Showing posts with label Fireballs. Show all posts
Showing posts with label Fireballs. Show all posts

Monday, 18 August 2025

Fireball over Arkansas and Missouri.

Witnesses across Arkansas, Iowa, Illinois, Indiana, Kentucky, Louisiana, Mississippi, Missouri, Oklahoman Tennessee, and Texas have reported observing a bright fireball meteor slightly after 1.30 am local time (slightly after 6.30 am GMT) on Sunday 17 August 2025. The fireball is described as having moved from southeast to northwest, appearing to the northwest of Walnut Ridge and disappearing close to Reeds Spring. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 17 August 2025 fireball meteor seen from Waxahachie, Texas. Garrett Griffen/American Meteor Society

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as a luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

See also...

Wednesday, 4 June 2025

The Nqweba Bolide and Meteorite Fall Event.

It is thought that more than a hundred tons of cosmic debris enters the Earth's atmosphere every day, mostly in the form of micrometeorites, dust-to-gravel sized particles. Most particles entering the upper atmosphere are derived from the tails of comets, but others are remnants of the original protoplanetary disc from which the Solar System formed, or fragments from the surface of other planets or moons, knocked free by earlier impacts. When these objects enter the atmosphere, they generally do so at very high velocities, causing them to heat rapidly as they pass through the atmosphere, and causing their surfaces to melt and the surrounding gasses to ionise. This can result in a bright streak across the sky called a meteor.

Larger bodies penetrate further into the atmosphere, burning longer and brighter, with those a few tens of centimetres in diameter producing meteors brighter in the sky than the planet Venus, which are termed 'fireballs'. Particularly large fireballs can sometimes be seen to visibly disinitegrate, and are known as bolides. The break up of such bolides is often audible from the ground, although, since they are typically tens of kilometres high, the sound typically reaches observers some time after the visible meteor, which can be confusing.

In a paper published in the South African Journal of Science on 29 May 2025, Roger Gibson of the School of Geosciences at the University of the Witwatersrand, Timothy Cooper of the Comet Asteroid and Meteor Section of the Astronomical Society of Southern AfricaLeonidas Vonopartis, also of the School of Geosciences at the University of the Witwatersrand, Carla Dodd of the Department of Geosciences and Institute for Coastal and Marine Research at Nelson Mandela University, Peter Hers of the Garden Route Centre of the Astronomical Society of Southern Africa, and Lewis Ashwal and Robyn Symons, once again of the School of Geosciences at the University of the Witwatersrand, describe a bolide event which took place over the coastal belt between Mossel Bay and Gqeberha, and as far north as the southern Karoo, on 25 August 2024.

Slightly before 9.00 am on Sunday 25 August 2024, residents of the area between Mossel Bay and Gqeberha and the southern Karoo heard a noise described as like rolling thunder which persisted for more than 30 seconds, despite the sky being clear of thunderclouds. Some residents of this area also reported ground tremors.

This provoked a great deal of speculation on social media, with people hypothesizing an earthquake, landslide, vehicle collision, aircraft crash, gas or electrical infrastructure explosion, or other events. At 9.02 am, Zoë van der Merwe of Cape St Francis posted a a cluster of rapidly moving, bright, silver-white fireballs in the sky that extinguished within seconds in the general vicinity of Gqeberha.

Selected frame-by-frame analysis of Zoë van der Merwe’s video (reproduced with permission) showing the bolide post-disruption phase with multiple secondary fragments flaring individually over about two seconds before entering dark flight. Gibson et al. (2025).

There is currently a global effort to better understand atmospheric fireball events, involving organisations in many different parts of the world. In Southern Africa, the Astronomical Society of Southern Africa maintains a database of fireball events, with a dedicated webpage where members of the public can report events. They also actively seek out reports of fireballs on social media, and quickly became aware of Zoë van der Merwe's post, and other reports of the Nqweba event, leading them to share reporting guidelines on social media groups. They also received reports of a bulletin on Luister FM, a radio station based in Port Elizabeth, which stated that a meteorite had been observed falling into the sea off the Eastern Cape at around 8.55 am.

