Missing Solar Neutrinos Found

Missing Solar Neutrinos Found

What makes the Sun shine? Where does Earth’s life-sustaining radiation originate? Astronomers answered these questions in part with the discovery of nuclear fusion, the same process that powers the hydrogen bomb.

To test the theory that hydrogen’s fusion into helium powers the Sun, astronomers spent the last thirty years searching for exotic particles dubbed neutrinos, a by-product of the fusion reaction. Once generated, neutrinos stream out and away from the Sun in all directions at nearly the speed of light. Detecting them requires painstaking efforts, but scientists succeeded in doing so. They captured neutrinos in underground detectors,1 only to discover two-thirds of their expected number missing. This “solar neutrino problem” persisted for 30 years, eluding careful experiments until now.2

The problem arose when physicists calculated (using standard equations) that nuclear fusion in the Sun would send 5.1 million neutrinos to every square centimeter of Earth’s surface per second.3 However, observatories designed to detect solar neutrinos found only about 1.7 million neutrinos per cm2 per second.4

No physicist or astronomer, however, really believed that the Sun fell two-thirds short in its neutrino production. So, they altered their hypothesis. The initial hypothesis treated neutrinos as massless particles, but if neutrinos possess a tiny mass, they could “oscillate,” or transform into alternate neutrino “flavors,” namely tau and muon neutrinos. The flow of solar neutrinos arriving at Earth, then, would be split among electron, tau, and muon flavors.

Since neutrino observatories were originally designed to find only electron neutrinos, the detected 1.7 million neutrinos per cm2 per second would actually prove consistent with the revised hypothesis (1.7 is one-third of 5.1). Discoveries made three years ago by two independent teams using different detectors confirmed that neutrinos do indeed oscillate from one flavor into another.5 These discoveries indirectly solved the solar neutrino problem. But researchers hungered for direct proof.

To get it, the Sudbury Neutrino Observatory (SNO) was built in Ontario, Canada. There a collaboration of Canadian, American, and British physicists can use 1,000 tons of heavy water (water molecules in which the hydrogen atoms contain an extra neutron) and for two experiments. The first sensed only electron neutrinos. The second will measure the flux of all three types of neutrinos.

To date, only the first experiment has collected data. However, the team has compared its results with the results of a Japanese experiment dubbed “Super-Kamiokande,” which detected all three varieties of neutrinos.6 The data showed that the so-called missing neutrinos were not really missing after all but had simply converted from electron neutrinos into tau and muon neutrinos. The two studies indicate that solar neutrinos flow at 5.4 ±1.0 million neutrinos cm-2 sec-1, a measurement close enough to resolve the neutrino problem.7

Solving the solar neutrino problem gives astronomers confidence in their understanding of the Sun. The neutrino flux shows physicists how the Sun’s output of light has remained very steady over the last 50,000 years, and will continue to do so for the next 50,000 years—a requirement for human existence.

The solution also affirms the nuclear fusion model for other stars. This confirms that the oldest stars in Earth’s galaxy are about 13 billion years old, as the big bang creation model predicts.

Astronomers and physicists can now state with greater certainty that the Sun is 4.60 billion years old. This age implies that the 4.57-billion-year-old Earth formed relatively quickly. These findings about the Sun—and their implications for life on Earth—powerfully suggest the involvement of a divine designer.

  1. Neutrinos flow quite freely through Earth, just as they stream through the Sun. Experiments to capture them must be carried out deep under Earth’s surface to avoid interfering cosmic radiation. One such laboratory, the Gran Sasso National Laboratory in Italy, operates 3,800 meters underground.
  2. Sudbury Neutrino Observatory home page (www.sno.phy.queensu.ca) contains the first science results, which are described in a technical paper submitted to the Physical Review Letters. Links from this page lead to other articles describing neutrinos, the standard solar model, and the solar neutrino problem in detail.
  3. This occurs when the incidental solar radiation is perpendicular to Earth’s surface. S. Brun, S. Turck-Chieze, and J. P. Zahn, “Standard Solar Models in the Light of New Helioseismic Constraints. II. Mixing Below the Convective Zone,” Astrophysical Journal 525 (1999): 1032-41; John N. Bahcall, M. H. Pinsonneault, and Sarbani Basu, “Solar Models: Current Epoch and Time Dependencies, Neutrinos, and Helioseismological Properties,” Astrophysical Journal 555(2001): 990-1012.
  4. Bruce T. Cleveland, “Measurement of the Solar Electron Neutrino Flux with the Homestake Chlorine Detector,” Astrophysical Journal 496(1998): 505-26; J. N. Abdurashitov et al., “Measurement of the Solar Neutrino Capture Rate with Gallium Metal,” Physical Review C (Nuclear Physics), 60 (1999): id. 055801 (page number converted to hex); Y. Fukuda et al., “Solar Neutrino Data Covering Solar Cycle 22,” Physical Review Letters 77 (1996): 1683-86; J. N. Abdurashitov et al., “Measurement of the Solar Neutrino Capture Rate by SAGE and Implications for Neutrino Oscillations in Vacuum,” Physical Review Letters 83 (1999): 4686-89; W. Hempel et al., “GALLEX Solar Neutrino Observations: Results for GALLEX IV,” Physics Letters B 447 (1999): 127-33; S. Fukuda et al., “Solar 8B and hep Neutrino Measurements from 1258 Days of Super-Kamiokande Data,” Physical Review Letters 86(2001): 5651-55; M. Altmann et al., “GNO Solar Neutrino Observations: Results for GNO I,” Physics Letters B 490 (2000): 16-26.
  5. Andrew Watson, “Case for Neutrino Mass Gathers Weight,” Science 277 (1997): 30-31; Dennis Normile, “Heavy News on Solar Neutrinos,” Science 280 (1998): 1839; Dennis Normile, “Weighing in on Neutrino Mass,” Science 280(1998): 1689-90; Hugh Ross, “Mass Mystery Nearly Solved,” Facts & Faith 11, no. 4 (1997), 6-7; The K2K Collaboration, “Artificial Neutrino Beam Detected After Passing Through 250 km of Earth,” June 28, 1999 press release from K2K (KEK Experiment E362).
  6. S. Fukuda et al., 5651.
  7. Future results from the second SNO detector will carry out a direct measurement of the total neutrino flux with improved precision, thus providing an independent check of the combined results of the first SNO detector and Super-Kamiokande. Q. R. Ahmad et al., “Measurement of Charged Current Interactions Reduced by 8B Solar Neutrinos at the Sudbury Neutrino Observatory,” Physical Review Letters 87 (2001): 71301-5.