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Farabi

Hari Ini jam 10:51:44 AM
Kalo alasan kuota karena jaringan kurang kuat? Kenapa tiap akhir bulan dimana semua orang abis kuota jaringan tidak jadi lebih cepat? Sebenarnya Internet Indonesia lambat lebih karena masalah nyari duit kan?
 

Farabi

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Tarolah setiap gajian orangindonesia beli pulsa.  Berarti ada 10 juta orang yang kuotanya bisa akses internet kecepatan full.  Berarti kekuatan jaringan sebetulnya kuat kan.  Tapi kenapa setelah kuota abis jadi lambat?
 

Farabi

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Apaan nih ganti menkominfo internet kecepatan nya malah ancur bae gini.

Raidahafi27

Pebruari 28, 2015, 07:12:04 AM
departemen tehnik lingkungan banyak menggambar nya ga??

jayanusantaraku

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 >:(

jayanusantaraku

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ada yg tau gk bahan kimia /material pembuat n pembentuk plastik n bagaimana proses campurane/takaran yg pas untuk membuat plastik frame kacamata yg celluloid n thanks ya

jayanusantaraku

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hy saya anggota baru dr kota surabaya n salam kenal n thanks udh d ijinin gabung

abdillahibnunasrullah

Pebruari 24, 2015, 07:53:17 PM
Assalamualaikum, shalom kenal semuanya, ane temennya MuhammadRyan
 

MuhammadRyan

Pebruari 23, 2015, 10:23:33 PM
YAOW, Akhirnya pulang juga dari Haifah, Israel. Ada proyek... bkan soal Mossad...

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salam kenal semuanya, saya anggota baru di sini, mau tanya apakah ada yg tau bagaimana caranya agar daun yang sudah kita petik tetap segar dan tidak menjadi keriput/ menciut ?
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Penulis Topik: Studi Genetik Galaksi  (Dibaca 2811 kali)

0 Anggota dan 1 Pengunjung sedang melihat topik ini.

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Studi Genetik Galaksi
« pada: April 07, 2007, 07:24:07 AM »
Format PDF nya : http://www.aanda.org/images/stories/PressRelease/PRaa200615/praa200615.pdf

Galactic Bulge and Disc Stars Shown To Have Different Oxygen Abundances

Looking in detail at the composition of stars with ESO's VLT, astronomers are providing a fresh look at the history of our home galaxy, the Milky Way. They reveal that the central part of our Galaxy formed not only very quickly but also independently of the rest.

"For the first time, we have clearly established a 'genetic difference' between stars in the disc and the bulge of our Galaxy," said Manuela Zoccali, lead author of the paper presenting the results in the journal Astronomy and Astrophysics. "We infer from this that the bulge must have formed more rapidly than the disc, probably in less than a billion years and when the Universe was still very young."

The Milky Way is a spiral galaxy, having pinwheel-shaped arms of gas, dust, and stars lying in a flattened disc, and extending directly out from a spherical nucleus of stars in the central region. The spherical nucleus is called a bulge, because it bulges out from the disc. While the disc of our Galaxy is made up of stars of all ages, the bulge contains old stars dating from the time the galaxy formed, more than 10 billion years ago. Thus, studying the bulge allows astronomers to know more about how our Galaxy formed.

To do this, an international team of astronomers analysed in detail the chemical composition of 50 giant stars in four different areas of the sky towards the Galactic bulge. They made use of the FLAMES/UVES spectrograph on ESO's Very Large Telescope to obtain high-resolution spectra.

The chemical composition of stars carries the signature of the enrichment processes undergone by the interstellar matter up to the moment of their formation. It depends on the previous history of star formation and can thus be used to infer whether there is a 'genetic link' between different stellar groups. In particular, comparison between the abundance of oxygen and iron in stars is very illustrative. Oxygen is predominantly produced in the explosion of massive, short-lived stars (so-called Type II supernovae), while iron instead originates mostly in Type Ia supernovae [3], which can take much longer to develop. Comparing oxygen with iron abundances therefore gives insight on the star birth rate in the Milky Way's past.

"The larger size and iron-content coverage of our sample allows us to draw much more robust conclusions than were possible until now," said Aurelie Lecureur, from the Paris-Meudon Observatory (France) and co-author of the paper.

The astronomers clearly established that, for a given iron content, stars in the bulge possess more oxygen than their disc counterparts. This highlights a systematic, hereditary difference between bulge and disc stars.

"In other words, bulge stars did not originate in the disc and then migrate inward to build up the bulge but rather formed independently of the disc," said Zoccali. "Moreover, the chemical enrichment of the bulge, and hence its formation timescale, has been faster than that of the disc."

Comparisons with theoretical models indicate that the Galactic bulge must have formed in less than a billion years, most likely through a series of starbursts when the Universe was



 

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