astronomy

Kojima-1Lb

Kojima-1Lb 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 Kojima-1Lb rather than just read about it. In short: Kojima-1Lb (TCP J050742+244755 b) is an exoplanet discovered through the microlensing method. The host star lens was discovered by the amateur astronomer Tadashi Kojima (小嶋正).

Key takeaways

Kojima-1Lb belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Kojima-1Lb to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kojima-1Lb from memory before moving on to harder problems.

Reference excerpt

Kojima-1Lb (TCP J050742+244755 b) is an exoplanet discovered through the microlensing method. The host star lens was discovered by the amateur astronomer Tadashi Kojima (小嶋正). At the time of its discovery it was the planet around the brightest microlensing host star and consequently around a nearby star, as opposed to most of the microlensing planets, which are usually found around distant and inaccessible host stars. Kojima-1Lb is a mildly cold Neptune around a red dwarf located 429±21 pc from the Solar System.

Naming The microlensing event was first reported on CBAT as TCP J05074264+2447555 by Kojima. Conventionally microlensing planets are named after the discoverer of the microlensing event and not after the discoverer of the planetary feature. The discovery group of the planetary feature nicknamed the microlensing event Feynman-01 in honour of the Osservatorio Astroficico R.P. Feynman that discovered the planetary feature. The star now appears as Kojima-1 in SIMBAD.

Discovery The microlensing event caused by the star Kojima-1L moving in front of a background star was first observed by Tadashi Kojima from Gunma prefecture in Japan with a Canon EOS 6D + 135 mm f3.2 lens on 2 and 25 October 2017. ASASSN confirmed it as a microlensing event, but described it as a single-lens event. Nucita et al. 2017 used the photometry by AAVSO and the R.P. Feynman Observatory to first establish that TCP J05074264+2447555 was a binary lens with a hint to a new planetary system. Nucita et al. 2018 finally announced the discovery of the planet.

Lensed background star The lensed background star is a single late F-type main-sequence star with a temperature of about 6,400 K and a radius of 1.49±0.25 R☉. The lensed background star is about 800 parsecs distant from earth.

Lensing system

The star

The star has a mass of about 0.5 M☉ and it has a proper motion of 25.55±0.36 mas/yr. It is the second-brightest microlensing host star with Ks=13.7 mag. The brightest microlensing host star is Gaia22dkvL with V≈14 as of September 2023. Together with Gaia22dkvL, Kojima-1L is located outside the bulge of the Milky Way, representing a small growing sample of microlensing planets discovered in less-crowded regions.

The planet The planet has a mass of about 20 Earth masses and has a projected separation of 0.8 or 0.9 astronomical units from its host star. This translates into a semi-major axis of about 1.1 astronomical units, which was inside and near the ice line at the younger age of the system. The planet might have first formed while the snow line was at a distance larger than the orbit of the planet. As the snow line decreased, it might have crossed the orbit of the planet at around 2.2 Myrs after the Kojima-1L system has formed. Circumstellar disks around low-mass stars have lifetime of a few tens of Myrs. During planet formation, the planet might have experienced a period of a gas-rich, but ice-poor environment, before it got more ice-rich in a following period. It is difficult to form planets as massive such as Kojima-1Lb if the ice-rich period was during a gas-poor period. It is more likely that some gas remained in the ice-rich period. This way Kojima-1Lb could have grown fast during the ice-rich period, by accreting solid material and then accreting the remaining gas.

Future observations In the future it might be possible to observe the star causing the lens. With current adaptive optics instruments it is predicted that the background star and the star causing the lens can be resolved in 2021. This will enable an independent characterization of the host star by taking a spectrum. VLT/Espresso might even be able to detect the 1.3-year orbital period planet Kojima-1Lb with the radial velocity method. A follow-up with for example Subaru/IRD might even be able to detect additional inner and/or massive planets around Kojima-1L

References

External links Discovery image by T. Kojima Article about Kojima-1Lb by Sky & Telescope Osservatorio Astrofisico R.P.Feynman

Worked examples

Example 1 — a first encounter with Kojima-1Lb

Start with the simplest possible case. Write down what Kojima-1Lb 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 Kojima-1Lb 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 Kojima-1Lb 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 Kojima-1Lb

In research: Kojima-1Lb 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 Kojima-1Lb 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: Kojima-1Lb is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets detected by microlensing, Exoplanets discovered in 2018, Giant planets, so understanding it makes those chapters shorter.
In everyday life: Look for Kojima-1Lb 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 Kojima-1Lb in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kojima-1Lb 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 Kojima-1Lb out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kojima-1Lb in simple terms?

Kojima-1Lb (TCP J050742+244755 b) is an exoplanet discovered through the microlensing method. The host star lens was discovered by the amateur astronomer Tadashi Kojima (小嶋正).

Why does Kojima-1Lb 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 Kojima-1Lb?

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 Kojima-1Lb.