Starship Asterisk*

ta152h0 wrote:There was a mention of a camera shake by one observer of the asteroid fly by. Is it possible to measure the distance of a background star by measuring the amplitude of the shake of a nearby object and compare the amplitute of the shake on a far away object and just bdo the math ? Couldn't be that simple , could it ?

Space astrometry for parallax

In 1989, the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions of nearby stars, increasing the reach of the method tenfold. Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 light-years away, a little more than one percent of the diameter of the Milky Way Galaxy. The European Space Agency's Gaia mission, due to launch in 2013, will be able to measure parallax angles to an accuracy of 10 microarcseconds, thus mapping nearby stars (and potentially planets) up to a distance of tens of thousands of light-years from earth.

ta152h0 wrote:There was a mention of a camera shake by one observer of the asteroid fly by. Is it possible to measure the distance of a background star by measuring the amplitude of the shake of a nearby object and compare the amplitute of the shake on a far away object and just bdo the math ? Couldn't be that simple , could it ?

ta152h0 wrote:
There was a mention of a camera shake by one observer of the asteroid fly by. Is it possible to measure the distance of a background star by measuring the amplitude of the shake of a nearby object and compare the amplitute of the shake on a far away object and just bdo the math ? Couldn't be that simple , could it ?

Steve Randall wrote:Does the asteroid seem to be spinning? Maybe 2 or 3 revs/second? Did anyone do an FFT on luminosity or something?

Steve Randall wrote:
Does the asteroid seem to be spinning?
Maybe 2 or 3 revs/second?

Chris Peterson wrote:

ta152h0 wrote:
I remember the 1972 meteor that famously, and lucky for us was photographed by an amateur , streaked ove a lake. I don't remember reading about a shock wave in Scientific American at the time. Maybe it was going too slow. I do remember reading it came back for a final visit.

That was the Grand Teton meteor. It was an Earth grazer, meaning it only dipped into the upper atmosphere. It was far too high for any audible acoustic energy to reach the ground. In all likelihood it was smaller and less massive than the body that exploded over Russia. Based on its orbital elements (as modified by its 1972 encounter with the Earth) it should have returned quite close to the Earth in 1997, but it was not detected.

http://en.wikipedia.org/wiki/Grand_Teton_Meteor wrote:
<<The 1972 Great Daylight Fireball (or US19720810) was an Earth-grazing meteoroid that passed within 57 kilometres of the surface of the Earth at 20:29 UTC on August 10, 1972. It entered the Earth's atmosphere at 15 kilometres per second in daylight over Utah, United States (14:30 local time) and passed northwards leaving the atmosphere over Alberta, Canada. It was seen by many people and recorded on film and by space-borne sensors. Analysis of its appearance and trajectory showed it was a meteoroid about 3 metres in diameter, if a carbonaceous chondrite, to 14 metres, if made of cometary ices. It was in the Apollo asteroid class in an Earth-crossing orbit that would make a subsequent close approach to Earth in August 1997. In 1994, Czech astronomer Zdenek Ceplecha re-analysed the data and suggested the passage would have reduced the meteoroid's mass to about a third or half of its original mass. The meteoroid's 100-second passage through the atmosphere reduced its velocity by about 800 metres per second and the whole encounter significantly changed its orbital inclination from 15 degrees to 8 degrees. If it had not entered at such a grazing angle, this meteoroid would have lost all its velocity in the upper atmosphere, possibly ending in an airburst, and any remnant would have struck Earth at terminal velocity.>>

http://en.wikipedia.org/wiki/The_Hammer_of_God wrote:

<<The 1972 Great Daylight Fireball (or US19720810) meteoroid is described in the preface of the first chapter of Arthur C. Clarke's The Hammer of God.

The Hammer of God is a science fiction novel by Arthur C. Clarke originally published in 1993. A good portion of the book details the life of spaceship-captain Robert Singh (including his running a marathon race on the Lunar surface and uprooting his life and moving to Mars). When it is discovered that the asteroid Kali is likely to hit Earth, Singh's ship Goliath makes an emergency voyage to Kali with a load of thrusters to set up on the asteroid, hopefully nudging the rock's orbit just enough to push it clear of Earth. In the meantime, a religious sect called Chrislam, originally founded by a female veteran of the Persian Gulf War, believes that they can convert a human being into a few terabytes of computer information, and then transmit this data across space to Sirius (where they believe aliens reside); members of the sect also come to believe that the asteroid is meant to destroy the Earth. They [Geckzilla, Owlice, Moonlady, Ann and Margarita] thus sneak a bomb on board the Goliath and ruin the thrusters. While Singh uses the Goliath itself as a thruster to move the asteroid, the world government on Earth rushes to reconstruct one of the planet's long-decommissioned nuclear weapons, hoping to break the peanut-shaped Kali in two.

