astronomy

Messier 29

Messier 29 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 29 rather than just read about it. In short: Messier 29 or M29, also known as NGC 6913 or the Cooling Tower Cluster, is a quite small, bright open cluster of stars just south of the central bright star Gamma Cygni of a northerly zone of the sky, Cygnus. It was discovered by Charles Messier in 1764, and can be seen from Earth by using binoculars.

Key takeaways

Messier 29 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 29 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 29 from memory before moving on to harder problems.

Reference excerpt

Messier 29 or M29, also known as NGC 6913 or the Cooling Tower Cluster, is a quite small, bright open cluster of stars just south of the central bright star Gamma Cygni of a northerly zone of the sky, Cygnus. It was discovered by Charles Messier in 1764, and can be seen from Earth by using binoculars. M29 is well within the several degrees of the arms and bulge of the Milky Way. It is at least many hundreds of light years short of the yardstick distance to the Galactic Center, as is between 4,000 and 7,200 light years away. A 1998 popular work gives a value within this range. Data from Gaia EDR3 gives a parallactic distance of about 5,240 light years. The uncertainty is due to poorly known absorption of the cluster's light. Its extinction greatly is from faint surrounding nebulosity and other foreground interstellar matter of this cross-section of the spiral arms (see Orion–Cygnus Arm, which is our local arm). According to the Sky Catalogue, M29 is included in the Cygnus OB1 association, and the radial velocity component of three-dimensional motion, by default factoring in the solar system's current trajectory, is one of approaching at 28 km/s (noted, thus, as negative). Its age is estimated at 10 million years, as its five hottest stars are all giants of spectral class B0. Kepple and his associates give the apparent brightness of the brightest star as eighth magnitude of in the mid-wavelength (and frequency) "visual" band. The cluster's absolute magnitude is estimated at −8.2, a luminosity of 160,000 solar luminosities (L☉). The linear diameter was estimated at only 11 light years. Its Trumpler class is III,3,p,n (as it is associated with nebulosity), although Götz gives, differently, II,3,m, and Kepple gives I,2,m,n. The Sky Catalogue lists it with 50 member stars; earlier Becvar estimated 20 members. North of 47 degrees north, the cluster is for part or all of the day above the horizon. It can be made out in binoculars in a good sky. In telescopes, lowest powers are best. The brightest of its stars form a "stubby dipper", per Mallas. The four brightest stars form a quadrilateral, and another set a small triangle just north of the northernmost of the four. It is often known as the "cooling tower" due to its resemblance to the hyperboloid-shaped structures. A few fainter stars are around them, but the cluster appears quite isolated, especially in smaller telescopes. In photographs, many faint Milky Way background stars appear. Messier 29 can be found quite easily as it is about 1.7 degrees south of Gamma or 37 Cygni (Sadr). Angularly close, and almost certainly nearby in space, is diffuse nebulosity. The especially hot binary Wolf–Rayet star WR 143 (WC4+Be) (HD 195177) can be found near this cluster.

Illustrations

Worked examples

Example 1 — a first encounter with Messier 29

Start with the simplest possible case. Write down what Messier 29 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 29 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 29 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 29

In research: Messier 29 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 29 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 29 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1764, Cygnus (constellation), Discoveries by Charles Messier, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 29 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 29 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 29 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 29 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 29 in simple terms?

Why does Messier 29 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 29?

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 29.