Archive for the ‘Universe’ Category

Mariner 4 Taught Us to See

Friday, August 30th, 2013
The first 'image' of Mars from NASA's Mariner 4
Mission team members for NASA’s Mariner 4 spacecraft, incredibly anxious to see the first up-close photograph of Mars, devised a way to see the image before it made its way to Earth by color-coding binary code on strips of ticker tape. The resulting collage became known as “the first image of Mars.” Image credit: NASA/JPL-Caltech

In today’s universe, it seems unimaginable that a planetary spacecraft would leave the comfort of its terrestrial perch without some kind of imaging system on board. But in the early 1960s, as NASA’s Jet Propulsion Laboratory was reveling in the success of its first planetary mission to Venus and setting its sights on Mars — a destination whose challenges would unfurl themselves much more readily than they had with Venus — for some scientists, the question of camera or none was still just that, a question.

Bud Schurmeier, project manager for NASA’s Ranger missions, a few years ago recalled, “There were a lot of scientists who said, ‘Pictures, that’s not science. That’s just public information.’ Over the years, that attitude has changed so markedly, and so much information has been obtained just from the photographs.”

The recent passing of former JPL Director and career-long planetary imaging advocate Bruce C. Murray, 81, is a reminder of how different our understanding of the planets — and our appreciation of them — would be without space-based cameras.

This truth was evident as early as 1965, when NASA’s Mariner 4, carrying an imaging system designed by a young Murray and his colleagues, arrived at Mars. It marked the world’s first encounter with the Red Planet, a remarkable achievement in itself. But for an anxious press, public and mission team, the Holy Grail lay in catching that first glimpse of Mars up-close.

It was a waiting game that was too much for some. For everyone, in fact:


This is a clip from the JPL-produced film The Changing Face of Mars about the laboratory’s early attempts to explore the Red Planet. Credit: NASA’s Jet Propulsion Laboratory

What resulted became known as “The first image of Mars.” And in many ways it symbolizes — more than any of the actual 22 photographs captured by Mariner 4 — how significant this opportunity to truly “see” Mars had been.

Now, nearly 50 years after Mariner 4’s arrival at Mars, imaging systems are an integral piece of our quest to understand the planets and the universe beyond, playing key roles in scientific investigations, spacecraft navigation and public support for missions. It’s because of that first image that we can now look at that red dot in the night sky and picture what has become our new reality of Mars:

Curiosity's first billion pixel panorama
This image is a portion of a billion-pixel panorama from NASA’s Mars rover Curiosity that combines 900 images taken by the rover from Oct. 5 through Nov. 16, 2012 from its “Rocknest” site on Mars. Image credit: NASA/JPL-Caltech
› Explore the full panorama

Rocks and Stars with Amy: This Year I Saw the Universe

Tuesday, February 1st, 2011

By Amy Mainzer

Rocks and Stars with Amy

With WISE, I roamed the skies — seeing everything from the closest asteroids to the most distant galaxies. When I was a kid, maybe 6 or 7, I remember reading the encyclopedia about Andromeda, Mars and Jupiter. After that, I spent a lot of my free time (and a fair amount of gym class) wishing that I could be “out there” exploring the stars, imagining what it must be like to get close to a black hole or the lonely, cold surface of a moon. Fast-forwarding several decades, I’ve just spent a tremendously satisfying and delightful year using some of our most sophisticated technology to see “out there” for real. It’s pretty cool when your childhood dreams come true!

Today, the operations team sent the command to kill the survey sequence and put WISE into a deep sleep. While I’m sad to see the survey stop, the real voyage of discovery is just getting started as we unpack the treasures that our spacecraft beamed back to us. Although I’m going to miss waking up to see a new slew of pictures fresh from outer space, what I’ve looked at so far is only a tiny fraction of the millions of images we’ve garnered. My colleagues and I are working nonstop now to begin the decades-long process of interpreting the data. But I can already say for certain that we’re learning that the universe is a weirder, more wonderful place than any science fiction I’ve ever read. If I could go back in time to when I was kid, I’d tell myself not to worry and to hang in there through the tough parts — it was all worth it.

