Astronomers may have found most powerful supernova

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• “This may be the most powerful supernova ever seen by anybody,” Ohio State University professor says

An international team of astronomers may have discovered the biggest and brightest supernova ever.

The explosion was 570 billion times brighter than the sun and 20 times brighter than all the stars in the Milky Way galaxy combined, according to a statement from The Ohio State University, which is leading the study. Scientists are straining to define its strength.

“This may be the most powerful supernova ever seen by anybody … it’s really pushing the envelope on what is possible,” study co-author Krzysztof Stanek, an astronomer at Ohio State, was quoted as saying in The Los Angeles Times.

The team of astronomers released their findings this week in the journal Science. The explosion and a gas cloud that resulted are called ASASSN-15lh after the team of astronomers, All Sky Automated Survey for Supernovae, that discovered it last June.

A supernova is a rare and often dramatic phenomenon that involves the explosion of most of the material within a star. Supernovas can be very bright for a short time and usually release huge amounts of energy.

Searching for the power source

This blast created a massive ball of hot gas that the astronomers are studying through telescopes around the world, Ohio State said. It cannot be seen with the naked eye because it is 3.8 billion light years from Earth.

There’s an object about 10 miles across in the middle of the ball of gas that astronomers are trying to define.

“The honest answer is at this point that we do not know what could be the power source for ASASSN-15lh,” said Subo Dong, lead author of the Science paper, according to Ohio State. He is a Youth Qianren Research Professor of astronomy at the Kavli Institute for Astronomy and Astrophysics at Peking University.

Todd Thompson, professor of astronomy at Ohio State, said the object in the center may be a rare type of star called a millisecond magnetar. Spawned by a supernova, it’s a rapidly spinning, dense star with a powerful magnetic field.

Could it be a ‘supermassive black hole’?

To achieve the brightness recorded, the magnetar would have to spin 1,000 times a second and “convert all that rotational energy to light with nearly 100% efficiency,” Thompson said, according to the Ohio State press release. “It would be the most extreme example of a magnetar that scientists believe to be physically possible.”

The question of whether a suprnova truly caused the space explosion may be settled later this year with help from the Hubble Space Telescope, which will allow astronomers to see the host galaxy surrounding the object in center of the ball of gas, Ohio State said.

If it’s not a magnetar, it may be unusual nuclear activity around “a supermassive black hole,” Ohio State said.

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Space oddity: Bizarre hybrid star found after 40-year search

Image showing the location of the star HV 2112 — a hybrid between a red supergiant and a neutron star — in the Small Magellanic Cloud, a dwarf galaxy that lies about 200,000 light-years from Earth.Phil Massey, (Lowell Observatory)

Astronomers have apparently discovered the first of a class of strange hybrid stars, confirming theoretical predictions made four decades ago.

In 1975, physicist Kip Thorne and astronomer Anna Zytkow proposed the existence of odd objects that are hybrids between red supergiants and neutron stars — the collapsed, superdense remnants of supernova explosions.

These so-called Thorne-Zytkow objects (TZOs) likely form when a red supergiant gobbles up a nearby neutron star, which sinks down into the giant’s core, researchers said. TZOs look like ordinary red supergiants, like the famed star Betelgeuse in the constellation Orion, but differ in their chemical fingerprints, the theory goes. [Top 10 Star Mysteries]

“Studying these objects is exciting because it represents a completely new model of how stellar interiors can work,” study leader Emily Levesque, of the University of Colorado Boulder, said in a statement.

“In these interiors we also have a new way of producing heavy elements in our universe,” she added. “You’ve heard that everything is made of ‘star stuff’ — inside these stars we might now have a new way to make some of it.”

And now Levesque and her team say they have probably found the first TZO — a star called HV 2112 in the Small Magellanic Cloud, a dwarf galaxy that lies about 200,000 light-years away.

The researchers used the 6.5-meter Magellan Clay telescope in Chile to study the light emitted by HV 2112. They found the starlight to be highly enriched in rubidium, lithium and molybdenum, just as theory predicts for TZOs. (Normal red supergiants produce these elements as well, but not in such abundance, scientists said.)

