This is an update of the Simostronomy blog “Supernovae Alphabet Soup”
posted December 2011. Thanks to Brad Walter for the revised text.
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| 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.[http://wis-tns.weizmann.ac.il/search]. 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 [http://crts.caltech.edu/] 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 [http://www.rochesterastronomy.org/supernova.html] where you can see discovery images and
keep track of your favorite supernovae and related news. There is an excellent
article about David
[http://www.richobservatory.com/Site/Article.htm] 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 http://www.rochesterastronomy.org/supernova.html.
Got that? Good, there will be a new quiz later. The answers aren’t
necessarily the same as before.
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