science

List of asteroid close approaches to Earth in 2021

List of asteroid close approaches to Earth in 2021 is a science 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 List of asteroid close approaches to Earth in 2021 rather than just read about it. In short: Below is the list of asteroids that have come close to Earth in 2021. Timeline of known close approaches less than one lunar distance from Earth A list of known near-Earth asteroid close approaches less than 1 lunar distance (0.0025696 AU (384,410 km; 238,860 mi)) from Earth in 2021, based on the close approach database of the Center for Near-Earth Object Studies (CNEOS).

Key takeaways

List of asteroid close approaches to Earth in 2021 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect List of asteroid close approaches to Earth in 2021 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of List of asteroid close approaches to Earth in 2021 from memory before moving on to harder problems.

Reference excerpt

Below is the list of asteroids that have come close to Earth in 2021.

Timeline of known close approaches less than one lunar distance from Earth A list of known near-Earth asteroid close approaches less than 1 lunar distance (0.0025696 AU (384,410 km; 238,860 mi)) from Earth in 2021, based on the close approach database of the Center for Near-Earth Object Studies (CNEOS). For reference, the radius of Earth is about 0.0000426 AU (6,370 km; 3,960 mi) or 0.0166 lunar distances. Geosynchronous satellites have an orbit with semi-major axis length of 0.000282 AU (42,200 km; 26,200 mi) or 0.110 lunar distances. The largest asteroid to pass within 1 LD of Earth in 2021 was 2021 SG with an estimated diameter of around 68 meters and an absolute magnitude of 24.0. The fastest asteroid to pass within 1 LD of Earth in 2021 was 2021 UA7 that passed Earth with a velocity with respect to Earth of 27.7 km/s (62,000 mph). The CNEOS database of close approaches lists some close approaches a full orbit or more before the discovery of the object, derived by orbit calculation. The list below only includes close approaches that are evidenced by observations, thus the pre-discovery close approaches would only be included if the object was found by precovery, but there was no such close approach in 2021. This list and the relevant databases do not consider impacts as close approaches, thus this list does not include any of the objects that collided with Earth's atmosphere in 2021, none of which were discovered in advance, but were observed visually or recorded by sensors designed to detect detonation of nuclear devices. Rows highlighted red indicate objects which were not discovered until after closest approach Rows highlighted yellow indicate objects discovered less than 24 hours before closest approach Rows highlighted green indicate objects discovered more than one week before closest approach Rows highlighted turquoise indicate objects discovered more than 7 weeks before closest approach Rows highlighted blue indicate objects discovered more than one year before closest approach(i.e. objects successfully cataloged on a previous orbit, rather than being detected during final approach)

Warning times by size This sub-section visualises the warning times of the close approaches listed in the table of confirmed close approaches, depending on the size of the asteroid. It shows the effectiveness of asteroid warning systems at detecting close approaches in 2021. The sizes of the charts show the relative sizes of the asteroids to scale. For comparison, the approximate size of a person is also shown. This is based the absolute magnitude of each asteroid, an approximate measure of size based on brightness. Absolute magnitude H ≥ 30 (smallest)

(size of a person for comparison)

Absolute magnitude 30 > H ≥ 29

Absolute magnitude 29 > H ≥ 28

Absolute magnitude 28 > H ≥ 27

Absolute magnitude 27 > H ≥ 26 (probable size of the Chelyabinsk meteor)

Absolute magnitude 26 > H ≥ 25

Absolute magnitude 25 > H (largest)

Predicted close approaches Below is the list of predicted close approaches of near-Earth asteroids larger than magnitude 27, that were predicted to occur in 2021. This relates to the effectiveness of asteroid cataloging systems at predicting close approaches in 2021. 2018 BA3 (with a 9 day observation arc from January 2018) could have passed as far as 3 million km (8 LD) from Earth. For asteroids which were observed but not predicted in advance, see the main list above. Rows highlighted orange indicate objects which were predicted theoretically but were not observed in practice Rows highlighted yellow indicate objects which were predicted and observed but the predicted close approach date and distance were incorrect Rows highlighted green indicate objects which were observed with the predicted close approach distance (within +/-50%) but wrong date Rows highlighted turquoise indicate objects which were observed with the predicted close approach date but wrong distance (out by over 50%) Rows highlighted blue indicate objects which were observed as predicted with the correct close approach date and distance

Notes

Additional examples

Below is an example list of near-Earth asteroids that passed or will pass more than 1 lunar distance (384,400 km or 0.00256 AU) from Earth in 2021.

Notes

See also List of asteroid close approaches to Earth List of asteroid close approaches to Earth in 2020 List of asteroid close approaches to Earth in 2022 Asteroid impact prediction

References

Illustrations

Worked examples

Example 1 — a first encounter with List of asteroid close approaches to Earth in 2021

Start with the simplest possible case. Write down what List of asteroid close approaches to Earth in 2021 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 List of asteroid close approaches to Earth in 2021 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 List of asteroid close approaches to Earth in 2021 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 List of asteroid close approaches to Earth in 2021

In research: List of asteroid close approaches to Earth in 2021 appears in science 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 List of asteroid close approaches to Earth in 2021 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: List of asteroid close approaches to Earth in 2021 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earth-crossing asteroids, Lists of asteroids, Near-Earth asteroids, so understanding it makes those chapters shorter.
In everyday life: Look for List of asteroid close approaches to Earth in 2021 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “List of asteroid close approaches to Earth in 2021” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study List of asteroid close approaches to Earth in 2021 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what List of asteroid close approaches to Earth in 2021 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 List of asteroid close approaches to Earth in 2021 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is List of asteroid close approaches to Earth in 2021 in simple terms?

Below is the list of asteroids that have come close to Earth in 2021. Timeline of known close approaches less than one lunar distance from Earth A list of known near-Earth asteroid close approaches less than 1 lunar distance (0.0025696 AU (384,410 km; 238,860 mi)) from Earth in 2021, based on the c…

Why does List of asteroid close approaches to Earth in 2021 matter?

Because it connects several science 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 List of asteroid close approaches to Earth in 2021?

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 List of asteroid close approaches to Earth in 2021.