Wednesday 27 August 2008

2nd International Olympiad On Astronomy and Astrophysics Part II

Olimpiade Astronomi dan Astrofisika Internasional
Ke-2



Related Topic [2nd International Olympiad On Astronomy and Astrophsics Part I]


Banjar Astro Physics Association [Kembali ke Home]

Oleh:
Arip Nurahman
Department of Physics
Faculty of Sciences and Mathematics, Indonesia University of Education

and

Follower Open Course Ware at Massachusetts Institute of Technology
Cambridge, USA
Department of Physics
http://web.mit.edu/physics/
http://ocw.mit.edu/OcwWeb/Physics/index.htm
&
Aeronautics and Astronautics Engineering
http://web.mit.edu/aeroastro/www/
http://ocw.mit.edu/OcwWeb/Aeronautics-and-Astronautics/index.htm


















CURRICULUM VITAE

Name: Ronald David Ekers
Date of Birth: September 18, 1941
Place of Birth: Victor Harbour, South Australia
Academic Qualifications:
1962 B Sc, 1963 (hon) University of Adelaide, South Australia
1967 Ph D Australian National University, A.C.T.
Positions Held:
1967 - 1970 California Institute of Technology, Pasadena, CA, U.S.A.
1970 - 1971 Institute of Theoretical Astronomy, Cambridge, U.K.
1971 - 1980 Kapteyn Laboratory, Groningen, The Netherlands
1980 - 1988 Assistant Director, National Radio Astronomy Observatory, Director for VLA Operations, Socorro, U.S.A.
1988 - 2003 Director Australia Telescope National Facility, Australia
2003 Federation Fellow, CSIRO
Other Appointments (last 10 years only):
1989-2005 Adjunct Professor, Australian National University
1997 Oort Visiting Chair, Leiden, The Netherlands
1997-1998 Chairman, SETI working group (USA)
1997-1999 Australian representative OECD Megascience Forum working group on radio astronomy
1997-2001 Member, Anglo-Australian Telescope Board
2002-2004 Chairman, Anglo-Australian Telescope Board
1999-2003 Member, Max Planck Institute for Radio Astronomy advisory board (Germany)

2000-2002 Chairman, International SKA Steering Committee

2001 Visiting Miller Professor, University of California, Berkeley, USA
2001-2002 Member, Radio Astronomy Task Force, OECD Global Science Forum
2003 Australian Astronomy Board of Management
2003-2006 President, International Astronomical Union
2006-2009 Advisor, International Astronomical Union
Major awards, honours
1993 Fellow of the Australian Academy of Science
1993 Foreign Member, Royal Netherlands Academy of Sciences
1999 Brodie Hall lecturer (W. Australia)
2003 Centenary Medal (Australia)
2003 Elected a member of the American Philosophical Society
2004 Nov Jansky Lecturer (NRAO, USA)
2005 May Flinders Medal (Australian Academy of Science)
2005 May26 Fellow of Royal Society of London
Open Lecture

Sasana Budaya Ganesha ITBMonday 25 August 2008 09.00 - 12.00 WIB

"The Big Bang, Black Holes, Pulsars, and Extraterrestrial Life"

Prof. Ronald David Ekers

Synopsis :
During the 20th century astronomers built new telescopes to explore the universe using many different wavelengths from radio to infrared, X-ray, and cosmic rays.
These new ways of 'seeing' the universe revealed many unexpected objects in the cosmos.
Prof. Ekers will discuss some of the discoveries which have revolutionized our knowledge of the Universe and how they were made. He will talk about the big bang and how our universe formed, the discovery of the black holes in the centres of galaxies, we will listen to some of the pulsars and discuss the chance of finding other life.
Our understanding of the Universe is based on observations by the new generations of great telescopes and on the interpretation of data by astronomers from all over the globe. Astronomy has always been an international science driven by a shared vision to better understand our universe and our place in it. In the twenty first century we have a vision to build even grander telescopes, a vision which can only be realized through innovation and international collaboration.