A cast of hundreds, maybe thousands, of people have worked on WISE and deserve far more credit than they get. The scientists will swoop in and write papers, but all those results are squarely due to the brilliance, stubborn persistence and imagination of the technicians, managers, engineers of all stripes (experts in everything from the optical properties of strange materials to the orbital perturbations of the planets), and administrative staff who make sure we get home safely from our travels. Although we may not be able to fly people around the galaxy yet, one thing Star Trek got right is the spirit of camaraderie and teamwork that makes projects like WISE go. For the opportunity to explore the universe with such fine friends and teammates, I am truly grateful.


Rocks and Stars with Amy: This Asteroid Inspected by #32

Monday, November 15th, 2010

By Amy Mainzer

Rocks and Stars with Amy

Over the course of the nine months we’ve been operating WISE, we’ve observed over 150,000 asteroids and comets of all different types. We had to pick all of these moving objects out of the hundreds of millions of sources observed all over the sky — so you can imagine that sifting through all those stars and galaxies to find the asteroids is not easy!

We use a lot of techniques to figure out how to distinguish an asteroid from a star or galaxy. Even though just about everything in the universe moves, asteroids are a whole lot closer to us than your average star (and certainly your average galaxy), so they appear to move from place to place in the WISE images over a timescale of minutes, unlike the much more distant stars. It’s almost like watching a pack of cyclists go by in the Tour de France. Also, WISE takes infrared images, which means that cooler objects like asteroids look different than the hotter stars. If you look at the picture below, you can see that the stars appear bright blue, whereas the sole asteroid in the frame appears red. That’s because the asteroid is about room temperature and is therefore much colder than the stars, which are thousands of degrees. Cooler objects will give off more of their light at longer, infrared wavelengths that our WISE telescope sees. We can use both of these unique properties of asteroids — their motion and their bright infrared signatures — to tease them out of the bazillions of stars and galaxies in the WISE images.

Image of the first near-Earth asteroid discovered by WISE
The first near-Earth asteroid discovered by WISE (red dot) stands out from the stars (blue dots). The asteroid is much cooler than the stars, so it emits more of its light at the longer, infrared wavelengths WISE uses. This makes it appear redder than the stars. Image credit: NASA/JPL-Caltech/UCLA |   › Full image and caption

 
Thanks to the efforts of some smart scientists and software engineers, we have a very slick program that automatically searches the images for anything that moves at the longer, infrared wavelengths. With WISE, we take about a dozen or so images of each part of the sky over a couple of days. The system works by throwing out everything that appears again and again in each exposure. What’s left are just the so-called transient sources, the things that don’t stay the same between snapshots. Most of these are cosmic rays — charged particles zooming through space that are either spat out by our sun or burped up from other high-energy processes like supernovae or stars falling into black holes. These cosmic rays hit our detectors, leaving a blip that appears for just a single exposure. Also, really bright objects can leave an after-image on the detectors that can persist for many minutes, just like when you stare at a light bulb and then close your eyes. We have to weed the real asteroid detections out from the cosmic rays and after-images.

The data pipeline is smart enough to catch most of these artifacts and figure out what the real moving objects are. However, if it’s a new asteroid that no one has ever seen before, we have to have a human inspect the set of images and make sure that it’s not just a collection of artifacts that happened to show up at the right place and right time. About 20 percent of the asteroids that we observe appear to be new, and we examine those using a program that we call our quality assurance (QA) system, which lets us rapidly sift through hundreds of candidate asteroids to make sure they’re real. The QA system pops up a set of images of the candidate asteroid, along with a bunch of “before” and “after” images of the same part of the sky. This lets us eliminate any stars that might have been confused for the asteroids. Finally, since the WISE camera takes a picture every 11 seconds, we take a look at the exposures taken immediately before the ones with the candidate asteroid — if the source is really just an after-image persisting after we’ve looked at something bright, it will be there in the previous frame. We’ve had many students — three college students and two very talented high school students — work on asteroid QA. They’ve become real pros at inspecting asteroid candidates!

