Béntang itu apa sih? Jelaskan dalam bahasa sunda ya

Béntang téh hartina raga plasma di luar angkasa nu ngahasilkeun énergi tina fusi inti. Teu kawas planét, nu cahyana mangrupa pantulan, béntang mah mencarkeun cahya téh alatan panasna anu kacida. Sacara ilmiah, béntang didefinisikeun salaku bal plasma self-gravitating dina kasatimbangan hidrostatik, nu ngahasilkeun énergina sorangan tina prosés fusi inti. Béntang 'leutik' samodél Panonpoé umumna boga permukaan anu kaciri polos jeung boga starspots anu leutik. Béntang nu leuwih badag (raksasa) boga starspot anu leuwih gedé jeung leuwih jelas. Salian ti éta permukaanana nunjukkeun stellar limb-darkening anu leuwih kuat (stellar limb-darkening téh caangna béntang beuki ka gigir kaciri beuki poek). Stellar astronomy nyaéta studi bentang-bentang.

kabéh béntang (kacuali Panonpoé) kaciri ku panon manusa jiga titik cahya di langit peuting, anu kelap-kelip lantaran efek atmosfer planet bumi. Teleskop Interferometer dibutuhkeun pikeun ngahasilkeun gambar-gambar objek-objek eta. Panonpoé kaasup béntang ogé, ngan lantaran deukeut pisan jarakna jadina kaciri jiga piringan, jeung nyadiakeun cahaya panonpoé.

Béntang-béntang di alam semesta téh nyebarna teu rata, nanging biasana mah ngarumpul jadi galaksi-galaksi. Hiji galaksi biasana dibentuk ku ratusan milyar milyar béntang. Mayoritas béntang silih iket alatan gravitasi jeung béntang séjén, ngabentuk bintang kembar. Sedengkeun kumpulan béntang-béntang anu leuwih loba disebut klaster béntang.

Astronom ngira-ngira paling saeutik aya 70 sextillion (7×1022) béntang di alam semesta . Hartina aya 70 000 000 000 000 000 000 000, atawa 230 milyar kali leuwih loba batan 300 milyar di galaksi urang sorangan (galaksi Bima Sakti).

Lolobana bentang téh umurna antara samilyar nepi ka 10 milyar taun. Sababaraha bentang umurna bisa nepi ka 13.7 milyar taun, nyaéta umur alam semesta nu ka ukur. (Tingal Big Bang theory jeung stellar evolution.) They range in size from the tiny neutron stars (which are actually déad stars) no bigger than a city, to supergiants like the North Star (Polaris) and Betelgeuse, in the Orion constellation, which have a diaméter about 1,000 times larger than the Sun —about 1.6 terametres. However, these have a much lower density than the Sun.

One of the most massive stars known is η Carinae, with 100–150 times as much mass as the Sun. Recent work by Donald Figer, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, suggests that 150 solar masses is the upper limit of stars in the current éra of the universe. He used the Hubble Space Telescope to observe about a thousand stars in the Arches cluster, a massive young star cluster néar the core of the Milky Way, and found no stars over that limit despite a statistical expectation that there should be several. The réason for this limit is not precisely known, but the Eddington limit is part of the answer. The very first stars to form after the Big Bang may have been larger, up to 300 solar masses or more, due to the complete absence of elements héavier than lithium in their composition. This generation of supermassive star is long extinct, however, and currently only théoretical.

With a mass only 93 times that of Jupiter, AB Doradus C, a companion to AB Doradus A, is the smallest known star undergoing nucléar fusion in its core. Smaller bodies are brown dwarfs, which occupy a poorly-defined grey aréa between stars and gas giants. The minimum mass a star can have is estimated to be in the vicinity of 75 Jupiters.

The energy produced by stars radiates into space as electromagnetic radiation, as a stréam of neutrinos from the star's core, and as a stréam of particles from the star's outer layers (its stellar wind). The péak frequency of the light depends on the temperature of the outer layers of the star. Besides the emitted visible light, the ultraviolet and infrared components are typically significant. The apparent brightness of a star is measured by its apparent magnitude.

The néarest star to the éarth, apart from the Sun, is Proxima Centauri, which is 39.9 trillion kilométers, or 4.2 light years away (light from Proxima Centauri takes 4.2 yéars to réach éarth). Travelling at the orbit speed of the Space Shuttle (5 miles per second—almost 30,000 kilométers per hour), it would take about 150,000 yéars to get there. Distances like this are typical inside galactic discs, where the Sun and éarth are located. Stars can be much closer to éach other in the centres of galaxies and globular clusters, or much further apart in galactic halos.