astronomy

Messier 65

Messier 65 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 Messier 65 rather than just read about it. In short: Messier 65 (also known as NGC 3623) is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo, within its highly equatorial southern half. It was discovered by Charles Messier in 1780.

Key takeaways

Messier 65 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Messier 65 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 65 from memory before moving on to harder problems.

Reference excerpt

Messier 65 (also known as NGC 3623) is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo, within its highly equatorial southern half. It was discovered by Charles Messier in 1780. With M66 and NGC 3628, it forms the Leo Triplet, a small close group of galaxies.

Discovery M65 was discovered by Charles Messier and included in his Messier Objects list. However, William Henry Smyth accidentally attributed the discovery to Pierre Méchain in his popular 19th-century astronomical work A Cycle of Celestial Objects (stating "They [M65 and M66] were pointed out by Méchain to Messier in 1780"). This error was, in turn, picked up by Kenneth Glyn Jones in Messier's Nebulae and Star Clusters. This has since ramified into a number of other books by a variety of authors.

Star formation The galaxy is low in dust and gas, and there is little star formation in it, although there has been some relatively recently in the arms. The ratio of old stars to new stars is correspondingly quite high. In most wavelengths, it is quite uninteresting, though there is a radio source visible in the NVSS, offset from the core by about two arc-minutes. The identity of the source is uncertain, as it has not been identified visually or formally studied in any published papers.

Interaction with other galaxies To the eye, M65's disk appears slightly warped, and its relatively recent burst of star formation is also suggestive of some external disturbance. Rots (1978) suggests that the two other galaxies in the Leo Triplet interacted with each other about 800 million years ago. Recent research by Zhiyu Duan suggests that M65 may also have interacted, though much less strongly. He also notes that M65 may have a central bar—it is difficult to tell because the galaxy is seen from an oblique angle—a feature which is suggestive of tidal disruption.

Supernova One supernova has been observed in Messier 65:

SN 2013am (Type II, mag. 15.6) was discovered by Matsuo Sugano on 21 March 2013.

Gallery

Illustrations

Worked examples

Example 1 — a first encounter with Messier 65

Start with the simplest possible case. Write down what Messier 65 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 Messier 65 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 Messier 65 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 Messier 65

In research: Messier 65 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 Messier 65 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: Messier 65 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1780, Discoveries by Charles Messier, Intermediate spiral galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 65 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 Messier 65 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 65 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 Messier 65 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 65 in simple terms?

Why does Messier 65 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 Messier 65?

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 Messier 65.