Video: Evolusi Bulan

Bumi dan Bulan dahulunya bermula dari Bola magma panas raksasa yang kemudian terpisah akibat tumbukan benda langit sebesar Mars yang kemudian masing-masing bagian membeku dan membentuk Bumi dan Bulan yang sekarang menjadi pasangan harmonis yang seiring dan sejalan mengelilingi Matahari. dan pada postingan sebelumnya saya sempat menulis mengapa hanya bagian Bulan berupa dataran lava yang disebut "Maria" yang terus menerus menghadap Bumi, bisa dibaca di sini.

Nah kali ini para ahli dari Goddard’s Scientific Visualization Studio membuat video perubahan wujud Bulan (evolusi) dari berbentuk Bola panas menjadi dingin dan membeku seperti sekarang, yang aslinya berlangsung dalam waktu 4.5 miliar tahun namun dalam video ini hanya 2.5 menit. Silahkan menyaksikan video berikut:

Read More

Kalender Astronomi 2012

Image credit: seasky.org

 Berikut adalah kalender astronomi tahun 2012 seperti yang dikutip dari www.seasky.org:

• January 3, 4 - Quadrantids Meteor Shower. The Quadrantids are an above average shower, with up to 40 meteors per hour at their peak. The shower usually peaks on January 3 & 4, but some meteors can be visible from January 1 - 5. The near first quarter moon will set shortly after midnight, leaving dark skies for what should be a good show. Best viewing will be from a dark location after midnight. Look for meteors radiating from the constellation Bootes.
  
• January 9 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 07:30 UTC.
  
• January 23 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 07:39 UTC.
  
• February 7 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 21:54 UTC.
  
• February 20 - March 12 - Best Chance to see Mercury. The planet Mercury will be far enough from the Sun's glare to be visible shortly after sunset. Mercury will reach greatest elongation from the Sun on March 5, reaching a relatively bright magnitude of about -1. This will be your best chance to see the planet this year.
  
• February 21 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 22:35 UTC.
  
• March 3 - Mars at Opposition. The red planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Mars.
  
• March 8 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 09:39 UTC.
  
• March 14 - Conjunction of Venus and Jupiter. The two brightest planets in the sky will be within 3 degrees of each other in the evening sky. On March 25 and 25, the crescent Moon will be near the two planets, creating a dazzling evening spectacle.
  
• March 20 - March Equinox. The March equinox occurs at 05:14 UTC. The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of spring (vernal equinox) in the northern hemisphere and the first day of fall (autumnal equinox) in the southern hemisphere.
  
• March 22 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 14:37 UTC.
  
• April 6 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 19:19 UTC.
  
• April 15 - Saturn at Opposition. The ringed planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Saturn and its moons.
  
• April 21 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 07:18 UTC.
  
• April 21, 22 - Lyrids Meteor Shower. The Lyrids are an average shower, usually producing about 20 meteors per hour at their peak. These meteors can produce bright dust trails that last for several seconds. The shower usually peaks on April 21 & 22, although some meteors can be visible from April 16 - 25. With no moon to get in the way this year, this really should be a good show. Look for meteors radiating from the constellation of Lyra after midnight.
  
• April 28 - Astronomy Day Part 1. Astronomy Day is an annual event intended to provide a means of interaction between the general public and various astronomy enthusiasts, groups and professionals. The theme of Astronomy Day is "Bringing Astronomy to the People," and on this day astronomy and stargazing clubs and other organizations around the world will plan special events. You can find out about special local events by contacting your local astronomy club or planetarium. You can also find more about Astronomy Day by checking the Web site for the Astronomical League.
  
• May 5, 6 - Eta Aquarids Meteor Shower. The Eta Aquarids are a light shower, usually producing about 10 meteors per hour at their peak. The shower's peak usually occurs on May 5 & 6, however viewing should be good on any morning from May 4 - 7. The full moon will probably ruin the show this year, washing out all but the brightest meteors with its glare. The radiant point for this shower will be in the constellation Aquarius. Best viewing is usually to the east after midnight, far from city lights.
  
