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If it isn't in the removed list or the table, this means its harmless. If it is a real Near Earth Object, you can click the "page at ESA" link to find out more. Normally it will say "not in risk list".
The press often runs stories about "Potentially Hazardous Asteroids" - this is a technical term for an asteroid larger than 150 meters (500 feet) across that comes within a certain distance of Earth's orbit (closer than 7.48 million kilometers (4.65 million miles) to Earth's orbit). Most come nowhere near Earth for centuries, but may have a small chance of an impact some time in the next few tens of millions of years. See What is a potentially hazardous asteroid or comet? (below)
For the details summary for the objects, I've added a paragraph about tsunamis, based on Near and far-field hazards of asteroid impacts in oceans" March 2019 in Acta Astronautica. and for summary of relevant parts, More details about the splosh, and Asteroid Generated Tsunami: Summary of NASA/NOAA Workshop. The modeling is tricky with few complete examples worked out yet, this is just a rough idea. The links for the effects for the asteroid impacts take you to the Imperial College London / Purdue University Impact Effects calculator.
The section on global effects is based on an article by Michael Paine which is from 2004, but I can't find much more recent that gives a suitable summary.
The estimated time before the next impact of this size on average is based on table 2.1, page 26, of the 2018 Report of the Near-Earth Object Science Defnition Team).
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Max number of objects to show:
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Far future objects
Dates for harmless objects
Clickable name for more info for harmless objects
Hide objects with first possible impact after
Hide objects smaller than
meters
NOTE: diameters shown in the sentry table are an estimate based on the average brightness when lit up by sunlight (albedo) of asteroids.
Palermo values (how it compares with the background rate)
Sort by maximum palermo value for single impact
(when uneslected,, sorts by combined palermo value for all its possible impacts through to 2100)
List asteroids removed in each past year - and asteroids still in table for future years
(for past years it shows the number of asteroids removed in each year, for future years, the number of asteroids with possible impacts in each year)
OK Cancel message for the randomized warnings
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It is using the same data as the more geeky NASA Sentry table which this page accesses using their published Sentry API.
I just present it in a way that is more friendly for less geeky readers. For instance, instead of just giving a "0" for the Torino value, I say in words what it means, "No hazard" and added "- HARMLESS" just to help make it really clear and be easy to see on the page. For the ones with no Torino value, instead of leaving it blank I label them as FAR FUTURE. For the Palermo value I translate it into a number that shows how less likely it is than the background rate.
This is what the geeky Sentry table says if you know how to read it.
I do this to help the many not very techy people who find the official version scary because they read the sensationalist press stories about "NASA Asteroid warnings" and don't see anything to contradict them because it is just a mass of numbers for them.
I've also added details of how many dice you’d need to throw and get them all as sixes to be equivalent to this happening. I find this works well when explaining the table to non techy scared people.
I've also taken the opportunity to do a unified search for the Search for object that shows you whether an object is in the table, or removed, and if it is neither of those, provides a link you can use to look for its JPL Small-Body database page as well as the list of observations in the IAU Minor Planet center. That's to help for the fake asteroid warnings such as for instance the Daily Express warning that Vesta was "approaching Earth"! I've also added extra links e.g. to show the size of crater, fireball, air burst etc on Bing Maps via the Imperial College London / Purdue University interactive project.
