Major Southern Hemisphere Meteor Stream Information.
Taurids North and South (NTA) (STA)
The Taurids consist of two radiants, the North Taurids and the South Taurids. The Taurids are related to the periodic comet Enkie. It is has been calculated, by looking at the orbits of the meteors seen that the streams were produced by outbursts from the comet both 4700 years ago and 1500 years ago.
The two streams are similar in location to each other, one being 9º further North than the other. This year the maximum of the South Taurids falls near the full moon, however, the maximum of the North Taurids falls 3 days after the last quarter moon and is well placed to observe. Due to the long duration of the Taurids streams they can be observed over many months and you can get a good amount of data on the shower.
Taurids meteors are slow in speed when seen on the sky and are brighter than average with an average magnitude (r) of +2.3. In recent years it is thought the Taurids have been responsible for many fireballs, it is possible observers, because of their slow speed, have noticed them more readily. Taurid meteors are most often white and yellow in colour, about 6 % appear to be orange. Other colours make up about 1%.
If possible, care should be taken in deciding which stream the meteor you see comes from. It is easy to decide if the meteor appears parallel to the horizon, however if you cant decide if it was either a South or a North just list the meteor as a Taurid, the observation is still important. A finder chart is provided to make it easier to identify. (Chart 2)
The Chi Orionids are one of several streams who have both a North and South comments. This was revealed by photographic surveys in the 1950's. Meteors from both the North and South Chi Orionids tend to be bright with some leaving trains, about 14%. Chi Orionid meteors are slowish in speed (V=25-30°sec) The Chi Orionids have been known for around 100 years however due to them being at maximum near the time of the Geminids they are often overlooked for observing. A study of the stream by the WAMS with Jeff Wood showed a colour break up as follows: White 64%, Yellow 31%, Blue or Green 5%. For the streams position to observe, see Chart 1 above.
Much is known about the Geminids meteor stream. The parent body of the Geminids is the asteroid 3200 Phaethon. It was the first asteroid to be linked to a meteor stream. The stream first appeared in the 1860's, first noted in 1862. Rates of the Geminid stream were lower in the past, generally between 10 and 30 until 1930. Since 1930 the rates have been steadily increasing and are now around a Zenithal Hourly Rate (ZHR) of 80-110.
The increase in rates of the Geminid stream can be linked to the changing nature of the streams orbit. The orbit of the Geminids stream is affected by the two planets Earth and Jupiter, Jupiter by far having the greatest effect. The gravity of Earth and Jupiter is causing the stream to move and hence rates of activity to change. In 1700 the orbit of the Geminids was 0.1337 AU inside the Earth's orbit, in 1900 it was 0.0178 AU inside the Earth's orbit, in 2100 it will be 0.1066 AU outside the Earth's orbit. Activity is now increasing but it will eventually decline and become non-existent.
The average magnitude of Geminid meteors is on average +2.6. At different stages over the time the stream is active the average magnitude of the meteors seen changes. Around Dec 7 the average magnitude is +2.14, Dec 9 this brightens to +1.63, by Dec 13 this fades to +2.41 just before the maximum on Dec 14. Over the next several days this brightens again so by Dec 18 it is up to +1.60. Two days before maximum it has been found that the there is encountered a moderate concentration of smaller particles. The Earth then moves into a region of larger particles producing brighter meteors.
The Geminids, when near maximum, remain above half the maximum rate for around two days, this is quite a large window of opportunity and with the moon favorable this year, it is a great chance to view the stream. When watching for Geminids it should be noted that the meteors are often yellow in colour with very few trains produced. In fact only 4% of Geminid meteors on average produce trains. Geminid meteors are of an average speed.
Enjoy watching the Geminids, from a dark location such as the ASV site at Heathcote an observer could expect to see anything from 20 to 50 Geminids per hour on the night of maximum, 50 per hour would be under ideal conditions and a limiting magnitude from +6.5 to +6.8, expect 20 per hour and you may be surprised. From an outer suburbs location with a limiting magnitude between +5.5 and +6.3 rates of 10 to 30 per could be expected. The rates will never be as high as the ZHR indicated as the radiant for the Geminids never climbs above 20° in elevation. For the streams position, see Chart 1 above.
The Monocerotids are a more minor stream in comparison to the others listed in this group. The peak ZHR of this stream is 5 per hour and the meteors are of a medium speed. The Monocerotids reach maximum on December the 10th, 4 days ahead of the Geminids and may be affected a little by a Last Quarter moon this year. For Positions, See Chart 1 above.
The October Capricornids provide variable activity from year to year. They are active from Sept 20 to October 14 with an overall maximum on October 3. This is close to the new moon and should be OK to observe. Anyone intending to observe this stream should face the radiant position and take care in identifying these meteors. It is recommended that you plot the meteors from this stream.
The Sigma Orionids are active from Sept 10 to Oct 26. It has a maximum ZHR of around 3 per hour on Oct 5. This stream is also well placed with a new moon on the 2nd of Oct. The radiant at maximum will be located in the Belt of Orion, so after maximum, great care needs to be taken in distinguishing the sigma Orionids meteors with those to the October Orionids. Best time to observe is a few hours before sunrise. Face no more than 30 degrees from the radiant position. If possible plot meteors from this stream as it makes it a lot easier to identify stream members.
Alpha Monocerotids (AMO)
The Alpha Monocerotids are noted for their variable activity. Some years they are virtually non-existent, in other years the maximum ZHR has exceeded 100 meteors per hour. With a maximum on November 20, a gibbous moon heavily affects this stream, however, it is still worth a look. It is recommended by the IMO that observers try to observe both the Leonids and the Alpha Monocerotids at the same time whenever both streams area more than 20 deg above the horizon. For the best results, center your field in a region RA 120 deg to 150 deg and DEC –20 to +30 deg.
