astronomy

HE 2149−2745

HE 2149−2745 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 HE 2149−2745 rather than just read about it. In short: HE 2149−2745 is a strong gravitationally lensed quasar located in the southern constellation of Piscis Austrinus. It has a redshift of (z) 2.033 and was first discovered by astronomers in 1996.

Key takeaways

HE 2149−2745 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HE 2149−2745 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HE 2149−2745 from memory before moving on to harder problems.

Reference excerpt

HE 2149−2745 is a strong gravitationally lensed quasar located in the southern constellation of Piscis Austrinus. It has a redshift of (z) 2.033 and was first discovered by astronomers in 1996. It is also classified as a broad absorption line (BAL) quasar as it shows absorption lines in its spectrum.

Description HE 2149−2745 is classified as a double quasar. When imaged, it is separated into two components with a separation gap of 1.7 arcseconds and each having B magnitudes of 17.3 and 19.0 respectively. The components also display P Cygni type emission or absorption profiles but found indistinguishable from one another. The lens galaxy of HE 2149−2745 is classified as an elliptical galaxy according to observations by Sebastian Lopez who estimated its redshift between (z) 0.3 and (z) 0.5. A spectroscopic result by A. Eigenbrod would later confirm the galaxy's redshift as (z) 0.603 although a redshift of (z) 0.495 is suggested. The lens mass of the galaxy is estimated to be 1.5(2.4) × 1011 M☉ with an R magnitude of 20.4. It is also suggested the lens galaxy might be part of a cluster given there are several other galaxies in R-band imaging. The quasar displays time-delays. Based on results using the V-band light curve data obtained via the 1.5 meter telescope at La Silla Observatory, the time-delays are estimated as 103 ± 12 days, while dismissing later time-delay estimates of either 70–85 days or 100–110 days when observed by Eva Eulaers and Pierre Magain. Observations also found the A and B components have marginal differences of 1.635 ± 0.001 and 1.505 ± 0.003 magnitudes in both V and I-bands. Evidence points out the A component is much bluer than the B component, but the color differences doesn't vary in both components during the observation period. In addition, HE 2149−2745 displays some variations in its flux ratio showing fluctuations at 0.03 suggesting microlensing variability. The broad-line region of HE 2149−2745 is observed. When studied by astronomers, the accretion disk size is found to be measured as 8+11-5 M/M☉ light-days. An estimate of the size vs. wavelength exponent was calculated as 0.4 ± 0.3. Microlensing of its broad-line region is suggested, given evidence of absorbed doubly ionized carbon emission caused by time-variable absorption in both components. A supermassive black hole mass of 9.31 ± 0.93 M☉ has been found for the quasar.

References

External links HE 2149−2745 on SIMBAD HE 2149−2745 on HyperLeda

Illustrations

Worked examples

Example 1 — a first encounter with HE 2149−2745

Start with the simplest possible case. Write down what HE 2149−2745 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 HE 2149−2745 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 HE 2149−2745 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 HE 2149−2745

In research: HE 2149−2745 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 HE 2149−2745 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: HE 2149−2745 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1996, Gravitationally lensed quasars, Piscis Austrinus, so understanding it makes those chapters shorter.
In everyday life: Look for HE 2149−2745 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 HE 2149−2745 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HE 2149−2745 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 HE 2149−2745 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HE 2149−2745 in simple terms?

HE 2149−2745 is a strong gravitationally lensed quasar located in the southern constellation of Piscis Austrinus. It has a redshift of (z) 2.033 and was first discovered by astronomers in 1996.

Why does HE 2149−2745 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 HE 2149−2745?

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 HE 2149−2745.