RS Ophiuchi (''RS Oph'') is a recurrent
nova system approximately 5,000
light-year
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s away in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
Ophiuchus
Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constellati ...
. In its quiet phase it has an
apparent magnitude
Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
of about 12.5. It has been observed to erupt in 1898, 1933, 1958, 1967, 1985, 2006 and 2021 and reached about magnitude 5 on average. A further two eruptions, in 1907 and 1945, have been inferred from archival data. The recurrent nova is produced by a
white dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
star and a
red giant
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
in a
binary system. About every 15 years, enough material from the red giant builds up on the surface of the white dwarf to produce a
thermonuclear explosion. The white dwarf orbits close to the red giant, with an
accretion disc concentrating the overflowing atmosphere of the red giant onto the white dwarf.
Properties
RS Ophiuchi is a system consisting of a
white dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
with a
red giant
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
companion. The stars are in a
binary system with an orbital period of around 454 days.
Eruptive history
The chart below shows when every recorded nova had occurred since the first confirmed one in the year of 1898.
1898

The 1898 eruption was, in fact, not discovered until several years after it happened.
Williamina Fleming
Williamina Paton Stevens Fleming (15 May 1857 – 21 May 1911) was a pioneering Scottish astronomer, who made significant contributions to the field despite facing gender biases. She was a single mother hired by the director of the Harvard Co ...
discovered a nova-like spectrum in the Henry Draper Memorial photographs and announced it as a potential nova in 1904. This diagnosis was affirmed by
Edward Charles Pickering in 1905, after which
Annie Jump Cannon
Annie Jump Cannon (; December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification. With Edward C. Pickering, she is credited with the creation of ...
determined that RS Ophiuchi had likely reached maximum in 1898.
1907
Though the 1907 eruption was not observed during outburst, measurements of a dip in brightness from archival observations suggests that RS Oph underwent an eruption in early 1907 during a time when it was obscured by the sun.
1933
The 1933 outburst was first detected by
Eppe Loreta, from
Bologna
Bologna ( , , ; ; ) is the capital and largest city of the Emilia-Romagna region in northern Italy. It is the List of cities in Italy, seventh most populous city in Italy, with about 400,000 inhabitants and 150 different nationalities. Its M ...
,
Italy
Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
. Loreta had been observing
Y Ophiuchi when he serendipitously noticed a bright object about 50 arcminutes southwest of Y Oph. The detection of this luminous star resulted in the second recorded outburst of RS Oph. An independent discovery of this activity was made several days later by
Leslie Peltier (P) while making his routine check of the variable.
1945
The 1945 eruption was also inferred from archival data after the outburst as a result of obscuration from the sun during the peak brightness. This eruption is more certain than that in 1907, as the tail of the eruption was also observed.
1958
The 1958 outburst was detected by
Cyrus Fernald
Cyrus () is a Persian-language masculine given name. It is historically best known as the name of several List of monarchs of Iran, Persian kings, most notably including Cyrus the Great, who founded the Achaemenid Empire in 550 BC. It remains wid ...
, located in
Longwood, Florida. Fernald's monthly report for July 1958, containing 345 observations, displays a note in which he comments ''"Not too good of a month outside of the RS Oph observations (19 in total). It was interesting to watch the change in color as the star faded. It was reddish-yellow the first night, then yellowish-red, and so on. The last observation was the reddest star that I have ever seen."'' The crimson color of which Fernald speaks is indicative of the strong H-alpha emission displayed in the several days following the outburst.
1967
The 1967 outburst was again detected by Cyrus Fernald (FE), however, Fernald was not given credit for the earliest observation of maximum. For on the same evening, Dr. Max Beyer (BY), located in Hamburg, Germany, observed the variable at 6th magnitude. Due to the 6-hour difference in time zones, Dr. Beyer was credited with the first report.
1985
In January 1985,
Warren Morrison
Warren most commonly refers to:
* Warren (burrow), a network dug by rabbits
* Warren (name), a given name and a surname, including lists of persons so named
Warren may also refer to:
Places Australia
* Warren (biogeographic region)
* Warren ...
of
Peterborough
Peterborough ( ) is a City status in the United Kingdom, cathedral city in the City of Peterborough district in the Ceremonial counties of England, ceremonial county of Cambridgeshire, England. The city is north of London, on the River Nene. A ...
,
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
discovered RS Oph to again be in outburst, reaching a maximum brightness of magnitude 5.4.
2006
On 12 February 2006 a new outburst occurred, reaching magnitude 4.5. The opportunity was taken to observe it at different wavelengths.
It was notably observed with the VLTI by
Olivier Chesneau, who discovered an elongated fireball as early as 5.5 days after the explosion (see the figure below). Silicate dust and
SiO emissions were observed after eruptuon.
2021
On 8 August 2021, the Brazilian amateur astronomer
Alexandre Amorim, from
Florianópolis
Florianópolis () is the capital and second largest city of the state of Santa Catarina (state), Santa Catarina, in the South Region, Brazil, South region of Brazil. The city encompasses Santa Catarina Island and surrounding small islands, as we ...
,
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
detected a new outburst of RS Oph at 21:55 UT and sent a notification to
AAVSO.
The outbust was confirmed by an independent observation of Keith Geary from
Ireland
Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...
at 22:20 UT.
The
Fermi Gamma Ray Space Telescope corroborated optical observations made by Amorim and Geary of a new outburst associated with RS Oph, with an estimated visual magnitude of 5.0.
It reached a peak visual magnitude of approximately 4.6 the following day.
References
Bibliography

*
External links
*
Entry at Astronomy Picture of the Day
Entry in the Variable Star IndexAAVSO
{{DEFAULTSORT:RS Ophiuchi
Recurrent novae
Ophiuchus
M-type giants
Ophiuchi, RS
162214
Durchmusterung objects