| The Geminids are coming….The debris left behind by asteroid (3200) Phaethon are visible as the Geminids meteor shower when these particles enter the Earth’s atmosphere. The shower peaks on the 14th December. Best time to look is a day prior and a day after the peak (13th 14th & 15th Dec), looking towards the constellation Gemini from around 02:30 in the morning.
Although text and graphic below are 7 years old they both still apply. Except for the dates of course. Many thanks Auke Slotegraaf, co-editor of Sky Guide Africa South with Ian Glass.
As you read this, our planet Earth is moving through a zone of interplanetary space filled with gravel and tiny rocks. As these bits hit our Earth’s atmosphere, beautiful meteors are seen to flash across the night sky. Some of these space stones are the size of grapes, and they produce spectacular and memorable fireballs – brilliant meteors that are about as bright as Venus! This rocky material has a very curious origin: they are bits broken off from an unusual asteroid that astronomers call Phaethon. The asteroid is named after the son of the Sun god Helios (in Greek mythology) because its orbit carries it very close to the Sun — closer than even Mercury ever gets to our star. On these close approaches the Sun’s heat probably causes the 5-km sized asteroid to expand unevenly, and as its surface fractures, it sheds debris into space. Further evidence that this asteroid is slowly crumbling into dust comes from space craft observations that show dust tails sprouting from its surface as material is ejected. In some respects, therefore, Phaethon resembles a rocky comet! Phaethon is a dark horse on many accounts. Not only is very little known about it but it is also literally dark: its surface reflects about as much light as a tarred road! Despite the fact that Phaethon moves quite close to the Earth from time to time, and also crosses the orbits of Mercury, Venus and Mars, it was only discovered in 1983, when it became the first asteroid to be found on photographs taken by a space craft (the IRAS satellite).Every year, as our planet plows through the debris field strewn by Phaethon, meteor watchers get the opportunity to enjoy a meteor shower. For a few nights, centred on December 14 (12:00 UT), more meteors than usual can be seen in the sky. Since these shooting stars appear to come from a patch of sky in the constellation Gemini the Twins (near the bright star Castor) astronomers speak of the “Geminid Meteor Shower”. Nobody knows how many meteors will be seen during the Geminid shower – which is why astronomers conduct a “meteor watch”, to count and describe the activity. On a normal night, when there is no meteor shower, about 4 meteors can be seen per hour. The Geminid shower can produce up to 120 per hour! (Remember that even this high rate is still only two shooting star every minute: a LOT more than you see on a typical night, but not the fireworks display that you see in sci-fi movies!)When the Geminid meteors hit our Earth’s atmosphere, they are travelling at an astounding 126,000 km/h! It is the energy of this motion, rapidly lost as it collides with the atmosphere, that causes the asteroid fragment to be super-heated and vaporised. As the doomed particle rushes earthward, it causes the surrounding air molecules to glow, creating a long, thin strip of glowing gas – about 1 metre thick but tens of kilometres long! This beautiful flash of light is most active this weekend — Sat/Sun Dec 13/14, and Sun/Mon Dec 14/15. Observe from midnight until the start of twilight, and look for shooting stars that appear to come from the direction of Castor in Gemini. And keep a bright eye open for those fireballs!
SOURCE: SOUTHERN CAPE ASTRONOMY CLUB | |
