James Webb Space Telescope Science

Webb Science
 

The James Webb Space Telescope will be a giant leap forward in our quest to understand the Universe and our origins.  The Webb will examine every phase of cosmic history: from the first luminous glows after the Big Bang to the formation of galaxies, stars, and planets to the evolution of our own solar system.  The science goals for the Webb can be grouped into four themes:

The End of the Dark Ages: First Light and Reionization seeks to identify the first bright objects that formed in the early Universe, and follow the ionization history.

Assembly of Galaxies will determine how galaxies and dark matter, including gas, stars, metals, physical structures (like spiral arms) and active nuclei evolved to the present day.

The Birth of Stars and Protoplanetary Systems focuses on the birth and early development of stars and the formation of planets.

Planetary Systems and the Origins of Life studies the physical and chemical properties of solar systems (including our own) and where the building blocks of life may be present.

The observations needed to accomplish these goals require a telescope that can study the Universe in infrared light.  For this, it needs to be cooled till it is just a few tens of degrees above Absolute Zero.  To accomplish this goal, the Webb will reside far from the Earth at the L2 region.  Why does Webb need to be at L2?

We now have a series of videos that highlight the science that will be peformed by the James Webb Space Telescope.

A detailed description of the science capabilities and instruments on Webb can be found in the Space Science Reviews paper by Gardner et. al.

Arip Nurahman

Guru dan Dosen Profesional, amin cita-citaku

Chandra X-ray Observatory

"I am aware of the usefulness of science to society and of the benefits society derives from it."

~Subrahmanyan Chandrasekhar~

Chandra X-ray Observatory

Chandra X-ray Observatory and Inertial Upper Stage sit inside the payload bay on Space ShuttleColumbia mission STS-93
General information
NSSDC ID	1999-040B
Organization	NASA, SAO, CXC
Major contractors	TRW, Northrop Grumman
Launch date	23 July 1999
Launched from	Kennedy Space Center
Launch vehicle	Space Shuttle Columbia STS-93
Mission length	planned: 5 years[1] elapsed: 12 years and 13 days
Mass	4,790 kg (10,600 lb)
Orbit height	apogee 133,000 km (83,000 mi) perigee 16,000 km (9,900 mi)
Orbit period	64.2 hours
Wavelength	X-ray (0.1 - 10 keV)
Diameter	1.2 m (3.9 ft)
Collecting area	0.04 m2 (0.43 sq ft) at 1 keV
Focal length	10 m (33 ft)
Instruments
Website	chandra.harvard.edu

The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit.

Chandra Observatory is the third of NASA's four Great Observatories. The first was Hubble Space Telescope; second the Compton Gamma Ray Observatory, launched in 1991; and last is the Spitzer Space Telescope. Prior to successful launch, the Chandra Observatory was known as AXAF, the Advanced X-ray Astrophysics Facility. 


AXAF was assembled and tested by TRW (now Northrop Grumman Aerospace Systems) in Redondo Beach, California. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, due primarily to the high angular resolution of the Chandra mirrors.

Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes, requiring a space-based telescope to make these observations.

In 1976 the Chandra X-ray Observatory (called AXAF at the time) was proposed to NASA by Riccardo Giacconi and Harvey Tananbaum. Preliminary work began the following year at Marshall Space Flight Center (MSFC) and the Smithsonian Astrophysical Observatory (SAO). In the meantime, in 1978, NASA launched the first imaging X-ray telescope, Einstein (HEAO-2), into orbit. 

Work continued on the Chandra project through the 1980's and 1990's. In 1992, to reduce costs, the spacecraft was redesigned. Four of the twelve planned mirrors were eliminated, as were two of the six scientific instruments. Chandra's planned orbit was changed to an elliptical one, reaching one third of the way to the Moon's at its farthest point. This eliminated the possibility of improvement or repair by the space shuttle but put the observatory above the Earth's radiation belts for most of its orbit.

AXAF was renamed Chandra in 1998 and launched in 1999 by the shuttle Columbia (STS-93). At 22753 kg, it was the heaviest payload ever launched by the shuttle, a consequence of the two-stage Inertial Upper Stage booster rocket system needed to transport the spacecraft to its high orbit.

Chandra has been returning data since the month after it launched. It is operated by the SAO at the Chandra X-ray Center in Cambridge, Massachusetts, with assistance from MIT and Northrop Grumman Space Technology. The ACIS CCDs suffered particle damage during early radiation belt passages. To prevent further damage, the instrument is now removed from the telescope's focal plane during passages.

