View Full Version here: : J,k (1,1) (2,2) ????
25-08-2011, 10:22 PM
Haven't posted in this section of the ice in space forum yet, and apologies in advance as my only other thread was about a question I had as well. Anyway, I'm returning to study next year to study astronomy and have been trying to get a head start. Hopefully after that I will be able to assist others who are in a similar situation to myself at the moment! Being an amateur astronomer for quite some time, I have a decent understanding of general astronomy theory, however spectroscopy/radio astronomy have always been my most neglected areas!
My question is related to the terminology used with what seems to be involved with transitions! I understand the basics of spectra, however more advanced texts tend to mention J and K and always have bracketed numbers next to them eg J, K (1,1) or (1,3) etc. Its hard to find any information that bridges the gap between a general astronomy spectra that talks about basics and more advanced texts. So my problem being is that basic texts avoid going this deep, and advanced texts seem to assume that the reader understands what J and K equal, and what the numbers relate to (I've got a fair idea, but a solid answer would be great).
Could anyone please explain this, or please suggest an appropriate resource so I could understand this aspect of spectra science?
Thanks in advance.
26-08-2011, 01:52 AM
The J and K bands are bandwidths within the IR spectrum that correspond to around 1.1-1.4 and 2.0-2.4 microns in wavelength, respectively. The H band at 1.5-1.8 microns is also important as well. They're most commonly mentioned in solar astronomy as they denote the wavelengths at which lines of CaII (singly ionised Calcium) are found in the solar spectrum. You can also tell by the strength of these lines just where in the spectral classes of F, G and K, a star resides. The cooler the star, the stronger the lines...although they peak around G3-5. You can also get other molecules and elements appear in these bands as well, such as K, Fe, CO, Mn and others. What also appears in these IR bands is dependent on luminosity class as well, with supergiants, giants and main sequence stars all having somewhat different spectra for any given spectral class.
As for a good text, grab a hold of "Stellar Spectral Classification", By Rick Gray and Chris Corbally. You can pick it up at Fishpond.com (http://www.fishpond.com.au/Books/Stellar-Spectral-Classification-Richard-O-Gray-Christopher-J-Corbally/9780691125114?cf=3&rid=88868435&i=15&keywords=Astrophysics).
I'll fill you in on more tomorrow....it's getting late!!! (2am). Need some sleep:)
26-08-2011, 04:58 PM
I have a question for you, if you don't mind...
I'm thinking strongly of studying astronomy formally to get a degree, and like you, I'm based in Melbourne.
I've been trying to find a good place to approach as a mature student, and I'm a bit snookered with limited options that I can see. Right now, my best alternative is a UK uni with an excellent international/online course, with options to replace pure and applied maths (which I suck at) with physics instead.
Locally, I know Monash has a dedicated Astro group, and that's probably my preferred option, but I was wondering how you went about choosing the best place, and where you ended up going? Obviously, our needs are probably very different, but any help would be very much appreciated!
Pete from Yarra Glen
27-08-2011, 11:43 AM
Thanks Carl for your answer, straight to the rescue once again :thumbsup:
Hi Pete, more than happy to let you know about the options I found, this also gives me a small chance to contribute to the forum, rather than taking, as I have a short history of doing so!
Being in Melbourne, as an on campus student, you have the option of Monash or Melbourne Uni. Swinburne has postgraduate research options, but not for undergraduate degrees. I know that other uni's run the odd astronomy unit for their physics majors, but as electives (if I'm wrong please inform me). You can also do an astronomy major at Monash or Melbourne as long as you have a degree, but its known as a postgraduate diploma and since my undergraduate degree was not in science, this means that I have loads of required units to do before I take the astro ones. If you have time these options would be ideal as you get tutorials and prac classes and face to face communication with your teachers! I dont have the option for this as my bills outweigh what I would get from Austudy etc. That leaves off-campus study as my option.
The two of these options that I investigated were Swinburne astronomy online, which offer up to Masters by coursework. I noticed that there are people on this site that are doing or have completed degrees and seemed to enjoy it. The other option is JCU, which offer the same as Swinburne, but with a research component and go all the way up to PhD. I'm going for JCU as it gives me that option of going "all the way" if I want to. Friends of mine who have done on-campus astronomy research have mentioned that several areas are not lab based, and more computer based (modeling, analysing spectra data etc), so I assume that these areas could be done at the research area off-campus.
Never-the-less, I'm starting with a garduate certificate. If it doesn'e kill my love for astronomy with the added stress that academic life brings, then I'll continue. Either way, I'll keep you posted along the way.
Hope that helps and good luck. Looks like we are both in the same boat!
27-08-2011, 12:36 PM
Ralph, thank you so much for the excellent explanation, that helps me hugely! Especially the clarification about undergraduate vs. post-graduate degrees. (I actually started an EE degree at RMIT in the 80's as a mature student, but a motorcycle accident put an end to that... so I never learned about all the pre- and post-graduate requirements!)
