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Wednesday, December 8, 2010

Tipe - Tipe Galaksi

Dengan mempergunakan teleskop 250 cm di Observatorium Mount Palomar, astronom Edwin Hubble (1924) memotret sebuah galaksi di rasi Andromeda. Dia menjelaskan, untuk ertama kalinya, bentuk galaksi yang kemudian terkenal dengan nama galaksi Andromeda, berjarak 2 juta tahun cahaya dari galaksi kita (Bimasakti/Milkyway). Galaksi Andromeda merupakan galaksi luar (extra galaxy) pertama yang diketahui astronom. Sejak penemuannya, banyak studi dilakukan dalam mempelajari galaksi-galaksi di luar galaksi Bimasakti tempat kita berada.

Upaya para astronom mempelajari galaksi melalui pengamatan semenjak abad ke-18, telah melahirkan berbagai katalog benda-benda langit yang meliputi gugusan bintang termasuk didalamnya adalah galaksi. Pada tahun 1888, J.L.E. Dreyer mempublikasikan New General Catalogue of nebulae and Clusters of Stars yang memuat 7840 obyek langit. Katalog ini dilengkapi dengan suplemennya, Index Catalogues pada tahun 1895 dan 1908. Umumnya katalog tersebut mempergunakan notasi NGC atau IC diikuti dengan nomor obyek dalam daftar. Sebagai contoh, galaksi Andro-meda diberi nomor katalogus NGC 224.

Ada banyak galaksi-galaksi dengan berbagai ragam bentuknya. Hubble mengklasifikasikan galaksi-galaksi berdasarkan bentuknya ke dalam 3 kelompok utama, yakni:

1. Galaksi spiral (S)
Populasi galaksi berbentuk spiral ini yang terbanyak (80%). Galaksi ini memiliki struktur yang paling teratur dengan pusat, selubung bulat dan piringan dengan lengan spiral yang mengelilingi ekuator galaksi. Variasi dari galaksi spiral adalah galaksi spiral berbatang (SB), dengan bentuk cerutu yang melintasi pusat dan di kedua ujungnya pola spiral menjuntai.

2. Galaksi eliptik (E)
Galaksi dengan bentuk ini meliputi 17% dari seluruh populasi galaksi di alam semesta. Bentuknya lebih sederhana dibandingkan dengan galaksi spiral, karena hanya terdiri dari pusat dan selubung pipih. Kerapatan bintang lebih tinggi di pusat dibanding di tepiannya.

3. Galaksi tidak beraturan
Sebanyak 3% dari galaksi yang teramati sejauh ini menunjukkan bentuk yang tidak beraturan. Bentuknya lebih merupakan onggokan bintang dengan batas yang kurang jelas. Berbagai contoh nyata galaksi ini antara lain Awan Magellan kecil dan besar, tetangga galaksi kita, Bima Sakti.
Pola galaksi yang dirangkum dan diklasifikasikan oleh Hubble ditafsirkannya sebagai perjalanan evolusi galaksi di alam semesta dari bentuk yang awalnya sangat teratur menuju bentuk yang tidak beraturan.

Sunday, November 21, 2010

Soal - soal Latihan

1. Bulan memerlukan waktu paling tidak 2 menit untuk terbit dilihat dari Bumi. Berapa lama Bumi memerlukan waktu untuk terbit dilihat oleh seorang pengamat dari Bulan?
a. 2 menit
b. 4 menit
c. 6 menit
d. 8 menit
e. Bumi tidak terbit dan tidak tenggelam

2. On the sunlit side of the Moon the sky appears …
A. white because of the extreme brilliance of the sunlight
B. black because the Earth blocks the light
C. blue due to the Moons' atmosphere
D. black because the Moon lacks an atmosphere
E. black because the Moon has a dense atmosphere

3. You are adrift at sea, and you see a star directly overhead. You remember from your astronomy lab at N.C. State that this star has a declination of 42 degrees South, and a Right Ascension of 8 hours. From this information alone, you know that …
A) You are adrift at a point north latitude 42 degrees.
B) You are adrift at a point south latitude 42 degrees.
C) You are adrift at a point west longitude 8 degrees.
D) You are adrift at a point south latitude 48 degrees.
E) A and C

4. If you lived on the Moon, would the motion of the planets appear any different than from Earth?
A. The motion of the planets would not appear significantly different than on the Earth.
B. The planets would not appear to go around the Moon.
C. The planets would not appear to go around the Earth.
D. The planets would not appear to go around the Sun.
E. None of the above

5. You are carried away by an alien spacecraft to a different star planetary system. You are set down on a planet with cloudless skies. After some time, you notice five planets in the sky. Three retrograde after greatest eastern elongation with the "sun"; two at opposition. From this observation, you infer that, in a heliocentric model, you are on the _____ planet outward from the "sun".
A. first
B. second
C. third
D. fourth
E. fifth

6. When Venus sets after sunset …
a. Venus is west of the sun
b. Venus is east of the sun
c. Venus could be either east or west of the sun depending on the month.
d. it is a mistake because Venus never sets after sunset
e. it must be moving retrograde

7. Pernyataan tentang gerak planet yang tepat adalah ...
A. Planet Venus mungkin saja terlihat saat tengah malam
B. Planet Jupiter tidak mungkin tertutup oleh bulan Purnama
C. Planet Mars selalu nampak berdekatan dengan Matahari
D. Planet Merkurius tidak mungkin nampak melintas di depan piringan Matahari
E. Planet Saturnus bisa mengalami gerak retrogade

8. Peristiwa yang tidak tepat berhubungan dengan pengamat yang ada tepat di kutub utara adalah ...
A. Matahari paling tinggi ada di 23,50 di atas horizon
B. Pada bulan Desember, Matahari tidak terbit
C. Semua arah adalah arah selatan
D. Bisa mengamati rasi Centaurus di bulan-bulan tertentu
E. Bintang Polaris menjadi bintang sirkumpolar

Selamat Belajar

Monday, November 8, 2010

Solar System

A couple videos related to the solar system:






Source: youtube

Tuesday, November 2, 2010

Latihan Soal: Gerak Benda Langit

1. Tentukan perbandingan gaya pasang surut antara Bumi-Bulan dan Bumi-Matahari bila diketahui jarak pusat ke pusat antara Bumi-Matahari 400 kali jarak pusat ke pusat Bumi-Bulan, diameter Bumi 4 kali diameter Bulan, dan massa Bumi 80 kali massa Bulan!

2. Sebuah satelit mempunyai orbit polar dengan ketinggian 5,49 x 10^6 m di atas permukaan Bumi. Setelah melewati di atas London, tentukan posisi satelit saat menyelesaikan satu kali orbit!

3. Mengapa objek langit yang besar (misalkan Matahari, Bintang, Planet, dll) bentuknya mendekati bola sedangkan objek langit yang relatif kecil (misalkan Asteroid, Komet, dll) bentuknya irregular?

4. Certain neutron stars are believed to be rotating at about 1 revolution/second. If such a star has a radius of 20 km, what must be its minimum mass so that material on its surface remains in place during the rapid rotation?