The new data, while suggestive, do not represent a slam-dunk discovery for TZOs quite yet, researchers said.

“We could, of course, be wrong,” co-author Philip Massey, of Lowell Observatory in Flagstaff, Arizona, said in a statement.

“There are some minor inconsistencies between some of the details of what we found and what theory predicts,” he added. “But the theoretical predictions are quite old, and there have been a lot of improvements in the theory since then. Hopefully our discovery will spur additional work on the theoretical side now.”

The find means a lot to Zytkow, who is a co-author of the new study.

“I am extremely happy that observational confirmation of our theoretical prediction has started to emerge,” said Zytkow, who is based at the University of Cambridge in England. “Since Kip Thorne and I proposed our models of stars with neutron cores, people were not able to disprove our work. If theory is sound, experimental confirmation shows up sooner or later. So it was a matter of identification of a promising group of stars, getting telescope time and proceeding with the project.”

The study has been accepted for publication in the Monthly Notices of the Royal Astronomical Society Letters.

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Neutrino telescopes launch new era of astronomy

This image shows the highest energy neutrino ever observed (1.14 petaelectronvolts), which scientists named ‘Ernie,’ as seen by the IceCube Neutrino Observatory at the South Pole on Jan. 3, 2012. Image released Nov. 21, 2013. (ICECUBE COLLABORATION)

The recent discovery of neutrino particles bombarding Earth from outer space has ushered in a new era in neutrino astronomy, scientists say.

Neutrinos are produced when cosmic rays interact with their surroundings, yielding particles with no electrical charge and negligible mass. Scientists have wondered about the source of cosmic rays since they were discovered, and finding cosmic neutrinos could provide clues about the origin of the mysterious rays.

In November, a team of scientists announced the discovery of cosmic neutrinos by the giant IceCube Neutrino Observatory in Antarctica. [Neutrinos from Beyond the Solar System Found (Images)]

“We now have the opportunity to determine what the sources are, if we are indeed seeing sources of cosmic rays,” said Francis Halzen, principal investigator of the IceCube observatory and a theoretical physicist at the University of Wisconsin-Madison. “The big difference why it’s new astronomy is that we are not using light, we are using neutrinos to look at the sky.”

Cosmic visitors
Neutrinos are the social misfits of the particle world — they rarely interact with matter. Produced in some of the most violent, but unknown, events in the universe, they travel to Earth at close to the speed of light and in straight lines, which reveals information about their origin. Supernovas, active galactic nuclei and black holes are some of the possible sources for these ghostly particles.

Until recently, scientists had only detected neutrinos beyond Earth from the sun or from a supernova in the Large Magellanic Cloud in 1987. No neutrinos from distant cosmic sources had been seen.

But in April 2012, IceCube recorded two neutrinos with extremely high energies — almost a billion times that of the ones found in 1987 — that could only have come from a high-energy source outside the solar system. After looking deeper into the data, scientists found a total of 28 high-energy neutrinos with energies greater than 30 teraelectronvolts (TeV), reporting their finding in the journal Science.

The finding opens the door to a new kind of astronomy that would “image” the sky in the light of neutrinos, rather than photons. “Each time we find another way to make a picture of the sky — using gamma rays, X-rays, radio waves — you have always been able to see things you never saw before,” Halzen told SPACE.com.

The successful completion of IceCube and the prospect of other telescopes on the horizon have set the neutrino world abuzz.

“It is the point in time when it becomes real,” said Uli Katz, an astrophysicist at the University of Erlangen-Nuremberg in Germany, who is helping spearhead KM3NeT, a planned neutrino telescope in the Mediterranean Sea.

Neutrino telescopes
The idea of neutrino detectors goes back to the 1950s, when Clyde Cowan and Frederick Reines first detected neutrinos from a nuclear reactor. Later, scientists detected solar neutrinos and atmospheric neutrinos.

