# 816 Juliana
**816 Juliana** (provisional designation A916 CE) is a large main-belt asteroid about 50.7 km in diameter, discovered on 8 February 1916 by the German astronomer [Max Wolf](https://www.edgepedia.org/max-wolf) at [Heidelberg](https://www.edgepedia.org/heidelberg) and named, presumably, for [Juliana of the Netherlands](https://www.edgepedia.org/juliana-of-the-netherlands), then a princess and later queen[1](https://ndl.ethernet.edu.et/bitstream/123456789/32939/1/Lutz%20D.%20Schmadel.pdf) • [2](https://www.spacereference.org/asteroid/816-juliana-a916-ce).
| Key fact | Detail |
|---|---|
| Discovery | 8 February 1916 by M. F. Wolf at Heidelberg[1](https://ndl.ethernet.edu.et/bitstream/123456789/32939/1/Lutz%20D.%20Schmadel.pdf) |
| Name origin | Presumably Queen Juliana of the Netherlands; Wolf had earlier named 392 Wilhelmina after her mother[1](https://ndl.ethernet.edu.et/bitstream/123456789/32939/1/Lutz%20D.%20Schmadel.pdf) |
| Orbit | Semi-major axis 3.008 AU, eccentricity 0.106, inclination 14.31°; period 1,910 days (5.23 years)[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce) |
| Distance from the Sun | Perihelion 2.69 AU, aphelion 3.33 AU[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce) |
| Size and surface | Diameter about 50.7 km; geometric albedo 0.043, a dark surface[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce) |
| Rotation | One rotation every 10.56 hours[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce) |
| Hazard status | Not a near-Earth object and not classified as potentially hazardous[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce) |
## Discovery and naming
Max Wolf found 816 Juliana on 8 February 1916 at Heidelberg, one of hundreds of minor planets he discovered there[1](https://ndl.ethernet.edu.et/bitstream/123456789/32939/1/Lutz%20D.%20Schmadel.pdf). The *Dictionary of Minor Planet Names* records the name as given presumably in honor of Queen Juliana (1909–) of the Netherlands. The astronomer Tom Gehrels, in connection with his interpretation of the name of [392 Wilhelmina](https://www.edgepedia.org/392-wilhelmina), pointed out that it seems very consistent that Wolf named an asteroid after Queen Wilhelmina's daughter as well[1](https://ndl.ethernet.edu.et/bitstream/123456789/32939/1/Lutz%20D.%20Schmadel.pdf).
## Orbit
Juliana orbits in the main portion of the asteroid belt between Mars and Jupiter. Its orbit has a semi-major axis of 3.008 AU, an eccentricity of 0.106, and an inclination of 14.31°, and it completes one revolution every 1,910 days, or 5.23 years, moving at an average orbital speed of 17.13 km/s[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce). The orbit carries it from 2.69 AU at perihelion to 3.33 AU at aphelion[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce).
The orbit is well determined. The [Minor Planet Center](https://www.edgepedia.org/minor-planet-center) records 4,748 observations used to determine it, with observations dating back to the 1916 discovery and a last official observation on 4 July 2023[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce). An occultation prediction for 30 May 2017, computed from 1,560 accepted observations spanning 1960 to 2017, gave a 1-sigma positional uncertainty of only about 0.027 arcseconds[3](https://occultations.org.nz/planet/2017/updates/170530_816_50912_u.htm).
## Physical characteristics
Juliana is about 50.7 km across, a size the Space Reference summary describes as larger than 99% of asteroids and comparable to the U.S. state of [Rhode Island](https://www.edgepedia.org/rhode-island)[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce). The 2017 occultation prediction used an approximate diameter of 50 km[3](https://occultations.org.nz/planet/2017/updates/170530_816_50912_u.htm). Its geometric albedo of 0.043 means it reflects only a few percent of incident sunlight, a dark surface typical of primitive outer-belt material[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce). Light-curve observations give a rotation period of 10.56 hours[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce), and the occultation solution lists an absolute magnitude H of 10.35[3](https://occultations.org.nz/planet/2017/updates/170530_816_50912_u.htm).
## The Juliana family
A 2025 Gaia-based survey of primitive, dark, spectrally red asteroid families in the main belt lists the [Juliana family](https://www.edgepedia.org/juliana-family) among the X-complex families, a group of 29 families including [22 Kalliope](https://www.edgepedia.org/22-kalliope), 87 Sylvia, and [375 Ursula](https://www.edgepedia.org/375-ursula)[4](https://academic.oup.com/mnras/article/545/3/staf2067/8339709). The X-complex is a spectral category whose members share similar, generally medium-albedo reflectance properties; the study notes that most X-complex families are dark, and that future near-infrared observations should help link such families to meteorite types[4](https://academic.oup.com/mnras/article/545/3/staf2067/8339709).
## Hazard status
Juliana is not a near-Earth object: its orbit stays 1.70 AU from [Earth's orbit](https://www.edgepedia.org/earths-orbit) at the closest point, and orbital simulations by NASA JPL's CNEOS show no close approaches to Earth, so JPL has not classified it as potentially hazardous[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce). It is also not considered a viable target for human exploration by the NHATS study[2](https://www.spacereference.org/asteroid/816-juliana-a916-ce).
## References
1. [Lutz D. Schmadel, Dictionary of Minor Planet Names, 5th ed., entry for (816) Juliana](https://ndl.ethernet.edu.et/bitstream/123456789/32939/1/Lutz%20D.%20Schmadel.pdf)
2. [Asteroid Juliana (816), Space Reference](https://www.spacereference.org/asteroid/816-juliana-a916-ce)
3. [RASNZ Occultation Section, Juliana occultation update, 2017 May 30](https://occultations.org.nz/planet/2017/updates/170530_816_50912_u.htm)
4. [Searching for primitive, dark, spectrally red asteroid families in the main belt with Gaia, Monthly Notices of the Royal Astronomical Society](https://academic.oup.com/mnras/article/545/3/staf2067/8339709)
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*Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Main-belt asteroids and numbered minor planets › Middle-belt asteroids › Asteroids named for people*
*Initially written Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license