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Dark Energy Survey @TheDESurvey
We have a new DArchive article! Read about DES scientists studying galaxy clusters and why they are looking for som… https://t.co/z1FS5IK3k4

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Dark Energy Survey @TheDESurvey
I've spent years on tasks that seem tangentially related to my science goals: applying for telescope time, sifting… https://t.co/6htCP0hY9a

Nov 09 reply retweet favorite 3 days ago

Dark Energy Survey @TheDESurvey
RT @p_realism:And here we go: ⁦@Ofer_Lahav⁩ kicks off ⁦@theDESurvey⁩ meeting: 200 papers being produced, last observations to con… https://t.co/OEVA0vGqBT

Nov 09 reply retweet favorite 3 days ago

Dark Energy Survey @TheDESurvey
RT @UoS_SNe:Money Slide number 1: how amazing does the @theDESurvey SN Ia Hubble diagram look?? https://t.co/imlDdsdbqk

Nov 09 reply retweet favorite 3 days ago

Dark Energy Survey @TheDESurvey
RT @robertcnichol:Local @portsmouthuni story on this week's @theDESurvey #hubbleconstant stuff https://t.co/aX9xfpSTjd

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The Dark Energy Survey
7 hours ago
We have a new article on the DArchives! Read about DES scientists studying galaxy clusters and why they are looking for something called the ‘splashback radius’. www.darkenergysurvey.org/darchive/finding-edges-massive-galaxy-clusters/

The DArchives are articles on DES science geared toward a public audience. See more here: www.darkenergysurvey.org/news-and-results/darchives/ ... See MoreSee Less
Finding the Edges of Massive Galaxy Clusters - The Dark Energy Survey
darkenergysurvey.org
This DArchive describes the detection of a feature known as the “splashback radius” of galaxy clusters as seen in DES … Read more »
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The Dark Energy Survey
3 days ago
I've spent years on tasks that seem tangentially related to my science goals: applying for telescope time, sifting through data for targets, analyzing and organizing spectra. The disconnect can be a real source of discouragement, and not every day was a great one. But ...

... this week the DES Supernova Program published our first cosmological constraints, the first major result of all those years of work! Seeing it all finally come together with amazing data and rigorous analysis is a fantastic feeling. :-) #DEST4TD

Thanks to Chris D'Andrea (University of Pennsylvania) for today's DES thought for the day! ... See MoreSee Less
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The Dark Energy Survey
5 days ago
As everyone probably saw last night….DES released 8 papers related to its first cosmology results using Type Ia supernovae! Studying these objects led to the discovery of the effects of dark energy 20 years ago.

The new papers can be read at: des.ncsa.illinois.edu/releases/sn

For a little background on Type Ia supernovae, check out: hubblesite.org/hubble_discoveries/dark_energy/de-type_ia_supernovae.php
www.darkenergysurvey.org/the-des-project/science/ ... See MoreSee Less
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The Dark Energy Survey
1 week ago
#DESimages (Credit: Erin Sheldon)

Today’s image is particularly interesting. You can see some bright stars (the bright blue light with diffraction spikes) and some galaxies like most images. But this image also has what is likely an asteroid. Can you spot it?

Hint: It’s not the long horizontal streak near the bottom, that is due to diffracted light from the bright blue star.

To understand what’s going on, it is helpful to know that this image, like many we post here are called ‘coadded’ images, meaning it is a stack of images taken in different color band filters. This is useful both for getting a multi-color image, but also a deeper image to bring out faint galaxies. This image is a coadd of several individual images over a few years of DES.

But, what if the objects in the sky are moving during that time? That is likely happening in the upper right where we see a bright red dot and a bright green dot. Unlike the mostly stationary stars and galaxies (when the telescope moves with the rotation of the Earth), something (probably an asteroid) in the top right has clearly moved between the time of some of the red and green images that were combined into this image. ... See MoreSee Less
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The Dark Energy Survey
1 week ago
Today I’m preparing for a 5-night observing run on the SOAR-4m telescope to obtain spectra of candidate pure-hydrogen-atmosphere white dwarf stars. These stars are very useful for DES photometric calibrations. #DEST4TD

Thanks to Douglas Tucker (Fermi National Accelerator Laboratory) for today's DES thought for the day!

Darkbites credit: Ravi Gupta
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News

Dark Energy May Be Incompatible With String Theory

August 9, 2018 12:00 am

Since 1998, telescope observations have indicated that the cosmos is expanding ever-so-slightly faster all the time, implying that the vacuum of empty space must be infused with a dose of gravitationally repulsive “dark energy.” In addition, it looks like the amount of dark energy infused in empty space stays constant over time (as best anyone can tell). But the new conjecture asserts that the vacuum energy of the universe must be decreasing. Paul Steinhardt, a cosmologist at Princeton University and one of Vafa’s co-authors, said that over the next few years, “all eyes should be on” measurements by the Dark Energy Survey, WFIRST and Euclid telescopes of whether the density of dark energy is changing. “If you find it’s not consistent with quintessence,” Steinhardt said, “it means either the swampland idea is wrong, or string theory is wrong, or both are wrong or — something’s wrong.”