Because neutrinos interact so weakly with other particles, you have to have a very large amount of matter in order to detect them. When neutrinos smash into protons or neutrons inside an atom, they produce secondary particles that give off a blue light called Cherenkov radiation. You need a large, transparent detector shielded from daylight to see them, so scientists build them deep underwater or embedded in ice.

The Deep Underwater Muon And Neutrino Detector  (DUMAND) Project was a proposed underwater neutrino telescope in the Pacific Ocean near the island of Hawaii. The observatory would have stretched nearly 0.25 cubic miles of ocean more than 3 miles beneath the surface. Started in 1976 but canceled in 1995, DUMAND paved the way for successor projects.

Scientists built the Antarctic Muon And Neutrino Detector Array (AMANDA) in the ice beneath the South Pole, which ultimately became part of the IceCube observatory. IceCube, which was completed in 2010, consists of a cubic kilometer grid of sensors embedded below 4,900 feet of ice.

In Europe, scientists are developing plans for KM3NeT, which will span 1.2 cubic miles in the Mediterranean. And scientists at the Baikal Neutrino Telescope in Russia’s Lake Baikal, the largest freshwater lake by volume in the world, are planning to build the Gigaton Volume Detector (GVD), which would be one cubic km.

The latest neutrino telescopes will enable more than just new astrophysics. Scientists are starting to use them to look for dark matter, the unknown substance that makes up roughly 85 percent of the total matter in the universe. In addition, being able to detect high-energy neutrinos will enable new particle physics that even the best particle accelerators can’t achieve.

“I expect lot of effort will be invested to increase this field in its capabilities,” Katz said.

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Coldest Known Object In Space Reveals Its Ghostly Figure

Image Caption: The Boomerang Nebula reveals its true shape with ALMA. The background blue structure, as seen in visible light (HST), shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in red. (FULL IMAGE) (Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai)

The Boomerang Nebula, at a crisp one degree Kelvin (-458 degrees Fahrenheit), is the coldest known object in the Universe. In fact, the Boomerang Nebula is colder than the faint afterglow of the Big Bang, which is the natural background temperature of space.

To learn more about this intriguing object, a team of astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to investigate its frigid properties and determine its true shape, which is eerily ghost-like.

The nebula appeared lopsided when originally observed with ground-based telescopes. This lopsidedness is how this nebula got its name. A bow-tie-like structure was revealed when astronomers later used Hubble Space Telescope observations. According to the new ALMA observations, the Hubble data only told part of the story. The twin lobes seen in the Hubble image may actually be a trick of the light as seen at visible wavelengths.

“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” saidRaghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory (JPL). “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”

The results of this study were published in the Astrophysical Journal.

Located approximately 5,000 light-years away in the constellation Centaurus, the Boomerang Nebula is a relatively young example of an object known as a planetary nebula. Contrary to their name, planetary nebulae are actually the end-of-life phases of stars like our Sun that have sloughed off their outer layers. The remaining centers are white dwarf stars, emitting intense ultraviolet radiation that causes the gas in the nebulae to glow and emit light in brilliant colors.

The Boomerang is an example of a pre-planetary nebula, which is a stage in a star’s life immediately preceding the planetary nebula phase. At this point, the central star is not yet hot enough to emit enough electrical ultraviolet radiation to produce its characteristic glow. A pre-planetary nebula is seen by starlight reflecting off its dust grains.

The gas outflow from the Boomerang Nebula’s star is expanding rapidly and cooling itself in the process, in a way similar in principle to the way refrigerators use expanding gas to produce cold temperatures. The astronomers were able to gauge the temperature of the gas in the nebula by seeing how it absorbed the cosmic microwave background radiation, which has a very uniform temperature of 2.8 degrees Kelvin (-455 degrees Fahrenheit).

“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”

Single-dish millimeter wavelength telescopes, however, did not detect the narrow waist observed by the Hubble. Rather, they found a more uniform and nearly spherical outflow of material.

ALMA has unprecedented resolution, which allowed the astronomers to reconcile the discrepancy. The team was able to detect the double-lobe structure that is seen in the Hubble image, but only in the inner regions of the nebula, by observing the distribution of carbon monoxide molecules, which glow brightly at millimeter wavelengths. A more elongated cloud of cold gas that is roughly round was observed farther out.