While filmmaker Steven Spielberg optioned the rights to The Hammer of God for film production, the resultant movie, Deep Impact (1998), was dissimilar enough to the book that Clarke received no on-screen credit for the movie.>>

ta152h0 wrote:I remember the 1972 meteor that famously, and lucky for us was photographed by an amateur , streaked ove a lake. I don't remember reading about a shock wave in Scientific American at the time. Maybe it was going too slow. I do remember reading it came back for a final visit.

cmflyer wrote:Getting both answers (see Art's answer above yours). The boom sounds like a classic double sonic-boom, and I agree with Art that the fragments seem to be making their own smaller sonic-booms. Perhaps the brightest flash corresponds with max-Q, which, assuming the velocity was down into the Mach 1 or 2 range by that time, would cause the main boom, create maximum heat, and shatter the object.

Chris Peterson wrote:

cmflyer wrote:2. Was the shockwave experienced in Russia a result of the object ramming through air hypersonically, or from it exploding, or both?

Primarily from the explosion. When the object fragmented, a huge surface area was exposed to ablation, superheating a large volume of air (a cylinder because of the motion of the bodies). This is the primary source of the shockwave. There were secondary shockwaves created by the smaller pieces, but these were much lower energy (you can hear them after the primary shock in some of the videos). At the disruption height of 27 km, most of the energy from the supersonic shock waves dissipated before reaching the ground.

neufer wrote:Detection technologies for objects less than about 100 meters make good sense:

Chris Peterson wrote:
Developing detection and deflection technology makes good sense, but probably only for objects larger than about 100 meters.

• 1) To provide better statistics on how often such events occur.
  2) To give folks in populated land regions a heads up.
  3) To assist fresh meteorite searchers in unpopulated land regions.

http://en.wikipedia.org/wiki/Almahata_Sitta#Recovered_fragments_.28Almahata_Sitta_meteorite.29 wrote:
<<2008 TC3 (Catalina Sky Survey temporary designation 8TA9D69) was a meteoroid 2 to 5 meters in diameter and weighing 80 tonnes, that entered Earth's atmosphere on October 7, 2008, at 02:46 UTC (05:46 local time). The meteoroid was notable as the first such body to be observed and tracked prior to reaching Earth. It exploded an estimated 37 kilometers above the Nubian Desert in Sudan. A search of the impact zone that began on December 2008 turned up 10.5 kilograms of meteorites in 600 fragments, which are surviving pieces of the meteoroid. The meteorites are of a rare type known as ureilites [Not to be confused with Uralites], which contain, among other minerals, nanodiamonds.>>

mjimih wrote:Wow thank goodness, because from an elevation almost three times the height of Mt Everest, it was still easily capable of busting out glass over a large area. I'd say we really need to become experts at deflecting these "startlingly powerful" pebbles asap. Friday was about as stark a reminder of just how small we are as I can think of. I mean two big rocks on the same day too! Amazing. We need to build machines now that can be readily used on very short notice.
Bill Nye on the need for deflection technology (a ten year plan)

Chris Peterson wrote:

cmflyer wrote:... but these were much lower energy (you can hear them after the primary shock in some of the videos). At the disruption height of 27 km, most of the energy from the supersonic shock waves dissipated before reaching the ground.

Steve Dutch wrote:... The smallest nukes overlap the largest chemical explosions, but we've never set off tens of thousands of tons of explosive at once. ...

Until the Trinity test that led to the development of the atomic bomb, it was the largest man-made explosion in recorded history with an equivalent force of roughly 2.9 kilotons of Trinitrotoluene (TNT). In a meeting of the Royal Society of Canada in May 1918, Dalhousie University's Professor Howard L. Bronson estimated the blast at some 2.4 million kilograms of high explosive.

Steve Dutch wrote:Bottom line is the difference between an estimate of 300 kT and 500 kT is not worth discussing. Even less do we know the exact energy of the Chesapeake Bay or Sudbury impacts. Order of magnitude is about it.

cmflyer wrote:2. Was the shockwave experienced in Russia a result of the object ramming through air hypersonically, or from it exploding, or both?

alter-ego wrote:The details of how much energy reaches the ground is complicated by power dissipation along the air column before disruption...

cmflyer wrote:
1. Is today's APOD video in real time?

cmflyer wrote:
2. Was the shockwave experienced in Russia a result of the object ramming through air hypersonically, or from it exploding, or both?

Airburst estimates for a stony asteroid with a diameter ranging from 30 to 85 meters

Diameter 	Kinetic energy 	Airburst energy    Airburst altitude 	Average frequency
------------------------------------------------------------------------------------------------------------
30 m  	  	   708 kt	   		 530 kt  		    16.1 km  		    185 years
50 m  	  	   3.3 Mt 		 	  2.9 Mt 		      8.5 km 	   	  764 years
85 m         	16.1 Mt 		  	15.6 Mt 		     0.435 km	  	  3300 years