In 2004 Chandra celebrated its fifth year of operation.

Technical description

 

 

Unlike optical telescopes which possess simple aluminized parabolic surfaces (mirrors), X-ray telescopes generally use a Wolter telescope consisting of nested cylindrical paraboloid and hyperboloid surfaces coated with iridium or gold. X-ray photons would be absorbed by normal mirror surfaces, so mirrors with a low grazing angle are necessary to reflect them. Chandra uses four pairs of nested mirrors, together with their support structure, called the High Resolution Mirror Assembly (HRMA); the mirror substrate is 2 cm-thick glass, with the reflecting surface a 33 nm iridium coating, and the diameters are 65 cm, 87 cm, 99 cm and 123 cm.

The thick substrate and particularly careful polishing allowed a very precise optical surface, which is responsible for Chandra's unmatched resolution: between 80% and 95% of the incoming X-ray energy is focused into a one-arcsecond circle. However, the thickness of the substrates limit the proportion of the aperture which is filled, leading to the low collecting area compared to XMM-Newton.

Chandra's highly elliptical orbit allows it to observe continuously for up to 55 hours of its 65 hour orbital period. At its furthest orbital point from earth, Chandra is one of the furthest from earth earth-orbiting satellites. This orbit takes it beyond the geostationary satellites and beyond the outer Van Allen belt.

With an angular resolution of 0.5 arcsecond (2.4 µrad), Chandra possesses a resolution over 1000 times better than that of the first orbiting X-ray telescope.

Instruments

The Science Instrument Module (SIM) holds the two focal plane instruments, the Advanced CCD Imaging Spectrometer (ACIS) and the High Resolution Camera (HRC), moving whichever is called for into position during an observation.

ACIS consists of 10 CCD chips and provides images as well as spectral information of the object observed. It operates in the range of 0.2–10 keV. HRC has two micro-channel plate components and images over the range of 0.1–10 keV. It also has a time resolution of 16 microseconds. Both of these instruments can be used on their own or in conjunction with one of the observatory's two transmission gratings.

The transmission gratings, which swing into the optical path behind the mirrors, provide Chandra with high resolution spectroscopy. The High Energy Transmission Grating Spectrometer (HETGS) works over 0.4–10 keV and has a spectral resolution of 60–1000. The Low Energy Transmission Grating Spectrometer (LETGS) has a range of 0.09–3 keV and a resolution of 40–2000.

Discoveries

SN 2006gy (upper right) and its parent galaxy NGC 1260 (lower left) in false color as observed through the Chandra X-Ray Observatory.

In this image of PSR B1509-58, the lowest energy X-rays that Chandra detects are red, the medium range is green, and the most energetic ones are colored blue.

The data gathered by Chandra have greatly advanced the field of X-ray astronomy.

• The first light image, of supernova remnant Cassiopeia A, gave astronomers their first glimpse of the compact object at the center of the remnant, probably a neutron star or black hole. (Pavlov, et al., 2000)
• In the Crab Nebula, another supernova remnant, Chandra showed a never-before-seen ring around the central pulsar and jets that had only been partially seen by earlier telescopes. (Weisskopf, et al., 2000)
• The first X-ray emission was seen from the supermassive black hole, Sagittarius A*, at thecenter of the Milky Way. (Baganoff, et al., 2001)
• Chandra found much more cool gas than expected spiralling into the center of the Andromeda Galaxy.
• Pressure fronts were observed in detail for the first time in Abell 2142, where clusters of galaxies are merging.
• The earliest images in X-rays of the shock wave of a supernova were taken of SN 1987A.
• Chandra showed for the first time the shadow of a small galaxy as it is being cannibalized by a larger one, in an image of Perseus A.
• A new type of black hole was discovered in galaxy M82, mid-mass objects purported to be the missing link between stellar-sized black holes and supermassive black holes. (Griffiths, et al., 2000)
• X-ray emission lines were associated for the first time with a gamma-ray burst, Beethoven Burst GRB 991216. (Piro, et al., 2000)
• High school students, using Chandra data, discovered a neutron star in supernova remnant IC 443.
• Observations by Chandra and BeppoSAX suggest that gamma-ray bursts occur in star-forming regions.
• Chandra data suggested that RX J1856.5-3754 and 3C58, previously thought to be pulsars, might be even denser objects: quark stars. These results are still debated.
• Sound waves from violent activity around a supermassive black hole were observed in the Perseus Cluster (2003).
• TWA 5B, a brown dwarf, was seen orbiting a binary system of Sun-like stars.
• Nearly all stars on the main sequence are X-ray emitters. (Schmitt & Liefke, 2004)
• The X-ray shadow of Titan was seen when it transitted the Crab Nebula.
• X-ray emissions from materials falling from a protoplanetary disc into a star. (Kastner, et al., 2004)
• Hubble constant measured to be 76.9 km/s/Mpc using Sunyaev-Zel'dovich effect.
• 2006 Chandra found strong evidence that dark matter exists by observing supercluster collision
• 2006 X-ray emitting loops, rings and filaments discovered around a supermassive black hole within Messier 87 imply the presence of pressure waves, shock waves and sound waves. The evolution of Messier 87 may have been dramatically affected.^[6]
• Observations of the Bullet cluster put limits on the cross-section of the self-interaction of dark matter.^[7]
• "The Hand of God" photograph of PSR B1509-58.