5. Planet imajiner mempunyai jarak rata-rata 120 satuan astronomi dari matahari. Berapa lama waktu yang diperlukan planet ini untuk mengorbit matahari? Berapa periode sinodisnya?


Selamat Belajar.

Friday, September 24, 2010

Introducing Lomba Rancang Pabrik Tingkat Nasional

Memperkenalkan website www.lrptn.com sebagai sumber informasi bagi acara Lomba rancang Pabrik Tingkat Nasional.



Sekilas mengenai LRPTN (Source: www.lrptn.com)

Perkembangan industri kimia saat ini tidak lepas dari kemampuan dan kreativitas para insinyurnya, yang selalu memberikan ide-ide baru sehingga dapat memenuhi kebutuhan masyarakat. Kecakapan seorang insinyur tentunya tidak diperoleh secara instan, namun perlu dibentuk semenjak duduk di bangku kuliah. Untuk meningkatkan kemampuan dan kreativitas para calon insinyur teknik kimia, Himpunan Mahasiswa Teknik Kimia (HIMATEK) ITB bekerjasama dengan Program Studi Teknik Kimia ITB mengadakan Lomba Rancang Pabrik Tingkat Nasional (LRPTN). LRPTN merupakan sebuah kompetisi rancang pabrik yang mengangkat tema-tema yang berkaitan dengan isu-isu aktual dalam dunia industri. Sampai sekarang, LRPTN telah berhasil diselenggarakan sebanyak 11 kali sejak tahun 1996.

LRPTN yang pertama kali diadakan diikuti oleh 8 kelompok peserta dari berbagai perguruan tinggi di Indonesia dengan dewan juri terpillih, yang memiliki kompetensi dalam menilai rancangan suatu pabrik dari sudut pandang keilmuan, khususnya Teknik Kimia. Rangkaian acara LRPTN diisi oleh pembicara-pembicara yang secara khusus diundang untuk berbagi pengetahuan dan pengalaman menarik mereka berkaitan dengan tema dari tiap LRPTN. Semenjak LRPTN IV pada tahun 2000, kompetisi ini dikategorikan menjadi 2, yaitu kategori perancangan pabrik dan problem solving. Kategori perancangan pabrik ini dilombakan dengan pembatasan berdasarkan subtema utama dari LRPTN, sedangkan untuk kategori problem solving dilombakan untuk memfasilitasi ide-ide solutif dan inovatif dari mahasiswa dalam memecahkan masalah nyata yang sedang terjadi dalam suatu pabrik tertentu.

Selanjutnya, pada LRPTN V yang diselenggarakan pada tahun 2001, kategori LRPTN diubah menjadi 3 kategori, yaitu Lomba Rancang Pabrik Kategori A, Lomba Rancang Pabrik Kategori B, dan problem solving. “ Format kompetisi LRPTN dengan 3 kategori tersebut dianggap mampu memfasilitasi ide-ide solutif dan inovatif dari mahasiswa sehingga penyelenggaraan LRPTN berikutnya, mulai dari LRPTN VII hingga LRPTN XI mengikuti format yang hampir sama dengan LRPTN V. Banyak pihak memandang LRPTN merupakan suatu kegiatan yang memberi dampak positif bagi perkembangan mahasiswa Teknik Kimia di Indonesia dalam meningkatkan kemampuan aplikatif mahasiswa dalam melakukan suatu pra rancangan pabrik. Hal ini ditunjukkan dengan peningkatan jumlah peserta yang turut bergabung untuk mengikuti LRPTN ini tiap tahunnya.

Penyelenggaraan LRPTN diharapkan dapat menjadi suatu wadah berkarya bagi mahasiswa se-Indonesia dalam lingkup keilmuan Teknik Kimia. Selain itu, LRPTN ini juga diharapkan dapat memberikan kontribusi nyata bagi perkembangan industri nasional.

Friday, May 7, 2010

Hubble 20 years of Space-Shattering Discoveries

A nice video from NASA to celebrate 20 years of Hubble Telescope.



Source: youtube.com

Soal Latihan Astronomi Dasar

Silakan mencoba beberapa latihan soal Astronomi.

1. If you measure the parallax of a star to be 0,5 arc seconds on Earth and an observer in a space station in the orbit around the Sun measures a parallax for the same star to be 1 arc seconds, how far is the space station from the Sun ?

2. Sebuah galaksi yang berada pada jarak d Mpc dari kita. Tunjukkan bahwa pada galaksi ini, bentangan 1” di langit berkorespondensi dengan bentangan fisik 5d parsec!

3. Para ahli menggunakan sinar laser untuk menentukan jarak dari Bumi ke planet Venus. Sinar laser ditembakkan ke arah planet Venus , lalu para ahli mengukur selang waktu antara penembakkan sinar laser dengan pantulan yang diterima oleh detektor tertentu. Jika didapat selang waktunya adalah 4,32178 menit. Hitunglah jarak planet Venus dari Bumi !

4. Teleskop di Bumi mempunyai kemampuan memisahkan objek (resolving power) sebesar 0”,1. Berapakah ukuran kawah minimum yang dapat diamati di permukaan Mars ?

5. You observe an asteroid approaching the Earth. You have two observatories 3200 km apart, so you can measure the parallax shift of the incoming asteroid. You observe the parallax shift to be 0,022 degrees.
a) How big is the parallax shift in radians ?
b) How far away is the asteroid ?

Selamat belajar.

Sunday, March 14, 2010

Sekilas Tentang Badai Matahari

Matahari adalah sumber dari semua energi yang kita kenal di Bumi. Jika kita merunut semua sumber energi yang kita kenal dan kita gunakan sehari-hari, semuanya akan bermuara pada Matahari. Matahari sendiri menghasilkan energi lewat reaksi nuklir yang terjadi di pusatnya. Namun, meski Matahari memegang peran penting sebagai sumber energi yang kita butuhkan, Matahari juga menyimpan potensi yang bisa memberikan ancaman bagi manusia dan ekosistem Bumi. Ancaman yang dimaksud adalah peristiwa yang dikenal dengan nama badai matahari.

Gambar 1. Struktur Matahari

Sebelum membicarakan tentang badai matahari, kita akan melihat sekilas tentang Matahari. Matahari adalah sebuah bintang, yaitu bola plasma panas yang ditopang oleh gaya gravitasi. Di pusat Matahari (nomor 1 dalam Gambar 1), terjadi reaksi nuklir (fusi) yang mengubah 4 atom hidrogen menjadi 1 atom helium. Reaksi fusi tersebut, selain menghasilkan helium, juga menghasilkan energi dalam jumlah melimpah (ingat persamaan terkenal oleh Einstein: E=mc2). Energi yang dihasilkan, di pancarkan keluar melewati bagian-bagian Matahari, yaitu: zona radiatif (nomor 2), zona konventif (nomor 3), dan bagian atmosfer Matahari, yang terdiri dari fotosfer (nomor 4), kromosfer (nomor 5), dan korona (nomor 6). Dan badai Matahari adalah peristiwa yang berkaitan dengan bagian atmosfer Matahari tersebut.

