Dark Energy Camera Sees Universe Through A Comet’s Tail

At the time this image was taken, the comet was passing about 51 million miles from Earth – a short distance for the Dark Energy Camera, which is sensitive to light up to 8 billion light years away. Each of the rectangular shapes above represents one of the 62 individual fields of the camera. Click to explore the original, hi-res image. Credit:
Comet Q2 Lovejoy on December 27, 2014. At the time this image was taken, the comet was passing about 51 million miles from Earth – a short distance for the Dark Energy Camera, which is sensitive to light up to 8 billion light years away. Each of the rectangular shapes above represents one of the 62 individual fields of the camera. Click to explore the original, hi-res image. Credit: Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny

Not a bad photo considering no one planned to shoot this picture of Comet Lovejoy with the  world’s most powerful digital camera. That’s right. The comet just happened to “be in the way” during a scan made by the Dark Energy Camera. A member of the observing team said it was a “shock” to see the comet appear on the computer screen.

An assortment of galaxies including this spiral appear through the tail of Comet Q2 Lovejoy on December 27, 2014 during one of the new Dark Energy Camera's scans of the sky. Credit: Fermilab’s Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny
An assortment of galaxies including this pretty spiral appear shine through a small section of Lovejoy’s tail on December 27, 2014 during one of the Dark Energy Camera’s scans of the sky. Credit: Fermilab’s Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny

While the detail in the comet is spectacular, what’s behind it is equally amazing. The image represents a narrow but deep slice into the body of the cosmos, revealing hundreds of distant galaxies beyond the green veil of Lovejoy’s tail. I’ve sectioned off a few portions, but I encourage you to download and explore the original file and see the rest for yourself. We’ve all read there are billions of galaxies out there, but seeing them twinkling beyond the comet gives us a visceral feel of how deep the universe goes.

The camera, a 570 megapixel beast with lenses up to a yard across, is mounted on the 157-inch (4-meter) Victor M. Blanco telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in the Andes Mountains in Chile. With a 2.2° field of view (much larger than most professional telescopes) and the ability to see light from more than 100,000 galaxies up to 8 billion light-years away in each snapshot, it forms the heart of the Dark Energy Survey (DES).

Another serving of galaxy salad. Credit:
Serving up another helping  of galaxy salad. Credit: Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny

Dark energy is the name given to whatever is causing the universe to accelerate. No one went looking for it, but studies of the brightnesses of extremely distant supernovae in the 1990s turned up a phenomenal increase in the expansion rate of the universe when viewed across billions of light years. Now we’re stuck trying to figure out what it is. If anything, most astronomers expected cosmic expansion to slow down as predicted by Einsteins’ Theory of Relativity. Nope.

Overall, dark energy is thought to comprise 73% of all the mass and energy in the universe. 23% is unseen dark matter known only through its gravitational prowess, leaving just 4% ordinary matter for hamburgers, stars and cars.

How the universe divvies up its energy/matter. Credit: NASA
How the universe divvies up its energy/matter. Credit: NASA

The DES designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. The survey will probe dark energy on four fronts:

* Counting galaxy clusters: Dark matter and galaxies’ own gravity hold clusters together, but dark energy tries to pull the clusters apart. The camera will photograph 100,000 clusters across billions of light years of space and time. Counting clusters and mapping their distribution will help us understand how dark energy battles gravity for the fate of the universe.

* Measuring supernovae brightnesses and distances to better determine the expansion rate of the universe. 4,000 new supernovae are expected to be found with the camera.

Fermilab astrophysicist Tom Diehl inspects the Dark Energy Camera.
Fermilab astrophysicist Tom Diehl inspects the 570-megapixel Dark Energy Camera. A high-end consumer camera like the Canon D5 has a full-frame 22.3 megapixel “chip”. Credit: Fermilab

* Studying how dark energy interacts with dark matter. The light of distant galaxies is bent and distorted when it passes around dark matter, warping their shapes. The survey will measure those shapes to see what role dark energy plays in the interaction.

* When the universe was less than 400,000 years old, matter and light interacted to set off a series of sound waves which left an imprint on how galaxies are distributed throughout the universe. The survey will measure the positions in space of 300 million galaxies to find this imprint and use it to infer the history of cosmic expansion.

Even if we don’t track down the nature of dark energy in our lifetime, we can sure enjoy the side benefits of pictures like this one.

4 Responses

  1. Edward M. Boll

    With Lovejoy fading I am looking ahead to this Fall with US Catalina 10. The BAA early on predicted about magnitude 0 in November. Now they are saying 2. I would say 0 may yet be possible. I doubt if it would be any brighter than that.

  2. Thanks Bob. Unprecedented picture of Q2.
    Would that be the 1st digital astro-photographic photo bomb?
    But the coma, the dust and ionized gas (aka to a minority as plama) is making the extra-galactic plasmoid filaments almost impossible to detect against the background noise of the gracity defeating electro-magnetism greatness.
    😉

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