The Eagle Nebula's pillars of creation taken in 1995 (right) and 2015. The new image was obtained with the Wide Field Camera 3, installed by astronauts in 2009. Credit: Left: NASA, ESA/Hubble and the Hubble Heritage Team. Right: NASA, ESA/Hubble, STScI, J. Hester and P. Scowen (Arizona State University)
When you look at that image on the right, make sure to thank the STS-125 crew. And all the people who defended the idea of sending one last repair mission to the Hubble Space Telescope before the space shuttle was decommissioned.
That’s because the famous “Pillars of Creation” image taken in 1995 by Hubble just got a huge upgrade. Using a camera the astronauts installed in 2009, astronomers recently revisited the iconic image and got far more detail this time around. And please, do yourself a favor to click through and see the ethereal infrared image Hubble got at the same time.
Embedded in these Eagle Nebula towers, which are sometimes called elephant trunks, are stars under creation. And in a short span of 20 years, you can see how the stars are slowly blowing the pillars apart. This is leading some press officials to call the structures “pillars of destruction.” And astronomers can chart how everything is changing over time.
“I’m impressed by how transitory these structures are. They are actively being ablated away before our very eyes,” stated Paul Scowen of Arizona State University in Tempe, one of the astronomers who led the 1995 observations.
The Eagle Nebula’s pillars of creation captured in infrared light with the Hubble Space Telescope, in 2015. Credit: NASA, ESA/Hubble and the Hubble Heritage Team
“These pillars represent a very dynamic, active process,” Scowen added. “The gas is not being passively heated up and gently wafting away into space. The gaseous pillars are actually getting ionized (a process by which electrons are stripped off of atoms) and heated up by radiation from the massive stars. And then they are being eroded by the stars’ strong winds (barrage of charged particles), which are sandblasting away the tops of these pillars.”
One large find from the two images showed a “narrow jet-like feature” that could have been emanating from a brand-new star. It’s been getting larger over the past two decades, moving more than 60 billion miles further into the universe.
The new images were presented at the American Astronomical Society meeting in Seattle this week.
A new Avengers movie. A reboot of the Star Wars franchise. The final installment of the Hunger Games. The Martian makes it to the big screen. Yup, even if the zombie apocalypse occurs in 2015, it’ll still be a great year. But trading science fiction for fact, we’re also on track for a spectacular year in space science and exploration as well.
Humanity will get its first good look at Ceres and Pluto, giving us science writers some new pics to use instead of the same half dozen blurry dots and artist’s conceptions. SpaceX will also attempt a daring landing on a sea platform, and long duration missions aboard the International Space Station will get underway. And key technology headed to space and on Earth may lead the way to opening up the window of gravitational wave astronomy on the universe. Here’s 10 sure-fire bets to watch for in the coming year from Universe Today:
LISA Pathfinder deployed at L1. Credit: ESA/Artist’s concept.
10. LISA Pathfinder
A precursor to a full-fledged gravitational wave detector in space, LISA Pathfinder will be launching atop a Vega rocket from Kourou, French Guiana in July 2015. LISA stands for the Laser Interferometer Space Antenna, and the Pathfinder mission will journey to the L1 Lagrange point between the Earth and the Sun to test key technologies. LISA Pathfinder will pave the way for the full fledged LISA space platform, a series of three free flying spacecraft proposed for launch in the 2030s.
Looking down one of the arms of LIGO Hanford. Credit: Photo by author.
9. AdLIGO Goes Online
And speaking of gravitational waves, we may finally get the first direct detection of the same in 2015, when Advanced LIGO is set to go online. Comprised of two L-shaped detectors, one based in Livingston Louisiana, and another in Hanford Washington, AdLIGO will feature ten times the sensitivity of the original LIGO observatory. In fact, as was the case of the hunt for the Higgs-Boson by CERN, a non-detection of gravitational waves by AdLIGO would be a much stranger result!
A replica of the Hubble Space Telescope on display at the Kennedy Space Center. Credit: Photo by author.
8. Hubble Turns 25
Launched on April 24th, 1990 aboard the Space Shuttle Discovery, the Hubble Space Telescope celebrates 25 years in space in 2015. The final servicing mission in 2009 gave Hubble a reprieve from the space junk scrap heap, and the orbiting telescope is still going strong. Hubble has no less than pushed the limits in modern astronomy to become a modern icon of the space age.
MESSENGER wraps up its mission in 2015. Credit: NASA/MESSENGER/JPL/APL.
