# Sky-checking for incoming comets, asteroids etc. **URL:** \ **Category:** Factual Questions\ **Created:** [August 31, 2016, 5:46am UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547 "2016-08-31T05:46:45Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Nippless](https://avatars.discourse-cdn.com/v4/letter/n/df788c/32.png) [@Nippless](https://boards.straightdope.com/u/Nippless)\ **Post date:** [August 31, 2016, 5:46am UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547/1 "2016-08-31T05:46:45Z")
How is humanity currently monitoring the skies for potential bolide impacts? Is there any kind of official system or is it more or less left to chance observation? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [August 31, 2016, 6:15am UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547/2 "2016-08-31T06:15:41Z")
There are many official programs all over the world. In the US, NASA does the bulk of the official tracking. They receive funding from Congress specifically for this task. It’s not an easy task, though. NASA is currently tracking tens of thousands of objects, but it’s possible for them to miss an object. The meteor that came down in Russia a few years ago (and has videos all over youtube) wasn’t detected before it hit. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [August 31, 2016, 6:29am UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547/3 "2016-08-31T06:29:19Z")
And, as any Sci-Fi fan will gladly tell you, in honour of Arthur C Clarke’s novel Rendezvous with Rama, where the name was coined, such programmes may get called Spaceguard, and are often lumped under that name generically. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [August 31, 2016, 6:37am UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547/4 "2016-08-31T06:37:47Z")
If you haven’t seen this already, it’s pretty interesting (IMHO). Note the huge uptick in objects detected in the late 90s, which corresponds to when a lot of the detection programs received their first major funding. Improved technology helped with the uptick as well. Asteroid Discovery from 1980 - 2011 [![](https://img.youtube.com/vi/ONUSP23cmAE/maxresdefault.jpg "Asteroid Discovery from 1980 - 2011 (4K HD version)") ](https://www.youtube.com/watch?v=ONUSP23cmAE) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 31, 2016, 12:41pm UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547/5 "2016-08-31T12:41:43Z")
There have also been very large objects (large enough to cause extinctions, IIRC) that have passed very close (closer than the Moon), and yet only been detected _after_ their closest approach. ---
**Author:** ![joema](https://avatars.discourse-cdn.com/v4/letter/j/a9adbd/32.png) [@joema](https://boards.straightdope.com/u/joema)\ **Post date:** [August 31, 2016, 7:20pm UTC](https://boards.straightdope.com/t/sky-checking-for-incoming-comets-asteroids-etc/764547/6 "2016-08-31T19:20:04Z")
> [@Nippless](#): > > How is humanity currently monitoring the skies for potential bolide impacts? Is there any kind of official system or is it more or less left to chance observation? There is a system called Spaceguard which is much better than 10 years ago, but it is still limited: > **[Spaceguard](https://en.wikipedia.org/wiki/Spaceguard)** > > The term Spaceguard loosely refers to a number of efforts to discover, catalogue, and study near-Earth objects (NEO), especially those that may impact Earth (potentially hazardous objects). > Asteroids are discovered by telescopes which repeatedly survey large areas of sky. Efforts which concentrate on discovering NEOs are considered part of the "Spaceguard Survey," regardless of which organization they are affiliated with. > A number of organizations have also raised related discussions and propos... About 14,723 Near Earth Objects (NEOs) have been discovered, and 1,717 are classified as Potentially Hazardous Objects. > **[Near-Earth object](https://en.wikipedia.org/wiki/Near-Earth_object)** > > 34,000+ known NEOs, divided into several orbital subgroups > A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit around the Sun, rather than its current position, thus an object with such an orbit is considered an NEO even at times when it is far from making a close approach of Earth. If an NEO's orbit crosses th... > **[Potentially hazardous object](https://en.wikipedia.org/wiki/Potentially_hazardous_object)** > > A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. They are conventionally defined as having a minimum orbit intersection distance with Earth of less than 0.05 astronomical units (19.5 lunar distances) and an absolute magnitude of 22 or brighter, the latter of which roughly corresponds to a size larger than 1 Mo... As of 2011 over 93% of NEOs larger than 1 km have been found. However even a much smaller object is potentially very damaging. The 2013 meteor in Chelyabinsk Russia was probably only 20 meters in diameter. It was not detected and probably could not have been using current earth-based technology: > **[Chelyabinsk meteor](https://en.wikipedia.org/wiki/Chelyabinsk_meteor)** > > The Chelyabinsk meteor (Russian: Челябинский метеорит, Chelyabinskiy meteorit) was a superbolide that entered Earth's atmosphere over the southern Ural region in Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC). It was caused by an approximately 18 m (59 ft) diameter, 9,100-tonne (10,000-short-ton) near-Earth asteroid that entered the atmosphere at a shallow 18.3 ± 0.4 degree angle with a speed relative to Earth of 19.16 ± 0.15 kilometres per second (69,000 km/h; 42,690 mph). The lig... [https://blogs.nasa.gov/Watch\_the\_Skies/2013/02/19/post\_1361308690869/](https://blogs.nasa.gov/Watch_the_Skies/2013/02/19/post_1361308690869/) The Chelyabinsk meteor was probably the largest NEO to enter earth’s atmosphere since the 1908 Tunguska event: [Tunguska event - Wikipedia](https://en.wikipedia.org/wiki/Tunguska_event) However in 1972 a fairly large meteor formed a fireball above the Grand Tetons in the US, and it was filmed. The size is uncertain and has been estimated from 3 to 14 meters in diameter: [1972 Great Daylight Fireball - Wikipedia](https://en.wikipedia.org/wiki/1972_Great_Daylight_Fireball) Still image: [http://apod.nasa.gov/apod/image/0903/earthgrazer\_ansmet\_big.jpg](http://apod.nasa.gov/apod/image/0903/earthgrazer_ansmet_big.jpg) Film: [https://www.youtube.com/watch?v=4WlCfuPrszU](https://www.youtube.com/watch?v=4WlCfuPrszU)