Knowra 2I/Borisov 2I/Borisov 2I/Borisov is an interstellar comet discovered in 2019, the first confirmed interstellar comet and second confirmed interstellar object observed passing through the Solar System.
Hyperbolic trajectory : An unbound orbit shaped like a hyperbola, with eccentricity greater than one. Its strongly hyperbolic path showed that Borisov was not gravitationally bound to the Sun.
1I/ʻOumuamua : The first confirmed interstellar object, discovered in 2017, whose nature remains debated because it showed no clear coma. Its unusual appearance contrasts with Borisov’s unmistakable cometary activity.
Gennadiy Borisov : A Ukrainian amateur astronomer who discovered the comet now named 2I/Borisov in 2019. His observations first identified the moving object later confirmed as interstellar.
Astronomical spectroscopy : The study of celestial objects through the wavelengths and patterns of their emitted or absorbed light. Spectra revealed gases and dust in Borisov’s coma, allowing comparison with Solar System comets.
Interstellar medium : The matter and radiation occupying the space between stars in a galaxy. Borisov traveled through this environment before entering the Solar System, where erosion may have altered its surface.
Cometary coma : A cloud of gas and dust surrounding a comet’s nucleus, produced as sunlight heats its volatile material. Borisov’s coma made the object visibly cometary and supplied material for chemical measurements.
C/1995 O1 (Hale–Bopp) : A bright long-period comet discovered in 1995, notable for its large nucleus and extensive observations. Hale–Bopp offers a well-studied Solar System comet for comparing Borisov’s activity and chemistry.
Crimean Astrophysical Observatory : An astronomical observatory in Crimea where Gennadiy Borisov made his discovery observations. Borisov detected the comet with a telescope he built at this observatory.
Hubble Space Telescope : A space telescope launched in 1990 that observes ultraviolet, visible, and near-infrared light. Hubble resolved Borisov’s coma and helped constrain the size of its nucleus.
Comet fragmentation : The splitting or disintegration of a comet’s nucleus under stresses such as heating and rotation. Borisov showed signs of fragmentation, complicating estimates of its nucleus and activity.
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