The sudden appearance of a meteor, commonly known as a shooting star, strikes awe and wonder in sky-watchers worldwide. While ancient observers had several different interpretations for these fleeting occurrences, we know today that meteors are the result of small fragments of rock entering the Earth’s atmosphere, heating up due to friction with air and causing the gases around them to glow as a result.
However, while on most nights we get a few, sporadic meteors, we get specific periodic increases in the number of meteors we observe on any given night, with these meteors seemingly originating from a particular region in the sky – a radiant.
Indeed, the Earth periodically experiences meteor showers, typically extending a few days or weeks. These meteor showers are typically annual, and thus predictably increase in a specific calendar period.
For the Perseid meteor shower, this period starts roughly around mid-July and ends in late August, with the peak of the shower occurring between August 11 and 13.
The Perseid meteor shower is so named because of the radiant of the Perseid meteors, which is in the constellation Perseus, and the peak hourly rate for this meteor shower can sometimes exceed 60 – thus averaging more than one meteor per minute.
The reason behind their periodicity involves their origin. In most cases, periodic meteor showers are a result of our passage through a debris field left in the wake of a comet that intersected, or almost intersected, with the Earth’s orbit at some point in the past.
The Perseid meteor shower is so named because of the radiant of the Perseid meteors, which is in the constellation Perseus
As the Earth passes through this debris field, it will encounter small fragments that broke off from the main comet nucleus in the past and that would be following in the orbital path of the original comet itself. Since the comet would have intersected the Earth’s orbital path in one specific region, we get a meteor shower during the time period in which Earth crosses that position annually.
Comet Swift-Tuttle is responsible for the annual Perseids. The comet has a 133-year orbital period around the sun and last entered the inner solar system in 1992. While some initial calculations had provided some cause for concern for the comet’s next perihelion passage in 2126, it has now been verified that the comet will pose no risk of collision with Earth and will pass at distances of around 22 to 23 million kilometres in both 2126 and 2261.
The comet will make a closer approach to Earth in the year 3044, with an estimated closest approach distance of approximately 1.6 million kilometres.
As in previous years, the Astronomical Society of Malta will be organising an observation night event, open for the general public, for the observation of the Perseids on the night of August 13 at Ndawar (close to Żonqor Point) in Marsascala. This year will be particularly favourable for observing the Perseid meteor shower, with only a very thin moon crescent mildly hindering observations in the early hours of the morning, when the Perseid radiant will be high above the horizon.
Josef Borg completed a PhD in astronomy at the Institute of Space Sciences and Astronomy, University of Malta, and is currently a researcher at the Faculty of Health Sciences at the University of Malta. He is also Malta’s representative on the European Astrobiology Network Association (EANA) council.
Sound Bites
• The James Webb Space Telescope (JWST) captures stunning near-IR image of two forming stars. Herbig-Haro 46/47 are a pair of actively forming stars, some 1,470 light years away, that have been a target for JWST. The telescope has imaged the pair of forming stars while spewing ejecta, in the form of two large lobes, considered of significant importance during star formation. The stars are actively maturing at present, in a process expected to conclude in millions of years.
https://www.space.com/james-webb-space-telescope-stuns-with-glowing-portrait-actively-forming-stars
For more soundbites, listen to Radio Mocha every Saturday at 7.30pm on Radju Malta and the following Monday at 9pm on Radju Malta 2 https://www.fb.com/RadioMochaMalta/.
DID YOU KNOW?
• Comet Swift-Tuttle, responsible for the Perseid meteor shower, is the largest near-Earth object to intersect the Earth’s orbit. Measuring some 26km across, Swift-Tuttle is by far the largest near-Earth object to cross our planet’s path, with its size having caused concerns in the past regarding the potential dangers posed by the comet to Earth. However, careful analysis of previous sightings of the comet have shown that the comet poses no significant risk of collision with Earth for the next two millennia.
• There are two main types of comets, classified depending on their orbital period. Short period comets are identified as those having an orbital period of less than 200 years, while long period comets have longer orbital periods. The difference in orbital periods is mainly due to their origin, wherein short period comets likely originate from the Kuiper belt or scattered disc while long period comets likely originate from the Oort cloud.