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| No Hazard (White Zone) |
0 | The likelihood of a collision is zero, or is so low as to be effectively zero. Also applies to small objects such as meteors and bodies that burn up in the atmosphere as well as infrequent meteorite falls that rarely cause damage. |
| Normal (Green Zone) |
1 | A routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or public concern. New telescopic observations very likely will lead to re-assignment to Level 0. |
| Meriting Attention by Astronomers (Yellow Zone) |
2 | A discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. While meriting attention by astronomers, there is no cause for public attention or public concern as an actual collision is very unlikely. New telescopic observations very likely will lead to re-assignment to Level 0. |
| 3 | A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of localized destruction. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away. | |
| 4 | A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of regional devastation. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away. | |
| Threatening (Orange Zone) |
5 | A close encounter posing a serious, but still uncertain threat of regional devastation. Critical attention by astronomers is needed to determine conclusively whether or not a collision will occur. If the encounter is less than a decade away, governmental contingency planning may be warranted. |
| 6 | A close encounter by a large object posing a serious but still uncertain threat of a global catastrophe. Critical attention by astronomers is needed to determine conclusively whether or not a collision will occur. If the encounter is less than three decades away, governmental contingency planning may be warranted. | |
| 7 | A very close encounter by a large object, which if occurring this century, poses an unprecedented but still uncertain threat of a global catastrophe. For such a threat in this century, international contingency planning is warranted, especially to determine urgently and conclusively whether or not a collision will occur. | |
| Certain Collisions (Red Zone) |
8 | A collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if close offshore. Such events occur on average between once per 50 years and once per several 1000 years. |
| 9 | A collision is certain, capable of causing unprecedented regional devastation for a land impact or the threat of a major tsunami for an ocean impact. Such events occur on average between once per 10,000 years and once per 100,000 years. | |
| 10 | A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean. Such events occur on average once per 100,000 years, or less often. |
For the CNEOS page about it, see:
For the philosophy behind the wording used here:
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Number of objects per row
Clickable name
Add e m o j n
(adds extra links below each object, for page on ESA, Minor planets center observations, orbit at JPL, JPL page and NEOdys-2 page)
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(skip to What is a potentially hazardous asteroid or comet or Why small asteroid tsunamis don't travel far)
If the Egyptians had build an asteroid detection telescope back at the time of the Great Pyramid of Giza, over 4,500 years ago - it would still be waiting for its first "city killer" asteroid.
Combines photo of Kheops-Pyramid with one of the two Keck ten meter telescopes Linked Hawaiian Telescopes Catch a Nova Surprise (I know the top of a pyramid in Egypt is hardly the best place for a telescope, this is just for visual effect to show the idea). They were only a few key insights away from the industrial revolution in some ways. It's a not impossible alternative history :).
See also
skip to Why small asteroid tsunamis don't travel far - Did you know
This is a technical term. It just means an asteroid larger than 150 meters in diameter that comes within a certain distance of Earth's orbit (0.05 au which is 7.48 million kilometers, or 4.65 million miles). For a comet then it also has to have a period of at most 200 years. Coming close to Earth's orbit doesn't mean they ever come close to Earth. For instance, 2010 TK7 at 150 to 500 meters in diameter is an Earth trojan which is always a third of an orbit ahead of Earth in its orbit,
Most PHA;s come nowhere near Earth for centuries, but may have a small chance of an impact some time in the next few tens of millions of years. Only a few percent will ever hit Earth - most eventually after many flybys of varous planets hit the Sun, Jupiter, or are ejected from the solar system and a few percent hit other smaller planets.
Meanwhile a NEO just means an object whose perihelion (closest point to the sun) is less than 1.3 au, i.e. 1.3 times Earth's orbital radius. Most are not even PHA's.
According to one estimate, the largest undiscovered NEO is likely to be about 3.5 km.
From Table 2-1. NEO population, impact frequency, and projected completion from Update to determine the feasibility of enhancing the search and characterization of NEOs There the numbers less than 1 are interpreted as a probability so for instance the 0.02 for objects from 7.94 to 10.0 km in diameter means there is only a 2% chance of finding even one more object of that size. Most of these will not be PHA's.
The largest known PHA is Swift-Tuttle at 26 km across, which has a one in a million chance of impact in 4479. That's plenty of time to deflect it with whatever technology we have thousands of years from now. The table is complete from 10 km upwards (the size of asteroid that ended the dinosaur era). There are only four asteroids and four comets at this size.
The only other NEO of 10 km across or larger that seems to have a chance of hitting Earth is the asteroid 433 Eros (16.84 km). It could hit us some time after a million years from now, with a 5% chance, but is not likely to hit us before 100,000 years from now. Summary details of all eight objects here.
The Sentry table is automated. New objects go their automatically as soon as they are identified as a NEO. The name consists of the year it was first observed, e.g. 2007 then a code of two letters and a number. The first letter gives the half month in which it was found, e.g. A is Jan 1-15, B is Jan 16 - 31 and so on. So F is Mar 16 - 31. Then the last bit, say, T3 in 2007 FT3, is assigned in a cycling system, first asteroid in that half month gets letter A, through to 25th gets letter Z (omitting the letter I), then it goes through A1 to Z1, and so on.