7. The End of MESSENGER
NASA’s Mercury exploring spacecraft wraps up its mission next year. Launched in 2004, MESSENGER arrived in orbit around Mercury after a series of flybys on March 18th, 2011. MESSENGER has mapped the innermost world in detail, and studied the space environment and geology of Mercury. In late March 2015, MESSENGER will achieve one final first, when it impacts the surface of Mercury at the end of its extended mission.
Akatsuki on Earth prior to departure. Credit: JAXA.
6. Akatsuki at Venus
This Japanese spacecraft missed orbital insertion a few years back, but gets a second chance at life in 2015. Launched in 2010 atop an H-IIA rocket from the Tanegashima Space Center in Japan, Akatsuki failed to enter orbit around Venus at the end of 2010, and instead headed out for a heliocentric path around the Sun. Some quick thinking by JAXA engineers led to a plan to attempt to place Akatsuki in Venusian orbit in November 2015. This would be a first for the Japanese space agency, as attempts by JAXA at placing a spacecraft in orbit around another planet – including the Mars Nozomi probe – have thus far failed.
The target for the Falcon-9 first stage later next week. Credit: SpaceX.
5. SpaceX to Attempt to Land on a Sea Platform
It’ll definitely rock if they pull it off next week: on January 6th, a SpaceX Falcon 9 rocket will lift off from Cape Canaveral with its Dragon spacecraft headed to the International Space Station on mission CRS-5. Sure, these resupply missions are becoming routine, but after liftoff, SpaceX is attempting something new and daring: landing the Falcon-9 first stage Buck Rodgers style, “fins first” on a floating barge. This is the next step in ultimately proving the feasibility of having the rocket fly back to the launch site for eventual reuse. If nothing else, expect some stunning video of the attempt soon!
An artist’s concept of an asteroid retrieval mission. Credit: NASA.
4. NASA to Decide on an Asteroid Mission
Some major decisions as to the fate and the future of manned space exploration are due next year, as NASA is expected to decide on the course of action for its Asteroid Redirect Mission. The current timeline calls for the test of the SLS rocket in 2018, and the launch of a spacecraft to recover an asteroid and place it in orbit around the Moon in 2019. If all goes according to plan – a plan which could always shift with the political winds and future changes in administrations – we could see astronauts exploring a captured asteroid by the early 2020s.
Astronaut Scott Kelly (left), and cosmonaut Mikhail Korniyenko. Credit: NASA/Roscomos.
3. Long Duration ISS Missions
Beginning in 2015, astronauts and cosmonauts will begin year-long stays aboard the ISS to study the effects of long duration space missions. In March of 2015, cosmonaut Mikhail Korniyenko and U.S. astronaut Scott Kelly will launch as part of Expedition 43 headed to the ISS. The Russians have conducted stays in space longer than a year aboard the Mir space station, but Kelly’s stay aboard the ISS will set a duration record for NASA astronauts. Perhaps, a simulated “Mars mission” aboard the ISS could be possible in the coming years?
An artist’s concept of Dawn approaching 1 Ceres. Credit: NASA/JPL.
2. Dawn at Ceres
Fresh off of exploring Vesta, NASA’s Dawn spacecraft will become the first mission to enter orbit around a second object, the asteroid 1 Ceres next year in April 2015. The largest asteroid and the first object of its kind discovered on the first day of the 19th century, Ceres looks to be a fascinating world in its own right. Does it possess water ice? Active geology? Moons of its own? If Dawn’s performance at Vesta was any indication, we’re in for another exhilarating round of space exploration!
And artist’s conception of New Horizons at Pluto. Credit: NASA/JPL/Thierry Lombry.
1. New Horizons at Pluto
An easy No. 1,we finally get our first good look at Pluto in July, as NASA’s New Horizons spacecraft flies less than 14,000 kilometres from the surface of the distant world. Launched in 2006, New Horizons will “thread the needle” between Pluto and Charon in a flurry of activity as it passes by. New Horizons will then turn back as it passes into the shadows of Pluto and Charon and actually view the two worlds as they occult the distant Sun. And from there, New Horizons will head out to explore Kuiper Belt Objects of opportunity.
And these are just the top stories that are slated to be big news in space in 2015. Remember, another Chelyabinsk meteor or the next big comet could drop by at any time… space news can be unpredictable, and its doubtless that 2015 will have lots more surprises in store.
