Ongoing Assassin Project Has Detected 89 Supernovas To Date

Ohio State University reported that their All-Sky Automated Survey for Supernovae (ASAS-SN, pronounced "assassin") project has had tremendous success in detecting supernovas (supernovae). Since May 2014, ASAS-SN has detected 89 supernovae which is more than all other professional astronomical surveys combined.

The survey uses six 6-inch telescopes located in Hawaii (4) and in Chile (2). Amateurs worldwide has also volunteered their time and equipment to ASAS-SN. ASAS-SN covers the nearest 500 million light years around the Milky Way Galaxy which is about 1 percent of the observable universe.

According to the astronomists, ASAS-SN complements the work done by big telescopes since these telescopes are too sensitive to capture details of bright, nearby events. As an example, the image above was taken by the Sloan Digital Sky Survey (left image). On 03 January 2015, the All-Sky Automated Survey for Supernovae looked at the same region (right image) and detected a bright supernova.

Aside from supernovae, the survey has also detected two tidal disruption events which are extremely rare sightings of what happens when a black hole captures a portion of a nearby star, and many M dwarf flares, which are believed to emanate from stars with extremely strong magnetic fields.

Star Cluster NGC 3293 Nestled Against Clouds of Gas and Dust in the Carina Constellation

ESO’s La Silla Observatory in Chile released a striking image of star cluster NGC 3293 with clouds of glowing red gas and streaks of dust in the background. NGC is composed of young stars are believed to be less than ten million years old and is about 8000 light-years from Earth in the constellation of Carina (The Keel).

Using the Wide Field Imager (WFI) installed on the MPG/ESO 2.2-meter telescope at the observatory, astronomers study young star clusters such as NGC 3293 to learn more about the evolution of stars.

Star cluster are groups of stars that are held together by their own gravitational fields. Open star clusters and globular are the two types of clusters. NGC 3293 is an open star cluster; loosely clustered groups of young stars. The gravitational attraction between the stars in an open star cluster may be weak or non existent.

Globular star clusters are made up of hundreds of thousands of very old stars that are gravitationally bound. These stars are attracted to each other and form a very tight sphere. The stars within a globular star cluster orbit a galactic core and the amount of stars within get denser going toward the center.

These open clusters each formed from a giant cloud of molecular gas and their stars are held together by their mutual gravitational attraction. But these forces are not enough to hold a cluster together against close encounters with other clusters and clouds of gas as the cluster’s own gas and dust dissipates. So, open clusters will only last a few hundred million years, unlike their big cousins, the globular clusters, which can survive for billions of years, and hold on to far more stars.

New 3D Model Gives Insight On How Supernovas are Formed

Credit: Arnett, Meakin and Viallet/AIP Advances

A new model on how supernovas are formed was presented that can explain certain properties of supernovas that existing models cannot. The new model depicts the formation in three dimensions compared to previous one or two dimensional models.

In the new model, the material in the stars are violently mixed together which causes them to expand, contract, eject and then explode into a supernova. This 3D model is described in the article, "Chaos and turbulent nucleosynthesis prior to a supernova explosion" by David Arnett, Casey Meakin and Maxime Viallet which appears in the journal AIP Advances.

Supernovas are stars that run out of fuel or reaches critical mass and explodes. The explosion from a supernova can expel stellar materials at a rate of about 30,000 kilometers per second (10% of the speed of light). A supernova remnant is formed after the explosion and its boundaries are based on the shockwave from the exploding supernova and is made up of the ejected stellar material of dust and gas.

The Crab Nebula is the most popular and well known supernova remnant in the Universe In 1987, a supernova erupted in the Large Magellanic Cloud and afterwards formed the Supernova Remnant 1987A. It was the closest exploding star observed in modern times.

