C/2025 J1 (Borisov)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 J1 (Borisov) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2026-06-11T19:26:34.730880Z |
| Orbit solution date (soln_date, UTC) | 2026-09-21T07:12:14Z |
| Obs used | 922 |
| NEO | - |
| M1 | 8.600 |
| K1 | 10.250 |
| PC | 0.030 |
| Discovery observation (MPC, UTC) | 2025-05-02T23:26:46.752000Z |
| Discovery magnitude (MPC) | 19.30 G |
| Discovery observatory (MPC) | L51 · MARGO, Nauchnyi |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-11-30.0000000 |
| e | 0.99717002 |
| q (au) | 3.580293 |
| a (au) | 1265.130457 |
| i (deg) | 95.444573 |
| Ω (om, deg) | 273.976364 |
| ω (w, deg) | 166.624474 |
| M (ma, deg) | 359.995755 |
Magnitude
Scatter + Global Linear
$$ M_a = (9.631 + 5.298\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 9.631 |
| n | 5.298 |
| gf | 1.000 |
| gb | -0.777 |
| k | 0.800 |
| δ90 | 10.000 |
| Parameter | Symbol | Range | Description |
|---|---|---|---|
| Absolute magnitude at 1 AU from Sun and Earth | H0 | -5 to 20 | Intrinsic brightness of the comet |
| Photometric slope parameter | n | 2 to 6 | Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor | gf |
0.8 to 1 | Degree of forward scattering |
| Backward scattering asymmetry factor | gb |
-1 to -0.5 | Degree of backward scattering |
| Partitioning coefficient | k | 0.8 to 1 | Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio | δ90 | 1 to 10 | Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) | End (UTC) | a | b |
|---|---|---|---|
| 2025-04-29 | 2025-10-22 | +4.4523 | -3.016 |
| 2025-10-22 | 2026-05-05 | -12.7713 | +7.443 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Finding Chart
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-09-20 00:00 | 07:14:56.50 | +15:55:06.4 | HIP 35071 | 3.00 |
| 2026-09-20 12:00 | 07:15:01.45 | +15:48:40.7 | HIP 35071 | 7.31 |
| 2026-09-21 00:00 | 07:15:06.16 | +15:42:13.8 | HIP 35071 | 13.56 |
| 2026-09-21 12:00 | 07:15:10.65 | +15:35:45.9 | HIP 35071 | 20.01 |
| 2026-09-22 00:00 | 07:15:14.90 | +15:29:16.8 | HIP 35071 | 26.54 |
| 2026-09-22 12:00 | 07:15:18.91 | +15:22:46.7 | HIP 34918 | 28.27 |
| 2026-09-23 00:00 | 07:15:22.69 | +15:16:15.4 | HIP 34918 | 27.69 |
| 2026-09-23 12:00 | 07:15:26.23 | +15:09:43.0 | HIP 35143 | 22.11 |
| 2026-09-24 00:00 | 07:15:29.52 | +15:03:09.5 | HIP 35143 | 15.64 |
| 2026-09-24 12:00 | 07:15:32.58 | +14:56:34.9 | HIP 35143 | 9.36 |
| 2026-09-25 00:00 | 07:15:35.39 | +14:49:59.1 | HIP 35143 | 4.33 |
| 2026-09-25 12:00 | 07:15:37.96 | +14:43:22.1 | HIP 35143 | 6.20 |
| 2026-09-26 00:00 | 07:15:40.29 | +14:36:44.0 | HIP 35143 | 12.13 |
| 2026-09-26 12:00 | 07:15:42.36 | +14:30:04.8 | HIP 35143 | 18.59 |
| 2026-09-27 00:00 | 07:15:44.19 | +14:23:24.3 | HIP 35143 | 25.19 |
| 2026-09-27 12:00 | 07:15:45.77 | +14:16:42.8 | HIP 35053 | 20.37 |
| 2026-09-28 00:00 | 07:15:47.09 | +14:10:00.0 | HIP 35053 | 15.68 |
| 2026-09-28 12:00 | 07:15:48.16 | +14:03:16.1 | HIP 35124 | 11.51 |
| 2026-09-29 00:00 | 07:15:48.97 | +13:56:30.9 | HIP 35124 | 4.97 |
| 2026-09-29 12:00 | 07:15:49.53 | +13:49:44.6 | HIP 35124 | 2.84 |
| 2026-09-30 00:00 | 07:15:49.83 | +13:42:57.1 | HIP 35124 | 9.12 |
| 2026-09-30 12:00 | 07:15:49.87 | +13:36:08.4 | HIP 35124 | 15.85 |
| 2026-10-01 00:00 | 07:15:49.64 | +13:29:18.5 | HIP 35124 | 22.64 |
| 2026-10-01 12:00 | 07:15:49.15 | +13:22:27.4 | HIP 35124 | 29.46 |
| 2026-10-02 00:00 | 07:15:48.40 | +13:15:35.1 | HIP 35124 | 36.31 |
| 2026-10-02 12:00 | 07:15:47.37 | +13:08:41.5 | HIP 35124 | 43.19 |
| 2026-10-03 00:00 | 07:15:46.08 | +13:01:46.8 | HIP 35124 | 50.09 |
| 2026-10-03 12:00 | 07:15:44.51 | +12:54:50.8 | HIP 35005 | 51.01 |
| 2026-10-04 00:00 | 07:15:42.68 | +12:47:53.7 | HIP 35005 | 44.37 |
| 2026-10-04 12:00 | 07:15:40.56 | +12:40:55.2 | HIP 35005 | 37.80 |
| 2026-10-05 00:00 | 07:15:38.17 | +12:33:55.6 | HIP 35005 | 31.36 |
| 2026-10-05 12:00 | 07:15:35.50 | +12:26:54.8 | HIP 35005 | 25.18 |
| 2026-10-06 00:00 | 07:15:32.55 | +12:19:52.7 | HIP 35005 | 19.53 |
| 2026-10-06 12:00 | 07:15:29.32 | +12:12:49.4 | HIP 35005 | 15.04 |
| 2026-10-07 00:00 | 07:15:25.81 | +12:05:44.8 | HIP 35005 | 13.05 |
| 2026-10-07 12:00 | 07:15:22.00 | +11:58:39.1 | HIP 35005 | 14.65 |
| 2026-10-08 00:00 | 07:15:17.91 | +11:51:32.1 | HIP 34960 | 18.83 |
| 2026-10-08 12:00 | 07:15:13.53 | +11:44:23.8 | HIP 34960 | 19.34 |
| 2026-10-09 00:00 | 07:15:08.86 | +11:37:14.4 | HIP 34960 | 22.28 |
| 2026-10-09 12:00 | 07:15:03.90 | +11:30:03.7 | HIP 34960 | 26.87 |
| 2026-10-10 00:00 | 07:14:58.64 | +11:22:51.8 | HIP 35063 | 21.75 |
| 2026-10-10 12:00 | 07:14:53.09 | +11:15:38.6 | HIP 35063 | 14.67 |
| 2026-10-11 00:00 | 07:14:47.23 | +11:08:24.3 | HIP 35063 | 8.10 |