1862 Apollo
First recognized Apollo asteroid, lost for decades, with a moon.
1862 Apollo is a stony near-Earth object about 1.5 kilometers across. It gives its name to the Apollo asteroids—a group of NEOs that cross Earth’s orbit. German astronomer Karl Reinmuth first spotted it on 24 April 1932 from Heidelberg Observatory, but the asteroid was then lost for decades until its recovery in 1973. Because of that long gap, its official IAU number (1862) is higher than that of later-discovered Apollos like 1566 Icarus.
Apollo’s highly eccentric orbit also takes it across the paths of Venus and Mars, making it both a Venus-crosser and a Mars-crosser. Studies of its rotation provided the first observational evidence of the YORP effect. The asteroid is named after the Greek god Apollo; the minor planets 5731 Zeus and 68 Leto are named after his parents.
A small moon was detected orbiting Apollo by radar from Arecibo Observatory between 19 October and 2 November 2005, announced on 4 November 2005 in IAU Circular 8627. The satellite is only 80 meters across and orbits just 3 kilometers from the main body. From Apollo’s surface, the moon would appear about 2.1 degrees wide.
Because its minimum orbit intersection distance with Earth is less than 0.05 AU and its diameter exceeds 150 meters, 1862 Apollo is classified as a potentially hazardous asteroid. Its Earth MOID is 0.0257 AU (about 3.84 million kilometers). The orbit is well understood for the next several hundred years; on 17 May 2075, it will pass 0.0083 AU (roughly 1.24 million kilometers) from Venus.
Quick Facts
- Minorplanet
- yes
- Background
- #FFC2E0
- Discoverer
- K. Reinmuth
- Discovered
- 24 April 1932
- Discovery Site
- Heidelberg Obs.
- Mpc Name
- (1862) Apollo
- Pronounced
- ə · ˈ · p · ɒ · l · oʊ
- Named After
- Apollo / (Greek mythology)
- Mp Category
- NEOPHA / Venus-crosser / Mars-crosser / Apollo asteroids
- Epoch
- 21 November 2025 (JD 2461000.5)
- Uncertainty
- 0
- Observation Arc
- 95.27 yr (34796 days)
Facts from the source article.
Lore & Background
1862 Apollo was discovered by German astronomer Karl Reinmuth at Heidelberg Observatory on 24 April 1932, but was lost and not recovered until 1973. Its official IAU-number (1862) is higher than that of some other Apollo asteroids such as 1566 Icarus because it was a lost asteroid for more than 40 years and other bodies were numbered in the meantime. The analysis of its rotation provided observational evidence of the YORP effect. It is named after the Greek god Apollo, after which the minor planets 5731 Zeus and 68 Leto are respectively named. On 4 November 2005, it was announced that an asteroid moon of Apollo had been detected by radar observations from Arecibo Observatory, Puerto Rico, on 19 October – 2 November 2005. The satellite is only 80 meters across and orbits Apollo just 3 kilometers away. From the surface of Apollo, the satellite would have an angular diameter of about 2.1 degrees.
Reader's Guide
1862 Apollo is notable as the namesake and first recognized member of the Apollo asteroids, a subgroup of near-Earth objects that cross Earth's orbit. Its highly eccentric orbit also crosses the orbits of Venus and Mars, making it a Venus-crosser and Mars-crosser. It is classified as a potentially hazardous asteroid because its minimum orbit intersection distance with Earth is less than 0.05 AU and its diameter is greater than 150 meters; Apollo's Earth MOID is 0.0257 AU. Its orbit is well-determined for the next several hundred years, and on 17 May 2075 it will pass 0.0083 AU from Venus. The discovery of its satellite in 2005 via radar observations from Arecibo Observatory added to its significance, as did the analysis of its rotation providing observational evidence of the YORP effect. Its status as a lost asteroid for over 40 years explains why its IAU number is higher than that of later-discovered Apollo asteroids.
Did You Know?
- 1862 Apollo was discovered on 24 April 1932 by Karl Reinmuth but was lost and not recovered until 1973.
- On 4 November 2005, a satellite of Apollo was announced, detected by radar from Arecibo Observatory.
- Apollo's Earth MOID is 0.0257 AU, and it will pass 0.0083 AU from Venus on 17 May 2075.
Frequently Asked Questions
What is 1862 Apollo?
1862 Apollo is a stony near-Earth asteroid roughly 1.5 kilometers in diameter, first observed by German astronomer Karl Reinmuth at Heidelberg Observatory on 24 April 1932. It is the first asteroid ever classified in the "Apollo" group, a category of Earth-crossing NEOs.
Why does 1862 Apollo carry a higher IAU number than asteroids found after it?
After Reinmuth's 1932 sighting the object vanished from tracking for over four decades and was not recovered until 1973. Because its orbit was only confirmed at that later date, it was assigned the much higher designation 1862, even though bodies such as 1566 Icarus received lower numbers in the interim.
What makes 1862 Apollo's orbit unusual?
Its highly eccentric path carries it across Earth's orbit as well as through the orbital zones of both Venus and Mars. This makes it simultaneously an Earth-crosser, Venus-crosser, and Mars-crosser, a combination that is relatively rare among near-Earth objects.
Does 1862 Apollo have a moon?
Yes, observations have identified a small satellite roughly 80 meters in diameter orbiting the main body. This makes 1862 Apollo one of the rarer near-Earth asteroids known to possess a natural companion.
Why is 1862 Apollo considered important in asteroid taxonomy?
As the first recognized member of its orbital class, it lends its name to the entire "Apollo" group of near-Earth asteroids. Its long period of being lost and then recovered also made it a key case study in understanding how easily small bodies can slip out of tracking.
More in Notable Asteroids, Part 2 1-24
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