APOD: Orbits of Potentially Hazardous... (2023 Jun 30)

[APOD Robot]

Orbits of Potentially Hazardous Asteroids

Explanation: Are asteroids dangerous? Some are, but the likelihood of a dangerous asteroid striking the Earth during any given year is low. Because some past mass extinction events have been linked to asteroid impacts, however, humanity has made it a priority to find and catalog those asteroids that may one day affect life on Earth. Pictured here are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs). These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth -- about 20 times the distance to the Moon. Although none of them will strike the Earth in the next 100 years -- not all PHAs have been discovered, and past 100 years, many orbits become hard to predict. Were an asteroid of this size to impact the Earth, it could raise dangerous tsunamis, for example. To investigate Earth-saving strategies, NASA successfully tested the Double Asteroid Redirection Test (DART) mission last year. Of course, rocks and ice bits of much smaller size strike the Earth every day, usually pose no danger, and sometimes create memorable fireball and meteor displays.

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[shaileshs]

Wow.. never imagined there's so many with their paths around Sun that close (relatively) to each other and all planets. We have decent idea about none of the PHA's (ones we have discovered/identified so far) colliding with Earth in next 100 years, I wonder, what's the probability of them hitting other planets ? Do we expect any such even soon (in next 20 years)? Because I don't think we are going to use DART to avoid those collisions.. but in turn those collisions might affect us some way (rays, gravity, changing plane of rotation, change of rotational axis, new moons for some planets... etc etc etc..) so maybe it's better NASA uses DART to avoid even those collisions ?

[Chris Peterson]

Wow.. never imagined there's so many with their paths around Sun that close (relatively) to each other and all planets. We have decent idea about none of the PHA's (ones we have discovered/identified so far) colliding with Earth in next 100 years, I wonder, what's the probability of them hitting other planets ? Do we expect any such even soon (in next 20 years)? Because I don't think we are going to use DART to avoid those collisions.. but in turn those collisions might affect us some way (rays, gravity, changing plane of rotation, change of rotational axis, new moons for some planets... etc etc etc..) so maybe it's better NASA uses DART to avoid even those collisions ?

Keep in mind that if this were to scale, those lines would be the thickness of an atom. The image makes the space look much, much more densely filled than it actually is!

UPDATE: okay, just for fun, I did a couple of calculations. The full size image, displayed on a modern screen (100 pixels/cm) should be understood to have the following scale: the asteroid tracks (assuming 100 m diameter asteroids) should be drawn with a width of 1 picometer, or about 1/100th the size of an atom. The Earth's path should be drawn with a width of 160 nm, the wavelength of near UV light. And, of course, while there's a bias for these objects to have orbits near the ecliptic plane, they still cover a wide range of inclinations, so we're not looking here at a plane, but at a thick volume of space projected onto a plane. If we shifted our view so we were not directly above the ecliptic, this would look quite different.

[VictorBorun]

Wow.. never imagined there's so many with their paths around Sun that close (relatively) to each other and all planets. We have decent idea about none of the PHA's (ones we have discovered/identified so far) colliding with Earth in next 100 years, I wonder, what's the probability of them hitting other planets ? Do we expect any such even soon (in next 20 years)? Because I don't think we are going to use DART to avoid those collisions.. but in turn those collisions might affect us some way (rays, gravity, changing plane of rotation, change of rotational axis, new moons for some planets... etc etc etc..) so maybe it's better NASA uses DART to avoid even those collisions ?

Keep in mind that if this were to scale, those lines would be the thickness of an atom. The image makes the space look much, much more densely filled than it actually is!

UPDATE: okay, just for fun, I did a couple of calculations. The full size image, displayed on a modern screen (100 pixels/cm) should be understood to have the following scale: the asteroid tracks (assuming 100 m diameter asteroids) should be drawn with a width of 1 picometer, or about 1/100th the size of an atom. The Earth's path should be drawn with a width of 160 nm, the wavelength of near UV light. And, of course, while there's a bias for these objects to have orbits near the ecliptic plane, they still cover a wide range of inclinations, so we're not looking here at a plane, but at a thick volume of space projected onto a plane. If we shifted our view so we were not directly above the ecliptic, this would look quite different.

Earth's orbit is presented in this APOD as 2 pixel wide line of a 366 pixel wide circle.
To present the things in scale we could use 1/64 pixel for Earth's diameter (.0425 light seconds) and 366 pixels for Earth's orbit diameter (1000 light seconds).
A line of 1/64 pixel width is a hairline with 1/64 of contrast against the background, still visible

[orin stepanek]

Click on a date/time to view the file as it appeared at that time.
https://commons.wikimedia.org/wiki/File ... d_Rock.jpg
with aprpox. 8 years difference] how come no change? They must be the same photo!
Maybe I'm missing something!!!

[johnnydeep]

Balanced_Rock.jpgClick on a date/time to view the file as it appeared at that time.
https://commons.wikimedia.org/wiki/File ... d_Rock.jpg
with aprpox. 8 years difference] how come no change? They must be the same photo!
Maybe I'm missing something!!!

What two photos are you talking about?