The Orionid meteor showing is coming or is it?

Created using Stellarium 0.11.0
Created using Stellarium 0.11.0

On a dark clear night who hasn’t looked up to see the last hint of meteor fading from sight? “Damn it why couldn’t I have seen all of it?” And then perhaps minutes, hours or nights later you do get to see one while everyone else is looking the wrong way! Looking for meteors or “shooting stars” can be very frustrating.

Every now and then however the probability of seeing some increases as the Earth silently glides through the dust trail left behind by a comet. This causes a meteor shower.

Next month is one of the better chances or is it? The Orionid meteor shower this year should start around October 2nd and go through to November 11th but the peak is from October 19th to the 22nd.

The Orionids are the result of dust left behind by that most famous of comets, Halley that last swept by in 1986 and will return in 2061. As the Earth rotates on its axis while orbiting the Sun the relative velocity of up to 70km/s makes short work of the dust hitting the atmosphere between 80 and 120km up. The result is a short sharp streak of light in most cases though sometimes a more spectacular fiery event can be seen lasting for several seconds.

So what can we expect this year? A lot depends on the observer’s location. In a bright city or dark country side, clouds, fog and latitude. The closer to the horizon the key point known as the Radiant is the poorer the view and the number of visible meteors drops.

For the Orionids the Zenithal Hourly Rate (ZHR) and therefore maximum under PERFECT conditions is above 23 meteors per hour. For major locations like Sydney this drops but be how much?

The following formula helps.
formula4

Where HR is the hourly rate for an observer, r is the population index, in this case 2, which describes the numbers of fainter meteors of each magnitude, LM is the observer’s average limiting magnitude ie how bright the sky is. For cities like Sydney this would be about 4.5 until the time of Moonrise when the sky becomes much brighter. A is the altitude of the shower’s radiant above the horizon in degrees which sadly for the 22nd will only be about 17 degrees above the ENE horizon.

formula2

So for Sydney at around 2am on October 22nd (Moonrise is at 2:39am)

formula3

(HR) = 0.84 which is sadly well below the sporadic or background rate of 4.

This means this years Orionids are effectively a non-event for us on the East coast of Australia in 2011 as the radiant is so low before the rising waning Moon. Maybe we will have better luck next year!

(1) http://www.namnmeteors.org/

Share

19 responses to “The Orionid meteor showing is coming or is it?

  • Thanks for your research. I accept it may have been spacejunk coming in as it entered from low in the sky and went across and wasn’t up high in the sky falling straight down. I was reading about the German satellite Rosat due for reentry last week and also the Elenides comet which all sounded so similar all due last week.The only thing I can stipulate was that this really big item did not break into several pieces but seemed to be just 1 large fiery light.  On the Rosat website it said:

    Tracking stations will typically witness the uncontrolled return of at least
    one piece of space debris every day; and on average, one intact defunct
    spacecraft or old rocket body will come back into the atmosphere every week.

    Something the size of Nasa’s UARS satellite is seen to enter uncontrolled
    perhaps once a year.

    Much larger objects such as space station cargo ships return from orbit
    several times a year, but they are equipped with thrusters capable of guiding
    their dive into a remote part of the Southern Ocean.
    I found the research really interesting at 

    http://www.bbc.co.uk/news/science-environment-15402157

    http://abcnews.go.com/Technology/space-junk-nasa-predict-entry-certainty/story?id=14587907
    Also the doomsday comet “Elenin” sounds like the description on http://www.space.com     website which was all in the same week as our sighting.  This event has really inspired me to watch for extra terrestial & amazing sights in the heavens. There really is another world out there.

  • I was coming home at around 11.22pm a few hrs ago on Tu night 18/10/11 & my 18 yr old daughter and I saw in the west low in the sky this fantastic meteor.  It was travelling at super fast speed just like halley’s comet and it had a tail.  It was spectacular and was travelling north across the sky. I hope the sky is filmed & there can be some footage captured so everyone can see it.  I have never seen anything like it – it was incredible.  I yelled whoa look at that! Did you see that!!!! My daughter said wow!!! It moved so fast it was unbelievable.  Please put something on this website about it.  Was it the Orionid meteor??  It sounds like it.

    • Hi Chris. Sadly the wrong direction altogether as the west was home to Capricornus last night at 11:22pm and Orion was about to rise in the East. It would appear as though you saw a sporadic meteor. Spectacular yes but an Orionid no. Quite possibly no bigger than a golf or tennis ball entering the upper atmosphere to a rather warm, due to friction, reception hence the fireworks.

