Near-Earth Object Program

http://neo.jpl.nasa.gov/faq/

What Is The Purpose Of The Near-Earth Object Program?

The purpose of the Near-Earth Object Program is to coordinate NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. The NEO Program will focus on the goal of locating at least 90 percent of the estimated 1,000 asteroids and comets that approach the Earth and are larger than 1 kilometer (about 2/3-mile) in diameter, by the end of the next decade. In addition to managing the detection and cataloging of Near-Earth objects, the NEO Program office will be responsible for facilitating communications between the astronomical community and the public should any potentially hazardous objects be discovered.

What Is A Near-Earth Object (NEO)?

Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighborhood. Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system between the orbits of Mars and Jupiter.

What Are The Differences Between An Asteroid, Comet, Meteoroid, Meteor and Meteorite?

In space, a large rocky body in orbit about the Sun is referred to as an asteroid or minor planet whereas much smaller particles in orbit about the Sun are referred to as meteoroids. Once a meteoroid enters the Earth's atmosphere and vaporizes, it becomes a meteor (i.e., shooting star). If a small asteroid or large meteoroid survives its fiery passage through the Earth's atmosphere and lands upon the Earth's surface, it is then called a meteorite. Cometary debris is the source of most small meteoroid particles. Many comets generate meteoroid streams when their icy cometary nuclei pass near the Sun and release the dust particles that were once embedded in the cometary ices. These meteoroid particles then follow in the wake of the parent comet. Collisions between asteroids in space create smaller asteroidal fragments and these fragments are the sources of most meteorites that have struck the Earth's surface.

Because they are readily available for study, many meteorites have already been subjected to detailed chemical and physical analyses in laboratories. If particular asteroids can be identified as the sources for some of the well-studied meteorites, a detailed knowledge of the meteorite's composition and structure will provide important information on the chemical mixture and conditions from which the parent asteroid formed 4.6 billion years ago.

What Is A Potentially Hazardous Asteroid (PHA)?

Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth. Specifically, all asteroids with a minimum orbit intersection distance (MOID) of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less are considered PHAs. In other words, asteroids that can't get any closer to the Earth (i.e. MOID) than 0.05 AU (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 150 m (500 ft) in diameter (i.e. H = 22.0 with assumed albedo of 13%) are not considered PHAs. This ``potential'' to make close Earth approaches does not mean a PHA will impact the Earth. It only means there is a possibility for such a threat. By monitoring these PHAs and updating their orbits as new observations become available, we can better predict the close-approach statistics and thus their Earth-impact threat.

印尼罕見小行星撞地球

鉅亨網新聞中心 (來源：中廣新聞網)

2009 / 10 / 30 星期五 14:42

印尼南蘇拉威西省上空本月8號突傳巨響，一條巨大彎曲狀煙塵橫過天際，引起大批居民恐慌。

科學家經過兩星期調查，確定是直徑10公尺的小行星撞擊大氣層時發生爆炸，釋放的能量等同三顆廣島原子彈。

南蘇拉威西省上空發生爆炸時，當地居民見到一個火球，初傳是撞機，也有專家估計是墜落的太空垃圾。

美國太空總署指出，是小行星以時速約7萬2000公里撞入大氣層所致，釋放的能量大約相當於5萬噸黃色炸藥。

據釋放的能量推算，估計小行星的直徑約10公尺，類似物體約10年撞擊地球1次。

幸運的是，爆炸發生在地球上空15到20公里，地面沒受損。

不過，如果小行星的直徑大到20公尺以上，便有可能造成可怕破壞及人命傷亡。

科學界指出，由於沒有任何天文機構預先發現這顆小行星，令人憂慮地球防衛網薄弱。

在目前的情況下，科學界仍無力追蹤這次出現的小行星。

http://news.cnyes.com/dspnewsS.asp?fi=%5CNEWSBASE%5C20091030%5CWEB1811

http://www.youtube.com/watch?v=yeQBzTkJNhs&videos=jkRJgbXY-90

直徑僅7米 最近地小行星:與地球 "親密接觸"