A dense lane of millimeter-sized dust grains were found to be surrounding the star, providing an explanation for why the outer cloud has an hourglass shape in visible light. The dust grains form a mask that shade a portion of the central star, allowing its light to leak out in narrow but opposite directions in the cloud. This forms the hourglass appearance.

“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”

The current findings also suggest that the outer fringes of the nebula are beginning to warm, even though they are slightly colder than the cosmic microwave background. The warming could be caused by the photoelectric effect — an effect first proposed by Albert Einstein in which light is absorbed by solid material, which then re-emits electrons.

 

Largest Known Star Self-Destructs While Astronomers Observe

(European Southern Observatory)

A group of international scientists have been observing as the largest known star in the Universe tears itself apart.

Astronomers from the UK, Chile, Germany and the US have watched as W26 in the Westerlund 1 star cluster shed its outer layers and flings a huge cloud of glowing hydrogen gas out to return enriched material back to the interstellar medium.

The latest observation, reported in the journal Monthly Notices of the Royal Astronomical Society, is considered to be a vital step in understanding how massive stars help enrich the space between stars, which is necessary for forming planetary systems.

Westerlund 1 is the most massive cluster of stars in the Milky Way galaxy. The cluster, which is 16,000 light years away from Earth, is home to several hundred thousand stars. Astronomers used the Very Large Telescope (VST) at the European Southern Observatory’s Paranal Observatory in Chile to observe Westerlund 1 when they happened to discover W26.

They realized that the star was probably the largest ever discovered, with a radius 1,500 times larger than our Sun. They also discovered that W26 is one of the most luminous red supergiants ever seen.

Glowing hydrogen-gas clouds like the one seen around W26 are rarely found around massive stars, and are even rarer around red supergiants. This was the first ionized nebula ever discovered around such a star. While W26 is too cool to make the gas glow, the astronomers believe the source of the ionizing radiation could be either hot blue stars or possibly a companion star.

The nebula around W26 is similar to the nebula surrounding SN1987A, which is the remnant of a star that exploded as a supernova in 1987. SN1987A was the closest observed supernova to Earth since 1604, and it gave astronomers a chance to better understand the properties of these explosions.

Astronomers will be able to use the new nebula around W26 to better understand the mass loss processes around massive stars. Stars with masses tens of times larger than the Sun live very short and dramatic lives, with some having lifetimes of less than a few million years before they exhaust all of their nuclear fuel and explode as a supernova.

When a massive star reaches the end of its life it becomes highly unstable, ejecting a considerable amount of material from its outer envelopes. This material has been enriched by nuclear reactions deep within the star and includes many of the elements necessary for forming rocky planets like Earth. Knowing more about how this material is ejected and how it affects the evolution of the star would enable scientists to better understand the evolution of our universe.

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6 Mind Blowing Things Nobody Taught You About Black Holes

Black holes are what happens when the universe divides by zero and eats anything that tries to notice. They’re cosmological grizzly bears: an inevitable result of nature that is majestic and terrifying to every species intelligent enough to comprehend them.

Black holes happen when reality has an overflow error: you put too much stuff in one place, and it breaks both the stuff and the place with gravity. Gravity is usually the responsible older sibling of the universe, always pulling things together. Black holes are where gravity goes full Al Capone, calls a meeting of all the fundamental forces of existence and makes a big showy spectacle of crushing them. It doesn’t just crush matter; it crushes the quantum laws that define matter, stomps them all into a compacted nugget until matter stops existing so much. It simply overrides reality.

And yet, most people treat them like cosmic vacuum cleaners. Science fiction characters are worse at understanding black holes than they are at aiming laser weapons, and the coverage they get in most schools only encourage students to kill themselves with trampolines and bowling balls. That’s a shame, since black holes are literally the ultimate everything, so we’re looking at how cool they are.