This is a screenshot from the WISE moving-object quality assurance system, which helps weed out false asteroid candidates.
This is a screenshot from the WISE moving-object quality assurance system, which helps weed out false asteroid candidates. The top two rows show an asteroid candidate detected in 16 different WISE snapshots, at two different infrared wavelengths. The lower rows show the same patch of sky at different times — they let the astronomers make sure that stars or galaxies haven’t been confused for the asteroid. Image credit: NASA/JPL-Caltech/UCLA

 
Meanwhile, the hunt continues — we’re still trekking along through the sky with the two shortest-wavelength infrared bands, now that we’ve run out of the super-cold hydrogen that was keeping two of the four detectors operating. Even though our sensitivity is lower, we’re still observing asteroids and looking for interesting things like nearby brown dwarfs (stars too cold to shine in visible light because they can’t sustain nuclear fusion). Our dedicated team of asteroid inspectors keeps plugging away, keeping the quality of the detections very high so that we leave the best possible legacy when our little telescope’s journey is finally done.


Rocks and Stars with Amy: Milestones

Tuesday, July 20th, 2010
Rocks and Stars with Amy
By Amy Mainzer

It’s hard to believe that we’ve just crossed the six-month mark on WISE — seems like just yesterday when we were all up at Vandenberg Air Force Base, near Santa Barbara, shivering in the cold at night while watching the countdown clock. But the time is flying (literally!) as WISE whips by over our heads. We’re analyzing data ferociously now, trying to get the images and the data ready for the public release next May. Even though the mission’s lifetime is short, we’ve gotten into a semblance of a routine. We receive and process images of stars, galaxies and other objects taken by the spacecraft every day, and we’re running our asteroid-hunting routine on Mondays and Thursdays. We’ve got a small army (well, okay, three — but they do the work of a small army!) of extremely talented students who are helping us verify and validate the asteroid detections, as well as hunt for new comets in the data. Plus, there is an unseen, yet powerful, cadre of observers out there all over the world following up our observations.

asteroids and comets detected by WISEThis plot shows asteroids and comets observed by NASA’s Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/ULCA/JHU   |   ›See related video

And so it’s come to pass that we’ve achieved some milestones. We completed our first survey of the entire sky on July 17 — and we just discovered our 100th new near-Earth object! That’s out of the approximately 25,000 new asteroids we’ve discovered in total so far; most of these hang out in the main belt between Mars and Jupiter and never get anywhere near Earth’s orbit. These new discoveries will allow us to conduct an accurate census of both the near-Earth and main belt asteroid populations. We’re really busy chewing on the data right now and calculating what it all means.

Because it’s so short, this mission reminds me a little bit of what the first days of college felt like — a tidal wave of new ideas, new sights and new thoughts. The pace of learning has been incredibly quick, whether I’m trying to get up to speed on asteroid evolution theories or tinkering with the software we use to write papers.

Speaking of papers, we’re in the process of preparing to submit several to science journals; in fact, I’ve already submitted one. The gold standard of science, of course, is the peer-review process. We submit our paper to a journal, and the scientific editor assigns another scientist who is an expert in the field but not involved in the project (and who usually remains anonymous) to read it and offer comments. The referee’s job is to “kick the tires,” so to speak, and ask tough questions about the work to make sure it’s sound. We get a chance to respond, and the referee gets a chance to respond to our responses, and then when everybody’s convinced the results are right, the paper is accepted and can be published. So stay tuned — we should have some of the first papers done soon telling us what these milestones mean for asteroid science.