Bagian terluar dari Matahari, yaitu korona, memiliki temperatur yang mencapai jutaan kelvin. Dengan temparatur yang tinggi tersebut, materi yang berada di korona Matahari memiliki energi kinetik yang besar. Tarikan gravitasi Matahari tidak cukup kuat untuk mempertahankan materi korona yang memiliki energi kinetik yang besar itu dan secara terus menerus, partikel bermuatan yang berasal dari korona, akan lepas keluar angkasa. Aliran partikel ini dikenal dengan nama angin matahari, yang terutama terdiri dari elektron dan proton dengan energi sekitar 1 keV. Setiap tahunnya, sebanyak 1012 ton materi korona lepas menjadi angin matahari, yang bergerak dengan kecepatan antara 200-700 km/s.

Berbeda dengan pusat Matahari yang relatif sederhana, bagian atmosfer Matahari relatif lebih rumit. Karena di atmosfer Matahari ini, medan magnetik Matahari berperan besar terhadap berbagai peristiwa yang terjadi di dalamnya. Ada berbagai fenomena menarik diamati di atmosfer Matahari berkaitan dengan medan magnetik Matahari, seperti bintik matahari (sun spot), ledakan Matahari (solar flare), prominensa, dan pelontaran material korona (CME – Coronal Mass Ejection). Hal-hal inilah yang berkaitan dengan badai matahari.

Jadi apa yang dimaksud dengan badai matahari?

Singkatnya, badai matahari adalah kejadian/event dimana aktivitas Matahari berinteraksi dengan medan magnetik Bumi. Badai matahari ini berkaitan langsung dengan peristiwa solar flare dan CME. Kedua hal itulah yang menyebabkan terjadinya badai matahari.

Solar flare adalah ledakan di Matahari akibat terbukanya salah satu kumparan medan magnet permukaan Matahari. Ledakan ini melepaskan partikel berenergi tinggi dan radiasi elektromagnetik pada panjang gelombang sinar-x dan sinar gamma. Partikel berenergi tinggi yang dilepaskan oleh peristiwa solar flare, jika mengarah ke Bumi, akan mencapai Bumi dalam waktu 1-2 hari. Sedangkan radiasi elektromagnetik energi tingginya, akan mencapai Bumi dalam waktu hanya sekitar 8 menit.

Lalu bagaimana dengan CME?

CME adalah pelepasan material dari korona yang teramati sebagai letupan yang menyembur dari permukaan Matahari. Dalam semburan material korona ini, sekitar 2×1011 – 4×1013 kilogram material dilontarkan dengan energi sebesar 1022 – 6×1024 joule. Material ini dilontarkan dengan kecepatan mulai dari 20 km/s sampai 2000 km/s, dengan rata-rata kecepatan 350 km/s. Untuk mencapai Bumi, dibutuhkan waktu 1-3 hari.

Matahari kita memiliki siklus keaktifan dengan periode sekitar 11 tahun. Siklus keaktifan ini berkaitan dengan pembalikan kutub magnetik di permukaan Matahari. Keaktifan Matahari ini bisa dilihat dari jumlah bintik matahari yang teramati. Saat keaktifan Matahari mencapai maksimum, kita akan mengamati bintik matahari dalam jumlah paling banyak di permukaan Matahari dan pada saat keaktifan Matahari mencapai maksimum inilah, angin matahari lebih ‘kencang’ dari biasanya dan partikel-partikel yang dipancarkan juga lebih energetik. Dan peristiwa solar flare dan CME dalam skala besar juga lebih dimungkinkan untuk terjadi. Dengan kata lain, saat keaktifan Matahari mencapai maksimum, Bumi akan lebih banyak dipapar dengan partikel-partikel bermuatan tinggi (lebih tinggi dari biasanya) dan radiasi elektromagnetik energi tinggi.

Partikel-partikel bermuatan yang dipancarkan dari peristiwa solar flare dan CME, saat mencapai Bumi, akan berinteraksi dengan medan magnetik Bumi. Interaksi ini akan menyebabkan gangguan pada medan magnetik Bumi buat sementara.

Saat partikel-partikel bermuatan dengan energi tinggi mencapai Bumi, ia akan diarahkan oleh medan magnetik Bumi, untuk bergerak sesuai dengan garis-garis medan magnetik Bumi, menuju ke arah kutub utara dan kutub selatan magnetik Bumi. Saat partikel-partikel energetik tersebut berbenturan dengan partikel udara dalam atmosfer Bumi, ia akan menyebabkan partikel udara (terutama nitrogen) terionisasi. Bagi kita yang berada di permukaan Bumi, yang kita amati adalah bentuk seperti tirai-tirai cahaya warna-warni di langit, yang dikenal dengan nama aurora. Aurora ini bisa diamati dari posisi lintang tinggi di sekitar kutub magnetik Bumi (utara dan selatan).

Gambar 2. Aurora

Saat terjadi badai matahari, partikel-partikel energetik tadi tidak hanya menghasilkan aurora yang indah yang bisa di amati di lintang tinggi. Tapi bisa memberikan dampak yang relatif lebih besar dan lebih berbahaya. Dampak yang dimaksud antara lain: gangguan pada jaringan listrik karena transformator dalam jaringan listrik akan mengalami kelebihan muatan, gangguan telekomunikasi (merusak satelit, menyebabkan black-out frekuensi HF radio, dll), navigasi, dan menyebabkan korosi pada jaringan pipa bawah tanah.

Peristiwa gangguan besar yang disebabkan oleh badai matahari, yang paling terkenal adalah peristiwa tahun 1859, peristiwa yang dikenal dengan nama Carrington Event. Saat itu, jaringan komunikasi telegraf masih relatif baru tapi sudah luas digunakan. Ketika terjadi badai Matahari tahun 1859, jaringan telegraf seluruh Amerika dan Eropa mati total. Aurora yang biasanya hanya bisa diamati di lintang tinggi, saat itu bahkan bisa diamati sampai di equator.

Masih ada beberapa contoh peristiwa lain yang berkaitan dengan badai matahari yang terjadi dalam abad ke-20 dan 21:

  1. 13 maret 1989: Terjadi CME besar 4 hari sebelumnya. Badai geomagnetik menghasilkan arus listrik induksi eksesif hingga ribuan ampere pada sistem interkoneksi kelistrikan Ontario Hydro (Canada). Arus induksi eksesif ini menyebabkan sejumlah trafo terbakar. Akibat dari terbakarnya trafo tsb, jaringan listrik di seluruh Quebec (Canada) putus selama 9 jam. Guncangan magnetik badai sekitar seperempat Carrington event, (sekitar 400 nT). Aurora teramati sampai di Texas
  2. Januari 1994 : 2 buah satelit komunikasi Anik milik Canada rusak akibat digempur elektron-elektron energetik dari Matahari. Satu satelit bisa segera pulih dalam waktu beberapa jam, namun satelit lainnya baru bisa dipulihkan 6 bulan kemudian.
    Total kerugian akibat lumpuhnya satelit ini disebut mencapai US $ 50 – 70 juta.
  3. November 2003 : Mengganggu kinerja instrumen WAAS berbasis GPS milik FAA AS selama 30 jam.
  4. Januari 2005: Berpotensi mengakibatkan black-out di frekuensi HF radio pesawat, sehingga penerbangan United Airlines 26 terpaksa dialihkan menghindari rute polar (kutub) yang biasa dilaluinya.