Extraterrestrial Life
By:
Arip Nurahman


Sepi, sendiri mengarungi lautan sang kala diatas butir biru kehampaan, terbentang dihorizon langit malam, tidak diragukan kesendirian mengajak kita berderai air mata, melantunkan sajak penderitaan karena terpasung masa yang silam. ada yang datang dan pergi dari palung kalbu, ada yang berdegup ketika kenangan datang, masihkah ada...harapan..ataukah aku memang sendiri disini...Agaknya kesepian masih senantiasa memayungiku. Kesepian ini kini merasuk hingga ke tulang-tulangku...
Adakah disana menungguku....atau Kau melupakanku...
(-“H2O”-)
Extraterrestrial life is life originating outside of the Earth. It is the subject of astrobiology, and its existence remains hypothetical. There is no credible evidence of extraterrestrial life that has been widely accepted by the scientific community. There are several hypotheses regarding the origin of extraterrestrial life if it exists. One proposes that it may have emerged, independently, in different places in the universe. An alternative hypothesis is panspermia, which holds that life emerging in one location then spreads between habitable planets. These two hypotheses are not mutually exclusive. The study and theorization of extraterrestrial life is known as astrobiology, exobiology or xenobiology. Speculative forms of extraterrestrial life range from sapient or sentient beings to life at the scale of bacteria.
Suggested locations that might have once developed or continue to host life include the planets Venus[1] and Mars, moons of Jupiter and Saturn (e.g. Europa,[2] Enceladus and Titan). Gliese 581 c and d, recently discovered to be near Earth-mass extrasolar planets apparently located in their star's habitable zone, and having the potential to have liquid water.[3]test

Contents
Introduction
Pertanyaan ini telah dicoba untuk dirumuskan secara matematis oleh Prof. Frank Drake di tahun 1960-an. Prof. Frank Drake menyusun rumus ini pada pertemuan mengenai SETI (Search of Extra Terrestrial Intelligence /Pencarian Kehidupan yang cerdas di luar Bumi) di Green Bank, Virginia Barat.

Contents
Mari kita sedikit bermain hitung-hitungan, menggunakan persamaan yang dirumuskan oleh Prof. Drake, sbb:
N = R* × fp × fe × fl × fi × fc × ft

N = jumlah peradaban di dalam galaksi kita, yang memungkinkan kita bisa melakukan kontak.;

R* = rasio pembentukan bintang di dalam galaksi kita

fp = fraksi dari bintang-bintang yang mempunyai planet

fe = rata-rata jumlah planet yang berpotensi punya penunjang hidup per-bintang (yang mempunyai planet)

fl = fraksi dari yang di atas dimana ada kehidupannya berkembang

fi = fraksi dari yang di atas dimana kehidupannya mengembangkan kecerdasan

fc = fraksi dari peradabaan yang mengembangkan teknologi, yang bisa mengirimkan sinyal tentang keberadaannya, ke luar angkasa


ft = rentang waktu peradaban tersebut untuk mengirimkan sinyal ke luar angkasa
Tentu saja angka-angka yang berada pada sisi kanan tidaklah selalu disepakati oleh banyak pihak. Tetapi, tidaklah salah untuk mencobakan satu atau dua angka tertentu sebagai pendekatan awal, sehingga bisa menggambarkan kemungkinannya. Bahkan kita bisa mencoba asumsi kita sendiri.
Pada tahun 1961, Prof. Drake mempergunakan pendekatan angka-angka sebagai berikut:

R* = 10/tahun (10 bintang terbentuk dalam setahun)


fp = 0.5 (setengah dari setiap bintang terbentuk punya planet)


fe = 2 (2 planet per bintang memungkinkan adanya kehidupan)

fl = 1 (100% dari setiap planet mengembangkan kehidupan)


fi = 0.01 (1% dari setiap kehidupan mengembangkan kecerdasan)

fc = 0.01 (1% yang bisa berkomunikasi)

