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Defekt massy

- raznost' mezhdu massoi svyazannoi sistemy vzaimodeistvuyushih tel i summoi ih mass v svobodnom sostoyanii. D. m. ( $\Delta {\mathfrak M}$ ) opredelyaetsya energiei svyazi sistemy ( $\Delta\varepsilon$ ): $\Delta {\mathfrak M}=\Delta\varepsilon/c^2$ . V mass-spektroskopii D. m. nazyvayut raznost' mezhdu massoi atoma, izmerennoi v atomnyh edinicah massy, i massovym chislom. Takoe opredelenie otlichaetsya ot privedennogo vyshe nachalom otscheta defekta massy i sistemoi edinic.

Dlya atomnyh yader D. m. opredelyaet predel'nuyu velichinu energii, k-raya mozhet vydelit'sya pri yadernyh reakciyah. Energiya, vydelyaemaya pri ekzotermich. ili pogloshaemaya pri endotermich. reakciyah, ravna raznosti mezhdu summoi D. m. produktov reakcii i summoi D. m. ishodnyh yader. Eto pozvolyaet issledovat' energetiku yadernyh reakcii, nenablyudaemyh v laboratornyh usloviyah, no realizuyushihsya v kosmose i opredelyayushih evolyuciyu zvezd, a takzhe processy obrazovaniya him. elementov.

Pri ochen' bol'shih gravitacionnyh potencialah, sravnimyh po velichine s c², mozhet stat' sushestvennym gravitac. D. m. Pri etom nuzhno uchityvat' ne tol'ko energiyu prityazheniya, no i polozhitel'nuyu kinetich. energiyu vzaimodeistvuyushih tel (chastic). Pri gravitacionnom kollapse gravitac. energiya svyazi perehodit v teplovuyu i kinetich. energiyu kollapsiruyushego veshestva, poetomu massa sistemy mozhet umen'shit'sya lish' za schet poter' energii na izluchenie (el.-magn., neitrinnoe, gravitacionnoe). Pri kollapse v chernuyu dyru takoe umen'shenie massy mozhet sostavlyat' 20-40%.

Gravitac. D. m. Solnca $\sim 10^{-6} {\mathfrak M}_\odot$ , belogo karlika i neitronnoi zvezdy toi zhe massy sootvetstvenno $\sim 10^{-4} {\mathfrak M}_\odot$ i $\sim 10^{-1} {\mathfrak M}_\odot$ . Gravitac. D. m. zvezdnogo skopleniya sostavlyaet 10^-7-10^-8 ot ego massy, D. m. Galaktiki i skopleniya galaktik - sootvetstvenno 10^-6 i 10^-5 ot ih mass.

Esli sr. plotnost' Vselennoi prevyshaet kriticheskuyu, to mir yavl. zamknutym (sm. Kosmologiya), tak chto gravitac. D. m. dlya Vselennoi v celom sovpadaet s ee polnoi massoi i dlya vneshnego nablyudatelya ee massa ravna nulyu. Na etom sv-ve zamknutogo mira osnovany nek-rye kosmologicheskie gipotezy spontannogo rozhdeniya Vselennoi.

(M.Yu. Hlopov)

M. Yu. Hlopov, "Fizika Kosmosa", 1986
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