Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Princeton scientists confirm long-held theory about source of sunshine

22.08.2007
Scientists are a step closer to understanding sunshine. A monumental experiment buried deep beneath the mountains of Italy has provided Princeton physicists with a clearer understanding of the sun's heart -- and of a mysterious class of subatomic particles born there.

The researchers, working as part of an international collaboration at the underground Gran Sasso National Laboratory near L'Aquila, Italy, have made the first real-time observation of low-energy solar neutrinos, which are fundamental particles created by nuclear reactions that stream in vast numbers from the sun's core.

"Our observations essentially confirm that we understand how the sun shines," said Frank Calaprice, a professor of physics and principal investigator of the Princeton team. "Physicists have had theories regarding the nuclear reactions within the sun for years, but direct observations have remained elusive. Now we understand these reactions much better."

The scientists' precise measurements of the neutrinos' energy provide long-sought proof of the theory regarding how these neutrinos are produced.

In stars the size of the sun, most solar energy is produced by a complex chain of nuclear reactions that converts hydrogen into helium. Beginning with protons from hydrogen's nucleus, the chain takes one of several routes that all end with the creation of a helium nucleus and the production of sunlight.

Steps along two of these routes require the presence of the element beryllium, and physicists have theorized that these steps are responsible for creating about 10 percent of the sun's neutrinos. But technological limitations had made the theory difficult to test until now.

The Gran Sasso lab's giant Borexino detector, located more than a kilometer below the Earth's surface, overcame these limitations, permitting the team to observe low-energy neutrinos, which interact extremely rarely with other forms of matter. Scientists have desired a way to detect them, because they emerge largely unchanged from their journey through the sun's interior to the Earth -- offering an unsullied glimpse into the processes that forged them. Most particles that emerge from the sun take so long to escape the interior that they change drastically before scientists can study them, so it has been difficult to prove how the sun creates energy. Neutrinos provide a key because they escape before they have time to change.

"The findings show that science's understanding of the chain of nuclear processes that make the sun shine is essentially correct, as least as far as the part of the chain that involves beryllium is concerned," Calaprice said. "The reaction does not generate a large percentage of the sun's energy, but confirming that we understand it makes us more certain that we know how the other processes that create sunlight work."

The results address other longstanding questions as well. The highly sensitive detector has confirmed theories regarding why previous experiments had found fewer solar neutrinos than expected at higher energies, a problem that stemmed from the particles' odd capacity to oscillate from one form to another as they travel through space. While the sun only produces electron neutrinos, these can change into tau or muon neutrinos, which have proved more difficult to detect.

Observing lower-energy neutrinos may also help physicists understand other predicted effects of neutrino oscillation that have not yet been tested.

"This experiment is an important step along the way toward understanding the details of neutrino physics using neutrinos from the sun," said physicist Morgan Wascko, co-spokesman for SciBooNE neutrino experiment at Fermi National Accelerator Laboratory. "Using these particles to observe the sun is important because they give us a lot of information about the way the universe functions, because it's full of stars."

The Borexino experiment's entire research team, which includes more than 100 scientists from many institutions worldwide, will publish its findings in an upcoming edition of the scientific journal Physics Letters B. Calaprice's Princeton colleagues include Cristiano Galbiati, assistant professor of physics, and Jay Benziger, professor of chemical engineering.

The experiment is funded by the National Science Foundation.

Abstract:
First real time detection of 7Be solar neutrinos by Borexino
This paper reports a direct measurement of the 7Be solar neutrino signal rate performed with the Borexino low background liquid scintillator detector. This is the first real-time spectral measurement of sub-MeV solar neutrinos. The result for 0.862 MeV 7Be is 47 ± 7stat ± 12sys counts/(day · 100 ton), consistent with predictions of Standard Solar Models and neutrino oscillations with LMA-MSW parameters.

Chad Boutin | EurekAlert!
Further information:
http://www.princeton.edu

More articles from Physics and Astronomy:

nachricht Researchers discover link between magnetic field strength and temperature
21.08.2018 | American Institute of Physics

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

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: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>