Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Neutrino weighed up

11.04.2002


Astronomers use galaxies to reckon a subatomic particle’s mass.


Astronomers surveyed regions outside our Galaxy to estimate neutrino’s mass.
© R. Smith


The spread of galaxies reveals the smoothing effect of invisible neutrinos.



By mapping hundreds of thousands of galaxies, astronomers have estimated the mass of the neutrino. They have also calculated the contribution that this mysterious subatomic particle makes to the total mass of the Universe.

The neutrino weighs no more than one-billionth of the mass of a hydrogen atom, Ofer Lahav of the University of Cambridge told the annual UK National Astronomy Meeting in Bristol today. Yet despite being so small, neutrinos could account for a maximum of about 20% of the mass of the entire Universe.


Lahav and his colleagues deduced the influence of neutrinos by comparing a three-dimensional map of the Universe with the predictions of theoretical physics. "We can use a huge chunk of the Universe to constrain the mass of a tiny particle," says Lahav.

Small but influential

Neutrinos are unimaginably tiny, carry no electrical charge and can pass through planets unperturbed. But their abundance makes them potentially major players in the Universe.

For a long time it was thought that neutrinos had no mass at all. Recent astronomical observations have suggested that they do, but working out the exact figure "is probably one of the hardest questions [in physics]", says theoretical physicist Stephen King of the University of Southampton, UK.

The new estimate "sounds like a reasonable number", King adds. It broadly agrees with, although does not confirm, other figures produced from studies of radioactive decay earlier this year.

One-billionth of a hydrogen atom is towards the lower end of current estimates. If this value stands up, it shows that neutrinos do not exert enough gravitational tug to have much influence over the evolution of the visible Universe, says King. "It’s saying that neutrinos can’t play an important part in galaxy formation."

Revealing wrinkles

Lahav and his colleagues’ conclusion is based on gauging the lumpiness of the Universe. Tiny wrinkles in the Big Bang led to matter forming into gigantic clumps - galaxies, and clusters of galaxies - as the Universe aged.

Yet only about 5% the Universe’s mass is in a visible form. The rest is in a variety of substances known as dark matter, of which neutrinos are one component.

Dark matter is betrayed by its influence on what we can see. Neutrinos, which whizz through space at close to the speed of light, smooth the Universe out by redistributing mass. The heavier neutrinos are, the less clumping we should see in today’s Universe.

Lahav’s team used a three-dimensional map of 160,000 galaxies that they constructed as part of an Anglo-Australian team. They worked out the mass of the neutrino that best fitted the spread of galaxies they saw.

JOHN WHITFIELD | © Nature News Service

More articles from Physics and Astronomy:

nachricht Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen

nachricht New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>