The dark-energy deniers

June 19, 2018 12:00 am

Make no mistake, dark energy – be it the cosmological constant or quintessence – is the leading theory with plenty of observational evidence to support it. The alternatives remain highly controversial. Yet those nagging questions just won’t go away. Upcoming surveys will either solidify dark energy theory’s position further, or produce a surprise by pulling the rug out from under it. With the Dark Energy Survey – an international collaboration using a 570-million-pixel camera called DECam on the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory in Chile – releasing its first data from a survey of 300 million galaxies, these are exciting times. “What makes this a really fun field to be in is that I don’t know what the next big step will be,” concludes Riess. “We’re just in the middle of our initial reconnaissance, and I don’t think we should be surprised by surprises.”

Simon Samuroff receives URA Thesis Award for Dark Energy Survey image analysis

June 1, 2018 12:00 am

The Dark Energy Survey captures images of galaxies billions of light-years away to help our understanding of the evolution of the cosmos. Assessing these galaxies’ properties, such as their size, shape and distance from each other, is a painstaking process, one that involves not only collecting massive amounts of data, but also correcting for potential miscues that challenge the very act of assessing the data. The Fermilab-led Dark Energy Survey aims to make unprecedented measurements of a phenomenon known as gravitational lensing. Gravity bends light produced by faraway galaxies, so images of galaxies are subtly distorted by the time they reach Earth. The degree of distortion itself can provide information about those galaxies, galaxy clusters and the universe around them. An important step in making accurate measurements of the universe is by successfully isolating these tiny distortions. Simon Samuroff is the recipient of the 2017 URA Thesis Award, presented annually for outstanding work by a graduate student working at or in collaboration with Fermilab. In his thesis, titled “Systematic Biases in Weak Lensing Cosmology with the Dark Energy Survey,” Samuroff built computer simulations to model the shapes of galaxies captured by the Dark Energy Camera, which was built by Fermilab and is located at an observatory on a Chilean mountaintop. He closely compared thousands of the simulations to actual images to determine the amount by which scientists’ initial estimates of these distortions are incorrect. He singled out miscues so the Dark Energy Camera could make improved measurements and be more sensitive to subtle effects of phenomena such as dark matter. “The committee was impressed by both the quality of writing and the magnitude of his study — cataloging millions of galaxies or clusters and taking very small effects into account,” said Fermilab scientist Lenny Spiegel, chair of the URA Thesis Award Committee. “His work is invaluable to scientists studying mysteries regarding astrophysics, which may ultimately point the direction for future progress in particle physics.” One of Samuroff’s major results showed that interactions between the images of neighboring galaxies that overlapped affected scientists’ measurements more severely than they realized. By identifying where and to what degree distortions like this cause inaccuracies, Samuroff helps scientists create a more reliable system of measurement.

KBO could be evidence for a giant planet in the outer solar system

May 31, 2018 12:00 am

The discovery of a distant Kuiper Belt Object (KBO) with an extremely eccentric orbit could be evidence that a giant planet is waiting to be discovered in the outer solar system. KBO BP519 was discovered by scientists analyzing data collected by the Dark Energy Survey, which observes a region far above the orbital plane of most of the solar system’s planets as part of a project to measure acceleration of the universe’s expansion. It orbits the Sun at a tilt of some 54 degrees from the plane of the inner solar system planets’ orbits. Like several other KBOs found in 2016, which all orbit at the same unique angle to the plane of the inner planets, 2015 BP519’s position suggests it is being influenced by the gravitational pull of a much larger object, sometimes referred to as “Planet X” or “Planet Nine,” which may be shepherding it and the other above KBOs into this strange orbit. Since the 2016 discovery of these KBOs orbiting at the same distinct angle, scientists have been searching for a hypothesized large planet influencing their orbits, which could be either a super-Earth or a gas giant. One possibility is 2015 BP519, described as “the most extreme Trans-Neptunian Object discovered to date,” is actually a moon of the large planet, which some astronomers estimate to be ten times as massive as the Earth.

‘Nova Wonders’ Asks ‘What’s the Universe Made Of’ Tonight

May 30, 2018 12:00 am

When gravitational-wave detectors recorded a distant collision of two neutron stars, astronomers around the world got the call and began to search for visible evidence of the crash. A team in Chile from the Dark Energy Survey — as well as other groups — was able to detect the so-called kilonova's light, providing the first-ever observations of both light and gravitational waves from the same cosmic explosion. For the Dark Energy Survey crew, these observations will help gauge the universe's expansion rate, aiding their investigation into the mysterious dark energy pushing the universe apart. "What's the Universe Made Of" digs deep into two cosmic mysteries — dark matter and dark energy — showing how researchers know those entities exist, but also revealing that they are still trying to learn what they're made of and how they work.

© 2018 The Dark Energy Survey