Rendering showing the location and size of water vapor plumes coming from Europa's south pole. Credit: NASA/ESA/L. Roth/SWRI/University of Cologne
It was about this time last year that Europa really began to excite us again. Following a sci-fi movie about the Jupiter moon, astronomers using the Hubble Space Telescope announced they had found possible water vapor near the icy moon — maybe from geysers erupting from its icy surface. (That is, if the finding was not due to signal noise, which researchers acknowledged at the time.)
As NASA ramped up (distant) plans to get close to Europa again, scientists began plumbing data from the Cassini spacecraft to see if its glance at the moon circa 2001 revealed anything. Turns out that the spacecraft didn’t see any sign of a plume. Which leads to the greater question, what is happening?
Now scientists are scurrying for a second look. Hubble is in the midst of a six-month search of the moon (from afar) to see if any more of the plumes are showing up. Now the theory is that the plumes, if they do exist, would be intermittent — at least, that’s according to the team looking at data from Cassini’s ultraviolet imaging spectograph (UVIS).
Europa (bottom left) in orbit around its planet, Jupiter, as spotted from the Cassini spacecraft in 2000. Credit: NASA/JPL/University of Arizona
“It is certainly still possible that plume activity occurs, but that it is infrequent or the plumes are smaller than we see at Enceladus,” stated co-author Amanda Hendrix, a Cassini UVIS team member with the Planetary Science Institute in Pasadena. “If eruptive activity was occurring at the time of Cassini’s flyby, it was at a level too low to be detectable by UVIS.”
This finding was part of a greater set of observations showing that it’s not really Europa that is contributing plasma (superheated gas) to space — it’s the ultra-volcanic moon Io. And Europa itself is sending out 40 times less oxygen than previously believed to the area surrounding the moon.
“A downward revision in the amount of oxygen Europa pumps into the environment around Jupiter would make it less likely that the moon is regularly venting plumes of water vapor high into orbit, especially at the time the data was acquired,” NASA stated. This would stand in contrast to, say, Saturn’s Enceladus — which Cassini has seen sending plumes high above the moon’s surface.
The findings were presented at the American Geophysical Union meeting earlier this month and also published in the Astrophysical Journal. The research was led by Don Shemansky, a Cassini UVIS team member with Space Environment Technologies.
Vesta seen from the Earth-orbit based Hubble Space Telescope in 2007 (left) and up close with the Dawn spacecraft in 2011. Hubble Credit: NASA, ESA, and L. McFadden (University of Maryland). Dawn Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Photo Combination: Elizabeth Howell
The Hubble Space Telescope is one of the best observatories humanity has. It’s been operating for nearly 25 years in space, is still highly productive, and is a key element to mission planning for NASA as it sends spacecraft out into the Solar System. When the agency was getting ready to send Dawn to Vesta, for example, it took pictures to help with calibration.
Then Dawn got up close to the dwarf planet in 2011 and found a few surprises — liquid water that possibly flowed temporarily on the surface, for example. And as the spacecraft draws near to Ceres for a close encounter next year, it also will be looking for water — in the form of its atmosphere.
That’s following on from research out of the Herschel Space Telescope published earlier this year, showing that Ceres has a thin water vapor atmosphere surrounding the dwarf planet. It could be producing water similarly to how a comet does, through sublimation, but investigators won’t know much until they get close-up.
“Ceres has some sort of mechanism that’s putting out water vapor and causing a thin, temporary atmosphere,” said Keri Bean, a mission operations engineer at the Jet Propulsion Laboratory who works on Dawn, in a Google+ Hangout yesterday (Dec. 11). “I think that we’re going to try to look into this, and we don’t know what else Ceres will have in store for us.”
Ceres as seen from the Earth-based Hubble Space Telescope in 2004 (left) and with the Dawn spacecraft in 2014 as it approached the dwarf planet. Hubble Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), L. McFadden (University of Maryland, College Park), and M. Mutchler and Z. Levay (STScI). Dawn Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Photo Combination: Elizabeth Howell
Dawn is now so close to Ceres that its pictures will soon exceed the best ones Hubble had to offer. The image above (at right) is modest compared to the space telescope, but in a planned photo session Jan. 26 Dawn will have slightly better pictures than Hubble. By Feb. 4 they will be twice as good in quality and then seven times as good Feb. 20.
The spacecraft’s images not only have science purposes, as they let investigators study the surface, but also serve as optical navigation aids. Ceres is a tiny body and hard to navigate to from far away, so as it gets closer these pictures are crucial for Dawn to figure out where to go next.
Dawn will get its close-up of Ceres in the spring when it arrives at the dwarf planet. To get the latest on the mission, check out the entire Google+ Hangout from yesterday.
