This image shows 22 out of 150 supernovae, only 10 percent of the Subaru Deep Field. With the exception of a few nearby Milky Way stars, each point of light in the image is a galaxy, which consists of tens of billions of stars.
updated 10/6/2011 11:38:58 AM ET 2011-10-06T15:38:58

Astronomers have peeled back layers of time to reveal a dozen of the most ancient star explosions ever seen.

These explosions, called supernovas, helped seed the universe with chemical elements, and scientists are able to use them as mile markers to measure the cosmos.

Researchers from Tel Aviv University pointed the huge Japanese Subaru Telescope in Hawaii at a patch of the sky as big as the full moon and let their cameras collect the accumulated light from several nights of observations. This allowed the scientists to image very faint objects from extremely far away, whose light has taken billions of years to reach Earth. Thus we are getting a picture of them as they were eons ago, when the light was first emitted.

In all, the scientists observed 150 supernovas in this bit of sky, 12 of which occurred around 10 billion years ago, meaning they exploded when the universe was only 3.7 billion years old, about one-third its present age of 13.7 billion years.

Violent cosmic deaths
Some supernovas are the violent deaths of massive stars. When these stars have burned up all their fuel, they finally succumb to the inward pull of gravity and collapse to become dense remnants such as neutron stars and black holes. In the process, they expel copious amounts of energy in a short and powerful explosion that's so bright we can see it across the universe.

Other supernovas occur when a special type of smaller star, called a white dwarf, slowly siphons off mass from a companion star, until it becomes too heavy and collapses in a similarly luminous detonation.

This kind of supernova, called Type 1a, always occurs when the star has reached a particular mass threshold, called the Chandrasekhar limit, and therefore Type 1a supernovas always release the same amount of radiation. By comparing their apparent brightness on the sky with the brightness they would have if an observer were right next to them, astronomers can measure their distances.

For this reason, Type 1a supernovas have become handy cosmic yardsticks that have helped astronomers realize that the expansion of the universe is accelerating, apparently due to a mysterious force called dark energy — a discovery that was awarded the 2011 Nobel Prize in physics.

The new research revealed that Type 1a supernovas were about five times more common during this ancient epoch, 10 billion years ago, than they are today.

Element factories
Supernovas are factories for heavy elements in the universe. Just after the Big Bang that started the cosmos, the universe was mostly made of hydrogen and helium, the two lightest elements. (They have one and two protons each, respectively.)

As stars formed and carried out nuclear fusion in their cores, elements such as carbon, nitrogen and oxygen were created. But to make anything heaver than iron, which has 26 protons per atom, would take a supernova. Only the extreme energies of these explosions are powerful enough to fuse these elements.

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Supernovas not only create these heavy elements but disperse them throughout space when they explode. Then the elements are caught up and made into new generations of stars, and eventually find their way into planets like Earth.

"These elements are the atoms that form the ground we stand on, our bodies, and the iron in the blood that flows through our veins," astronomer Dan Maoz, one of the leaders of the new study, said in a statement released Wednesday.

And without supernovas, none of this would be possible. By studying these ancient explosions, the scientists hope to learn more about the timeline of element creation in the universe.

The research was led by Tel Aviv University astrophysicists Maoz, Dovi Poznanski and Or Graur, and included scientists from the University of Tokyo, Kyoto University, the University of California Berkeley and Lawrence Berkeley National Laboratory.

The findings are reported this month in the Monthly Notices of the Royal Astronomical Society.

You can follow senior writer Clara Moskowitz on Twitter @ ClaraMoskowitz. Follow for the latest in space science and exploration news on Twitter @Spacedotcom  and on Facebook.

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Photos: Month in Space: January 2014

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  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
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