Image Caption: Three-dimensional turbulent mixing in a stratified burning oxygen shell which is four pressure scale heights deep. The yellow ashes of sulphur are being dredged up from the underlying orange core. The multi-scale structure of the turbulence is prominent. Entrained material is not particularly well mixed, but has features which trace the large scale advective flows in the convection zone. Also visible are smaller scale features, which are generated as the larger features become unstable, breaking apart to become part of the turbulent cascade. The white lines indicate the boundary of the computational domain.

Star Cluster Messier 7 Shines Bright At The Tail End of The Scorpion

Star Cluster Messier 7 can be found shining brightly at the end of the tail end of the constellation Scorpius (The Scorpion). This group of stars is also known as Ptolemy's Cluster in honor of Claudius Ptolemy who discovered this star cluster around 130 AD. As the name implies, it is the 7th entry of Charles Messier's Catalog of Nebulae and Star Clusters done in 1764.

Messier 7 is about 800 light years from the Earth and is comprised of about 100 stars. It is a bright patch of stars that is visible to the naked eye found near the tail of the Scorpius constellation.

The latest images from the European Southern Observatory's Wide Field Imager on the MPG/ESO 2.2-metre telescope shows Messier 7 shining like diamonds against the backdrop of a multitude of stars.

These bright stars are believed to be close to exploding into a supernova as it is over 200 million years old.

Messier 7 is an open star cluster. Open star clusters are loose clustered groups of stars that are held together by a very weak gravitational attraction to each other.

ALMA Telescope Finds Evidence of Newly Formed Dust Made from Supernova

Artist's impression of dustfilled supernova 1987A
Credit: Alexandra Angelich (NRAO/AUI/NSF)

Researchers have captured an image of supernova 1987A with newly formed dust that was not present when the supernova was discovered. The amount of new dust comprises about 25% of the Sun's mass.

This observation gives direct evidence to support the theory of the dust making abilities of a supernova. It can also explain why young and newly formed galaxies have a dusty, dusky appearance.

When the supernova was discovered in 1987, the closest observed supernova explosion since 1604, there was only a small amount of dust observed at the time. Using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope, researchers discovered the amount of dust now in the supernova has significantly increased as well as huge amounts of newly formed carbon monoxide and silicon monoxide gas.

The artists impression above shows SN 1987A's inner regions in red where huge amounts of dust were detected and imaged by ALMA. This inner region is contrasted with the outer shell (lacy white and blue circles), where the energy from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation.

Supernova SN 1987 was first observed in February 1987 and achieved peak brightness in May of that year. SN 1987 is around 168,000 light-years away and is located in the Large Magellanic Cloud.

Supernova Remnant at the Dragon's Head Nebula Captured

The European Southern Observatory using the FORS (FOcal Reducer and low dispersion Spectrograph) instrument captured a detailed image of NGC 2035 known as the Dragon's Head Nebula. The image shows filaments of gas and dust clouds that resulted from a supernova explosion.

A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases.

The Dragon's Head Nebula is located in the Large Magellanic Cloud (LMC). The LMC is a galaxy 163,000 light years away and contains around 35 million stars. The LMC is smaller than the Milky Way galaxy at 14,000 light years wide compared to the Milky Way's width of 100,000 light years.

Studying the Evolution of a Supernova Through Supernova Remnant 1987A

Astronomers are intensively studying Supernova Remnant 1987A to find out more about the inner workings of stars, supernovas, and how they interact with the surroundings.

A supernova is an astronomical event where a star runs out of fuel or reaches critical mass and explodes. The explosion from a supernova can expel stellar materials at a rate of about 30,000 kilometers per second (10% of the speed of light).

After the explosion, what is left of the star is a structure called a Supernova Remnant (SNR). The boundaries of a SNR is based on the shockwave from the supernova and is made up of the ejected stellar material of dust and gas.

One of the most popular and well known supernova remnant is the Crab Nebula. Most supernova remnants are named after objects or animals they resemble. Just recently, a SNR was discovered that resembled a Florida Manatee.

In early 1987, a supernova erupted in the Large Magellanic Cloud and afterwards formed the Supernova Remnant 1987A. It was the closest exploding star observed in modern times.