2009年11月11日 08:07

來源：騰訊科技 悠悠/編譯

    據英國每日郵報報道，上週五，一顆小行星與地球“親密接觸”，距離地球最近距離僅有14000公里（8700英里），然而之前相關天文機構並未發現這顆小行星會接近地球，直到它抵達近日點15小時前才發現。 與地球和月球之間的距離402335公里（25萬英里）相比，這顆小行星與地球的距離僅是地月距離的三十分之一。據悉，這顆小行星的直徑僅有7米（23英尺），地球平均每年兩次與類似大小的小行星近距離接觸，平均每隔5年會有一顆類似大小的小行星碰撞其表面。 　　

     天文學家認為這顆被命名為“2009 VA”的小行星在進入地球大氣層時，差不多已完全燃燒，至多在天空中形成一個明亮的火球，並不會對地球表面構成較大的威脅。 　　

     2009 VA小行星是卡特琳娜太空勘測中心於11月6日發現的，之後美國馬薩諸薩州小行星研究中心將它定義為近地天體（near Earth object）。美國宇航局近地天體計劃署繪製了這顆小行星的運行軌跡，並確定雖然它非常接近地球，卻並不會發生碰撞。

     這是迄今為止所探測到的第3顆最近距離接近地球的未碰撞小行星，目前美國宇航局近地天體計劃署的工作任務是在2020年之前對接近地球90%直徑大於0.96公里（0.6英里）的1000顆小行星和彗星進行監控跟蹤。 　　

     今年3月2日，天文學家探測到了一顆直徑為30.5米（100英尺）的小行星距離地球僅有72418公里（45000英里），類似大小的一顆小行星于1908年碰撞在前蘇聯西伯利亞通古斯地區，此次碰撞釀成1931平方公里（1200平方英里）的森林火災。

（責任編輯：單曉冰）

http://big5.ce.cn/gate/big5/sci.ce.cn/yzdq/yz/yzxw/200911/11/t20091111_20391226.shtml

http://neo.jpl.nasa.gov/news/news166.html

末日救地球！俄射太空船撞小行星

2009年12月31日10:43

俄羅斯聯邦宇航局負責人安東利－珀明諾維（Anatoly Perminov）稱，俄宇航局將不久召開會議討論“阿波菲斯”小行星，致力於避免地球末日的出現。

他在接受新聞媒體採訪時表示，一旦會議討論議題確立，他將邀請美國宇航局、歐洲宇航局和中國航空部共同參與這項太空計劃。

這一消息可能會讓美國宇航局感到有些驚訝，之前美國宇航局曾認為這顆885英呎直徑的小行星於2029年碰撞地球的概率很低，僅為1：37，甚至可以接近不與地球發生碰撞。

美國宇航局預測“阿波菲斯”小行星將“和平地”與地球擦肩而過，之間的最近距離不會達到1.8萬英里。

同時，這顆小行星于2035年再次碰撞地球的可能性也非常低，預計碰撞概率為1：45000分至1：250000。

但珀明諾維卻認為“阿波菲斯”小行星具有潛在威脅，他說：“人類的生活將處于危險之中，我們應該花費數千萬美元建造一個能夠避免碰撞的防禦系統，而不是坐以待斃，等待這場災難讓數以萬計的居民喪生。”

在此之前，科學家們曾提出過一些小行星偏離軌道的策略，有人提議發射探測器在這顆危險的小行星的周圍盤旋，試著改變它的運行軌道；

還有人認為發射一個宇宙飛船與小行星發生碰撞，將改變它朝向地球運行的方向；或者使用核武器炸毀它。

目前，珀明諾維並未表明該項計劃的詳細信息，只是表示相應的防禦性計劃需要進一步商榷，但他明確不會使用任何核武器炸燬這顆小行星。（悠悠/編譯）

http://news.sina.com.hk/cgi-bin/nw/show.cgi/1/1/1/1378897/1.html

新發現一顆小行星明日將與地球擦肩而過

中央社 (2010-01-13 07:43)

一顆最新發現的小行星正向地球方向飛來，並將於美國時間星期三與地球近距離擦肩而過這顆小行星是從現在起到2024年間已知的最靠近地球的天體。 　　

新浪科技訊 北京時間1月13日消息，據美國《連線》雜誌網站報導，一顆最新發現的小行星正向地球方向飛來，並將於美國時間星期三與地球近距離擦肩而過，兩者之間的最近距離僅為地月距離的三分之一。