ft = 10000 tahun (hanya bisa terjadi komunikasi setelah 10000 tahun, setelah sinyal dikirimkan)
Maka N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10. Baiklah, ada 10 kemungkinan peradaban lain di luar sana yang mungkin berkomunikasi dengan kita. Tapi apakah benar demikian adanya?
Nilai R* bisa diterima karena memang banyak ditemukan di alam dari pengamatan-pengamatan; demikian juga dengan nilai fp tidak terlalu diperdebatkan. Tetapi angka-angka yang lain masih harus di uji lagi, dan disesuaikan dengan pengamatan-pengamatan terkini.
Penemuan terkini tentang planet-planet gas di dekat orbit bintang menyebabkan nilai fe semakin tidak pasti, karena memberikan keragu-raguan apakah planet yang mempunyai penunjang-hidup, dapat bertahan di dalam sistem bintang? Sebagai tambahan, kebanyakan bintang di dalam galaksi merupakan raksasa merah, dengan radiasi UV yang sangat kecil, menambah kecil kemungkinan adanya planet yang bisa ditinggali. Alih-alih terjadi semburan energi bintang pada UV oleh bintang, semburan terjadi pada sinar-X, yang malah menyebabkan adanya erosi pada atmosfer planet. Jadi apakah mungkin suatu planet dengan penunjang kehidupan bertahan dalam kondisi seperti itu?
Selain itu, adanya kemungkinan jika planet-planet gas tersebut mempunyai bulan yang mempunyai kemungkinan adanya kehidupan
(seperti contoh kasus satelit Jupiter Europa) menambah ketidak-pastian-nya menjadi semakin besar.

Angka-angka untuk fl, fi dan fc, sampai sekarang masih menjadi perdebatan.
Perdebatannya melibatkan Geologi, Biologi dan semua ilmu yang berkaitan dengan bagaimana asal muasal planet Bumi serta kehidupannya. Penemuan adanya kehidupan di Mars menambah keruwetan dalam menentukan angka-angka tersebut, jika kehidupan di Mars berasal dari proses pembentukan yang berbeda dengan di Bumi, maka angka fl harus lebih lagi. Itu pun, jika ada kecerdasan lain, apakah mereka akan berpartisipasi dalam mencari kehidupan di luar planet-nya? Apakah mereka peduli mereka sendirian atau tidak di alam semesta? Mempunyai kecerdasan, berarti mempunyai kebebasan untuk memilih, sekalipun memiliki teknologinya, tetapi jika tidak berminat mencari tahu, maka kita di Bumi tidak akan pernah tahu. Atau, jangan-jangan, malah mereka sudah datang kesini, sudah mencoba berkomunikasi dengan kita?
Nilai ft, hanya berlaku untuk daerah di sekitar Matahari, sementara berapa jauh alam semesta ini? Luas sekali. Jika saja ada suatu peradaban yang mengirimkan pesan ke Bumi setelah 10ribu tahun dan baru kita terima sekarang,
Sampai saat ini, angka-angka yang diterapkan dalam perumusan tersebut masih dianggap spekulatif, tetapi, spekulatif atau bukan; rumus yang dibuat oleh Prof. Drake memberikan harapan, bahwa, secara statistik, masih ada kemungkinan kehidupan lain di luar Bumi, dan ini menjadi pijakan untuk kita terus menerus melakukan pengamatan, studi astronomi dan mencari tahu tentang banyak hal yang sampai saat ini belum kita ketahui tentang alam semesta kita.

Penutup

"Akan tiba masanya ketika sang kala mempertemukan kita dan kita telah benar-benar siap memulai awal dan mengarungi akhir dibawah payung kebesaran sang Maha cerdas semoga tetap lestari kenangan ini serta harapan yang dikandungnya"
(-“H2O”-)


Black Hole & Pulsar
by:
Attraiq Ramadhino

(Dosen Tamu di IOAA II, Kelas 6 SD Mentari Jakarta 11 Tahun)

A black hole is a region of space in which the gravitational field is so powerful that nothing, not even electromagnetic radiation (e.g. visible light), can escape its pull after having fallen past its event horizon. The term derives from the fact that the absorbsion of visible light renders the hole's interior invisible, and indistinguishable from the black space around it.
Despite its interior being invisible, a black hole may reveal its presence through an interaction with matter that lies in orbit outside its event horizon. For example, a black hole may be perceived by tracking the movement of a group of stars that orbit its center. Alternatively, one may observe gas (from a nearby star, for instance) that has been drawn into the black hole. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation that can be detected from earthbound and earth-orbiting telescopes.[1][2] Such observations have resulted in the general scientific consensus that—barring a breakdown in our understanding of nature—black holes do exist in our universe.[3]
The idea of an object with gravity strong enough to prevent light from escaping was proposed in 1783 by the Reverend John Michell[4], an amateur British astronomer. In 1795, Pierre-Simon Laplace, a French physicist independently came to the same conclusion.[5][6] Black holes, as currently understood, are described by the general theory of relativity. This theory predicts that when a large enough amount of mass is present in a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, preventing all matter and radiation within it from escaping.
While general relativity describes a black hole as a region of empty space with a pointlike singularity at the center and an event horizon at the outer edge, the description changes when the effects of quantum mechanics are taken into account. Research on this subject indicates that, rather than holding captured matter forever, black holes may slowly leak a form of thermal energy called Hawking radiation.[7][8][9] However, the final, correct description of black holes, requiring a theory of quantum gravity, is unknown.