› Read more from “Rocks and Stars with Amy”


Rocks and Stars with Amy: The Golden Ticket

Friday, January 29th, 2010

By Amy Mainzer

Rocks and Stars with Amy

We have discovered our first new near-Earth asteroid with WISE. Our first “golden ticket” is now known as 2010 AB78. It’s an asteroid that is roughly 1 kilometer [about .6 miles] in diameter, so it’s fairly large. The most interesting thing about it so far is that we thought we knew of about 85 percent of all the asteroids 1 kilometer and larger, so finding a big one like this is a little unusual. Of course, unlike Charlie and his chocolate bars, finding the golden ticket wasn’t a matter of luck, but a meticulous search process more like a busy assembly line.

Near-Earth objects are asteroids and comets with orbits that get close to Earth’s orbit. That doesn’t mean they are going to hit the Earth, of course. It’s sort of like driving on a busy street; just because there are a lot of cars zipping by on either side of you, it doesn’t necessarily mean your car is going to hit one. The cars would have to be at the same place at the same time for that to happen. So even though the paths each car has traveled might get close, there is no collision.

WISE finds asteroids by using a sophisticated piece of software called the WISE Moving Object Processing System, or WMOPS. When we first get a set of images from WISE, we have software that automatically searches the images for all the sources in them, be they stars, galaxies or asteroids. The software records their positions and how bright they are. WMOPS goes into that source list and figures out which sources are moving compared to the fixed stars and galaxies in each frame. Then, it figures out which sources are actually the same object — just observed at different times. So it’s a pretty smart piece of code. The whole system has to be highly automated, since when the WISE survey is done, the source catalog will contain several hundred million sources! You can imagine that trying to sort through all of these to find individual objects would be very challenging without a nifty program like WMOPS.

Our newest addition to the approximately 6,600 near-Earth Asteroids that are currently known is shown in this new image:

artist's concept of the WISE space telescope
The red dot at the center of this image is the first near-Earth asteroid discovered by NASA’s Wide-Field Infrared Survey Explorer, or WISE — an all-sky mapping infrared mission designed to see all sorts of cosmic objects. Image credit: NASA/JPL-Caltech/UCLA
› Full image and caption

2010 AB78 shows up like a glowing red ember at the center of the image, because it’s glowing brightly in infrared light with a wavelength of 12 microns, which is about 20 times redder than your eye can see. The stars appear blue, because they’re much hotter, and they emit proportionally less of their energy at these long wavelengths. The color that the asteroids appear to WISE is an important feature we use to distinguish them from other stars and galaxies, in addition to their motion.

With this first asteroid discovery, we are flexing our muscles in preparation for the heavy lifting we’re about to start.


Rocks and Stars with Amy: It’s Time to Go

Friday, December 11th, 2009

By Amy Mainzer

Rocks and Stars with Amy

Now that we are just days from launch (wow!), the team is making final decisions and preparations. We’ve just held our Flight Readiness Review, at which the final commitment to launch was made by NASA, the United Launch Alliance (the rocket folks) and the WISE project. It turns out that fueling our Delta II rocket’s second stage engine is an irreversible process — once we fuel the second stage, we have 34 days to launch the rocket. If we don’t launch within 34 days of fueling it, we have to replace the second stage completely — and that would mean taking WISE off the rocket. So we needed to be really sure that we were “go for launch” before we decided to fuel up the second stage. That is now done, and we are in the process of putting the final finishing touches on cooling down our solid hydrogen tanks.

These last few weeks and days before launch require a lot of flexibility of the team, since the schedule can change on a dime. There are about a million things having nothing to do with the launch vehicle or the spacecraft that can delay a launch — winds, too much fog, too many clouds, lightning and even something as mundane as a fishing boat or aircraft straying into the “keepout” zone that’s established around the launch site. You would think that the prospect of running into a giant, 330,000-pound rocket loaded with fuel would be enough to make people move out of the way, but sometimes they don’t seem to get the message! Any of these items is enough to scrub a launch attempt.

