About (21371) 1997 TD28
(21371) 1997 TD28 is a common asteroid. It swings within 4.838 AU of the Sun at perihelion.
Locked in a gravitational sweet spot 60° ahead of or behind a much larger body, shepherded there for billions of years.
Common asteroid 19 EP
(21371) 1997 TD28
Position computed live · sbdb
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Live ephemeris
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Score breakdown
· 4 badgesCommon 22 pts → Uncommon
- Trojan +10
- Notably bright (low H) +8
- Asteroid +1
- Catalogue designation only +0
Total score 19
3 more points to reach Uncommon.
Badges
- Asteroid · +1
- Trojan · +10
- Notably bright (low H) · +8
- Catalogue designation only
Trivia
What makes it special
- Trojan. Locked in a gravitational sweet spot 60° ahead of or behind a much larger body, shepherded there for billions of years.
What it actually is
- Its orbit family. A Jupiter trojan, parked in a gravitational sweet spot 60° ahead of or behind Jupiter and shepherded there for billions of years. There may be as many trojans as there are main-belt asteroids.
- Closest approach. At its nearest it comes within 4.84 AU of the Sun — inside the orbit of Jupiter.
- One lap. A single orbit around the Sun takes it about 11.9 years.
- How far it roams. Its orbit swings between 4.84 and 5.57 AU from the Sun.
Sense of scale
- Sense of scale. In everyday terms it is roughly 1.6× the height of Mount Everest.
- Walk around it. Walking its equator at a steady pace, eight hours a day, would take about 1.1 days.
By the numbers
- Estimated size. Nobody has measured its size directly. Assuming it reflects light like a typical asteroid, its brightness implies something roughly 14.5 km across.
Properties
- aphelion au
- 5.57
- designation
- 21371
- eccentricity
- 0.0705
- full name
- 21371 (1997 TD28)
- h mag
- 11.95
- inclination
- 7.88
- mean motion deg day
- 0.083
- moid au
- 3.86
- name
- (21371) 1997 TD28
- number only
- yes
- orbit class
- TJN
- perihelion au
- 4.838
- semi major au
- 5.205
- trojan
- yes
How to see it
Like any astronomical target, (21371) 1997 TD28 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 (21371) 1997 TD28 is a common asteroid
(21371) 1997 TD28 scores 19 points on Spacedle's rarity scale, which places it in the common tier. Another 3 points would lift it into a rarer tier.
That score comes from 4 science badges — Asteroid, Trojan, Notably bright (low H) and Catalogue designation only — 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.