Badai Matahari juga bisa berbahaya bagi makhluk hidup secara biologi. Bahaya ini terutama bagi para astronot yang kebetulan sedang berada di luar angkasa saat badai matahari terjadi. Bagi kita yang berada di permukaan Bumi, kita relatif aman terlindungi oleh medan magnetik Bumi. Pengaruh langsung dari badai matahari ini hanya dialami oleh binatang-binatang yang peka terhadap medan magnetik Bumi. Karena badai matahari mengganggu medan magnetik Bumi, maka binatang-binatang yang peka terhadap medan magnetik akan secara langsung terimbas. Misalnya burung-burung, lumba-lumba, dan paus, yang menggunakan medan magnetik Bumi untuk menentukan arah, untuk sesaat ketika badai matahari terjadi, mereka akan kehilangan arah.

Saat ini, Matahari sedang menuju puncak keaktifan dalam siklusnya yang ke-24. Puncak keaktifan Matahari ini diperkirakan terjadi sekitar tahun 2011-2013. Saat puncak keaktifan Matahari pada siklus ke-24 ini, diperkirakan tidak akan jauh berbeda dengan saat puncak keaktifan pada siklus-siklus sebelumnya. Mungkin efeknya akan sedikit lebih besar, tapi ada juga yang menduga akan terjadi hal yang sebaliknya, justru lebih kecil efeknya. Yang manapun itu kasusnya, bisa dikatakan semua ahli fisika matahari sepakat tidak mungkin terjadi peristiwa besar yang akan membahayakan kehidupan di muka Bumi.

Berdasarkan pengetahuan kita saat ini, badai matahari hanya akan memberikan ancaman bahaya yang rendah. Solar flare dan CME yang terjadi di Matahari, tidak akan cukup untuk menyebabkan peristiwa seperti yang digambarkan dalam beberapa film yang beredar belakangan ini. Beberapa bintang yang diamati memang menunjukkan adanya peristiwa yang dikenal dengan istilah superflare, yaitu flare seperti yang kita amati di Matahari tapi dengan intensitas yang jauh lebih besar. Tapi peristiwa serupa diduga bukan peristiwa yang umum dan diragukan bakal terjadi pada Matahari kita, setidaknya saat ini. Memang peristiwa solar flare dan CME belum bisa diprediksi dengan baik untuk saat ini. Tapi pengetahuan kita yang didapat dari pengamatan Matahari lewat berbagai observatorium landas-bumi dan wahana antariksa yang terus menerus mengamati Matahari, kita semakin mengerti berbagai peristiwa yang terjadi di Matahari. Setidaknya untuk saat ini, kita bisa mengatakan dengan cukup yakin bahwa yang digambarkan dalam film-film fiksi ilmiah (misalnya: film 2012) tentang badai raksasa matahari, tidak akan terjadi dalam waktu dekat.

Seiring dengan perkembangan teknologi elektronika, serta kaitannya dengan iklim, studi tentang aktivitas matahari menjadi perhatian yang semakin perlu dikaji. Bisakah kita memprediksi badai matahari? Dinamika siklusnya? Dinamika cuaca antariksa yang di dorong dinamika matahari? Pengamatan matahari saat ini telah menggunakan teknologi satelit dalam menentukan bilamanakah terjadi aktivitas yang tiba-tiba dari matahari.

SOHO (Solar Heliospheric Observatory), diluncurkan untuk terus menerus memonitor matahari; ACE (Advance Composition Explorer), mengamati perubahan lingkungan antariksa dan memberikan peringatan adanya badai matahari, satu jam sebelum mencapai bumi. WIND yang mengawasi angin matahari yang terjadi pada ruang antar planet sekitar bumi, atau IMAGE (Imager for Magnetopause-to-Auroral Global Exploration) mengamati partikel bermuatan dan atom netral disekitar magnetosfer. Kesemuanya itu digunakan untuk memahami fenomena yang terjadi pada matahari dan keterkaitannya dengan lingkungan bumi. Tetapi pemahaman yang lebih baik lagi akan diperoleh jika kita bisa memahami bagaimana dinamika yang sesungguhnya terjadi jauh di dalam matahari, dan mendorong terjadinya dinamika yang teramati. Dan dengan dukungan pengamatan yang semakin baik, kajian yang semakin mendalam mendorong semakin berkembangnya studi bidang astronomi, khusunya astrofisika bintang/matahari. (Gambar dari SOHO ditampilkan pula di dalam blog ini, di bagian kanan)

Sumber: www.langitselatan.com

Tuesday, March 2, 2010

Soal - soal latihan astronomi 2

Silakan mencoba kedua soal di bawah ini. Soal-soal ini merupakan soal olimpiade astronomi siswa di India.

1. Jayshree claimed that she saw a solar eclipse when the size of the solar disk was 26and that of the lunar disk was 30. She also claimed that at the time of the maximum eclipse, distance between the centres of the two disks was 7. Qualitatively show that she could not have observed a total eclipse. Find the percentage of the solar disk covered at the time of the maximum eclipse.

2. A year in Solar calendar consist of 365.25 days and the same in Lunar calendar consist of 354 days. The additional days in Solar calendar are kept as balance every year. Whenever the number of balance days exceeds 30, an additional month of 30 days is added to the lunar year to offset the difference. The cycle goes on. Anwesh, whose birthday falls on 1st January, noticed that in the year 2008, his birthday coincided with the start of the lunar year. In which earliest future year, his birthday will again coincide with the start of the lunar year?


Solusinya dapat di download di sini

Tuesday, February 9, 2010

Where did today’s spiral galaxies come from?


Hubble shows that the beautiful spirals galaxies of the modern Universe were the ugly ducklings of six billion years ago.

If confirmed, the finding highlights the importance to many galaxies of collisions and mergers in the recent past. It also provides clues for the unique status of our own galaxy, the Milky Way. Using data from the NASA/ESA Hubble Space Telescope, astronomers have created a census of galaxy types and shapes from a time before Earth and the Sun existed, up to the present day. The results show that, contrary to contemporary thought, more than half of the present-day spiral galaxies had peculiar shapes as recently as 6 billion years ago.


The study of the shapes and formation of galaxies, known as morphology, is a critical and much-debated topic in astronomy. An important tool for this is the ‘Hubble sequence’ or the ‘Hubble tuning-fork diagram’, a classification scheme invented in 1926 by the same Edwin Hubble in whose honour the space telescope is named.

Hubble’s scheme divides regular galaxies into three broad classes — ellipticals, lenticulars and spirals — based on their visual appearance. A fourth class contains galaxies with an irregular appearance.

A team of European astronomers led by François Hammer of the Observatoire de Paris has, for the first time, completed a census of galaxy types at two different points in the Universe’s history — in effect, creating two Hubble sequences — that help explain how galaxies form. In this survey, researchers sampled 116 local galaxies and 148 distant galaxies.

