This is the season of celebrating, and the Chandra X-ray Center has prepared a platter of cosmic treats from NASA's Chandra X-ray Observatory to enjoy. This selection represents different types of objects — ranging from relatively nearby exploded stars
Before electrical power became available, water fountains worked by relying on gravity to channel water from a higher elevation to a lower one. This water could then be redirected to shoot out of the fountain and create a centerpiece for people to admire.
In space, awesome gaseous fountains have been discovered in the centers of galaxy clusters. One such fountain is in the cluster Abell 2597. There, vast amounts of gas fall toward a supermassive black hole, where a combination of gravitational and electromagnetic forces sprays most of the gas away from the black hole in an ongoing cycle lasting tens of millions of years.
Scientists used data from the Atacama Large Millimeter/submillimeter Array (ALMA), the Multi-Unit Spectroscopic Explorer (MUSE) on ESO's Very Large Telescope (VLT) and NASA's Chandra X-ray Observatory to find the first clear evidence for the simultaneous inward and outward flow of gas being driven by a supermassive black hole.
Hidden in a distant galaxy cluster collision are wisps of gas resembling the starship Enterprise — an iconic spaceship from the "Star Trek" franchise.
Galaxy clusters — cosmic structures containing hundreds or even thousands of galaxies — are the largest objects in the Universe held together by gravity. Multi-million-degree gas fills the space in between the individual galaxies. The mass of the hot gas is about six times greater than that of all the galaxies combined. This superheated gas is invisible to optical telescopes, but shines brightly in X-rays, so an X-ray telescope like NASA's Chandra X-ray Observatory is required to study it.
Astronomers have used data from NASA's Chandra X-ray Observatory to capture a dramatic image of an enormous tail of hot gas stretching for more than a million light years behind a group of galaxies that is falling into the depths of an even-larger cluster of galaxies. Discoveries like this help astronomers learn about the environment and conditions under which the Universe's biggest structures evolve.
Galaxy clusters are the largest structures in the Universe held together by gravity. While galaxy clusters can contain hundreds or even thousands of individual galaxies, the lion's share of mass in a galaxy cluster comes from hot gas, which gives off X-rays, and unseen dark matter. How did these cosmic giants get to be so big?
We welcome Stephen A. Walker, first author on our latest results from the Perseus galaxy cluster, as our guest blogger. Originally from the UK, Stephen received his PhD at the University of Cambridge, continuing there as a postdoc, before becoming a NASA Postdoctoral Program Fellow at NASA’s Goddard Space Flight Center.
The story begins in October 2010, when I started my PhD at the University of Cambridge. I was exploring new X-ray observations of the outskirts of galaxy clusters taken with Suzaku. Much like in a city, the outskirts are where clusters continue to grow outwards.
Galaxy clusters are the largest gravitationally bound structures of the universe, consisting of hundreds or thousands of galaxies. The total masses of clusters are colossal, reaching up to and beyond a million billion times the mass of the sun. The vast majority of the ‘normal’ matter in these clusters (like hydrogen and helium) does not actually lie in the galaxies themselves, but rather in an extremely hot and diffuse gas between the galaxies, called the intracluster medium.
As the largest gravitationally bound structures in the universe, galaxy clusters continue to grow and accrete matter from the surrounding cosmic web of gas produced by the Big Bang. When the infalling gas falls into their deep gravitational potential wells, it is shock heated to tens of millions of degrees, and begins to emit prodigiously in the X-ray band.
A gigantic and resilient "cold front" hurtling through the Perseus galaxy cluster
This graphic shows the cold front in the Perseus cluster. The image above contains X-ray data from Chandra — for regions close to the center of the cluster —along with data from ESA's XMM-Newton and the now-defunct German Roentgen (ROSAT) satellite for regions farther out. The Chandra data have been specially processed to brighten the contrast of edges to make subtle details more obvious.
An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter, as described in our latest press release. The finding involves a new explanation for a set of results made with NASA's Chandra X-ray Observatory, ESA's XMM-Newton and Hitomi, a Japanese-led X-ray telescope. If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the Universe.