Cosmic Rays Confirmed To Originate From Supernovas In Two Separate Announcements

When stars explode, the supernovas send off shock waves, which accelerate protons to cosmic-ray energies through a process known as Fermi acceleration. In this mechanism, named for Enrico Fermi who first hypothesized it, the protons gain energy from collisions with turbulent magnetic fields on either side of a shock wave. Though many details of Fermi acceleration remain unknown, new results from the Fermi Gamma-ray Space Telescope provide overwhelming evidence that the mechanism is indeed responsible for producing many of the galaxy's cosmic ray protons.
Credit: Greg Stewart, SLAC National Accelerator Laboratory

In two separate announcements (and two separate studies), the European Southern Observatory and the Kavli Institute for Particle Astrophysics and Cosmology at the Department of Energy's (DOE) SLAC National Accelerator Laboratory confirmed that cosmic rays come from exploding stars or supernovas.

Cosmic rays are high energy particles from space. These particles travel at close to the speed of light and originate from outside the Solar System. They have very high energy that they can penetrate the Earth's atmosphere and even through solid rock at the surface. Prior to the announcement, its origin and how it was formed has been a mystery.

The ESO together with the Max Planck Institute for Astronomy in Heidelberg Germany, used the VIMOS Equipment on the Very Large Telescope (VLT) to study SN 1006, a supernova first observed in the year 1006, to gather data and base their discovery of the cosmic ray mystery. Their study, An Integral View of Fast Shocks around Supernova 1006, is appearing in the 14 February 2013 issue of the journal Science.

The Kavli Institute, NASA, and Stanford University used the Large Area Telescope (LAT), which sits onboard the Fermi Gamma-ray Space Telescope to base their findings. They used the telescope to study two supernova remnants, IC 433 and W44. Both are located within the Milky Way with IC 443 5,000 light years away from Earth in the constellation Gemini, and W44 is located about 10,000 light years away, in the constellation of Aquila. Their study, Detection of the Characteristic Pion-Decay Signature in Supernova Remnants, will be appearing in the February 15 2013 issue of the journal Science.

Supernova Remnant W50 Resembles A Manatee

The National Radio Astronomy Observatory has adopted a new nickname for W50 of "The Manatee Nebula," because the likeness between it and a resting Florida Manatee is too uncanny to ignore. Left: The W50 supernova remnant in radio (green) glows against the infrared background of stars and dust (red). Right: A Florida Manatee rests underwater in Three Sisters Springs in Crystal River, Florida.
Credit: Left: NSF's Karl G. Jansky Very Large Array (VLA), NRAO/AUI/NSF, K. Golap, M. Goss; NASA’s Wide Field Survey Explorer (WISE). Right: Tracy Colson

A supernova remnant found in the constellation of Aquila has been imaged and is found to resemble a resting Florida Manatee.

When a star runs out of fuel or reaches critical mass, it explodes into a supernove. The explosion expels stellar material at a rate of about 30,000 kilometers per second (10% of the speed of light).

The structure that results from the supernova is called a Supernova Remnant (SNR). It is bounded by the shockwave from the supernova and is made up of the ejected material from the explosion.

The Crab Nebula is an example of a supernova remnant.

Some of the SNR found in the sky resemble common objects or animals such as the Owl Nebula, The Crab Nebula, or the Veil Nebula.

ESO Wide Field Imager Sets Its Sights On The Seagull Nebula IC-2177

Crab Nebula

Long ago, a nebula used to refer to any astronomical object that is found in the sky. An example of this would be the Andromeda Galaxy which used to be referred to as the Andromeda Nebula.

Now, a nebula is an astronomical object referring to an interstellar cloud of dust and gasses. The two most famous nebulae are the Crab Nebula and the Pillars of Creation. The crab nebula is a six light year wide nebula formed during a supernova.

Nebulae are regions, such as the Pillars of Creation, where astronomers believe stars are formed. These clouds of gas and dust start to form large masses that eventually become stars as these start to grow bigger in size. To a lesser extent, even planets and other objects are also believed to be formed within these regions.