"AstroButch [Butch Wilmore] has set up our Xmas tree in the lab and hung socks for us," tweeted astronaut Samantha Cristoforetti from the International Space Station Dec. 7, 2014. Credit: Samantha Cristoforetti/Twitter
If you think the upside-down Christmas tree above is bizarre — that’s one of the latest activities of Expedition 42 astronauts in space right now — think back to the history of other holidays in orbit.
We’ve seen a vital telescope undergo repairs, an emergency replacement of part of a space station’s cooling system, and even a tree made of food cans. Learn more about these fun holiday times below.
Reading from above the moon (Apollo 8, 1969)
In this famous reading from the Bible, astronauts Frank Borman, Jim Lovell and Bill Anders shared their experience looking at the Moon on Dec. 24, 1968. The Apollo 8 crew was the first to venture to lunar orbit, just seven months before the Apollo 11 crew made it all the way to the surface.
Food can “Christmas tree” (Skylab 4, 1973)
A “Christmas tree” created out of food cans by the Skylab 4 crew in 1973. Credit: NASA
Living on the Skylab station taught astronauts the value of improvisation, such as when the first crew (under NASA’s instructions) repaired a sunshield to stop electronics and people from roasting inside. Skylab 4 took the creativity to Christmas when they created a tree out of food cans.
Hubble Space Telescope repair (STS-103, 1999)
The Hubble Space Telescope during a 1999 repair mission with STS-103 crew members Mike Foale (left, for NASA) and Claude Nicollier (European Space Agency). Credit: NASA
When the Hubble Space Telescope was in hibernation due to a failed gyroscope, the STS-103 crew made repairs in December 1999 that culminated with the final spacewalk on Christmas Day. The telescope remains in great shape to this day, following another repair mission in 2009.
First Christmas on the International Space Station (Expedition 1, 2000)
The Expedition 1 crew with fresh oranges on the International Space Station in December 2000. From left, Yuri Gidzenko (Roscosmos), Bill Shepherd (NASA) and Sergei Krikalev (Roscosmos). Credit: NASA
The Expedition 1 crew was the first on the International Space Station to spend Christmas in orbit. “On this night, we would like to share with all-our good fortune on this space adventure; our wonder and excitement as we gaze on the Earth’s splendor; and our strong sense — that the human spirit to do, to explore, to discover — has no limit,” the crew said in a statement on Christmas Eve, in part.
Ammonia tank replacement (Expedition 38, 2013)
Just last year, an ammonia tank failure crippled a bunch of systems on the International Space Station and forced spacewalkers outside to fix the problem, in the middle of a leaky suit investigation. The astronauts made the final repairs ahead of schedule, on Christmas Eve.
But that didn’t come cheap. Four astronaut servicing missions (including one to fix a mirror that was launched with myopia) were required to keep the telescope going since 1990. Hubble has never been more scientifically productive, according to a recent NASA review, but a new article asks if Hubble is destined to die a fiery death when its orbit decays in the next eight to 10 years.
“NASA doesn’t have any official plans for upgrading the telescope, meaning its hardware will grow old and out-of-date in the coming years,” reads the article in Popular Science. “Without assistance, Hubble can’t maintain its orbit forever, and eventually Earth’s gravity will pull the telescope to a fiery death.”
That’s not to say NASA is going to abandon the cosmos — far from it. Besides NASA’s other space telescopes, the successor James Webb Space Telescope is planned to launch in 2018 to chart the universe in other wavelengths. But a review from April warns that ceasing operations of Hubble would not be prudent until James Webb is up, running, and doing its own work productively. That’s a narrow window of time considering Hubble is expected to work well until about 2020.
The Hubble Space Telescope shows the shrinking size of Jupiter’s Great Red Spot in this series of images taken between 1995 and 2014. Credit: NASA, ESA, and A. Simon (Goddard Space Flight Center)
The Hubble Space Telescope senior review panel submitted a report on March that overall praised the observatory’s work, and which also talked about its potential longevity. As is, Hubble is expected to work until at least 2020, the review stated. The four science instruments are expected to be more than 85% reliable until 2021, and most “critical subsystems” should exceed 80% until that same year.
The report urges that experienced hands are kept around as the telescope degrades in the coming years, but points out that Hubble has backups that should keep the observatory as a whole going for a while.
There are no single-point failure modes on Hubble that could take down the entire observatory. It has ample redundancy. Planned mitigations for numerous possible sub-system failures or degraded performance have been developed in advance via the project’s Life-Extension Initiatives campaign. Hubble will likely degrade gracefully, with loss or degradation of individual science instrument modes and individual sub-system components.
