Science to what’s in a name

YOU may recall the excitement in January this year when the US space probe New Horizons flew past the most distant object ever seen at close range.

This was originally called 2014 MU69, then given the temporary name Ultima Thule. Now, the International Astronomical Union has approved a permanent name: Arrokoth.

In 2015, New Horizons made the first-ever flyby of the dwarf planet Pluto, and returned a wealth of information about it.

This included close-up photographs that revealed to us for the first time since its discovery in 1930 what Pluto really looked like. It turned out to be unexpectedly active, with a geologically young surface that had fewer than the expected number of craters.

Following its highly successful Pluto encounter, New Horizons continued its journey. It was decided that its next target — assuming it still worked — would be an object orbiting beyond Pluto that was discovered in 2014. It is one of a multitude of small bodies forming the Kuiper Belt, named after astronomer Gerard Kuiper.

The initial designation 2014 MU69 indicates its year of discovery, followed by letters and numbers indicating which halfmonth the discovery was made, and the order of discovery during that brief period.

In advance of the spacecraft encounter, 2014 MU69 was given the name Ultima Thule as a result of a competition. The name means “beyond the limits of the known world”, but it was clear at the time that this would be only a temporary name until the IAU assigned one that would be official.

The permanent name Arrokoth was announced by the IAU on 13 November, and it was chosen as a result of the desire to have a name with an important connection to the US state of Maryland. There are many connections between this celestial object and Maryland. Importantly, the New Horizons mission has close connections with the Johns Hopkins Applied Physics Laboratory, which is based in Maryland’s Howard County, and with NASA’s Goddard Space Flight Centre, also located in that state in a place called Greenbelt.

Other connections are that Arrokoth was discovered using the Hubble Space Telescope, which is managed by Goddard; and the Space Telescope Science Institute — where the sciences operations are based — is in Baltimore, also in Maryland.

So, what is the actual connection with this little-known name? Well, in the language of the Powhatan people from this district the name means “sky”. Unfortunately, their language, one of the group called the Algonquian languages, is a lost language, but research turned up the word in a book dating from about four centuries ago.

In the Launceston Planetarium we are often asked about the naming of astronomical objects. This is handled by the International Astronomical Union, which is the world body of professional astronomers. Within that body there are working groups that are responsible for the approval of names of various types of celestial objects.

There are agreed constraints on the names that can be used. For example, objects like Arrokoth, which are in a stable orbit farther out than Neptune, are given names associated with creation. On the surface of Venus, meanwhile, features are named after women — including mythological goddesses.

Our most common query is about the naming of stars, especially as there are organisations that offer to “sell” star names. These names are never used by astronomers, and the IAU is careful to point that out.

It may seem a lovely gesture to pay to “name” a star for someone, but that name is recognised only by the commercial organisation. Some places also offer star sponsorship for fundraising purposes. This is quite different, as there is no suggestion that astronomers will actually use those names.