95 votes
Accepted

Could the dinosaurs have seen the asteroid that killed them?

The answer is yes; for a few nights prior to the impact (assuming they had eyes with a similar sensitivity to our own and could look up!). It could be a bit longer than this if the body was larger ...
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  • 114k
31 votes

How early could we detect an asteroid the size of the one that caused the extinction of the dinosaurs?

It could be as little notice as a few days. There is a large variation in the amount of warning we would have before an asteroid strike similar in energy to Chicxulub. Let’s examine the case in which ...
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28 votes
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Why was there a gap in the number of asteroid detections between 1807 and 1845?

Ceres, Pallas, Juno and Vesta were all discovered between 1801 and 1807. After that, astronomers looked in vain for 38 years until the 5th, Astraea was spotted on December 8, 1845 by German amateur ...
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  • 3,226
25 votes

Where on Earth could dinosaurs feel the impact of their extinction asteroid?

The whole Earth "rippled" after the Chicxulub impact. By ripple, I specifically mean surface displacement. Current models indicate that it rippled enough that most of the dinosaurs and ...
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  • 13.7k
24 votes
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What caused this mysterious stellar occultation on July 10, 2017 from something ~100 km away from 486958 Arrokoth?

There were three attempts to measure Arrokoth by occultation, and the June 3rd attempt didn't detect anything. The July 10th attempt had a tiny blip, that appeared to be in the "wrong place"...
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  • 87.7k
20 votes
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Have we ever observed a body, such as a large asteroid, "hitting" the Sun?

Yes and here's a video of "a Giant Comet Hitting the Sun": https://www.youtube.com/watch?v=Mat4dWpszoQ The impact occurred sometime during May 10-11, 2011. The comet was not named but believed to ...
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  • 356
20 votes

Gravitational Properties of Asteroids

Of course you would need to specify who the person is - an Olympic athlete? Let us assume so and then you can scale downwards accordingly. So an Olympic high jumper can jump hard enough to raise ...
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  • 114k
20 votes
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Does anything orbit the Sun faster than Mercury?

The recently discovered asteroids 2019 LF6 and 2020 AV2, each taking 151 days to orbit the Sun, have the shortest periods currently listed in the JPL Small Body Database. Vulcanoids are difficult to ...
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  • 16.5k
18 votes

Has anyone back-calculated previous close encounters between the Apophis asteroid and Earth?

The JPL Small Body Database lists Apophis close approaches dating back 100 years before discovery. Three fairly close ones were: 1907-04-13, 0.029 au 1949-04-14, 0.028 au 1990-04-14, 0.033 au While ...
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  • 16.5k
18 votes
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What are the benefits of collecting asteroid samples in situ rather than just waiting for bits of asteroids to fall as meteorites?

This can be answered in two ways. At the Earth's orbit we do not necessarily sample (meteoroid intercepting Earth and surviving atmospheric entry to fall as a meteorite) all the taxonomic types (...
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  • 633
17 votes
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Why did the distribution of asteroids discovered in 2010 have a radial modulation?

I'm pretty sure that the radial pattern found in the data is a result of WISE's approximately 90 minute sampling cadence (dictated by the satellite's orbit), astrometric precision (about 0.2 ...
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  • 2,846
17 votes

How early could we detect an asteroid the size of the one that caused the extinction of the dinosaurs?

There are two classes of object. One is "asteroids" and the other is "comets". Asteroids orbit in fat ellipses, mostly between Mars and Jupiter, but some come closer and a few can ...
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  • 87.7k
17 votes
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Opportunities to see a near earth object via unaided eyes or binoculars?

Your best viewing opportunity will be 99942 Apophis which will pass Earth on April 13, 2029, where it will pass about 19,600 miles from Earth; look out for that. According to Wikipedia: On that date, ...
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17 votes

What if the Earth was hit by a small asteroid having close to the speed of light?

If the Earth was hit by an asteroid having diameter of about 5 km and moving with the speed close to the speed of light? What would happen? According to https://what-if.xkcd.com/20/ The momentum ...
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16 votes
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Could this estimate of the size and mass of the Chicxulub Impactor be accurate?

