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2018年雙子座流星雨 Geminids 2018

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日期 Date 傳媒 Media 分類 Categories 標題 Title
2018-12-05 香港01 hk01 社會新聞 雙子座流星雨14日大爆發 專家憂光污染大減觀賞性 最多只有15顆

雙子座流星雨由2018年12月4日至17日發生,當中12月14日凌晨3時及15日凌晨1時30分左右為香港的最佳觀賞時間!每年平均也有數十個大大小小的流星雨出現,然而觀賞條件受到各種天然及人為因素影響。綜合各種因素,香港大學天文學家根據本港情況推算12月14日凌晨3時及15日凌晨1時30分左右為香港最佳的觀賞時間,在本港視野廣闊和較黑暗的郊區,每小時的可見流星數目約有10至15顆。

The Geminid Meteor Shower, will occur between December 4 and 17, 2018. The observation conditions of the various meteor showers each year depend on a multitude of natural and artificial factors. HKU astronomers have determined that the best time to observe the Geminid Meteor Shower this year in the Hong Kong territory will be around 3:00 am on December 14 and 1:30 am on December 15. There may be 10-15 meteors per hour if you’re watching at a dark rural location with a wide field-of-view during that period.

當地球運行到由彗星或小行星遺留下來的流星體集中區域,便會看到流星像從天空中某一點(「輻射點」)向外散射而出形成流星雨。人們肉眼可以見到的流星數目受眾多因素影響,包括各種天然因素,如觀賞的地理位置、流星雨的活躍程度、高峰期出現的時間、輻射點在天空的位置、月相、雲量和視野等。同時,觀測者的視力和經驗等的人為因素也有相當影響。人為因素當中,觀測地點的光污染程度至為關鍵。

When the Earth sweeps past regions of meteoroids left behind from comets or asteroids, a meteor shower will appear as if it originates from a particular point (the radiant) in the sky. The actual number of meteors observable in the night sky during any particular meteor shower is affected by many factors, including various natural factors such as the geographical location of the observing site and its light pollution condition, the activity of the shower, the peaking time of the meteor shower activities, the location of the radiant point in the sky, moon phase, the amount of cloud in the sky and the field-of-view of the observation location. At the same time, human factors including the observer’s eyesight and experience may also affect what can be seen. In terms of anthropogenic factors, the extent of light pollution in the observing location is of foremost importance in Hong Kong.

雙子座流星雨的「每小時天頂流星數」為120顆,這是個理想化的最高值,假設了觀測者的眼睛完全適應黑暗環境、流星雨的輻射點在天頂、沒有月光影響、觀測地點的天空毫無遮擋及沒有光污染。事實上,這個理想化的最高值,在本港根本不會出現,因為是次流星雨的輻射點並不位於天頂及部分時間有月光影響,即使香港完全沒有光污染,每小時可見流星數目最多只有約45顆。

The Zenithal Hourly Rate (ZHR) for this year’s Geminid Meteor Shower being 120 per hour. This figure is an ideal maximum, which assumes the observer has totally dark-adapted eyes, the radiant is directly up the zenith during the peak hour, and the observing site has an unobstructed field-of-view open without moonlight and light pollution. In fact, this assumed maximum will not realistically take place in Hong Kong. Part of the reason is that the radiant of this shower is not along the zenith direction and the Moon is present over a certain period of time. Therefore even in a location with zero light pollution, the number of meteors observable in Hong Kong will only be around 45.

港大物理系過去十多年來不停收集及追蹤研究本港各區的夜空光度數據及光污染情況,明確顯示本港光污染問題嚴重,令可見的星星和流星數目大幅減少。收集所得的光污染數據讓研究團隊能夠計算出比較貼近現實的可見流星數目。他們利用美國太空總署流星專家Peter Jenniskens博士的模型,根據本港的光污染情況,計算出如本港天氣許可,在視野廣闊及較黑暗的郊區,如西貢天文公園,在12月14日凌晨3時及15日凌晨1時30分左右的可見流星數目才有機會達至10至15顆。至於在本港市區,更可能每小時也看不見一顆流星!整體而言,由於本港光污染嚴重,令本港普遍地區可見流星的數目大幅減少,可見光污染嚴重破壞流星雨的觀賞度。

The HKU Physics Department has been conducting comprehensive research on the light pollution conditions all around Hong Kong for over a decade. Results indicate that light pollution is serious in Hong Kong, and the actual number of meteors observable is closely related to the level of light pollution: the more serious the light pollution is, the smaller the numbers of stars and meteors observable. The measured night sky brightness data collected also allows for more realistic estimates of the number of meteors observable. Based on the meteor shower model of NASA scientist Dr Peter Jenniskens and the light pollution data collected in Hong Kong, if local weather permits, the number of meteors observable from this Geminid Meteor Shower in a dark location with a wide field-of-view, such as the Astropark in Sai Kung, could possibly reach 10-15 per hour during the best observation hours of around 3:00 am on December 14 and 1:30 am on December 15, while the number for an urban site can be no more than 1 per hour during the same period! This implies the severe light pollution in Hong Kong leads to a huge drop of the actual number of meteors observable in most places.

觀賞流星雨秘笈:
- 留意天氣
- 在12月14日凌晨3時或15日凌晨1時30分左右觀賞
- 遠離光污染
- 到視野廣闊的地方
- 無需使用望遠鏡

Tips for viewing the Meteor Shower:
- Pay attention to the weather conditions
- Watch during the best observation hours (around 3:00 am on December 14 and 1:30 am on December 15)
- Stay away from locations with severe light pollution
- Choose a location with a wide field-of-view
- DO NOT use a telescope

觀星禮儀:
- 不要以強光四周照射或使用閃光燈拍照
- 切勿遺留垃圾、騷擾動植物或破壞自然景物
- 使用紅光電筒照明:強光會製造光污染,使人看不見較暗的星星和流星。紅光較不會剌激眼睛,可保持夜視能力,增加看到流星的機會。紅光電筒可以數層紅色玻璃紙、紅布或紅色膠袋覆蓋電筒自製。

Proper stargazing manners:
- DO NOT use powerful lighting or use flash photography
- DO NOT leave behind rubbish, disturb animals and plants, or destroy natural landscapes
- Use torches with red light only: Strong lighting leads to light pollution and makes dimmer stars and meteors less visible. Red light is better because it won’t affect our night vision as much, giving us a better chance to see more meteors. A red light torch can be easily prepared by covering a regular torch by layers of red cellophane, cloth or plastic bag.


2018年雙子座流星雨每小時可見流星數目預測,藍色範圍為較黑郊區(如天文公園)每小時可見數目預測,紅線為一般市區每小時可見數目預測。
Prediction on the number of observable meteors during Geminids 2018. The blue regions show the expected range of meteors per hour in a dark rural location (e.g., Astropark), while the red line represents the expected number in a typical urban location.


觀測地點的光污染程度與2018年雙子座流星雨預測最多每小時可見流星數目的關係。圖中顯示香港時間12月15日凌晨1時30分(其中一段最佳觀賞時間)的流星數目預測,假若香港完全沒有光污染,每小時可見流星數目約有45顆,較黑郊區(如天文公園)約為10至15顆(藍色範圍),一般市區約為0至1顆(紅線)。
The relation between the number of observable meteors during Geminids 2018 and the light pollution condition of observing site. The plot shows the prediction for December 15, 2018 at 1:30 am, one of the best observing times. The number of meteors observable in Hong Kong will be around 45 per hour in a site with no light pollution, but it drops to ~10 – 15 (blue region) for a dark rural location (e.g., Astropark) and further to ~0 – 1 for a typical urban location (red).