Comet Lemmon (C/2012 F6) captivated observers in 2012-2013 with its brilliant green color and exceptional visibility in the southern hemisphere. Discovered by the Mount Lemmon Survey in Arizona, it exemplifies the chemical and physical phenomena that define these icy travelers of the solar system.
A comet is an icy celestial body composed of:
When a comet approaches the Sun (within 3-4 AU), the sublimation of ices creates:
| Characteristic | Value/Details |
|---|---|
| Official Designation | C/2012 F6 (Lemmon) |
| Discovery Date | March 23, 2012 (Mount Lemmon Survey, Arizona, USA) |
| Orbit Type | Hyperbolic (non-periodic) |
| Perihelion | 0.73 AU (March 24, 2013) |
| Peak Magnitude | ~5.5 (January 2013) |
| Distinctive Color | Green (C₂ emission at 518 nm) |
| Visibility | Southern Hemisphere (December 2012 - April 2013) |
| Minimum Distance to Earth | 0.98 AU (February 5, 2013) |
| Discoverer | A.R. Gibbs |
| Notable Composition | Diatomic carbon (C₂), cyanogen (CN), silicate dust |
N.B.:
Comets with hyperbolic orbits like Lemmon likely originate from the Oort Cloud and pass near the Sun only once before leaving the inner solar system permanently.
The emerald hue of Comet Lemmon results from fluorescence:
| Date | Event | Magnitude | Position |
|---|---|---|---|
| March 23, 2012 | Discovered by A.R. Gibbs | 20.8 | - |
| December 2012 | Visible with binoculars | < 10 | Southern Hemisphere |
| January 9, 2013 | Peak visibility | 5.5 | Sagittarius |
| March 24, 2013 | Perihelion passage | ~6 | 0.73 AU from the Sun |
| April 2013 | Gradual disappearance | > 10 | - |
N.B.:
A magnitude of 5.5 is the naked-eye visibility limit under a perfectly dark sky. In cities, a magnitude of 4 or less is typically required for unaided observation.
| Equipment Type | Features | Possible Observations |
|---|---|---|
| Naked Eye | Dark sky (limiting magnitude > 6) | Fuzzy coma (no details) |
| Binoculars | 10×50 or 20×80 | Coma and short tail visible |
| Telescope | ≥ 150 mm aperture | Coma details, dust tail |
| Photography | DSLR + long exposure (20-60 sec) | Extended tails, colors (with processing) |
N.B.:
Swan-Band or C₂ filters enhance gaseous structures in photography but reduce overall light by 30 to 50%.
Comet Lemmon (C/2012 F6) follows a hyperbolic trajectory, which means it will probably not return to the inner solar system regularly. A periodic comet (like Halley, Period ≈ 76 years) returns at predictable intervals. A hyperbolic comet has an open trajectory: it may pass near the Sun once or a few times, or escape permanently into interstellar space. In reality, the comet is moving away from the Sun and its path does not allow a "classic" orbital period to be defined.
Note :
Hyperbolic comets, unlike periodic comets, are not expected to have regular close passages. Any future observation would be exceptional and unpredictable on a human timescale.
| Year | Minimum Distance to the Sun | Estimated Distance from Earth | Remarks |
|---|---|---|---|
| 2012-2013 | 0.73 AU | 0.98 AU | Observed from the Southern Hemisphere |
| 2100 (simulation) | ~5 AU | ~4.8 AU | Distant passage, not visible to the naked eye |
| 2025 | 0.72 AU (close approach to the Sun) | ≈ 0.95 AU | Possible naked-eye observation in the Southern Hemisphere |
Note :
Hyperbolic comets, unlike periodic comets, do not have regular close passages. Any future observation would be exceptional and highly uncertain on a human timescale.
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