astronomy

Messier 90

Messier 90 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 90 rather than just read about it. In short: Messier 90 (also known as M90, NGC 4569 or as the Carabin Galaxy) is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away[a] in the constellation Virgo. It was discovered by Charles Messier in 1781.

Key takeaways

Messier 90 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 90 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 90 from memory before moving on to harder problems.

Reference excerpt

Messier 90 (also known as M90, NGC 4569 or as the Carabin Galaxy) is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away[a] in the constellation Virgo. It was discovered by Charles Messier in 1781.

Membership of the Virgo Cluster Messier 90 is a member of the Virgo Cluster, being one of its largest and brightest spiral galaxies, with an absolute magnitude of around −22 (brighter than the Andromeda Galaxy). The galaxy is found about 1.5° from the central subgroup of Messier 87. Due to the galaxy's interaction with the intracluster medium in its cluster, the galaxy has lost much of its interstellar medium. As a result of this process, which is referred to as ram-pressure stripping, the medium and star formation regions appear severely truncated compared to similar galaxies outside the Virgo Cluster and there are even H II regions outside the galactic plane, as well as long (up to 80,000-parsec—that is, 260,000-light-year) tails of ionized gas that have been stripped away.

Star formation activity As stated above, the star formation in Messier 90 appears truncated. Consequently, the galaxy's spiral arms appear to be smooth and featureless, rather than knotted like galaxies with extended star formation, which justifies why this galaxy, along with NGC 4921 in the Coma Cluster has been classified as the prototype of an anemic galaxy. Some authors go even further and consider it is a passive spiral galaxy, similar to those found on galaxy clusters with high redshift. However, its center appears to host significant nebula and star formation, where around 50,000 stars of spectral types O and B that formed around 5 to 6 million years ago are set amidst many A-type supergiants that were born in earlier starbursts, between 15 and 30 million years ago. Multiple supernovae (up to 100,000) in the nucleus have produced 'superwinds' that are blowing the galaxy's interstellar medium outward into the intracluster medium collimated in two jets, one of which is being disturbed by interaction with Virgo's intracluster medium as the galaxy moves through it.

Blueshift The spectrum of Messier 90 is blueshifted, which indicates that, net of non-aligned vectors of motion, the gap between it and our galaxy is narrowing. The spectra of most galaxies are redshifted. The blueshift was originally used to argue that Messier 90 was actually an object in the foreground of the Virgo Cluster. However, since the phenomenon was limited mostly to galaxies in the same part of the sky as the Virgo Cluster, it appeared that this inference based on the blueshift was incorrect. Instead, many blueshifts exhibit the large range in velocities of objects within the Virgo Cluster.

Distance measurements Low levels of H I gas prevents using the Tully–Fisher relation to estimate the distance to Messier 90.

Companion galaxies Messier 90 is rich in globular clusters, with around 1,000 of them. The galaxy IC 3583 was once thought to be a satellite of Messier 90; however, it is now thought they are too far away to be interacting at all.

Gallery

See also List of Messier objects Black Eye Galaxy (Messier 64), a similar spiral galaxy

Notes

^ Tschöke et al. 2001 uses a Hubble constant of 75 (km/s)/Mpc to estimate a distance of 16.8 Mpc to NGC 4569. Adjusting for the 2006 value of 70+2.4−3.2 (km/s)/Mpc we get a distance of 18.0+0.9−0.6 Mpc.

References

External links

SEDS: Spiral Galaxy M90

Messier 90 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 90

Start with the simplest possible case. Write down what Messier 90 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 90 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 90 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 90

In research: Messier 90 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 90 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 90 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arp objects, Astronomical objects discovered in 1781, Discoveries by Charles Messier, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 90 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 90 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 90 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 90 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 90 in simple terms?

Why does Messier 90 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 90?

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 90.