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IAU Naming Conventions for Minor Planets

IAU Naming Conventions for Minor Planets

A couple of days ago, I posted about the naming conventions as defined by the IAU for comets: . Today, I’m about to post about the naming conventions for asteroids and near-earth objects (NEOs) and other minor planets.

Unlike comets, asteroids are given a provisional (temporary) designation once the first sightings of a potential minor planet are reported to the IAU Minor Planet Centre. Let’s take the asteroid 2012 DA14 as an example for explaining this whole concept.

The first part of the designation is undoubtedly the date (year) of discovery. Therefore, we infer that 2012 DA14 was discovered in the year 2012. The IAU actually uses a very confusing definition for the second half of the comet. In my opinion, the naming system for comets is 100 times better than those for minor planets and NEOs.

Anyways, let’s get into it slowly. As in the case of comets, the first letter that follows the year of discovery indicates the date of discovery, accurate to half a month. Therefore, A would mean the first two weeks of January, B stands for the last two weeks of January, C stands for the first week of February, D for the second week of February, and so on. It’s exactly similar to that of comets.

The next letter that follows this is the one that indicates the order of discovery. For example, the 4th asteroid to be discovered in the first week of February 2013 would be assigned the name 2013 CD. However, there is a serious problem with this system. 

This system of naming allows for only 25 asteroids to be named in the first or last two weeks of the month. However, our current technology has become so advanced, and there are so many innumerable minor planets, it’s a fact that more than 25 NEOs are discovered every two weeks! Startled? That’s a fact. But the world doesn’t get to know about them because most of the discoveries are apparently ‘unimportant’ to anyone other than the astrophotography and astronomy research groups. Then, what do you do (to overcome this serious problem)?

Once again, let’s get started with the example of 2012 DA14. See that the date designations are followed by a number. As I said before, the system for only 25 NEOs every two weeks is inadequate. For example, the first asteroid discovered in the first week of September 2013 would be christened 2013 IA. The 25th to be discovered in the first two weeks would be named 2013 IZ. But how can you go after Z? Therefore, the 26th would be named 2013 IA1, the 27th 2013 IA2, the 28th 2013 IA3, and so on. 

However, this system is very complicated to decipher. Here’s an easy way, with the example of 2012 DA14. We deduce that it was discovered in the second week of February, 2012. To deduce its order of discovery (number of asteroid to be discovered during that time period), multiply the number following the designation by 25. In this case, we get 350. Therefore, 2012 DA14 is the 350th NEO to be discovered in the second week of February, 2012.

Obviously, the IAU could’ve done better with this. This outdated system needs to be updated. The sooner, the better.

However, the year of discovery is often replaced by the name of a well-known NEO search survey. An example of such a name is 2040 P-L. The number is the beginning is the order of discovery (the number of the NEO to be discovered by the survey). 

Some such surveys:

P-L: Palomar-Leiden Survey (1960)

T-1: First Trojan Survey (1971)

T-2: Second Trojan Survey (1973)

T-3: Third Trojan Survey (1977)

There are hundreds of other definitions for naming asteroids with a common name. I’ll post about that later.

Image Credit: Screenshot from Wikipedia


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