When they get the first observations, oten they don't know if it is an asteorid or not (might just be a data glitch). If so, it goes into the Scout table where it gets a temporary name. As soon as it is confirmed to be a NEO it is then transferred to the Sentry table if there is any risk, or just to the JPL and ESA tables. When an object is first discovered then the orbit is not well known, and there are many possible virtual orbits. Only one of them is the real orbit but which it is isn't known at this stage. The impacts in the risk list are for virtual orbits. When an object is removed from the table it's usually because the orbit is better known and the virtual orbits that would impact can be ruled out.
The smaller asteroids can change orbit over years to decades due to minute effects such as absorbing sunlight and re-radiating it as heat in a different direction as it spins. Comets can change orbit slightly due to outgassing and jets. But normally the reason an object gets removed is just because its orbit is better known.
This video explains how that works:
back to What is a potentially hazardous asteroid or comet - Did you know
The reason that tsunamis from earthquakes travel so far is because a large area of the floor of the ocean moves up or down suddenly. An earthquake can shift an area a hundred kilometers across or more. The resulting tsunami typically has a wavlength of 100 km or more, and that's how they travel so far inland, as this vast wave surges in towards a coast. The wavelength is also typically more than twenty times the depth of the sea, which lets them travel far without dissipating.
This gives the wave far more energy than a small asteroid can deliver. The short wavelength waves from a smaller asteroid splosh are only hundreds of meters or kilometers in diameter. These dissipate quickly, can't travel far across the sea, easily break up if they approach shallower water, and can’t travel far inland because the trough is only a short way behind the crest.
Uses A340-313X wih contrails for little image of jet at lower right, and computer simulation of an asteroid splosh from: Never Fear, an Oceanic Asteroid Impact Wouldn’t Cause Apocalyptic Tidal Waves. Future news story made with Break Your Own News
For all except the larger asteroid impacts, any waves dissipate rapidly. You get a big splosh that can shoot up to several kilometers into the atmosphere, but almost no waves. The crater that forms in the sea rapidly fills back inwards on itself, and any waves that ripple outwards don't travel far.
The transient crater in the water depends on the angle and speed, but as a very rough guide you are talking about a crater of a few kilometers wide for an impactor of up to 500 meters in width, and the depth depending on the angle. However a stony asteroid of 200 meters diameter or less would break up in the atmosphere and have almost no effect because the airburst energy is largely reflected by the sea. So for small asteroids, any tsunami risk is only for iron asteroids.
If the wavelength is less than a tenth of the ocean depth there is very rapid dissipation (inversely proportional to distance traveled). If the wavelength is more than 20 times the ocean depth then there is almost no dissipation. Earthquake tsunamis are typically 100 km or more, and so fall into this category of ones with almost no dissipation.
So you have those three things for a small splosh iron meteorite, the waves because they are much shorter in wavelength than the depth of the sea, disperse a fair bit before they get to the shore. Then whatever is left because it is short wavelength is likely to break as it bunches up, and whatever is left after that because it is short wavelength doesn't travel far up onto the land before it is caught up by the trough following behind and stops.
So there isn't much risk of tsunami in most cases, but that small splosh would be spectacular to watch from the air at a safe distance. In a simulation of a 85 meter impact of an iron meteorite, the splash curtain mainly fell back into the transient crater, but the central rebound jet rose several kilometers into the atmosphere and the first rebound wave was 200 meters high before breaking..About 1% of the impact energy was turned into a one meter high tsunami but with short wavelengths, which when it came on shore would be not much different from a storm surge.
See "Near and far-field hazards of asteroid impacts in oceans" March 2019 in Acta Astronautica
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If you are scared: Seven tips for dealing with doomsday fears which also talks about health professionals and how they can help.
If in the middle of a panic attack, see
Facebook group Doomsday Debunked has been set up to help anyone who is scared by these fake doomsdays.
If you are suicidal don’t forget there’s always help a phone call away with the List of suicide crisis lines - Wikipedia
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