# Tag Info

### 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 ...
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### 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 ...
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### Does the Earth have another moon?

Not strictly satellites/moons, but certainly companions are 2010 TK7 with a diameter of ~300 m, an Earth trojan at the L4 point, and the ~5 km 3753 Cruithne in a peculiar orbit locked to the ...
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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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### What is the ratio of "real" stars in the sky?

It's almost 100% stars. In good conditions, you can see perhaps 2000 stars. (There are about 6000 naked-eye visible stars; of these, 3000 are above the horizon at any time, and about 1000 are hidden ...
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### Does the Earth have another moon?

One kilometer, no way! That would've been known since long ago. Most asteroids of that size have already been found, all the way out to the asteroid belt beyond Mars. Earth has no second Moon. But ...
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### 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 ...
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### 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 ...
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### What’s the object between the Earth and The Sun currently showing in Google maps?

That's the Moon alright, and it's definitely real and definitely there. If you go outside and look at the Sun right now, the Moon will be almost but not quite on top of it, though it's impossible to ...
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### What mechanism causes oscillations of the solar system's orbit about the galactic plane?

The cause for the oscillations perpendicular to the galactic plane is the gravity of the non-spherical mass distribution (needed for a plane Kepler ellipse) in the Milky Way. Simplified, there is a ...
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### Do NEA (Near Earth Asteroids) have minable water ice?

No and yes. I'll address the "no" answer first. The answer is no if you truly mean "water ice". Ceres is close to the limit of where water can exist as water, as opposed to in the form of hydrated ...
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### 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 ...
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### 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 ...
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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 ...
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### Do NEA (Near Earth Asteroids) have minable water ice?

Unlikely. Plugging numbers into the Stefan–Boltzmann law gives us a temperature near 273°K (0°centigrade) for bodies near earth's orbit. The exact answer for atmospherless bodies depends on albedo. ...
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### 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, ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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.
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### 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 ...
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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 ...
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### 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 (...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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