In NASA’s response to the Senior Review for several missions (including Hubble), the agency said that the telescope has been approved (budgetarily speaking) until 2016, when an incremental review will take place. Further in the future, things get murky.
The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)
The just-tested Orion spacecraft won’t be ready to take crews until the mid-2020s, and so far (according to the Popular Science article) the commercial crew program isn’t expected to include a servicing mission.
According to STS-125 astronaut Michael Good, who currently serves in the Commercial Crew Program, the space agency isn’t looking into the possibility of using private companies to fix Hubble, but he says there’s always a chance that could happen. “One of the reasons we’re doing Commercial Crew is to enable this capability to get into lower Earth orbit,” says Good. “But it’s certainly in the realm of possibility.”
Much can happen in a decade — maybe a surge in robotic intelligence would make an automated mission more possible — but then there is the question of priorities. If NASA chooses to rescue Hubble, are there other science goals the agency would need to push aside to accomplish it? What is best? Feel free to leave your feedback in the comments.
Eta Carinae from Hubble's STIS instrument. Credit: NASA, ESA, and the Hubble SM4 ERO Team
Wow! One of the most famous star explosions captured by the Hubble Space Telescope — several times — shows clear evidence of expansion in this new animation. You can see here the Homunculus Nebula getting bigger and bigger between 1995 and 2008, when Hubble took pictures of the Eta Carinae star system. More details from one of the animation authors below.
“I had the idea to check the Hubble image of Eta Carinae because I know this star rather well,” wrote Philippe Henarejos, one of the authors of the animation, in an e-mail to Universe Today. Henarejos has written several times about the star for the magazine he edits, Ciel et espace (Sky and Space) and also published a French-language book on star histories.
“Telling this story, I realized that astronomers knew for a long time that the Homunculus Nebula was expanding. Also, I knew that the HST had taken many photos of this object since 1995. So I thought that thanks to the very high resolution of the HST images, it could be possible to see the expansion.”
Eta Carinae from Hubble’s STIS instrument. Credit: NASA, ESA, and the Hubble SM4 ERO Team
Along with colleague Jean-Luc Dauvergne, Henarejos tracked down two images in the archives and searched for a fixed object that wouldn’t be moving as the expansion occurred, which they decided would be two stars close to the border of the field of view. Then Dauvergne found a third image that clearly showed the expansion happening.
The two gentlemen then verified their findings with astronomer John Martin from the University of Illinois, who maintains a page on Eta Carinae. “He told me that the expansion is real,” Henarejos said.
Eta Carinae mysteriously brightened about 170 years ago, becoming the second-most luminous object in Earth’s night sky. Then it faded 150 years ago. Astronomers are still examining the system to see what might have caused this.
A beautiful image of Sasturns tiny moon Daphnis, but where is all the color?
If NASA is so advanced, why are their pictures in black and white?
It’s a question that I’ve heard, in one form or another, for almost as long as I’ve been talking with the public about space. And, to be fair, it’s not a terrible inquiry. After all, the smartphone in my pocket can shoot something like ten high-resolution color images every second. It can automatically stitch them into a panorama, correct their color, and adjust their sharpness. All that for just a few hundred bucks, so why can’t our billion-dollar robots do the same?
The answer, it turns out, brings us to the intersection of science and the laws of nature. Let’s take a peek into what it takes to make a great space image…
Perhaps the one thing that people most underestimate about space exploration is the time it takes to execute a mission. Take Cassini, for example. It arrived at Saturn back in 2004 for a planned four-year mission. The journey to Saturn, however, is about seven years, meaning that the spacecraft launched way back in 1997. And planning for it? Instrument designs were being developed in the mid-1980s! So, when you next see an astonishing image of Titan or the rings here at Universe Today, remember that the camera taking those shots is using technology that’s almost 30 years old. That’s pretty amazing, if you ask me.
But even back in the 1980s, the technology to create color cameras had been developed. Mission designers simply choose not to use it, and they had a couple of great reasons for making that decision.
Perhaps the most practical reason is that color cameras simply don’t collect as much light. Each “pixel” on your smartphone sensor is really made up of four individual detectors: one red, one blue, two green (human eyes are more sensitive to green!). The camera’s software combines the values of those detectors into the final color value for a given pixel. But, what happens when a green photon hits a red detector? Nothing, and therein lies the problem. Color sensors only collect a fraction of the incoming light; the rest is simply lost information. That’s fine here on Earth, where light is more or less spewing everywhere at all times. But, the intensity of light follows one of those pesky inverse-square laws in physics, meaning that doubling your distance from a light source results in it looking only a quarter as bright.
