A short-period comet that goes round the Sun every 6.9 years, at perihelion about December 2028
Returns in December 2028. First in reach from Georgetown about 5 September 2028 to 4 January 2029, with a small telescope.
Returns in December 2028. First in reach from Georgetown about 5 September 2028 to 4 January 2029, with a small telescope.
From Lethem, under a dark interior sky: Returns in December 2028. First in reach from Lethem about 7 August 2028 to 4 January 2029, with binoculars.
It is not placed for viewing tonight. On its next best night from Georgetown, 11 December 2028, face south (azimuth 181 degrees) at 8:57 pm GYT and look almost overhead, 85 degrees up. It will be 134 degrees from the Sun.
A window is a run of nights on which it is at least 10 degrees up with the Sun at least 12 degrees down and its forecast brightness reaches a camera or better from Georgetown. The forecast is from how the comet behaved on past returns.
From 8 November 2026 to 30 January 2027 it is hidden in the Sun's glare from Georgetown: 84 nights.
From 5 December 2027 to 4 March 2028 it is hidden in the Sun's glare from Georgetown: 91 nights.
| In reach | Best night | Best time | Height and direction | Gear on the best night | Forecast magnitude | Nights at each rung |
|---|---|---|---|---|---|---|
| 5 September 2028 to 4 January 2029 | 11 December 2028 | 8:57 pm GYT | 85 degrees, south | Small telescope | about 6.8 (likely 6.2 to 7.4) | 66 small telescope, 56 camera |
Nobody has reported its brightness to COBS in the last 30 days, so every number here is a forecast.
The forecast comes from past returns (2008, 2015, 2022): a law fitted to 130 eye estimates before perihelion and 222 after, with the Earth's distance at the time removed and this return's put in. Comets do change between returns.
On its best night from Georgetown, 11 December 2028, it could be about 6.8 (likely 6.2 to 7.4), reading 6.8 through the air. Chance of the naked eye: no real chance. Binoculars: about 51%. A small telescope: about 99%. The range is one standard deviation either side: about two forecasts in three land inside it.
A comet's light is spread over a fuzzy patch, so it is harder to see than a star of the same magnitude. That is why the gear rungs ask for a magnitude in hand.
Plan for 11 December 2028: aim at azimuth 181 degrees, altitude 85 degrees, at 8:57 pm GYT.
On a fixed tripod keep each exposure short enough that the stars stay round, then stack many frames. For a long stack, align on the comet as well as on the stars: it drifts against them from frame to frame. A dark site adds more than any lens.
19P/Borrelly passes closest to the Sun (perihelion) about 11 December 2028, at 1.310 au, where 1 au is the Earth's distance from the Sun. One orbit takes 6.86 years. The orbit is tilted 29.3 degrees to the Earth's and its eccentricity is 0.6371 (0 is a circle, 1 an open curve).
Orbit: NASA/JPL Horizons osculating elements, solution JPL#K283/1, retrieved 8 October 2026. Positions on this page are computed from them in your browser and agree with JPL's own tables to half an arcminute.
19P/Borrelly is a short-period comet that goes round the Sun every 6.9 years. The "P" in 19P marks a periodic comet, and the number is the order in which its return was first confirmed.
Brightest eye estimate reported to COBS on each past return: 2008: magnitude 9.1, 18 days after perihelion, 1.37 au from the Sun and 2.12 au from Earth; 2015: magnitude 10.2, 139 days after perihelion, 2.03 au from the Sun and 2.70 au from Earth; 2022: magnitude 8.5, 8 days before perihelion, 1.31 au from the Sun and 1.24 au from Earth. How bright a return looks depends as much on how near the Earth it passes as on the comet.
Orbits: NASA/JPL Horizons (Giorgini, JD and the JPL Solar System Dynamics Group), data retrieved 2026-10-08.
Catalogue brightness laws: JPL Small-Body Database and the IAU Minor Planet Center.
Observed brightness: COBS Comet Observation Database (https://cobs.si) and its contributing observers, CC BY-NC-SA 4.0.
Data updated 8 October 2026. "Forecast" means: Not measured yet this return. Based on how this comet behaved on past returns.
Gear rungs and ranges are estimates for a typical observer: your eyes, your sky and the night will differ.