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Post Last Edit by mencacus at 19-6-2011 10:35
Larger-scale structures
Deep sky surveys show that galaxies are often found in relatively close association with other galaxies. Solitary galaxies that have not significantly interacted with another galaxy of comparable mass during the past billion years are relatively scarce. Only about 5% of the galaxies surveyed have been found to be truly isolated; however, these isolated formations may have interacted and even merged with other galaxies in the past, and may still be orbited by smaller, satellite galaxies. Isolated galaxies[note 2] can produce stars at a higher rate than normal, as their gas is not being stripped by other nearby galaxies.[102]
On the largest scale, the universe is continually expanding, resulting in an average increase in the separation between individual galaxies (see Hubble's law). Associations of galaxies can overcome this expansion on a local scale through their mutual gravitational attraction. These associations formed early in the universe, as clumps of dark matter pulled their respective galaxies together. Nearby groups later merged to form larger-scale clusters. This on-going merger process (as well as an influx of infalling gas) heats the inter-galactic gas within a cluster to very high temperatures, reaching 30–100 megakelvins.[103] About 70–80% of the mass in a cluster is in the form of dark matter, with 10–30% consisting of this heated gas and the remaining few percent of the matter in the form of galaxies.
Seyfert's Sextet is an example of a compact galaxy group.
Most galaxies in the universe are gravitationally bound to a number of other galaxies. These form a fractal-like hierarchy of clustered structures, with the smallest such associations being termed groups. A group of galaxies is the most common type of galactic cluster, and these formations contain a majority of the galaxies (as well as most of the baryonic mass) in the universe. To remain gravitationally bound to such a group, each member galaxy must have a sufficiently low velocity to prevent it from escaping (see Virial theorem). If there is insufficient kinetic energy, however, the group may evolve into a smaller number of galaxies through mergers.
Larger structures containing many thousands of galaxies packed into an area a few megaparsecs across are called clusters. Clusters of galaxies are often dominated by a single giant elliptical galaxy, known as the brightest cluster galaxy, which, over time, tidally destroys its satellite galaxies and adds their mass to its own.
Superclusters contain tens of thousands of galaxies, which are found in clusters, groups and sometimes individually. At the supercluster scale, galaxies are arranged into sheets and filaments surrounding vast empty voids. Above this scale, the universe appears to be isotropic and homogeneous.
The Milky Way galaxy is a member of an association named the Local Group, a relatively small group of galaxies that has a diameter of approximately one megaparsec. The Milky Way and the Andromeda Galaxy are the two brightest galaxies within the group; many of the other member galaxies are dwarf companions of these two galaxies. The Local Group itself is a part of a cloud-like structure within the Virgo Supercluster, a large, extended structure of groups and clusters of galaxies centered around the Virgo Cluster.
Sumber : wikipedia |
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Post Last Edit by mencacus at 19-6-2011 10:37
Multi-wavelength observation
After galaxies external to the Milky Way were found to exist, initial observations were made mostly using visible light. The peak radiation of most stars lies here, so the observation of the stars that form galaxies has been a major component of optical astronomy. It is also a favorable portion of the spectrum for observing ionized H II regions, and for examining the distribution of dusty arms.
The dust present in the interstellar medium is opaque to visual light. It is more transparent to far-infrared, which can be used to observe the interior regions of giant molecular clouds and galactic cores in great detail. Infrared is also used to observe distant, red-shifted galaxies that were formed much earlier in the history of the universe. Water vapor and carbon dioxide absorb a number of useful portions of the infrared spectrum, so high-altitude or space-based telescopes are used for infrared astronomy.
The first non-visual study of galaxies, particularly active galaxies, was made using radio frequencies. The atmosphere is nearly transparent to radio between 5 MHz and 30 GHz. (The ionosphere blocks signals below this range.) Large radio interferometers have been used to map the active jets emitted from active nuclei. Radio telescopes can also be used to observe neutral hydrogen (via 21 centimetre radiation), including, potentially, the non-ionized matter in the early universe that later collapsed to form galaxies.
