Night
Sky Over Gemini North 北雙子天文台的夜空 (8/6/2003)
你認識多少個大型天文台？香港天文台...？唔...今次就原諒你，下次就不要再這樣回答了。香港那個「台」，做的是氣象觀測，不是一所做天文研究的天文台，只是歷史原因錯叫它為天文台那麼多年，確實覺得有它有需要改名。氣象跟天文的分野是很大的，觀測預報天氣的是氣象台的工作，而天文台是夜觀天象（或日觀太陽）的地方。世界上的大型天文台其實不多，因為要有好的選址，建天文台才有意義。地球上，最多大型天文台雲集的地方，就是夏威夷的Mauna
Kea，其中之一正是圖中的是北雙子天文台。若果你細心看，你可以看到圖中的銀河的。
Caption::
Hong Kong Observatory is an meteorolgical observatory instead of an astronmical
one. There aren't many big observatory in this world, as a good location
is vital for doing observation for astronomers. Mauna Kea of Hawaii contains
the most big observatory of the world, this one, Gemini North is also
located there. If you are careful enough, you can spot the milky way in
the photo.
Credit::
Gemini
Observatory
|
Pencil
Nebula 鉛筆星雲 (7/6/2003)
一張由哈勃太空望遠鏡拍回來的新照片，這個叫鉛筆星雲的地方，其實是船帆座超新星爆炸殘骸的其中一部份。之前介紹過幾種星雲，包括了恆星出生地的星際雲、行星狀星雲，今次這個也是一個星雲，但它屬於另一種類別－－超新星爆炸殘骸。這個跟行星狀星雲有點類似，但這個是直接由恆星死亡時的爆炸而留下來的星雲，而非由恆星拋出的氣殼所形成的。
Caption::
Remnants from a star that exploded thousands of years ago created a celestial
abstract portrait, as captured in this NASA Hubble Space Telescope image
of the Pencil Nebula. Officially known as NGC 2736, the Pencil Nebula
is part of the huge Vela supernova remnant, located in the southern constellation
Vela. Discovered by Sir John Herschel in the 1840s, the nebula's linear
appearance triggered its popular name. The nebula's shape suggests that
it is part of the supernova shock wave that recently encountered a region
of dense gas. It is this interaction that causes the nebula to glow, appearing
like a rippled sheet.
Credit::
NASA
and The Hubble Heritage Team (STScI/AURA)
|
Dumbbell
Nebula 啞鈴星雲 (6/6/2003)
啞鈴星雲，M27，是另一個行星狀星雲。當恆星開始年老，內部的核燃料用得七七八八時，它的表面就會開始向外膨脹，拋出氣殼。到那顆恆星死亡時，之前拋出的氣殼已經變得很大了，這個氣殼就是行星狀星雲了。至於為什麼叫行星，這是因為很久以前人們覺得這類星雲看上去跟行星很似，所以得到了這個名。
Caption::
When normal nuclear fusion stops in a Sun-like star, the balance between
the contracting force of gravity and the expansion pressure of internal,
hot gas is upset. The consequence is the ejection of the star's outer
layers into space. The exposed core of the star, a white dwarf, emits
intense ultraviolet light that ionizes the ejected gas and causes the
colorful emission seen here. The planetary nebula phase is relatively
short, only twenty thousand years or so as the ejected material is recycled
back into the interstellar medium of the galaxy.
Credit::
Jean-Charles
Cuillandre and CFHT
|
Wolves
on Snow 雪地上的群狼 (5/6/2003)
日落時份，長長的影投在白茫茫的雪地上，除此之外，還有其他東西在雪地上。你看到右下方那一個個的小黑點嗎？那是什麼？牠們是一隻隻的狼。狼是群居的動物，但有時卻會給人一種孤高的感覺。
Caption::
Wolves wandering across Minnesota's great white north have fared far better
than their cousins elsewhere, partly because thick forest and the lack
of roads barred trappers. With packs flourishing, problems arise, such
as a growing incidence of wolves killing livestock and domestic dogs.
Credit::
Joel
Sartore
|
Hercules
Cluster 武仙座星團 (4/6/2003)
你覺得這裏有多少粒星？一千？錯。一萬？都錯。係三十萬！這天體就叫做星團，而這種有那麼多星聚在一起的稱為球狀星團，一般的球狀星團都有十多萬顆恆星，越靠近中心，恆星就越密集。相中的是武仙座星團，又稱M13，是梅西爾星表中的第13個成員，肉眼都可以見到的，是一個很靚的球狀星團。
Caption::
Globular clusters are relatively compact groups of stars orbiting around
galaxies. They contain hundreds of thousands of stars bound together by
their mutual gravitational attraction. They are believed to be some of
the oldest stellar systems in the Universe. This one (Messier 13) lies
in the nearby halo of our galaxy at a distance of approximately 23000
light years. It can be found in the Hercules constellation.
Credit::
Jean-Charles
Cuillandre and CFHT
|
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