Nebulae are separated into four general groups, Diffuse nebulae, planetary nebulae, protoplanetary nebulae, and a supernova remnant.

A diffuse nebulae is low density cloud formed when a star was produced. A planterary nebula is a cloud of gas formed when a mature star starts ejecting ionized gas. A protoplanetary nebula is a mid stage where gas starts to escape the star before a star starts to eject gasses to form a planetary nebula. A supernova remnant is a special kind of diffuse nebula where the cloud is formed when a star explodes.

This image from ESO’s La Silla Observatory shows part of a stellar nursery nicknamed the Seagull Nebula. This cloud of gas, known as Sh 2-292, RCW 2 and Gum 1, seems to form the head of the seagull and glows brightly due to the energetic radiation from a very hot young star lurking at its heart. The detailed view was produced by the Wide Field Imager on the MPG/ESO 2.2-metre telescope.
Credit: ESO

This new image from ESO’s La Silla Observatory shows part of a stellar nursery nicknamed the Seagull Nebula. This cloud of gas, formally called Sharpless 2-292, seems to form the head of the seagull and glows brightly due to the energetic radiation from a very hot young star lurking at its heart. The detailed view was produced by the Wide Field Imager on the MPG/ESO 2.2-metre telescope.

Nebulae are among the most visually impressive objects in the night sky. They are interstellar clouds of dust, molecules, hydrogen, helium and other ionised gases where new stars are being born. Although they come in different shapes and colours many share a common characteristic: when observed for the first time, their odd and evocative shapes trigger astronomers’ imaginations and lead to curious names. This dramatic region of star formation, which has acquired the nickname of the Seagull Nebula, is no exception.

Astronomers Observe Rare Type 1A Supernova PTF 11kx

A supernova or supernovae is an exploding star that releases much more energy than it normally would. They are extremely luminous and emit a powerful burst of radiation that often briefly outshines an entire galaxy. During this period a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. The explosion expels much or all of a star's material at a velocity of up to 30,000 km/s (10% of the speed of light), driving a shock wave into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant.

A Type Ia supernova is a sub-category of supernova. It comes from an explosion of a white dwarf star, a small but very dense star that is made up mostly of electron-degenerate matter. A white dwarf is a star that has completed its normal life cycle and has ceased nuclear fusion. Despite this, white dwarfs are still capable of further fusion reactions that can generate a great amount of energy.

The supernova PTF 11kx can be seen as the blue dot on the galaxy. The image was taken when the supernova was near maximum brightness by the Faulkes Telescope North. The system is located approximately 600 million light years away in the constellation Lynx.
Credit: BJ Fulton (Las Cumbres Observatory Global Telescope Network)

Berkeley Lab researchers make historic observation of rare Type 1a supernova

Exploding stars called Type 1a supernova are ideal for measuring cosmic distance because they are bright enough to spot across the Universe and have relatively the same luminosity everywhere. Although astronomers have many theories about the kinds of star systems involved in these explosions (or progenitor systems), no one has ever directly observed one—until now.

In the August 24 issue of Science, the multi-institutional Palomar Transient Factory (PTF) team presents the first-ever direct observations of a Type 1a supernova progenitor system. Astronomers have collected evidence indicating that the progenitor system of a Type 1a supernova, called PTF 11kx, contains a red giant star. They also show that the system previously underwent at least one much smaller nova eruption before it ended its life in a destructive supernova. The system is located 600 million light years away in the constellation Lynx.

By comparison, indirect observations of another Type 1a supernova progenitor system (called SN 2011fe, conducted by the PTF team last year) showed no evidence of a red giant star. Taken together, these observations unequivocally show that just because Type 1a supernovae look the same, that doesn't mean they are all born the same way.

