A so-called "cosmic tsunami" is rousing a galaxy cluster affectionately nicknamed "Sausage," suggesting that stagnant galaxies can be rejuvenated when galactic clusters collide, scientists say.
Astronomers made the discovery while studying CIZA J2242.8+5301, an ancient galaxy cluster 2.3 billion light-years from Earth. The cluster (yes, they actually call it Sausage), which is full of old red stars, is waking up as a shock wave triggers new star formation. The shock wave from the cluster's collision, which scientists compared to a tsunami, began 1 billion years ago and is moving at a mind-boggling speed: 5.6 million mph (9 million km/h).
"We assumed that the galaxies would be on the sidelines for this act, but it turns out they have a leading role," study co-leader Andra Stroe, an astronomer at Leiden Observatory, said in a statement. "The comatose galaxies in the Sausage cluster are coming back to life, with stars forming at a tremendous rate. When we first saw this in the data, we simply couldn't believe what it was telling us." [Epic Photos: When Galaxies Collide]
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This is the first time such star formation has been observed, but in theory nearly every galaxy cluster should have passed through this period of furious star formation. Alas, such a resurrection is not meant to last, the researchers said.
"But star formation at this rate leads to a lot of massive, short-lived stars coming into being, which explode as supernovae a few million years later," the study's other co-leader, David Sobral of Leiden and the University of Lisbon, said in a statement. "The explosions drive huge amounts of gas out of the galaxies and with most of the rest consumed in star formation, the galaxies soon run out of fuel. If you wait long enough, the cluster mergers make the galaxies even more red and dead - they slip back into a coma and have little prospect of a second resurrection."
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Stroe, Sobal and an international team of astronomers used several telescopes and observatories in La Palma, Spain, and in Hawaii to study the Sausage galaxy cluster, which is located in the constellation Lacerta (the Lizard) in the Northern Hemisphere sky. Their research was detailed in the April 24 edition of the Monthly Notices of the Royal Astronomical Society.
The team plans to sample a larger number of galaxies soon to try to catch more of these comatose mergers in the act.
Originally published on Space.com.
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This radio image shows a shock wave (the bright arc running from bottom left to top right) in the 'Sausage' merging cluster of galaxies as seen by the Giant Metrewave Radio Telescope.
Astronomers using the Hubble Space Telescope recently completed the largest and most sensitive survey of dust surrounding young star systems. The survey zoomed-in on stars that are between 10 million to 1 billion years old and the source of the dust is thought to be the left-over debris from planet, asteroid and comet collisions after systems of planets have formed.
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The research is akin to looking far back into the history of our solar system, seeing the inevitable dusty mess left over after the Earth and other planets evolved. "It's like looking back in time to see the kinds of destructive events that once routinely happened in our solar system after the planets formed," said Glenn Schneider, of the University of Arizona's Steward Observatory and lead scientist on the survey team.
Read on to see some of the beautiful variety of circumstellar disks observed by Hubble.
One of the major findings to come from this survey is the stunning diversity of dust surrounding these young stars. Traditionally, circumstellar dust is thought to settle into an orderly disk-like shape -- but it turns out that the opposite is true.
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"We find that the systems are not simply flat with uniform surfaces," said Schneider. "These are actually pretty complicated three-dimensional debris systems, often with embedded smaller structures. Some of the substructures could be signposts of unseen planets."
One stunning observation of the star HD 181327 exhibits a bright ring of dust containing irregularities, potential evidence of a massive collision that has scattered debris far and wide. "This spray of material is fairly distant from its host star — roughly twice the distance that Pluto is from the Sun," said Christopher Stark of NASA's Goddard Space Flight Center, Greenbelt, Md., and co-investigator in the survey team. "Catastrophically destroying an object that massive at such a large distance is difficult to explain, and it should be very rare. If we are in fact seeing the recent aftermath of a massive collision, the unseen planetary system may be quite chaotic."
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Another interpretation for the irregularities could be some kind of interaction with unseen interstellar material. "Our team is currently analyzing follow-up observations that will help reveal the true cause of the irregularity," added Schneider.
Like the diversity of exoplanetary systems astronomers have discovered, it appears the accompanying dust disks also share this characteristic, possibly indicative of gravitational interactions with planets orbiting the stars surveyed by Hubble.
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"How are the planets affecting the disks, and how are the disks affecting the planets? There is some sort of interdependence between a planet and the accompanying debris that might affect the evolution of these exoplanetary debris systems," said Schneider.
Since 1995, thousands of exoplanets have been discovered orbiting stars in our galaxy. Over the same period, however, only a couple of dozen circumstellar disks have been imaged directly. This is down to the fact that the scattered light off these disks is extremely faint (around 100,000 times fainter than the parent star's light). The technology and techniques are only recently becoming available for scientists to not only block the star's blinding light, but to also boost the sensitivity of observations to pick out this scattered light that would otherwise be obscured from view. Fortunately, Hubble's high-contrast imaging has been key in making this survey a success.
By studying these disks of dust and their surprising variety of morphologies may help astronomers better understand how the Earth-moon and Pluto-Charon systems formed. Through planetary collisions, the debris from the early solar system may have coalesced to create many of the natural satellites we see today, 4.6 billion years later. The results of this survey have been published in The Astrophysical Journal.