The Chi Orionids stream is active from November 6 to December 15. A ZHR of 3 is reached in early December with little interference from the moon this year. The Chi Orionids are characterized by being very slow and brightly colored meteors. Observers who choose to monitor this shower should center their field of view at about RA 90 deg and DEC +20 deg for best results. Once again, plot the meteors if possible.
This stream is active from Nov 28 to Dec 9 with a maximum on Dec 5. This stream produces variable activity. Rates usually range from 2-10 per hour. On a couple of occasions, notably in 1956 and 1974 rates reached 100 and 25 respectively. This year the maximum and most of the streams activity is moon free and it is best observed in the early evening hours.
Alpha and Beta Centaurids (ACE)
This discovery of this shower should be attributed to Michael Buhagiar (Western Australia), who obtained observations of both Centaurid radiants during 1969-1980. In his "Southern Hemisphere Meteor Stream List" of 1980, Buhagiar listed two radiants that reached maximum on February 7. Radiant 290 was active during February 6-8, from RA=206 deg, DECL=-57 deg, while radiant 299 was active during February 5-9, from RA=214 deg, DECL=-64 deg. Both radiants were referred to as "Beta Centaurids." Although both radiants have continued to be observed following the publication of Buhagiar's meteor stream list, observers have rarely distinguished between the two radiants during the same year.
During 1979, members of the Western Australia Meteor Section (WAMS) managed to observe the "Alpha Centaurids" during February 2-18. At maximum on February 7, the radiant at RA=216 deg, DECL=-59 deg. During 1980, the same group observed members of the "Alpha Centaurids" during February 2-24. They noted that maximum came on February 8, from RA=209 deg, DECL=-58 deg. The 1979 radiant obviously represents the true Alpha Centaurids, while the 1980 radiant is the Beta Centaurids. (credit to Gary Kronk for above info)
The average brightness for the above streams varies, the Alpha Centaurid stream having a brightness of +2.45 and the Beta Centaurid stream an average brightness of +1.6 approximately. The streams drift by 1.2 deg per day RA and –0.3 deg per day DEC. The diameters for the radiants are 4 degrees. The meteors seen emanating from this area may be hard to distinguish into individual streams because of their closeness. Although it is best to try and distinguish between stream member, if you are unable to do so, just record the meteors as “Centaurids”, the information is still very valuable.
Pi Puppids - Grigg/Skjellerupids (PPU)
The Pi Puppids, otherwise known as the Grigg/Skjellerupids are active between April 15 and April 28 with a maximum on the 23rd of that month. The stream is associated with the periodic comet Grigg/Skjellerup. From Australian observations it has been determined that about 55% of the meteors are yellow and about 20 % are orange in colour. 16% of the meteors from this stream exhibited persistent trains and meteors will have a very slow appearance. Average magnitude for Pi Puppid meteors is between 1.9 and 2.3 (listed as 2.0). This means that overall, meteors emanating from this radiant are brighter than average. The maximum rates for this stream during a period of increased activity can vary between 18 to 42 meteors per hour, but a ZHR of around 15 is likely at maximum. The Pi Puppids may have increased activity this year with the return of P/ Grigg/Skjellerup and is definitely worth looking out for.
The Lyrid meteor shower is a highly variable shower which can produce storm activity up to around 100 per hour. This is uncommon and rates usually in the order of 10 ZHR are normal. The rates will stay within ¼ of the maximum ZHR for about 4 days around the maximum period. The last outburst form the Lyrid shower was in 1982 when rates recorded from Colorado in the USA reached around 90-100 per hour. The average magnitude of Lyrid meteors is around 2.4 and they are described as rapid in appearance. The usual colour is white and about 15 % leave persistent trains. Increases in activity of Lyrid meteors is characterized by a drop in the average magnitude of the meteors showing that during periods of increased activity, there is a higher proportion of fainter meteors. The Lyrids are worth observing in any year just in case of an outburst.
The Sco/Sag shower is a large radiant complex in the Scorpius and Sagittarius area of the sky. It is active for a long period of three months starting on April 15 and ending around July 15. More data is needed on this shower. The shower has several maxima reaching a ZHR of around 10. The stream has a large radiant diameter of 15° in RA by 10° in Dec and meteors coming from this radiant will have a slow-average speed. This stream is well placed for Southern observers.
Eta Aquarids (ETA)
The Virginids are a stream of very long duration being active from early February until late May. Virginid meteors will appear to emanate from a very large radiant 15° in RA by 10° in Dec and will travel at a fairly slow speed across the sky. The Virginid stream has several maxima where the ZHR may reach between 5 and 10 meteors per hour but I can find no listing for an actual date of maximum for any of the sub-maxima. Virginid meteors should be easy to identify with there slow speed and large radiant size. This is a stream which needs more observation and can be monitored earlier in the night before the Eta Aquarids rise.
Sth and Nth Delta Aquarids (SDA) (NDA)
One other stream to observe is the South Delta Aquarids. This stream produces a ZHR of around 20 and is fairly consistent. This year the moon has little interference with this stream and it should be easy to observe. The South Delta Aquarids are closely related to another stream the North Delta Aquarids which appears around 10° north in declination. This stream produces lower rates (ZHR around 5) and reaches maximum about a week later. The South Delta Aquarids have a RA of 22h 30m and a Dec of -16°. The North Delta Aquarids have a RA of 22h 20m and a Dec of -5°. Their period of activity is from July 12th to Aug 19th with a maximum on July 28th. Both Sth and Nth Delta Aquarid meteors are of a medium speed. Because of the close proximity of the radiants care should be taken when identifying which stream meteors come from when seen emanating from this area.