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Home of South Common Observatory
Written by Richie Jarvis
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Friday, 01 August 2014 15:50 |
Last night, I was taking 2 minute exposures of the constellation of Cygnus the Swan from my observatory. This morning when I went through the exposures, I discovered I had caught something in one of the exposures. It didn't look like a meteor, as it appeared to rise and fall in brightness over a period of time, whereas a meteor I would expect to start off dim and get brighter and then vanish. My suspicion was that it was a satellite - specifically one of the Iridium group of satellites.
The Iridium satellites are used for satellite phone calls. They are named because it was originally intended to launch 77 satellites providing call coverage around the globe. However, it was determined that all 77 satellites were not needed to provide full worldwide coverage, so there are currently 66 operating satellites in orbit, with 6 spares in a holding orbit. The orbital height of the operational satellites is 485 miles on average. They are travelling at 16,832 miles per hour, and complete one orbit of the Earth every 100 minutes.
The reason for the flare seen in the picture is that these satellites have 3 door-sized antennas angled at 40 degrees away from the main body of the satellite itself. They are arranged equally, with 120 degrees between them. When the light from our Sun hits the antenna, about 4-5 times a day the reflected light create a 6.2 mile wide circle of light on the surface of the Earth. To an observer, this appears as a bright flash of light which suddenly gets brighter, then dimmer as the satellite moves over their head. The date and time of each flash is easily predictable, as the orbit and attitude of the satellite is known precisely.
To find out whether I had accidentally caught an Iridium flare, and check which satellite and antenna my camera saw the reflection from, I checked on http://www.heavens-above.com, which provides detailed prediction for most satellites circling the Earth, including the International Space Station and Iridium Flares.
I was able to determine exactly which satellite I had captured - Iridium 72 - and the reflection was from the front facing antenna (its direction of travel). At the time of the flash, the satellite was 640 miles away.
Here is the track of the satellite from Heavens-Above.com showing the predicted position of the flare:
I PDF'd a version of the Flare information from Heavens-Above.com, which you can download here. |
Last Updated on Friday, 09 February 2018 22:05 |
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Written by Richie Jarvis
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Saturday, 19 July 2014 15:22 |
I've taken many pictures of parts of the Veil Nebula over the years - you can see them in my Galley. Back in the days when the New General Catalogue was compiled (thats where the NGC designation comes from), the parts of the Veil Nebula were given separate designations.
This year, I decided to see if I could take a picture of the whole of the Veil Nebula. My camera (SXVR-H18) and telescope (101mm @ F/7) combination can only see 1.4 x 1.1 degrees at F/5.6 with my Televue Focal Reducer, so to get the complete veil requires taking images of different areas of the sky, and stitching them together. You can see the boundaries of the panes in the image above. Each 'pane' is the result of stacking many images together. So far there are 97 images making up this mosaic. So far, I have been concentrating on the Hydrogen emission wavelength with my Ha narrowband filter.
This will be a several year project, as I then need to shoot with an Oiii (Oxygen) filter, and then choose whether to shoot with an Hb (Hydrogen Beta) or Sii (Sulphur). I might even be able to incorporate some of the data from previous imaging runs - time will tell. I have some gaps to fill in the Ha band - I just need some clear nights!
Here are some of the other pictures I hope to incorporate should the inclination take me:
NGC6992/NGC6995/IC1340 is known as the Eastern Veil, or Network Nebula NGC6992 is the bright area, NGC6995 is the 'rectangle' element of the Eastern Veil Nebula. Between the Eastern and Western Veil, Pickerings Wisp is the fainter triangle shaped structure NGC6960 is known as the Western Veil, Witches Broom, Finger of God, of Filamentry Nebula
At a distance of 1,470 light years away, the Veil Nebula is the result of a supernova which is thought to have exploded 5,000 to 8,000 years ago. The resulting gas and dust released spread out into this 3 degree area of sky (roughly 6 times the diameter of a full moon) in the time since the explosion. It is one of the largest, brightest features in the X-ray band. The dust and gas is estimated to be travelling at the huge speed of 370,000 miles per hour away from the original star which spawned it.
Read more about the Veil Nebula and see a beautiful picture from the Hubble Space Telescope here: http://www.space.com/4136-veil-nebula-pierced-hubble-gaze.html
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Last Updated on Friday, 09 February 2018 22:05 |
Written by Richie Jarvis
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Wednesday, 22 January 2014 21:14 |
This morning, I saw an interesting email come into my inbox. It reads as follows:
Subject: [vsnet-alert 16812] Re: PSN J09554214+6940260: bright (11.7 mag) supernova in M82 At UT 2014 Jan 22.305, we obtained a spectrum of PSN_J09554214+6940260 (discoverer: S. J. Fossey) with the Dual Imaging Spectrograph on the ARC 3.5m telescope. We classify this as a Type Ia supernova with a Si II velocity of 20000 km/s. The best superfit match is SN2002bo at -14d. The supernova has a red continuum and deep Na D absorption.
A type 1a supernova is what happens when a binary star system starts to tear itself apart. In essence, a very small dense white dwarf rips the material from the surface of its neighbouring star. It appears to be relatively common when one of the stars in a binary star system inflates when it becomes a red giant. The surface of the red giant is now much closer to the companion star, and so matter starts to transfer from the red giant to the smaller star. As the smaller star accepts matter from the giant, the system becomes unstable, and the small white dwarf explodes violently.
The velocity quoted above shows that the shockwave of this star exploding is travelling at 20,000 km/s - thats almost 12,500 miles per second - pretty quick.
Type 1a supernovae are special because they allow astronomers to accurately gauge the distance from the Earth of the galaxy that spawned it. Each one that is identified gives astronomers much more accurate data about the Universe around us.
I managed to gather a quick snap of Messier 82 tonight before the clouds rolled in. This animation shows the difference between some Messier 82 images I took last year in February versus the 2 exposures I managed to capture tonight.
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Last Updated on Friday, 09 February 2018 22:05 |
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