Informal Education

• Background
  
  • Galactic Navigation
  • Take a tour of the Galactic Coordinate System.
  • Chandra 101
    Overview of X-ray astronomy and the Chandra mission.
  • False Color
  • X-ray Images 101
  • Chandra Top Ten
    Top Ten Amazing Facts about Chandra!
  • Ask an Astrophysicist
    View the Q & A page & ask questions about the X-ray universe.
  • Tracking Chandra
    Follow this tutorial to see the Chandra orbit.
• Interactive Games, Activities & Quizzes
  Educational Word Searches, Puzzles, Memory, and other games, activities & quizzes based on the Chandra Mission and X-ray Astronomy.
• Chandra Podcasts
  Audio & video features showcasing the Chandra mission and X-ray Astronomy.
  • The Beautiful Universe (HD)
    High definition audio/video versions of Chandra's exciting science viewable on your computer or television.
  • Chandra Podcasts (SD)
    Audio/video content in standard definition perfect for your portable MP3 player
  • Touch the Invisible Sky
    Audio recordings from NASA's Braille book "Touch the Invisible Sky"
  • Incredible Two-Inch Universe
    Explore the universe by shrinking cosmic scale in 4 steps (Audio & American Sign Language)
• Printable Materials
  • Printable 2011 Chandra Calendar
    Print your own 2011 Chandra calendar!
  • Printable Activities
    Coloring Book, Tracking Chandra, Trading Cards, more.
  • Printable Games
    Crossword puzzles, word searches, jumbles, more.
  • Chandra Image Handouts
    Chandra images with short captions.
  • Chandra Lithographs
    2-sided printable handouts.
• Links & Resources - A list of links and other resources for science education.
• Resources for Outreach and Education
  • Resources for museums, planetariums,
    broadcast producers & other special venues
• Resource Request Form
• Evaluation & Comments
  • Educators' Comments
  • Evaluation Form
• Chandra Education Proposals: Cycle 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10

Sumber:

1. Wikipedia

2. Harvard University
3. http://chandra.si.edu/
4. http://cxc.harvard.edu/
5  http://www.nasa.gov/mission_pages/chandra/main/index.html

Disusun Ulang Oleh:

Arip Nurahman

Terima Kasih Semoga bermanfaat

Mengenal Prof. Subrahmanyan Chandrasekhar

Chandrasekhar Fisikawan Ahli Bahasa 

Subramanyan Chandrasekhar, peraih nobel Fisika tahun 1983 dilahirkan di Lahore, India pada 19 Oktober 1910. Ayahnya, Chandrasekhara Subrahmanyan Ayyar adalah pegawai di departemen keuangan India. Sementara Ibunya, Sita (neé Balakrishnan) seorang ibu rumah tangga biasa namun berintelektual tinggi (ia mampu menerjemahan karya Henrik Ibsen, “A Doll House” ke bahasa Tamil). 

Kedua orangtuanya, menurut Chandrasekhar sangat menaruh perhatian pada pendidikan anak-anaknya. Orangtuanyalah yang langsung memberikan pendidikan dasar khusus baginya di rumah hingga ia berusia 12 tahun. 

Mereka mengharapkan Chandrasekhar terkenal seperti pamannya, Chandrasekhara V. Raman, orang India pertama yang meraih hadiah Nobel fisika. Pada tahun 1918, ayahnya dipindah tugaskan ke Madras dan di sanalah keluarganya kemudian hidup menetap.