• May 6 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 03:35 UTC. The Moon will be at its closest point to the Earth, so this will be the largest full moon of the year.
  
• May 20 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 23:47 UTC.
  
• May 20 - Annular Solar Eclipse. The path of annularity will begin in southern China and move east through Japan, the northern Pacific Ocean, and into the western United States. A partial eclipse will be visible throughout parts of eastern Asia and most of North America. (NASA Map and Eclipse Information)
  
• June 4 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 11:12 UTC.
  
• June 4 - Partial Lunar Eclipse. The eclipse will be visible throughout most of Asia, Australia, the Pacific Ocean, and the Americas. (NASA Map and Eclipse Information)
  
• June 5, 6 - Transit of Venus Across the Sun. This extremely rare event will be entirely visible throughout most of eastern Asia, eastern Australia, and Alaska. A partial transit can be seen in progress at sunrise throughout Europe, western Asia, and eastern Africa. A partial transit can be seen in progress at sunset throughout most of North America, Central America, and western South America. The next transit will not take place until the year 2117. (NASA Transit Information | NASA Transit Map)
  
• June 19 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 15:02 UTC.
  
• June 20 - June Solstice. The June solstice occurs at 23:09 UTC. The North Pole of the earth will be tilted toward the Sun, which will have reached its northernmost position in the sky and will be directly over the Tropic of Cancer at 23.44 degrees north latitude. This is the first day of summer (summer solstice) in the northern hemisphere and the first day of winter (winter solstice) in the southern hemisphere.
  
• July 3 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 18:52 UTC.
  
• July 19 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 04:24 UTC.
  
• July 28, 29 - Southern Delta Aquarids Meteor Shower. The Delta Aquarids can produce about 20 meteors per hour at their peak. The shower usually peaks on July 28 & 29, but some meteors can also be seen from July 18 - August 18. The radiant point for this shower will be in the constellation Aquarius. The near first quarter moon will set shortly after midnight, leaving dark skies for what should be a good show. Best viewing is usually to the east after midnight.
  
• August 2 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 03:27 UTC.
  
• August 6 - Curiosity Rover at Mars. NASA’s Mars Science Laboratory (MSL) is scheduled to land on the red planet between August 6 and August 20, 2012. Officially named Curiosity, it is an autonomous rover similar to the Spirit and Opportunity rovers that previously visited Mars. This much larger rover will carry many more instruments and experiments than its previous cousins. Curiosity’s high definition color cameras will photograph the Martian surface while a host of instruments will sample the soil and air and search for organic compounds.
  
• August 12, 13 - Perseids Meteor Shower. The Perseids is one of the best meteor showers to observe, producing up to 60 meteors per hour at their peak. The shower's peak usually occurs on August 13 & 14, but you may be able to see some meteors any time from July 23 - August 22. The radiant point for this shower will be in the constellation Perseus. The near last quarter moon will be hanging around for the show, but shouldn’t be too much of a problem for a shower with up to 60 meteors per hour. Find a location far from city lights and look to the northeast after midnight.
  
• August 17 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 15:54 UTC.
  
• August 24 - Neptune at Opposition. The blue planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view Neptune. Due to its distance, it will only appear as a tiny blue dot in all but the most powerful telescopes.
  
• August 31 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 13:58 UTC. Since this is the second full moon in the same month, it is known as a blue moon. This rare calendar event only happens once every few years, giving rise to the term, “once in a blue moon.”
  
• September 16 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 02:11 UTC.
  
• September 22 - September Equinox. The September equinox occurs at 14:49 UTC. The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of fall (autumnal equinox) in the northern hemisphere and the first day of spring (vernal equinox) in the southern hemisphere.
  
• September 29 - Uranus at Opposition. The blue-green planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view Uranus. Due to its distance, it will only appear as a tiny blue-green dot in all but the most powerful telescopes.
  
