Vesta
Reference data for protoplanet 4 Vesta: V = 5.1 naked-eye opposition brightness, 525 km diameter, Rheasilvia impact basin, and HED meteorites.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Peak Opposition Magnitude (V) | 5.2 mag | ± 0.9 mag | Reaches V = 5.1 at perihelic opposition (brightest of all asteroids) and ~8.5 at conjunction. | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Sidereal Orbital Period | 1325.75 d | ± 0.05 d | Equivalent to 3.630 Julian years. | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Semi-Major Axis | 2.3615 AU | ± 0.0001 AU | JPL Horizons DE440/441 planetary and satellite ephemeris solution | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Orbital Eccentricity | 0.0887 dimensionless | ± 0.0001 dimensionless | JPL Horizons DE440/441 planetary and satellite ephemeris solution | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Mean Volumetric Radius | 0.0412 R⊕ | ± 0.0001 R⊕ | Dawn orbiter mean radius of 262.7 ± 0.1 km (triaxial dimensions 572.6 × 557.2 × 446.4 km). | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Mass | 0.0000433 M⊕ | ± 1e-7 M⊕ | 2.59076 × 10²⁰ kg (~9% of the mass of the asteroid belt). | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Vesta (4 Vesta) — Brightest Asteroid Profile at RA 05h 10m 00.00s, Dec +19° 30′ 00.0″ within Taurus, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Discovered on March 29, 1807, by German physician and astronomer Heinrich Wilhelm Olbers, 4 Vesta is the second-most-massive body in the main asteroid belt after Ceres. Unlike carbonaceous C-type asteroids or icy Ceres, Vesta is a dry, fully differentiated terrestrial protoplanet with a bulk density of 3.456 grams per cubic centimeter. Detailed gravity and elemental mapping by NASA's Dawn spacecraft in 2011–2012 confirmed that Vesta melted early in Solar System history via aluminum-26 decay, segregating a 220-kilometer metallic iron-nickel core beneath an olivine-rich mantle and a basaltic crust.
Vesta departed from hydrostatic equilibrium roughly one billion years ago when a massive impactor excavated the 500-kilometer-wide Rheasilvia basin across its south pole—nearly shattering the 525-kilometer world. At the center of Rheasilvia rises a 22-kilometer-tall central peak that rivals Olympus Mons on Mars as one of the tallest mountains in the Solar System, while equatorial troughs (Divalia Fossae) girdle the globe from the shockwave. Fragments blasted from Rheasilvia populate the V-type 'Vestoid' asteroid family and arrive on Earth as the Howardite-Eucrite-Diogenite (HED) clan of achondrite meteorites.
Thanks to its bright basaltic surface (geometric albedo 0.423—four times more reflective than the Moon or Ceres) and its closer inner-belt orbit at 2.36 astronomical units, Vesta outshines all other asteroids and reaches visual magnitude 5.1 to 5.5 at opposition.
Practical Visual Observing Guide
- The only asteroid routinely visible to the unaided eye (reaching V = 5.1 to 5.6 at opposition) and effortless to follow nightly in binoculars.
- Fast 5.342-hour rotation period produces a ~0.10 to 0.20 magnitude light-curve variation driven by hemispheric albedo contrasts.
- Reaches up to 0.70 arcseconds in apparent diameter at perihelic opposition.
Catalog Cross-Identifications & Aliases
Common Aliases: 4 Vesta · A807 FA
| Catalog Authority | Identifier |
|---|---|
| SIMBAD | Vesta |
Related Objects, Comparisons & Guides
Ceres (1 Ceres) — Main-Belt Dwarf Planet Data
Reference data for dwarf planet 1 Ceres: 4.60-year orbit at 2.77 AU, 939.4 km diameter from Dawn, Occator crater salt deposits, and visual magnitude.
Mars (Terrestrial Planet & Opposition Cycle)
JPL orbital parameters (1.5237 AU, 686.98 d), 780-day synodic opposition cycle, 25.1″ maximum disk, and telescope observing guide for Mars.
Jupiter (Gas Giant & Galilean Moons)
JPL orbital parameters (5.2038 AU, 11.862 yr), opposition magnitude −2.94, 50.1″ angular disk, Galilean moons, and observing guide for Jupiter.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
Celestial Coordinates (RA & Dec) Explained
Practical reference to J2000 equatorial coordinates: Right Ascension (RA in hours, minutes, seconds), Declination (Dec in degrees), and sexagesimal conversion.
Scientific Sources & Dataset Provenance
- NASA/JPL Solar System Dynamics & Planetary Fact Sheets (DE441 (2021/2026)): Park, R. S., et al. 2021, AJ, 161, 105 (The JPL Planetary and Lunar Ephemerides DE440 and DE441) — NASA Jet Propulsion Laboratory / GSFC