VOEvent
Encyclopedia
VOEvent is a standardized language used to report observations of astronomical
events; it was officially adopted in 2006 by the International Virtual Observatory Alliance
(IVOA). Though most VOEvent messages currently issued are related to supernova
e, gravitational microlensing
, and gamma-ray bursts
, they are intended to be general enough to describe all types of observations of astronomical events, including gravitational wave events. Messages are written in XML
, providing a structured metadata
description of both the observations and the inferences derived from those observations. The rapid dissemination of event data with a formalized language was the
original impetus for the creation of VOEvents and the network (now called VOEventNet) used to transport the messages; indeed VOEvent messages are designed to be compact and quickly transmittable over the internet. The VOEvent language (which is codified in an XML schema) continues to evolve; the latest version is 1.11.
Central Bureau for Astronomical Telegrams
(IAUCs and CBETs) and the Astronomer's Telegrams (ATELs). The principal difference is that VOEvent messages are intended to be automatically parsed
and filtered
whereas ATELs and IAUCs are intended to be read by humans. The scope of VOEvent is informed by several other messaging schemes used to facilitate rapid discovery announcements for specialized sub-fields of astronomy (such as OGLE microlensing alerts
and Supernova Early Warning System
). The closest ancestors of VOEvent are The Telescope Alert Operation Network System (TALON) and the Gamma Ray Burst Coordinates Network
(GCN) messages, used extensively by the gamma-ray burst
community.
:
A well-formed VOEvent message must validate
against the VOEvent schema (.xsd). A valid message may omit most of the informational tags listed above, but since the creation of VOEvent messages is done automatically, most opt to transmit the fullest content available.
, there are no promises that once a VOEvent message has been issued, it will persist indefinitely. It is the role of the publisher, generally, to maintain and curate VOEvents issued. Still, public VOEvent messages may be distributed and or archived through 3rd parties.
(through a variety of protocols, such as RSS
and XMPP
) currently available from:
mashup
of microlensing events.
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
events; it was officially adopted in 2006 by the International Virtual Observatory Alliance
IVOA
The International Virtual Observatory Alliance or IVOA is a worldwide scientific organisation formed in June 2002. Its mission is to facilitate international coordination and collaboration necessary for enabling global and integrated access to data gathered by astronomical observatories. An...
(IVOA). Though most VOEvent messages currently issued are related to supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
e, gravitational microlensing
Gravitational microlensing
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects ranging from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit lots of light ...
, and gamma-ray bursts
Gamma ray burst
Gamma-ray bursts are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the most luminous electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several minutes, although a typical...
, they are intended to be general enough to describe all types of observations of astronomical events, including gravitational wave events. Messages are written in XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
, providing a structured metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
description of both the observations and the inferences derived from those observations. The rapid dissemination of event data with a formalized language was the
original impetus for the creation of VOEvents and the network (now called VOEventNet) used to transport the messages; indeed VOEvent messages are designed to be compact and quickly transmittable over the internet. The VOEvent language (which is codified in an XML schema) continues to evolve; the latest version is 1.11.
History
VOEvent builds upon previous generic publishing schemes such as International Astronomical UnionInternational Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
Central Bureau for Astronomical Telegrams
Central Bureau for Astronomical Telegrams
The Central Bureau for Astronomical Telegrams is the official international clearing house for information relating to transient astronomical events....
(IAUCs and CBETs) and the Astronomer's Telegrams (ATELs). The principal difference is that VOEvent messages are intended to be automatically parsed
Parsing
In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens , to determine its grammatical structure with respect to a given formal grammar...
and filtered
Filter (software)
A filter is a computer program to process a data stream. Some operating systems such as Unix are rich with filter programs. Even Windows has some simple filters built into its command shell, most of which have significant enhancements relative to the similar filter commands that were available in...
whereas ATELs and IAUCs are intended to be read by humans. The scope of VOEvent is informed by several other messaging schemes used to facilitate rapid discovery announcements for specialized sub-fields of astronomy (such as OGLE microlensing alerts
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...
and Supernova Early Warning System
Supernova Early Warning System
The SuperNova Early Warning System is a network of neutrino detectors designed to give early warning to astronomers in the event of a supernova in the Milky Way galaxy or a nearby galaxy such as the Large Magellanic Cloud or the Canis Major Dwarf Galaxy. Enormous numbers of neutrinos are produced...