#6. They’re the Brightest Things in the Sky

“Black hole” is as simple and descriptive a title as “Pied Piper of Hamelin,” and equally misleading. The one thing everybody knows about black holes is that not even light can escape, meaning they’re pictured as the interstellar equivalent of open manhole covers: pitch-black doom awaiting the unwary. But black holes are often the brightest points in the sky.

A black hole.

What people forget is that while there is an “event horizon” boundary inside of which light can’t escape, there’s also an “entire rest of the universe” where it can, often in galaxy-blinding quantities. When a rotating black hole consumes a cloud of interstellar gas, the material is drawn into a spiral, like fluid swirling down the plughole of existence … which is actually what’s cosmologically happening.

The hair around the universe’s plughole is ENTIRE GALAXIES.

Meteors light up because a thin layer of gas is being compressed by plummeting space rock and further heated by friction. When gas clouds fall into a black hole, the whole thing is being compressed, plummeting, and being heated by friction. The consumed cloud is its own meteor and atmosphere, and both are burning with cosmic fire. They get so hot, they don’t just glow white, they glow X-ray, converting 10 percent of their total mass into pure energy. For comparison, fusion warheads only convert 0.5 percent of their mass into energy. Understand: Black holes create a place where dropping something releases 20 times more energy than thermonuclear detonation. And our galaxy’s central black hole, Sagittarius A*, will be doing that this year.
Black holes can glow so brightly that they defeat their own gravity. Supermassive black holes can reach the Eddington limit, where continuum radiation force defeats the otherwise irresistible gravitational attraction. (That sentence contains more band names and anime series subtitles than anything else I’ve ever written.) The radiation becomes so intense that it blows away the incoming material. And this isn’t radiation as in “nuclear”; this is radiation as in “light.” As in “move toward the light, except in the real heavens, the light can be so intense that it shoves you back.”

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“Oddball” Galaxy Contains the Biggest Black Hole Yet

Image of lenticular galaxy NGC 1277 taken with Hubble Space Telescope. (NASA/ESA/Andrew C. Fabian)

It’s thought that at the heart of most if not every spiral galaxy (as well as some dwarf galaxies) there’s a supermassive black hole, by definition containing enormous amounts of mass — hundreds of millions, even billions of times the mass of our Sun packed into an area that would fit inside the orbits of the planets. Even our own galaxy has a central SMBH — called Sgr A*, it has the equivalent of 4.1 million solar masses.

Now, astronomers using the Hobby-Eberly Telescope at The University of Texas at Austin’s McDonald Observatory have identified what appears to be the most massive SMBH ever found, a 17 billion solar mass behemoth residing at the heart of galaxy NGC 1277.

Located 220 million light-years away in the constellation Perseus, NGC 1277 is a lenticular galaxy only a tenth the size of the Milky Way. But somehow it contains the most massive black hole ever discovered, comprising a staggering 14% of the galaxy’s entire mass.

“This is a really oddball galaxy,” said Karl Gebhardt of The University of Texas at Austin, a team member on the research. “It’s almost all black hole. This could be the first object in a new class of galaxy-black hole systems.”

The study was led by Remco van den Bosch, who is now at the Max Planck Institute for Astronomy (MPIA).

It’s estimated that the size of this SMBH’s event horizon is eleven times the diameter of Neptune’s orbit — an incredible radius of over 300 AU.

How the diamater of the black hole compares with the orbit of Neptune (D. Benningfield/K. Gebhardt/StarDate)

 

Although previously imaged by the Hubble Space Telescope, NGC 1277′s monster black hole wasn’t identified until the Hobby-Eberly Telescope Massive Galaxy Survey (MGS) set its sights on it during its mission to study the relationship between galaxies and their central black holes. Using the HET data along with Hubble imaging, the survey team calculated the mass of this black hole at 17 billion solar masses.

“The mass of this black hole is much higher than expected,” said Gebhardt, “it leads us to think that very massive galaxies have a different physical process in how their black holes grow.”

To date, the HET team has observed 700 of their 800 target galaxies.

In the video below, Remco van den Bosch describes the discovery of this unusually super supermassive black hole:

Read more on the UT Austin’s McDonald Observatory press release here, or this press release from the Max Planck Institute for Astronomy.

