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35 votes

Is the science in "Don't Look Up" realistic?

Short observational arcs present difficulties in orbit determination. A couple of examples (taken from Wikipedia) : (392741) 2012 SQ31 was observed for one day, and the best-fit orbit was found to ...
James K's user avatar
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30 votes

Is the science in "Don't Look Up" realistic?

Accurate determination of collision within 1 day of discovery is realistic only if old pre-discovery measurement data is available. We can approximate the orbit determination accuracy with some ...
jpa's user avatar
  • 1,610
20 votes

Could an object enter or leave the vicinity of the Earth without being detected?

The Chelyabinsk meteor exploded over Chelyabinsk Oblast just shy of a decade ago. It was estimated after the fact to have been about 20 meters in diameter. No organization saw it before it entered the ...
David Hammen's user avatar
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17 votes
Accepted

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, ...
WarpPrime's user avatar
  • 6,673
11 votes
Accepted

Could 99942 Apophis break up due to Earth's gravity during 2029 flyby?

Unlikely. An asteroid can break up due to tidal forces if it approaches a planet closer than the Roche limit. The exact size of the Roche limit depends on the density of the object and whether it is ...
James K's user avatar
  • 123k
8 votes
Accepted

Is there a distinction between NEOs and near-Earth asteroids? Is there a difference?

Yes, Near Earth Objects (NEOs) include asteroids (Near Earth Asteroids (NEAs)) and a few percent of comets (Near Earth Comets (NECs)). As shown by the Update to Determine the Feasibility of Enhancing ...
astrosnapper's user avatar
  • 8,357
7 votes

Can Earth have a ring?

Most planets don't have rings. The ring region is inside the Roche limit which is quite close to the planet. A ring system outside the Roche limit needs to be either very faint or, it would over ...
userLTK's user avatar
  • 24.1k
6 votes

Newtons law of Gravitation

For gravity the force is : $$F=\frac {G M_1 M_2} {r^2}$$ But the acceleration : $$a=\frac F {M_2} =\frac {G M_1 } {r^2}$$ and this is the same for all bodies as it depends only on the primary's ...
StephenG - Help Ukraine's user avatar
6 votes
Accepted

Has Hubble ever been used to try to image a near Earth asteroid?

[rewritten to address the revised question] Maybe, depending on how fussy you want to be about "resolved". This is a study from 1995, using observations of asteroid 4179 Toutatis made in 1992 with ...
Peter Erwin's user avatar
  • 17.1k
5 votes
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Reference frames in relativity?

It depends on your definition of "layman" but Patrick Wallace has a slide presentation on what changed and why with the new reference systems. There is also the USNO Circular 179 which covers all of ...
astrosnapper's user avatar
  • 8,357
5 votes

Has NASA confirmed earth now has a second moon orbiting the planet?

2016 HO3 does not really orbit Earth. It orbits the Sun in such a way that it happens to loop around Earth at distances of 0.1 to 0.25 AU. Earth's gravitational sphere of influence is much smaller, ...
Mike G's user avatar
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5 votes
Accepted

Has NASA confirmed earth now has a second moon orbiting the planet?

It's not true; this object is not a moon of Earth's. Here's a NASA/JPL announcement of it. 2016 HO3 is the "name" being used for it at the moment. They're calling it a "quasi-moon". It's in an orbit ...
Andy's user avatar
  • 2,467
5 votes
Accepted

Fastest recorded apparent motion of a comet or asteroid seen from Earth (degrees/day)?

This is more of a recent example than a record. On 2019-07-25, asteroid 2019 OK passed about 65000 km from the Earth at a relative speed of 24.5 km/s. The Minor Planet Center lists multiple ...
Mike G's user avatar
  • 18.7k
5 votes
Accepted

Has a near earth object in heliocentric orbit ever been bright enough to be visible to the unaided eye?

The Near-Earth close approches website shows close approaches to the Earth by near-Earth objects (NEOs). The table showing all close encounters indicates the absolute magnitude. The data can be ...
usernumber's user avatar
  • 17.5k
5 votes
Accepted

How poor was our tally of objects that could produce potential extinction-level events back in 1998?

