2009년 1월 4일 일요일

우주에서 가장 기이한 10가지 현상 [by Dave Mosher]

우주에서 가장 기이한 10가지 현상
TOP 10 STRANGEST THINGS IN THE UNIVERSE

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초고속별, 블랙 홀, 마그네타, 뉴트리노, 암흑 물질, 암흑 에너지, 행성, 중력, 생명체, 우주

미국의 디스커버리 채널이 홈페이지를 통해 올해(2008)의 인기 기사 중 하나로 꼽은 기사는 “우주에서 가장 기이한 10가지 현상”을 요약해 소개한다.

총탄처럼 우주 공간을 뚫고 날아가는 ‘초고속 별’(사진 아래 왼쪽)은 1억 개 별 중 하나 꼴로 발견되는 기이한 우주 현상이다. 2005년 처음 발견된 초고속별은 초속 850km로 보통 별에 비해 10배 빠른 속도를 보였다. 블랙홀이나 초신성의 폭발이 원인이리라 추정된다.

중력 경계로 넘어온 것은 물질이건 빛이건 빨아 들여 절대 빠져나갈 수 없게 하는 블랙홀도 우주의 신비하고도 이상한 현상이다.

엄청나게 강한 자기장을 가진 마그네타는 태양보다 무거운 별이 무너져 내려 약 20km 지름 크기로 줄어들면 탄생한다. 마그네타로부터 수십만 km 떨어져 있어도 신용카드는 망가지고 원자는 극히 얇은 ‘실린더’로 변형된다.

주머니에서 동전을 꺼내 일초 정도 들고 있으면, 뉴트리노라는 작고 거의 질량이 없는 입자가 1천5백억개 정도 그 동전을 뚫고 지나간다. 별, 빅뱅, 핵물질이 그 원천으로 추정되는데 이런 뉴트리노도 우주의 기이한 현상 중 하나이다.

우주의 모든 물질과 에너지들을 모두 모아 파이 차트를 그려보면 놀라운 결과를 알게 된다. 우리가 알고 있는 우주와 별과 행성과 혜성과 운석과 먼지와 가스와 입자들은 천체의 4%에 불과하다. 눈이나 기구에 뵈지 않는 “암흑 물질”이 23%를 차지한다. 73%는 “암흑 에너지”다. 우주의 96%에 해당하는 암흑 물질과 암흑 에너지는 우주과학의 미스터리가 아닐 수 없다. (사진 : 아래 오른쪽은 성단 주위의 암흑 물질을 묘사한 것이다.)

우리가 행성에 살고 있어 익숙할 뿐 행성도 우주의 신비하고 기이한 현상 중 하나다. 별 주위의 가스 및 먼지 디스크들이 어떻게 행성(특히 암석 행성)을 구성하게 되는지 완벽히 설명하는 이론은 아직 없다. 중력도 신비한 현상이다. 우주 모든 곳에 존재하면서도 가장 약한 힘 즉 중력의 원천은 미스터리다.

디스커버리 채널이 선정한 우주의 기이한 현상 10가지 중에서 2위와 1위를 차지한 것은 각각 생명체와 우주 그 자체이다. 물질과 에너지가 우주에 퍼져 있으나 생명체가 생겨나는 드문 일이다. 아직도 생명체를 만드는 “레시피”는 완전히 밝혀지지 않았다.

우주의 최대 미스터리는 에너지와 물질 그리고 우주 자체가 어디에서 생겨났는가 하는 점이다. 빅뱅이 우주의 출발이라고 알려졌으나 그 이전의 시간을 설명하는 것은 불가능하다. 강입자 충돌기가 빅뱅 직후에 형성된 입자를 찾아내면 우주 존재에 대한 진전된 설명이 나올 것이다.

* 아래는 원문 전체
Mysterious Universe - by Dave Mosher
A great article about the top 10 weirdest things in space, on the Discovery Channel website. I couldn't help but be taken in by the beauty of our universe and the countless number of things that are still mysteries. According to the website, here are the Top 10:
  1. Hypervelocity Stars
  2. Black Holes
  3. Magnetars
  4. Neutrinos
  5. Dark Matter
  6. Dark Energy
  7. Planets
  8. Gravity
  9. Life
  10. Universe
출처:http://dsc.discovery.com/space/top-10/strange-universe/space-10-weirdest-things-universe.html

The more we look among the stars and galaxies, the weirder things seem to get.
Even space itself is puzzling, for example. Recent studies suggest that the fabric of the universe stretches more than 150 billion light-years across -- in spite of the fact that the cosmos is 13.7 billion years old.

From super-fast stars to the nature of matter, here we cover other strange and mysterious elements of the universe.


Hypervelocity Stars
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If you've ever gazed at the night sky, you've probably wished upon a shooting star (which are really meteors).

But shooting stars do exist, and they're as rare as one in 100 million.

In 2005, astronomers discovered the first "hypervelocity" star careening out of a galaxy at nearly 530 miles per second (10 times faster than ordinary star movement).

We have ideas about what flings these rare stars into deep space, but aren't certain; anything from off-kilter supernova explosions to supermassive black holes might be responsible.

Caption: Artist's rendition of a hypervelocity star leaving a galaxy. Credit: Harvard-Smithsonian Center for Astrophysics


Black Holes
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Speaking of black holes, what could be stranger?