這顆小行星是從現在起到2024年間已知的最靠近地球的天體。 　　

這顆最新發現的小行星被命名為『2010 AL30』，直徑大約為30英尺到50英尺(約合9米到15米)。

『2010 AL30』是由美國宇航局資金贊助的林肯近地小行星研究中心首先發現的，美國史密松天文物理台小行星中心于當地時間周一宣布了這一發現。

在2024年，將有一顆名為『2007 XB23』、相近大小的天體飛越地球。 　　

從『2010 AL30』被發現，到它與地球以最近距離擦肩而過，兩者之間時間相隔如此之短，這意味著人類並不能夠預測和掌握所有可能危害地球外太空或與地球相撞的天體。

美國阿肯色州天文台科學家克雷-舍爾羅德博士通過在線論壇介紹說，『許多訪問者不斷地問我，我是否會擔心我所測量到的近地天體。

我的回覆是，「我並不擔心這些我們已經掌握的天體。

我更關心的是那些正在向我們飛來，但我們卻沒有觀測到的天體。」』 　　

如果想了解這顆小行星與地球的距離究竟有多近，你可以下載由澳地利天文學家傑拉德-唐格爾所製作的『小行星接近地球』動畫片段(下載位址為：http://www.dangl.at/2010/2010_al30/2010_al30.avi)。 　　

需要指出的是，這顆小行星體積較小，即使闖入地球大氣層，也不會造成太大的災難。它極有可能在落到地面之前就已經在大氣層中燃燒殆盡。

此外，『2010 AL30』與地球的距離也比『阿波菲斯』與地球的距離要遠三倍以上。

小行星『阿波菲斯』也是最近討論比較多的一顆近地天體。

據了解，『阿波菲斯』將有可能於2029年與地球相撞。

http://news.sina.com.tw/article/20100113/2677504.html

如果撞埋o黎地球真係 Die Hard~!唯有到時候希望外星人出手救救!

以地球文明科技不足以自救!

咁又未必, 射幾個核彈上去就搞掂啦!!! 

呢單嘢令我諗起《千年女王》, 松本零士寫呢個故事嘅時候大大低估咗核武嘅威力, 我仲記得八十年代有紀錄片提過, 如果將當時嘅核彈一鑊過引爆, 足以毁滅九個半地球!!! 彌生你死得好冤枉呀!!!

無錯係可以o甘...但得回來的結果是地球大受幅射影響破壞...到時一樣 Die Hard!

所以要更高o既外星科技解救!

我都幾信有八成可能真係有飛碟救地球.

近年睇DISCOVERY CHANNEL 話射飛彈炸殞石都有危險性, 就係炸唔哂, 變成更多舊飛落來都一樣玩完.

最佳方法係想辦法令到殞石移位改變軋道..

我都有睇過...有人提出用太陽光集速射向殞石令它發熱從而推離軋道.

承你貴言.

理論上可以, 但仍未實踐到.

送一隻人造衛星物體上太空, 然後用太陽光反射過去令殞石改變軌道.

但有個問題出現, 唔射殞石....改為射向地球, 咁咪變成另一種大殺傷力武器?

一物二用...合經濟原則. 睇吓邊個射上去先 la.

我睇過紀錄片講個地面實驗....好勁幾秒已經將成吋厚鋼板溶了. 成了武器一定強勁. 殺傷力一定好大.

 當你有力量時你會點用...刀可以殺人也可救人你會點用在你有力量之後先知....朋友.

咁咪仲勁過「高熱火燄」!!!???

難怪到而家都冇人開發戰鬥機械人, 睇怕呢家嘢只會永遠活在漫畫家嘅世界!!!

類似列根時代講既星球大戰計劃吧?

根時代講既星球大戰計劃是用導彈為主同主旨在兇蘇聯...不過今次主旨是救世同能源 ...嗱目的是乜見仁見智.

睇深一層我地現時所享受的科技大多由軍事上演變而成. 咁乜都兩面睇.

兇到蘇聯自己摺埋.

太陽能激光炮?

