FARTHEST SUPEROVA SO FAR DISCOVERED

FROM: NASA
Hubble Breaks Record in Search for Farthest Supernova

WASHINGTON -- NASA's Hubble Space Telescope has found the farthest supernova so far of the type used to measure cosmic distances. Supernova UDS10Wil, nicknamed SN Wilson after American President Woodrow Wilson, exploded more than 10 billion years ago.

SN Wilson belongs to a special class called Type Ia supernovae. These bright beacons are prized by astronomers because they provide a consistent level of brightness that can be used to measure the expansion of space. They also yield clues to the nature of dark energy, the mysterious force accelerating the rate of expansion.

"This new distance record holder opens a window into the early universe, offering important new insights into how these stars explode," said David O. Jones of Johns Hopkins University in Baltimore, Md., an astronomer and lead author on the paper detailing the discovery. "We can test theories about how reliable these detonations are for understanding the evolution of the universe and its expansion."

The discovery was part of a three-year Hubble program, begun in 2010, to survey faraway Type Ia supernovae and determine whether they have changed during the 13.8 billion years since the explosive birth of the universe. Astronomers took advantage of the sharpness and versatility of Hubble's Wide Field Camera 3 to search for supernovae in near-infrared light and verify their distance with spectroscopy.
Leading the work is Adam Riess of the Space Telescope Science Institute in Baltimore, Md., and Johns Hopkins University.

Finding remote supernovae provides a powerful method to measure the universe's accelerating expansion. So far, Riess's team has uncovered more than 100 supernovae of all types and distances, looking back in time from 2.4 billion years to more than 10 billion years. Of those new discoveries, the team has identified eight Type Ia supernovae, including SN Wilson, that exploded more than 9 billion years ago.

"The Type Ia supernovae give us the most precise yardstick ever built, but we're not quite sure if it always measures exactly a yard," said team member Steve Rodney of Johns Hopkins University. "The more we understand these supernovae, the more precise our cosmic yardstick will become."

Although SN Wilson is only 4 percent more distant than the previous record holder, it pushes roughly 350 million years farther back in time. A separate team led by David Rubin of the U.S. Energy Department's Lawrence Berkeley National Laboratory in California announced the previous record just three months ago.

Astronomers still have much to learn about the nature of dark energy and how Type Ia supernovae explode.
By finding Type Ia supernovae so early in the universe, astronomers can distinguish between two competing explosion models. In one model the explosion is caused by a merger between two white dwarfs. In another model, a white dwarf gradually feeds off its partner, a normal star, and explodes when it accretes too much mass.

The team's preliminary evidence shows a sharp decline in the rate of Type Ia supernova blasts between roughly 7.5 billion years ago and more than 10 billion years ago. The steep drop-off favors the merger of two white dwarfs because it predicts that most stars in the early universe are too young to become Type Ia supernovae.

"If supernovae were popcorn, the question is how long before they start popping?" Riess said. "You may have different theories about what is going on in the kernel. If you see when the first kernels popped and how often they popped, it tells you something important about the process of popping corn."

Knowing the type of trigger for Type Ia supernovae also will show how quickly the universe enriched itself with heavier elements such as iron. These exploding stars produce about half of the iron in the universe, the raw material for building planets, and life.

The team's results have been accepted for publication in an upcoming issue of The Astrophysical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. The Association of Universities for Research in Astronomy Inc., in Washington operates STScI.

THE DEAD STAR

FROM: NASA
Sizzling Remains of a Dead Star
This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. Blue indicates the highest energy X-ray light, where NuSTAR has made the first resolved image ever of this source. Red and green show the lower end of NuSTAR's energy range, which overlaps with NASA's high-resolution Chandra X-ray Observatory.