"We know that Type 1a supernovae vary slightly from galaxy to galaxy, and we've been calibrating for that, but this PTF 11kx observation is providing the first explanation of why this happens," says Peter Nugent, a senior scientist at the Lawrence Berkeley National Laboratory (Berkeley Lab) and a co-author on the paper. "This discovery gives us an opportunity to refine and improve the accuracy of our cosmic measurements."

"It's a total surprise to find that thermonuclear supernovae, which all seem so similar, come from different kinds of stars," says Andy Howell, a staff scientist at the Las Cumbres Observatory Global Telescope Network (LCOGT) and a co-author on the paper. "How could these events look so similar, if they had different origins?"

A One in a Thousand Discovery, Powered by Supercomputers

Although Type 1a supernovae are rare, occurring maybe once or twice a century in a typical galaxy, Nugent notes that finding a Type 1a progenitor system like PTF 11kx is even more rare. "You maybe find one of these systems in a sample of 1,000 Type 1a supernovae," he says. "The Palomar Transient Factory Real-Time Detection Pipeline was crucial to finding PTF 11kx."

The PTF survey uses a robotic telescope mounted on the 48-inch Samuel Oschin Telescope at Palomar Observatory in southern California to scan the sky nightly. As the observations are taken, the data travels more than 400 miles via high-speed networks--including the National Science Foundation's High Performance Wireless Research and Education Network and the Department of Energy's Energy Sciences Network (ESnet)--to the National Energy Research Scientific Computing Center (NERSC), located at Berkeley Lab. There, the Real-time Transient Detection Pipeline uses supercomputers, a high-speed parallel filesystem and sophisticated machine learning algorithms to sift the data and identify events for scientists to follow up on.

Baryon Oscillation Spectroscopic Survey (BOSS) Publicly Release Data On More Than 750,000 Galaxies, Quasars, and Stars

BOSS is capturing accurate spectra for millions of astronomical objects by using 2,000 plug plates that are placed at the Sloan Foundation Telescope’s focal plane. Each of the 1,000 holes drilled in a single plug plate captures the light from a specific galaxy, quasar, or other target, and conveys its light to a sensitive spectrograph through an optical fiber. The plates are marked to indicate which holes belong to which bundles of the thousand optical fibers that carry the object’s light.
Credit: Lawrence Berkeley National Laboratory and Sloan Digital Sky Survey III

The Baryon Oscillation Spectroscopic Survey (BOSS) is an astronomical survey designed to measure the rate of expansion of the Universe. It will focus on the spatial distribution of Luminous Red Galaxies (LRGs) and quasars.

BOSS is one of the four components of the Sloan Digital Sky Survey (SDSS-III). SDSS-III is used to cover distant quasars at far reaches of the universe, the distribution of galaxies, the properties of stars in the Milky Way and also subjects such as dark matter and dark energy in the universe.

On March 2012, BOSS announced the most accurate measurement yet of the distance scale of the universe during the era when dark energy turned on.

The first public data release from BOSS, the Baryon Oscillation Spectroscopic Survey

The Third Sloan Digital Sky Survey (SDSS-III) has issued Data Release 9 (DR9), the first public release of data from the Baryon Oscillation Spectroscopic Survey (BOSS). In this release BOSS, the largest of SDSS-III's four surveys, provides spectra for 535,995 newly observed galaxies, 102,100 quasars, and 116,474 stars, plus new information about objects in previous Sloan surveys (SDSS-I and II).

"This is just the first of three data releases from BOSS," says David Schlegel of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), an astrophysicist in the Lab's Physics Division and BOSS's principal investigator. "By the time BOSS is complete, we will have surveyed more of the sky, out to a distance twice as deep, for a volume more than five times greater than SDSS has surveyed before – a larger volume of the universe than all previous spectroscopic surveys combined."

Spectroscopy yields a wealth of information about astronomical objects including their motion (called redshift and written "z"), their composition, and sometimes also the density of the gas and other material that lies between them and observers on Earth. The BOSS spectra are now freely available at http://sdss3.org to a public that includes amateur astronomers, astronomy professionals who are not members of the SDSS-III collaboration, and high-school science teachers and their students.

