Deep-sky object

Last updated September 09, 2024

A deep-sky object (DSO) is any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.).^[1]^[2] The classification is used for the most part by amateur astronomers to denote visually observed faint naked eye and telescopic objects such as star clusters, nebulae and galaxies. This distinction is practical and technical, implying a variety of instruments and techniques appropriate to observation, and does not distinguish the nature of the object itself.

Origins and classification

Classifying non-stellar astronomical objects began soon after the invention of the telescope.^[3] One of the earliest comprehensive lists was Charles Messier's 1774 Messier catalog, which included 103 "nebulae" and other faint fuzzy objects he considered a nuisance since they could be mistaken for comets, the objects he was actually searching for.^[3] As telescopes improved these faint nebulae would be broken into more descriptive scientific classifications such as interstellar clouds, star clusters, and galaxies.

"Deep-sky object", as an astronomical classification for these objects, has its origins in the modern field of amateur astronomy. The origin of the term is unknown but it was popularized by Sky & Telescope magazine's "Deep-Sky Wonders" column, which premiered in the magazine's first edition in 1941.^[4] Houston's columns, and later book compilations of those columns, helped popularize the term,^[5] each month giving the reader a guided tour of a small part of the sky highlighting well-known and lesser-known objects for binoculars and small telescopes.

Observations and activities

Map of the constellation Cygnus marking the location of bright and more challenging deep-sky objects CygnusOBmap.png — Map of the constellation Cygnus marking the location of bright and more challenging deep-sky objects

There are many amateur astronomical techniques and activities associated with deep-sky objects. Some of these objects are bright enough to find and see in binoculars and small telescopes. But the faintest objects need the light-gathering power of telescopes with large objectives,^[6] and since they are invisible to the naked eye, can be hard to find. This has led to increased popularity of GoTo telescopes that can find DSOs automatically, and large reflecting telescopes, such as Dobsonian style telescopes, with wide fields of view well suited to such observing.^[7] Observing faint objects needs dark skies, so these relatively portable types of telescopes also lend themselves to the majority of amateurs who need to travel outside light polluted urban locations.^[8] To cut down light pollution and enhance contrast, observers employ nebular filters, which are designed to admit certain wavelengths of light and block others.

There are organized activities associated with DSOs such as the Messier marathon, which occurs at a specific time each year and involves observers trying to spot all 110 Messier objects in one night. Since the Messier catalog objects were discovered with relatively small 18th-century telescopes, it is a popular list with observers, being well within the grasp of most modern amateur telescopes. The Herschel 400 Catalogue is also a popular list with observers and is considered more challenging; it was designed for larger telescopes and experienced amateur astronomers.^[9]

List of deep-sky object types

There are many astronomical object types that come under the description of deep-sky objects. Since the definition is objects that are not Solar System objects or individual stars, examples include:^[10]

Related Research Articles

Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers make contributions in doing citizen science, such as by monitoring variable stars, double stars, sunspots, or occultations of stars by the Moon or asteroids, or by discovering transient astronomical events, such as comets, galactic novae or supernovae in other galaxies.

Charles Messier was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the Messier objects, referred to with the letter M and their number between 1 and 110. Messier's purpose for the catalogue was to help astronomical observers distinguish between permanent and transient visually diffuse objects in the sky.

The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles. Because Messier was interested only in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. This list, which Messier created in collaboration with his assistant Pierre Méchain, is now known as the Messier catalogue. The Messier catalogue is one of the most famous lists of astronomical objects, and many objects on the list are still referenced by their Messier numbers. The catalogue includes most of the astronomical deep-sky objects that can be easily observed from Earth's Northern Hemisphere; many Messier objects are popular targets for amateur astronomers.

Frederick William Herschel was a German-British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline Herschel. Born in the Electorate of Hanover, William Herschel followed his father into the military band of Hanover, before emigrating to Great Britain in 1757 at the age of nineteen.

The New General Catalogue of Nebulae and Clusters of Stars is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and emission nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues, describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use.

The Ring Nebula is a planetary nebula in the northern constellation of Lyra.^[C] Such a nebula is formed when a star, during the last stages of its evolution before becoming a white dwarf, expels a vast luminous envelope of ionized gas into the surrounding interstellar space.

A Messier marathon is an attempt, usually organized by amateur astronomers, to find as many Messier objects as possible during one night. The Messier catalogue was compiled by French astronomer Charles Messier during the late 18th century and consists of 110 relatively bright deep-sky objects.

Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection.

Messier 58 is an intermediate barred spiral galaxy with a weak inner ring structure located within the constellation Virgo, approximately 68 million light-years away from Earth. It was discovered by Charles Messier on April 15, 1779 and is one of four barred spiral galaxies that appear in Messier's catalogue. M58 is one of the brightest galaxies in the Virgo Cluster. From 1779 it was arguably the farthest known astronomical object until the release of the New General Catalogue in the 1880s and even more so the publishing of redshift values in the 1920s.

Messier 91 is a barred spiral galaxy that is found in the south of Coma Berenices. It is in the local supercluster and is part of the Virgo Cluster of galaxies. It is about 63 million light-years away from our galaxy. It was the last of a group of eight "nebulae" – the term 'galaxy' only coming into use for these objects once it was realized in the 20th century that they were extragalactic – discovered by Charles Messier in 1781. It is the faintest object in the Messier catalog, with an apparent magnitude of 10.2.

<span class="mw-page-title-main">Owl Nebula</span> Planetary nebula in the constellation Ursa Major

The Owl Nebula is a planetary nebula approximately 2,030 light years away in the constellation Ursa Major. Estimated to be about 8,000 years old, it is approximately circular in cross-section with a faint internal structure. It was formed from the outflow of material from the stellar wind of the central star as it evolved along the asymptotic giant branch. The nebula is arranged in three concentric shells, with the outermost shell being about 20–30% larger than the inner shell. The owl-like appearance of the nebula is the result of an inner shell that is not circularly symmetric, but instead forms a barrel-like structure aligned at an angle of 45° to the line of sight.

Messier 93 or M93, also known as NGC 2447 or the Critter Cluster, is an open cluster in the modestly southern constellation Puppis, the imagined poop deck of the legendary Argo.

Messier 110, or M110, also known as NGC 205, is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy in the Local Group.

<span class="mw-page-title-main">NGC 3532</span> Open cluster in the constellation Carina

NGC 3532, also commonly known as the Pincushion Cluster, Football Cluster, the Black Arrow Cluster, or the Wishing Well Cluster, is an open cluster some 405 parsecs from Earth in the constellation Carina. Its population of approximately 150 stars of 7th magnitude or fainter includes seven red giants and seven white dwarfs. On 20 May 1990 it became the first target ever observed by the Hubble Space Telescope. A line from Beta Crucis through Delta Crucis passes somewhat to the north of NGC 3532. The cluster lies between the constellation Crux and the larger but fainter "False Cross" asterism. The 4th-magnitude Cepheid variable star x Carinae appears near the southeast fringes, but it lies between the Sun and the cluster and is not a member of the cluster.

The Caldwell catalogue is an astronomical catalogue of 109 star clusters, nebulae, and galaxies for observation by amateur astronomers. The list was compiled by Patrick Moore as a complement to the Messier catalogue.

The Herschel 400 catalogue is a subset of William Herschel's original Catalogue of Nebulae and Clusters of Stars, selected by Brenda F. Guzman (Branchett), Lydel Guzman, Paul Jones, James Morris, Peggy Taylor and Sara Saey of the Ancient City Astronomy Club in St. Augustine, Florida, United States c. 1980. They decided to generate the list after reading a letter published in Sky & Telescope by James Mullaney of Pittsburgh, Pennsylvania, United States.

An astronomical catalog or catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. The oldest and largest are star catalogues. Hundreds have been published, including general ones and special ones for such items as infrared stars, variable stars, giant stars, multiple star systems, star clusters, and so forth.

Steven Michael Gottlieb is an American amateur astronomer, researcher, writer and lecturer.

References

↑ Fred Schaaf (1998). 40 Nights to Knowing the Sky: A Night-by-Night Sky-Watching Primer. Henry Holt and Company. p. 113. ISBN 978-0-8050-4668-7.
↑ Ian Ridpath (2001). The Illustrated Encyclopedia of the Universe. Watson-Guptill Publications. p. 273. ISBN 978-0-8230-2512-1.
1 2 Edward W. Kolb; Rocky Kolb (1999). Blind Watchers of the Sky: The People and Ideas that Shaped Our View of the Universe. Oxford University Press. p. 174. ISBN 978-0-19-286203-7.
↑ Charles Anthony Federer (1942). Sky and Telescope. Sky Publishing Corporation.
↑ Fred Schaaf (1998). 40 Nights to Knowing the Sky: A Night-by-Night Sky-Watching Primer. Henry Holt and Company. p. 13. ISBN 978-0-8050-4668-7.
↑ Grant Privett; Paul Parsons (2001). The Deep-Sky Observer's Year: A Guide to Observing Deep-Sky Objects Throughout the Year. Springer Science & Business Media. p. 11. ISBN 978-1-85233-273-0.
↑ Rajiv Gupta (September 2004). Observer's Handbook 2005. Royal Astronomical Soc of Canada. p. 73. ISBN 978-0-9689141-8-2.
↑ The Observer's Handbook, Royal Astronomical Society of Canada, p. 63
↑ Cavin, Jerry D. (2011). The Amateur Astronomer's Guide to the Deep-Sky Catalogs. Springer New York. p. 149. ISBN 9781461406563.
↑ W.H. Finlay (2003). Concise Catalog of Deep-sky Objects: Astrophysical Information for 500 Galaxies, Clusters and Nebulae. Springer Science & Business Media. p. 10. ISBN 978-1-85233-691-2.
↑ Black hole at the Encyclopædia Britannica
↑ Active glactic nucleus at the Encyclopædia Britannica
↑ Nebula at the Encyclopædia Britannica
↑ Galaxy at the Encyclopædia Britannica
↑ Star cluster at the Encyclopædia Britannica

Neil Bone, Wil Tirion, Deep Sky Observer's Guide. Firefly Books, 2005. ISBN 1-55407-024-4.
Jess K. Gilmour, The practical astronomer's deep-sky companion. Springer, 2003. ISBN 1-85233-474-6.
Jack Newton, Philip Teece. The Guide to Amateur Astronomy. Cambridge University Press, 1995. ISBN 0-521-44492-6.
W. H. Finlay, Concise Catalog of Deep-sky Objects: Astrophysical Information for 500 Galaxies, Clusters and Nebulae. London: Springer, 2003. ISBN 1-85233-691-9. Includes the Messier objects, Herschel 400 & more.
Roger Nelson Clark, Visual astronomy of the deep sky. CUP Archive, 1990. ISBN 0-521-36155-9.

External links

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[1] Fred Schaaf (1998). 40 Nights to Knowing the Sky: A Night-by-Night Sky-Watching Primer. Henry Holt and Company. p. 113. ISBN 978-0-8050-4668-7.

[2] Ian Ridpath (2001). The Illustrated Encyclopedia of the Universe. Watson-Guptill Publications. p. 273. ISBN 978-0-8230-2512-1.

[Kolb-3] 1 2 Edward W. Kolb; Rocky Kolb (1999). Blind Watchers of the Sky: The People and Ideas that Shaped Our View of the Universe. Oxford University Press. p. 174. ISBN 978-0-19-286203-7.

[4] Charles Anthony Federer (1942). Sky and Telescope. Sky Publishing Corporation.

[5] Fred Schaaf (1998). 40 Nights to Knowing the Sky: A Night-by-Night Sky-Watching Primer. Henry Holt and Company. p. 13. ISBN 978-0-8050-4668-7.

[6] Grant Privett; Paul Parsons (2001). The Deep-Sky Observer's Year: A Guide to Observing Deep-Sky Objects Throughout the Year. Springer Science & Business Media. p. 11. ISBN 978-1-85233-273-0.

[7] Rajiv Gupta (September 2004). Observer's Handbook 2005. Royal Astronomical Soc of Canada. p. 73. ISBN 978-0-9689141-8-2.

[8] The Observer's Handbook, Royal Astronomical Society of Canada, p. 63

[9] Cavin, Jerry D. (2011). The Amateur Astronomer's Guide to the Deep-Sky Catalogs. Springer New York. p. 149. ISBN 9781461406563.

[10] W.H. Finlay (2003). Concise Catalog of Deep-sky Objects: Astrophysical Information for 500 Galaxies, Clusters and Nebulae. Springer Science & Business Media. p. 10. ISBN 978-1-85233-691-2.

[11] Black hole at the Encyclopædia Britannica

[12] Active glactic nucleus at the Encyclopædia Britannica

[13] Nebula at the Encyclopædia Britannica

[14] Galaxy at the Encyclopædia Britannica

[15] Star cluster at the Encyclopædia Britannica

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