La cometa Ison, che si annuncia come "stella di Natale", probabilmente visibile a occhio nudo, si sta avvicinando sempre più al sole. Il 28 novembre giungerà al punto minimo di distanza dalla nostra stella.
Gli esperti dicono che Ison è lunga tra tre e sei chilometri. Avvicinandosi al sole la sua chioma e la coda divengono visibili. Già ora è osservabile al mattino nella costellazione della Vergine: con un buon binocolo si dovrebbe riconoscere la coda della cometa.
La maggiore cometa degli ultimi 50 anni è stata la Hale-Bopp, apparsa nella primavera del 1997.
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