Tag Archives: Provisional designation in astronomy

The Big Bang Theory of Trans-Neptunian objects

Season 02, Episode 04: “The Griffin Equivalency”
The Big Bang Theory astrophysicist Rajesh Koothrappali looks pleased as he talks about trans-Neptunian object 2008 NQ17

Rajesh Koothrappali (Kunal Nayyar) looks pleased as he talks about his inclusion into People magazine’s “30 Under 30 to watch” list for his discovery of the fictional trans-Neptunian object, 2008 NQ17 which exists beyond the Kuiper belt

In “The Griffin Equivalency” episode of The Big Bang Theory, Raj (Kunal Nayyar) announces that he has been chosen as one of People Magazine’s “30 visionaries under 30 years to watch” list for his discovery of the trans-Neptunian object 2008 NQ17. This fictional astronomical body exists just beyond the Kuiper Belt, a region of the Solar System that extends from the orbit of Neptune (about 30 Astronomical units(AU) away), to a distance of 50AU from the Sun. (1AU is roughly the distance of the Earth from the Sun).

Trans-Neptunian Objects in the Solar System

The distribution and classification of the trans-Neptunian Objects in our solar system

The first trans-Neptunian object discovered was Pluto in 1930 and is the second most massive known dwarf planet in the Solar System. These objects are so small and distant that it wasn’t until 1992 that the second trans-Neptunian object orbiting the Sun, (15760) 1992 QB1, was discovered. As cryptic as these names sound, i.e 2008 NQ17 and 1992 QB1, the nomenclature comes from a provisional designation in astronomy that names objects immediately following their discovery. Once a proper orbit has been calculated, a permanent designation consisting of a number-name combination is given by the Minor Planet Center. Unfortunately for Raj, so many of these minor planets are discovered that most won’t be named for their discoverers.

Provisional designation of Minor Planets

The provisional naming system for minor planets, of which dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, and other trans-Neptunian objects are a part of, have been in place since 1925. The first element in a minor planet’s provisional designation is the year of discovery, followed by two letters and sometimes a number.

The first letter indicates the “half-month” of the object’s discovery. “A” denotes a discovery in the first half of January (between January 1st and January 15th) while “B” denotes a discovery in the second half of January (between January 16th and January 31st). The letter “I” is not used so the letters go all the way up to “Y”. The first half is always the 1st through to the 15th of the month, regardless of the numbers of days in the second “half”.

First Letter (A-G)
A B C D E F G
Jan 1 Jan 16 Feb 1 Feb 16 Mar 1 Mar 16 Apr 1

First Letter (H-O)
H J K L M N O
Apr 16 May 1 May 16 Jun 1 Jun 16 Jul 1 Jul 16

First Letter (P-V)
P Q R S T U V
Aug 1 Aug 16 Sep 1 Sep 16 Oct 1 Oct 16 Nov 1

First Letter (W-Y)
W X Y
Nov 16 Dec 1 Dec 16

The second letter and the number indicate the order or discovery within that half-month.

Second Letter (A-K)
A B C D E F G H J K
1 2 3 4 5 6 7 8 9 10

Second Letter (L-U)
L M N O P Q R S T U
11 12 13 14 15 16 17 18 19 20

Second Letter (V-Z)
V W X Y Z
21 22 23 24 25

So the 14th minor planet discovered in the first half of June 2013 will get the provisional planetary designation 2013 LO. As modern techniques has made it (relatively) easier to detect these objects, there can be more than 25 discoveries in a given half-month. To solve this a subscript number is added to indicate the number of times that the letters have cycled through. So the 40th minor planet to be discovered in the first half of June 2013 will gain the designation 2013 LP1.
\[\begin{aligned}
40 & = 25 + 15 \\
\therefore P & = 15
\end{aligned}\]

Planet Bollywood

Using this information we can calculate when Raj discovered “Planet Bollywood”. It was discovered some time between July 1-15 and it was the 441st minor planet to be discovered in that half month.
\[\begin{aligned}
Q & = 16 \\
25 \times 17 & = 425
\end{aligned}\]
And \(425 + 16 = 441\).

It must have been a particularly busy month in the Big Bang Theory Universe. A quick check at the Minor Planet Center’s Provisional Designations webpage indicates that there were 137 astronomical bodies discovered in that half-month. That would make that last trans-Neptunian object to be discovered to receive the provisional designation 2008 NM4.

Long live Planet Bollywood!