Hubble Opens Pandora’s Box, and Thousands of Galaxies Fly Out

The entire universe in blog form
Jan. 8 2014 10:46 AM

Hubble Opens Pandora’s Box, and Thousands of Galaxies Fly Out

Pandora's Cluster
Pandora's Cluster has hundreds of galaxies, and thousands upon thousands more are revealed in this dramatic Hubble image. Click to galactinate.

Photo by NASA,ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

As I was putting together my Best Astronomy Pictures of 2013 page, I was thinking that it had been a while since I had posted a jaw-dropping Hubble shot of galaxies. And then Hubble delivered.

That stunning image shows Abell 2744, a huge cluster of galaxies located a mind-numbing 4 billion light years away. Also known as Pandora's Cluster, it’s actually four separate clusters of galaxies undergoing a massive collision.


I suggest you grab a higher-resolution version of the image (there's even a monster 3900 x 4360 pixel version). When you peruse it, take note: not every object you see in it is part of the cluster. Not even close. If you zoom in, you’ll see lots of weird arcs and streaks:


Get this: Those are actually entire galaxies, located far, far behind the cluster. Pandora is so massive—400 trillion times the mass of our own Sun, a thousand times that of our entire galaxy—that its combined gravity literally bends space. Light from the more distant galaxies gets bent as it passes through space near the cluster, distorting our view of them. The cluster is what we call a gravitational lens because that’s exactly what’s going on: The gravity is bending light similar to the way a glass lens does. I have a more detailed explanation in an earlier post if you want the back story on how this works.

Another fun benefit from gravitational lenses is that they boost the light from more distant galaxies. At huge distances galaxies are faint, of course. But if the light from a galaxy is focused by the gravity of a cluster, it appears brighter to us. This means otherwise invisible galaxies can be seen! Some of the galaxies in the Hubble image are incredibly far away, 12 billion light years away. That means we see them less than 2 billion years after the Big Bang itself, when the Universe was young (it’s 13.8 billion years old now).

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

That’s why Hubble stared at this same spot in space for a whopping 67 hours: To get the deepest images ever of a gravitational lens, to take a census of the cluster itself, and to see the soul-crushingly distant galaxies behind it better than ever before—it’s why they call this the Frontier Field (similar to the series of Deep Field images Hubble has taken over the years).

In the final image, more than 3,000 such distant galaxies can be spotted, some of which have a mass only 1/1,000th of our own Milky Way. Hundreds of galaxies are seen in Pandora's Cluster, and in total some 10,000 galaxies are seen scattered throughout the image, both between Earth and the cluster, and well beyond. This image is so deep that astronomers can actually see the light from stars in Pandora's Cluster that have been stripped out of their parent galaxies, victims of gravitational collisions between the galaxies.

This image is stunning. Back in the day, when I was gainfully employed calibrating and processing Hubble data, I worked with a few very deep ones. You could see galaxies strewn through them, scattered like plant seeds on the wind. The work to whip the images into shape was generally fairly routine, even tedious at times, but then sometimes I’d suddenly see them for what they really were: Trillions upon countless trillions of stars, each photon of light in the image from these distant suns having traveled billions of years, losing energy as they swam upstream against the expansion of the Universe, finally stopping after that long, long journey when they hit the camera orbiting hundreds of kilometers above the Earth.

I’d stop dead in my work, gaping, the hair on the back of my neck rising as those thoughts seeped into my brain. Even if you don’t understand the science, can’t grasp the physics, then know this: We humans yearn to reach across the Universe, to understand all that we see. And then we actually do this. When we try, we can see very, very far indeed.



Crying Rape

False rape accusations exist, and they are a serious problem.

Scotland Is Just the Beginning. Expect More Political Earthquakes in Europe.

Why Men Can Never Remember Anything

The XX Factor
Sept. 19 2014 1:11 PM Why Men Can Never Remember Anything

The Music Industry Is Ignoring Some of the Best Black Women Singing R&B

How Will You Carry Around Your Huge New iPhone? Apple Pants!

Medical Examiner

The Most Terrifying Thing About Ebola 

The disease threatens humanity by preying on humanity.


The Other Huxtable Effect

Thirty years ago, The Cosby Show gave us one of TV’s great feminists.

There’s a Way to Keep Ex-Cons Out of Prison That Pays for Itself. Why Don’t More States Use It?

No, New York Times, Shonda Rhimes Is Not an “Angry Black Woman” 

Brow Beat
Sept. 19 2014 1:39 PM Shonda Rhimes Is Not an “Angry Black Woman,” New York Times. Neither Are Her Characters.
Sept. 19 2014 11:33 AM An Up-Close Look at the U.S.–Mexico Border
  News & Politics
Sept. 19 2014 1:56 PM Scotland’s Attack on the Status Quo Expect more political earthquakes across Europe.
Sept. 19 2014 12:09 PM How Accelerators Have Changed Startup Funding
Inside Higher Ed
Sept. 19 2014 1:34 PM Empty Seats, Fewer Donors? College football isn’t attracting the audience it used to.
  Double X
The XX Factor
Sept. 19 2014 1:11 PM Why Men Never Remember Anything
  Slate Plus
Slate Picks
Sept. 19 2014 12:00 PM What Happened at Slate This Week? The Slatest editor tells us to read well-informed skepticism, media criticism, and more.
Brow Beat
Sept. 19 2014 2:44 PM Where Do I Start With Mystery Science Theater 3000?
Future Tense
Sept. 19 2014 12:38 PM Forward, March! Nine leading climate scientists urge you to attend the People’s Climate March.
  Health & Science
Medical Examiner
Sept. 19 2014 12:13 PM The Most Terrifying Thing About Ebola  The disease threatens humanity by preying on humanity.
Sports Nut
Sept. 18 2014 11:42 AM Grandmaster Clash One of the most amazing feats in chess history just happened, and no one noticed.