astronomy

RS Ophiuchi

RS Ophiuchi is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand RS Ophiuchi rather than just read about it. In short: RS Ophiuchi (RS Oph) is a recurrent nova system approximately 5,000 light-years away in the constellation Ophiuchus. In its quiet phase it has an apparent magnitude of about 12.5.

Key takeaways

RS Ophiuchi belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect RS Ophiuchi to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of RS Ophiuchi from memory before moving on to harder problems.

Reference excerpt

RS Ophiuchi (RS Oph) is a recurrent nova system approximately 5,000 light-years away in the constellation Ophiuchus. In its quiet phase it has an apparent magnitude 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 star and a red giant 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. The nova is surrounded by a 70 parsecs (230 light-years) nova super-remnant (not to be confused with supernova remnant). The nova remnant has an estimated mass between 20 and 200 M☉ and an age between 50 and 100,000 years. Such remants may be common among all reccurent novae, but due to their faint brightness, very few have been discovered.

Properties RS Ophiuchi is a system consisting of a white dwarf with a red giant 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 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 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, Italy. 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, 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 of Peterborough, Canada 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, Brazil 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 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

Schaefer, B. E. (2010). "Comprehensive Photometric Histories of All Known Galactic Recurrent Novae". Astrophysical Journal. 187 (2): 275–373. arXiv:0912.4426. Bibcode:2010ApJS..187..275S. doi:10.1088/0067-0049/187/2/275. S2CID 119294221.

External links

"V* RS Oph". SIMBAD. Centre de données astronomiques de Strasbourg. Entry at Astronomy Picture of the Day Entry in the Variable Star Index AAVSO

Illustrations

Worked examples

Example 1 — a first encounter with RS Ophiuchi

Start with the simplest possible case. Write down what RS Ophiuchi claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to RS Ophiuchi before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about RS Ophiuchi ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of RS Ophiuchi

In research: RS Ophiuchi appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses RS Ophiuchi in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: RS Ophiuchi is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1904, Discoveries by Williamina Fleming, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for RS Ophiuchi outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study RS Ophiuchi in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what RS Ophiuchi means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain RS Ophiuchi out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is RS Ophiuchi in simple terms?

RS Ophiuchi (RS Oph) is a recurrent nova system approximately 5,000 light-years away in the constellation Ophiuchus. In its quiet phase it has an apparent magnitude of about 12.5.

Why does RS Ophiuchi matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study RS Ophiuchi?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on RS Ophiuchi.