 |
|
Astronomers weigh neutrinos with the universe
April 04, 2002Neutrinos, the lightest of the known elementary particles, weigh a billionth (one part in a thousand million) of a hydrogen atom at most, and can account for no more than one-fifth of the dark matter in the Universe, according to findings by astronomers in Cambridge, who used data from the Anglo-Australian telescope 2dF Galaxy Redshift Survey (2dFGRS). The results will be presented by Dr Ofer Lahav of Cambridge University at the UK National Astronomy Meeting in Bristol on Wednesday 10 April.
The findings come from detailed study of the 2dF (two-degree field) Galaxy Redshift Survey, compiled using the Anglo-Australian telescope in New South Wales, Australia. The telescope has created the world`s largest three-dimensional catalogue of galaxies so far, currently consisting of 220,000 galaxies. A team of 30 researchers is analysing the survey to answer fundamental questions about the Universe.
Neutrinos come in three different varieties, and were long thought to have no mass at all, but observations of neutrinos emitted from the Sun and created by cosmic rays in the Earth`s atmosphere have in the last few years revealed that this cannot be the case. A determination of the masses of neutrinos would provide clues about the physics of processes occurring under conditions beyond the reach of current particle physics experiments.
It has long been known that there is more to our Universe than we can see in the starry sky. Indeed, astronomers now know that the visible parts of the Universe, such as stars and galaxies, only constitute a small fraction of its total mass. Neutrinos do not interact with light, and are therefore a candidate for the mysterious invisible dark matter in the Universe. The mass of the neutrinos affects the growth of clumps that evolve into the large structures we observe in the Universe at the present epoch. Since neutrinos are very light, they move at nearly the speed of light over vast regions, smoothing out the clumpiness of the matter.
To study this effect of the tiny neutrinos on the universe, Dr Oystein Elgaroy and Dr Ofer Lahav (both from the Institute of Astronomy, University of Cambridge, UK) together with other 2dFGRS team members, compared the distribution of galaxies mapped out by the 2dFGRS with theoretical calculations of how the matter would be distributed in model universes with different values for the neutrino mass. From this confrontation of theory with observation, they were able to conclude that the neutrinos must have a mass smaller than a billionth of a hydrogen atom. They also concluded that the neutrinos make up less than 20 % of the dark matter in the Universe, and that the rest therefore has to be in some as yet unknown form.
"It is fascinating that we can use enormous structures like galaxies to learn about the properties of the lightest of all the particles in the Universe," says Oystein Elgaroy.
"The dark matter problem has bothered astronomers for over 70 years. If indeed neutrinos have mass, the composition of matter and energy in the universe is even more complicated than the astronomers have so far imagined," says Ofer Lahav.
Recently a group of particle and nuclear physicists announced that they had observed a new type of nuclear decay process involving neutrinos. Their result is still being debated by scientists around the world but, as it stands, it implies that the three neutrinos have very nearly the same mass, and that its value is roughly a few parts in ten billion of the mass of a hydrogen atom.
"Our result from the galaxy survey does not rule out a neutrino mass as deduced from the particle physics experiment," says Oystein Elgaroy. The redshift surveys of millions of galaxies that will be completed in the next few years will set even tighter limits on the mass of the neutrino".
Ofer Lahav adds: "The latest cosmological data suggest that the universe is a mysteriously dark place. It is probably made of four entities, three of them rather exotic: ordinary matter, neutrinos, another form of dark matter which is `cold` and energy (so-called `dark energy` or vacuum energy) represented by the cosmological constant, suggested originally by Einstein".
Royal Astronomical Society (RAS)
It has long been known that there is more to our Universe than we can see in the starry sky. Indeed, astronomers now know that the visible parts of the Universe, such as stars and galaxies, only constitute a small fraction of its total mass. Neutrinos do not interact with light, and are therefore a candidate for the mysterious invisible dark matter in the Universe. The mass of the neutrinos affects the growth of clumps that evolve into the large structures we observe in the Universe at the present epoch. Since neutrinos are very light, they move at nearly the speed of light over vast regions, smoothing out the clumpiness of the matter.
To study this effect of the tiny neutrinos on the universe, Dr Oystein Elgaroy and Dr Ofer Lahav (both from the Institute of Astronomy, University of Cambridge, UK) together with other 2dFGRS team members, compared the distribution of galaxies mapped out by the 2dFGRS with theoretical calculations of how the matter would be distributed in model universes with different values for the neutrino mass. From this confrontation of theory with observation, they were able to conclude that the neutrinos must have a mass smaller than a billionth of a hydrogen atom. They also concluded that the neutrinos make up less than 20 % of the dark matter in the Universe, and that the rest therefore has to be in some as yet unknown form.
