You know that the summer is gone and winter is not too far off when the Orion constellation once more adorns our night sky in all its glory. If you want a friend, acquaintance or even your six-year old son to become enraptured with backyard astronomy, there are four things you should show him through your telescope - the Moon, Jupiter, Saturn and, the crowning jewel of them all - the Orion Nebula.
Even the non-astronomer will probably be able to spot the famous line of three stars pictured below, known as Orion's Belt. Just below that 'belt' is another line of stars - Orion's Sword, and the Orion Nebula is right in the middle of that 'sword'.
'Just' 1,300 light years away from us, the Orion Nebula is the closest nebula to us, and the brightest, so it can be seen with the naked eye. What you'll probably see is pictured below - a tenuous, but clearly visible, hazy patch of light. a few rather bright stars. These stars are what illuminates the clouds of dust and gases of the nebula, which otherwise would not be visible at all. The brightest of these stars are Theta–1 and Theta–2.
With a telescope, though, and in good observing conditions, you will be able to see the full extent of the nebula and perhaps even glimpse it's greenish blue hue, perhaps even a reddish tint.
However, you will need either time-lapse or long exposure photography to view the nebula in all its colour and glory. The picture at the top of this article was produced using afocal photography, viz. a camera attached by adapters and T-Rings to a 26mm eyepiece on the telescope and operated remotely by computer. I took 24 exposures, with each exposure lasting 3 seconds (to minimize the star-trailing), and the 24 images were then 'stacked' together
in black and white, as in the picture below, you can see that the contrast improves and one can actually make out the areas of swirling black clouds of nebular gas.
in black and white, as in the picture below, you can see that the contrast improves and one can actually make out the areas of swirling black clouds of nebular gas.
The nebula is a vast, cold cloud of gases and dust that does not emit light and is composed mainly of hydrogen (91%), helium (9%), carbon (0.05%), oxygen (0.02%), and nitrogen (0.02%), as well as smaller quantities of sulphur, neon, chlorine, argon, and fluorine. The gases and dust reflect the light of the nearby stars, but in the vicinity of the hot young stars the gases in the nebula are excited by the ultraviolet light emitted by these stars and so emit their own light. Although the nebula may appear tenuous and transparent, this 'clouds' actually contains the matter of 10,000 Sun-like stars! It is from such 'clouds' that stars like our sun and even planets like ours are 'born' and the Orion Nebula has revealed much to astronomers about the process of how starsand planetary systems are formed from collapsing clouds of gas and dust.
All photographs on this page © Sabri Zain 2012.
All photographs on this page © Sabri Zain 2012.
Thank you for the info! Question..If we took a picture of the Orion Nebula today and then take another picture 100 years in the future using the exact same camera (telescope & filters), would we be able to see significant movement in the Nebula? Or would it appear to not have moved much? Thanks again!!
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Adam, over the next few million years much of Orion's dust will be slowly destroyed by the stars now being formed in its 'nursery', or dispersed into the Galaxy, so it would probably look quite different then (and perhaps a little less spectacular). But a hundred years is less than a very tiny fraction of the blink of an eye in celestial terms, so it is probably unlikely that you'll see any significant change with an amateur telescope in a hundred-year period period. However, if you had a more powerful telescope in your back garden - like the Hubble or Herschel-Spitzer Space Telescopes, for example! - you could probably see a discernible change in the stars rapidly heating up and cooling down within a matter of weeks as they mature from being star embryos to become full-fledged stars. This was exactly what astronomers observing with the Herschel-Spitzer Space Telescope observed last February when they noticed that several young stars varying in their brightness by more than 20 percent over just a few weeks.
DeleteThe Nebula would also have moved ever so slightly in a hundred years with respect to its location in the sky as observed from the Earth. This shifting of position is due to the precession of the equinoxes, or axial precession. The rotational axis of the Earth is tilted with respect to the normal to the plane of the ecliptic, presently at an angle of about 23.5°. That is, it doesn't stand up straight but leans over a bit. Because of the oblate shape of the Earth and the tilt, the Sun exerts a gravitational pull that differs in force at the two poles. The effect is to attempt to set the Earth up straight - i.e., to try to right the axis to be normal to the ecliptic. The "righting force" has the effect of causing the rotational axis to execute a circular, wobbling motion, like a spinning top. The North Celestial Pole of the Earth will not always be point towards the same starfield as a result. It's this that will cause the celestial pole to move away from Polaris after the 21st century, passing close by Vega by about the 41st century. However, changes of star positions over a 100-year period are too small to be noticed with only the naked eye, though you might want to update your star maps or GO-TO telescope software!
Wonderful! Thank you for the response. With respect to the gas and dust formations, (like a cloud in our sky here on Earth)...Using Hubble or the Herschel-Spitzer do you think the gas pattern would look much different? For example, if I can see an image of an eye in the Nebula, will the gas and dust swirl enough relative to us to change shape in 100-500 years. I have a feeling that we would not be able to notice much difference in the gas pattern as well. This seems basic, but it's really bothering me.
DeleteI really appreciate your help and thank you for your time! -Adam
Yes, Adam, it's not likely one would be able to notice much difference in the gas pattern in 100-500 years. Yes, you can see clouds on earth change shape slowly but there are two huge differences between clouds on earth and the 'clouds' in the Orion Nebula - the Orion Nebula is 70,000,000,000,000 miles across and 80,000,000,000,000,000 miles away! You might think that seeing any change in something so mind-bogglingly huge and so unimaginably far within a 'brief' period of a few hundred years is quite unlikely. However, the expansion of the (albeit much smaller) Cat's Eye Nebula is quite discernible when you compare Hubble images taken in 1994, 1997, 2000, and 2002. The violent birth of the Crab Nebula was witnessed by astronomers 'just a thousand years ago, and the nebula is still expanding at a rate of over 1,000 kilometers per second. Comparing images of the Crab Nebula made nearly 30 years apart, you can clearly see the expansion. The Orion Nebula has many local phenomena such contracting cloud fragments, protostars, and newborn stars where space telescopes such as Hubble could record changes over relatively short periods of time. However, it's not likely you'll be able to spot those in, say, a 200mm SCT at home ;)
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