Category: galaxy

VV 340, pair of interacting galaxies in Boöt…

VV 340, pair of interacting galaxies in Boötes.

The two galaxies shown here are in the early stage of an interaction that will eventually lead to them merging in millions of years.


NASA/STScI/NRAO/A.Evans et al


Abell 2744: Pandora’s Cluster of Galax…

Abell 2744: Pandora’s Cluster of Galaxies 

Image Credit: NASA, ESA, J. Merten (ITA, AOB), & D. Coe (STScI)

NGC 1309: Spiral Galaxy and Friends Image Cr…

NGC 1309: Spiral Galaxy and Friends 

Image Credit: Hubble Legacy Archive, ESA, NASA; Processing – Jeff Signorelli

Galaxy M74 (via apod)

Galaxy M74 (via apod)

The spiral galaxy NGC253 in the constellation …

The spiral galaxy NGC253 in the constellation Sculptor.

Image credit: Eddie Trimarchi

A galaxy cluster, or cluster of galaxies, is…

A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity. They are the largest known gravitationally bound structures in the universe and were believed to be the largest known structures in the universe until the 1980s, when superclusters were discovered. One of the key features of clusters is the intracluster medium (ICM). The ICM consists of heated gas between the galaxies and has a peak temperature between 2–15 keV that is dependent on the total mass of the cluster. Galaxy clusters should not be confused with star clusters, such as open clusters, which are structures of stars within galaxies, or with globular clusters, which typically orbit galaxies. Small aggregates of galaxies are referred to as galaxy group rather than clusters of galaxies. The galaxy groups and clusters can themselves cluster together to form superclusters. source

Spiral galaxy ESO 137-001 hurtles through ma…

Spiral galaxy ESO 137-001 hurtles through massive galaxy cluster Abell 3627 some 220 million light years away. The distant galaxy is seen in this colorful Hubble/Chandra composite image through a foreground of the Milky Way’s stars toward the southern constellation Triangulum Australe. As the spiral speeds along at nearly 7 million kilometers per hour, its gas and dust are stripped away when ram pressure with the cluster’s own hot, tenuous intracluster medium overcomes the galaxy’s gravity. Evident in Hubble’s near visible light data, bright star clusters have formed in the stripped material along the short, trailing blue streaks. Chandra’s X-ray data shows off the enormous extent of the heated, stripped gas as diffuse, darker blue trails stretching over 400,000 light-years toward the bottom right. The significant loss of dust and gas will make new star formation difficult for this galaxy. A yellowish elliptical galaxy, lacking in star forming dust and gas, is just to the right of ESO 137-001 in the frame.

Image Credit: NASA, ESA, CXC

Astronomers have just assembled one of the m…

Astronomers have just assembled one of the most comprehensive portraits yet of the universe’s evolutionary history, based on a broad spectrum of observations by the Hubble Space Telescope and other space and ground-based telescopes. In particular, Hubble’s ultraviolet vision opens a new window on the evolving universe, tracking the birth of stars over the last 11 billion years back to the cosmos’ busiest star-forming period, about 3 billion years after the big bang. This photo encompasses a sea of approximately 15,000 galaxies — 12,000 of which are star-forming — widely distributed in time and space. This mosaic is 14 times the area of the Hubble Ultra Violet Ultra Deep Field released in 2014.

Credits: NASA, ESA, P. Oesch (University of Geneva), and M. Montes (University of New South Wales)

Relativistic Jets Super-massive black hol…

Relativistic Jets

Super-massive black holes in the centers of some active galaxies create powerful jets of radiation and particles travelling close to the speed of light. Attracted by strong gravity, matter  falls towards the central black hole as it feeds on the surrounding gas and dust. But instead of falling into the black hole, a small fraction of particles get accelerated to speed almost as great as the speed of light and spewn out in two narrow beams along the axis of rotation of the black hole. These jets are believed to be the sources of the fastest-travelling particles in the Universe – cosmic rays.

In some cases these jets can reach outside of the galaxy itself, ending in giant radio lobes far from the active galaxy center. Observed with radio telescopes these galaxies can have a variety of shapes, mostly resembling dumbbells. We call these objects either radio galaxies or quasars, depending on how bright they are and how fast they consume the surrounding matter. As these monster black holes grow to become a billion times more massive than our Sun, their jets eventually get strong enough to blow gas out of the galaxy and shut off the formation of new stars! 

A small fraction of active galaxies with jets are oriented so that their jet is pointed straight at Earth. In those cases we observe radiation across the electromagnetic spectrum enhanced by the enormous speed of the jet and call such sources blazars. By combining NuSTAR X-ray observations with observations in the radio, visible light and extremely energetic gamma-rays, we are learning about the physics of how powerful jets are formed and sustained. One of the remaining mysteries is how do jets create radiation of such extraordinary broad spectrum up to very high energies.


This composite image shows the distribution …

This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters.

Image Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)