• September 30 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 03:19 UTC.
  
• October 20 - Astronomy Day Part 2. Astronomy Day is an annual event intended to provide a means of interaction between the general public and various astronomy enthusiasts, groups and professionals. The theme of Astronomy Day is "Bringing Astronomy to the People," and on this day astronomy and stargazing clubs and other organizations around the world will plan special events. You can find out about special local events by contacting your local astronomy club or planetarium. You can also find more about Astronomy Day by checking the Web site for the Astronomical League.
  
• October 15 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 12:02 UTC.
  
• October 21, 22 - Orionids Meteor Shower. The Orionids is an average shower producing about 20 meteors per hour at their peak. This shower usually peaks on the 21st, but it is highly irregular. A good show could be experienced on any morning from October 20 - 24, and some meteors may be seen any time from October 17 - 25. The first quarter moon will set by midnight, leaving a dark sky for what should be a good show. Best viewing will be to the east after midnight. Be sure to find a dark location far from city lights.
  
• October 29 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 19:49 UTC.
  
• November 13 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 22:08 UTC.
  
• November 13 - Total Solar Eclipse. The path of totality will only be visible in parts of extreme northern Australia and the southern Pacific Ocean. A partial eclipse will be visible in most parts of eastern Australia and New Zealand.
  (NASA Map and Eclipse Information)
  
• November 17, 18 - Leonids Meteor Shower. The Leonids is one of the better meteor showers to observe, producing an average of 40 meteors per hour at their peak. The shower itself has a cyclic peak year every 33 years where hundreds of meteors can be seen each hour. The last of these occurred in 2001. The shower usually peaks on November 17 & 18, but you may see some meteors from November 13 - 20. The crescent moon will set early in the evening leaving dark skies for what should be an excellent show. Look for the shower radiating from the constellation Leo after midnight, and be sure to find a dark location for viewing.
  
• November 27 - Conjunction of Venus and Saturn. These two bright planets will be within 1 degree of each other in the morning sky. Look to the east around sunrise.
  
• November 28 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 14:46 UTC.
  
• November 28 - Penumbral Lunar Eclipse. The eclipse will be visible throughout most of Europe, eastern Africa, Asia, Australia, the Pacific Ocean, and North America. (NASA Map and Eclipse Information)
  
• December 3 - Jupiter at Opposition. The giant planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. This is the best time to view and photograph Jupiter and its moons.
  
• December 13 - New Moon. The Moon will be directly between the Earth and the Sun and will not be visible from Earth. This phase occurs at 08:42 UTC.
  
• December 13, 14 - Geminids Meteor Shower. Considered by many to be the best meteor shower in the heavens, the Geminids are known for producing up to 60 multicolored meteors per hour at their peak. The peak of the shower usually occurs around December 13 & 14, although some meteors should be visible from December 6 - 19. The radiant point for this shower will be in the constellation Gemini. This year the new moon will guarantee a dark sky for what should be an awesome show. Best viewing is usually to the east after midnight from a dark location.
  
• December 21 - December Solstice. The December solstice occurs at 11:12 UTC. The South Pole of the earth will be tilted toward the Sun, which will have reached its southernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter (winter solstice) in the northern hemisphere and the first day of summer (summer solstice) in the southern hemisphere.
  
• December 28 - Full Moon. The Moon will be directly opposite the Earth from the Sun and will be fully illuminated as seen from Earth. This phase occurs at 10:21 UTC.
  

Read More

Sistem Tata Surya yang Mengorbit Dua Bintang

Tata surya yang mengorbit
dua bintang. Image credit: LYNETTE COOK

Penelitian yang dipresentasikan baru-baru ini pada pertemuan tahunan American Astronomical Society menunjukkan bahwa planet-planet sistem circumbinary, yaitu planet yang mengorbit dua bintang, bukanlah suatu hal yang jarang, bahkan mungkin juga terdapat dalam jumlah jutaan di Galaksi Bima Sakti sendiri.

