viven durante un abrir y cerrar de ojos en escalas cósmicas de tiempo.

Observa la multitud de remolinos de polvo en la imagen de arriba. Sus colores abarcan todo el arco iris visible y más allá. Cada mancha de luz contiene miles de millones de estrellas. A través de nuestros telescopios, imágenes y espectrógrafos, aprendemos sobre los tipos de productos químicos de la materia que reside dentro de las galaxias. A través de la comprensión de la gravedad y la mecánica cuántica, vinculamos esta información a los posibles procesos físicos que están teniendo lugar.

De manera análoga a las hojas del árbol, los colores de las galaxias son el resultado de sus componentes químicos y reflejan su edad. Las galaxias azules, todavía jovenes, son lo suficientemente frías para estar todavía formando estrellas, porque sus estrellas jóvenes y el gas que las envuelve liberan luz azul al cosmos. Las galaxias rojas han visto como su periodo de formación estelar se extinguía: su gas ahora es demasiado caliente para que fuerza de la gravedad pueda colapsarlas en ardientes esferas. Estas galaxias rojas y muertas representan el final del ciclo de vida galáctico .

Si bien tenemos formas de observar las entrañas de las galaxias, aún no existe la manera de observar cómo se forma una galaxia, y mucho menos ver su vida entera. Cada una representa su propio afluente del río del tiempo, su propio pedazo del rompecabezas en la delta de la red cósmica .

Det. B. Nord

Imagen: Dark Energy Camera [Edited and logged by Det. M. Murphy]

Traducción: Nacho Sevilla


Unsung Hero Cold Cases – The Slipher File

 As the Milky Way sets, light from nearby villages and mining towns turns the stream of clouds overhead into a rippling river of fool’s gold. On this night in October of 2013, during the first season of observations of the Dark Energy Survey, we pumped caffeine into our bodies to stay awake, to keep ready for when the conditions would change. Every field we can observe, every galaxy we can capture will make a contribution to the greater measurement of their vast patterns – patterns distorted (or created) by a dark energy.

One hundred years ago, an American astronomer by the name of Vesto Slipher became the first to measure streams of galaxies in our local neighborhood. Slipher used the 24-inch telescope at Lowell Observatory to measure velocities of spiral nebulae (i.e., galaxies), through a method known as “spectroscopy.” Most of the galaxies that Slipher measured are receding from the Milky Way, rather than moving toward it – the first indication of cosmic expansion.

This result laid the groundwork for the definitive discovery of the expanding universe. Unfortunately, Edwin Hubble of Mount Wilson is most often accredited with this finding. Hubble measured distances via Cepheid Variables to distant nebulae and then correlated them with Slipher’s velocity (redshift) data to create the famous distance-velocity plot for his 1929 paper.

Hubble provided no citation of Slipher’s work.

Slipher is the first to measure Doppler Shifts (velocities) of galaxies, to show that spiral galaxies rotate, and to detect that collections of stars and dust are actually nebulae outside our own Milky Way.

Let us remember Vesto Slipher – among modern cosmology’s most influential unsung heroes.

Det. B. Nord


Distant Wanderer

TV158-cropAfter a great journey, a long-hidden member of our solar system has returned. Not since the 9th century, when Charlemagne ruled as Emperor of the Holy Roman Empire and Chinese culture flourished under the Tang Dynasty, has this small icy world re-entered the realm of the outer planets.

This distant wanderer is among first of its kind discovered with data from the Dark Energy Survey (DES). Now officially known as 2013 TV158, it first came into view on October 14, 2013, and has been observed several dozen more times over the following 10 months as it slowly traces the cosmic path laid out for it by Newton’s law of gravitation. We see this small object move in the animation to the left, comprised of a pair of images taken two hours apart in August, 2014.

It takes almost 1200 years for 2013 TV158 to orbit the sun, and it is probably a few hundred kilometers across – about the length of the Grand Canyon.

