Frequently Asked Questions about the SIMBAD service.

Updated: March 15, 2024 - 12:18 CET

SIMBAD contents

Why is my paper missing from an object's bibliographic references?

New links between papers and astronomical objects are added to SIMBAD on every working day by the CDS documentalists. Your paper might not yet appear in an object's bibliography for several reasons:

  • The paper has not been fully processed yet. Papers are only processed by the SIMBAD team after they get published by the journals. The processing of a paper at CDS for its ingestion in SIMBAD involves several teams where documentalists, astronomers and engineers work together. The process is not a fully automated one, and depending on the complexity, quality and quantity of data, it can take several months.

    See also "How do I check the status of a paper in SIMBAD?" in this FAQ, to find the current status of your paper.

    Be aware that preprints from arXiv are never processed in SIMBAD.

  • Not all journals are systematically processed in SIMBAD. The list of journals and periodicals scanned or having been scanned for the SIMBAD bibliography is impressive.

    This list includes a number of additional publications, including colloquia and symposia which are scanned or have been scanned, but not in a systematic way.

    Only a limited number of journals and periodicals (including all major reference journals, such as A&A, MNRAS, AJ, ApJ) are currently systematically processed, due to the dramatic increase in the total number of publications, and the limited CDS manpower.

If you feel that a paper is missing due to an error in the processing, you can contact us by email.

You can also use the CDS annotations service to add an annotation to a SIMBAD object.

How do I report an error in the contents of SIMBAD?

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.

The data contained in SIMBAD are 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 coordinated by Cécile Loup.

You can also use the CDS annotations service to add an annotation to a SIMBAD object and share remarks with the community. Each object result page contains a link at the bottom to "report an error concerning the data of this object", and send a notification to the SIMBAD team.

How do I check the status of a paper in SIMBAD?

You can use the paper bibcode or DOI in the SIMBAD reference query form to find its status.

You can then check the meaning of the status of your paper in the following document summarizing how we process your article at CDS.

Why is this object missing in SIMBAD?

SIMBAD only contains 17,130,400 objects. This is a small number compared to large catalogues such as 2MASS, SDSS, or Gaia DR3, containing in the 10^8 or 10^9 objects.

The explanation lies in the very nature of SIMBAD :

  • 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 wavelengths 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.

  • In the past, catalogues like 1RXS or IRAS have been enterely put in Simbad, but we do not do that anymore, because the number of objects is increasing exponentially, and because usually only a small percentage of a whole catalogue is actually studied in the literature. We do not want to put all SDSS or 2MASS objects in SIMBAD because SIMBAD focuses on the objects of interest.

We therefore do not systematically process all the catalogues in SIMBAD, and SIMBAD will not contain all astronomical sources ever detected in the sky. But you can use both SIMBAD and VizieR (containing published lists of objects, as well as most very large surveys) as complementary research tools.

You can find more details on catalogues processing in SIMBAD.

Usage of SIMBAD

Where can I have a list of all object types used in Simbad?

You can see all object types and their relations in the SIMBAD otypes page.

You can change the output (top left) to visualise them in a tabular or hierarchical view.

How to cite the usage of SIMBAD? See how to acknowledge SIMBAD usage?
How to group/sort a list of objects according to the spectral type ? First, in the Output Options (yellow link at the top of the SIMBAD query page), you should check the Spectral type for list display. Then, you can click on the arrow in the head of the table, in the spectral type column, to sort the result.
How can I see the distance of a list of objects?

In the Output Options (yellow link at the top of the SIMBAD query page) you can check the Measurements box for a list display (second column) and choose:

  • catalog list: Distance
  • display first measurement

Output options for distance in list results


Why is my IP blacklisted?

If you can't access SIMBAD, your computer's IP address might have been blacklisted.

In order to prevent abuse, the number of SIMBAD queries is limited to 10 queries per second from a single IP address. Exceeding this limit will result in the following restrictions :

  • If more than 10 queries are received in one second from the same IP address, this IP gets banned for 1 minute.
  • If more than 400 queries are received in 10 seconds from the same IP address, this IP gets banned for 1 hour.

This temporary blacklisting is automatic. You might try the following solutions to avoid the problem :

  • Add a delay between queries if you are using a script, e.g. time.sleep(300)
  • Avoid querying too many individual SIMBAD objects. There are better dedicated methods to query SIMBAD for a list of objects :

If you are accessing the web from behind a firewall, you might be sharing the same IP address with other users in your local network.

These users might be responsible for the ban !

If none of these help, you can contact us.

Can I query Simbad with Python? You can use the astroquery.simbad module to query Simbad in many different ways.