Gravity’s Lens

Now that we as a nation have more or less scrapped our space program, it would be very easy to see NASA as kind of an aimless organization. Some of the more vocal supporters of science in the public sphere, like astrophysicist Neil deGrasse Tyson, think it’s downright shameful to lose that kind of ambition that helped define America’s greatness in the past (and I can’t say I disagree with that line of thinking). But NASA doesn’t seem to be planning to just drift off into obscurity so easily.  A press release issued today, October 24, announced the beginning of the Frontier Fields program, a collaborative effort between the three most powerful telescopes NASA has that plans to peer into new depths of the universe, using what is called “gravitational lensing.”


The Hubble, Spitzer, and Chandra telescopes will each focus on the same as-yet unstudied galaxy clusters, with each gathering a different type of information. The Hubble and Spitzer will work together to measure mass and distance more accurately than either could separately. As Peter Capak, principal investigator for the Spitzer arm of the project, says in the press release, “Hubble tells you which galaxies to look at and how many stars are being born in those systems. Spitzer tells you how old the galaxy is and how many stars have formed.” At the same time, data from the Hubble will be used to establish how dark matter is distributed throughout the six foreground galaxies.

Each of the three telescopes will monitor the galaxies at different ranges of light, that is, looking at different wavelengths of light. The Chandra telescope will focus on X-ray imaging, which will allow the project to determine both the mass of the objects studied and their gravitational force. This gravitational force data will then be used to better understand a phenomena that is integral to the project’s overall goal, gravitational lensing. Gravitational lensing is what will allow the three telescopes to peer deeper into the universe than we have yet seen.


Gravitational lensing is, quite frankly, just damn cool. It’s when the gravitational field of an object (like a galaxy) causes light to bend as it moves around the object, thus magnifying the light’s source. Basically it amounts to a naturally-occurring zoom lens surrounding those objects massive enough to generate the gravitational force necessary. Unlike an optical lens though, the gravitational lens has no focal point where the light hits just right and magnification occurs. Instead, gravitational lenses have a focal line. As long as an observer is along that line, the light source will appear magnified in a circle around the object. If the observer moves, it will appear only partially, as an arc segment, a section of a circle. When using a large and non-spherical object, like a galaxy, the magnification results in distortions and fragmentation, so that you have to do some crazy mathematical footwork to find your way back to a clear description of the light source. Once you do though, you can learn about how otherwise unreachable depths of the universe are put together, while also learning more about the object creating the lens.


It’s true that seeing the United States’ space program fall prey to budget cuts and apathy is disheartening. There was something very cool about the space program, something deeply rooted in human ambition and curiosity, and it is saddening to see that lost because of its financial cost. But work like this shows that the ambition and curiosity aren’t gone, they’ve just been deferred. And they’ll no doubt figure a way back up there eventually, given some time. For now though, we may not be able to send people further into space, but that’s no reason to stop exploring.

Original press release:


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