"It is fascinating that we can use enormous structures like galaxies to learn about the properties of the lightest of all the particles in the Universe," says Oystein Elgaroy.
"The dark matter problem has bothered astronomers for over 70 years. If indeed neutrinos have mass, the composition of matter and energy in the universe is even more complicated than the astronomers have so far imagined," says Ofer Lahav.
Recently a group of particle and nuclear physicists announced that they had observed a new type of nuclear decay process involving neutrinos. Their result is still being debated by scientists around the world but, as it stands, it implies that the three neutrinos have very nearly the same mass, and that its value is roughly a few parts in ten billion of the mass of a hydrogen atom.
"Our result from the galaxy survey does not rule out a neutrino mass as deduced from the particle physics experiment," says Oystein Elgaroy. The redshift surveys of millions of galaxies that will be completed in the next few years will set even tighter limits on the mass of the neutrino".
Ofer Lahav adds: "The latest cosmological data suggest that the universe is a mysteriously dark place. It is probably made of four entities, three of them rather exotic: ordinary matter, neutrinos, another form of dark matter which is `cold` and energy (so-called `dark energy` or vacuum energy) represented by the cosmological constant, suggested originally by Einstein".
Royal Astronomical Society (RAS)
Galaxies Current Events and Galaxies News RSSWatching a Cannibal Galaxy Dine
A new technique using near-infrared images, obtained with ESO's 3.58-metre New Technology Telescope (NTT), allows astronomers to see through the opaque dust lanes of the giant cannibal galaxy Centaurus A, unveiling its "last meal" in unprecedented detail - a smaller spiral galaxy, currently twisted and warped.
Baffling boxy bulge
When targeting spiral galaxy bulges, astronomers often seek edge-on galaxies, as their bulges are more easily distinguishable from the disc.
Rapid star formation spotted in 'stellar nurseries' of infant galaxies
The Universe's infant galaxies enjoyed rapid growth spurts forming stars like our sun at a rate of up to 50 stars a year, according to scientists at Durham University.
Swift XMM-Newton Satellites Tune Into a Middleweight Black Hole
While astronomers have studied lightweight and heavyweight black holes for decades, the evidence for black holes with intermediate masses has been much harder to come by.
'Dropouts' pinpoint earliest galaxies
Astronomers, conducting the broadest survey to date of galaxies from about 800 million years after the Big Bang, have found 22 early galaxies and confirmed the age of one by its characteristic hydrogen signature at 787 million years post Big Bang.
VERITAS telescopes help solve 100-year-old mystery: The origin of cosmic rays
Nearly 100 years ago, scientists detected the first signs of cosmic rays - subatomic particles (mostly protons) that zip through space at nearly the speed of light.
Iowa State researchers contribute to discovery of gamma rays from starburst galaxy
Iowa State University astrophysicists contributed to the recent discovery that a galaxy quickly creating new stars is also a source of high energy gamma rays.
Starburst galaxy sheds light on longstanding cosmic mystery
An international collaboration that includes scientists from the University of Delaware's Bartol Research Institute in the Department of Physics and Astronomy has discovered very-high-energy gamma rays in the Cigar Galaxy (M82), a bright galaxy filled with exploding stars 12 million light years from Earth.
NASA's Fermi Telescope Detects Gamma-Ray From
Nearby galaxies undergoing a furious pace of star formation also emit lots of gamma rays, say astronomers using NASA's Fermi Gamma-ray Space Telescope.
Shedding light on the cosmic skeleton
"Matter is not distributed uniformly in the Universe," says Masayuki Tanaka from ESO, who led the new study. "In our cosmic vicinity, stars form in galaxies and galaxies usually form groups and clusters of galaxies. The most widely accepted cosmological theories predict that matter also clumps on a larger scale in the so-called 'cosmic web', in which galaxies, embedded in filaments stretching between voids, create a gigantic wispy structure."