Light from the stellar explosion that created Cassiopeia A is thought to have reached Earth about 300 years ago, after traveling 11,000 years to get here. While the star is long dead, its remains are still bursting with action. The outer blue ring is where the shock wave from the supernova blast is slamming into surrounding material, whipping particles up to within a fraction of a percent of the speed of light. NuSTAR observations should help solve the riddle of how these particles are accelerated to such high energies

X-ray light with energies between 10 and 20 kiloelectron volts are blue; X-rays of 8 to 10 kiloelectron volts are green; and X-rays of 4.5 to 5.5 kiloelectron volts are red.

The starry background picture is from the Digitized Sky Survey.


Image credit: NASA/JPL-Caltech/DSS

 

SHOCK-WAVE

FROM:  NASA
Using observations from NASA's Chandra X-ray Observatory, researchers have obtained the first X-ray evidence of a supernova shock wave breaking through a cocoon of gas surrounding the star that exploded. This discovery may help astronomers understand why some supernovas are much more powerful than others. On Nov. 3, 2010, a supernova was discovered in the galaxy UGC 5189A, located about 160 million light years away. Using data from the All Sky Automated Survey telescope in Hawaii taken earlier, astronomers determined this supernova exploded in early October 2010. This composite image of UGC 5189A shows X-ray data from Chandra in purple and optical data from Hubble Space Telescope in red, green and blue. SN 2010jl is the very bright X-ray source near the top of the galaxy. A team of researchers used Chandra to observe this supernova in December 2010 and again in October 2011. The supernova was one of the most luminous that has ever been detected in X-rays. In the first Chandra observation of SN 2010jl, the X-rays from the explosion's blast wave were strongly absorbed by a cocoon of dense gas around the supernova. This cocoon was formed by gas blown away from the massive star before it exploded. In the second observation taken almost a year later, there is much less absorption of X-ray emission, indicating that the blast wave from the explosion has broken out of the surrounding cocoon. The Chandra data show that the gas emitting the X-rays has a very high temperature -- greater than 100 million degrees Kelvin – strong evidence that it has been heated by the supernova blast wave. In a rare example of a cosmic coincidence, analysis of the X-rays from the supernova shows that there is a second unrelated source at almost the same location as the supernova. These two sources strongly overlap one another as seen on the sky. This second source is likely to be an ultraluminous X-ray source, possibly containing an unusually heavy stellar-mass black hole, or an intermediate mass black hole. Image Credit: X-ray: NASA/CXC/Royal Military College of Canada/P.Chandra et al); Optical: NASA/STScI

STAR READIES FOR SPECTACULAR SUPERNOVA

“NASA's Hubble Telescope captured an image of Eta Carinae. This image consists of ultraviolet and visible light images from the High Resolution Channel of Hubble's Advanced Camera for Surveys. The field of view is approximately 30 arcseconds across. The larger of the two stars in the Eta Carinae system is a huge and unstable star that is nearing the end of its life, and the event that the 19th century astronomers observed was a stellar near-death experience. Scientists call these outbursts supernova impostor events, because they appear similar to supernovae but stop just short of destroying their star. Although 19th century astronomers did not have telescopes powerful enough to see the 1843 outburst in detail, its effects can be studied today. The huge clouds of matter thrown out a century and a half ago, known as the Homunculus Nebula, have been a regular target for Hubble since its launch in 1990. This image, taken with the Advanced Camera for Surveys High Resolution Channel, is the most detailed yet, and shows how the material from the star was not thrown out in a uniform manner, but forms a huge dumbbell shape. Eta Carinae is one of the closest stars to Earth that is likely to explode in a supernova in the relatively near future (though in astronomical timescales the "near future" could still be a million years away). When it does, expect an impressive view from Earth, far brighter still than its last outburst: SN 2006gy, the brightest supernova ever observed, came from a star of the same type, though from a galaxy over 200 million light-years away. Image Credit: ESA/NASA”

The above picture and following excerpt is from the NASA website:

OLDEST DOCUMENTED SUPERNOVA

This image combines data from four space telescopes to create a multi-wavelength view of all that remains of RCW 86, the oldest documented example of a supernova. Chinese astronomers witnessed the event in 185 A.D., documenting a mysterious "guest star" that remained in the sky for eight months. X-ray images from NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton Observatory were combined to form the blue and green colors in the image. The X-rays show the interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the supernova. Infrared data from NASA's Spitzer Space Telescope and WISE, Wide-Field Infrared Survey Explorer, shown in yellow and red, reveal dust radiating at a temperature of several hundred degrees below zero, warm by comparison to normal dust in our Milky Way galaxy. By studying the X-ray and infrared data, astronomers were able to determine that the cause of the explosion was a Type Ia supernova, in which an otherwise-stable white dwarf, or dead star, was pushed beyond the brink of stability when a companion star dumped material onto it. Furthermore, scientists used the data to solve another mystery surrounding the remnant -- how it got to be so large in such a short amount of time. By blowing away wind prior to exploding, the white dwarf was able to clear out a huge "cavity," a region of very low-density surrounding the system. The explosion into this cavity was able to expand much faster than it otherwise would have. This is the first time that this type of cavity has been seen around a white dwarf system prior to explosion. Scientists say the results may have significant implications for theories of white-dwarf binary systems and Type Ia supernovae. RCW 86 is approximately 8,000 light-years away. At about 85 light-years in diameter, it occupies a region of the sky in the southern constellation of Circinus that is slightly larger than the full moon. This image was compiled in October 2011. Image Credit: X-ray: NASA/CXC/SAO & ESA; Infared: NASA/JPL-Caltech/B. Williams (NCSU). The above picture and excerpt is from the NASA website:

HUBBLE TELESCOPE MAKES DISTANT SUPERNOVA DISCOVERY

                                                         Picture Courtesy NASA Website

“WASHINGTON -- NASA's Hubble Space Telescope has looked deep into the
distant universe and detected the feeble glow of a star that exploded
more than 9 billion years ago. The sighting is the first finding of
an ambitious survey that will help astronomers place better
constraints on the nature of dark energy, the mysterious repulsive
force that is causing the universe to fly apart ever faster.

"For decades, astronomers have harnessed the power of Hubble to
unravel the mysteries of the universe," said John Grunsfeld,
associate administrator for NASA’s Science Mission Directorate in
Washington. "This new observation builds upon the revolutionary
research using Hubble that won astronomers the 2011 Nobel Prize in
Physics, while bringing us a step closer to understanding the nature
of dark energy which drives the cosmic acceleration." As an
astronaut, Grunsfeld visited Hubble three times, performing a total
of eight spacewalks to service and upgrade the observatory.

The stellar explosion, nicknamed SN Primo, belongs to a special class
called Type Ia supernovae, which are bright beacons used as distance
markers for studying the expansion rate of the universe. Type Ia
supernovae likely arise when white dwarf stars, the burned-out cores
of normal stars, siphon too much material from their companion stars
and explode.

SN Primo is the farthest Type Ia supernova with its distance confirmed
through spectroscopic observations. In these types of observations, a
spectrum splits the light from a supernova into its constituent
colors. By analyzing those colors, astronomers can confirm its
distance by measuring how much the supernova's light has been
stretched, or red-shifted, into near-infrared wavelengths because of
the expansion of the universe.

The supernova was discovered as part of a three-year Hubble program to
survey faraway Type Ia supernovae, opening a new distance realm for
searching for this special class of stellar explosion. The remote
supernovae will help astronomers determine whether the exploding
stars remain dependable cosmic yardsticks across vast distances of
space in an epoch when the cosmos was only one-third its current age
of 13.7 billion years.

Called the CANDELS+CLASH Supernova Project, the census uses the
sharpness and versatility of Hubble's Wide Field Camera 3 (WFC3) to
assist astronomers in the search for supernovae in near-infrared
light and verify their distance with spectroscopy. CANDELS is the
Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and
CLASH is the Cluster Lensing and Supernova Survey.