). The closest ancestors of VOEvent are The Telescope Alert Operation Network System (TALON) and the Gamma Ray Burst Coordinates Network
Gamma Ray Burst Coordinates Network
The Gamma-ray burst Coordinates Network is a system that distributes information about the location of a Gamma-ray burst , called Notices, when a burst is detected by various spacecraft. The GCN also automatically receives and distributes messages, called Circulars, about follow-up observations to...
(GCN) messages, used extensively by the gamma-ray burst
Gamma ray burst
Gamma-ray bursts are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the most luminous electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several minutes, although a typical...
community.
Structure of the Language
A typical VOEvent message contains the following tagsTag (metadata)
In online computer systems terminology, a tag is a non-hierarchical keyword or term assigned to a piece of information . This kind of metadata helps describe an item and allows it to be found again by browsing or searching...
:
-
- describing who is responsible (the author and the publisher) for the information contained in the message -
- a description of the instrumental setup on where the data were obtained -
- the data (such as source flux) associated with the observations of the event -
- inferences about the nature of the event -
- description of the time and place where the event was recorded. This draws from the Space-time Coordinate (STC) recommendation to the IVOA IVOAThe International Virtual Observatory Alliance or IVOA is a worldwide scientific organisation formed in June 2002. Its mission is to facilitate international coordination and collaboration necessary for enabling global and integrated access to data gathered by astronomical observatories. An...
.
A well-formed VOEvent message must validate
XML Validation
XML validation is the process of checking a document written in XML to confirm that it is both "well-formed" and also "valid" in that it follows a defined structure. A "well-formed" document follows the basic syntactic rules of XML, which are the same for all XML documents...
against the VOEvent schema (.xsd). A valid message may omit most of the informational tags listed above, but since the creation of VOEvent messages is done automatically, most opt to transmit the fullest content available.
Current uses
As with most products of the Virtual ObservatoryVirtual Observatory
Virtual observatory is a collection of interoperating data archives and software tools which utilize the internet to form a scientific research environment in which astronomical research programs can be conducted....
, there are no promises that once a VOEvent message has been issued, it will persist indefinitely. It is the role of the publisher, generally, to maintain and curate VOEvents issued. Still, public VOEvent messages may be distributed and or archived through 3rd parties.
VOEvent feeds
There are live VOEvent feedsWeb feed
A web feed is a data format used for providing users with frequently updated content. Content distributors syndicate a web feed, thereby allowing users to subscribe to it. Making a collection of web feeds accessible in one spot is known as aggregation, which is performed by an aggregator...
(through a variety of protocols, such as RSS
RSS
-Mathematics:* Root-sum-square, the square root of the sum of the squares of the elements of a data set* Residual sum of squares in statistics-Technology:* RSS , "Really Simple Syndication" or "Rich Site Summary", a family of web feed formats...
and XMPP
Extensible Messaging and Presence Protocol
Extensible Messaging and Presence Protocol is an open-standard communications protocol for message-oriented middleware based on XML . The protocol was originally named Jabber, and was developed by the Jabber open-source community in 1999 for near-real-time, extensible instant messaging , presence...
) currently available from:
- The Skyalert project at Caltech.
- eStar (ExeterExeterExeter is a historic city in Devon, England. It lies within the ceremonial county of Devon, of which it is the county town as well as the home of Devon County Council. Currently the administrative area has the status of a non-metropolitan district, and is therefore under the administration of the...
, EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
)
Vizualizations
Since VOEvents note the location and time events, it is possible to convert streams of events into temporal or spatial visualizations. Skyalert has Worldwide Telescope views of the event sky. eStar hosts an AJAXAjax
- Mythology :* Ajax , son of Telamon, ruler of Salamis and a hero in the Trojan War, also known as "Ajax the Great"* Ajax the Lesser, son of Oileus, ruler of Locris and the leader of the Locrian contingent during the Trojan War.- People :...
mashup
Mashup (web application hybrid)
In Web development, a mashup is a Web page or application that uses and combines data, presentation or functionality from two or more sources to create new services...
of microlensing events.
External links
- Description of the VOEvent language (latest version is 1.11)
- IVOA VOEvent Working Group
- Astronomer's Telegrams
- Space-time Coordinate (STC) recommendation to the IVOAIVOAThe International Virtual Observatory Alliance or IVOA is a worldwide scientific organisation formed in June 2002. Its mission is to facilitate international coordination and collaboration necessary for enabling global and integrated access to data gathered by astronomical observatories. An...