On January 1st at pm on highway in Lower Sackville, Nova Scotia, I saw what looked to be a large red ball of fire moving across the sky. Unfortunately, it was moving fast enough to be out of sight within 5 seconds. We both sat there discussing the possibilities.
So I googled asteroids in and read this. I just wanted to let you know that at least two people witnessed your asteroid. Philip, you are right on target, though technically a meteor is the display the object makes when it enters the atmosphere and is luminous from friction. My impression is if it is dicovered telescopically its an asteroid, but if it is not discovered until it lights up in the earths atmosphere its a meteor.
Here sizre does not matter!
Planetary Size and Distance Comparison
Nova Scotia is UT-4; cf. Perhaps AA had a twin traveling at some distance? Or else you might have seen another coincidental meteorite on the same date as AA; reminiscent of that which we experienced on the day of the Chelyabinsk event in Russia? I have a small problem with this report of the discovered 19th mag object being the same as the impact object.
This discovered object was moving quite a bit in each of the 11 minute exposures. I find it hard to believe the object moving left to right, across your FOV at , miles at the time of the sighting, is going to impact anywhere within 20, miles of your position. Great story, but makes me think this is more sensationalism than accurate news. I live in New Orleans and I was outside actually watching fireballs fly through the sky.
I have a few pictures of this eevent. So another sighting of this event was seen in Louisiana and my family has pictures from this in California. They were impressive and extremely fast fireballs flying about the height a plane would fly. Some comments here mentioned other sightings of fireballs. These are almost certainly unrelated. Small fireballs, bright enough to be locally spectacular the sort of thing that makes you say, "wow!
There are hundreds every day globally. And something this size can be dazzlingly bright and will cast shadows on the ground as it dumps its energy in the atmosphere. So the vast majority of these visually spectacular fireballs go unobserved.
But things are changing… Within a decade, we may reasonably expect that half of these super-fireballs will be detected with enough advance warning that we might at least be alerted a few hours in advance. Enough time to run outside and enjoy the show. Another benefit of the Information Age….. Very few of your readers will spot the "Read All Comments" button and realize that this leads to more messages.
How about showing the first 25 or even 50 comments on the top page? We need some categories below those to separate the asteroid wheat from the asteroid chaff. Obviously, this object, AA, qualifies by minimal standards as an "asteroid" because it was discovered as asteroids are normally discovered, and it was handled by the MPC.
Therefore, "asteroid". Unfortunately for public communication, this term is far too broad. While it was numbered as an asteroid, this should be referred to as a "meteor" or perhaps a "meteor detected by an asteroid survey". What are the odds? I live at I heard a loud boom in he sky late one night near new years eve. It may not have been this event but a precog impression of it.
Who knows? There are all kinds of communications going on in the universe. Get tuned. Frank, you make a very good point. Many of my non-astronomer type friends are very surprised when when I tell them there is no precise diameter to distinguish meteoroids from asteroids. It seems if the object is more than 1 meter we could call it an asteroid. I have often thought that an object with an absolute magnitude of more than 31 should be a meteoroid and less than 31 and thus brighter should be an asteroid.
The absolute magnitude of an asteroid is its magnitude if was 1 AU from the sun and 1 AU from the earth, which can be calculated since we know it apparent magnitude and its distance from earth using the inverse squar law etc. However, even this does not work for AA. So using the object absolute magnitude to tell if it is an asteroid or meteoroid will not work for object close to magnitude 31 either.
I guess we will just have to keep using the definition,if it is telescopically discovered it is an ansteroid.
Astronomy: The Study of the Universe
Does anyone have a better idea? It was very interesting to read your replies. The Minor Planet Center does not use the term "meteoroid". The relegating of the term "meteor" to being only the "visible streak of light" is a common misuse of the terms "meteoroid" and "meteor" as originally defined by the IAU. Sorry, size does matter!
A meteoroid is less than 10 meters in diameter.
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Subsequent observations of Apophis ruled out an impact in and also determined that it is quite unlikely that this object could strike during its next close approach to Earth in However, there likely remain many Apophis-sized NEOs that have yet to be detected. The threat from Apophis was discovered only in , raising concerns about whether the threat of such an object could be mitigated should a collision with Earth be determined to have a high probability of occurrence in the relatively near future.
In June , a powerful explosion blew down trees over an area spanning at least 2, square kilometers of forest near the Podkamennaya Tunguska River in Central Siberia. As no crater associated with this explosion. Elhassan, M. Shaddad, and P. However, subsequent analysis and more recent modeling see, e. Such airbursts are potentially more destructive than are ground impacts of similar-size objects.
A stony meteorite 1 to 2 meters in diameter traveling at high supersonic speeds created an impact crater in Peru in September According to current models with standard assumptions, such a small object should not have impacted the surface at such a high velocity. This case demonstrates that specific instances can vary widely from the norm and is a reminder that small NEOs can also be dangerous.
Although the object was deemed too small to pose much of a threat, the Spaceguard Survey 1 and the Minor Planet Center see Chapter 3 acted rapidly to coordinate an observation campaign over the following 19 hours, with both professionals and amateurs to observe the object and determine its trajectory. The 2- to 5-meter-diameter object entered the atmosphere on October 7, , and the consequent fireball was observed over northern Sudan Figure 2.
Subsequent ground searches in the Nubian Desert in Sudan located 3. These recent events, as well as the current understanding of impact processes and the population of small bodies across the solar system but especially in the near-Earth environment, raise significant concerns about the current state of knowledge of potentially hazardous objects and the ability to respond to the threats that they might pose to humanity.
The Spaceguard Survey was mandated by Congress to detect 90 percent of NEOs 1 kilometer in diameter or greater by The observation of NEOs that appear very close to the Sun when viewed from Earth is difficult or even impossible. The brightness of each NEO also changes as it moves through its orbit, coming closer to and going farther away from Earth.
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As a result, it is very difficult to detect all NEOs, particularly smaller fainter asteroids, in the entire population. Figure 2. Note that the asteroids represented in Figure 2. The image is also very misleading in the sense that on this scale, the asteroids would be invisible. The vast majority of the solar system is empty space, but there are nonetheless many objects present. Of course, while many NEOs have been located, there are many yet to be discovered, some of which may represent a significant threat of impact on Earth.
Using estimates of the distribution and orbits of these undiscovered NEOs, the committee can statistically address the hazard posed by NEOs, particularly those that are large enough to cause significant damage should they impact Earth. To determine what fraction of the entire NEO population has been detected, it is necessary to compute the total expected number of objects from knowledge of the properties of known NEOs and how objects are expected to get brighter and fainter as they and Earth move around their orbits.
Using computer models one can determine the fraction of all NEOs of different sizes that will be detected for a particular survey strategy. As surveys approach completion and the knowledge of the NEO population increases, refinements are possible to the computer simulations that allow greater confidence in the predicted numbers of NEOs in each size range. Current estimates Harris,. The green dots represent asteroids that do not currently approach Earth. Contrary to the impression given by this illustration, the space represented by this figure is predominantly empty.