怎样观测星期六的小行星!!8月17-18号

怎样观测星期六的小行星
作者：By Roger W. Sinnott
翻译：姚京辉
   8月17-18号，星期六晚上。一个最近发现的的小行星将在近距离穿过地球。你可以非常容易的用小望远镜或双筒镜观测到它。设在麻萨诸塞州剑桥大学中的小行星中心计算的最新结果显示，小行星飞行轨迹最近将离地球527000千米（327000英里）。刚好在月亮轨道距离的外面一点。
   天文学家7月14日在美国新墨西哥州使用一米口径的LINEAR望远镜发现了着颗星体，并命名为2002NY40。星体出现在几乎固定的西方宝瓶座，当时仅仅19等，小行星朝向地球在一定范围内有规律的逐渐变亮。在这个星期，它快速的靠近。着颗小行星开始逐渐加速的穿过西北方向的天空。
   根据亮度的判断，这个闯入者粗略估计为500米（0.3英里）直径。但是经过by Lenka Sarounova (Czech Republic), Sergio Foglia (Italy), and David DeGraff, William Holliday, and Walter Cooney (USA) 的精细光度测定已经显示了它有个不规则的外形。利用他们的资料，Petr Pravec (Ondrejov Observatory) 发现了2002NY40以20小时/圈的速度在旋转和更多数量的改变！光度曲线显示小行星的两个轴的大小比率是2：1。Praveec在8月9日向小行星邮件列表（Minor Planet Mailing List）做了报告。
   几乎在发现小行星的同时，天文学家做出了2002NY40不会在接近地球的飞行过程中给地球带来危险。数据增加到,由两个NEODyS 由比萨大学管理由美国国家航空和宇宙航行局在短时间制定在即将来临的世纪将与地球冲撞的物体列表中。但是这个遭遇过程为地球基础天文学家提供了这个短暂的，罕见的研究如此近距离的小行星的机会。

                               
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原文！：：
How to Watch Saturday's Asteroid Flyby
By Roger W. Sinnott

 
For help in locating asteroid 2002 NY40 on August 17–18, Sky & Telescope has prepared four (PDF) finder charts (see page 2). S&T: Roger Sinnott and Steven Simpson.


 
 
On Saturday night, August 17–18, a recently discovered asteroid will pass close enough to Earth to be easily spotted in small telescopes or even binoculars. The latest calculations by the Minor Planet Center in Cambridge, Massachusetts, indicate the flyby will bring it to within 527,000 kilometers (327,000 miles) of Earth, just outside the Moon抯 orbital distance.
Astronomers first detected this object, designated 2002 NY40, on July 14th with the 1-meter LINEAR telescope in New Mexico. It was then only 19th magnitude and appeared nearly stationary in western Aquarius, brightening steadily on an in-bound path toward Earth. Finally this week, with the flyby fast approaching, the asteroid began moving northwest at an ever-increasing rate.

Judging by its brightness, this interloper is roughly 500 meters (0.3 mile) across. But detailed photometry by Lenka Sarounova (Czech Republic), Sergio Foglia (Italy), and David DeGraff, William Holliday, and Walter Cooney (USA) already shows it to have an irregular shape. Using their observations, Petr Pravec (Ondrejov Observatory) finds that 2002 NY40 rotates in 20 hours and varies by more than a magnitude. The light-curve amplitude 搃ndicates that the asteroid is an elongated object with an equatorial-axis ratio greater than 2:1,?Pravec reported to the Minor Planet Mailing List August 9th.

Almost immediately after its discovery in July, astronomers determined that there was no danger of 2002 NY40 striking Earth during this flyby. In addition, both NEODyS, operated by the University of Pisa, and NASA抯 Near-Earth Object Program quickly ruled out an impact during the coming century. But the encounter affords Earth-based astronomers a rare chance to study an asteroid at very close range, however briefly.

