Perkenalan Musytari

Perkenalan pendek ke Musytari.

Musytari adalah "planet raksasa"sistem kami, banyaknya yang sebagian besar melebihi yang dipunyai semua dari planet yang lain bergabung. Jupiters berarti garis tengah adalah sekitar 85.000 mil; tetapi berutang sampai pergiliran kilatnya atas porosnya ,nya khatulistiwa melebihi garis tengah kutubnya oleh 5000 mil. Di volume dia melebihi tanah kami sekitar 1300 kali, sedangkan di massa dia melebihinya sekitar 213 kali. Gravitasi spesifiknya ialah, oleh karena itu, jauh kurang dari yang dipunyai tanah, dan makin sedikit lagi daripada yang dipunyai air. Jarak pelitnya dari matahari adalah 480 jutaan mil, tetapi, berutang sampai kenyentrikan orbitnya, jarak sebenarnyanya bervariasi di antara 457 kersang 503 ion pabrik. Masanya perubahan total ialah lima puluh hari kurang dari dua belas tahun.

Permukaan Musytari

Kecuali matahari dan bulan, tidak ada objek sistem kami yang mempunyai selama yang terakhir sedikit tahun subyek lebih hati-hati ujian daripada planet ini. Tidak seperti Marikh, tidak ada tanda yang benar-benar permanen di atas permukaannya, dan sehelai peta Musytari ialah oleh karena itu mustahil. Tetapi permukaan ini selalu menimbulkan penampilan yang sangat berjenis-jenis. Pengamat teleskopis yang lebih awal menggambarkan ikat pinggang ringan dan gelap sebagai memanjang di seberang itu. Sampai periode yang cukup belakangan, sudah biasa menggambarkan ikat pinggang ini sebagai dua di bilangan, satu utara khatulistiwa, dan selatan yang lain itu. Secara umum, mereka dilihat sebagai gerombolan-gerombolan gelap di atas cakra terang planet; tetapi ingin tahu bahwa Huyghens mewakili mereka selebih terang daripada sisa permukaan. Seteleskopis tenaga di berkerut, dilihat bahwa gerombolan-gerombolan ini yang apa yang dinamakan struktur yang jauh lebih kompleks daripada sudah disangka benar, dan terdiri atas penampilan bentuk yang paling beraneka warna yang seperti awan yang bertingkat-tingkat banyak. Bentuk ini menukarkan begitu kilat itu muka planet hampir tidak pernah memberikan yang sama muncul ance pada dua malam berikut. Mereka kebanyakan sangat dapat dilihat di suatu jarak di masing-masing pihak khatulistiwa Jovian, dan demikian menimbulkan penampilan sebanyak dua helai ikat pinggang kalau teleskop yang sangat kecil atau tidak sempurna bekas.


Baik garis besar 'of ikat pinggang ini maupun warna beberapa bagian planet, kelihatannya subyek sampai ganti sungguh-sungguh. Daerah khatulistiwa, dan memang tempat di antara ikat pinggang secara umum, sering cercah yang merah merona. Warna ini ialah beberapa kali oleh sebab itu sangat dapat dilihat sebagai untuk menjadi nampak ke yang paling super ficial pengamat, sedangkan di kali lain hampir tidak jejak itu bisa dimengerti.

Tempat yang ialah lebih banyak lagi permanen daripada tanda biasa di atas ikat pinggang kadang-kadang kelihatan. Dengan menonton tempat ini dari hari ke hari, dan mengukur jarak mereka dari cakra nyata, masa pergiliran Musytari atas porosnya sudah gigih. Secara umum tempat adalah kegelapan; tetapi atas beberapa kesempatan yang agak langka planet dilihat dengan sejumlah tempat terang yang bulat yang kecil seperti satelit. Tempat terang ini tak ada keterangan sudah diberi.

From the changeability of the belts, and indeed of nearly all the visible features on the surface of Jupiter, it is clear that what we see on that planet is not the surface of a solid nu cleus, but vaporous or cloud-like formations which cover the entire surface and extend to a great depth below. To all ap pearance, the planet is covered with a deep and dense atmosphere, through which light cannot penetrate on account of thick masses of clouds and vapor. In the arrangements of these clouds in streaks parallel to the equator, and in the change of their forms with the latitude, there may be some thing analogous to the zones of clouds and rain on the earth. But of late years it has been noticed that the physical consti tution of Jupiter seems to offer more analogies to that of the sun than to that of the earth. Like the sun, he is brighter in the centre than near the edges. This is shown in the most striking manner in the transits of his satellites over his disk. When the satellite first enters on the disk, it commonly seems like a bright spot on a dark background ; but as it approaches the centre, it appears like a dark spot on the bright back ground of the planet. The brightness of the centre is prob ably two or three times greater than that of the limb. This diminution of light towards the edge may arise, as in the case of the sun, from the light near the edge passing through a greater depth of atmosphere, and thus becoming fainter by absorption.

A still more remarkable resemblance to the sun has some times been suspected nothing less, in fact, than that Jupiter shines partly by his own light. It was at one time supposed that he actually emitted more light than fell upon him from the sun ; and if this were proved, it would show conclusive ly that he was self-luminous. If all the light which the sun shed upon the planet were equally reflected in every direction, we might speak with some certainty on this question ; but in the actual state of our knowledge we cannot. Zollner has found that the brightness of Jupiter may be accounted for by supposing him to reflect 62 per cent, of the sunlight which he receives. But if this is his average reflecting power, the re flecting power of his brighter portions must be much greater; in fact, they are so bright that they must shine partly by their own light, unless they reflect a disproportionate share of the sunlight back in the direction of the earth and sun. Clouds would not be likely to do this. On the other hand, if we as sume that the planet emits any great amount of light, we are met by the fact that, if this were the case, the satellites would shine by this light when they were in the shadow of the planet. As these bodies totally disappear in this position, the quantity of light emitted by Jupiter must be quite small. On the whole, there is a small probability that the brighter spots of this planet are from time to time slightly self-luminous.

Again, the interior of Jupiter seems to be the seat of an activity so enormous that we can attribute it only to a very high temperature, like that of the sun. This is shown by the rapid movements always going on in his visible surface, which frequently changes its aspect in a few hours. Such a power ful effect could hardly be produced by the rays of the sun, because, owing to the great distance of the planet, he receives only between one-twenty-fifth and one-thirtieth of the light and heat which we do. It is therefore probable that Jupiter is not yet covered by a solid crust, as our earth is, but that his white-hot interior, whether liquid or gaseous, has nothing to cover it but the dense vapors to which that heat gives rise. In this case the vapors may be self-luminous when they have freshly arisen from the interior, and may rapidly cool off after reaching the upper limit to which they ascend.

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