I think we *are* in the same boat - I'm also looking to go "all the way" if it's at all possible. And, to grab my metaphorical oar, I'm also really keen to see if I'm truly capable of retaining my passion and focus during a formal learning commitment.
I'll have a good look at JCU and see if what they offer will be workable for my situation. I really hope so, despite my maths delinquency.
Thanks so much, and I'll also post a quick update when I've learned more.
Cheers mate, and best of luck with your studies!
11-09-2011, 09:23 AM
I'm a late comer to this discussion but would like to add my two pennies worth.
I looked into these online astromomy degree courses when they first started (ten years or so ago?), and again recently, and came to the same conclusion ... can't see the point in them, not worth the money and their main purpose appears to be just an income source for the provider. Apart from the dubious 'satisfacton' of holding an astronomy degree I've yet to find any useful value in the award. If someone wants to be a real professional astronomer the only way to have any chance of being offered employment, which is pretty slim even with all the right degrees, is to do the hard slog and earn a real PhD in physics (not 'astronomy') from a well regarded institution ... generalist degrees don't appear to carry any weight or be of any value in the hard to enter professional astronomy world ... where a deep knowledge of maths and physics are the essential tools of the trade.
If a person's interest is just self-improvement and/or an amateur interest in astromomy then I think the large amount of money that needs to be spent to obtain an online astronomy degree is more productively invested in the best quality range of astro gear and books. If a person lacks the self discipline to teach themselves what they need to know then they probably lack the one crucial quality needed to carry out research.
From my own experience ... collaborating with professional astronomers by providing them with photometric and spectroscopic data over the last fifteen years ... there is plenty of work to be done by amateur astronomers, especially in the southern hemisphere, if they have the interest and equipment (not necessarily very expensive). While I do have a dark site observatory I am currently doing valuable spectroscopy for the pros from a portable telescope system near the centre of Melbourne.
So, I'm clearly biased against these online astronomy degrees and strongly in favour of spending the money saved on equipment and books.
11-09-2011, 10:59 AM
Thanks so much for sharing your point of view, Bernard (pun intended! :lol:)
I couldn't agree more with the point you make about cost - most of the universities seem to view online courses as just another revenue stream. Why should someone pay $23k per year as a remote student, when they have limited access to the resources that physically present students have full access to?
My perspective is as a physically disabled 48-year-old ex-electronics guru (GURU = Good Understanding, Relatively Useless :)) with limited physical access to even getting out in the hills around home to lug my manual EQ and point my 4.5" Newt at the stars, let alone spend significant amounts of cash for the kind of quality equipment needed to do proper astrophotography. So I'm a kind of corner case, if you like...
Everything I know about the cosmos I've taught myself, from first principles. I wanted to understand celestial mechanics, so I bought a book on that subject; then I found I needed calculus. So I bought myself a Year-12 calculus text, and found I didn't understand properly, so I bought an english translation of The Principia... Then I was having trouble understanding the geometrical allegories, so I bought Euclid's Geometry, and then... well, I just worked my way back up. Unfortunately, I found my mathematical limitations were just too severe to allow further learning without outside help.
Hence the search for an astronomy-based degree, rather than pure or applied physics - I'm just not wired for the heaviest kind of maths needed.
I don't want a job as an astronomer (that ship has well and truly sailed!), but I do want to understand at least as much as I know I'm capable of, and that means I may have to get a less-than-well-regarded degree.
THat way, I can enter into discussions and help other folks find out more about the wonderful reality we're in, and be taken (more or less) seriously.
If I can talk to the folks at Coonabarabran, or provide information to professional astronomers, then so much the better. But that's not my primary focus (again, pun intended! :lol:)....
This is a really interesting discussion. I hope others decide to chip in.. although we may need to make a formal thread so we don't keep hijacking this one!
11-09-2011, 04:55 PM
I'm not sure I agree with Bernard on this one.
I did the Master at UWS in the second intake. Maybe the price has changed but I think it was about $1800/ year when I did it. The reason that each person in the group did the degree was quite varied. Mine was for education sake only. I don't think I would have been able to teach myself how to reduce and analyse radio data and produce a published paper without the degree.
One person in the group was a naval officer. He needed a higher degree to get a promotion and the astro degree fitted the criteria.
At least 1 member has gone on to study a PhD and is working at the AAO. (Warren Reid)
It can be a stepping stone or just for interest as I did.