That means that spacecraft orbiting Jupiter, which is about five times farther from the Sun than is the Earth, see only four percent as much light as we do. And Cassini at Saturn sees the Sun as one hundred times fainter than you or I. To make a good, clear image, space cameras need to make use of all the little light available to them, which means making do without those fancy color pixels.
A mosaic of images through different filters on NASA’s Solar Dynamics Observatory. Image credit: NASA/SDO/Goddard Space Flight Center
The darkness of the solar system isn’t the only reason to avoid using a color camera. To the astronomer, light is everything. It’s essentially our only tool for understanding vast tracts of the Universe and so we must treat it carefully and glean from it every possible scrap of information. A red-blue-green color scheme like the one used in most cameras today is a blunt tool, splitting light up into just those three categories. What astronomers want is a scalpel, capable of discerning just how red, green, or blue the light is. But we can’t build a camera that has red, orange, yellow, green, blue, and violet pixels – that would do even worse in low light!
Instead, we use filters to test for light of very particular colors that are of interest scientifically. Some colors are so important that astronomers have given them particular names; H-alpha, for example, is a brilliant hue of red that marks the location of hydrogen throughout the galaxy. By placing an H-alpha filter in front of the camera, we can see exactly where hydrogen is located in the image – useful! With filters, we can really pack in the colors. The Hubble Space Telescope’s Advanced Camera for Surveys, for example, carries with it 38 different filters for a vast array of tasks. But each image taken still looks grayscale, since we only have one bit of color information.
At this point, you’re probably saying to yourself “but, but, I KNOW I have seen color images from Hubble before!” In fact, you’ve probably never seen a grayscale Hubble image, so what’s up? It all comes from what’s called post-processing. Just like a color camera can combine color information from three detectors to make the image look true-to-life, astronomers can take three (or more!) images through different filters and combine them later to make a color picture. There are two main approaches to doing this, known colloquially as “true color” and “false color.”
A “true color” image of the surface of Jupiter’s moon Europa as seen by the Galileo spacecraft. Image credit: NASA/JPL-Caltech/SETI Institute
True color images strive to work just like your smartphone camera. The spacecraft captures images through filters which span the visible spectrum, so that, when combined, the result is similar to what you’d see with your own eyes. The recently released Galileo image of Europa is a gorgeous example of this.
Our eyes would never see the Crab Nebula as this Hubble image shows it. Image credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)
False color images aren’t limited by what our human eyes can see. They assign different colors to different features within an image. Take this famous image of the Crab Nebula, for instance. The red in the image traces oxygen atoms that have had electrons stripped away. Blue traces normal oxygen and green indicates sulfur. The result is a gorgeous image, but not one that we could ever hope to see for ourselves.
So, if we can make color images, why don’t we always? Again, the laws of physics step in to spoil the fun. For one, things in space are constantly moving, usually really, really quickly. Perhaps you saw the first color image of comet 67P/Churyumov-Gerasimenko released recently. It’s kind of blurry, isn’t it? That’s because both the Rosetta spacecraft and the comet moved in the time it took to capture the three separate images. When combined, they don’t line up perfectly and the image blurs. Not great!
The first color image of comet 67P/Churyumov-Gerasimenko. Image credit: ESA/Rosetta
But it’s the inverse-square law that is the ultimate challenge here. Radio waves, as a form of light, also rapidly become weaker with distance. When it takes 90 minutes to send back a single HiRISE image from the Mars Reconnaissance Orbiter, every shot counts and spending three on the same target doesn’t always make sense.
Finally, images, even color ones, are only one piece of the space exploration puzzle. Other observations, from measuring the velocity of dust grains to the composition of gases, are no less important to understanding the mysteries of nature. So, next time you see an eye-opening image, don’t mind that it’s in shades of gray. Just imagine everything else that lack of color is letting us learn.
The four dots around the bright source, an elliptical galaxy, are multiple images of the new supernova taken with the Hubble Space Telescope between November 10-20, 2014. In the bottom image, the galaxy has been digitally removed to show only the supernova. The line segments are diffraction spikes from a nearby star. Credit: P.L. Kelly et. all
How about four supernovae for the price of one? Using the Hubble Space Telescope, Dr. Patrick Kelly of the University of California-Berkeley along with the GLASS (Grism Lens Amplified Survey from Space) and Hubble Frontier Fields teams, discovered a remote supernova lensed into four copies of itself by the powerful gravity of a foreground galaxy cluster. Dubbed SN Refsdal, the object was discovered in the rich galaxy cluster MACS J1149.6+2223 five billion light years from Earth in the constellation Leo. It’s the first multiply-lensed supernova every discovered and one of nature’s most exotic mirages.