Contents


Pulsars are highly magnetized rotating neutron stars that emit a beam of electromagnetic radiation in the form of radio waves. Their observed periods range from 1.4 ms to 8.5 s.[1] The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses are very regular. For some pulsars, the regularity of pulsation is as precise as an atomic clock.[2] Pulsars are known to have planets orbiting them, as in the case of PSR B1257+12. Werner Becker of the Max-Planck-Institut für extraterrestrische Physik said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work."[3]

Contents

Futher Information:

http://www.ioaa2.itb.ac.id/?m=1




SUPERNOVA

Add & Edited by:

Arip Nurahman

A supernova (plural: supernovae or supernovas) is a stellar explosion. They are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over its life span.[1] The explosion expels much or all of a star's material[2] at a velocity of up to a tenth the speed of light, driving a shock wave[3] into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant.
Several types of supernovae exist that may be triggered in one of two ways, involving either turning off or suddenly turning on the production of energy through nuclear fusion. After the core of an aging massive star ceases to generate energy from nuclear fusion, it may undergo sudden gravitational collapse into a neutron star or black hole, releasing gravitational potential energy that heats and expels the star's outer layers. Alternatively, a white dwarf star may accumulate sufficient material from a stellar companion (usually through accretion, rarely via a merger) to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it. Stellar cores whose furnaces have permanently gone out collapse when their masses exceed the Chandrasekhar limit, while accreting white dwarfs ignite as they approach this limit (roughly 1.38[4] times the mass of the Sun). White dwarfs are also subject to a different, much smaller type of thermonuclear explosion fueled by hydrogen on their surfaces called a nova. Solitary stars with a mass below approximately nine[5] solar masses, such as the Sun itself, evolve into white dwarfs without ever becoming supernovae.
On average, supernovae occur about once every 50 years in a galaxy the size of the Milky Way[6] and once every second somewhere in the universe.[7] They play a significant role in enriching the interstellar medium with heavy elements. Furthermore, the expanding shock waves from supernova explosions can trigger the formation of new stars.[8]
Nova (plural novae) means "new" in Latin, referring to what appears to be a very bright new star shining in the celestial sphere; the prefix "super-" distinguishes supernovae from ordinary novae, which also involve a star increasing in brightness, though to a lesser extent and through a different mechanism. According to Merriam-Webster's Collegiate Dictionary, the word supernova was first used in print in 1926.

Contents

· 1 Observation history
· 2 Discovery
· 3 Naming convention
· 4 Classification
· 5 Current models
o 5.1 Type Ia
o 5.2 Type Ib and Ic
o 5.3 Type II
§ 5.3.1 Core collapse
§ 5.3.2 Light curves and unusual spectra
o 5.4 Asymmetry
o 5.5 Type Ia vis-à-vis core collapse
· 6 Interstellar impact
o 6.1 Source of heavy elements
o 6.2 Role in stellar evolution
o 6.3 Impact on Earth
· 7 Milky Way candidates
· 8 See also
· 9 Notes
· 10 References
· 11 Further reading
· 12 External links

Observation history

Main article: History of supernova observation
The earliest recorded supernova, SN 185, was viewed by Chinese astronomers in 185 CE. The brightest recorded supernova was the SN 1006, which was described in detail by Chinese and Arab astronomers. The widely observed supernova SN 1054 produced the Crab Nebula. Supernovae SN 1572 and SN 1604, the last to be observed with the naked eye in the Milky Way galaxy, had notable effects on the development of astronomy in Europe because they were used to argue against the Aristotelian idea that the universe beyond the Moon and planets was immutable.[9]
Since the development of the telescope, the field of supernova discovery has enlarged to other galaxies, starting with the 1885 observation of supernova S Andromedae in the Andromeda galaxy. Supernovae provide important information on cosmological distances.[10] During the twentieth century, successful models for each type of supernova were developed, and scientists' comprehension of the role of supernovae in the star formation process is growing.
Some of the most distant supernovae recently observed appeared dimmer than expected. This has provided evidence that the expansion of the universe may be accelerating.[11][12]

