astronomy

Messier 99

Messier 99 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 99 rather than just read about it. In short: Messier 99 or M99, also known as NGC 4254 or St. Catherine's Wheel, is a grand design spiral galaxy in the northern constellation Coma Berenices approximately 15,000,000 parsecs (49,000,000 light-years) from the Milky Way.

Key takeaways

Messier 99 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 99 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 99 from memory before moving on to harder problems.

Reference excerpt

Messier 99 or M99, also known as NGC 4254 or St. Catherine's Wheel, is a grand design spiral galaxy in the northern constellation Coma Berenices approximately 15,000,000 parsecs (49,000,000 light-years) from the Milky Way. It was discovered by Pierre Méchain on 17 March 1781. The discovery was then reported to Charles Messier, who included the object in the Messier Catalogue of comet-like objects. It was one of the first galaxies in which a spiral pattern was seen. This pattern was first identified by Lord Rosse in the spring of 1846. This galaxy has a morphological classification of SA(s)c, indicating a pure spiral shape with loosely wound arms. It has a peculiar shape with one normal looking arm and an extended arm that is less tightly wound. The galaxy is inclined by 42° to the line-of-sight with a major axis position angle of 68°. A bridge of neutral hydrogen gas links NGC 4254 with VIRGOHI21, an HI region and a possible dark galaxy. The gravity from the latter may have distorted M99 and drawn out the gas bridge, as the two galaxy-sized objects may have had a close encounter before parting greatly. However, VIRGOHI21 may instead be tidal debris from an interaction with the lenticular galaxy NGC 4262 some 280 million years ago. It is expected that the drawn out arm will relax to match the normal arm once the encounter is over. While not classified as a starburst galaxy, M99 has a star formation activity three times larger than other galaxies of similar Hubble type that may have been triggered by the encounter. M99 is likely entering the Virgo Cluster for the first time bound to the periphery of the cluster at a projected separation of 3.7°, or around one megaparsec, from the cluster center at Messier 87. The galaxy is undergoing ram-pressure stripping of much of its interstellar medium as it moves through the intracluster medium.

Supernovae and luminous red nova Four supernovae have been observed in M99:

SN 1967H (Type II, mag. 14.0) was discovered by Fritz Zwicky on 1 July 1967. SN 1972Q (type unknown, mag. 15.8) was discovered by Leonida Rosino on 14 December 1972. SN 1986I (Type II, mag. 14) was discovered by Carlton Pennypacker et al. on 17 May 1986. SN 2014L (Type Ic, mag. 17.2) was discovered by the THU-NAOC Transient Survey (TNTS) on 26 January 2014. One luminous red nova has been observed in M99:

PTF 10fqs (Type LRN, mag. 20.1) was discovered by the Palomar Transient Factory on 16 April 2010.

See also List of Messier objects Messier 83 – a similar face-on spiral galaxy Pinwheel Galaxy – a similar face-on spiral galaxy

References

External links

SEDS: Spiral Galaxy M99 UniverseToday: Dark Matter Galaxy? PPARC: New evidence for a Dark Matter Galaxy Kasliwal, Mansi M.; et al. (2011). "PTF 10fqs: A LUMINOUS RED NOVA IN THE SPIRAL GALAXY MESSIER 99". The Astrophysical Journal. 730 (2): 134. arXiv:1005.1455. Bibcode:2011ApJ...730..134K. doi:10.1088/0004-637X/730/2/134. S2CID 18454146.

Messier 99 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 Messier 99

Start with the simplest possible case. Write down what Messier 99 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 99 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 99 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 99

In research: Messier 99 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 99 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 99 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1781, Coma Berenices, Discoveries by Pierre Méchain, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 99 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.

Affiliate

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

How to study Messier 99 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 99 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 99 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 99 in simple terms?

Why does Messier 99 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 99?

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 99.