Astronomers Calculate Orbit and Origins of Russian Fireball

by Nancy Atkinson on February 25, 2013

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Reconstructed orbits for the Chelyabinsk meteoroid. Credit: Jorge Zuluaga and Ignacio Ferrin, University of Antioquia in Medellin, Colombia

Reconstructed orbits for the Chelyabinsk meteoroid. Credit: Jorge Zuluaga and Ignacio Ferrin, University of Antioquia in Medellin, Colombia

Just a week after a huge fireball streaked across the skies of the Chelyabinsk region of Russia, astronomers published a paper that reconstructs the orbit and determines the origins of the space rock that exploded about 14-20 km (8-12.5 miles) above Earth’s surface, producing a shockwave that damaged buildings and broke windows.

Researchers Jorge Zuluaga and Ignacio Ferrin at the University of Antioquia in Medellin, Colombia used a resource not always available in meteorite falls: the numerous dashboard and security cameras that captured the huge fireball. Using the trajectories shown in videos posted on YouTube, the researchers were able to calculate the trajectory of the meteorite as it fell to Earth and use it to reconstruct the orbit in space of the meteoroid before its violent encounter with our planet.

The results are preliminary, Zuluaga told Universe Today, and they are already working on getting more precise results. “We are working hard to produce an updated and more precise reconstruction of the orbit using different pieces of evidence,” he said via email.

But through their calculations, Zuluaga and Ferrin determined the rock originated from the Apollo class of asteroids.

Using triangulation, the researchers used two videos specifically: one from a camera located in the Revolutionary Square in Chelyabinsk and one video recorded in the a nearby city of Korkino, along with the location of a hole in the ice in Lake Chebarkul, 70km west of Chelyabinsk. The hole is thought to have come from the meteorite that fell on February 15.

Zuluaga and Ferrin were inspired to use the videos by Stefen Geens, who writes the Ogle Earth blog and who pointed out that the numerous dashcam and security videos may have gathered data about the trajectory and speed of the meteorite. He used this data and Google Earth to reconstruct the path of the rock as it entered the atmosphere and showed that it matched an image of the trajectory taken by the geostationary Meteosat-9 weather satellite.

But due to variations in time and date stamps on several of the videos — some which differed by several minutes — they decided to choose two videos from different locations that seemed to be the most reliable.

From triangulation, they were able to determine height, speed and position of the meteorite as it fell to Earth.

This video is a virtual exploration of the preliminary orbit computed by Zuluaga & Ferrin

But figuring out the meteroid’s orbit around the Sun was more difficult as well as less precise. They needed six critical parameters, all which they had to estimate from the data using Monte Carlo methods to “calculate the most probable orbital parameters and their dispersion,” they wrote in their paper. Most of the parameters are related to the “brightening point” – where the meteorite becomes bright enough to cast a noticeable shadow in the videos. This helped determine the meteorite’s height, elevation and azimuth at the brightening point as well as the longitude, latitude on the Earth’s surface below and also the velocity of the rock.

“According to our estimations, the Chelyabinski meteor started to brighten up when it was between 32 and 47 km up in the atmosphere,” the team wrote. “The velocity of the body predicted by our analysis was between 13 and 19 km/s (relative to the Earth) which encloses the preferred figure of 18 km/s assumed by other researchers.”

They then used software developed by the US Naval Observatory called NOVAS, the Naval Observatory Vector Astrometry to calculate the likely orbit. They concluded that the Chelyabinsk meteorite is from the Apollo asteroids, a well-known class of rocks that cross Earth’s orbit.

According to The Technology Review blog, astronomers have seen over 240 Apollo asteroids that are larger than 1 km but believe there must be more than 2,000 others that size.

However, astronomers also estimate there might be about 80 million out there that are about same size as the one that fell over Chelyabinsk: about 15 meters (50 feet) in diameter, with a weight of 7,000 metric tons.

In their ongoing calculations, the research team has decided to make future calculations not using Lake Chebarkul as one of their triangulation points.