Armed with these sources of data, they set out to determine whether the observed objects were in fact derived from a Solar System body, rather than being Human-made space junk re-entering the atmosphere. This is less complex than it sounds, as space junk will typically enter the atmosphere at a low angle and with a slow velocity, most often as a series of such events as debris from the same object falls to Earth. The Nqweba object did not fit this profile, and its occurrence did not coincide with any known satellite debris re-entering the atmosphere, making unlikely that it was space junk.

Initial reports all suggested that the bolide was moving out to sea, possibly splashing down in Jeffreys Bay, to the west of Gqeberha. As more reports came in it became it had been seen over a much wider area, north as far as Petrusburg, and west as far as Ceres. A further three videos of the object emerged, although the one taken by Zoë van der Merwe appears to cover the final part of the meteor's journey.

Shortly before 9.00 am, residents of Nqweba (formerly Kirkwood), about 100 km to the north of Cape St Francis, heard what they described as a loud thunderclap, followed by a long rumbling noise. Slightly after this, 9-year-old Eli-zé du Toit observed something falling through a large Wild Fig tree in her parents garden. When investigated, this turned out to be a rock smaller than her fist, with a shiny black crust, broken in places to reveal a light grey, concrete-like interior. When touched, the exterior layer of this rock was hot, while the interior was cold. Eli-zé's mother, Jesica Botha, posted several images of this and other fragments found in the garden to social media groups, leading to her being contacted by Carla Dodd of Nelson Mandela University.

(a) Photo of main meteorite mass retrieved by Eli-zé du Toit, displaying black fusion crust (top) and the grey interior containing multiple angular rock and mineral fragments. (b) Post submitted by Jesica Botha on the Snow Report Southern Africa Facebook page. Gibson et al. (2025).

Carla Dodd was able to arrange for the meteorite fragments to be transported to Nelson Mandela University for safekeeping; meteorites, along with fossils and archaeological artefacts are protected in South Africa by the National Heritage Resources Act (1999). Here the fragments were weighed, examined and placed into desiccators for storage. This preliminary inspction suggested that the fragments belonged to a type of stoney meteorite called a HED (howardite–eucrite–diogenite) achondrite breccia. These meteorites resemble terrestrial igneous rocks, and are therefore presumed to have come from bodies large enough for magma differentiation and igneous processing to have occurred.

Initial witness reports, and the two sites where meteors were reported to have fallen to Earth, Nqweba and the sea off Cape St Francis, are about 100 km apart, suggesting that the bolide had followed a north-south trajectory, shedding fragments as it went, towards the sea. However, bolides are notoriously confusing for observers, due to the long gap between the visual fireball and the sound reaching witnesses. Careful examination of witness reports and data from remote observation stations eventually led Gibson et al. to conclude that the bolide moved southwest-to-northeast, first appearing off Mossel Bay and moving inland towards Nqweba.

The Nqweba Bolide was the 20th bolide recorded globally in 2024, and one of the smallest. It is thought to have been about 1 m in diameter when it entered the atmosphere, and to have released energy equivalent to that released by the detonation of 92 tons of TNT.

Since 1992, 493 fireball events have been recorded over South Africa, only about 3% of which have been visible during the day. The largest recorded bolide in Southern Africa was the 21 November 2009 event over northern South Africa and southern Botswana, which was probably about 200 times as large as the Nqweba Bolide, although no fragments of this were ever found.

Recovered meteorites in South Africa are strongly linked to observed meteorites, and particularly daytime events, with 21 of 51 known meteorites collected in South Africa connected to observed falls, 75% of these in the daytime. However, prior to the Nqweba Bolide,  the most recent of these fell on Lichtenburg, North West Province, in 1973, long before modern technology such as remote observation stations and mobile phones was available to help track these events.

South Africa is currently increasing its remote observation capacity, and therefore its ability to track fireballs.  It is currently home to 16 cameras running under the auspices of the NASA SETI Institute Cameras for Allsky Meteor Surveillance network, and a further ten operated by the Global Meteor Network (4 of which have been installed in Western Cape schools to promote STEM activities). These are already improving fireball-detection rates, but do not work well in daylight. The collection of meteorite fragments is largely dependent on direct observation of the objects falling, as was the case with the Nqweba Meteorite Fall, but networks of cameras can help triangulate the area in which meteorites might have fallen, improving the chances of finding meteorites which were not directly observed.