Ultraviolet and X-ray telescopes can observe highly energetic galactic phenomena. An ultraviolet flare was observed when a star in a distant galaxy was torn apart from the tidal forces of a black hole. The distribution of hot gas in galactic clusters can be mapped by X-rays. The existence of super-massive black holes at the cores of galaxies was confirmed through X-ray astronomy
Sumber : wikipedia |
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cant imagine how is it look like during the period before big bang. kiranya semuanya start dgn satu particle yg meletup la?before big bang mmg xde alam ke?lagi difikir boley gilak.. |
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cant imagine how is it look like during the period before big bang. kiranya semuanya start dgn satu ...
mk-sabio Post at 28-5-2011 19:42 
sebelum kejadian big bang pun memang sudah ada alam yang lain iaitu alam akhirat (alam nyata)...... kejadian big bang nie hanya sebesar atom dan membawa letusan yang sungguh dahsyat dengan izin tuhan .......
teori nie pun boleh kita tengok ketika letupan bunga api yang biasa tengok masa hari tahun baru ......
sebenarnya kita berada di alam maya ...... |
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dulu lecturer aku cite..
dalam fizik.. ada ruang dan masa.
sekarang ini kita berada di dalam r ...
testas Post at 24-5-2011 14:39 
teringat cite back to the future |
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aku rasa ada kena mengena dengan kisah manusia ke alam bunian ..... contohnya manusia nie baru ...
mencacus Post at 25-5-2011 23:27 
umur jinn pun boleh tahan lama.... |
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Reply 56# testas
betui tu..kalu bawa keta laju2...jam kat umah lambat..jam kat keta laju..sumtime terlaju sampai ke sorga/neraka  |
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Perkara paling penting saintis kena temui ialah unlimited source of energy.
Lepas kita dah ada unlimited source of energy, baru kita boleh explore semua benda yg baru termasuklah faster than light traveling. |
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umur jinn pun boleh tahan lama....
HangPC2 Post at 1-6-2011 11:00
jin boleh hidup sekitar 500 ke 1000 tahun .... memang lama kalau nak bandingkan dengan manusia yang sekitar 75 tahun .... |
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Reply testas
betui tu..kalu bawa keta laju2...jam kat umah lambat..jam kat keta laju..sum ...
putput Post at 1-6-2011 16:53
dalam maknanya tu ..... |
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Perkara paling penting saintis kena temui ialah unlimited source of energy.
Lepas kita dah ada un ...
MACD Post at 1-6-2011 20:18
awak ada tengok cerita iron man tak ? .... aku ada terfikir tentang energy yang si hero tu cipta untukmeneruskan hayatnya ..... |
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teringat cite back to the future
honeylutfi Post at 30-5-2011 13:36
back to the future tu bagi aku dah advance sangat ..... siap boleh letak tarikh , bulan dan tahun .... |
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kedudukan matahari di galaksi bimq sakti ( milky way ) |
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galaksi andromeda , jiran paling dekat dengan galaksi bima sakti |
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galaksi andromeda , jiran paling dekat dengan galaksi bima sakti
mencacus Post at 3-6-2011 22:28
mase aku study bende nih semue.. mmg aku kagum gile... hebat ciptaan Allah..
aku rase kecik mcm habuk aje manusia nih kalau nak dibandingkan dgn semua tu.. |
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Reply 77# midory
midory dah tengok youtube yang aku tepek tu ? ..... dibandingkan bumi dengan bintang yang terbesar yang pernah direkodkan .... |
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Reply 78# mencacus
dah.. keciknye aku rase.. tahap habuk pon bukan nih.. |
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kita ni (manusia) diibaratkan atom yang berada di dalam atom (bumi) ...... dan bumi pulak umpama atom di dalam galaksi bima sakti .......bima sakti maybe umpama atom di dalam alam semesta ..... besarnya alam nie ...... |
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Category: Belia & Informasi
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Author
Post time 28-5-2011 07:42 PM