12-09-2011, 12:47 AM
I know of at least 4 of my group than have gone onto doing a PhD, starting this year, and I suspect a couple more will do so in the future. Before I do anything of the sort, I want to get a bit of cash under my belt so I'll be looking at lecturing at one or more of the colleges in the U.S. and/or looking at an assistant lecturer's/tutor's position at one of the unis. That way, if I finally decide to go further at least I'll have a foot in the door and some money to back myself up. I like teaching people, anyway, so I might decide to stay in there and do some professional research work every now and then. Less stressful than full time teaching AND research at the same time. Good thing with colleges is that you don't need a PhD to get your foot in the door. To teach astronomy, all you need is a masters in astronomy/astrophysics, physics or maths. Same goes for all academic subjects...masters degrees to start teaching. The colleges usually teach the equivalent of the first two (sometimes three) years of an uni course for the academic subjects, especially in the sciences. Allows the students to get part of their final degrees close to home before committing to go to a larger university further from home. They're like a cross between a TAFE college and a full blown uni. Good idea, if you ask me.
The problem with the "hard slog" approach that Bernard espoused there is that, in reality, all it ever produces is physicists...not astronomers. There is a difference. Although physics is a very big part of astronomer and a reasonable grounding in it is needed, it's not the be all and end all of astronomy. There are other paths that you can take getting into the various fields within astronomy as a whole that don't require a "Neil Turok" or "Ed Witten" level of understanding in physics and/or maths. In other words, a deep level of understanding of either physics or maths. But like I said, it helps to have a reasonable grounding in those subjects. Cosmologists and stellar astrophysicists/helioseismologists need the physics and the maths, but astrobiologists, astrochemists and planetary geologists/exoplanetary astronomers not so much. Theorists (mostly physicists, really) more so than observational astronomers. Archaeoastronomers and planetarium lecturers/curators even less so. You have quite a few options and even teaching itself is very rewarding, without having to do pure research. It's far more open to possibilities than just your bread and butter physics/maths option.
Not much going in Oz for astronomers, of any degree, unless you're lucky to get into one of the obs (like the AAO)
The maths components of these courses are woefully inadequate. Professional astronomy is more maths than anything. Without a thorough grounding in advanced mathematics and an ability to compute and reduce at the highest levels, you can never even pretend to be a "real" astronomer. Like it or not, it's a fact. Most graduates of these courses have what some refer to disparagingly as "Omni" or "New Scientist" educations: They can blather on like an expert about astronomical topics at a populist-level but, as soon as any mathematical ability is required, their whole shtick falls apart.
There are no shortcuts to the big league.
12-09-2011, 02:22 PM
So what is a "real" astronomer?
My professional field is medicine. So what makes a "real" doctor? Is it only the sub specialist surgeons or are generalist "real" Drs as well.
There are different roles as professional astronomers not all of which need Fields medals in maths.
12-09-2011, 06:03 PM
Some have no intention of wanting to duke it out with the big boys, so they don't need that level of maths. You'll find that most people who end up doing astronomy have come from a maths/physics background in their undergrad course and have only touched on astronomical subjects in graduate school. They could've used their undergrad degree for any science based career, if they so chose. Even quite a few outside of science. Despite the content of such courses, they're relatively generalist in their application. That's why we have graduate courses. A course is only as well regarded as the quality of the graduates that are matriculated and the teaching standards of the faculty/department running those courses. Even so, calling such courses as mentioned "Omni" or "New Scientist" is just elitist and very disparaging. Just a case of looking down one's nose at the students who don't do the "traditional" thing. Yes, some are generalist and not heavily maths based, but some others aren't. Many of the people who graduate from these courses never intended to go onto PhD's, but some have and now they have careers as astronomers. Some may decide to stay as masters and teach at colleges, and not every lecturer I've encountered at uni has had a PhD. Quite a few have only had masters degrees. Not even all astronomers have PhD's. Others may go onto teaching at high school, whilst some may go into industry, or even the military in some countries (especially the US).
Astronomy is like any other field of science these days....it's become highly specialised in any number of related fields within the subject and some require a better handle on maths than others. So, given the diversity of fields within the subject as a whole, what would you define as being a "real" astronomer????. You can say the same about any science. Physics, especially.
Put it another way....what is the strictest definition of an astronomer. One who studies the stars, am I not right??. If so, then anyone at this site, no matter their levels of knowledge, can be classed as an astronomer. And I can tell you now that there are quite a few "amateur" astronomers that have a much better knowledge of the night sky than many of the so called "professional" astronomers that grace the halls of the unis and observatories around the world. The only difference between the two is the level of specialised education (or more precisely, the little piece of paper in the photo frame on the wall) and the pay packet.
14-09-2011, 10:47 AM
I concur whole-hearteadly with this view … usually PhD eligibility in Theoretical Physics, is directly related to the achievement of honours level mastery in applied mathematics. If one doesn't achieve this level of academic prowess, PhD level qualifications won't ever be offered as an option.
A lack of experience in mathematical training during undergraduate courses, will virtually guarantee a shallower understanding of the AstroPhysical aspects which one is almost immediately confronted with, in Astronomy, or virtually any of the Physics related sciences.
Its unfortunate, but even an appreciation of this view, in itself, requires exposure to a comparatively sophisticated level of achievement in pure and applied mathematics.
There are no shortcuts to achieving deeper understanding in this field.
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