2623 Zech
Stony binary asteroid discovered in 1919 with a moon.
2623 Zech (provisional designation A919 SA) is a stony asteroid in the inner main belt, roughly 6.5 kilometers across. It was discovered on 22 September 1919 by German astronomer Karl Reinmuth at Heidelberg Observatory in southwest Germany. The asteroid is named after Gert Zech, a German astronomer at the Astronomisches Rechen-Institut (ARI) in Heidelberg.
Zech orbits the Sun at a distance of 1.7 to 2.8 AU, completing one orbit every 3 years and 5 months (1,236 days). Its orbit has an eccentricity of 0.24 and an inclination of 4° relative to the ecliptic. The observation arc begins with its discovery, as no precovery images or prior identifications exist. On 8 June 2002, Zech passed within 0.036 AU (about 5.4 million kilometers) of the large asteroid 3 Juno.
Estimates of Zech’s diameter vary. Johnston's Archive gives a value of 7.61 kilometers, while the Collaborative Asteroid Lightcurve Link, assuming a standard albedo of 0.20 for stony asteroids, calculates 6.5 kilometers from an absolute magnitude of 13.3. No measurements from the IRAS, Akari, or WISE/NEOWISE surveys have been published.
In October 2004, photometric observations by American astronomer Donald P. Pray at Sugarloaf Mountain Observatory, Massachusetts, in collaboration with colleagues from France, the Czech Republic, Serbia, Georgia, and Ukraine, produced a lightcurve for Zech. The data revealed a rotation period of 2.7401 hours with a brightness variation of 0.22 magnitude (quality rating not available). Although not a fast rotator, Zech spins relatively quickly for its size—most minor planets have rotation periods between 2.2 and 20 hours.
The same observations showed that Zech is an asynchronous binary asteroid, with a moon orbiting it. The moon has an orbital period of 117.2 hours and a spin period of 18.718 hours, with an amplitude of 0.08 magnitude. Based on a secondary-to-primary mean diameter ratio of more than 0.29, Johnston's Archive estimates the moon’s diameter to be at least 2.21 kilometers.
The minor planet was named after Gert Zech (born 1941), who served as editor of *Astronomy and Astrophysics Abstracts* and is known for using dynamical methods to determine the astronomical unit and the mass of the Earth–Moon system from observations of the near-Earth object 433 Eros. The naming citation was prepared by Lutz D.
Quick Facts
- Minorplanet
- yes
- Background
- #D6D6D6
- Discovered
- 22 September 1919
- Discoverer
- K. Reinmuth
- Discovery Site
- Heidelberg Obs.
- Mpc Name
- (2623) Zech
- Named After
- Gert Zech / (ARI astronomer)
- Mp Category
- main-belt(inner)
- Epoch
- 4 September 2017 (JD 2458000.5)
- Uncertainty
- 0
- Observation Arc
- 97.70 yr (35,684 days)
- Aphelion
- 2.7846 AU
Facts from the source article.
Lore & Background
2623 Zech orbits the Sun in the inner main-belt at a distance of 1.7–2.8 AU once every 3 years and 5 months (1,236 days). Its orbit has an eccentricity of 0.24 and an inclination of 4° with respect to the ecliptic. The body's observation arc begins with its official discovery observation, as no precoveries were taken, and no prior identifications were made. On 8 June 2002, Zech passed 0.036 AU (5,400,000 km) from the major asteroid 3 Juno.
In October 2004, a rotational lightcurve of Zech was obtained from photometric observations by American astronomer Donald P. Pray at Sugarloaf Mountain Observatory, Massachusetts, in a collaboration with other American and European astronomers. Lightcurve analysis gave a rotation period of 2.7401 hours with a brightness variation of 0.22 magnitude. While not being a fast rotator, it has a relatively fast spin rate for its size.
During Pray's photometric observations, it was revealed that Zech is an asynchronous binary asteroid with a minor planet moon orbiting it. The moon has an orbital period of 117.2 hours and a spin rate of 18.718 hours with an amplitude of 0.08 magnitude. Based on Pray's secondary-to-primary mean diameter ratio of more than 0.29, Johnston's Archive estimates a diameter of at least 2.21 kilometers for Zech's companion.
Reader's Guide
2623 Zech is significant as a binary asteroid system discovered through collaborative photometric observations in 2004, adding to the known population of minor planets with satellites. Its discovery by Donald P. Pray and international collaborators highlights the role of amateur-professional partnerships in asteroid research. The asteroid's name honors German astronomer Gert Zech, known for his work on the dynamical determination of the astronomical unit and the mass of the Earth–Moon system using observations of the near-Earth object 433 Eros. The naming citation was prepared by Lutz D. Schmadel and published on 18 February 1992. The asteroid's relatively fast spin rate for its size and the presence of a moon with a longer orbital period contribute to understanding the formation and evolution of binary systems in the inner main-belt. The uncertainty in diameter estimates—6.5 kilometers from lightcurve assumptions versus 7.61 kilometers from Johnston's Archive—reflects the lack of published space-based survey data from IRAS, Akari, and WISE/NEOWISE.
Did You Know?
- It is an asynchronous binary asteroid with a moon that has an orbital period of 117.2 hours.
- The asteroid's moon has an estimated diameter of at least 2.21 kilometers based on a secondary-to-primary diameter ratio of more than 0.29.
- On 8 June 2002, Zech passed within 0.036 AU (5,400,000 km) of the major asteroid 3 Juno.
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