It was fairly poor. Wikipedia has a list of large, potentially hazardous asteroids, and 9 on that list were known before 1998: 2201 Olijato 1620 Geographos 4183 Cuno 1981 Midas 3122 Florence 3200 ...
James K's user avatar
  • 123k
5 votes
Accepted

2001 VB - when will it be reacquired?

The remote chance of an Earth impact in late July 2023 may depend on hitting a small "keyhole" near Venus on 2002-01-09. NEODyS gives an 8% chance that 2001 VB even passed within 0.1 au of ...
Mike G's user avatar
  • 18.7k
5 votes

Could an object enter or leave the vicinity of the Earth without being detected?

Each year, several small NEOs pass Earth closer than the distance of the Moon. Here is the list of NEOs that has been detected recently but still, many of them passes through undetected. The main ...
Nilay Ghosh's user avatar
  • 4,462
4 votes

What measures are currently in place to detect asteroids on possible collision courses with earth?

This site is an asteroid tracking program started up by NASA. It seems to be fairly effective at detecting asteroids. Read up on this article for further information about NASA's plan.
CipherBot's user avatar
  • 1,301
4 votes

Will 1036 Ganymed's orbit be changed by its close encounter with Mars in 2176?

Ganymed's Mars approach in 2176 is only moderately close: 4.4 times Mars's Hill sphere radius or 11 times the average Earth-Moon distance. JPL HORIZONS predicts these heliocentric orbital elements (...
Mike G's user avatar
  • 18.7k
4 votes
Accepted

How was a rock on the surface of asteroid 101955 Bennu first observed from Earth (Benben Saxum)?

I think it is the "boulder" discovered by Nolan et al. (2013). They used radar images from two ground-based observatories, from two different passes, to perform shape modeling: The radar ...
Jean-Marie Prival's user avatar
4 votes
Accepted

With only seemingly two measurements 30 minutes apart, how were astronomers able to determine that asteroid 2022 EB5's trajectory intersected Earth?

The object was already so close to the Earth that in the 30 min time difference between the observations it moved already 1/4 of the way further to the earth (from about 21 Earth radii distance to 16 ...
Thomas's user avatar
  • 3,484
4 votes

Appropriate NEO databases for preliminary orbit determination simulations

The Minor Planet Center (MPC) is the officially designated clearing house for all asteroid observations, including Near-Earth Objects (NEOs). Their database has the records of all observations for all ...
astrosnapper's user avatar
  • 8,357
3 votes
Accepted

Size and Mass of a typical "small" asteroid that impacts the Earth?

For the asteroid not to break up it needs to either be big, or tough. You can experiment with the impact effects calculator but you should notice that a rocky asteroid with a diameter of less than ...
James K's user avatar
  • 123k
3 votes
Accepted

Discovery of Near Earth Objects (NEO's)

This is because there are many more small NEOs than there are large ones and the larger ones are easier to find and so were found first. The numbers of NEOs follow what's know as a power law ...
astrosnapper's user avatar
  • 8,357
3 votes

Why is the difference between Apollo and Aten asteroids considered meaningful?

The first point to make is that categorization isn't an exact science. It's done for convenience and practicality and sometimes, familiarity. It's not going to be perfect. The second point to make ...
userLTK's user avatar
  • 24.1k
3 votes

How would a small TCO (temporarily captured orbiter) or other natural Earth satellite most likely be detected?

Cruithne and J002E3 were detected using ground based astrophotography. J002E3 is thought to be "the S-IVB third stage of the Apollo 12 Saturn V rocket ... It is thought that J002E3 left Earth orbit in ...
Wayfaring Stranger's user avatar
3 votes
Accepted

What would people on Earth see during a close comet pass?

Hear and smell: Nothing. The comet and its coma are well outside the atmosphere, no sound or scent can travel through space. The coma of the comet could be 30000km across, bigger than the moon, and ...
James K's user avatar
  • 123k
3 votes

What mechanism causes oscillations of the solar system's orbit about the galactic plane?

I posted an answer for this on Physics SE recently, but have also just had a query on this from another Astronomy SE answer, so I am adding this here for completness. You can approximate the plane of ...
ProfRob's user avatar
  • 153k
3 votes
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Retrogradation movement of planet Mars relatively from Earth by Copernic

You are right. If Mars orbited in exactly the same plane as the Earth, instead of an S or a loop, we would see Mars moving prograde relative for the stars along the ecliptic, then slowing and ...
James K's user avatar
  • 123k
3 votes

Which solar system objects have the least stable solar orbits?

The least stable orbits are likely the temporarily captured orbiters of Earth and other planets. These are bodies that have been captured by the Earth/Moon gravity well and move from solar orbits to ...
James K's user avatar
  • 123k

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