The lensed supernova was discovered far behind the rich galaxy cluster MACS J1149.6+2223. The cluster is one of the most massive known and gained notoriety in 2012 when astronomers harnessed its powerful lensing ability to uncover the most distant galaxy known at the time. Credit: NASA/ESA/M. Postman STScI/CLASH team
Gravitational lensing grew out of Einstein’s Theory of Relativitywherein he predicted massive objects would bend and warp the fabric of spacetime. The more massive the object, the more severe the bending. We can picture this by imagining a child standing on a trampoline, her weight pressing a dimple into the fabric. Replace the child with a 200-pound adult and the surface of the trampoline sags even more.
Massive objects like the Sun and even the planets warp the fabric of space. Here a planet orbits the Sun but doesn’t fall in because of its sideways orbital motion.
Similarly, the massive Sun creates a deep, but invisible dimple in the fabric of spacetime. The planets feel this ‘curvature of space’ and literally roll toward the Sun. Only their sideways motion or angular momentum keeps them from falling straight into the solar inferno.
Curved space created by massive objects also bends light rays. Einstein predicted that light from a star passing near the Sun or other massive object would follow this invisible curved spacescape and be deflected from an otherwise straight path. In effect, the object acts as a lens, bending and refocusing the light from the distant source into either a brighter image or multiple and distorted images. Also known as the deflection of starlight, nowadays we call it gravitational lensing.
This illustration shows how gravitational lensing works. The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of distant galaxies behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Credit: NASA, ESA, L. Calcada
Simulation of distorted spacetime around a massive galaxy cluster over time
Turns out there are lots of these gravitational lenses out there in the form of massive clusters of galaxies. They contain regular matter as well as vast quantities of the still-mysterious dark matter that makes up 96% of the material stuff in the universe. Rich galaxy clusters act like telescopes – their enormous mass and powerful gravity magnify and intensify the light of galaxies billions of light years beyond, making visible what would otherwise never be seen.
This cropped image shows the central slice of the MACS J1149 galaxy cluster. A massive elliptical galaxy lenses the light of SN Refsdal into four separate images. It also distorts the purplish spiral galaxy that’s host to the supernova. Credit: NASA/ESA/M. Postman STScI/CLASH team
Let’s return to SN Refsdal, named for Sjur Refsdal, a Norwegian astrophysicist who did early work in the field of gravitational lensing. A massive elliptical galaxy in the MACS J1149 cluster “lenses” the 9.4 billion light year distant supernova and its host spiral galaxy from background obscurity into the limelight. The elliptical’s powerful gravity’s having done a fine job of distorting spacetime to bring the supernova into view also distorts the shape of the host galaxy and splits the supernova into four separate, similarly bright images. To create such neat symmetry, SN Refsdal must be precisely aligned behind the galaxy’s center.
What looks like a galaxy with five nuclei really has just one (at center) surrounded by a mirage of four images of a distant quasar. The galaxy lies 400 million light years away; the quasar about 8 billion. Credit: NASA/ESA/Hubble
The scenario here bears a striking resemblance to Einstein’s Cross, a gravitationally lensed quasar, where the light of a remote quasar has been broken into four images arranged about the foreground lensing galaxy. The quasar images flicker or change in brightness over time as they’re microlensed by the passage of individual stars within the galaxy. Each star acts as a smaller lens within the main lens.
Color-composite image of the lensing elliptical galaxy and distorted background host spiral (top). The green circles, S1-4, show the locations of the supernova images, while another quadruply imaged segment of the spiral arm is marked in red. The bottom panels show two additional lensed images of the spiral host galaxy visible in the galaxy cluster field. Talk about a funhouse mirror! Credit: P.L. Kelly/GLASS/Hubble Frontier Fields
Detailed color images taken by the GLASS and Hubble Frontier Fields groups show the supernova’s host galaxy is also multiply-imaged by the galaxy cluster’s gravity. According to their recent paper, Kelly and team are still working to obtain spectra of the supernova to determine if it resulted from the uncontrolled burning and explosion of a white dwarf star (Type Ia) or the cataclysmic collapse and rebound of a supergiant star that ran out of fuel (Type II).
