MessageToEagle.com - Our universe is filled with gobs of galaxies, bound together by gravity into
larger families called clusters. Lying at the heart of most clusters is a monster galaxy thought to grow in
size by merging with neighboring galaxies, a process astronomers call galactic cannibalism.
New research from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) is showing that,
contrary to previous theories, these gargantuan galaxies appear to slow their growth over time, feeding less and
less off neighboring galaxies.
"We’ve found that these massive galaxies may have started a diet in the last 5 billion years, and therefore have
not gained much weight lately," said Yen-Ting Lin of the Academia Sinica in Taipei, Taiwan, lead author of a study.
Click on image to enlarge
This image shows two of the galaxy clusters observed by NASA's Wide-field Infrared Survey Explorer (WISE) and Spitzer Space Telescope missions. Galaxy clusters are among the most massive structures in the universe. The central and largest galaxy in each grouping, called the brightest cluster galaxy or BCG, is seen at the center of each image.
The image on the left shows the cluster known as Abell 2199, which is relatively nearby at a distance of 400 million light-years from Earth (redshift of 0.0302). This image combines infrared data from WISE (in red) with shorter wavelengths of light extending into the visible spectrum from the Sloan Digital Sky Survey (in blue and green).
On the right is the cluster ISCS 1433.9+3330, which is significantly farther away at a distance of 4.4 billion light-years (redshift of 0.42). Infrared data from Spitzer (red) is combined with similar shorter wavelength data taken by the Mayall Telescope on Kitt Peak, Ariz.
Image credit: NASA/JPL-Caltech/SDSS/NOAO
Peter Eisenhardt, a co-author from NASA's Jet Propulsion Laboratory in Pasadena, Calif., said, "WISE and Spitzer
are letting us see that there is a lot we do understand -- but also a lot we don’t understand -- about the
mass of the most massive galaxies." Eisenhardt identified the sample of galaxy clusters studied by Spitzer, and
is the project scientist for WISE.
The new findings will help researchers understand how galaxy clusters -- among the most massive structures in
our universe -- form and evolve.
Galaxy clusters are made up of thousands of galaxies, gathered around their biggest member, what astronomers call
the brightest cluster galaxy, or BCG. BCGs can be up to dozens of times the mass of galaxies like our own Milky Way.
They plump up in size by cannibalizing other galaxies, as well as assimilating stars that are funneled into the
middle of a growing cluster.
To monitor how this process works, the astronomers surveyed nearly 300 galaxy clusters spanning 9 billion years of
The farthest cluster dates back to a time when the universe was 4.3 billion years old, and the closest,
when the universe was much older, 13 billion years old (our universe is presently 13.8 billion years old).
"You can't watch a galaxy grow, so we took a population census," said Lin. "Our new approach allows us to connect
the average properties of clusters we observe in the relatively recent past with ones we observe further back
in the history of the universe."
Spitzer and WISE are both infrared telescopes, but they have unique characteristics that complement each other
in studies like these. For instance, Spitzer can see more detail than WISE, which enables it to capture the
farthest clusters best. On the other hand, WISE, an infrared all-sky survey, is better at capturing images of
nearby clusters, thanks to its larger field of view. Spitzer is still up and observing; WISE went into hibernation
in 2011 after successfully scanning the sky twice.
The findings showed that BCG growth proceeded along rates predicted by theories until 5 billion years ago, or a
time when the universe was about 8 billion years old. After that time, it appears the galaxies, for the most part,
stopped munching on other galaxies around them.
The scientists are uncertain about the cause of BCGs' diminished appetites, but the results suggest current models
"BCGs are a bit like blue whales -- both are gigantic and very rare in number. Our census of the population of
BCGs is in a way similar to measuring how the whales gain their weight as they age. In our case, the whales
aren't gaining as much weight as we thought. Our theories aren't matching what we observed, leading us to
new questions," said Lin.
The Wandering Stars
In ancient civilizations, people pondered the meanings of the stars, watching for clues to their survival: the beginning of planting and
harvesting times, the seasons, and even portents of danger.
They soon noticed that certain stars didn't stay in place, but wandered amongst the fixed star field.
"The Most Profound Mystery In All Of Science" -
Little is known about this force and its its repulsive gravity, which is causing the expansion of the universe to accelerate.
The riddles of dark matter and cosmic inflation, along with dark energy, these are the three pillars of modern cosmological theory,"
and none of them can be explained with physics that we know," Michael Turner, director of the Kavli Institute for Cosmological Physics says.
Doesn't Secret Dark Matter Exist?
The more scientists study dark matter they know lesser and are not particularly optimistic about their results.
After completing this study, we know less about dark matter than we did before," said Matt Walker, of the Harvard-Smithsonian Center for Astrophysics.
A mysterious and still unknown substance is totally invisible in the Universe and reveals its presence only through its gravitational pull.
Mysteries Of A Dark Universe
Cosmology, the study of the universe as a whole, has been turned on its head by a stunning discovery that the universe is flying apart in all directions at an ever-increasing rate. Is the universe really as we think it should be? Or is nature somehow fooling us?
The astronomers whose data revealed this accelerating universe have been awarded the Nobel Prize for Physics.
Black Holes With No 'Table Manners' Eat Two Courses At Once!
It is still unknown how the supermassive black holes (SMBH) in galaxy centres accrete gas and grow.
Researchers from the University of Leicester (UK) and Monash University in Australia have investigated how some black holes got so big so fast that they are billions of times heavier than the sun.
Mercury Surprises Scientists
On March 17, MESSENGER (MErcury Surface, Space Environment, GEochemistry, and Ranging) completed its one-year primary mission, orbiting Mercury, capturing nearly 100,000 images, and recording data
that reveals new information about the planet's core, topography, and the mysterious radar bright material in the permanently shadowed areas near the poles.
Living Earth Simulator - Supercomputer Predicting The Future
In Douglas Adams book the Hitchhikers Guide to the Galaxy we encounter a machine called Deep Thought. It is the most powerful computer ever built. Deep Thought is capable of answering questions
concerning life, the Universe, and simply everything. Now scientists are planning to create a similar machine. It is called the Living Earth Simulator (LES).
Warp-Speed Planets Are Some Of The Fastest Objects In The Milky Way
Warped planets are some of the fastest objects in the Milky Way and they zoom through space near the speed of light.
Some years ago astronomers were astonished when they they found the first runaway star flying out of our Galaxy at a speed of 1.5 million miles per hour.
The discovery intrigued theorists, who wondered: If a star can get tossed outward at such an extreme velocity, could the same thing happen to planets?
Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the
course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view.
Kepler Will Find Goldilocks Planet Within The Next Two Years
NASA's Kepler spacecraft is discovering a veritable avalanche of alien worlds. Recent finds include planets with double suns, massive
"super-Earths" and "hot Jupiters," and a miniature solar system.
The variety of planets circling distant suns is as wonderful as it is surprising.