More Galaxies Current Events and Galaxies News Articles
 |
Galaxies by Seymour Simon (Author) This close-up look at our own Milky Way and other enormous clusters of stars describes the many different types of galaxies, how they were formed, and how they got their different shapes. "A dazzling photo-essay."--School Library Journal. |
 |
Galaxies in the Universe: An Introduction by Linda S. Sparke (Author), John S. Gallagher III (Author) This extensively illustrated book presents the astrophysics of galaxies since their beginnings in the early Universe. It has been thoroughly revised to take into account the most recent observational data, and recent discoveries such as dark energy. There are new sections on galaxy clusters, gamma ray bursts and supermassive black holes. The authors explore the basic properties of stars and the Milky Way before working out towards nearby galaxies and the distant Universe. They discuss the structures of galaxies and how galaxies have developed, and relate this to the evolution of the Universe. The book also examines ways of observing galaxies across the whole electromagnetic spectrum, and explores dark matter and its gravitational pull on matter and light. This book is self-contained and... |
 |
Galaxies: A Very Short Introduction (Very Short Introductions) by John Gribbin (Author) In this fascinating Very Short Introduction, popular science writer John Gribben tells the story of our growing understanding of galaxies, from the days before Galileo to our present-day observations of our many hundreds of millions of galactic neighbors. Not only are galaxies fascinating astronomical structures in themselves, but their study has revealed much of what we know today about the cosmos, providing a window on the Big Bang and the origins of the Universe. Gribben looks at our own "Milky Way" Galaxy in detail, from the different kinds of stars that are born within it, to the origins of its magnificent spiral structure. Perhaps most interesting, Gribben describes the many exciting discoveries have been made about our own galaxy and about those beyond: how a supermassive black... |
 |
Kid Galaxy Morphibians Shark by Kid Galaxy It's an animal, its a 4x4, it's a speed boat, no it's a Morphibian! This shark is no fish out of water on sand and dirt, powerful four wheel drive, zips it over the water, then even faster on land!These high-performance radio control amphibious creatures can go anywhere- dirt, pond or pool. Features sturdy 4x4 turf digging tires for land and wake forming paddle wheel treads for ripping through the water. Powerful full-function controller makes explorations on any surface just a touch away. Requires 2 "AAA" and 3 "AA" batteries, not included. As with all water related activities, use with close adult supervision. Measures 5" x 5.5" x 7.75". |
 |
GUESS Nadine Top, GALAXY BLUE/TRUE WHITE (M) by GUESS Checkered chic gets a rocker makeover on this fitted top. Snap-up front and snap pockets in true western style. Just slip on your favorite denim and boots and you've got an instant cutting-edge trend. 62% cotton, 34% nylon, 4% spandex Machine wash cold Women > Tops > Long Sleeve |
 |
Galaxies by Kevin Braheny |
 |
Geometry Wars: Galaxies by Sierra Classic arcade fans -- prepare for re-entry! The planet's purest arcade shooter returns with more enemies, bigger power-ups, and a brand-new Battle Drone to help you tear through the first-ever Geometry Wars campaign mode. |
 |
Galaxy Granola Cranberry Orange, 12 Ounce Pouch (Pack of 6) by Galaxy Granola 70% less fat than the others because Galaxy Granola bakes its granola in apple sauce, not oil. Cranberry Orange contains real cranberries and orange peels for a sweet / tart taste experience |
 |
Wausau Paper Astrobrights Colored Card Stock, 65 lb, Letter, Galaxy Gold, 250 Sheets per Pack (22771) by Wausau The brightest colored paper available. Guaranteed performance in laser and ink jet printers. Acid-free. Durable, heavyweight cover ideal for color-coding, menus, posters and more. Global Product Type: Card/Cover Stock; Sheet Size (W x H): 8 1/2 in x 11 in; Paper Color(s): Galaxy Gold™; Paper Weight: 65 lb. |
 |
Galaxies and the Cosmic Frontier by William H. Waller (Author), Paul W. Hodge (Author) For the past twelve billion years, galaxies have governed the Universe, bringing form to the firmament, light to the void. Each one a giant system of as many as hundreds of billions of stars, the galaxies are the building blocks of the cosmos, and through new data from modern telescopes--including the Hubble Space Telescope--we are discovering dizzying new facts about how they formed, how they evolve, and what they are made of. This book acquaints readers with these facts and findings--and with what they can tell us about the lives of galaxies over cosmic time, from their emergence shortly after the Hot Big Bang to their ongoing gyrations and transmutations. Orienting us with an insider's tour of our cosmic home, the Milky Way, William Waller and Paul Hodge then take us on a... |
| © 2009 BrightSurf.com |