But that’s why we’ve built in the ability to make two consecutive launch attempts with WISE, separated by 24 hours. We get two tries. After that, our tank full of frozen hydrogen starts to warm up too much, and it takes two days for us to cool it back down. To keep the tank of frozen hydrogen a frosty 7 degrees above absolute zero (minus 447 Fahrenheit), we circulate an even colder refrigerant, liquid helium, around the outside of the tank. But the process of re-cooling takes two days; we have to hook all the hoses back up, cool everything down, then disconnect the hoses again before the next launch attempt.

So we have to be flexible. We’ve all put our lives on hold for the duration, since we have to be ready for anything that happens. Meanwhile, I’ve frantically tried to take care of stuff like cleaning the house and laying in supplies, because once WISE launches, things will go into overdrive. Needless to say, our families have all been very patient with us!


Rocks and Stars with Amy: Hi Ho, Hi Ho, It’s Into Space We Go

Thursday, November 5th, 2009

By Amy Mainzer

Rocks and Stars with Amy

With WISE a mere month away from liftoff, it’s probably a little late to be asking why we need to send it into space. But it’s worth taking the time to explain why we go to all the trouble of sending something up on a rocket. While it’s really cool to go into space, we’re not just sending WISE up there for the fun of it. In this case, there’s no other reasonable way to accomplish the mission’s science goals: surveying the entire sky in infrared, finding the nearest star to our sun, and finding the most luminous galaxy in the universe. We can’t do this from the ground.

artist concept of WISEIt turns out that the main culprit that drives us into space and into an orbit more than 500 kilometers (about 360 miles) above the Earth’s surface is our atmosphere. As wonderful as our atmosphere is for life on Earth, it wreaks havoc on astronomical images in many ways. For one, shifting pockets of warm and cool air drifting above a telescope — or a human observer– cause stars to twinkle. While pretty, this twinkling makes it difficult to get a good measurement of a star’s true brightness (or, in astronomical terms, its “photometry”). The twinkling also reduces the telescope’s sensitivity and resolution by enlarging the images it produces, making them blurrier and less sharp. This is true for all kinds of telescopes not just infrared ones.

Secondly, the atmosphere acts like a sponge at many wavelengths, soaking up light from the stars so that it never reaches the ground at all. Everybody’s seen a rainbow at one time or another, and that range of colors — from violet to red — spans the maximum range of wavelengths that our eyes can see. But that is only a small fraction of the entire spectrum of light that’s really out there in the universe. Our sun puts out most of its radiation in visible light, and most of that visible light makes it through our atmosphere to the ground. However, our atmosphere is only partially transparent to infrared wavelengths. Filled with water vapor, carbon dioxide, and methane, our atmosphere absorbs almost all infrared light, so most of the infrared light emitted by distant stars, asteroids, and planets doesn’t make it to observers on the ground. These molecules grab infrared light and trap it, preventing it from passing through the atmosphere (which is why they are called greenhouse gases). To see anything at all in most infrared colors, we have to get entirely above the Earth’s atmosphere.

The final problem posed by our atmosphere for infrared astronomers is that it — and the Earth itself — is warm. Infrared light is characteristically emitted by room-temperature objects. Objects like you and I glow brightly in infrared light, and so does the Earth and its atmosphere. If you could see in infrared light, the night sky would look as bright as daylight! So when we’re trying to detect the faint heat signatures of distant astronomical objects, a glowing, warm atmosphere is almost impossible to see through. This is why we must cool the WISE telescope to a mere 12 degrees above absolute zero (minus 438 Fahrenheit). Being in space with a cold telescope makes such a huge difference that the relatively modest-size WISE telescope, which is 40 centimeters (16 inches) in diameter, is equivalent in sensitivity to literally thousands of 8-meter (26-foot) telescopes on the ground. That small WISE telescope packs a punch.

So with that cleared up, we’re just about ready to put WISE into the nose cone and crane it up onto the Delta II rocket that’s waiting for us on the launch pad. Let’s go see some stars!