Lasers to beam energy to Earth from space

Solar energy collected in space and beamed back to Earth by laser could soon be used to power homes and electric vehicles under a project by European space engineers.

By Richard Gray, Science Correspondent
Published: 8:30PM GMT 23 Jan 2010

It sounds more like a scheme dreamed up by a James Bond villain attempting to destroy the Earth than a technology that could help provide a solution to the planet's dwindling energy supplies.

Engineers plan to put satellites into orbit around the planet that can gather energy from the sun, concentrate it into powerful laser beams and transmit the energy back to the Earth where it can be used to generate electricity.

While harvesting solar energy in space has been discussed by scientists for more than 30 years, engineers at EADS Astrium, Europe's largest space company, now believe the technology is available to allow them to start building a working prototype.

They hope to have a small demonstrator of a full sized space-based power station, capable of beaming back 10-20kW of power, ready for launch in the next five years.

Using a network of these solar power stations it would be possible to provide energy on demand 24 hours a day – something that is not possible with solar power on the planet's surface which can only produce energy during the hours of sunlight.

"There is a global need for increased energy generation that does not have an environmental impact," explained Matthew Perren, head of innovation at Astrium's headquarters in Paris.

"The real advantage of space solar power is that it can provide power on demand as we can essentially point the laser beam where ever we like on the earth below the orbit.

"Looking to the future we envisage large power stations in space that are capable of transmitting energy to any point in the planet on demand."

Space-based solar power, although more expensive than using solar panels on Earth, is attractive because of its capability to provide a clean, inexhaustible power supply around the clock.

Much of the power of the sun is filtered out by the Earth's atmosphere while clouds and the inability to produce power at night have all limited the use of solar power as an energy source.

In space, however, the sun's rays are far more powerful and even with a relatively inefficient conversion process, could still produce large amounts of power. Most importantly, satellites can be positioned so they are exposed to sunlight for far longer than sites on Earth.

The space power stations would be launched into a geostationary orbit, which means they remain above the same point above the planet, around 22,300 miles above the surface.

With solar panels more than 50 metres across, they would be able to gather large amounts of energy from the sun which would then be converted into a infrared laser beam to be transmitted back to Earth.

One of the key uses of the technology could be to power a new generation of large electric vehicles such as cargo ships and tankers. The satellites could be made to move the laser beam to track the ships as they move across the ocean, providing a constant energy supply.

Scientists at Astrium have already begun work on developing the technology needed to turn a laser beam into movable source of electricity. They have managed to use lasers in the laboratory to power toy cars.

Astrium hopes to work with international space agencies, governments and power companies to develop a network of space based power stations that will eventually be capable of supplying enough energy to power hundreds of thousands of homes.

But it is not the only firm working in the field. In September Japan announced a $21 billion plan to send solar panel equipped satellite into space that could beam enough power back to Earth to supply 300,000 homes.

California has also made a deal with a company called Solaren to design satellites that would beam power back down from solar powered satellites.

But Astrium claims that its approach of using infrared lasers will make the system safer than other proposals which have suggested using microwaves to transmit the energy. If misdirected, microwaves could cause widespread damage, effectively cooking anything in their path.

Such schemes are reminiscent of far fetched plots in James Bond movies such as Die Another Day, where villain Gustav Graves builds a space based laser that he can control as a weapon, and Diamonds are Forever, where Ernst Stavro Blofeld attempts to hold the world to ransom with a laser in space.

Astrium, however, insist that the infrared laser, which is typically used in laser guidance systems for the military, will be safe. As it is beyond the visible spectrum of the human eye, it would also not be harmful to eyesight should anyone look into the beam.

Mr Perren said: "We are concentrating on developing something that is safe. While the laser beam will have some heat in it, we intend for it to be safe for people to walk through unaffected.

"Much of the technology we need has already been tried and tested in existing satellites and spacecraft, but there are technical difficulties that still need to be overcome such as improving the efficiency of converting the energy and increasing the power of the laser we can build.

"It is important to remember that we are not looking to take the place of power stations on Earth, but to provide another piece of the puzzle in finding alternative energy sources."

http://www.telegraph.co.uk/earth/energy/solarpower/7060015/Lasers-to-beam-energy-to-Earth-from-space.html