astronomy

Southern Crab Nebula

Southern Crab Nebula 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 Southern Crab Nebula rather than just read about it. In short: The Southern Crab Nebula (or WRAY 16-147 or Hen 2-104) is a nebula in the constellation Centaurus. The nebula is several thousand light years from Earth, and its central star is a symbiotic Mira variable − white dwarf pair.

Key takeaways

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

Reference excerpt

The Southern Crab Nebula (or WRAY 16-147 or Hen 2-104) is a nebula in the constellation Centaurus. The nebula is several thousand light years from Earth, and its central star is a symbiotic Mira variable − white dwarf pair.

Nomenclature It is named for its resemblance to the Crab Nebula, which is in the northern sky. The name Southern Crab was officially added to the IAU Catalog of Star Names on 13 June 2026. The designation He2-104 (or Hen 2-104) comes from Karl Gordon Henize's 1967 catalog, Observations of Southern Planetary Nebulae. The catalog includes 459 items identified as planetary nebulae (or likely as such).

History of observations The Southern Crab was noted in a 1967 catalog, and was also observed using a CCD imager with the 2.2 meter telescope at the La Sila observatory in 1989. The 1989 observation marked a major expansion of knowledge about the nebula, and it was observed using various filters. The nebula had already been observed using Earth-based telescopes, but images taken with the Hubble Space Telescope in 1999 have provided much more detail, revealing that at the center of the nebula are a pair of stars, a red giant and a white dwarf. It was imaged again by HST in 2019 with a newer instrument. In 1999, it was imaged by the Hubble Space Telescope's Wide Field and Planetary Camera 2, noted for its unique "stair-step" crop and for such astrophotos as the Pillars of Creation. The WFPC2 images were taken at an optical light wavelength of 658 nm. The nebula was imaged again by the Hubble Space Telescope in 2019, and a set of images to celebrate the anniversary of the space telescope's launch in 1990 (29 years) by the Space Shuttle. This time a newer camera the WFC3 was used to image the nebula, at wavelengths filters of about 502, 656, 658, and 673 nanometers. In 2008, an investigation of the Southern Crab with its symbiotic star was published. The study used imaging and spectroscopic data from space and Earth-surface telescopes including Hubble and VLT observatories. The ESO defines a symbiotic star system as "binaries in which a small hot star (white dwarf or main sequence star) orbits around a red giant star. These systems are often surrounded by an envelope of gas or dust; those with gas are known as S-types and those with dust as D-types."

Gallery

See also List of Hubble anniversary images

Notes

References

External links

The "Southern Crab" Nebula (He2-104) in 1989 Archived 2021-11-08 at the Wayback Machine (captures the crab like presentation)

Illustrations

Worked examples

Example 1 — a first encounter with Southern Crab Nebula

Start with the simplest possible case. Write down what Southern Crab Nebula 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 Southern Crab Nebula 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 Southern Crab Nebula 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 Southern Crab Nebula

In research: Southern Crab Nebula 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 Southern Crab Nebula 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: Southern Crab Nebula is common in secondary-school and first-year university syllabi. It links to neighbouring topics Centaurus, Emission nebulae, Planetary nebulae, so understanding it makes those chapters shorter.
In everyday life: Look for Southern Crab Nebula 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 Southern Crab Nebula in 20 minutes

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

Frequently asked questions

What is Southern Crab Nebula in simple terms?

Why does Southern Crab Nebula 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 Southern Crab Nebula?

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 Southern Crab Nebula.