| Parameter |
Value |
| Designation |
C/2025 B2 (Borisov) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2026-09-11T17:02:15.377280Z |
| Orbit solution date (soln_date, UTC) |
2026-07-28T14:12:17Z |
| Obs used |
391 |
| NEO |
- |
| M1 |
6.500 |
| K1 |
8.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2025-01-20T18:38:49.344000Z |
| Discovery magnitude (MPC) |
20.30 G |
| Discovery observatory (MPC) |
L51 · MARGO, Nauchnyi |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2025-10-22.0000000 |
| e |
1.00162099 |
| q (au) |
8.239086 |
| a (au) |
-5082.735080 |
| i (deg) |
91.744125 |
| Ω (om, deg) |
84.865702 |
| ω (w, deg) |
78.854374 |
| M (ma, deg) |
-0.000883 |
Magnitude
Scatter + Global Linear
$$
M_a = (-0.525 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
-0.525 |
| n |
6.000 |
| gf |
0.999 |
| gb |
-0.503 |
| k |
1.000 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
17:00:50.33 |
+85:26:25.4 |
HIP 80561 |
41.09 |
| 2026-07-29 12:00 |
16:59:15.54 |
+85:22:10.0 |
HIP 82630 |
37.06 |
| 2026-07-30 00:00 |
16:57:44.66 |
+85:17:52.7 |
HIP 82630 |
32.50 |
| 2026-07-30 12:00 |
16:56:17.53 |
+85:13:33.6 |
HIP 82630 |
27.95 |
| 2026-07-31 00:00 |
16:54:54.02 |
+85:09:12.7 |
HIP 82630 |
23.43 |
| 2026-07-31 12:00 |
16:53:34.00 |
+85:04:50.1 |
HIP 82630 |
18.98 |
| 2026-08-01 00:00 |
16:52:17.34 |
+85:00:25.8 |
HIP 82630 |
14.66 |
| 2026-08-01 12:00 |
16:51:03.92 |
+84:56:00.0 |
HIP 82630 |
10.65 |
| 2026-08-02 00:00 |
16:49:53.63 |
+84:51:32.7 |
HIP 82630 |
7.49 |
| 2026-08-02 12:00 |
16:48:46.35 |
+84:47:03.8 |
HIP 82630 |
6.55 |
| 2026-08-03 00:00 |
16:47:41.98 |
+84:42:33.5 |
HIP 82630 |
8.61 |
| 2026-08-03 12:00 |
16:46:40.41 |
+84:38:01.9 |
HIP 82630 |
12.26 |
| 2026-08-04 00:00 |
16:45:41.55 |
+84:33:28.9 |
HIP 81625 |
9.80 |
| 2026-08-04 12:00 |
16:44:45.29 |
+84:28:54.6 |
HIP 81625 |
6.59 |
| 2026-08-05 00:00 |
16:43:51.56 |
+84:24:19.0 |
HIP 81625 |
6.03 |
| 2026-08-05 12:00 |
16:43:00.26 |
+84:19:42.2 |
HIP 81625 |
8.68 |
| 2026-08-06 00:00 |
16:42:11.31 |
+84:15:04.3 |
HIP 81625 |
12.68 |
| 2026-08-06 12:00 |
16:41:24.63 |
+84:10:25.2 |
HIP 81625 |
17.10 |
| 2026-08-07 00:00 |
16:40:40.15 |
+84:05:45.0 |
HIP 81625 |
21.70 |
| 2026-08-07 12:00 |
16:39:57.78 |
+84:01:03.7 |
HIP 81625 |
26.38 |
| 2026-08-08 00:00 |
16:39:17.47 |
+83:56:21.4 |
HIP 81625 |
31.12 |
| 2026-08-08 12:00 |
16:38:39.14 |
+83:51:38.0 |
HIP 80005 |
32.05 |
| 2026-08-09 00:00 |
16:38:02.72 |
+83:46:53.7 |
HIP 80005 |
30.15 |
| 2026-08-09 12:00 |
16:37:28.17 |
+83:42:08.4 |
HIP 80005 |
28.96 |
| 2026-08-10 00:00 |
16:36:55.40 |
+83:37:22.2 |
HIP 80005 |
28.59 |
| 2026-08-10 12:00 |
16:36:24.38 |
+83:32:35.2 |
HIP 82027 |
26.49 |
| 2026-08-11 00:00 |
16:35:55.04 |
+83:27:47.2 |
HIP 82027 |
23.43 |
| 2026-08-11 12:00 |
16:35:27.33 |
+83:22:58.4 |
HIP 80319 |
21.00 |
| 2026-08-12 00:00 |
16:35:01.19 |
+83:18:08.8 |
HIP 80319 |
19.52 |
| 2026-08-12 12:00 |
16:34:36.59 |
+83:13:18.5 |
HIP 82027 |
19.20 |
| 2026-08-13 00:00 |
16:34:13.47 |
+83:08:27.3 |
HIP 82027 |
20.05 |
| 2026-08-13 12:00 |
16:33:51.78 |
+83:03:35.4 |
HIP 82027 |
21.96 |
| 2026-08-14 00:00 |
16:33:31.48 |
+82:58:42.8 |
HIP 82027 |
24.70 |
| 2026-08-14 12:00 |
16:33:12.54 |
+82:53:49.6 |
HIP 82027 |
28.02 |
| 2026-08-15 00:00 |
16:32:54.90 |
+82:48:55.6 |
HIP 81667 |
31.20 |
| 2026-08-15 12:00 |
16:32:38.53 |
+82:44:01.0 |
HIP 81667 |
27.41 |
| 2026-08-16 00:00 |
16:32:23.39 |
+82:39:05.8 |
HIP 81667 |
24.02 |
| 2026-08-16 12:00 |
16:32:09.44 |
+82:34:10.0 |
HIP 81667 |
21.22 |
| 2026-08-17 00:00 |
16:31:56.65 |
+82:29:13.6 |
HIP 81667 |
19.27 |
| 2026-08-17 12:00 |
16:31:44.99 |
+82:24:16.6 |
HIP 81667 |
18.46 |
| 2026-08-18 00:00 |
16:31:34.41 |
+82:19:19.1 |
HIP 81664 |
18.90 |
| 2026-08-18 12:00 |
16:31:24.90 |
+82:14:21.1 |
HIP 81664 |
20.53 |
| 2026-08-19 00:00 |
16:31:16.41 |
+82:09:22.5 |
HIP 81664 |
23.11 |