作者bitlife (BIT一生)
看板Physics
標題[新聞] NASA's Fermi Catches Thunderstorms Hurling Antimatter...
時間Thu Jan 27 23:07:46 2011
http://www.nasa.gov/mission_pages/GLAST/news/fermi-thunderstorms.html
NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space
01.10.11
Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams
of antimatter produced above thunderstorms on Earth, a phenomenon never seen
before.
Scientists think the antimatter particles were formed in a terrestrial
gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown
to be associated with lightning. It is estimated that about 500 TGFs occur
daily worldwide, but most go undetected.
"These signals are the first direct evidence that thunderstorms make
antimatter particle beams," said Michael Briggs, a member of Fermi's
Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville
(UAH). He presented the findings Monday, during a news briefing at the
American Astronomical Society meeting in Seattle.
NASA's Fermi Gamma-ray Space Telescope has detected beams of antimatter
launched by thunderstorms. Acting like enormous particle accelerators, the
storms can emit gamma-ray flashes, called TGFs, and high-energy electrons and
positrons. Scientists now think that most TGFs produce particle beams and
antimatter. Credit: NASA's Goddard Space Flight Center
Fermi is designed to monitor gamma rays, the highest energy form of light.
When antimatter striking Fermi collides with a particle of normal matter,
both particles immediately are annihilated and transformed into gamma rays.
The GBM has detected gamma rays with energies of 511,000 electron volts, a
signal indicating an electron has met its antimatter counterpart, a positron.
Although Fermi's GBM is designed to observe high-energy events in the
universe, it's also providing valuable insights into this strange phenomenon.
The GBM constantly monitors the entire celestial sky above and the Earth
below. The GBM team has identified 130 TGFs since Fermi's launch in 2008.
"In orbit for less than three years, the Fermi mission has proven to be an
amazing tool to probe the universe. Now we learn that it can discover
mysteries much, much closer to home," said Ilana Harrus, Fermi program
scientist at NASA Headquarters in Washington.
Fermi’s Gamma-ray Burst Monitor detected 130 TGFs from August 2008 to the
end of 2010. Thanks to instrument tweaks, the team has been able to improve
the detection rate to several TGFs per week. (No audio.) Credit: NASA
The spacecraft was located immediately above a thunderstorm for most of the
observed TGFs, but in four cases, storms were far from Fermi. In addition,
lightning-generated radio signals detected by a global monitoring network
indicated the only lightning at the time was hundreds or more miles away.
During one TGF, which occurred on Dec. 14, 2009, Fermi was located over
Egypt. But the active storm was in Zambia, some 2,800 miles to the south. The
distant storm was below Fermi's horizon, so any gamma rays it produced could
not have been detected.
"Even though Fermi couldn't see the storm, the spacecraft nevertheless was
magnetically connected to it," said Joseph Dwyer at the Florida Institute of
Technology in Melbourne, Fla. "The TGF produced high-speed electrons and
positrons, which then rode up Earth's magnetic field to strike the
spacecraft."
The beam continued past Fermi, reached a location, known as a mirror point,
where its motion was reversed, and then hit the spacecraft a second time just
23 milliseconds later. Each time, positrons in the beam collided with
electrons in the spacecraft. The particles annihilated each other, emitting
gamma rays detected by Fermi's GBM.
graphic depicting how Fermi detected a terrestrial gamma-ray flash On Dec.
14, 2009, while NASA's Fermi flew over Egypt, the spacecraft intercepted a
particle beam from a terrestrial gamma-ray flash (TGF) that occurred over its
horizon. Fermi's Gamma-ray Burst Monitor detected the signal of positrons
annihilating on the spacecraft -- not once, but twice. After passing Fermi,
some of the particles reflected off of a magnetic "mirror" point and
returned. Credit: NASA's Goddard Space Flight Center
Scientists long have suspected TGFs arise from the strong electric fields
near the tops of thunderstorms. Under the right conditions, they say, the
field becomes strong enough that it drives an upward avalanche of electrons.
Reaching speeds nearly as fast as light, the high-energy electrons give off
gamma rays when they're deflected by air molecules. Normally, these gamma
rays are detected as a TGF.
But the cascading electrons produce so many gamma rays that they blast
electrons and positrons clear out of the atmosphere. This happens when the
gamma-ray energy transforms into a pair of particles: an electron and a
positron. It's these particles that reach Fermi's orbit.
A TGF produces gamma rays (magenta) as well as high-energy electrons (yellow)
and positrons (green). This simulation tracks a TGF and its particle beams
from their origin altitude of 9.3 miles (15 km) to 373 miles (600 km), beyond
Fermi's orbit. Credit: Joe Dwyer/Florida Inst. of Technology
The detection of positrons shows many high-energy particles are being ejected
from the atmosphere. In fact, scientists now think that all TGFs emit
electron/positron beams. A paper on the findings has been accepted for
publication in Geophysical Research Letters.
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle
physics partnership. It is managed by NASA's Goddard Space Flight Center in
Greenbelt, Md. It was developed in collaboration with the U.S. Department of
Energy, with important contributions from academic institutions and partners
in France, Germany, Italy, Japan, Sweden and the United States.
The GBM Instrument Operations Center is located at the National Space Science
Technology Center in Huntsville, Ala. The team includes a collaboration of
scientists from UAH, NASA's Marshall Space Flight Center in Huntsville, the
Max Planck Institute for Extraterrestrial Physics in Germany and other
institutions.
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◆ From: 118.233.140.102
→ petwing:反物質！？ 01/28 01:51
推 tideecho:暴風雨也有反物質喔? 01/28 03:55
推 HDT:反物質的暴風雨(誤) 01/28 04:25
推 caseypie:真有意思 01/28 04:38
→ MOONRAKER:是的寶賊，一定是外星人偷放到地球造成暴風雨(衰浩平談) 01/28 10:00
→ bitlife:真的是轉台時看到寶杰提到才去 NASA 找到這篇 XD 01/28 10:59
※ 編輯: bitlife 來自: 118.233.140.102 (01/28 11:06)
→ MOONRAKER:哇啦，×鍵時刻居然發揮了科普功能，這到底是好是壞 XD 01/28 17:52
推 light0617:看不太懂耶QQ 01/29 02:08
推 baalism2:反物質的暴風雨地球就爆炸了吧XD 01/29 02:27
→ MOONRAKER:通古斯卡大爆破 喔耶 01/31 12:33
→ bitlife:寶杰的節目現在正在介反物質(資?)狙擊槍 01/31 22:53
→ bitlife:若是真的反物質槍打出去,開槍者能活著離開現場嗎? 01/31 22:54
→ petwing:反物質槍？槍管內的空氣也是物質不是嗎？應該會膛炸吧@@ 02/01 20:06
→ bitlife:暫且假設該子彈用磁場將反物質封閉,擊中目標後磁場破壞 XD 02/01 20:23
→ petwing:覺得這東西做成飛彈還比較可能 如果是子彈 打出去的瞬間 02/01 21:03
→ petwing:磁場裝置若破不了 那撞到目標物的衝量更小 也會破不了 02/01 21:03