Five ‘Holy Grails’ of Distant Solar Systems

Thursday, June 11th, 2009
Angelle Tanner
Angelle Tanner

Angelle Tanner, a post-doctoral scholar at JPL and Caltech, studies planets in distant solar systems, called extrasolar planets. The golden prize in this field is to find a planet similar to Earth - the only planet we know that harbors life. While more than 350 extrasolar planets have been detected, most are gas planets, with no solid surface. Many are located in orbits closer to their parent star than Mercury is to the sun. In other words, not very similar to Earth.

Here’s Tanner’s short list of what she and her colleagues would love to find in another planet - the elements that might enable life on another world. With the powerful tools scientists have now and with new technology and missions coming soon, the odds are going up for finding an Earth-like planet, if one is out there.

Tanner’s top five “holy grails” of extrasolar planet research are hoped-for findings that she predicts will happen within the next 15 years.

1. First planet that weighs the same as Earth

Artist’s concept of an extraolar planet.
Artist’s concept of an extraolar planet.
Image credit: NASA/JPL-Caltech

Although most planets discovered have been giant gas planets with no surface, a handful of rocky planets, called super-earths, have also been detected. Super-earths are akin to Earth in their rocky make-up, but with a mass up to 10 times that of Earth.

There is no reason these planets could not host an atmosphere or even life as we know it. The discovery of a true Earth clone – Earth-like in size and make-up — could happen within a year or two. NASA’s recently launched Kepler mission has the ability to find planets as small as Earth.

2. First Earth-sized planet in the ‘habitable zone’

The so-called habitable zone is the area around a star where a rocky planet could have the right temperature to have liquid water on its surface. In our solar system, Earth sits in the habitable zone. Venus sits just inside the habitable zone and is too hot while Mars is just outside and too cold. Finding an Earth-sized planet is this geographically desirable location is the next big step in extrasolar research. One super-earth has already been detected near to its parent star’s habitable zone and it is only a matter of time — using existing technologies –- before a planet is found in this friendly environment. Ground-based telescopes and NASA’s Kepler mission are searching stars within a few hundred light years of Earth right now.

3. First atmosphere on a rocky planet

A planet’s atmosphere, along with other factors, helps determine whether a planet could sustain life. For the past few years, astronomers have studied the atmospheres of Jupiter-like, extrasolar planets. These gas giant planets have hydrogen-rich atmospheres inhospitable to life as we know it. However, many of the techniques developed for studying gas giants could be used to study the atmospheres of super-earths. This would mark an important step in beginning to understand the environment of rocky planets.

4. First hint of habitability and life

Once astronomers have enough Earth-sized planet atmospheres to study, they will be looking for biosignatures – indicators in a planet’s atmosphere that the planet might be hospitable to or even support life. Some of the molecules they will be looking for include water vapor, methane, ozone and carbon dioxide. NASA’s James Webb Space Telescope, scheduled to launch in 2014, will provide scientists with the sophisticated instruments needed for these potential observations on super-earths orbiting small stars. Assuredly, astrobiologists will be studying such data for years to come since potential life may, or may not be, in a form we expect. Keeping an open mind is critical.

5. The unexpected

The final grail — the unexpected. The history of science is marked with findings that were never predicted. As in all fields of science and exploration, it’s what we don’t know that will be the most exciting.

For more information about extrasolar planets, visit planetquest.jpl.nasa.gov


Almost There

Tuesday, March 3rd, 2009
Tracy Drain
by Tracy Drain
Systems Engineer

The Kepler mission, which will look for Earth-like planets, is nearing its scheduled March 6 launch date.

At our flight readiness review on February 4th, our deputy principal investigator, David Koch, took a few minutes to talk about the history of Johannes Kepler, the project’s namesake. Koch recapped Kepler’s tremendous contributions to the realm of astronomy 400 years ago, and reminded us all why our mission is so appropriately named for that great scientist. He also touched on the more recent history of the mission, reminding us how our science principal investigator, William Borucki, wrote his first paper on the possibility of detecting planets using the transit method back in the ’80s, and then in 1992 first proposed the mission that would later become Kepler. While I already knew most of those details, there was something special about hearing them again during that milestone review just one month away from launch. It gave a deeper, richer context to what we were all doing and made me even more excited about seeing this mission succeed. (If you are reading this David, thanks so much for doing that!)