In eight more years, it will make its closest approach to the sun – still a billion kilometers beyond Neptune. At this distance, the sun would shine with less than a tenth of a percent of its brightness here on earth, and would appear no larger than a dime seen from a hundred feet away.

That’s what high noon looks like on 2013 TV158.

Then it will begin its six-century outbound journey, slowly fading from the view of even the most powerful telescopes, eventually reaching a distance of nearly 30 billion kilometers before pirouetting toward home again sometime in the 27th century.

This object is just one of countless tiny worlds that inhabit the frozen outer region of the solar system called the Kuiper Belt, an expanse 20 times as wide and many times more massive than the asteroid belt between Mars and Jupiter. The dwarf planet Pluto also calls the Kuiper Belt its home. The orbits of Jupiter, Pluto and 2013 TV158 around the sun can be seen in the image to the lower right.

Scientists believe that these Kuiper Belt Objects, or KBOs, are relics from the formation of the solar system, cosmic leftovers that never merged into one of the larger planets. By studying them, we can gain a better understanding of the processes that gave birth to the solar system 4.5 billion years ago.

ellipses-blackBecause they are so distant and faint, KBOs are extremely difficult to detect. The first KBO, Pluto, was discovered in 1930. Sixty-two years would pass before astronomers found the next one. Astronomers have identified well over half a million objects in the main asteroid belt between Mars and Jupiter. To date, we know of only about 1500 KBOs.

DES is designed to peer far beyond our galaxy, to find millions of galaxies and thousands of supernovae, but it can also do much more. DES records images of ten specific patches of the sky each week between August and February. These images are a perfect hunting ground for KBOs, which move slowly enough that they can stay in the same field of view for weeks or even months. This allows us to look for objects that appear in different places on different nights, and eventually track the orbit over many nights of observations.

So far we’ve searched less than one percent of the DES survey area for new KBOs. Who knows what other distant new worlds will wander into view?

Det. D. Gerdes


Light-years Away, Right at Home



As the Galaxy sets behind the Blanco telescope, our home away from home, we are reminded of where we really are. Earth resides in a mere village of planets, one of many in a city of stars – our Milky Way galaxy – which, as these detectives see it, is our true home.

But it is the distant stars and galaxies, just like those we call home, that betray patterns in our cosmos.

We operate in the dark of night to find as many as we can, as carefully as we can. We track locations, movements, interactions, explosions and lifetimes of millions of individuals. Only these clues in aggregate (for the most part), will lead us down a starlit path to an understanding of our universe’s greatest tug of war: that which is between the pull of gravity and the accelerating expansion of dark energy.

The detectives have gone back to work for Season 2 of observing and combing the logs of photons as they stream into the trap we’ve set, the Dark Energy Camera (DECam). In the coming months, we’re turning these streams into nuggets of knowledge, the first puzzle pieces to be revealed by the Dark Energy Survey (@theDESurvey).

And ultimately this knowledge brings us back home, to understanding our place in the cosmos.

I’m here now at the Blanco, writing this as we prepare for our third night of observations and tracking in Season 2 of DES, with bags under our eyes, coffee mugs in hand, watching the fires in the sky.


Det. B. Nord (@briandnord)



If you run into us where the electrons roam (FB, Twitter, Reddit, etc.), don’t be afraid of the dark – get in touch. We’ll report every two weeks (and occasionally more), and we’ll have more detectives and more ways to tell the stories.

Today, there’s an announcement about the beginning of Season 2, along with a spate of videos and images about the team of detectives, the location and the machine we’ve built.


New Beginnings: Our Darkness (Re)Lit

DES0500-6205_cut_MJM.Nebulosity.3.3.960pxWhat clues early in humanity’s search of the sky told the Universe’s story? Emerging from the darkness long ago, what diffuse beacons in the fabric of spacetime offered a glimpse into our place in the cosmos?

