In an ambitious effort to look further out into the universe than anybody has ever seen before, NASA will be combining the efforts of its three flagship space telescopes (The Hubble Space Telescope, the Chandra X-ray observatory and the infrared Spitzer Space Telescope) in a new program called Frontier Fields. Together they will use the gravitational fields of distant galaxy clusters to magnify the light from distant objects that would normally be a hundred times too faint to be seen by any of these telescopes individually.Over the course of three years, NASA will direct the Hubble, Chandra and Spitzer space telescopes to carefully study 6 distant galaxy clusters. The Frontier Fields scientists are not interested in the clusters themselves, but are instead using their enormous gravity fields as a natural lens to boost and magnify images from galaxies far further away. Galaxy clusters are some of the most massive structures in the universe, containing hundreds or thousands of galaxies, each of which contain hundreds of billions of stars. As Einstein first predicted in the beginning of the 20th Century, gravity affects photons so that if a beam of light passes a very massive object, that light bends and the image it creates becomes distorted, as if passing through a crude lens. By using this effect, astronomers can use the chance alignment of extremely distant galaxies with relatively nearby clusters to boost and record their light and thus discover galaxies tens of billions of light years away.
“The idea is to use nature’s natural telescopes in combination with the Great Observatories to look much deeper than before and find the most distant and faint galaxies we can possibly see,” said principal investigator Jennifer Lotz of the Space Telescope Science Institute (STScI) in Baltimore, Md.
Since the Universe is only 13.8 billion years old, such distant galaxies will be very young, having been formed when the universe was only a few hundred million years old. Studying such distant galaxies will provide important data that will allow scientists to either confirm current models of the formation of the early universe, or disprove them. Astronomers have already been making observations like this for years, but this is the first large-scale program to combine the power of NASA’s flagship space telescopes. Unlike radio telescope interferometry, though, the telescopes won’t be linked as a single instrument. Rather, each will scrutinise the specific regions of the electromagnetic spectrum that it is optimised for, and the data they collect will be combined to gain a complete picture of what they’re looking at.
“We want to understand when and how the first stars and galaxies formed in the universe, and each Great Observatory gives us a different piece of the puzzle. 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,” said Peter Capak, the Spitzer principal investigator of the Frontier Fields program.
Chandra’s role is a little more subtle. A secondary goal of the project is to map out the distribution of dark matter within the galaxy clusters. Dark matter is the mysterious ghostly substance that does not reflect or shine light, and does not interact with regular matter, but which nevertheless has gravity and makes up the bulk of the mass of galaxies. By studying where the lensed images of the distant young galaxies appear, and the way in which they are distorted, astronomers will be able to determine where the gravity field of the cluster is strongest. Chandra’s observations in the X-ray band will identify powerful gravity sources that are made from regular matter, such as black holes and pulsars, so that their influence can be subtracted from the gravitation lensing and allow for a more accurate mapping of dark matter.
Observations have already started: In October last year, the three space telescopes of Frontier Fields were pointed at the galactic cluster Abell 2744 (“Pandora’s Cluster”), which appears to be a supercluster resulting from an earlier collision of at least four distinct earlier galaxy clusters. The cluster is so large that the collision which formed it lasted over 350 million years. Hubble and Spitzer have already studied this cluster before, although this is the first time they’ll be looking so deeply, and with the help of Chandra.