astronomy

MACHO-1997-BLG-41

MACHO-1997-BLG-41 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 MACHO-1997-BLG-41 rather than just read about it. In short: MACHO-1997-BLG-41, commonly abbreviated as 97-BLG-41 or MACHO-97-BLG-41, was a gravitational microlensing event located in Sagittarius which occurred in July 1999. The source star is likely a giant or subgiant star of spectral type K located at a distance of around 8 kiloparsecs (26,000 light-years).

Key takeaways

MACHO-1997-BLG-41 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect MACHO-1997-BLG-41 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of MACHO-1997-BLG-41 from memory before moving on to harder problems.

Reference excerpt

MACHO-1997-BLG-41, commonly abbreviated as 97-BLG-41 or MACHO-97-BLG-41, was a gravitational microlensing event located in Sagittarius which occurred in July 1999. The source star is likely a giant or subgiant star of spectral type K located at a distance of around 8 kiloparsecs (26,000 light-years). The lens star is a binary system approximately 10,000 light-years away in the constellation Sagittarius. The two stars are separated from each other by about 0.9 AU and have an orbital period of around 1.5 years. The most likely mass of the system is about 0.3 times that of the Sun. Star A and star B are both red dwarfs. The first published model of the MACHO-1997-BLG-41 event using data from Mount Stromlo Observatory, Cerro Tololo Inter-American Observatory and Wise Observatory show the lens system as being located in the galactic bulge at a distance of 6.3 kiloparsecs (21,000 light-years), a total system mass of about 0.8 times that of the Sun and a separation of 1.8 AU (the most likely value given a random orientation of the system). The individual components were assigned masses 0.6 and 0.16 times that of the Sun, making them an orange dwarf of spectral class K and a class M red dwarf, respectively. According to this model, a planet with around 3.5 times the mass of Jupiter orbits in a circumbinary orbit around the two stars at a distance of around 7 AU (assuming random orientation of the system). Subsequently, an independent analysis with data from five different observatories revealed that the microlensing event could be interpreted as being caused by a low-mass binary system of two red dwarf stars located in the galactic disk if one considers their orbital motion, without the need to invoke a planetary mass. A further study combining both datasets confirmed this finding. The planet is thus considered disproven.

See also Hypothetical astronomical object Delta Trianguli PSR B1620−26 HD 202206

References

External links "MACHO 97-BLG-41". SIMBAD. Centre de données astronomiques de Strasbourg. Notes for 97-BLG-41 on The Extrasolar Planets Encyclopaedia Sincell, Mark (20 August 1999). "A World With Two Suns". Science. 285 (5431): 1191–1193. doi:10.1126/science.285.5431.1191a.

Worked examples

Example 1 — a first encounter with MACHO-1997-BLG-41

Start with the simplest possible case. Write down what MACHO-1997-BLG-41 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 MACHO-1997-BLG-41 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 MACHO-1997-BLG-41 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 MACHO-1997-BLG-41

In research: MACHO-1997-BLG-41 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 MACHO-1997-BLG-41 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: MACHO-1997-BLG-41 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1999, Binary stars, Gravitational lensing, so understanding it makes those chapters shorter.
In everyday life: Look for MACHO-1997-BLG-41 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 MACHO-1997-BLG-41 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what MACHO-1997-BLG-41 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 MACHO-1997-BLG-41 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is MACHO-1997-BLG-41 in simple terms?

Why does MACHO-1997-BLG-41 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 MACHO-1997-BLG-41?

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 MACHO-1997-BLG-41.