When Galileo first pointed his telescope at Jupiter and saw its moons he inevitably would have looked at other parts of the sky. He would have noticed fuzzy patches of light in the sky. Early astronomers could only guess what those fuzzy patches of light were. Collectively, they were referred to as “nebulae”, due to their nebulous forms. Intentional or not, this was the beginning of modern astronomy.

Until the early 1900s, scientists believed the entirety of the universe was contained in what we now call our Milky Way galaxy. They believed that the fuzzy nebulae were much closer to Earth than they actually are. It wasn’t until Edwin Hubble’s observations of Cepheid variable stars in the Andromeda and Triangulum nebulae in the early 1920s that astronomers began to appreciate the size and scope of the universe.

Hubble discovered that those little fuzzy patches of light were entire collections of stars much farther away from us than the rest of the stars in the night sky. In short order, these collections of stars would be referred to as galaxies. That name was natural: the Greeks had already been referring to the fuzzy disc of the Milky Way as a galaxy (the Greeks referred to it as galaxias kyklos which means milky circle; the Latin word galaxias literally means milky way).

Our Milky Way was now one of many, many galaxies.

After changing our notion of what a galaxy is and our place in the universe, Hubble set out to categorize the different kinds of galaxies. Pictured above are many types of galaxies captured by the Dark Energy Camera (DECam). There are at least five or six easy-to-spot galaxies – the edge-on spiral on the right side, the pair of colliding spirals at the bottom center, a big spiral in the top-left, and an elliptical on the far left.

Hubble’s discovery rocked astronomy, and as the fields of astronomy and physics inevitably came together, many new questions emerged. Is the universe static? How did the universe come into being? How old is the universe?

Our current understanding is that the universe is not static.  Nobel prize-worthy research conducted in the late 1990s used exploding stars (supernovae) to reveal that the cosmos is expanding at an increasing rate.  Some new form of energy (dark energy) is overwhelming the force of gravity between all the massive objects in the universe.  The fate of the cosmos is once more brought to light.

So what is driving that expansion? What is causing galaxies to move away from one another, overcoming gravity’s pull?  The answer appears to be dark energy. Very little is known about dark energy, but we believe it makes up about 2/3 of the energy in the universe.

And so we are at the beginning again. Our answers lead us to new questions. There are many more questions to answer, and many more measurements to make.

If you’re interested in seeing these galaxies for yourself, point your telescope toward RA 05:00:34 Dec -62deg 4’.

Written by Det. Marty Murphy [FNAL]
Image by Det. Marty Murphy


DECam Tracks Near-Earth Asteroid

In the early evening of February 3rd, 2014, the DES team received an urgent request for optical imaging of a Near Earth Object (NEO) on a “potentially hazardous orbit.” This asteroid had first been spotted by the NEOWISE (NEO Wide-field Infrared Survey Explorer) team. However, they had been unable to pin down its orbit. Additionally, poor weather in Hawaii and Arizona had stymied all other attempts to image this object. To make matters even worse, the asteroid was rapidly moving towards lower solar elongations which would bring it in line with the Sun and make later observations impossible.

Luckily, the Dark Energy Survey (DES) was on the scene as humanity’s best, last, and only line of defense. Cerro Tololo was enjoying some of the finest weather Chile has to offer, and DECam’s large field of view makes it an excellent instrument for tracking down errant asteroids. Soon after sunset, the Blanco 4m telescope swung towards the best guess for the asteroid’s position and DECam took five images, dithering slightly to make sure the asteroid couldn’t slip through the gaps between CCDs, DECam’s digital imaging chips.

After rapid processing, the DECam images revealed a new Apollo-class asteroid, 2014 BE63. The NEOWISE team confirmed that 2014 BE63 will cross the Earth’s orbit; however, the closest approach to Earth itself will be at a safe distance of 18 million miles.

We dark energy detectives can rest easy knowing that, in the words of Steve Kent [FNAL], “2014 BE63 poses no threat to DES observations (and no threat to Earth).

Written by Detective Alex Drlica-Wagner [DES, FNAL]
Video by Alex Drlica-Wagner