The astronomers show that the Hubble sequence six billion years ago was very different from the one that astronomers see today. “Six billion years ago, there were many more peculiar galaxies than now – a very surprising result,” says Rodney Delgado-Serrano, lead author of the related paper recently published in Astronomy & Astrophysics. “This means that in the last six billion years, these peculiar galaxies must have become normal spirals, giving us a more dramatic picture of the recent Universe than we had before.” The astronomers think that these peculiar galaxies did indeed become spirals through collisions and merging. Although it was commonly believed that galaxy mergers decreased significantly eight billion years ago, the new result implies that mergers were still occurring frequently after that time — up to as recently as four billion years ago. “Our aim was to find a scenario that would connect the current picture of the Universe with the morphologies of distant, older galaxies — to find the right fit for this puzzling view of galaxy evolution,” says Hammer.

Also contrary to the widely held opinion that galaxy mergers result in the formation of elliptical galaxies, Hammer and his team support a scenario in which these cosmic clashes result in spiral galaxies. In a parallel paper published in Astronomy & Astrophysics, they delve further into their ‘spiral rebuilding’ hypothesis, which proposes that peculiar galaxies affected by gas-rich mergers are slowly reborn as giant spirals with discs and central bulges. Although our own Galaxy is a spiral galaxy, it seems to have been spared much of the drama; its formation history has been rather quiet and it has avoided violent collisions in astronomically recent times. However, the large Andromeda Galaxy from our neighbourhood has not been so lucky and fits well into the ‘spiral rebuilding’ scenario. Researchers continue to seek explanations for this.

Notes for editors:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Hammer and his team used data from the Sloan Digital Sky Survey undertaken by Apache Point Observatory, New Mexico, USA, and from the GOODS field and Hubble Ultra Deep Field taken by the Advanced Camera for Surveys aboard Hubble.

R. Delgado-Serrano, et al., 2010, How was the Hubble Sequence 6 Giga-years ago? Astronomy & Astrophysics, 509, A78.

F. Hammer et al., 2009, The Hubble Sequence: just a vestige of merger events? Astronomy & Astrophysics, 507, 1313.

Source: ESA

Saturday, February 6, 2010

Close Up Pictures Of Pluto's Face

Since discovered in 1930, there has never been observed which can provide a detailed picture of the face of Pluto. Although Pluto is an interesting object, even a topic of debate will be the definition of Pluto in 2006; but Pluto is still difficult to observe and record the details, because a small and distant.

However, Hubble Space Telescope (HST), has changed all that. With the observations that have been conducted since 1994, until the recent images taken between the years 2002-2003, then obtained a more detailed picture of Pluto, rather than observations that have been made ever. These results are a long way from the details, because the challenge to record details such as a soccer ball from a distance of 60 km.

Change the face of Pluto Hubble Space Telescope is seen. Credit: Hubble

Although the image of the HST is not enough to be able to record details of craters and mountains, and even then if there is one, but the recording is done the world HST indicates that vary in color, from white, dark orange-brown to dark. The colors are believed due to ultra-violet radiation from the sun which is in the distance, breaking the existing methane on Pluto's surface, causing a dark brown residue rich in carbon.

Pluto is also changing illumination, in the northern polar region of southern luminous and dark and reddish. The summer approaching Pluto's north pole causes ice to melt and experiencing freezing in the darker areas due terbayangi on the planet. HST has shown that Pluto is not just a ball of ice and rock, but a world that has a dramatic change in atmosphere.

Change season due to the elliptical orbit of Pluto 248 years along with the slanted axis. Season becomes elliptical symmetry because Pluto's orbit. Spring transition into summer in the polar hemisphere rapidly occurred in the north, because Pluto is moving very fast along the orbit as it moves around the Sun in the direction of approach.

Earth Observation landing between 1988 and 2002 showed the mass multiplication of the atmosphere have all the time allegedly due to heating and sublimation of nitrogen ice. HST images of the season to give an understanding of what happened on Pluto and the fate of the atmosphere.

HST image of this is that terdetil at the moment, at least until the New Horizon spacecraft will fly past Pluto and will record more detailed images again, and give a better picture of what is happening on the surface of Pluto, and was still waiting until 2015 to will come.

Source: Hubblesite and Langit Selatan

Tuesday, January 26, 2010

Soal-Soal Latihan Astronomi 2010

Silakan didownload beberapa file soal-soal latihan yang dapat digunakan sebagai bahan diskusi dan latihan. Selamat belajar dan semoga bermanfaat.

Link:
1. http://astronomy.case.edu/steven/temp/
olympiad/2008_C_olympiad_master.pdf
2. http://olympiads.hbcse.tifr.res.in/uploads/inao-jr-ans
3. Soal - Soal dari Ajang 2nd dan 3rd IOAA


Sunday, January 24, 2010

Oposisi Mars 2010

Beberapa tahun yang lalu, mungkin ada yang masih ingat, ketika ramai dibicarakan bahwa Mars akan mendekati Bumi dengan ukuran sebesar Bulan, tentunya tidak!

Oposisi Mars dilihat dari arah kutub. Kredit : ESA

Memang benar bahwa dalam lintasannya mengitari Matahari, baik Bumi dan Mars pada suatu ketika berada pada suatu posisi yang saling mendekat satu sama lain, karena lintasan Bumi, Mars, tidaklah merupakan lingkaran sempurna, tetapi berupa lintasan elips, dengan Matahari berada pada salah satu titik fokus elips.

Bumi bergerak mengitari Matahari lebih cepat daripada Mars, dan setiap 26 bulan, Bumi akan mendahului Mars melalui lintasan dalam, dan ketika itu, saat Matahar-Bumi-Mars berada pada segaris, dikenal sebagai oposisi Mars. Maka, oposisi Mars akan selalu terjadi setiap 26 bulan, dan biasanya di waktu oposisi tersebut maka, Bumi dan Mars berada pada posisi yang saling berdekatan.

Simulasi posisi Bumi-Mars & Matahari dapat dilihat di sini.

Jarak antara Bumi dan Mars tidak selalu sama setiap oposisi, karena orbit Mars yang sedikit lebih lonjong, maka jarak terdekat antara Bumi dan Mars tidak selalu tepat saat oposisi, tetapi selalu berada di sekitar waktu oposisi, yang berselisih beberapa hari dari waktu oposisinya. Dan biasanya, pada saat saling mendekat itu, maka Mars akan tampak cerlang dan cerlang, lebih kemerahan, kelihatan lebih jelas, baik diamati mempergunakan mata, binokular ataupun teleskop, tetapi yang pasti, tidak akan mencapai sebesar Bulan!