VLT Detailed Image of Spiral Galaxy NGC 1187 That Has Hosted Two Supernova Explosions

A new image taken with ESO’s Very Large Telescope shows the galaxy NGC 1187. This impressive spiral lies about 60 million light-years away in the constellation of Eridanus (The River). NGC 1187 has hosted two supernova explosions during the last thirty years, the latest one in 2007. This picture of the galaxy is the most detailed ever taken.

A supernova is an exploding star that expends more energy than it normally would. Supernovae or supernovas are extremely luminous and emit a powerful burst of radiation that often briefly outshines an entire galaxy. During this period a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. The explosion expels much or all of a star's material at a velocity of up to 30,000 km/s (10% of the speed of light), driving a shock wave into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant.

It is estimated that one to two supernovae explode in the Milky Way each century. The spiral galaxy NGC 1187 has had two supernova explosions detected, 25 years apart. The first was in 1982, and the second in 2007.

A Blue Whirlpool in The River

The galaxy NGC 1187 ^[1] is seen almost face-on, which gives us a good view of its spiral structure. About half a dozen prominent spiral arms can be seen, each containing large amounts of gas and dust. The bluish features in the spiral arms indicate the presence of young stars born out of clouds of interstellar gas.

Looking towards the central regions, we see the bulge of the galaxy glowing yellow. This part of the galaxy is mostly made up of old stars, gas and dust. In the case of NGC 1187, rather than a round bulge, there is a subtle central bar structure. Such bar features are thought to act as mechanisms that channel gas from the spiral arms to the centre, enhancing star formation there.

Around the outside of the galaxy many much fainter and more distant galaxies can also be seen. Some even shine right through the disc of NGC 1187 itself. Their mostly reddish hues contrast with the pale blue star clusters of the much closer object.

Bright High Mass Stars Are Part Of Binary Star Systems And Evolve To A Single Star

A new study using ESO’s Very Large Telescope (VLT) has shown that most very bright high-mass stars, which drive the evolution of galaxies, do not live alone. Almost three quarters of these stars are found to have a close companion star, far more than previously thought. Surprisingly most of these pairs are also experiencing disruptive interactions, such as mass transfer from one star to the other, and about one third are even expected to ultimately merge to form a single star. The results are published in the 27 July 2012 issue of the journal Science.

A binary star is a star system where two stars orbit around their common center of mass. The primary star would be the brightest of the two stars while the other is referred to as the companion star (comes) or secondary star.

A vast majority of all stars in the Milky Way Galaxy are binaries or members of more complex multiple star systems.

Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated. This also determines an empirical mass-luminosity relationship (MLR) from which the masses of single stars can be estimated.

The Brightest Stars Don't Live Alone

The Universe is a diverse place, and many stars are quite unlike the Sun. An international team has used the VLT to study what are known as O-type stars, which have very high temperature, mass and brightness^[1]. These stars have short and violent lives and play a key role in the evolution of galaxies. They are also linked to extreme phenomena such as “vampire stars”, where a smaller companion star sucks matter off the surface of its larger neighbour, and gamma-ray bursts.

“These stars are absolute behemoths,” says Hugues Sana (University of Amsterdam, Netherlands), the lead author of the study. “They have 15 or more times the mass of our Sun and can be up to a million times brighter. These stars are so hot that they shine with a brilliant blue-white light and have surface temperatures over 30 000 degrees Celsius.”

The astronomers studied a sample of 71 O-type single stars and stars in pairs (binaries) in six nearby young star clusters in the Milky Way. Most of the observations in their study were obtained using ESO telescopes, including the VLT.

By analysing the light coming from these targets^[2] in greater detail than before, the team discovered that 75% of all O-type stars exist inside binary systems, a higher proportion than previously thought, and the first precise determination of this number. More importantly, though, they found that the proportion of these pairs that are close enough to interact (through stellar mergers or transfer of mass by so-called vampire stars) is far higher than anyone had thought, which has profound implications for our understanding of galaxy evolution.

