astronomy

NGC 4045

NGC 4045 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 NGC 4045 rather than just read about it. In short: NGC 4045 is a barred spiral galaxy in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 2,334±25 km/s, which corresponds to a Hubble distance of 112.3 ± 8.0 Mly (34.42 ± 2.44 Mpc).

Key takeaways

NGC 4045 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NGC 4045 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4045 from memory before moving on to harder problems.

Reference excerpt

NGC 4045 is a barred spiral galaxy in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 2,334±25 km/s, which corresponds to a Hubble distance of 112.3 ± 8.0 Mly (34.42 ± 2.44 Mpc). However, 15 non-redshift measurements give a closer mean distance of 100.24 ± 2.77 Mly (30.733 ± 0.849 Mpc). It was discovered by German-British astronomer William Herschel on 20 December 1784. It was also observed by German astronomer Heinrich Louis d'Arrest on 10 April 1863, causing it to be listed a second time in the New General Catalogue, as NGC 4046. NGC 4045 is a LINER galaxy, i.e. a galaxy whose nucleus has an emission spectrum characterized by broad lines of weakly ionized atoms. Also, the galaxy is listed as having an active galactic nucleus, and as being a radio galaxy. NGC 4045 and neighboring galaxy PGC 38033 (also known as NGC 4045A) are listed together as Holm 320 in Erik Holmberg's A Study of Double and Multiple Galaxies Together with Inquiries into some General Metagalactic Problems, published in 1937. However, since PGC 38033 is over twice as distant (~81.6 Mpc) as NGC 4045, the grouping is purely an optical alignment.

Supernova and luminous blue variable One supernova has been observed in NGC 4045:

SN 1985B (Type II, mag. 13) was discovered by Shingo Horiguchi on 17 January 1985. A 1987 study classified this supernova as Type Ia. One luminous blue variable has been observed in NGC 4045:

AT 2019wbg (Type LBV, mag. 18.775) was discovered by ATLAS on 3 December 2019. It was initially classified as a supernova impostor, then as a Type IIn supernova. In June 2020 it was finally classified as a luminous blue variable, due to its continued up-and-down variability and low luminosity. Since then, it has exhibited repeated outbursts which have confirmed this classification.

See also List of NGC objects (4001–5000)

References

External links Media related to NGC 4045 at Wikimedia Commons NGC 4045 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Illustrations

Worked examples

Example 1 — a first encounter with NGC 4045

Start with the simplest possible case. Write down what NGC 4045 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 NGC 4045 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 4045 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 4045

In research: NGC 4045 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 NGC 4045 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 4045 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Barred spiral galaxies, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 4045 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 4045 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4045 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 4045 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4045 in simple terms?

Why does NGC 4045 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 NGC 4045?

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 4045.