Oleh karena bentuk geometri yang unik itu, maka setiap terjadi jarak yang terdekat antara Bumi-Mars (yang berperiode 26 bulan itu), tidak akan pernah sama dari satu kejadian ke kejadian berikutnya. Pada kejadian oposisi Mars tahun 2003, yang dikenal sebagai peristiwa Mars dalam posisi paling dekat (sedekat-dekatnya) dengan Bumi, jarak yang terhitung sebagai terdekat adalah 55758006 km, dengan diameter tampak sekitar 25″; dan fenomena ini hanya bisa terjadi setiap 60 ribu tahun. Besarkah itu? Bagi yang beruntung mengamati saat itu, Mars masih tetap sama seperti Mars yang telah diamati nenek moyang kita, dengan mata telanjang, masih berupa noktah merah terang di langit. Bahkan dengan teleskop sekalipun, tidak banyak berubah kenampakannya, hanya, detilnya agak lebih tampak sedikit.

Mars jelang oposisi yang dipotret Hubble sejak tahun 1995 - 2007. Kredit : NASA/Hubble

Dan kemudian, di awal tahun 2010 ini, melalui siklus 26-bulan berikutnya (sesudah 2007), maka si merah kembali mendekat dengan Bumi! Di bulan Januari ini, Mars telah mencapai kecerlanganan mencapai sekitar -1 magnitudo, cukup terang teramati di langit sebagai suatu noktah merah yang jelas terlihat mempergunakan mata telanjang. Pada tanggal 27 Januari 2010, posisi terdekatnya mencapai 99 juta km, dengan diameter tampak sekitar 14″, lalu, oposisi Mars tercapai pada tanggal 29 Januari 2010, dengan magnitudo mencapai -1,28. Mars akan berada dalam kondisi yang sangat cerlang dengan magnitudo di sekitar -1, sampai dengan tanggal 14 Februari 2010, dan sesudah itu akan semakin meredup.

Lalu, bagaimana kita menemukan Mars? Mudah, di bulan-bulan ini, ketika sore, carilah ke arah terbit di timur, apabila ada sebuah noktah yang cerlang berwarna kemerahan, besar kemungkinan itulah dia. Apabila kita telah mengetahui tentang rasi-rasi di langit, (mempergunakan peta langit sangat membantu), carilah rasi Cancer, maka disitulah ia berada!

Sumber: Langit Selatan

Thursday, January 21, 2010

The Known Universe



What would it look like to travel across the known universe? To help humanity visualize this, the American Museum of Natural History has produced a modern movie featuring many visual highlights of such a trip. The video starts in Earth's Himalayan Mountains and then dramatically zooms out, showing the orbits of Earth's satellites, the Sun, the Solar System, the extent of humanities first radio signals, the Milky Way Galaxy, galaxies nearby, distant galaxies, and quasars. As the distant surface of the microwave background is finally reached, radiation is depicted that was emitted billions of light years away and less than one million years after the Big Bang. Frequently using the Digital Universe Atlas, every object in the video has been rendered to scale given the best scientific research in 2009, when the video was produced. The film has similarities to the famous Powers of Ten video that has been a favorite of many space enthusiasts for a generation.


Source: APOD

Monday, January 18, 2010

Astronomy Without A Telescope – Getting Orientated


Artikel berikut mengenai bagaimana memperkenalkan astronomi kepada orang lain yang "buta" astronomi. Sumber: universetoday.

We’ve all been there. You’ve met someone nice – but for some inexplicable reason, they don’t get astronomy. So how do you start gently introducing them to your life’s passion (about astronomy that is) without scaring them away?

First it’s important to recognize that not everyone will be instantly in awe to learn you own a 14-inch Schmidt-Cassegrain with four speed microslew. Weird, but there it is. And it’s going to be a challenge getting that special someone to drive out to a lonely spot in the wilderness for some proper dark sky viewing – and don’t even mention that there’s such a thing as naked eye astronomy.

Start with the Sun – it’s big and it’s obvious and everyone gets that it rises in the east and sets in the west. Well, that of course means that the Earth is actually spinning from west to east. And heck, you’re an astronomer, so you’re bound to know your cardinal directions on familiar ground – so just point. We are spinning that way.

And if you are in the right part of the lunar cycle – you might comment, on one of those romantic moonlit evenings, that last night at this time the Moon was there – and tonight it’s shifted a bit to the east. Don’t dwell on it – just put the idea out there. The next night let them note that – hey, it’s moved even further east! They might even notice that it’s filled out a bit – but this is not the time to introduce them to the word gibbous.

What’s happening is that they are starting to make their own astronomical observations. All you have to do is to find an opportune moment to pull the background together. If the Earth spinning from west to east, that means that from a perspective in space – at least from above the North Pole – it’s spinning anti-clockwise. And the fact that the Moon inches further towards the east day by day means it’s orbiting the Earth anti-clockwise.

Hopefully you’ve captured their interest enough to carry on with the fact that actually all the planets orbit the Sun in that same anticlockwise direction – indeed, even the Sun spins in that same direction, once every 28 days. A quick mention of the theory that the whole solar system formed from a gas cloud that spun down into a disk – and it’s probably time to move on to another conservation topic. This is not the time to introduce them to the conservation of angular momentum. Pace yourself.


From here – a wealth of discussion could arise in the days to come. Your potential new partner might ponder whether all the planets spin in the same direction – to which you can reply well mostly, except for Venus and Uranus – and then you’re away talking about planetary collisions. Or, maybe you’ll be asked whether all the planet’s moons orbit in the same direction – to which you can reply well mostly, but there’s Triton that goes the wrong way around Neptune – probably because it came in from the Kuiper Belt. There’s a Kuiper Belt now?

Thursday, January 14, 2010

Sekilas tentang 99942 Apophis

Mungkin Anda belum pernah mendengar tentang asteroid ini. Mengapa asteroid 99942 Apophis ini menjadi beda dengan asteroid lainnya adalah karena ada probabilitas (kemungkinan) orbit asteroid ini menyilang orbit Bumi yang akan menghasilkan tabrakan (collide). Namun, sebelum kita menjadi panik, perlu diperhatikan tentang kecilnya probabilitas tabrakan dan perhitungan orbit masih penuh ketidakpastian. Perlu diketahui, tidak mudah membuat peta lengkap orbit sebuah benda langit seperti asteroid karena orbit asteroid sangat terpengaruh gaya gravitasi benda2 langit lain yang dilewatinya selama mengorbit. Berikut artikel tentang asteroid ini yang diambil dari wikipedia dan NASA.

99942 Apophis (pronounced /əˈpɒfɪs/, previously known by its provisional designation 2004 MN4) is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a small probability (up to 2.7%) that it would strike the Earth in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However, a possibility remains that during the 2029 close encounter with Earth, Apophis will pass through a gravitational keyhole, a precise region in space no more than about 600 meters across, that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale until August 2006. It broke the record for the highest level on the Torino Scale, being, for only a short time, a level 4, before it was lowered

Additional observations of the trajectory of Apophis revealed the keyhole will likely be missed. On August 5, 2006 Apophis was lowered to a Level 0 on the Torino Scale. As of October 7, 2009, the impact probability for April 13, 2036, is calculated as 1 in 250,000. An additional impact date in 2037 was also identified; the impact probability for that encounter is calculated as 1 in 12.3 million.

Basic data
Based upon the observed brightness, Apophis' length was estimated at 450 metres (1,500 ft); a more refined estimate based on spectroscopic observations at NASA's Infrared Telescope Facility in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 metres (1,100 ft).