Beyond a black hole's gravitational border -- or event horizon -- neither matter nor light can escape. Astrophysicists think dying stars about three to 20 times the mass of the sun can form these strange objects. At the center of galaxies, black holes about 10,000 to 18 billion times heavier than the sun are thought to exist, enlarged by gobbling up gas, dust, stars and small black holes.

What about mid-sized types? Perhaps surprisingly, evidence is both scarce and questionable for their existence.

Caption: Conception of a black hole pulling gas off of a nearby star. Credit: ESA/NASA


Magnetars
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The sun spins about once every 25 days, gradually deforming its magnetic field.

Well, imagine a dying star heavier than the sun collapsing into a wad of matter just a dozen miles in diameter.

Like a spinning ballerina pulling his or her arms inward, this change in size spins the neutron star -- and its magnetic field -- out of control.

Calculations show these objects possess temporary magnetic fields about one million billion times stronger than the Earth's. That's powerful enough to destroy your credit card from hundreds of thousands of miles away, and deform atoms into ultra-thin cylinders.

Caption: Artist's rendition of a magnetar with magnetic fields shown. Credit: NASA


Neutrinos
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Pull out a dime from your pocket and hold it up for a second... guess what? About 150 billion tiny, nearly massless particles called neutrinos just passed through it as though it didn't even exist. Scientists have found that they originate in stars (living or exploding), nuclear material and from the Big Bang. The elementary particles come in three "flavors" and, stranger still, seem to disappear on a whim. Because neutrinos occasionally do interact with "normal" matter such as water and mineral oil, scientists hope they can use them as a revolutionary telescope to see beyond parts of the universe obscured by dust and gas.

Caption: Construction of the NuMI neutrino source underway. Credit: BNL


Dark Matter
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If you put all of the energy and matter of the cosmos into a pie and divvy it up, the result is shocking.

All of the galaxies, stars, planets, comets, asteroids, dust, gas and particles account for just 4 percent of the known universe. Most of what we call "matter" -- about 23 percent of the universe -- is invisible to human eyes and instruments.

For now.

Scientists can see dark matter's gravitational tug on stars and galaxies, but are searching feverishly for ways to detect it first-hand. They think particles similar to neutrinos yet far more massive could be the mysterious, unseen stuff.

Caption: False-color depiction of dark matter around a star cluster. Credit: J.-P. Kneib/ESA/NASA


Dark Energy
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What really has everyone on the planet confused -- including scientists -- is dark energy.

To continue with the pie analogy, dark energy is a Garfield-sized portion at 73 percent of the known universe. It seems to pervade all of space and push galaxies farther and farther away from one another at increasingly faster speeds.

Some cosmologists think this expansion will leave the Milky Way galaxy as an "island universe" in a few trillion years with no other galaxies visible.

Others think the rate of expansion will become so great that it will result in a "Big Rip." In this scenario, the force of dark energy overcomes gravity to disassemble stars and planets, the forces keeping particles sticking together, the molecules in those particles, and eventually the atoms and subatomic particles. Thankfully, humankind probably won't be around to witness to cataclysm

Caption: Computer simulation of dark matter filaments. Credit: Science Magazine


Planets
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It might sound strange because we live on one, but planets are some of the more mysterious members of the universe.

So far, no theory can fully explain how disks of gas and dust around stars form planets -- particularly rocky ones.

Not making matters easier is the fact that most of a planet is concealed beneath its surface. Advanced gadgetry can offer clues of what lies beneath, but we have heavily explored only a few planets in the solar system.

Only in 1999 was the first planet outside of our celestial neighborhood detected, and in November 2008 the first bona fide exoplanet images taken.

Caption: Illustration of terrestrial, extrasolar planets. Credit: R. Hurt/NASA/JPL-Caltech


Gravity
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The force that helps stars ignite, planets stay together and objects orbit is one of the most pervasive yet weakest in the cosmos

Scientists have fine-tuned just about every equation and model to describe and predict gravity, yet its source within matter remains a complete and utter mystery.

Some think infinitesimal particles called gravitons exude the force in all matter, but whether or not they could ever be detected is questionable.

Still, a massive hunt is on for major shake-ups in the universe called gravitational waves. If detected (perhaps from a merger of black holes), Albert Einstein's concept that the universe has a "fabric" of spacetime would be on solid ground.

Caption: Artist depiction of gravity waves around merging black holes. Credit: NASA


Life
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Matter and energy abound in the universe, but only in a few places is the roll of the cosmic dice perfect enough to result in life.

The basic ingredients and conditions necessary for this strange phenomenon are better understood than ever before, thanks to abundant access to life here on Earth.

But the exact recipe -- or recipes -- to go from the basic elements of carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur to an organism is a prevailing mystery.

Scientists seek out new areas in the solar system where life could have thrived (or still may, such as below the surface of watery moons), in hopes of arriving at a compelling theory for life's origins.

Caption: E. coli bacteria. Credit: NIH


Universe
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The source of energy, matter and the universe itself is the ultimate mystery of, well, the universe.

Based on a widespread afterglow called the cosmic microwave background (and other evidence), scientists think that the cosmos formed from a "Big Bang" -- an incomprehensible expansion of energy from an ultra-hot, ultra-dense state.

Describing time before the event, however, may be impossible.

Still, atom smasher searches for particles that formed shortly after the Big Bang could shed new light on the universe's mysterious existence -- and make it a bit less strange than it is today.

Caption: Illustration showing the creation and expansion of the universe. Credit: NASA


Article posted October 31, 2008. / discovery.com.

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