See also...

Friday, 11 April 2025

Fireball meteor over Luxembourg.

Witnesses across Belgium, the Netherlands, Luxembourg, Switzerland, northern France, western Germany, southeast England, northern Italy, and parts of Austria, have reported observing a bright fireball meteor around 2.30 am local time (around 0.30 am GMT) on Sunday 6 April 2025. The fireball is described as having moved from southeast to northwest, appearing over the Grand Est region of northeastern France and disappearing overr Luxembourg. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 6 April 2025 meteor seen from the Saint-Luperce, France. Romain Kropp/Météo-Centre-Val de Loire/American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as a luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

See also...


Tuesday, 25 February 2025

Fireball meteor over northern Germany.

Witnesses across Germany, the Netherlands, Luxembourg, England, and parts of Belgium, France, Czechia, and Poland, have reported observing a bright fireball meteor around 4.45 am local time (around 3.45 am GMT) on Wednesday 19 February 2025. The fireball is described as having moved from east to west, appearing near the Dutch border and disappearing to the northwst of Berlin. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 19 February 2025 meteor seen from Lüdenscheid in North Rhine-Westphalia, Germany. American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as a luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

See also...

Saturday, 7 September 2024

Asteroid 2024 RW1 impacts the Earth.

On the morning of Wednesday 4 September 2024, planetary scientist Jacqueline Fazekas working at the University of Arizona's Catalina Sky Survey detected a fast moving object, which she interpreted as a potential Near Earth Asteroid. She reported this to the International Astronomical Union's Minor Planet Center, where it was given the provisional designation CAQTDL2. This initial discovery was followed by a series of further sightings from other observatories, confirming that the object was an asteroid, which was then named 2024 RW1, and that it was on a collision course with the Earth.

Discovery images of Asteroid 2024, within purple circles. Catalina Sky Survey.

The designation 2024 RW1 implies that the asteroid was the 47th asteroid  (asteroid W1 - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 26, A2 = 51, etc., which means that W1 = (25 x 1) + 22 = 47) discovered in the first half of September 2024 (period 2024 R - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).

Asteroid 2024 RW1 is calculated to have had a 1450 day (3.97 year) orbital period, with an elliptical orbit tilted at an angle of 0.53° to the plain of the Solar System which took in to 0.74 AU from the Sun (74% of the distance at which the Earth orbits the Sun) and out to 4.23 AU (4.23 times the distance at which the Earth orbits the Sun, and almost three times the distance at which the planet Mars orbits). It is therefore classed as having been an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). 

The calculated orbit of asteroid 2024 RW1. JPL Small Body Database.

Asteroid 2024 BX1 is calculated to have had four close encounters with the Earth before finally impacting, with the first in August 1912, and the most recent in October 2020. It has also had close encounters with Venus in June 1966 and January 2009, and Jupiter in November 2006 and September 2018. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.

By 11.00 am GMT on 4 September 2024, the European Space Agency had calculated that Asteroid 2024 RW1 would impact the Earth, entering the atmosphere at about 5.08 pm over or close to northern Luzon Island, the Philippines. In the event the asteroid entered the atmosphere at 4.46 pm GMT (0.46 am on 5 September, Philippines time) over the Pacific Ocean to the east of Luzon, producing a bright fireball meteor, with a distinct green colour, which probably indicates that it had a high magnesium content. 

A bright fireball meteor observed from Tuguegarao City in the Philippines on 5 September 2024, thought to have been caused by the impact of Asteroid 2024 RW1. Marvin Coloma/American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. It is possible on this occasion the object is known to have produced meteorites that reached the surface (an object visible in the sky is a meteor, a rock that falls from the sky and can be physically held and examined is a meteorite).

Based upon observations in space and on entry to the Earth's atmosphere, 2024 RW1 is calculated to have been about a metre in diameter, and to have had a high magnesium content, something which in turn implies a stony meteorite rich in the mineral olivine (counter to possible expectations, metallic meteorites seldom contain much magnesium). However, as it fell to Earth over the Pacific Ocean, it is unlikely that any fragments of the asteroid will be recovered to test this hypothesis. 2024 RW1 is the eighth asteroid ever to have been discovered before impacting the Earth.

See also...