Well, that article was never accepted for publication in any peer-review journal apparently. That said, estimates may vary widely depending on assumptions about the composition and velocity of the ...
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  • 3,536
15 votes

Whats the probability of a hazardous impact for human life on Mars?

We actually have a very good idea of this because the Mars Reconnaissance Orbiter has been orbiting Mars for over a decade. The MRO is, basically, a spy satellite around Mars and is continually taking ...
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  • 7,380
15 votes
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What is the difference between the Yarkovsky effect and YORP effect?

The Yarkovsky effect is the thrust on a small object in space that has been heated by sunlight, created from radiant energy. The YORP effect is when the thrust produces rotation, likely due to uneven ...
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  • 2,532
15 votes
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How loud was the asteroid that killed the dinosaurs?

Some estimates which I found worth sharing: For fun, I searched for Chixculub TNT equivalent and e.g. ScienceDaily claims The energy released by the impact that ...
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  • 5,284
15 votes
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How many iridium layers do we know, besides the K-Pg one (the dinosaur killer "smoking gun")?

There are other iridium anomalies, particularly the Devonian-Carboniferous boundary (D-C boundary), about 350 Ma ago. The K-Pg boundary is only 66 Ma old. Just because there is an iridium anomaly ...
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  • 1,446
15 votes

What will happen to a metal asteroid if it impacts the Earth? Will it disintegrate or will it stay intact?

Whether an asteroid survives the fall through the atmosphere depends on its size and structural integrity. Our understanding of large impacts is limited (we haven't observed any, and this is a very ...
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  • 87.7k
15 votes

Can earth grazers skip on the atmosphere more than once?

I believe the answer is yes, when the asteroid after the initial pass through the earth's atmosphere no longer has escape velocity relative to the earth, but enters an elliptical orbit around the ...
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  • 2,661
14 votes

Why do planets tend to rotate in the same direction although they have formed from tumbling asteroids?

You are right that the tilt of the asteroids are distributed in very random way, and that the rotation of the Solar nebula is a minor contributor to that tilt, and only skews it a little. However, ...
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14 votes
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Do comets contain any significant amounts of iridium?

I also googled "iridium content of comets", and the first result was https://news.dartmouth.edu/news/2013/04/dartmouth-researchers-say-comet-killed-dinosaurs Now there is currently no consensus on ...
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  • 87.7k
14 votes

Does anything orbit the Sun faster than Mercury?

There is a problem with very high velocity dust particles orbiting the Sun at distances much closer than Mercury with masses of micrograms and below. These particles can do damage to spacecraft that ...
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  • 31.4k
14 votes
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Asteroids in polar orbits?

To have an orbit perpendicular to the ecliptic plane, it would need to have an inclination of exactly 90 degrees. Orbits with inclination less than 90 degrees are prograde, and with greater are ...
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  • 13.7k
13 votes
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Do asteroids have a gravitational field?

By definition, gravity is a result of mass. Any body with a non-zero mass (even atoms) will have a gravitational field associated with it. The higher the mass the stronger will be the field. This is ...
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13 votes

How well would the Moon protect the Earth from an Asteroid?

It would be much better for Earth if the impactor hit the moon... In this Worldbuilding answer, I used a paper on ejecta kinematics to do calculations for ejecta velocity upon impact. Without going ...
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13 votes

Comet Neowise c2020 f3 will return in ~6800 years, how can we be sure Earth will be in the right place to see it then?

The time of the orbit is not well known but the inclination can't change as much (small changes in velocity due to outgassing can significantly change the orbital period, but can't change the ...
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  • 87.7k
13 votes

Has anyone back-calculated previous close encounters between the Apophis asteroid and Earth?

If you visit https://ssd.jpl.nasa.gov/horizons.cgi and enter Apophis as the target body (full name "99942 Apophis (2004 MN4)"), you can go to the "Time Span" link and see "...
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