Di Madras, ia bersekolah di sekolah lanjutan Hindu dari 1922 hingga 1925. Pendidikan tingginya (1925-30) ia peroleh pertama kali di Presidency College. Kemudian ketika hendak melanjutkan studinya ke Universitas Cambridge, ibunya jatuh sakit.

Subrahmanyan Chandrasekhar
Subrahmanyan Chandrasekhar
Born	(1910-10-19)October 19, 1910 Lahore, British India
Died	August 21, 1995(1995-08-21) (aged 84) Chicago, Illinois, United States
Residence	United States
Citizenship	India (1910–1953) United States (1953–1995)
Fields	Astrophysics
Institutions	University of Chicago University of Cambridge
Alma mater	Presidency College, Madras Trinity College, Cambridge
Doctoral advisor	R.H. Fowler, Arthur Stanley Eddington
Doctoral students	Donald Edward Osterbrock, Roland Winston, F. Paul Esposito, Jeremiah P. Ostriker
Known for	Chandrasekhar limit
Notable awards	Nobel Prize in Physics (1983) Copley Medal (1984) National Medal of Science (1966) Padma Vibhushan (1968)

Early life and education

 

 

 

Chandrasekhar was born on 19 October 1910 in Lahore, Punjab, India to a Tamil Iyer family Sitalakshmi (1891–1931) and Chandrasekhara Subrahmanya Iyer (1885–1960) who was posted in Lahore as Deputy Auditor General of the Northwestern Railways at the time of Chandrasekhar's birth. He was the eldest of their four sons and the third of their ten children. His paternal uncle was the Indian physicist and Nobel laureate C. V. Raman. C. S. Iyer. His mother was devoted to intellectual pursuits, had translated Henrik Ibsen's A Doll's House into Tamil and is credited with arousing Chandra's intellectual curiosity at an early age.

Chandrasekhar was tutored at home initially through middle school and later attended the Hindu High School, Triplicane, Madras during the years 1922-25. Subsequently, he studied at Presidency College, Madras from 1925 to 1930, writing his first paper, "The Compton Scattering and the New Statistics", in 1929 upon inspiration from a lecture by Arnold Sommerfeld and obtaining his bachelor's degree, B.Sc. (Hon.), in physics in June 1930.


In July 1930, Chandrasekhar was awarded a Government of India scholarship to pursue graduate studies at the University of Cambridge, where he was admitted to Trinity College, secured by Professor R. H. Fowler with whom he communicated his first paper. During his travels to England, Chandrasekhar spent his time working out the statistical mechanics of the degenerate electron gas in white dwarf stars, providing relativistic corrections to Fowler's previous work (see Legacy below).


In his first year at Cambridge, as a research student of Fowler, Chandrasekhar spent his time in intensive study, calculating mean opacities and applying his results to the construction of an improved model for the limiting mass of the degenerate star, and was introduced to the monthly meetings of the Royal Astronomical Society, where he met Professor E. A. Milne. At the invitation of Max Born he spent the summer of 1931, his second year of post-graduate studies, at Born’s institute at Göttingen, working on opacities, atomic absorption coefficients, and model stellar photospheres. On the advice of Prof. P. A. M. Dirac, he spent his final year of graduate studies at the Institute for Theoretical Physics in Copenhagen, where he met Prof. Niels Bohr.


After receiving a bronze medal for his work on degenerate stars, in the summer of 1933, Chandrasekhar was awarded his PhD degree at Cambridge with a thesis among his four papers on rotating self-gravitating polytropes, and the following October, he was elected to a Prize Fellowship at Trinity College for the period 1933-37. During this time, he made acquaintance with Sir Arthur Eddington. Chandrasekhar married Lalitha Doraiswamy in September 1936. He had met her as a fellow student, a year junior to him, at Presidency College, Madras. In his Nobel autobiography, Chandrasekhar wrote, "Lalitha's patient understanding, support, and encouragement have been the central facts of my life."




Chandrasekhar's infamous encounter with Arthur Eddington in 1935, in which the latter publicly ridiculed Chandra's most famous (and ultimately correct) discovery (see Chandrasekhar limit) led Chandra to consider employment outside of the U.K. (Later in life, Chandra on multiple occasions, expressed the view that Eddington's behavior was in part racially motivated.)