"In our search for supernovae, we had gone as far as we could go in
optical light," said Adam Riess, the project's lead investigator, at
the Space Telescope Science Institute and The Johns Hopkins
University in Baltimore, Md. "But it's only the beginning of what we
can do in infrared light. This discovery demonstrates that we can use
the Wide Field Camera 3 to search for supernovae in the distant
universe."

The new results were presented on Jan. 11 at the American Astronomical
Society meeting in Austin, Texas.

The supernova team's search technique involved taking multiple
near-infrared images over several months, looking for a supernova's
faint glow. After the team spotted the stellar blast in October 2010,
they used WFC3's spectrometer to verify SN Primo's distance and to
decode its light, finding the unique signature of a Type Ia
supernova. The team then re-imaged SN Primo periodically for eight
months, measuring the slow dimming of its light.

By taking the census, the astronomers hope to determine the frequency
of Type Ia supernovae during the early universe and glean insights
into the mechanisms that detonated them.

"If we look into the early universe and measure a drop in the number
of supernovae, then it could be that it takes a long time to make a
Type Ia supernova," said team member Steve Rodney of The Johns
Hopkins University. "Like corn kernels in a pan waiting for the oil
to heat up, the stars haven't had enough time at that epoch to evolve
to the point of explosion. However, if supernovae form very quickly,
like microwave popcorn, then they will be immediately visible, and
we'll find many of them, even when the universe was very young. Each
supernova is unique, so it's possible that there are multiple ways to
make a supernova."

If astronomers discover that Type Ia supernovae begin to depart from
how they expect them to look, they might be able to gauge those
changes and make the measurements of dark energy more precise. Riess
and two other astronomers shared the 2011 Nobel Prize in Physics for
discovering dark energy 13 years ago, using Type Ia supernova to plot
the universe's expansion rate.

The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. NASA's Goddard Space
Flight Center manages the telescope. The Space Telescope Science
Institute (STScI) conducts Hubble science operations. STScI is
operated for NASA by the Association of Universities for Research in
Astronomy, Inc., in Washington, D.C.”

PULSAR FOUND IN REMAINS OF A SUPERNOVA

The following is an excerpt from the NASA website:

“With the holiday season in full swing, a new image from an assembly of telescopes has revealed an unusual cosmic ornament. Data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton have been combined to discover a young pulsar in the remains of a supernova located in the Small Magellanic Cloud, or SMC. This would be the first definite time a pulsar, a spinning, ultra-dense star, has been found in a supernova remnant in the SMC, a small satellite galaxy to the Milky Way.

In this composite image, X-rays from Chandra and XMM-Newton have been colored blue and optical data from the Cerro Tololo Inter-American Observatory in Chile are colored red and green. The pulsar, known as SXP 1062, is the bright white source located on the right-hand side of the image in the middle of the diffuse blue emission inside a red shell. The diffuse X-rays and optical shell are both evidence for a supernova remnant surrounding the pulsar. The optical data also displays spectacular formations of gas and dust in a star-forming region on the left side of the image. A comparison of the Chandra image with optical images shows that the pulsar has a hot, massive companion.

Astronomers are interested in SXP 1062 because the Chandra and XMM-Newton data show that it is rotating unusually slowly -- about once every 18 minutes. (In contrast, some pulsars are found to revolve multiple times per second, including most newly born pulsars.) This relatively leisurely pace of SXP 1062 makes it one of the slowest rotating X-ray pulsars in the SMC.

Two different teams of scientists have estimated that the supernova remnant around SXP 1062 is between 10,000 and 40,000 years old, as it appears in the image. This means that the pulsar is very young, from an astronomical perspective, since it was presumably formed in the same explosion that produced the supernova remnant. Therefore, assuming that it was born with rapid spin, it is a mystery why SXP 1062 has been able to slow down by so much, so quickly. Work has already begun on theoretical models to understand the evolution of this unusual object.”