Pada konferensi pers, William Welsh dari Universitas San Diego State menjelaskan bahwa Kepler 34b dan Kepler 35b, merupakan penambahan terbaru untuk kelas baru dari sistem planet. Penelitian ini diterbitkan dalam jurnal Nature edisi 12 Januari.

“Gerhana-gerhana bintang memungkinkan kita untuk mengukur sifat-sifat bintang-bintang dengan presisi yang indah, yang pada gilirannya memungkinkan kita untuk mengukur sifat planet,” tutur Welsh.

Transit (gerhana kecil) yang disebabkan oleh planet memberikan bukti definitif mengenai keberadaan planet, sedangkan gerhana-gerhana bintang besar memungkinkan para ilmuwan untuk mengukur sifat-sifat bintang dengan presisi. Hal ini, pada akhirnya, memungkinkan mereka untuk mengukur sifat planet.

Sekarang setelah ketiga sistem tersebut telah secara langsung diamati (Kepler 16b diumumkan pada September), para peneliti telah menemukan keragaman orbit bintang dan planet di kelas baru dari sistem planet, dan sangat ingin untuk menyelidiki bagaimana planet terbentuk di sekitar sepasang bintang.

Dengan dukungan dari National Science Foundation (NSF), tim peneliti Welsh akan terus mencari planet yang lebih banyak lagi, baik transit maupun non-transit. “Menemukan planet circumbinary jauh lebih sulit daripada menemukan planet yang mengorbit di sekitar bintang tunggal.” (erabaru.net, astronomi.us)

Read More

Penuh Dengan Samudera Lava, Permukaan Io Mirip Pizza

Bulan Jupiter, Io. Image credit: NASA

Ilmuwan NASA telah menemukan samudera lava pada permukaan sebuah bulan yang terlihat seperti pizza.
Io, yang mengorbit planet raksasa Yupiter adalah dunia yang mengalami vulkanik paling aktif dalam sistem tata surya.

Meskipun hanya seperempat diameter Bumi, namun bulan ini menghasilkan sekitar 100 kali lebih banyak lava dibandingkan semua gunung berapi di seluruh Bumi.

Kini para ilmuwan AS pada Universitas California dan Michigan telah menemukan bahwa lava yang mengalir dari lautan magma itu berada antara 20-30 mil di bawah permukaan Io dengan kedalaman lebih dari 30 mil.

Penampakan Io mirip pizza ini, diakibatkan karena materi pada permukaan yang terus menerus mengalir tersebut terlihat seperti noda jerawat.

Perputaran yang tanpa akhir ini disebabkan oleh tarikan sangat kuat Yupiter pada interior Io, mirip tarikan pasang pada bulan kita.

Vulkanik Io mengejutkan sejumlah astronom ketika pertama kali difoto oleh NASA pada akhir 1970.

Lautan lava dideteksi dengan data penganalisaan yang dikumpulkan oleh pengamat lain, Galileo, yang mengorbit Yupiter selama delapan tahun hingga 2003 lalu.

Sinyal misterius dalam temuan ini terdengar cocok dengan apa yang diperkirakan dari bebatuan yang meleleh di bawah permukaan Io.

Para ilmuwan bahkan mampu mengidentifikasi beberapa jenis bebatuan, yang terungkap seperti lherzolite, sebuah batu vulkanik yang ditemukan di Spitzbergen, Swedia.

Torrence Johnson, mantan ilmuwan pada proyek Galileo, dari Jet Propulsion Laboratory NASA, di California, mengatakan, “Antara Bumi dan bulan kemungkinan juga pernah memiliki lautan magma serupa beberapa milyar tahun lalu pada saat pembentukannya, namun sudah lama mengalami pendinginan.”