In October 2005 it was predicted that the asteroid will pass just below the altitude of geosynchronous satellites, which are at 35,786 kilometres (22,236 mi). Such a close approach by an asteroid of this size is expected to occur only every 1,300 years or so. Apophis’ brightness will peak at magnitude 3.3, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter will be ~2 arcseconds, so that it will be barely resolved by telescopes not equipped with adaptive optics.



File:2004MN4 Sormano.gif

Close approaches
After the Minor Planet Center confirmed the June discovery of Apophis, an April 13, 2029 close approach was flagged by NASA's automatic Sentry system and NEODyS, a similar automatic program run by the University of Pisa and the University of Valladolid. On that date, it will become as bright as magnitude 3.3 (visible to the naked eye from rural as well as darker suburban areas, visible with binoculars from most locations). This close approach will be visible from Europe, Africa, and western Asia. As a result of its close passage, it will move from the Aten to the Apollo class.

After Sentry and NEODyS announced the possible impact, additional observations decreased the uncertainty in Apophis' trajectory. As they did, the probability of an impact event temporarily climbed, peaking at 2.7% (1 in 37). Combined with its size, this caused Apophis to be assessed at level 4 on the Torino Scale and 1.10 on the Palermo scale, scales scientists use to represent the danger of an asteroid hitting Earth. These are the highest values for which any known object has been rated on either scale.

On Friday, April 13, 2029, Apophis will pass Earth within the orbits of geosynchronous communication satellites. It will return for another close Earth approach in 2036.

Precovery observations from March 15, 2004 were identified on December 27, and an improved orbit was computed.Radar astrometry further refined the orbit. The 2029 pass will actually be much closer than the first predictions, but the uncertainty is such that an impact is ruled out. Similarly, the pass on April 13, 2036 carries little risk of an impact.

2013 refinement
The close approach in 2029 will substantially alter the object's orbit, making predictions uncertain without more data. "If we get radar ranging in 2013 [the next good opportunity], we should be able to predict the location of 2004 MN4 out to at least 2070." said Jon Giorgini of JPL. Apophis will pass within 0.09666 AU (14.4 million km) of the Earth in 2013 allowing astronomers to refine the trajectory for future close passes.

In July 2005, former Apollo astronaut Rusty Schweickart, as chairman of the B612 Foundation, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance with Earth, which would increase the probability of future impacts. Schweickart asked for an investigation of the necessity of placing a transponder on the asteroid for more accurate tracking of how its orbit is affected by the Yarkovsky effect.

NASA Refines Asteroid Apophis' Path Toward Earth
Using updated information, NASA scientists have recalculated the path of a large asteroid. The refined path indicates a significantly reduced likelihood of a hazardous encounter with Earth in 2036.

The Apophis asteroid is approximately the size of two-and-a-half football fields. The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA's Jet Propulsion Laboratory in Pasadena, Calif. They will present their updated findings at a meeting of the American Astronomical Society's Division for Planetary Sciences in Puerto Rico on Oct. 8.

"Apophis has been one of those celestial bodies that has captured the public's interest since it was discovered in 2004," said Chesley. "Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million."

A majority of the data that enabled the updated orbit of Apophis came from observations Dave Tholen and collaborators at the University of Hawaii's Institute for Astronomy in Manoa made. Tholen pored over hundreds of previously unreleased images of the night sky made with the University of Hawaii's 88-inch telescope, located near the summit of Mauna Kea.

Tholen made improved measurements of the asteroid's position in the images, enabling him to provide Chesley and Chodas with new data sets more precise than previous measures for Apophis. Measurements from the Steward Observatory's 90-inch Bok telescope on Kitt Peak in Arizona and the Arecibo Observatory on the island of Puerto Rico also were used in Chesley's calculations.

The information provided a more accurate glimpse of Apophis' orbit well into the latter part of this century. Among the findings is another close encounter by the asteroid with Earth in 2068 with chance of impact currently at approximately three-in-a-million. As with earlier orbital estimates where Earth impacts in 2029 and 2036 could not initially be ruled out due to the need for additional data, it is expected that the 2068 encounter will diminish in probability as more information about Apophis is acquired.

Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029. Additional observations of the asteriod ruled out any possibility of an impact in 2029. However, the asteroid is expected to make a record-setting -- but harmless -- close approach to Earth on Friday, April 13, 2029, when it comes no closer than 18,300 miles above Earth's surface.

"The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL. "The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed."

The science of predicting asteroid orbits is based on a physical model of the solar system which includes the gravitational influence of the sun, moon, other planets and the three largest asteroids.

NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near Earth-Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. Cornell University operates the Arecibo Observatory under a cooperative agreement with the National Science Foundation in Arlington, Va.

Possible impact effects
NASA initially estimated the energy that Apophis would have released if it struck Earth as the equivalent of 1,480 megatons of TNT. A later, more refined NASA estimate was 880 megatons. The impacts which created the Barringer Crater or the Tunguska event are estimated to be in the 3–10 megaton range. The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons.

Path of risk where 99942 Apophis may impact Earth in 2036.

The exact effects of any impact would vary based on the asteroid's composition, and the location and angle of impact. Any impact would be extremely detrimental to an area of thousands of square kilometres, but would be unlikely to have long-lasting global effects, such as the initiation of an impact winter (?).

The B612 Foundation made estimates of Apophis' path if a 2036 Earth impact were to occur as part of an effort to develop viable deflection strategies.The result is a narrow corridor a few miles wide, called the path of risk, and it includes most of southern Russia, across the north Pacific (relatively close to the coastlines of California and Mexico), then right between Nicaragua and Costa Rica, crossing northern Colombia and Venezuela, ending in the Atlantic, just before reaching Africa.Using the computer simulation tool NEOSim, it was estimated that the hypothetical impact of Apophis in countries such as Colombia and Venezuela, which are in the path of risk, would have had more than 10 million casualties.An impact several thousand miles off the West Coast of the US would produce a devastating tsunami.

Wednesday, January 13, 2010

Gerhana Matahari Cincin 15 Januari 2010

Hari Jumat, tanggal 15 Januari 2010 akan terjadi fenomena Gerhana Matahari Cincin. Gerhana Matahari pada 15 Januari 2010 merupakan gerhana matahari cincin (annular), yaitu bundaran bulan tidak sepenuhnya menutupi matahari sehingga masih tersisa bagian yang bercahaya, yang mengesankan seperti cincin. Namun dari Indonesia, yang bisa kita amati hanyalah Gerhana Matahari Sebagian (GMS) saja, karena tidak ada daerah di Indonesia yang dilalui oleh jalur totalitasnya, tidak seperti GMC 26 Januari 2009 yang lalu.

Daerah di Indonesia yang dapat menyaksikan gerhana nanti adalah seluruh Sumatra dan Kalimantan, bagian barat pulau Jawa, dan bagian utara pulau Sulawesi. Meskipun begitu, proses GMS akan bisa kita saksikan lebih baik apabila kita berada di wilayah barat Indonesia. Di sana gerhana akan berlangsung lebih lama dan piringan Matahari yang tertutup oleh Bulan juga lebih banyak dibandingkan dengan pengamatan di daerah timur.

