SIMBAD: Introduction


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What is SIMBAD ?

  1. SIMBAD
  2. This SIMBAD user's guide
  3. The Centre de Données Astronomiques de Strasbourg (CDS)
  4. Contents of the data base
  5. Updating SIMBAD
  6. Most common misunderstandings about SIMBAD
  7. SIMBAD features
  8. Documentation on the World-Wide Web


1  SIMBAD

The SIMBAD database is managed by the Centre de Données astronomiques de Strasbourg (CDS).

SIMBAD is the acronym for:   S et 
 of    I dentifications, 
                           M easurements
 and   B ibliography
 for   A stronomical
                           D ata.

The SIMBAD software is developped by Anaïs Oberto, Marc Wenger, (CDS, Strasbourg).
with contributions of students during trainings

2  This SIMBAD user's guide

The present User's guide describes the SIMBAD software which is operational since December 2006.

Part I tells you how to access the SIMBAD database, and gives some general informations.

Part II is a short User's Guide containing all you need to know for querying SIMBAD.

Finally, the last part gives some additional useful tables.

Comments and suggestions are welcome concerning the software or this User's Guide (for instance by sending a message to: ).

3  The Centre de Données Astronomiques de Strasbourg (CDS)

The CDS is located at the Observatoire Astronomique de Strasbourg (France). CDS is operated under an agreement between French Institut National des Sciences de l'Univers (INSU) and Université Louis Pasteur, Strasbourg (ULP). CDS staff created and implemented the SIMBAD data base and maintain its data and software system.

in 1972, SIMBAD was created by merging the Catalog of Stellar Identifications (CSI) and the Bibliographic Star Index (see References) as they existed at the Meudon Computer Centre until 1979. The resulting data base was then expanded by the addition of source data from the many catalogs connected to the CSI and by new literature references. The database was extended to galaxies and other non-stellar objects in 1983.

In 1981, the first on-line interactive version of SIMBAD was released at the Centre de Calcul de Strasbourg-Cronenbourg (CCSC) and operated there until December 1984, when it was moved to the Paris-Sud Informatique (PSI) Univac 1190 computer at Orsay, France and operated there until June 30, 1990.

In 1990, the SIMBAD database was moved to the Strasbourg Observatory running on Unix workstations, first a DEC 5400 station, and finally a SPARC E450 station with four processors). The database management system of SIMBAD has been developed by the CDS, using the concepts of object-oriented programming. The term SIMBAD in this User's Guide will refer both to the data base itself and to the software system used.

In 2006, a new release (SIMBAD 4) has been developped in JAVA language, and using the open source PostgreSQL DBMS. It runs on three Linux PCs, devoted to 1. the web interface, servlets and web services, 2. the SIMBAD server and 3. the postgres database.

4  Contents of the data base

The SIMBAD data base presently (June 2016) contains information for:

The only astronomical objects specifically excluded from SIMBAD are Solar System bodies.

For each object, the following data are included when available (see chapter 15 for more details):

A more complete description of the contents of SIMBAD is given in chapter 15.

5  Updating SIMBAD

What is SIMBAD, and what is it not ?
The purpose of Simbad is to provide information on astronomical objects of interest which have been studied in scientific articles.

Simbad is a dynamic database, updated every working day.

It provides the bibliography, as well as available basic information such as the nature of the object, its coordinates, magnitudes, proper motions and parallax, velocity/redshift, size, spectral or morphological type, and the multitude of names (identifiers) given in the literature. The CDS team also performs cross-identifications based on the compatibility of several parameters, in the limit of a reasonably good astrometry.

Simbad is a meta-compilation built from what is published in the literature, and from our expertise on cross-identifications. By construction it is highly inhomogeneous as data come from any kind of instruments at all wavelenghts with any resolution and astrometry, and different names from one publication to another.

Simbad is not a catalogue, and should not be used as a catalogue. The CDS also provides the VizieR database which contains published lists of objects, as well as most very large surveys. The idea now is to use both Simbad and VizieR as complementary research tools.

The data contained in SIMBAD are also permanently updated, as a result of errata, remarks from the librarians (during the scanning of the literature), quality controls, or special efforts from the CDS team to better cover some specific domains (e.g., multiwavelength emitters and complex objects). Requests for corrections, errata, or suggestions are regularly received from SIMBAD users through a dedicated e-mail address ().

Corrections of errors are made under the responsibility of CDS astronomers All the remarks received from the users are very welcome, as they help us to improve the database contents through the scrutiny of specialists' eyes.

6  Most common misunderstandings about SIMBAD

Here are listed the most common and serious misunderstandings that some researchers have in mind about Simbad. It is a short summary of what the CDS team could read in articles, in questions sent to us, or heard in conferences and schools.

Simbad (should) contains everything

No. This idea could still be supported in the early 90ths. At the era of very (extremely) large surveys, providing milliards and soon trillions of sources, it does not make sense anymore. In any case, catalogues of uncharacterized sources of any survey are not systematically included in Simbad; we wait for follow-up observations. If an object is not in Simbad, then please check in VizieR. The whole content of VizieR can be searched by position.

Simbad is wrong

Yes and no. There are 3 cases :

  • the CDS team made a mistake, usually a bug in the processing of a large table;
  • the authors made a mistake, usually misprints, erroneous cross-identifications, or erroneous re-classication of known objects;
  • there are conflicting data or classifications in the literature.

    In the first and second case, we are very pleased to be contacted and to correct the mistake. We particularly appreciate that the notice contains more information and arguments than just "it is wrong". We also recommend to researchers to avoid to write it in an article. Because as soon as Simbad has been corrected, what is false is the sentence in the article, and it will stay false forever.

    In the third case, it is of prime importance that Simbad users realize that the CDS team cannot - and especially may not - act as a kind of super-referee. If there are contradictory classifications or measurements in the literature, based on objective data, it is not our role to determine who is right and who is wrong. Our duty is to provide as much information as possible in order that researchers can decide themselves.

    Spectral/morphological types from Simbad

    Though it usually means "listed in Simbad", some researchers really believe that part of the spectral types given in Simbad have been "calculated" (sic) or estimated by the CDS team. No. All spectral and morphological types come from the literature.

    What happened however is that in the past the bibcode could not be put next to the type, so that the origin has been lost. What happened too is that, due to a historical bug, many complex spectral or morphological types have been truncated. We are very conscious of these problems and working on them.

    X-matching Simbad

    A blind positionnal Xmatch on Simbad, choosing the closest source as the right one, will produce some wrong cross-identifications with a 100is not a catalogue. Xmatching Simbad is just the level zero. To go further researchers have to know what kind of objects they are expecting, take into account the accuracy of the astrometry, eventually other parameters like the magnitudes or the velocity, and be aware that the possibility to find nothing exists.

    7  SIMBAD features

    The SIMBAD database can be queried by

    8  Documentation on the World-Wide Web

    Documentation and news about SIMBAD and related CDS activities can be found on the World-Wide Web. The ``SIMBAD home page'' gives access to the following documents:

    Moreover, every query form web page has a link to a dedicated help page, and may have at its top some hot news, and at its bottom a short description of the query form usage.


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