C/2015 X7 (ATLAS)
| Parameter |
Value |
| Designation |
C/2015 X7 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2016-07-30T05:59:33.682560Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:20Z |
| Obs used |
620 |
| NEO |
- |
| M1 |
11.600 |
| K1 |
6.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-09-22.0000000 |
| e |
1.00189036 |
| q (au) |
3.684550 |
| a (au) |
-1949.127032 |
| i (deg) |
57.578925 |
| Ω (om, deg) |
139.884070 |
| ω (w, deg) |
348.488537 |
| M (ma, deg) |
0.000616 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.078 + 2.092\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.078 |
| n |
2.092 |
| gf |
1.000 |
| gb |
-0.998 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2015-01-28 |
2016-05-01 |
-0.2726 |
-0.309 |
| 2016-11-02 |
2017-06-16 |
-0.5340 |
+0.555 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
18:28:29.70 |
+22:06:24.1 |
HIP 90654 |
19.78 |
| 2026-02-03 12:00 |
18:28:34.76 |
+22:06:55.1 |
HIP 90654 |
18.83 |
| 2026-02-04 00:00 |
18:28:39.79 |
+22:07:26.5 |
HIP 90654 |
17.92 |
| 2026-02-04 12:00 |
18:28:44.79 |
+22:07:58.3 |
HIP 90654 |
17.08 |
| 2026-02-05 00:00 |
18:28:49.77 |
+22:08:30.4 |
HIP 90654 |
16.29 |
| 2026-02-05 12:00 |
18:28:54.71 |
+22:09:02.9 |
HIP 90654 |
15.58 |
| 2026-02-06 00:00 |
18:28:59.63 |
+22:09:35.8 |
HIP 90654 |
14.96 |
| 2026-02-06 12:00 |
18:29:04.51 |
+22:10:09.0 |
HIP 90654 |
14.42 |
| 2026-02-07 00:00 |
18:29:09.36 |
+22:10:42.6 |
HIP 90654 |
13.99 |
| 2026-02-07 12:00 |
18:29:14.18 |
+22:11:16.5 |
HIP 90654 |
13.67 |
| 2026-02-08 00:00 |
18:29:18.97 |
+22:11:50.7 |
HIP 90654 |
13.47 |
| 2026-02-08 12:00 |
18:29:23.73 |
+22:12:25.3 |
HIP 90654 |
13.39 |
| 2026-02-09 00:00 |
18:29:28.45 |
+22:13:00.3 |
HIP 90654 |
13.43 |
| 2026-02-09 12:00 |
18:29:33.15 |
+22:13:35.6 |
HIP 90654 |
13.60 |
| 2026-02-10 00:00 |
18:29:37.81 |
+22:14:11.2 |
HIP 90654 |
13.88 |
| 2026-02-10 12:00 |
18:29:42.43 |
+22:14:47.2 |
HIP 90654 |
14.27 |
| 2026-02-11 00:00 |
18:29:47.03 |
+22:15:23.5 |
HIP 90654 |
14.76 |
| 2026-02-11 12:00 |
18:29:51.59 |
+22:16:00.1 |
HIP 90654 |
15.33 |
| 2026-02-12 00:00 |
18:29:56.11 |
+22:16:37.1 |
HIP 90654 |
15.99 |
| 2026-02-12 12:00 |
18:30:00.60 |
+22:17:14.3 |
HIP 90654 |
16.71 |
| 2026-02-13 00:00 |
18:30:05.06 |
+22:17:51.9 |
HIP 90654 |
17.48 |
| 2026-02-13 12:00 |
18:30:09.48 |
+22:18:29.9 |
HIP 90654 |
18.31 |
| 2026-02-14 00:00 |
18:30:13.87 |
+22:19:08.1 |
HIP 90654 |
19.18 |
| 2026-02-14 12:00 |
18:30:18.22 |
+22:19:46.7 |
HIP 90654 |
20.09 |
| 2026-02-15 00:00 |
18:30:22.54 |
+22:20:25.5 |
HIP 90654 |
21.03 |
| 2026-02-15 12:00 |
18:30:26.81 |
+22:21:04.7 |
HIP 90846 |
21.19 |
| 2026-02-16 00:00 |
18:30:31.06 |
+22:21:44.1 |
HIP 90846 |
20.12 |
| 2026-02-16 12:00 |
18:30:35.26 |
+22:22:23.9 |
HIP 90846 |
19.06 |
| 2026-02-17 00:00 |
18:30:39.43 |
+22:23:04.0 |
HIP 90846 |
18.03 |
| 2026-02-17 12:00 |
18:30:43.56 |
+22:23:44.3 |
HIP 90846 |
17.03 |
| 2026-02-18 00:00 |
18:30:47.66 |
+22:24:25.0 |
HIP 90846 |
16.06 |
| 2026-02-18 12:00 |
18:30:51.71 |
+22:25:05.9 |
HIP 90846 |
15.12 |
| 2026-02-19 00:00 |
18:30:55.73 |
+22:25:47.1 |
HIP 90846 |
14.23 |
| 2026-02-19 12:00 |
18:30:59.71 |
+22:26:28.6 |
HIP 90846 |
13.39 |
| 2026-02-20 00:00 |
18:31:03.65 |
+22:27:10.4 |
HIP 90846 |
12.60 |
| 2026-02-20 12:00 |
18:31:07.55 |
+22:27:52.5 |
HIP 90846 |
11.89 |
| 2026-02-21 00:00 |
18:31:11.41 |
+22:28:34.8 |
HIP 90846 |
11.25 |
| 2026-02-21 12:00 |
18:31:15.24 |
+22:29:17.4 |
HIP 90846 |
10.71 |
| 2026-02-22 00:00 |
18:31:19.02 |
+22:30:00.2 |
HIP 90846 |
10.28 |
| 2026-02-22 12:00 |
18:31:22.76 |
+22:30:43.3 |
HIP 90846 |
9.96 |
| 2026-02-23 00:00 |
18:31:26.47 |
+22:31:26.7 |
HIP 90846 |
9.78 |
| 2026-02-23 12:00 |
18:31:30.13 |
+22:32:10.3 |
HIP 90846 |
9.73 |
| 2026-02-24 00:00 |
18:31:33.75 |
+22:32:54.1 |
HIP 90846 |
9.82 |