Astronomers have used data from NASA's Chandra X-ray Observatory to study the properties of dark matter, the mysterious, invisible substance that makes up a majority of matter in the universe. The study, which involves 13 galaxy clusters, explores the possibility that dark matter may be more "fuzzy" than "cold," perhaps even adding to the complexity surrounding this cosmic conundrum.
For several decades, astronomers have known about dark matter. Although it cannot be observed directly, dark matter does interact via gravity with normal, radiating matter (that is, anything made up of protons, neutrons, and electrons bundled into atoms). Capitalizing on this interaction, astronomers have studied the effects of dark matter using a variety of techniques, including observations of the motion of stars in galaxies, the motion of galaxies in galaxy clusters, and the distribution of X-ray emitting hot gas in galaxy clusters. Dark matter has also left an imprint on the radiation left over from the Big Bang 13.8 billion years ago.
For this guest blog post, we are lucky to have not one, but two, contributors. Reinout van Weeren obtained his PhD from Leiden University, The Netherlands, before moving to the Harvard-Smithsonian Center of Astrophysics as an Einstein Postdoctoral Research Fellow. He is currently a Clay Fellow at the same place. He works on merging galaxy clusters, focusing on combined radio and X-ray observations. Felipe Andrade-Santos obtained his PhD from the Universidade de São Paulo, Brazil, before becoming a postdoctoral research fellow at the Harvard-Smithsonian Center of Astrophysics. He works on X-ray observations of galaxy clusters and galaxy cluster samples. Reinout and Felipe recently presented their study on the merging galaxy cluster system Abell 3411 and 3412 at the 229th meeting of the American Astronomical Society meeting in January 2017.
Galaxy clusters are the most massive objects in the Universe bound together by gravity and contain up to a few thousand galaxies. They are also permeated by very thin 100-million-degree gas that is held together by the cluster's strong gravitational pull. This hot gas can be imaged with X-ray satellites such as NASA's Chandra X-ray Observatory. Galaxy clusters form by mergers of smaller clusters and galaxy groups. During a merger event, which typically lasts for about a billion years, the galaxies mostly fly past each other without strongly interacting. In contrast, the diffuse gas in the merging clusters collides, creating giant shock waves, which are cosmic versions of sonic booms generated by supersonic aircraft. Cluster mergers have been of great interest to astronomers and us because of the extreme physical processes that take place during such events.
Radio telescopes have shown that large regions of merging galaxy clusters glow at radio wavelengths. The radio emission is produced by tiny particles, called electrons, which spiral around magnetic field lines and have energies that are a million times higher than the particles making up the hot cluster gas. Astronomers have long been puzzled by how these energetic electrons are produced. One idea is that the energetic particles are accelerated to these extreme energies by shocks created when clusters collide and merge.
We are pleased to welcome Dr. Tao Wang as a guest blogger. Tao is the first author of a paper that is the subject of our latest press release, about an extremely distant galaxy cluster. Tao is now a postdoc in CEA/Saclay, France, working with Dr. David Elbaz on high-redshift galaxies and galaxy clusters, and received a PhD in astrophysics from Nanjing University, China in 2012. During his PhD, he worked for two years in the Harvard-Smithsonian Center for Astrophysics and then worked as an associate researcher back in Nanjing University for one year before starting his postdoctoral work at CEA/Saclay in 2013.
Galaxy clusters are the largest known gravitationally bound structures in the universe and usually consist of hundreds of galaxies distributed in a relatively small area a few million light-years across. One of the most prominent features of clusters is the presence of a predominant population of massive, elliptical galaxies in the cluster core. These galaxies are among the most massive galaxies in the universe and are believed to have rapidly formed their stars a long time ago. However, how these galaxies formed and why have they stopped forming new stars remain mysteries. Solving these mysteries is essential to our understanding of both galaxy and cluster formation. To answer these questions, the key is to search for and study galaxy clusters (or their progenitors) in the early universe, right when they form.
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