“Vulkanik Io menginformasikan kepada kita bagaimana gunung berapi bekerja dan menyajikan sebuah jendela pada saat terjadinya berbagai jenis aktifitas vulkanik yang kemungkinan terjadi di Bumi dan bulan selama sejarah awal pembentukannya.”(erabaru.net, astronomi.us)

Read More

Venus dan Jupiter Akan Muncul Berpasangan Hingga 17 Maret

Venus dan Jupiter yang sebenarnya berada pada jarak yang berbeda tampak seolah-olah berdampingan. Image credit: Shawn Malone

Planet Jupiter dan Venus, muncul secara berpasangan dalam beberapa hari mendatang mulai Minggu 11 Maret 2012, waktu Amerika Serikat, atau Senin WIB, 12 Maret 2012 hingga 17 Maret. Walaupun dalam sitem tata surya, kedua planet tersebut berjarak sangat jauh, namun pada kemunculannya, terlihat hanya berjarak dua jari manusia.

Fenomena ini dapat disaksikan di sebelah barat daya, sesaat setelah matahari tenggelam. Venus akan bersinar lebih terang dibandingkan dengan Jupiter. Jupiter muncul di dalam satu garis lintasan, sepanjang bulan Maret ini.

Ini adalah periode rutin bagi kedua planet tersebut. Pada Sein, 5 Maret 2012, Planet Mars berada di titik paling dekat dengan bumi dalam dua tahun terakhir.

Kemunculan benda langit lainnya adalah pergerakan bulan yang seolah menari dalam orbitnya pada akhir Maret. Bulan akan bergerak mendekati Jupiter, kemudian Venus.

Peristiwa alam yang paling ditunggu di tahun ini adalah Venus yang akan terlihat di sejumlah wilayah di bumi. Planet tersebut akan melintas dekat matahari. (tempo.com, astronomi.us)

Read More

Bintang Terbesar Dalam Sistem Bintang Ganda Eta Carinae Siap Meledak

Bintang terbesar dalam sistem bintang ganda Eta Carinae yang siap meledak dalam bentuk supernova. Image credit: ESA/Hubble & NASA

Bintang terbesar dalam sistem bintang ganda Eta Carinae yang merupakan bintang terbesar dan tidak stabil yang mendekati akhir masa hidupnya. Sekira 150 tahun yang lalu bintang tersebut memancarkan materi berupa awan besar dalam bentuk khas yang dikenal sebagai Nebula Homunculus. Eta Carinae adalah salah satu bintang terdekat dengan Bumi yang akan meledak dalam supernova dalam waktu yang relatif dekat (kira-kira satu juta tahun ke depan). (Adi Saputro/astronomi.us)

Read More

5000 Gelembung Angkasa Ditemukan Astronom Amatir di Galaksi Bima Sakti

5000 gelembung angkasa di Galaksi Bimasakti ditemukan oleh amatir. Gelembung angkasa tersebut menandakan bahwa Bimsakti adalah area pembentukan bintang yang aktif. Image credit: NASA

Sebanyak 5000 gelembung angkasa ditemukan di Galaksi Bimasakti oleh tim yang terdiri dari ilmuwan amatir. Gelembung-gelembung itu berkaitan dengan bintang muda dan panas. Banyaknya gelembung yang ada menandakan bahwa Bimsakati merupakan tempat pembentukan bintang yang jauh lebih aktif dari yang diduga.

"Piringan Bimsakati seperti champagne dengan gelembung-gelmbung di semua sisinya," ungkap Eli Bresselt, mahasiswa doktoral yang melakukan penelitian di European Southern Observatory (ESO).

Penemuan 5000 gelembung angkasa ini melibatkan 35.000 sukarelawan yang tergabung dalam Proyek Bimasakti. Observasi dilakukan dengan Spitzer Space Telescope milik NASA. Seperti diberitakan Space, Jumat (9/3/2012), jumlah gelembung yang ditemukan 10 kali lebih banyak yang yang diperkirakan.

Pimpinan investigasi Proyek Bimasakati, Robert Simpson dari Oxford University, mengatakan, "Proyek Bimasakti adalah upaya untuk melihat data yang banyak dan indah dari Spitzer serta mengekstrak informasi secara menyenangkan, online dan melibatkan publik."