Now here we are, less than a week away from launch. The entire team has been working so hard these last several weeks. The assembly, test and launch operations team has run the final major checkouts on the spacecraft at the Kennedy Space (I don’t think it’s Spaceflight) Center in Florida, and the spacecraft is now all buttoned up on top of the Delta II launch vehicle.

 Workers attach the two-part payload fairing over the Kepler spacecraft in preparation for launch.
Image above: Workers attach the two-part payload fairing over the Kepler spacecraft in preparation for launch. The cover, designed to jettison shortly after launch, protects the spacecraft from the friction and turbulence as it speeds through the atmosphere during launch. Image credit: NASA

The operations team has completed the final, full-up operational readiness test to rehearse the launch and early operations period. We’ve also completed the last pre-launch ground segment integration test and the commissioning operational readiness tests, which together validated the tools and procedures that we will use during that roughly two months of checkout after launch. We’re now in the home stretch: signing off the last few test reports, closing out the final action items — dotting and crossing those proverbial i’s and t’s.

And so we are nearly ready to go. In just a few days I will head off to Boulder, Colo., where I will join the part of the team located at the mission operations center to support launch and commissioning operations. We’re gearing up for an exciting campaign; I can hardly wait for this new phase to begin!


How We See Dark Matter

Monday, February 2nd, 2009
Dan Coe
by Dan Coe
Astronomer

Planets, stars, buildings, cars, you and I, we are all made of the same basic stuff - atoms, the building blocks of matter. The late Carl Sagan famously said “we are star stuff,” as the heavy elements in our bodies were all forged in supernovas, the explosions of dying stars. In a real scientific sense, we are one with everything we see in the night sky.

We have since learned that everything we see is awash in another kind of matter, a “dark” matter, made of particles yet to be discovered. Dark matter is all around us, but we cannot see it. Some estimate that a billion dark matter particles whiz through your body every second, but you cannot feel them. We now believe that the universe contains five times more dark matter than ordinary matter. While we all may be made of star stuff, we find that the universe is mostly made of something very different.

Why do we believe that dark matter exists? How can we study something that we cannot see or even feel? And how can we unravel the universe’s greatest mystery - what is this dark matter?

The idea of dark matter was born at Caltech in 1933. (Just three years later, JPL would be born there as the “rocket boys” began their first launch experiments.) In observations of a nearby cluster of galaxies named the Coma cluster, Fritz Zwicky calculated that the collective mass of the galaxies was not nearly enough to hold them together in their orbits. He postulated that some other form of matter was present but undetected to account for this “missing mass.” Later, in the 1970’s and ’80’s, Vera Rubin similarly found that the arms of spiral galaxies should fly off their cores as they are orbiting much too quickly.

galaxy cluster
In this Hubble image, the galaxy cluster Abell 2218 reveals its dark matter by lensing background galaxies into giant arcs. Image credit: NASA/JPL.

Today dark matter is a widely accepted theory, which explains many of our observations. My colleagues and I at JPL are among those working to reveal and map out dark matter structures. Dark matter is invisible. But astronomers can “see” it in a way and you can too, if you know what to look for! For instance, if you have a wineglass on a table and you look through the glass, the images behind it are distorted. So too when we look through a dense clump of dark matter, we see distorted and even multiple images of galaxies more distant. Matter bends space according to Einstein’s Theory of General Relativity, and light follows these bends to produce the distorted images. By studying these “lensed” images, we can reconstruct the shape of the lens, or in our case, the amount and distribution of dark matter in our gravitational lens.

Our observations of dark matter in outer space force particle physicists to revise their theories to explain what we see. Hopefully through their efforts, physicists will soon produce dark matter in the lab, catch and identify a small fraction of that which passes through us, and ultimately explain the relationship between dark matter and “star stuff.”