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What’s the Coolest Place in the Universe?

The coolest place in the Universe is nearly at absolute zero. (International Falls Chamber of Commerce/Pete Schultz)

It’s not Miami Beach, if that’s what you were thinking. Nor is it the North Pole.

The coldest place known is inside the Boomerang Nebula. It is in the constellation of Centaurus, 5000 light-years from Earth. Planetary nebulae form around a bright, central star when it expels gas in the last stages of its life.

The Boomerang Nebula is one of the Universe’s peculiar places. In 1995, using the 15-metre Swedish ESO Submillimetre Telescope in Chile, astronomers Sahai and Nyman revealed that it is the coldest place in the Universe found so far. With a temperature of -272°C, it is only one degree warmer than absolute zero (the lowest limit for all temperatures). Even the -270°C background glow from the Big Bang is warmer than this nebula. It is the only object found so far that has a temperature lower than the background radiation.

The general bow-tie shape of the Boomerang appears to have been created by a very fierce wind, some 310,000 mph, blowing ultracold gas away from the dying central star. The star has been losing as much as one-thousandth of a solar mass of material per year for 1,500 years, astronomers say. This is 10-100 times more than in other similar objects. The rapid expansion of the nebula has enabled it to become the coldest known region in the universe.

Light from universe’s first stars seen

Nov. 1, 2012: Ultraviolet and visible light emitted by all the stars that ever existed is still coursing through the universe. Astronomers refer to this “fog” of starlight as the extragalactic background light (EBL). (NASA’s Goddard Space Flight Center)

Astronomers have spotted light from the very first stars in the universe, which are almost as old as time itself.

Shortly after the Big Bang 13.7 billion years ago, the universe cooled enough to let atoms form, which eventually clumped together to create the first stars. Ever since these stars ignited, their light has been filling the universe, creating a pervasive glow throughout space that each successive generation of stars adds to.

Now, astronomers have detected this glow — called the extragalactic background light, or EBL — and have separated out the light from later stars, isolating the contribution from the first stars that ever existed.

“The EBL is the ensemble of photons generated by all the stars and also all the black holes in the universe,” said astrophysicist Marco Ajello of the SLAC National Accelerator Laboratory in California, who led the research. “The EBL also includes the light of the first massive stars that ever shone. We have a fairly good knowledge of the light emitted by ‘normal’ stars. Thus, by measuring the EBL we are able to constrain the light of the first stars.”

‘By measuring the extragalactic background light, we are able to constrain the light of the first stars.’

– astrophysicist Marco Ajello of the SLAC National Accelerator Laboratory

Ajello and his team did not measure the EBL directly, but they detected it by analyzing measurements of distant black holes made by NASA’s Fermi Gamma-Ray Space Telescope. Fermi studied light from objects called blazars, which are giant black holes that release copious amounts of light while gobbling up large meals of matter.

“We use [blazars] as cosmic lighthouses,” Ajello said. “We observe their dimming due to the EBL ‘fog’. This allows us to quantify how much EBL there is between us and the blazars. As blazars are distributed across the universe, we can measure the EBL at different epochs.”

The study was able to probe light emitted by stars that existed when the universe was just 0.6 billion years old or so — relatively an infant.

These first stars are thought to have been quite different from stars that form today. In general, they were much more massive, containing up to hundreds of times the mass of our sun, and burned hotter, brighter, and for shorter lifetimes than stars today. [Gallery: History & Structure of the Universe]

This plot shows the locations of 150 blazars (green dots) used in the EBL study. Image released Nov. 1, 2012.

The new measurements should help astronomers answer some of their most basic questions about the first generations of stars, such as how quickly they formed, and how soon after the birth of the universe the first stars came to be, researchers said.

Already, the scientists have found that the first stars’ peak formation rate must have been lower than previously thought.

Ultimately, the researchers would like to constrain this parameter further, and eventually to glimpse these ancient stars themselves. Future technology, such as NASA’s successor to the Hubble Space Telescope, called the James Webb Space Telescope (expected to come online by 2018), should come closer to doing the job.

