Almost everyone who is familiar with space images has seen this beautiful and color emission and reflection nebula – but take a really close look. This isn’t a Hubble image. It was done with a ground based camera!
When looking at M20 through a telescope, what you will see won’t match the photo above, while what is normally presented in science journals is colorful. Why? Well, when it comes to photographs, exposure times and wavelengths causes the different colors you see. Photographically, the red emission nebula contained within Messier 20 has a bright blue star cluster in it central portion. It glows red because the ultraviolet light of the stars ionizes the hydrogen gas, which then recombines and emits the characteristic red hydrogen-alpha light captured on film. Further away, the radiation from these hot, young stars becomes too weak to ionize the hydrogen. Now the gas and dust glows blue by reflection!
Of course, there are other ways of looking at Messier objects, too. It was my great fortune on Saturday night to have an opportunity to study M20 through an image intensifier – a highly complex piece of equipment which uses x-rays and produces a ‘live’ image feed which is displayed on a binocular like eyepiece screen. I cannot even begin to describe to you what this does to observing, except to say that it opens a dimension to to eyes never before experienced. No matter how it is observed, the Trifid – or “three lobed” nebula has a distinctive set of dark dust lanes which divide it. These also have a classification of their own and were cataloged by E.E. Barnard as dark nebula Barnard 85 (B 85).
In 1999 the Hubble Space Telescope took this photograph – a look deep into the Trifid nebula at some of its star forming regions and found a stellar jet poking its way into the cloud, like a fabulous twisted antenna. Inside the exhaust column is a new star waiting to be born, yet sometime over the next 10,000 years the central massive star will probably erode away all of its material before it can fully form. Nearby a stalk stands waiting… Like the jet, it is also a stellar nursery – one with an EGG (evaporating gaseous globule) at its tip – a condensed cloud of gas able to survive so far. “If our interpretation is correct, the microjet may be the last gasp from a star that was cut off from its supply lines 100,000 years ago.” says Jeff Hester of the Department of Physics & Astronomy, “The vast majority of stars like our sun form not in isolation, but in the neighborhood of massive, powerful stars. HST observations of the Trifid Nebula provide a window on the nature of star formation in the vicinity of massive stars, as well as a spectacular snapshot of the “ecology” from which stars like our sun emerge.”
But, is it possible for those of us here on the ground to perform our own deep studies of regions of space like the Trifid Nebula? The answer is yes. Take a look at this small frame clipped from the full sized image you see above. While the colors haven’t been processed the same, those EGGs are there!
It’s a cinch that those of us that don’t have a multitude of titles behind our names are ever going to be allowed Hubble time… even at this late stage of the game. You know our findings will never be placed in the hallowed journals of science. But, why should the scientists be allowed to have all the fun? While images like Eddie’s might be considered “amateur”, it is anything but. While he’s chosen to reveal it in an artistic format, you must stop to think about how much information has been collected inside of his raw data. Unlike a simple film photograph, CCD imaging gathers huge amounts of information that’s processed out by what data is desired. “Velocity maps of the inner regions of the bright H II regions NGC 6514 were made with unprecedented spatial and spectral resolution in the 5007 A line of forbidden O III. In addition to the advantages of an instrumental full width at half-maximum intensity of only 5.4 km/s, the small thermal width of the heavy oxygen ion also allows determination of accurate line widths and velocities.” says C.R. O’Dell (et al), “The CCD spectra were numerically fitted to Gaussian line profiles and revealed two separate velocity systems in NGC 6523. The data sets of radial velocities were used to derive the dependence of the most probable turbulent velocities upon the sample sizes, and the spatial dependence of the structure function. These relationships are the basic functions for comparison with the predictions of the models for turbulence in H II regions.”
To me, one of the most fascinating aspects of Mr. Trimarchi’s picture wasn’t so much the huge revelation of all the Herbig-Haro objects – but a tiny, fine detail that you probably took for granted when you looked at it. Dust extinction… There’s a lot of very exiting things in that photograph, but there’s a detail he left in there that most other photographers filter out! The studies of C.R. O’Dell taught me to take a much closer look a certain properties in astrophotos, because I might see something that others missed, and in this case its a huge amount of dust extinction which he proved to exist around M20 many, many years ago. (Like back when my telescopes still had training wheels.)
Why are things like that important? In this circumstance, knowing there was more dust there than should have been lead to further investigations – and those in turn led to a discovery: “We report the discovery of a new candidate barrel-shaped supernova remnant (SNR) lying adjacent to M20 and two shell-type features to the north and east of SNR W28.” says F. Yusef-Zadeh (et al), ” Future observations should clarify whether the nonthermal shell fragment is either part of W20 or yet another previously unidentified shell-type SNR.”
Keep those cameras rolling… Who knows what we may find tomorrow?
Many thanks to Eddie Trimarchi of Southern Galactic for sharing this wonderul image with us!