The time light takes to travel to the Earth from each of the lensed images is different because each follows a slightly different path around the center of the lensing galaxy. Some paths are shorter, some longer. By timing the brightness variations between the individual images the team hopes to provide constraints not only on the distribution of bright matter vs. dark matter in the lensing galaxy and in the cluster but use that information to determine the expansion rate of the universe.
Images captured by the Hubble Telescope of the vast debris systems surrounding nearby stars.
Credit: NASA/ESA/ G. Schneider (University of Arizona), and the HST/GO 12228 Team
Using NASA’s Hubble Space Telescope, astronomers have completed the largest and most sensitive visible-light imaging survey of the debris disks surrounding nearby stars. These dusty disks, likely created by collisions between leftover objects from planet formation, were imaged around stars as young as 10 million years old and as mature as more than 1 billion years old.
The research was conducted by astronomers from NASA’s Goddard Space Center with the help of the University of Arizona’s Steward Observatory. The survey was led by Glenn Schneider, the results of which appeared in the Oct. 1, 2014, issue of The Astronomical Journal.
“We find that the systems are not simply flat with uniform surfaces,” Schneider said. “These are actually pretty complicated three-dimensional debris systems, often with embedded smaller structures. Some of the substructures could be signposts of unseen planets.”
In addition to learning much about the debris fields that surround neighboring stars, the study presented an opportunity to learn more about the formation of our own Solar System.
“It’s like looking back in time to see the kinds of destructive events that once routinely happened in our solar system after the planets formed,” said Schneider.
Once thought to be flat disks, the study revealed an unexpected diversity and complexity of dusty debris structures surrounding the observed stars. This strongly suggest they are being gravitationally affected by unseen planets orbiting the star.
Alternatively, these effects could result from the stars’ passing through interstellar space. In addition, the researchers discovered that no two “disks” of material surrounding stars were alike.
A circumstellar disk of debris around a matured stellar system may indicate that Earth-like planets lie within. Credit: NASA/JPL
The astronomers used Hubble’s Space Telescope Imaging Spectrograph to study 10 previously discovered circumstellar debris systems, plus MP Mus, a mature protoplanetary disk that is comparable in age to the youngest of the debris disks.
Irregularities observed in one ring-like system in particular (around HD 181327) resemble the ejection of a huge spray of debris into the outer part of the system from the recent collision of two bodies.
“This spray of material is fairly distant from its host star — roughly twice the distance that Pluto is from the Sun,” said co-investigator Christopher Stark of NASA’s Goddard Space Flight Center, Greenbelt, Maryland. “Catastrophically destroying an object that massive at such a large distance is difficult to explain, and it should be very rare. If we are in fact seeing the recent aftermath of a massive collision, the unseen planetary system may be quite chaotic.”
Another interpretation for the irregularities is that the disk has been mysteriously warped by the star’s passage through interstellar space, directly interacting with unseen interstellar material. “Either way, the answer is exciting,” Schneider said. “Our team is currently analyzing follow-up observations that will help reveal the true cause of the irregularity.”
Over the past few years astronomers have found an incredible diversity in the architecture of exoplanetary systems. For instance, they have found that planets are arranged in orbits that are markedly different than found in our solar system.
A collision between two bodies is one explanation for the ring-like debris system around HD 181327. Credit: NASA/JPL-Caltech
“We are now seeing a similar diversity in the architecture of accompanying debris systems,” Schneider said. “How are the planets affecting the disks, and how are the disks affecting the planets? There is some sort of interdependence between a planet and the accompanying debris that might affect the evolution of these exoplanetary debris systems.”
From this small sample, the most important message to take away is one of diversity, Schneider said. He added that astronomers really need to understand the internal and external influences on these systems – such as stellar winds and interactions with clouds of interstellar material – and how they are influenced by the mass and age of the parent star, and the abundance of heavier elements needed to build planets.
Though astronomers have found nearly 4,000 exoplanet candidates since 1995, mostly by indirect detection methods, only about two dozen light-scattering, circumstellar debris systems have been imaged over that same time period.
That’s because the disks are typically 100,000 times fainter than (and often very close to) their bright parent stars. The majority have been seen because of Hubble’s ability to perform high-contrast imaging, in which the overwhelming light from the star is blocked to reveal the faint disk that surrounds the star.
The new imaging survey also yields insight into how our solar system formed and evolved 4.6 billion years ago. In particular, the suspected planet collision seen in the disk around HD 181327 may be similar to how the Earth-Moon system formed, as well as the Pluto-Charon system over 4 billion years ago. In those cases, collisions between planet-sized bodies cast debris that then coalesced into a companion moon.