Baryon Oscillation Spectroscopic Survey (BOSS) Studying and Observing the Accelerating and Expanding Universe

Since 1992, it has been suggested that the universe appears to be expanding at an increasing rate. An accelerating universe means that a distant galaxy is receding from the Earth at a velocity that is continuously increasing over time. In 1998, observations of type Ia supernova also suggested that the expansion of the universe has been accelerating since around redshift of z~0.5.

A redshift happens when light observed coming from an object that is moving away is proportionally increased in wavelength, or shifted to the red end of the spectrum. In simple terms, the farther an object moves away, the stronger the light in the red spectrum is visible.

Dark energy, dark fluid or phantom energy as it is sometimes called is used to explain the universe's accelerating expansion. The most important property of dark energy is that it has negative pressure which is distributed relatively evenly and uniformly in space. The simplest explanation for dark energy is that it is a cosmological constant or vacuum energy

Baryon Oscillation Spectroscopic Survey (BOSS)

The Baryon Oscillation Spectroscopic Survey (BOSS) is an astronomical survey designed to measure the rate of expansion of the Universe. It will focus on the spatial distribution of Luminous Red Galaxies (LRGs) and quasars.

BOSS is one of the four components of the Sloan Digital Sky Survey (SDSS-III). SDSS-III is used to cover distant quasars at far reaches of the universe, the distribution of galaxies, the properties of stars in the Milky Way and also subjects such as dark matter and dark energy in the universe.

First results from BOSS

Some six billion light years ago, almost halfway from now back to the big bang, the universe was undergoing an elemental change. Held back until then by the mutual gravitational attraction of all the matter it contained, the universe had been expanding ever more slowly. Then, as matter spread out and its density decreased, dark energy took over and expansion began to accelerate.

Today BOSS, the Baryon Oscillation Spectroscopic Survey, the largest component of the third Sloan Digital Sky Survey (SDSS-III), announced the most accurate measurement yet of the distance scale of the universe during the era when dark energy turned on.

"We've made precision measurements of the large-scale structure of the universe five to seven billion years ago – the best measure yet of the size of anything outside the Milky Way," says David Schlegel of the Physics Division at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), BOSS's principal investigator. "We're pushing out to the distances when dark energy turned on, where we can start to do experiments to find out what's causing accelerating expansion."

Eta Carinae: Studying the Great Eruption

First catalogued by Edmund Halley in 1677, Eta Carinae is one of the most massive and most visible stars in the sky. It is composed of two parts, Eta Car A, the primary star and Eta Car B, the secondary star. The star is 7,500 light-years away in the constellation Carina. Because of the star’s extremely high mass, it is unstable and uses its fuel very quickly, compared to other stars. Such massive stars also have a short lifetime, and it is expected that Eta Carinae will explode within a million years.

Eta Carinae, one of the most massive stars in our Milky Way galaxy, unexpectedly increased in brightness in the 19th century. In 1843 Eta Carinae was one of the brightest stars in the sky. For ten years it was the second-brightest star in the sky. It then slowly faded until, in 1868, it became invisible in the sky. Eta Carinae started to brighten again in the 1990s and was again visible to the naked eye. Around 1998 and 1999 its brightness suddenly and unexpectedly doubled.

The increase in luminosity was so great that it earned the rare title of Great Eruption. New research from a team including Carnegie's Jose Prieto, now at Princeton University, has used a "light echo" technique to demonstrate that this eruption was much different than previously thought. Their work is published Feb. 16 in Nature.

Eta Carinae is a Luminous Blue Variable (LBV), meaning it has periods of dimness followed by periods of brightness. The variations in brightness of an LBV are caused by increased instability and loss of mass. The Great Eruption was an extreme and unique event in which the star, which is more than 100 times the mass of the Sun, lost several times the mass of the Sun. Scientists have believed that this rare type of eruption was caused by a stellar wind.