Masa Kuliah di Universitas Cambridge



Menurut tradisi India, ia harus tinggal di rumah merawat ibunya. Namun ibunya yang ingin anaknya sukses mendesak Chandra (nama kecil Chandrasekhar) untuk tetap pergi ke Cambridge, Inggris. 

Selama perjalanan panjang dengan kapal laut ke Inggris, Chandra mencoba menggabungkan pengetahuannya tentang bintang Bajang putih (white dwarf) dengan teori relativistik spesial, ia terkejut sekali mendapatkan hasil bahwa suatu bintang bajang putih dapat terbentuk melalui evolusi bintang, asalkan massa bintang itu kurang dari 1,45 massa matahari. 

Jika bintang terlalu berat maka gaya tolak akibat larangan Pauli tidak mampu menahan gaya gravitasi bintang, akibatnya bintang akan kolaps menjadi bintang netron atau bahkan menjadi lubang hitam (black hole). 

Tiba di Universitas Cambridge, dengan beasiswa penuh dari pemerintah India, Chandrasekhar menjadi mahasiswa peneliti di bawah bimbingan Profesor R.H. Fowler. Di tengah-tengah kesibukannya, Chandrasekhar masih ingat hasil perhitungannya di kapal laut itu. 

Ia mencoba menghitung ulang dan mendiskusikannya dengan para fisikawan di Cambridge, ternyata ia mendapatkan hasil yang sama bahwa ada batas atas massa bintang agar dapat berevolusi menjadi bintang bajang putih. 

Batas atas ini kemudian terkenal dengan nama “Chandrasekhar limit”. Karena hasil penelitian mengenai evolusi bintang inilah, 50 tahun kemudian Chandrasekhar dianugerahi hadiah nobel fisika (1983). 

Chandrasekhar sempat menghabiskan tahun ketiga masa kuliahnya di institut fisika teori, Copenhagen atas saran P.A.M. Dirac (pelopor fisika kuantum) yang melihat kemampuannya yang cemerlang. Pada tahun 1933, ia memperoleh gelar Ph.D dari Cambridge. 

Hanya beberapa bulan berselang, ia bergabung dengan Trinity College hingga tahun 1937. Ketika melakukan kunjungan ke Universitas Harvard, atas undangan Dr. Harlow Shapley selama musim dingin (Januari-Maret 1936), ia ditawari posisi sebagai peneliti di Universitas Chicago dan memutuskan menerima tawaran itu pada Januari 1937. 

Saat berada di Chicago, iapun melengkapi teorinya dan mempublikasikannya dalam buku An Introduction to the Study of Stellar Structure (1939). 

Riset bagi Chandrasekhar memang merupakan kerja berkesinambungan. 

Ia mencatat ada tujuh periode riset dalam hidupnya. 

Pertama, teori tentang struktur bintang, termasuk mengenai Bajang Putih (1929-39). 

Kedua, teori gerak Brownian yang merupakan bagian dari dinamika bintang (1938-43). 

Ketiga, teori tentang transfer energi, termasuk tentang atmosfer bintang dan teori kuantum ion negatif hidrogen, juga tentang atmosfer bintang (1943-50). 

Keempat, stabilitas hidrodinamika dan hidromagnetik (1953-61). 

Kelima, keseimbangan dan stabilitas bentuk elips, bagian dari kolaborasinya dengan Norman R Lebovitz (1961-8). Keenam, teori relativitas umum dan astrofisika relativitas (1962-71). 

Terakhir, teori matematika Black Holes (1974-83). Hasil penelitiannya itu dipublikasikan dalam berbagai monograf dan jurnal terkenal untuk astrofisika dan fisika.. 

Pimpinan Universitas Chicago, Hanna Gray pernah mengungkapkan kesannya terhadap Chandrasekhar. Profesor bidang astronomi dan astrofisika ini adalah ilmuwan yang penuh dedikasi, guru dari para guru, seseorang yang senantiasa membaktikan dirinya untuk kreativitas dunia ilmiah. 

Disamping fisika, Chandrasekhar juga menyukai bahasa Inggris dan senang membaca karya-karya sastra terkenal tulisan Shakespeare. 

Orang sangat mengagumi bahasa inggrisnya yang sangat sempurna baik dalam tata bahasa maupun aksennya, sampai-sampai fisikawan terkenal Hans Bethe mengatakan: 

"Chandrasekhar was one of the great astrophysicists of our time. He was also the greatest master of the English language that I know”. 

Sumber: Prof. Yohanes Surya, Ph.D.