Dalam observasi, ilmuwan amatir diminta memberi tanda bendera pada gelembung yang ditemukan. Gelembung akan dikatalogkan jika telah ada minimal 5 orang yang menandai gelembung yang sama.

Berdasarkan penemuan, ilmuwan mengungkapkan bahwa gelembung lebih jarang ditemukan di tepian galaksi. "Kami memperkirakan bahwa pembentukan bintang paling banyak terjadi di pusat galaksi karena di sanalah gas bermassa jenis tinggi terdapat. Proyek ini mengungkap lebih banyak pertanyaan daripada jawaban," kata Bressert.

Hasil studi telah dimasukkan ke jurnal Monthly Notice of the Royal Astronomical Society.(kompas.com, astronomi.us)

Read More

Mengapa Bagian Bulan yang Terlihat Dari Bumi Selalu Sama?

Penampakan dua sisi Bulan yang berbeda. Image credit: LRO

Ketika kita melihat Bulan, kita melihat variasi yang menakjubkan dari bagian yang terang dan gelap, tergantung pada posisi Anda di Bumi, Anda mungkin melihat Man in the Moon”, or maybe the “Rabbit in the Moon”, Daerah gelap yang dikenal sebagai maria, yaitu bidang lava halus yang diciptakan oleh letusan gunung berapi kuno di Bulan.

Tapi mengapa kita melihat bagian sisi maria tersebut dan bukan pada sisi yang lain?

Rotasi Bulan yang pasang surut terkunci dengan Bumi. Ini berarti bahwa Bulan selalu menghadirkan sisi yang sama kepada kita Dan sebelum era antariksa, diasumsikan bahwa seluruh sisi bulan seperti ini. Ketika pesawat ruang angkasa pertama dikirim dari Bumi untuk mengorbit Bulan, mereka mengirimkan foto-foto mengejutkan yang mengungkapkan pemandangan yang sama sekali berbeda dari apa yang kita biasa kita lihat. Bukan bercak gelap maria yang biasa kita lihat

Jadi mengapa sisi maria yang menghadap Bumi kita dan bukan sisi yang lain? Apakah itu hanya kebetulan?

Seperti yang di lansir dari universetoday.com, Rabu (14/03/2012), Peneliti dari California Institute of Technology (Caltech) berpikir bahwa ini bukan tentang keberuntungan sama sekali, tapi cara rotasi Bulan yang melambat setelah pembentukannya. Oded Aharonson, seorang profesor ilmu planet di Caltech, dan timnya menciptakan sebuah simulasi yang menghitung bagaimana rotasi Bulan melambat setelah pembentukannya.

Meskipun Bulan terlihat seperti bola, sebenarnya ia memiliki sedikit tonjolan. Dan miliaran tahun yang lalu, saat Bulan sedang berputar jauh lebih cepat, Seluruh sisi Bulan bisa terlihat dari Bumi, namun gravitasi bumi menarik-narik tonjolan ini dengan rotasi masing-masing dan membuat rotasi Bulan menurun sedikit sampai akhirnya berhenti dan yang menghadap Bumi adalah sisi maria.

Dalam setiap simulasi yang dilakukan berkat orientasi tonjolan bulan ini, sisi Maria atau sisi kawah akhirnya menghadap Bumi. Tapi tingkat di mana ia melambat seberapa cepat hilangnya energi rotasi menjelaskan mengapa hal tersebut bisa terjadi.

Jika Bulan melambat dengan cepat, maka peluangnya 50/50. Tapi karena Bulan melambat secara bertahap, kita memiliki kesempatan yang jauh lebih tinggi melihat sisi maria Bulan sebagai hasil akhir. Hasil penelitian ini diterbitkan dalam edisi 27 Februari dari Icarus Journal. (Adi Saputro/astronomi.us)

Read More