My heart stirs at these sights of Transcendence and Harmony,
The cosmic winds whisper an elegant Symphony,
I dance with the Stars, enshrouded in Magnificence
I let my soul free, to soak in this Blissfulness
— Leonidas Papadopoulos
Astronomers have revealed the first deep views from the Hubble Frontier Fields project during the recent 223rd meeting of the American Astronomical Society in Washington, D.C.
As previously reported here on AmericaSpace, Hubble Frontiers Fields is a collaborative project utilising all of NASA’s Great Observatories—the Hubble, Spitzer, and Chandra space telescopes—which aims to obtain the deepest-ever views of the distant Universe by utilising a technique called “gravitational lensing” while studying six specific galaxy clusters.
Gravitational lensing can be described as the phenomenon of the bending of light coming from distant, faraway cosmic sources, from the gravity of massive objects that lie in between. The gravity of these intermediate objects bends and refocuses the light of the more distant, background sources, acting like a lens, allowing us to observe distant parts of the Universe that would otherwise be beyond our view. Gravitational lensing, as an effect of the curvature of space-time by gravity, was first described by Einstein’s theory of General Relativity in the early 20th century and was later observed by astronomers in their studies of distant galaxies and galactic clusters.
The goal of the Hubble Frontier Fields project is to boost the viewing capabilities of NASA’s Great Observatories by taking advantage of this property of space-time. “The Frontier Fields is an experiment; can we use Hubble’s exquisite image quality and Einstein’s theory of General Relativity to search for the first galaxies?” says Dr. Matt Mountain, director of the Space Telescope Science Institute, which is responsible for the science operations of the Hubble and Kepler space telescopes, as well as the upcoming James Webb Space Telescope, due to launch in 2018. “With the other Great Observatories, we are undertaking an ambitious joint program to use galaxy clusters to explore the first billion years of the universe’s history.”
Video Credit: NASA/ESA and F. Summers, B. Lawton, M. Lussier, G. Bacon, and D. Coe (STScI)
The first galaxy cluster to be observed was Abell 2744, also known as the Pandora Cluster, located 3.5 billion light-years away at the southern constellation of Sculptor. It is one of the most massive galactic clusters ever observed and is believed to be the result of a series of previous collisions between four smaller clusters. Indeed, its estimated mass is approximately 400 trillion times that of the Sun—a staggering amount. Yet, the visible galaxies and gas seen in Abell 2744 account for only 25 percent of its total mass. The other 75 percent is believed to consist of dark matter—an invisible kind of matter that can only be observed indirectly by the effects of its gravity and is believed to make up 26.8 percent of the Universe’s total mass-energy.
The combined mass of the few hundreds of galaxies that comprise Abell 2744 has revealed the presence of approximately 3,000 more distant objects lying behind the cluster. The gravitational lensing effect of Abell 2744’s mass bent and refocused the light of these distant objects toward our line of sight, which would have otherwise remained invisible. This way, those galaxies appeared to Hubble 10 to 20 times larger and brighter than normal, seen as bright, long blue streaks and smudges around Abell 2744 in the Frontier Field images. Their warped, arc-shaped appearance is a consequence of this bending of light.
These first results from the Hubble Frontier Fields really validate the techniques of its observing campaign. Some of the distant galaxies discovered lying behind Abell 2744 are actually small dwarf galaxies, with the more distant located more than 12 billion light-years away. This means that with this technique, the Hubble Space Telescope could observe galaxies that are three times more distant than Abell 2744 itself, looking back at a time when the Universe was less than 2 billion years old!
In addition to being able to look further back in time using gravitational lensing, the Hubble telescope was able to observe the interior of Abell 2744 in a resolution that was unobtainable to previous studies of the cluster. In fact, Abell 2744 is revealed in such detail in these images that astronomers were able to detect previously unobserved small, dwarf galaxies inside the cluster, with masses as low as 1/1000th that of our own galaxy. Moreover, Hubble was even able to discern the faint light of individual rogue stars inside the cluster that have been stripped away from their galaxies of origin through gravitational interactions!
These first results help to meet some of the additional goals of the Hubble Frontier Fields project as well: probing the presence of dark matter inside Abell 2744. With the ability to obtain such crisp, deep-view images of the cluster’s interior, astronomers could possibly gain a better understanding of the nature of this ever-elusive mystery of astrophysics. “The Frontier Fields is combining the power of nature’s telescopes — these massive clusters of galaxies — with Hubble, to provide the intrinsically deepest yet view of the universe,” said Jennifer M. Lotz, assistant astronomer at the Space Telescope Science Institute, during the recent AAS meeting.
During the three-year duration of the Frontier Fields program, Hubble will observe six massive galaxy clusters in total. As was the case with the Abell 2744 observations, it will use its Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) instruments in parallel, one focused at the galaxy cluster itself, and the other pointed six arc minutes away from it. After six months, following the Earth’s orbit around the Sun, Hubble will be at the opposite side of the sky and the instruments will “swap” targets, producing a more comprehensive and detailed set of observations for the same object in various wavelengths. The first set of pictures of Abell 2744 were obtained during observing sessions that were conducted in November 2013, totaling 67 hours. Hubble will observe Abell 2744 again the following May. In the meantime, Hubble will start observing next week the second galaxy cluster on the Frontier Fields list, the MACSJ 0416.1-240.
“It’s a fabulous demonstration of the synergy between Hubble and Spitzer,” says Pascal Oesch, astronomer with Yale University in New Haven, Conn.
“The Space Age has transformed technology, and our view of our planet and ourselves. For the last half-century, NASA has been at the forefront of the scientific exploration of the cosmos. Let’s keep it there,” remarks Mountain.
Indeed, the recent results coming from the Hubble Frontier Fields program are a testament to the pioneering spirit and the leadership role that have been the hallmark of NASA throughout the agency’s celebrated history of exploration of the Cosmos.