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A transient astronomical event, often shortened by astronomers to a transient, is an astronomical object or phenomenon whose duration may be from seconds to days, weeks or even several years. This is in contrast to the time scale of millions or billions of years during which the galaxies and their component stars in our universe have evolved. Singularly, the term is used for violent deep sky events such as supernovae , gamma ray bursts, transit, gravitational microlensing, Tidal disruption event etc. Before the invention of telescopes, events like these which were visible to the naked eye, from within or near the Milky Way Galaxy, were very rare - sometimes hundreds of years part. But such events were recorded in antiquity, such as the supernova in 1054 observed by Chinese, Japanese, and Arab astronomers, and the one in 1572, known as "Tychos's supernova" after Tycho Brahe who studied it until it faded after two years.〔(Lecture by Prof. Carolin Crawford, 2014, “The Transient Universe” )〕 Even though telescopes made it possible to see more distant events, their small fields of view, typically less than 1 square degree, meant the chances of looking at the right place at the right time were low. As the interest in transients has intensified,〔 because their study helps astrophysicists to understand the mechanisms which produced our universe, telescopes with larger fields of view are coming into use. These, such as the Palomar Transient Factory, the Gaia (spacecraft) and the LSST are able to spot many more such occurrences. The fact that modern instruments can observe in wavelengths invisible to the eye (radio waves, infrared, ultraviolet, x-ray) increases the information to be obtained when a transient is studied. The proposed ULTRASAT satellite will observe a field of more than 200 square degrees continuously in the ultraviolet. This wavelength is particularly important for detecting supernovae within minutes of their occurrence. ==See also== * Gamma-ray burst * List of gamma-ray bursts * Soft X-ray transient * Visibly dark X-ray source * X-ray burster * X-ray pulsar * X-ray transient * Tidal disruption event * Supernova * Transit * gravitational microlensing 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「transient astronomical event」の詳細全文を読む スポンサード リンク
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