Discovery

Because supernovae are relatively rare events within a galaxy, occurring about once every 50 years in the Milky Way.[6] Obtaining a good sample of supernovae to study requires regular monitoring of many galaxies.
Supernovae in other galaxies cannot be predicted with any meaningful accuracy. Normally, when they are discovered, they are already in progress.[13] Most scientific interest in supernovae—as standard candles for measuring distance, for example—require an observation of their peak luminosity. It is therefore important to discover them well before they reach their maximum. Amateur astronomers, who greatly outnumber professional astronomers, have played an important role in finding supernovae, typically by looking at some of the closer galaxies through an optical telescope and comparing them to earlier photographs.
Towards the end of the 20th century, astronomers increasingly turned to computer-controlled telescopes and CCDs for hunting supernovae. While such systems are popular with amateurs, there are also larger installations like the Katzman Automatic Imaging Telescope.[14] Recently, the Supernova Early Warning System (SNEWS) project has also begun using a network of neutrino detectors to give early warning of a supernova in the Milky Way galaxy.[15][16] A neutrino is a particle that is produced in great quantities by a supernova explosion,[17] and it is not absorbed by the interstellar gas and dust of the galactic disk.
Supernova searches fall into two classes: those focused on relatively nearby events and those looking for explosions farther away. Because of the expansion of the universe, the distance to a remote object with a known emission spectrum can be estimated by measuring its Doppler shift (or redshift); on average, more distant objects recede with greater velocity than those nearby, and so have a higher redshift. Thus the search is split between high redshift and low redshift, with the boundary falling around a redshift range of z = 0.1–0.3[18]—where z is a dimensionless measure of the spectrum's frequency shift.
High redshift searches for supernovae usually involve the observation of supernova light curves. These are useful for standard or calibrated candles to generate Hubble diagrams and make cosmological predictions. At low redshift, supernova spectroscopy is more practical than at high redshift, and this is used to study the physics and environments of supernovae.[19][20] Low redshift observations also anchor the low distance end of the Hubble curve, which is a plot of distance versus redshift for visible galaxies.[21][22]
See also: Hubble's law

Naming convention

Supernova discoveries are reported to the International Astronomical Union's Central Bureau for Astronomical Telegrams, which sends out a circular with the name it assigns to it. The name is formed by the year of discovery, immediately followed by a one or two-letter designation. The first 26 supernovae of the year get designated with an upper case letter from A to Z. Afterward, pairs of lower-case letters are used, starting with aa, ab, and so on.[23] Professional and amateur astronomers find several hundred supernovae each year (367 in 2005, 551 in 2006 and 572 in 2007). For example, the last supernova of 2005 was SN 2005nc, indicating that it was the 367th supernova found in 2005.[24][25]
Historical supernovae are known simply by the year they occurred: SN 185, SN 1006, SN 1054, SN 1572 (Tycho's Nova) and SN 1604 (Kepler's Star). Since 1885, the letter notation was used, even if there was only one supernova discovered that year (e.g. SN 1885A, 1907A, etc.)—this last happened with SN 1947A. The standard abbreviation "SN" is an optional prefix.

See also

Astronomy portal

Notes

  1. ^ The value is obtained by converting the suffix "nc" from base 26, with a=1, b=2, c=3, ... n=14, ... z=26. Thus nc = n×26+c = 14×26+3 = 367.
  2. ^ For a core primarily composed of oxygen, neon and magnesium, the collapsing white dwarf will typically form a neutron star. In this case, only a fraction of the star's mass will be ejected during the collapse.[108]
  3. ^ Per the American Physical Society Neutrino Study reference,[53] roughly 99% of the gravitational potential energy is released as neutrinos of all flavors. The remaining 1% is equal to 1044 J

References

  1. ^ Giacobbe, F. W. (2005). "How a Type II Supernova Explodes". Electronic Journal of Theoretical Physics 2 (6): 30–38, http://adsabs.harvard.edu/abs/2005EJTP....2f..30G. Retrieved on 3 August 2007.
  2. ^ "Introduction to Supernova Remnants". NASA Goddard Space Flight Center (July 27, 2006). Retrieved on 2006-09-07.

Further reading


External links


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