用望远镜看看。

现在它的亮度是多少呢？

看到需要运气与条件！

在那里，怎样观测!!!请看这里！！
   在星期六的晚上，8月17-18号，2002NY40在欧洲、美洲、非洲观察将达到10等或9等。虽然它能达到双筒望远镜所能观测的亮度，但是小口径望远镜能给你的的只是更多的满意的星体运动轨迹。观测者能够看到小行星在背景星空中随着时间而改变位置。当18日7：47（格林尼治时间）分小行星经过近地点时你能看到它向东运行8分钟。
   为了帮助小行星的定位，“天空与望远镜”准备了4幅60平方度范围的星图，从天箭星座穿过狐狸座、天鹅座、天琴座、武仙座。每一个图表都是pdf格式的文件，你可以在任何计算机上使用Adobe公司Acrobat Readerhttp://www.adobe.com/products/acrobat/readstep2.html的3.0译本软件查看，还可以打印出来。
图表一 大体上是在欧洲、非洲的观测者使用。 在17日的20：00到18日的01：30。http://skyandtelescope.com/graphics/ChartA.pdf
图表二 包含的星空与轨迹适合北美洲的观测者。从1：30到4：30http://skyandtelescope.com/graphics/ChartB.pdf
图表三 显示了小行星的轨迹。适合在4：10到6：10在美国波士顿和洛山矶观测。
图表四 适合在北美的观测者 结束在7：40

因为视差的影响，小行星的精确轨迹按照你的地理位置。留下几个常见的几个大城市的上空星体运行的图纸，你可以按照你自己的地理位置估计小行星在空中运行的位置。
（例如在美国丹佛上空的轨迹应该在波士顿和洛山矶的中间，或者就在附近。）小行星必须在上升到黑夜中的地平线上10度以上才能较准确的定位。我们的计划是按照小行星中心8月11号得到的天文测量数据制定的。每一个数据都是很准确的！但小行星在前进的过程中与计划总是有1到2分钟的差别的。
   为了更好的观察这个小行星，更好的观察它的细节你应该制定详细的计划。你应该提前10分钟将你的望远镜对准它将出现的位置等待。如果你错过了，你应该找另外一个更远的点再次寻找。
   考虑它在你的视野中在星空中是很暗的，但它在小望远镜中仍然是很容易看到的。起码有24小时的时间你能够观测它，可是它会跑到相对地基望远镜上空即很靠近太阳的哪个方向。


原文：Where and How to Look

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When the asteroid is closest to Earth at around 7:47 UT on the 18th, it will be traveling eastward at a breezy 8 arcminutes per minute!
 

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On the night of Saturday, August 17–18, 2002 NY40 should reach magnitude 10 or even 9 during the period when it is well placed for viewing from Europe, Africa, and the Americas. Although it might be spotted in binoculars, small telescopes should give a more satisfying view by magnifying the object抯 apparent motion. Skywatchers should be able to perceive this motion any time it glides near a background star. When the asteroid is closest to Earth at around 7:47 Universal Time on the 18th, it will be traveling eastward at a breezy 8 arcminutes per minute!

For help in locating the asteroid that night, Sky & Telescope has prepared four finder charts (A, B, C, and D) that span a 60° arc across the heavens from Sagitta through Vulpecula, Cygnus, Lyra, and Hercules. Each chart is a PDF file; these are readable on any computer using Adobe's free Acrobat Reader software, version 3.0 or later, and can be printed out for use at the telescope.

Chart A is mainly of use to observers in Europe and Africa, with tracks plotted for the period 20:00 UT (on the 17th) to 01:30 UT on the 18th.

Chart B includes the start of tracks suitable for North American viewers, plotted from 1:30 to 4:30 UT.

Chart C shows the continuation of the asteroid抯 path as viewed from Boston and Los Angeles between 4:10 and 6:10 UT.

Chart D shows the the final portion of the track for North American viewers and concludes at 7:40 UT.

Because of the parallax effect, the asteroid抯 exact trajectory depends on your geographical location. Tracks for several widely separated cities are shown, and you can estimate the track for your own location relative to those shown. (For example, the track for Denver would lie between the tracks shown for Boston and Los Angeles, somewhat nearer the latter.) Each plotted track covers only the period when the asteroid is at least 10° above the horizon in a fully dark sky at that location. Our plots are based on astrometric measurements received by the Minor Planet Center through August 11th. Each individual track should be quite reliable, but the object抯 arrival time at a specific point along a track is still uncertain by 1 or 2 minutes.

To catch sight of this fleet visitor, the best strategy is to pick out a star near which the asteroid will pass at a specific UT. About 10 minutes in advance, park your telescope on that star and watch for the asteroid to come by. If you miss it, find another plotted star farther down the track and try again.

Keep in mind that the asteroid will be slightly fainter than the stars shown in our plots, yet still quite easy to see in a small telescope. A mere 24 hours after it goes by, however, the object will plunge hopelessly beyond reach of Earth-based telescopes as it heads closer to the Sun. (We will then be viewing its unilluminated side, which explains why it becomes so faint, so fast.)

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