UPDATE MARCH 7, 2016. Asteroid 2013 TX68 safely passed by Earth on Monday morning. According to the Minor Planet Center, the space rock’s closest approach occurred on March 7 at 13:42 UTC (8:42 ET) at a distance of 2,542,960 miles (4,092,497 km) from Earth, just a bit closer than the nominal 3 million miles previously estimated. The space rock approached our planet a few hours earlier than expected. The previous estimate indicated asteroid 2013 TX68 was due to pass by Earth around March 7 at 7:06 pm ET (March 8 at 00:06 UTC).
The flyby distance was about 10.64 times the Earth-moon distance, and the next closest approach dates predictions may change again, as the asteroid’s orbit is better understood and more precisely defined using new observations.
Read more about the uncertainties leading up to this object’s closest sweep past Earth today … below.
In the days leading up to this pass by 2013 TX68, astronomers were highly uncertain as to the asteroid’s closest distance to us. They knew it would not strike Earth, but – prior to today’s pass – the most recent estimate indicated a nominal or most probable distance of 3,104,591 miles (4,996,355 km).
However, the space rock might have passed as closely as 19,000 miles (30,000 km) or as far as 10,722,990 miles (17,256,980 km).
Astronomers at NASA’s Jet Propulsion Laboratory said the variation in possible nearest distances for this asteroid was due to the wide range of possible trajectories for this object, which was tracked for only a short time after its discovery in 2013.
In the days leading up to its closest approach to us, Marco Micheli of the European Space Agency’s NEO Coordination Centre (NEOCC/SpaceDys) in Frascati, Italy, realized that this object – which was observed only briefly in 2013 before going into a region of the sky lit by the sun’s glare – was visible on some images a few days before it was officially detected on October 6, 2013. The new images let scientists roughly refine its trajectory, but just a bit.
Asteroid 2013 TX68 is travelling at a speed of 34,279 miles per hour (55,166 km/h).
According to the orbit predictions during the past two weeks, the asteroid may pass by our planet again on September 18, 2056. However, the next closest approach dates predictions will change again, now that it has swept past us.
Why has there been so much uncertainty about this object?
It’s the scenario that astronomers have always cautioned us about … the fact that asteroid 2013 TX68 approached Earth from the sun’s direction. In late February, the space rock was still approaching Earth from this direction, although the asteroid was actually at a greater distance from us than our star.
In other words, for most of the past few weeks, it has been in the daytime sky, where astronomers could not observe it.
The uncertainty of the exact date of closest approach, as well as the precise orbit, was due to the fact that asteroid 2013 TX68 was just observed during 10 days (including the newly found pre-discovery images). That is still a short time to define an orbit precisely.
On February 11, 2016, NASA removed asteroid 2013 TX68 from a list of space rocks with possibilities of future impact with Earth over the next 100 years.
Preliminary estimates of the size of asteroid 2013 TX68 suggest the space rock has a diameter of 30 meters (98 ft), which is about twice the size of the Chelyabinsk meteor that entered over Russian skies in February, 2013.
If a space rock of this size were to enter our atmosphere, it would produce a shock wave at least twice as intense as that of the Chelyabinsk meteor, which broke windows in six Russian cities – caused more than 1,500 people to seek medical care, mostly due to cuts from flying glass – and did other damage to thousands of buildings.
Bottom line: Astronomers now know that asteroid 2013 TX68 safely passed by Earth on Monday morning, March 7, 2016. According to the Minor Planet Center, the space rock’s closest approach occurred on at 13:42 UTC (8:42 ET) at a distance of 2,542,960 miles (4,092,497 km) from Earth.
Eddie Irizarry of the Sociedad de Astronomía del Caribe (Astronomical Society of the Caribbean) has been a NASA Solar System Ambassador since 2004. He loves public outreach and has published multiple astronomy articles for EarthSky, as well as for newspapers in Puerto Rico. He has also offered dozens of conferences related to asteroids and comets at the Arecibo Observatory.