The New Supernovae Alphabet Soup

This is an update of the Simostronomy blog “Supernovae Alphabet Soup” posted December 2011. Thanks to Brad Walter for the revised text.

SN 2011fe aka PTF11kly
Image: Wikipedia
The International Astronomical Union (IAU) is the sole body responsible for the official naming of astronomical objects. So if you have a problem with the way things in the Universe are named, you now know where to send your email and letters of protest.

Before we get into this, a quick grammar note: When we discuss more than one supernova, they are called supernovae (super- no- vee), not supernovas. The same holds true for more than one nova. They are novae (no- vee). Please don't talk or write about Novas. Those are old Chevrolets, not stars.

Prior to January 1, 2016, the naming convention used for supernovae was pretty simple and straightforward. Once a supernova was spectroscopically confirmed, the name was formed by combining the prefix SN, for supernova, the year of discovery and a one- or two-letter designation. The first 26 supernovae of the year get an upper case letter from A to Z (SN 1987A). After that, the IAU started over with pairs of lower-case letters, starting with aa, ab, and so on (SN 2005ap). Confirmed supernovae had sequential letter designations without gaps. Prior to being confirmed they were given a temporary designation on the IAU CBAT Transient Object Confirmation Page with “PSN” followed by a coordinate string similar to the following:
PSN J01560719+1738468.That process is no longer in use.
[]. If it is a possible SN it gets a temporary “TA” prefix which is changed to an “SN” prefix when spectroscopically confirmed.

That all changed on January 1, 2016. Naming of transient objects was transferred to the IAU Transient Name Server. This is an automated recording and naming service of the IAU for all transient objects. When an astronomer registered with the IAU submits a transient discovery it is initially given a name automatically that has an “AT” prefix followed by the year and then one or more lower case letters in sequential permutation order, for example AT 2016edj. Now when a supernova is spectroscopically confirmed, the “AT” is changed to SN but the remainder of the designation remains the same.

The addition of several wide-field survey telescopes, some of them able to detect very faint objects, coupled with extremely fast automated processing and analysis is cranking out an enormous number of transient discoveries.  Names were up to three letter suffixes by the end of January 2017 (703 discoveries). That means SN designations will usually be separated by large gaps in the letter sequences. Also many discoveries may remain unconfirmed by spectroscopic observation and may retain AT designations.

Of course there are exceptions, there are always exceptions. That's one of the things about astronomical nomenclature that is maddening, but I digress...

Four important historical supernovae are known simply by the year they occurred: SN 1006, SN 1054, SN 1572 (more commonly referred to as Tycho's Nova), and SN 1604 (also known as Kepler's Star).

One reason I'm bringing this subject up now is that the name game changed at the beginning of this year 2016 which has caused some confusion. One can no longer predict the name of the first, or any confirmed supernova in a given year. However, it is still true that the first supernova of the year will usually not occur on the first day of the year because supernova discoveries have to be officially confirmed spectroscopically before they get an official IAU designation. When someone discovers a possible supernova it gets reported to the IAU and then listed on the CBAT TNS page

As the pace of discovery increases the time lag associated with naming supernovae becomes less and less acceptable. Astronomers will want immediate notification of discoveries of all types of transient objects including supernovae. Therefore new groups searching for SNe have begun to make up their own names. The Catalina Real Time Survey [] is one such group. They are discovering dozens of possible supernovae that don't always get official IAU designations. Their discoveries are all named CSS (Catalina Sky Survey) followed by the date in yymmdd format and then the rough coordinates, like this CSS111227:104742+021815. That’s a name only a mother could love and still not remember.

ROTSE, the Robotic Optical Transient Search Experiment, also discoveries SNe and gives them their own designation in the form of ROTSE3 (the third iteration of this experiment) followed by coordinates, such as ROTSE3 J133033.0-313427.

And there is the Palomar Transient Factory which names its discoveries with the prefix PTF, of course, such as PTF11kly, the nearest supernovae in decades, visible with small telescopes in M101. This SN eventually received an IAU designation, SN 2011fe, but that just created more confusion, since now it is known variously by both names in the literature. Somehow managing to keep it all together amidst the confusion, David Bishop maintains the Latest Supernova Website [] where you can see discovery images and keep track of your favorite supernovae and related news. There is an excellent article about David
[] and how his website evolved from simple beginnings. So if want to know about the latest SNe on the WWW the URL that will lead you through the ABC's is definitely

Got that? Good, there will be a new quiz later. The answers aren’t necessarily the same as before.

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