astronomy

Tololo 1247−232

Tololo 1247−232 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 Tololo 1247−232 rather than just read about it. In short: Tololo 1247−232 (Tol 1247 or T1247) is a small galaxy at a distance of 652 million light-years (200 million parsecs) (redshift z=0.0480). It is situated in the southern equatorial constellation of Hydra.

Key takeaways

Tololo 1247−232 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tololo 1247−232 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tololo 1247−232 from memory before moving on to harder problems.

Reference excerpt

Tololo 1247−232 (Tol 1247 or T1247) is a small galaxy at a distance of 652 million light-years (200 million parsecs) (redshift z=0.0480). It is situated in the southern equatorial constellation of Hydra. Visually, Tol 1247 appears to be an irregular or possibly a barred spiral galaxy. Tol 1247 is named after the surveys that were carried at the Cerro Tololo Inter-American Observatory (CTIO), the first of which was in 1976. It is one of nine galaxies in the local universe known to emit Lyman continuum photons.

Background

Tol 1247−232 (T1247) was first described in 1985. It was observed in the infrared using the Cerro Tololo Inter-American Observatory (CTIO) 4m telescope, as part of a study of regions of intense star formation. Six years later, T1247 was identified as an HII galaxy in the paper 'A spectrophotometric catalogue of HII galaxies', a study of 425 emission-line galaxies. T1247 has also been classified as a starburst galaxy, a blue compact dwarf and a Wolf–Rayet galaxy.

Lyman continuum leakage T1247 is one of nine galaxies in the local universe that have been identified as leaking Lyman continuum (LyC) photons. The first published detection of Lyman continuum photons from T1247 was made in 2013 by Leitet et al. using data from the Far Ultraviolet Spectroscopic Explorer (FUSE). It was the second-known LyC-leaking source in the local universe.

LyC leakage is crucial to the process known as reionization which is believed to have occurred within the first 10% of the age of the universe. The cosmic reionization is, after recombination, the second major phase-change of hydrogen in the universe. The epoch of reionization began when the first sources appeared which produced photons capable of ionizing the surrounding medium, and ended when all of the intergalactic medium (IGM) was ionized. LyC photons are responsible for this process. However, to date it is unclear which physical mechanisms effectively produce large amounts of LyC photons, such that the reionization of the universe could be powered. Two processes are currently discussed and under evaluation: active galactic nuclei (AGN) and starbursts in dwarf galaxies. AGNs are known to produce large amounts of LyC emission, but in the early universe the number of AGNs is unknown, and often believed to be too small to power the reionization. On the other side, dwarf starbursts are known to be numerous in the early universe, but their LyC emission is unknown. For that reason local galaxies such as TOL1247 are studied in detail, in order to understand physical processes that produce escaping LyC photons. In TOL1247 it was found that bulk of the LyC photons emerges from two massive stellar clusters located in the central region of the galaxy. The escape is supported by the structure of the interstellar medium of the galaxy, which appears to be clumpy and highly ionized. Although Puschnig et al. (2017) could verify that LyC indeed escapes from TOL1247, their new spectroscopic data obtained with the Cosmic Origins Spectrograph of the Hubble Space Telescope indicates a relatively low number of escaping LyC photons (only 1.5% escape fraction). Thus, if galaxies in the early universe were similar to TOL1247, they would indeed contribute to reionization, but not sufficiently to explain the second major phase-change in the universe.

See also Pea galaxy Haro 11 Lyman-alpha forest Lyman series Precision Array for Probing the Epoch of Reionization

References

External links

Simulation of the Reionization of the Universe - A video showing the gradual reionization of a typical patch of the universe (links to YouTube).

Illustrations

Worked examples

Example 1 — a first encounter with Tololo 1247−232

Start with the simplest possible case. Write down what Tololo 1247−232 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 Tololo 1247−232 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 Tololo 1247−232 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 Tololo 1247−232

In research: Tololo 1247−232 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 Tololo 1247−232 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: Tololo 1247−232 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hydra (constellation), Principal Galaxies Catalogue objects, Starburst galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for Tololo 1247−232 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 Tololo 1247−232 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tololo 1247−232 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 Tololo 1247−232 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tololo 1247−232 in simple terms?

Why does Tololo 1247−232 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 Tololo 1247−232?

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 Tololo 1247−232.