      • Hi Geoffw, aren’t sporatic meteors just falling or shooting stars as I have seen plenty of them and this was not just a falling star. It most definately was a meteor excelerating north direction across the sky lasting several seconds with a fiery tail which seemed to disinergrate (like fireworks do) when it past by.  It was going toward Qld way and it looked like a steam train light speeding in the dark travelling at great speed. It seems that at this exact time of date it was a predecessor to the Orionids that are to come. What do u think?

        • Hi Chris

          Meteor showers are named for the part of the sky they come from. What you saw, coming from the region around Capricornus, is not therefore an Orionid but that doesn’t make it any less exciting I hope? Shooting stars are just a common name for meteors. Some are bigger than others but they are all fundamentally the same, small pieces of dust and rock burning and heating the atmosphere as they crash into it. The larger ones, golf ball size and up can disintegrate and explode causing exactly the same effect you described. These happen every day and are a great sight to enjoy.

          There is however very little interest in them unless there are reports of pieces landing and a chance of recovery.

          Sadly there is no 24 hour sky camera.

          Kind regards
          Geoff

          • I called up the observatory today. And had a chat to an astronomer. After describing what i saw, he said the most likely cause was Space Junk. A piece of satellite that falls somewhere random and unpredictable, so there was no way of being 100% certain. I have looked up videos, and this big bright light (Which did not shoot across in seconds like a sporatic meteor/shooting star) was visible for atleast a minute as it moved north east and gradually fell down.
            Look up videos of UARS falling to earth. An identical looking object fell over the east coast on Tuesday.
            Everyone who saw it with me agrees, this thing looks exactly the same.
            Pretty sure this is what we saw on Tuesday night. A Man made object, not part of a meteor shower.
            Hope this helps Chris. Im settled.

          • Last night, at 10.30pm we saw a beauty… a bright green meteor across at least two full handspans of sky in the northeast. halfway between Jupiter (at that time) and Orion (which was mostly still below the ENE horizon… We’re at Mallacoota in Victoria.

      • I would love to hear an explanation too, as would a couple of people who
        saw this thing with me, it was not a shooting star, we were close
        enough to the object to see it eventually break apart, it was pretty
        big, considering the “Chunks” breaking off were clearly visible. I was actually pretty scared of a big impact, let alone the pieces which must have fallen somewhere….
        I have never seen anything like this and ive seen quite a few interesting things in the skies over the years, all of them explainable except for this amazing thing, which hasn’t even been reported yet… So, it would be really amazing to have this explained, my mind wont rest on it. Its making me annoyed at the pointless things that are reported, when something so amazing goes un-noticed.

        • I agree.  I even called our local radio station 102.90  being KOFM who recorded my conversation and then replayed part of it on air today about the meteor which I was pretty rapped about. No one else seemed to know anything about it or saw it in our area of Newcastle.

    • I saw something similar at about 11:30, a massive white ball leaving a thick streak of white smoke behind it, me and my friends watched as it fell and eventually broke apart, it was fast but the time from when we saw it to it breaking apart was about 30 seconds. It was massive, not small at all. I’ve never seen anything so spectacular.

      • Where abouts are you situated?  Are you in Sydney or another state? I’m glad you saw it. My 18 yr old daughter saw it too.  It was really big and I agree it was spectacular.  I saw it for about 4-5 seconds & it went north out of my view.

        • Yeah, I live in the northern suburbs of Sydney. Angry at myself that I didn’t get a photo or video, I was just in awe, kind of scared actually, I didn’t even think of taking a video, I thought it was going to crash down somewhere, it seemed pretty low when it eventually broke up completely.

    • Also witnessed it from Bronte, was outside looking West, it travelled low and fast from south to north across the sky.  Was visible for a long time and very, very cool to watch

      • So glad other people have seen this. I will be watching for more tonight.  I was so excited last night after I saw it that I found it hard to sleep.

      • Talked to an Astronomer at Sydney Observatory. Discussed what i saw, He said it was most likely “Space Junk” Although there is no way to be 100% sure.
        Look up Satellite UARS re entry footage. This is similar to what i saw, and i accept this explanation. What do you think?

Leave a Reply

Your email address will not be published. Required fields are marked *