Meteors of all sizes enter the atmosphere – day and night. We see these meteors as flashes and trails of light (also known as falling stars), but every so often we see one so spectacular that it seems to be within arms reach. These bright meteors are commonly known as fireballs.
A Meteors Classification to be Called a Fireball
Meteors are unpredictable and they can appear at any time of day or night. They can be so faint that they are not detectable with the naked eye, or they can be as bright as the Sun; bright enough to light up the night sky just as if it were day.
Fireballs are classified by typically producing a brightness of magnitude of -2 or brighter. In this case, the brightness, or “magnitude”, is a scale of measuring brightness (or faintness) in celestial objects. For example, Venus, the second planet from the Sun, can get as bright as magnitude -4.5 or sometimes slightly brighter.
Venus is commonly noticed as “the bright star” just after sunset in the western skies or just before sunrise in the eastern skies – according to its position in the sky and the time of year. The full moon produces a light-magnitude of -13 while the Sun is a whopping -27. The faintest night sky objects observable with the naked eye are around magnitude 6. These numbers give you a basic idea of how magnitude is calculated.
The Bolide Family of Meteors
Bolides are meteors that produce a bright “flash” before finally burning out. Theoretically, a bolide could be a fragment of a comet, or a meteoroid that contains internal water-ice. When the water-ice begins to heat due to the heat generated from atmospheric entry, pressure caused from the boiling water inside the meteor causes the object to explode. A bolide can produce a single flash just before disappearing, or they can create multiple flashes throughout their entry.
Video of a Bolide
Observing Meteors – The Possibility of Witnessing Bright Meteors and Fireballs
On average, and under average sky conditions, approximately six to ten non-fireball meteors per hour can be observed. Still, this number is an approximate and there is no definite amount of meteors that can be observed. They are unpredictable. As with brighter meteors and fireballs, they too are unpredictable but it is possible to see at least one fireball per night.
To increase the possibility of observing a fireball, it is better to watch during known annual meteor showers. During these times, it is expected to witness a larger number of meteors – sometimes even hundreds of meteors per hour. It is during these meteor showers where fireballs are more likely to be observed.
A Historical but Missed Fireball – 2008 TC3 in Sudan
On the night of October 7, 2008, a previously discovered asteroid dubbed as 2008 TC3 entered Earth’s atmosphere over Sudan. This small asteroid (or large meteoroid) was discovered the day before by Richard Kowalski, while scanning the skies for undiscovered Near Earth Objects with the Mt. Lemmon Survey telescope.
2008 TC3 entered the atmosphere over an area of Sudan that was very remote. Although the smoke trail left from the remains of the fireball was recorded, the fireball itself was not documented by anyone with a camera. A few weeks later, scientists began searching the “strewn field” of the asteroid and collected a number of specimens of the asteroid. This was the first asteroid (or meteoroid) in history to be detected by a telescope prior to impact.
Reporting Fireballs and Bright Meteors
The American Meteor Society offers an open database for individuals to report bright meteors and fireballs. These reports are used to create a database of fireballs observed by anyone interested in reporting their observation. The easy to fill out form provides simple instructions on completing the fireball report.
References:
Red Barn Observatory, Georgia Fireball Network, Bolide Video, site referenced, 1/12/2011
NASA, Astronomy Picture of the Day, On the Trail of 2008 TC3, 2008, site referenced 1/12/2011
Catalina Sky Survey, Mt. Lemmon Observatory, site referenced 1/12/2011
NASA, Dawn Dictionary, Magnitude, site referenced 1/12/2011
Steve Farmer - Steve Farmer Jr. is an individual of many interests and hobbies. When not spending time with his wife and four children, he is an employee ...
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