“We are acquainted with the skepticism that the holes in the icesheet of the lake have been produced artificially,” Zuluaga told Universe Today via email. “However I have also read some reports indicating that pieces of the meteoroid have been found in the area. So, we are working hard to produce an updated and more precise reconstruction of the orbit using different pieces of evidence.”

Many have asked why this space rock was not detected before, and Zuluaga said determining why it was missed is one of the goals of their efforts.

“Regretfully knowing the family at which the asteroid belongs is not enough,” he said. “The question can only be answered having a very precise orbit we can integrate backwards at least 50 years. Once you have an orbit, that orbit can predict the precise position of the body in the sky and then we can look for archive images and see if the asteroid was overlooked. This is our next move!”

Read the team’s paper here.

The video from Revolutionary Square in Chelyabinsk:

Video recorded in Korkino:

Read more about the Apollo class of asteroids here.

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Luke Dones February 25, 2013 at 10:11 PM

Nice article, Nancy! One quibble – Usually “family” means a group of asteroids with a common origin, such as an impact that broke up an asteroid into a bunch of fragments. By that definition, the Apollos aren’t a family.

NancyAtkinson February 25, 2013 at 11:06 PM

You’re right, Luke — I should have used “class” and I’ve edited the article as such. Thanks!

Zoutsteen from Holland February 25, 2013 at 11:09 PM

Sounds like you found a theme to talk about Luke :-)

John Giroux February 25, 2013 at 10:53 PM

Why do you keep referring to this as a “meteoroid” as if it was something LESS THAN an asteroid, when it has been estimated at 15 meters in diameter?

http://www.diffen.com/difference/Asteroid_vs_Meteoroid

http://cen.acs.org/articles/91/i8/Russian-Meteor-Chondrite.html

Ted Judah February 27, 2013 at 12:14 AM

The distinction between Asteroid and Meteoroid has never been clear to me.

delphinus100 February 27, 2013 at 10:36 PM

Same here. Is there a generally accepted point in mass and/or size whee we say; “Less than this is a meteoroid, more than this is an asteroid?”

It’ll be arbitrary, but that’s okay, as long as we all agree on it…

bugzzz February 25, 2013 at 11:54 PM

Wow, that second video is crazy. The blue-green across the horizon after. Apocalyptic!

briansheen February 26, 2013 at 9:18 AM

Hi Nancy, excellent feature, – been waiting for it! The fact that the Russian meteorite and 2012DA14 are/were Apollos it sort of strengthens the myth doing the rounds that both had a common origin. Don’t believe myself! I have always taught that a meteor burns up on entry, a meteorite lands on Earth and a meteoroid has yet to make its mind up ie is still incoming.

Gusssss February 26, 2013 at 11:29 AM

Still amazed at how people just kept driving in a straight line or didn’t break stride as this was going off above them. That person in the park in the first video doesn’t even stop to look up for several seconds after it happens. They just seem almost oblivious to it.

Lorin Ionita February 26, 2013 at 12:28 PM

Was looking at that myself. Even the people on the sidewalk are minding their own business and not even look at the sky.

Tim Amato February 26, 2013 at 8:49 PM

Those digital cameras are a lot more sensitive to light than we are. I have a camera on my house and it looks like its daylight well before sunrise.

Lorin Ionita February 27, 2013 at 10:01 AM

That I know, but I remember that a few videos had loud bangs when the asteroid blew up in the atmosphere. I think that would make you stop and look around.

Ron Davison February 26, 2013 at 12:09 PM

The conversion to English units on the altitude the meteor exploded is incorrect. It should be 8.7 – 12 miles up instead of 12-15 miles.

Aqua4U February 26, 2013 at 5:39 PM

Apollo orbit asteroids can overtake Earth’s orbit from a sun-ward direction and therefore unseen and the most dangerous? The 1st quarter, waning Moon’s dark-side faces in that direction. Getting impact counts from lunar obs. w/a high speed video cam during that time period now seems more prudent than ever?

Timothy R. Sillett February 27, 2013 at 4:28 AM

Need one of same size over Arizona, Think of all that denaro

Dav_Daddy February 28, 2013 at 6:01 AM

As long as it isn’t too close to my house I’m with you.

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