For the last week, detectives from the Dark Energy Survey have been coordinating across four continents to bring to light more evidence of how the fabric of spacetime is stretching and evolving.

In Sussex, England, over 100 detectives met to discuss the current state and the future of the Survey that is conducted at the Blanco telescope, located at Cerro Tololo in Chile. At this semi-annual collaboration meeting (with a new venue each time), we continued to strategize analyses for the many probes of spacetime evolution and dark energy: as I write, several early results are being prepared for publication.

At Cerro Tololo, a team of observers operated the Dark Energy Camera (DECam) on the Blanco telescope, as we make our way through the second season of observing for the Survey. Each season goes August through February, during the Chilean summer.

The Anglo-Australian Telescope at Siding Spring Observatory in Australia is home to the OzDES Survey – long-term project for obtaining highly precise distance measurements of objects discovered by DES, such as supernovae and galaxy clusters. These “follow-up” measurements will be very important evidence in pinning down the culprit for dark energy.

At Cerro Pachon, just east of Cerro Tololo, another team of two agents began to search for evidence of highly warped space in the distant cosmos, using the Gemini (South) Telescope (@GeminiObs). We spent six nights working to measure highly accurate distances of strong gravitational lensing systems. These systems are galaxies or groups of galaxies that are massive enough to significantly distort the fabric of space-time. Space and time are so warped that the light rays from celestial objects – like galaxies and quasars – behind these massive galaxies become bent. The resulting images in DECam become stretched or even multiplied – just like an optical lens. In future case reports, we’ll expand on this phenomenon in more detail.

All the while, supercomputers the National Center for Supercomputing Applications (NCSA) are processing the data from DECam each night, turning raw images into refined data – ready for analysis by the science teams.

The image above doesn’t display any obvious strong lenses, but it is an example of the exquisite lines of evidence that DES continues to accumulate each night.

Here are positions of some of the galaxies above. What information can you find about them? There are several electronic forensic tools to assist your investigation (for example, http://ned.ipac.caltech.edu/forms/nearposn.html; take care to enter the positions with the correct formatting, as they are below).  Tweet your findings to our agents at @darkenergdetec, and we can compare case notes.

RA: 304.3226d,    Dec: -52.7966d

RA: 304.2665d,    Dec: -52.6728d

RA: 304.0723d,     Dec: -52.7044d

Good night, and keep looking up,

Det. B. Nord

Det. M. Murphy [image processing]

Across North America, as the transition toward winter begins, we see symptoms in the changing colors of tree leaves. The lively green hue of summer gives way to yellows, oranges, reds and purples. Living cells inside the leaves have instructions for how to react to cooler and cooler environments: this reaction reduces the production of the green pigment, chlorophyll, allowing other colors (caused by the pigments of the carotenoids and anthocyanins) to dominate. When spring returns, so do leaves, newly filled with oxygen-producing chlorophyll.

Year after year, we watch the cycle of death and rebirth in the life-giving foliage around us.

But what if we were insects? What if, like the mayfly, we lived for only a day or two? Would we have any way of understanding the immense tapestry evolving around us? Imagine for one day on Earth, looking at leaves all over the globe – in different environments and in various states of health and age. With just this one day to create a coherent picture, could we piece together the clues of color, environment and the internal workings?

This is the challenge we face in understanding the life-cycle of galaxies, the leaves on our cosmic tree of matter and light. To these celestial objects, we are indeed the mayfly, living for only a blink of an eye in cosmic time.

Consider the cornucopia of dusty swirls in the image above, their colors spanning the entire visible rainbow and beyond. Each puff of light contains billions of stars. Through our telescopes, images and spectrographs, we learn about the kinds of chemicals, of matter that reside within galaxies. Through an understanding of physics, we link this information to the possible physical processes, from gravity to quantum mechanics.

Similar to that of tree leaves, the colors of galaxies are the result of the chemical constituents, and they reflect their ages. Blue galaxies, still young, are cold enough to be forming stars, because young stars and the gas enshrouding them release bluer light to the cosmos. Red galaxies have had their star-formation extinguished: their gases are too warm for the force gravity to collapse them into energy-generating balls of fusion. These ‘red and dead’ galaxies represent the end of the galactic life-cycle.

While we have ways of peering inside galaxies to reveal some of their guts, we still have no way to watch an entire galaxy come into being, much less live out a full life. Each galaxy represents its own tributary of time, its own puzzle piece in the delta of the cosmic web.

Det. B. Nord

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