Bolide over Sydney and Melbourne 10 July 2014
The above map gives a rough guess of the bright meteor or fireball or bolide that passed over eastern Australia at about 9:42 pm AEST on the evening of 10 July 2014. Diagram Nick Lomb, map courtesy of Google
On the evening of 10 July at about 9:42 pm AEST numerous people in the eastern part of Australia saw a bright moving object in the sky. There were dozens of reports on the Sydney Observatory Lights in the Sky page and we thank those people who reported their sighting. As well reports were made to emergency services, news media and of course on Twitter.
Reports ranged from the vicinities of Melbourne, Sydney,Hobart, Parkes and according to one ABC reporter, Brisbane. The most credible reports gave a direction of movement from south-west to north-east. This is consistent with the rough guess for a trajectory given on the map above.
Some of the reports indicated that the object was seen for ten seconds or more which is exceptionally long for a meteor sighting and others indicated a slower speed than they had seen in previous meteor sightings. A “tail” was reported by many people; this is a dust trail or “train” left behind by the object as it moves through the atmosphere. These trains can sometimes be seen for ten minutes or more.
The object was likely to be a piece of an asteroid or space rock hitting the Earth’s atmosphere, moving almost parallel to the Earth’s surface along the above path. It would have been 100 km or so high so that it could be seen for hundreds of kilometres. As it travelled along the intense heat of friction would have broken off bits of it and this was seen, especially from the Sydney region.
A very bright object passing through the atmosphere is called a bolide or a fireball. It is the same as a meteor but brighter as it is a larger object.
An object hitting the Earth’s atmosphere must be travelling at least at the escape velocity from Earth which is 11.2 km/sec or 40,000 km/hr. When space junk reenters the atmosphere it is moving slower so the reported slow speed of Thursday evening’s bolide could indicate that it was space junk.
It would be exciting if parts of this object did survive the journey through the atmosphere and could be found. Most likely though the smaller bits that broke off the object disintegrated while the main part fell into the ocean north of Brisbane.
Update 11:20 am 11 July 2014
As indicated above, the bright object seen last night was likely to be space junk as it appeared to be travelling slower than the minimum speed of a meteor impact. Low Earth satellites circle at around 7 km/sec while the minimum speed of a meteor is 11.2 km/sec, the Earth escape velocity. In addition, the shallow impact angle of the object last night also suggested a reentry from Earth orbit.
It is now clear that the object was the third-stage rocket that helped to take Russia’s second Meteor-M weather satellite into orbit on 8 July 2014. This was a massive metal object as can be seen here so that it is not surprising that it was so bright in the Victorian/New South Wales night sky as it burned up.
The report that the rocket was seen over Brisbane is now most unlikely. There is another report that a sonic boom was heard near Cobar about 600 km to the west of Sydney suggesting that the rocket disintegrated in that vicinity. That maybe correct, but it may not as Cobar maybe a little too far from Sydney where the object was clearly seen. If metal debris from the rocket is found in the vicinity of Cobar that would be proof of the location of the rocket’s break up.
There is a project based in Western Australia to try to find fallen meteorites, called the Desert Fireball Network. They are keen to pin down the track of the Russian rocket and possibly locate any remnants. They have an app called Fireballs in the sky for download in both the App Store and Google Play and ask people to log their observations if they’re close to where they saw the fireball and can remember in which direction they were facing. Just change the time to ~9.43pm Thursday when they’re asked to edit a sighting at the end of the process.