science

NGC 1851

NGC 1851 is a science 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 NGC 1851 rather than just read about it. In short: NGC 1851 (also known as Caldwell 73) is a relatively massive globular cluster located in the southern constellation of Columba. Astronomer John Dreyer described it as not very bright but very large, round, well resolved, and clearly consisting of stars.

Key takeaways

NGC 1851 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NGC 1851 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 1851 from memory before moving on to harder problems.

Reference excerpt

NGC 1851 (also known as Caldwell 73) is a relatively massive globular cluster located in the southern constellation of Columba. Astronomer John Dreyer described it as not very bright but very large, round, well resolved, and clearly consisting of stars. It is located 39.5 kilolight-years from the Sun, and 54.1 kilolight-years from the Galactic Center. The cluster is following a highly eccentric orbit through the galaxy, with an eccentricity of about 0.7. This object has a Shapley–Sawyer Concentration Class of II, indicating a dense central concentration. It has one of the highest concentrations known for Galactic globular clusters. The stellar components show two separate populations of subgiant stars, with the brighter branch being more concentrated in the outer regions of the cluster. NGC 1851 is an estimated 9.2 billion years old with 551,000 times the mass of the Sun. The cluster is surrounded by a diffuse halo of stars that stretches outward to a radius of 240 pc or more. This feature, if combined with the lack of tidal tail or associated stream of stars, suggests the cluster may be a stripped dwarf galaxy nucleus, similar to Omega Centauri, that has been accreted by the Milky Way. The tidal tail is still present though. It is also possible the cluster is the result of the merger of two separate clusters, but the fact that they would need to have the same metallicity – what astronomers term the abundance of elements other than hydrogen and helium – makes this scenario less likely. PSR J0514-4002A is a millisecond pulsar in NGC 1851. It is orbiting a massive object that may also be a neutron star. The pair have an orbital period of 18.8 days with a large eccentricity of 0.89. A nearby pulsar PSR J0514−4002E is orbiting a massive object which appears to occupy the "mass gap" between the heaviest neutron stars and the lightest black holes, making it an unusual star system which may be useful for studying theories of gravity. The TRAPUM Large Survey Project using the MeerKAT radio telescope discovered thirteen new pulsars in the cluster, which consist of six isolated millisecond pulsars (MSPs) and seven binary pulsars, of which six are MSPs and one is mildly recycled. 43 RR Lyrae variables have been discovered in the cluster, which show this to be an Oosterhoff type I cluster but having properties similar to type II. Two populations of horizontal branch stars have been observed, with the pair having an age difference of around two billion years. Spectroscopic analysis of the red giant branch member stars suggests there are actually three different populations of stars in the cluster.

Possible central black hole Based on the eccentricity of some pulsars, the cluster's core may contain a central intermediate-mass black hole with a mass of up to 7,500 M⊙, .

References

External links Media related to NGC 1851 at Wikimedia Commons Galex image of NGC 1851

NGC 1851 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images The globular cluster NGC1851 "SEDS Milky Way Globular Clusters". Results for NGC 1851. Retrieved 2011-01-09.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 1851

Start with the simplest possible case. Write down what NGC 1851 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 NGC 1851 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 NGC 1851 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 NGC 1851

In research: NGC 1851 appears in science 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 NGC 1851 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: NGC 1851 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Caldwell objects, Columba (constellation), Globular clusters, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 1851 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 NGC 1851 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 1851 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 NGC 1851 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 1851 in simple terms?

Why does NGC 1851 matter?

Because it connects several science 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 NGC 1851?

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 NGC 1851.