Image: Phoenix Cluster
M. Weiss / CXC / NASA
The hot gas in the Phoenix Cluster is giving off copious amounts of X-rays and cooling quickly over time, especially near the center of the cluster, causing gas to flow inwards and form huge numbers of stars at the base of the flows. These features are shown in this artist's impression of the central galaxy, with hot gas shown in red, cooler gas shown in blue, the gas flows shown by the ribbonlike features, and the newly formed stars shown in blue in the outer part of the galaxy.
updated 8/15/2012 1:38:50 PM ET 2012-08-15T17:38:50

An extraordinary cluster of faraway galaxies is shattering or challenging a number of cosmic records, weighing in as potentially the most massive cluster known.

The colossal galaxy cluster is also the brightest in X-ray light, and the galaxy at its heart apparently gives birth to more than 700 stars per year — hundreds of times as fast as our Milky Way forms stars, researchers say.

  1. Space news from
    1. KARE
      Teen's space mission fueled by social media

      Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

    2. Buzz Aldrin's vision for journey to Mars
    3. Giant black hole may be cooking up meals
    4. Watch a 'ring of fire' solar eclipse online

The cluster of galaxies, located about 7 billion light-years away, is formally known by the alphabet-soup name of SPT-CLJ2344-4243. Astronomers also have given it a more informal moniker: the Phoenix Cluster, named after the constellation in which it resides. It appears to contain thousands of galaxies with a range of sizes, from dwarf galaxies to conglomerations of stars about the size of the Milky Way.

Scientists added that this record-breaking galaxy cluster may help solve a decades-old puzzle about how slowly such clusters cool. [7 Surprising Things About the Universe]

Most massive ever?
The Phoenix Cluster is extraordinarily massive: about 2,000 times the apparent mass of the Milky Way, or 2.5 quadrillion times the mass of the sun.

"I would say it's in a dead heat for the most massive galaxy cluster," study lead author Michael McDonald, an astronomer at the Massachusetts Institute of Technology, told "The record holder, 'El Gordo,' is slightly more massive, but the uncertainty in this estimate is high — it could turn out that with more careful measurements, Phoenix is more massive."

The Phoenix Cluster was initially discovered in 2010 by the South Pole Telescope. "We didn't realize how exciting it was until summer of 2011, when we obtained follow-up X-ray data from the Chandra X-ray Observatory," McDonald said. "These observations immediately revealed the extreme X-ray brightness of this galaxy cluster."

Indeed, the Phoenix Cluster is the most X-ray luminous galaxy cluster found yet, about 35 percent brighter than the previous record holder. All the X-rays it sheds suggest the Phoenix Cluster is also the fastest-cooling cluster yet known, since cooling of hot gas in the cluster is what is thought to produce the X-rays.

"My first thought was that if there's that much cooling going on, there should be stars forming," McDonald said. As such, using the Gemini telescope, "we found evidence for a tremendous amount of star formation."

Star formation
Researchers say the central galaxy in the Phoenix cluster is apparently forming a whopping 740 stars per year, based on images acquired from 10 different telescopes in space and on the ground around the world that observed the cluster at a variety of wavelengths. The previous record holder was Abell 1835, a galaxy that forms about 100 stars per year.

"If you look at normal galaxy clusters, the central, most massive galaxy is typically forming stars at a rate of one new star every few years," McDonald said. "It's a huge difference."

Image: Phoenix Cluster
M. McDonald / NASA / CXC / MIT / JPL-Caltech / AURA / NOAO / CTIO
A composite image of the Phoenix Cluster shows X-ray data from NASA's Chandra X-ray Observatory in purple, an ultraviolet image from NASA's Galaxy Evolution Explorer in blue and an optical image from the 4-meter Blanco telescope in red, green and blue.

The central massive galaxies are essentially the first to form within such clusters.  Being billions of years old, they are expected to have been dormant a very long time. That makes this "starburst" activity seen in the Phoenix cluster's central galaxy even more extraordinary.

"Central galaxies have typically been referred to as 'red and dead' — just a bunch of old stars orbiting a massive black hole, and there's nothing new happening," McDonald said. "But the central galaxy in this cluster has somehow come to life and is giving birth to prodigious numbers of new stars."

This colossal rate of star formation may shed new light on a decades-old conundrum regarding the evolution of galaxy clusters. Gas at the core of a cluster streaming from nearby galaxies and supernova explosions should naturally cool over time, forming a flow cold enough to condense and form new stars. However, scientists have long been at a loss to find any galaxy cluster that actually cools at the rates predicted.

The cooling problem
One explanation for this "cooling flow problem" may be that a cluster's natural cooling somehow gets interrupted. For instance, the supermassive black holes suspected to lurk at the centers of many of these clusters might emit jets of particles that reheat the core, preventing it from cooling entirely.

"What's interesting about the Phoenix Cluster is that we see such a large fraction of the cooling that was predicted," McDonald said. "It could be that this is earlier in the evolution where there's nothing stopping it, so it cools and becomes a starburst."

In the future, "ideally we'd like to find more systems like this," McDonald said. "It's really difficult to draw meaningful conclusions based on a single system.

"If we could find more systems like this one, it would imply that this is a normal phase of galaxy cluster evolution," he added. "To do this, we need deeper surveys that cover larger areas of the sky. We have the technology in place for this — we just need time and continued financial support."

On the other hand, the Phoenix cluster may prove unique. If so, "we hope to get more detailed observations to answer questions such as, 'Why isn't the central black hole regulating this extreme cooling and the resulting star formation?' and, 'Is the starburst really being fueled by the cooling gas in the cluster core, or is it the result of something more exotic, like galaxy-galaxy mergers?'" McDonald said.

The team's findings are detailed in Thursday's issue of the journal Nature.

Follow on Twitter @Spacedotcom. We're also on Facebook and Google+.

© 2013 All rights reserved. More from

Photos: Month in Space: January 2014

loading photos...
  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
  1. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  2. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  3. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  4. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.


Discussion comments


Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments