astronomy

HD 148937

HD 148937 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 HD 148937 rather than just read about it. In short: HD 148937 is a likely binary star system in the southern constellation of Norma. It has a combined apparent visual magnitude of 6.73, a brightness that is below the limit for being readily visible to the naked eye.

Key takeaways

HD 148937 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 148937 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 148937 from memory before moving on to harder problems.

Reference excerpt

HD 148937 is a likely binary star system in the southern constellation of Norma. It has a combined apparent visual magnitude of 6.73, a brightness that is below the limit for being readily visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 3,900 light years from Sun, but is drifting closer with a radial velocity of about −54 km/s. The star is located in the hourglass-shaped emission nebula NGC 6164/65, which it generated through episodes of mass ejection.

Observations In 1955, C. S. Gum identified HD 148937 and possibly 15 Sagittarii as responsible for the emission from the region of NGC 6164/65. In 1959, K. G. Heinze catalogued NGC 6164/65 as a planetary nebula and placed HD 148937 at its center, with the two nebulae and the star being co-linear. However, the apparent brightness of HD 148937 is brighter than any other nucleus for a nebula of this class, and the spectra of the star raised questions about their evolutionary status. B. E. Westerlund classified the star as class O6fp in 1960, with the 'O' meaning an O-type star, 'f' indicating emission from ionized helium and nitrogen, and the 'p' meaning an unspecified peculiarity. He found a series of symmetrical nebular shells surrounding the star at angular separations of 3′, 4′, and 44′–64′.

In 1970, R. M. Catchpole and M. W. Feast showed that the radial velocities for the two nebulae are consistent with them being ejecta expanding away from the central star. A very luminous absolute visual magnitude of −6 was confirmed for the central star in 1972, which demonstrated that the surroundings are not a planetary nebula. This star lies within an H II region spanning 2°, which is surrounded by a thin dust shell. In 1980, the star showed a mass loss rate of 2×10−7 M☉·yr−1, similar to other O-type main-sequence stars. An abundance analysis of the surrounding nebulae in 1987 demonstrated a strong overabundance of nitrogen, which most likely comes from stellar processing. This indicates the star is evolved, rather than being in a pre-main-sequence phase. The estimated mass of the NGC 6164/6165 nebulae is twice the mass of the Sun, and it shows a kinetic age of 3×103 yr. The surrounding stellar wind bubble is much older at 2×105 yr. In 2008, a magnetic field with a longitudinal strength of −276±88 G was detected in the star. It shows spectroscopic variability with a period of 7.031±0.003 d, and has a nitrogen enhancement of about four times that in the Sun. Based on variations in the magnetic field strength, the seven day variance is interpreted as the stellar rotation period. X-ray emission has been detected and is interpreted as originating in hot plasma about one stellar radius from the photosphere. Observations of the star made between 2015 and 2019 showed a significant change in the spectrum. Radial velocity measurements made during this period suggest that this is a double-lined spectroscopic binary system of high mass stars. Initial measurements suggest they have an eccentric orbit with a period of about 26 years and an orbital eccentricity of 0.75. Only one member of the pair is magnetic, and it appears younger than the companion. This younger star may have been formed by a merger with a third member of the system, an event that can explain both the magnetic field and the surrounding nebula.

References

Worked examples

Example 1 — a first encounter with HD 148937

Start with the simplest possible case. Write down what HD 148937 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 HD 148937 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 HD 148937 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 HD 148937

In research: HD 148937 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 HD 148937 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: HD 148937 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Henry Draper Catalogue objects, Hipparcos objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 148937 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “HD 148937” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study HD 148937 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 148937 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 HD 148937 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 148937 in simple terms?

Why does HD 148937 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 HD 148937?

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 HD 148937.