“Detecting these stars is very important, but currently impossible,” Ajello said. “The Webb Telescope in a few years might be able to see the first galaxies (not the first stars though). In this way we are already able to set constraints on the amount and role of these stars in the early universe.”

The findings are reported in the Nov. 2 issue of the journal Science.
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What’s the smallest thing in the universe?

One contender for the smallest thing in the universe is the singularity at the center of a black hole. (Shown here, an artist’s drawing of a black hole pulling gas away from a companion star. (NASA E/PO, Sonoma State University, Aurore Simonnet)

Just how small is the universe’s smallest stuff anyway?

People once thought grains of sand were the building blocks of what we see around us. Then the atom was discovered, and it was thought indivisible, until it was split to reveal protons, neutrons and electrons inside. These too, seemed like fundamental particles, before scientists discovered that protons and neutrons are made of three quarks each.

“This time we haven’t been able to see any evidence at all that there’s anything inside quarks,” said physicist Andy Parker. “Have we reached the most fundamental layer of matter?”

And even if quarks and electrons are indivisible, Parker said, scientists don’t know if they are the smallest bits of matter in existence, or if the universe contains objects that are even more minute. [Graphic: Nature’s Tiniest Particles]

Parker, a professor of high-energy physics at England’s Cambridge University, recently hosted a television special on the U.K.’s BBC Two channel called Horizon: How Small is the Universe?

Strings or points?

In experiments, teensy, tiny particles like quarks and electrons seem to act like single points of matter with no spatial distribution. But point-like objects complicate the laws of physics. Because you can get infinitely close to a point, the forces acting on it can become infinitely large, and scientists hate infinities.

An idea called superstring theory could solve this issue. The theory posits that all particles, instead of being point-like, are actually little loops of string. Nothing can get infinitely close to a loop of string, because it will always be slightly closer to one part than another. That “loophole” appears to solve some of these problems of infinities, making the idea appealing to physicists. Yet scientists still have no experimental evidence that string theory is correct.

Another way of solving the point problem is to say that space itself isn’t continuous and smooth, but is actually made of discrete pixels, or grains, sometimes referred to as space-time foam. In that case, two particles wouldn’t be able to come infinitely close to each other because they would always have to be separated by the minimum size of a grain of space.

A singularity

Another contender for the title of smallest thing in the universe is the singularity at the center of a black hole. Black holes are formed when matter is condensed in a small enough space that gravity takes over, causing the matter to pull inward and inward, ultimately condensing into a single point of infinite density. At least, according to the current laws of physics.

But most experts don’t think black holes are really infinitely dense. They think this infinity is the product of an inherent conflict between two reigning theories — general relativity and quantum mechanics — and that when a theory of quantum gravity can be formulated, the true nature of black holes will be revealed.

“My guess is that [black hole singularities] are quite a lot smaller than a quark, but I don’t believe they’re of infinite density,” Parker told LiveScience. “Most likely they are maybe a million million times or even more than that smaller than the distances we’ve seen so far.”

That would make singularities roughly the size of superstrings, if they exist.

The Planck length

Superstrings, singularities, and even grains of the universe could all turn out to be about the size of the “Planck length.” [Tiny Grandeur: Stunning Photos of the Very Small]

A Planck length is 1.6 x 10^-35 meters (the number 16 preceded by 34 zeroes and a decimal point) — an incomprehensibly small scale that is implicated in various aspects of physics.

The Planck length is far and away too small for any instrument to measure, but beyond that, it is thought to represent the theoretical limit of the shortest measureable length. According to the uncertainty principle, no instrument should ever be able to measure anything smaller, because at that range, the universe is probabilistic and indeterminate.

This scale is also thought to be the demarcating line between general relativity and quantum mechanics.

“It corresponds to the distance where the gravitational field is so strong that it can start to do things like make black holes out of the energy of the field,” Parker said. “At the Planck length we expect quantum gravity takes over.”

Perhaps all of the universe’s smallest things are roughly the size of the Planck length.

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