Untuk pengamat yang berada di Banda Aceh, gerhana dimulai pada sekitar pukul 13.40 WIB dan berakhir pada pukul 16.40 WIB. Luas daerah piringan Matahari yang tertutupi Bulan mencapai 46% pada saat maksimumnya, yaitu pada sekitar pukul 15.20 WIB. Jumlah tersebut jauh lebih besar daripada hasil pengamatan di Manado yang hanya menutupi 0,3% daerah piringan Matahari saja.

Penjelasan lebih detail tentang Gerhana tersebut disajikan dalam artikel di bawah ini.


The solar eclipse of January 15, 2010 is an annular eclipse of the Sun with a magnitude of 0.9190. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partially obscuring Earth's view of the Sun. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun, causing the sun to look like an annulus (ring), blocking most of the Sun's light. An annular eclipse will appear as partial eclipse over a region thousands of miles wide.

It will be visible as a partial eclipse in much of Africa, Eastern Europe, Middle East and Asia. It will be seen as annular within a narrow stretch of 300 km (190 mi) width across Central Africa, Maldives, South Kerala, South Tamil Nadu, North Sri Lanka, Burma and China.


Visibility

SE2010Jan15A.gif

http://eclipse.gsfc.nasa.gov/SEsarosanimate/141.gif

The eclipse starts at Uganda, passes through Nairobi, enters Indian ocean where the greatest eclipse is taking place in mid of Ocean for a maximum of 11 Mins and 7.7 seconds.


After that enters Maldives, where it would be the longest on land with 10.8 Min of viewing. This makes the tiny islands of Maldives the best spot for viewing this eclipse from land. The annular Eclipse at Male', the capital city of Maldives starts at 12:20:20 hrs and ends 12:30:06 hrs Maldives local time (GMT+5hrs). This is also the longest duration of any city having an international airport in the eclipse track.[1]

After that enters and exits India at Rameswaram. Only place of land under the eclipse on India. At approx 13.20 hrs IST, there is a annular solar Eclipse of sun over India. The eclipse is viewable for full 10.4 min in India. The best place from India is Dhanushkodi in Pamban Island off Tamil Nadu coast. Dhanushkodi is now a ghost town and it is about 18 km South east from Rameshwaram and 18 Km West of Mannar Island in Sri Lanka.

After Rameswaram, enters Sri Lanka at Delft Island, exits at Jaffna in Sri Lanka, cross Bay of Bengal and ends in Burma - China border. Full data is in the NASA website.

For best viewing of the Eclipse, you need to travel to Maldives, where many International flights land and take off everyday, being a world famous tourist destination. Visa for Maldives is free for 30 days for a tourist entry.

The best location In India lies between Kodandaramar Temple islet and Dhanushkodi, which falls on the central line of the Eclipse. The northern most limit of shadow in India is Cuddalore, Neyveli, Erode, Kodaikanal, Madurai. Other best locations: Trivandrum, Thoothukudi and Cape Comorin which lies 22 km north of Central line.

Only means of reaching Dhanushkodi or kodandaramar temple is by ST bus or Auto from Rameswaram and for Dhanushkodi after road's end it is only by fish carts or 4x4 SUVs. Permission is required for entering Dhanushkodi ruins from the coast guard post as that area is 10 km from Sri Lankan coast.

The centre line passes some 2 km east of Kodandaramar Temple. The exact location is between NH end and Dhanushkodi ruins. Dhanushkodi is about 2 km east of the central line. The degree difference is about 0.2 between Central line - Kodandaramar Temple and Dhanushkodi ruins vice versa. Dhanushkodi is about 5 km from Kodandaramar Temple.

Enthusiasm
People, especially the sky enthusiasts from entire India are highly enthusiast about the annular eclipse as the last total solar eclipse of July 22, 2009, being visible on Indian soil remained somewhat a frustrating experience for many of them who got clouded out on the eclipse day in Monsoon cloud. The total solar eclipse of August 11, 1999, was also similar negative experience.

Astronomy clubs from the whole country are gathering in different locations along the shadow track. One section of them, preferring to observe Bailie Beads more are concentrating on the location at the northern limit of the shadow track while the other section is going deep towards the centerline to have better view of the Ring shaped Sun.

Leave aside the sky watcher's associations from Bangalore or Chennai, even clubs like SWAN(Sky Watchers Association of North Bengal) from eastern Himalayan region like Darjeeling or North East region are also gathering in Rameswaram.

Members of SPACE (Science Popularisation Association of Communicators and Educators) and STEPL (Space Technology Education pvt ltd) have planned various observation plans for this eclipse which includes scientific studies as well as watching eclipse for a layman as a curious observer.

Sumber: NASA, wikipedia, duniaastronomi

Tuesday, January 12, 2010

Sense of Scale: Star's Size

Sumber: wikipedia

Monday, January 4, 2010

Hujan Meteor Quadrantins - 3/4 Januari 2010

The Quadrantid meteor shower is one of the strongest meteor showers of the year, but observers can be disappointed if conditions are not just right. The point from where the Quadrantid meteors appear to radiate is located within the extinct constellation Quadrans Muralis. On modern star charts, this radiant is located where the constellations Hercules, Boötes, and Draco meet in the sky. The shower can appear almost nonexistent until about 11 p.m. Unfortunately, the radiant does not attain a very high altitude for most Northern Hemisphere observers before morning twilight puts an end to the show. The best observations are actually possible from countries with high northern latitudes, such as Canada, Finland, Sweden, and Norway. The display is virtually nonexistent for observers in the Southern Hemisphere.

The Quadrantids generally begin on December 28 and end on January 7, with maximum generally occurring during the morning hours of January 3/4. The Quadrantids are barely detectable on the beginning and ending dates, but observers in the Northern Hemisphere can see from 10 to around 60 meteors per hour at maximum. The maximum only lasts for a few hours.

Thus, the Quadrantid meteor shower is an extremely short one, lasting only a few hours. In 2010 the Quadrantids are predicted to reach a peak of about 120 meteors per hour at 1 p.m. EST on Sunday, January 3. Unfortunately, for us in North Carolina, this sharply peaked shower will not really get rolling before sunrise although a few early meteors may be spotted before morning twilight as the shower approaches. Viewers in Asia will fare better since the peak occurs before sunrise there. In any case, one should observe from a clear, dark location with a good horizon. Look high in the northeast for meteors appearing to radiate out of a point between the constellations of Hercules the strong man and Boötes the herdsman. Binoculars or telescopes are not needed to observe meteors. This year Full Moon occurs on New Years Eve which means a waning gibbous moon will interfere with observations of the fainter meteors between midnight and dawn. Incidentally, meteor showers are usually named after the constellation out of which the meteors seem to originate, i.e., their radiant point. However, there is no modern constellation of Quadrans. Instead, this shower retains its name from the obsolete constellation of Quadrans Muralis an instrument used to measure the positions of stars. The actual radiant of the shower is in the edge of Boötes.

(From several sources: 1 dan 2)