← Back to dex - Passes within two lunar distances of Earth's orbit +18
- Far-flung orbit (a > 50 AU) +14
- Has a proper name +8
- Comet +6
- Steeply tilted orbit (i > 40°) +4
Total score 50
28 more points to reach Anomaly.
Badges
- ☄️ Comet · +6
- 🏷️ Has a proper name · +8
- 🪡 Passes within two lunar distances of Earth's orbit · +18
- 🛤️ Far-flung orbit (a > 50 AU) · +14
- 📏 Steeply tilted orbit (i > 40°) · +4
✨ Trivia
What it actually is
- 🛸 Its orbit family. A long-period comet falling in from the Oort Cloud, where it spent billions of years in the deep freeze before something nudged it loose.
- 🌞 Closest approach. At its nearest it comes within 0.86 AU of the Sun — inside the orbit of Earth.
- 🔁 One lap. A single orbit around the Sun takes it about 700 years.
- 🥏 How far it roams. Its orbit swings between 0.86 and 156.78 AU from the Sun.
Standing on it
- 💨 Growing a tail. Once inside roughly the orbit of Mars the ice starts turning straight to gas, blowing out the coma and tail that make a comet a comet.
- ☄️ Tail. Its tail always points away from the Sun, never trailing behind its motion — it is blown, not dragged.
By the numbers
- 🧊 Made of. A comet is a dirty snowball: water ice, frozen carbon dioxide and dust, held together loosely enough that some simply crumble when the Sun warms them.
What's in a name
- 🏷️ Named. Notable enough to have earned a proper name, not just a catalogue number.
Properties
- aphelion au
- 156.77
- designation
- 2015 D4
- eccentricity
- 0.9891
- full name
- C/2015 D4 (Borisov)
- inclination
- 77.3
- mean motion deg day
- 0.0014
- moid au
- 0.0034
- name
- C/2015 D4 (Borisov)
- named
- yes
- orbit class
- COM
- perihelion au
- 0.862
- semi major au
- 78.82
About C/2015 D4 (Borisov)
C/2015 D4 (Borisov) is an epic comet. It swings within 0.862 AU of the Sun at perihelion.
A long-period comet falling in from the Oort Cloud, where it spent billions of years in the deep freeze before something nudged it loose.
How to see it
Like any astronomical target, C/2015 D4 (Borisov) is best seen from a dark site away from city lights, and when it is above the horizon depends on your latitude and the time of year. Because it moves against the background stars, the live position panel on this page tracks where it is right now. The visibility panel above works out tonight's viewing window for your saved location.
Why C/2015 D4 (Borisov) is an epic comet
C/2015 D4 (Borisov) scores 50 points on Spacedle's rarity scale, which places it in the epic tier. Another 28 points would lift it into a rarer tier.
That score comes from 5 science badges — Comet, Has a proper name, Passes within two lunar distances of Earth's orbit, Far-flung orbit (a > 50 AU) and Steeply tilted orbit (i > 40°) — each earned for a real, measurable property of the object. Rarity on Spacedle is never random: the more remarkable an object's astrophysics, the more badges it collects, the higher it scores, and the rarer it ranks.