"Its anthem is the wind in her trees, and the waves on her seas." - J. Cadle
Q. What is the illustration at the top of this page?
A. It is "The Flag of Earth". We fly it at the Big Ear Radio Telescope, and it is flown at many other S.E.T.I. sites around the world. Follow the links if you're interested in learning more. . .
Q. Was there a universe BEFORE the Big Bang?
A. The definition of "universe" is, all there is. Assuming there was nothing before the Big Bang, then by definition, there was no universe.
Q. What or who made the Big Bang in the first place? And what or who made him or it? For example, if your answer was God , where did God come from?
A. I personally do not believe in "God". Science has shown (through a LOT of mathematical handwaving), how the universe began (it's a quantum mechanical thing). This is one of those areas where science isn't sure of its answer, in the question of what was around before the Big Bang occurred (in fact, the very nature of science mandates that we are ALWAYS unsure of our answers, but we are ALWAYS sure when we're wrong!). Also, keep in mind that the Big Bang is only one possibility for the inception of the universe. It currently happens to fit current observations, but astronomy (and science in general) has a long history of "the observations fitting the currently popular theory".
Q. What is beyond the edge of the universe? And what would happen if you went there?
A. Theoretically, there is no "beyond the edge of the universe". We believe the universe is a closed system. Imagine a sphere (say, the Earth or a beachball). It is not infinite, but you cannot find "the edge" since it is a "closed system" (which explains why the early sailors never fell off the edge of the world, as feared!). Also, see definition of universe above.
Q. If there are black holes at the center of most galaxies, then what's at the center of the universe?
A. Everything! If the universe is a closed system, any point can be the center.
Q. Recently, my brother brought home a Meade Dobsonian 6" telescope. I've always wanted a telescope because the one thing I always did first when I stepped out to the backyard was to look up at the sky and wonder what it would look like close-up. So I am very happy that my brother has taken an interest in Astronomy. After all I am an Aquarius and one of our career options is Astronomy itself. I use a wide angle lens to look at the star constellations and sometimes I want to take closer look at some areas where there should be some other objects. So I change the lens and I use a 2X barlow to magnify it. The thing is, I never get anything in view. I get the same thing when I focus. A bunch of points of lights and stars. I can never get a close up view of the objects. I get real frustrated because I have checked out some of the books on backyard astronomy where they keep saying how you can get a closer look at these things just through binoculars or a small telescope. Now I know that my telescope is good enough for me to see nebulae and other objects in the sky. Why don't they show up? I can see the stars fine but nothing else. The only thing that I DID get to see in the morning hours was MARS and that was fascinating. I know that at this time, the planets are out of range but I know that there are plenty of other things in the sky to see. So can you tell me what the secret is? I keep reading on how we can see all these things just by looking at them with the naked eye, but I don't see it. There's a bit of light pollution, but not that much. I can see the stars through the telescope just fine. I live in Phoenix, AZ.
A. Well, living in Arizona is certainly a plus! The main reason you're not seeing objects other than stars & planets is because you have to know *right* where to look. Deep sky objects (galaxies, nebulae, globular & open clusters, etc) are quite small and usually faint, so they're not obvious to the naked eye (with a rare few exceptions, such as M45 & M31). I recommend an observing aid called "AstroCards". These are sets of finder charts on index cards, grouped by sets. There's a set for the Messier objects, a set for the brighter NGC objects, a set for double stars, etc. Above all, be patient! The universe will always be there, and once you learn where the objects are, it'll start to seem less mysterious. Also, download the file "begin.zip" for more assistance.
Q. I would like to know: As of now, are there any _confirmed_ "black holes"? And if yes, what was the principal evidence that ruled out other possible explanations?
A. Yes, there are confirmed black holes. By observing how an object moves in space, you can deduce that there is a gravitational influence acting on something. You can also deduce how much gravitational influence is being exerted. If you observe something being gravitationally influenced by something very massive, but do not visually see anything that could be influencing it, then it must be a black hole! Astronomers have observed these effects at the center of galaxies, as well as around a few objects within our own galaxy.
Q. Many books on solar eclipses indicate that there were five in 1935. I believe there were only four. Can you verify this?
A. According to my copy of "Astronomy Lab" (written by Eric Bergman-Terrell, distributed by Personal MicroCosms, 8547 E. Arapahoe Rd., Suite J-147, Greenwood Village, Co 80112), there were four solar eclipses in 1935: On 2/ 3/1935, a partial, maximum magnitude = 0.74, visible in the northern hemisphere; On 6/30/1935, a partial, maximum magnitude = 0.33, visible in the northern hemisphere; On 7/30/1935, a partial, maximum magnitude = 0.24, visible in the southern hemisphere; And on 12/25/1935, an annular, visible in the southern hemisphere.
Q. I have a question regarding time: if time is a variable then can it assume the value of 0? And if so, what happens?
A. Yes & no. Generally, time must have a non-zero value, else we obliterate the principle of cause and effect. Time can have a zero value in a relative sense, if one is attempting to describe the coordinates of something in only 3 dimensions.
Q. Do you know if any of the stars that have been found to have planets orbiting them (51 Pegasi, 70 Vir, 47 Ursae Majoris, 55 rho Cancri (Hr3522), HD114762, Lalande 21185, tau Bootes (HR5185, HD120136), upsilon Andromedae (HR458,HD9826), or 16 Cygni B(HR7504) to be a Red Star?
A. There are 2 stars with reported planets that are "red":
Lalande 21185; M2 class; Abs. Mag. = 10.5; App. Mag. = 7; Temp. = 3600d K; Rel. Luminosity = 0.0016; Rel. Radius = 0.3; Distance (in pc) = 2.
Gliese 229; variable, M1/M2V class; Abs. Mag. = 9.0; App. Mag. = 7.3; Temp. = 3660d K; Rel. Radius = 0.8; Distance (in PC) = 28.
Most of this info is available on the web at the following addresses: http://www.princeton.edu; http://cannon.sfsu.edu; http://www.seds.org; http://zebu.uoregon.edu.
Q. I've been wondering what sort of education, training, ambition, etc., it takes for someone to become a radio astronomer. It seems like a neat profession, and I am also very interested in astronomy. Cool site, by the way!
A. To be a traditional radio astronomer, a lot of education is necessary at the college level. However, at the "Big Ear" Radio Telescope, no experience or "traditional" education is necessary! We are almost entirely staffed by volunteers whose only trait is ambition! It doesn't hurt to be well read on the subject though. I recommend Dr. Kraus' books. Also, see if there are any groups local to you that share your interest in radio astronomy. Perhaps there is a radio telescope near you that will allow an enthusiastic volunteer to participate in some of their projects. The very best way to get involved in anything is to learn as much as you can about the subject, and "just do it"! And, thanx for the cudos!
Q. Have a question regarding Hale Bopp & Earth's trajectory. . .With Bopp's dust trail being so long and passing reasonably close to Earth, is Earth's trajectory cutting through the dust cloud left in space from the comets passing?
A. Unfortunately, no. The angles are all wrong. This is, however, the cause of meteor showers; whenever the Earth passes through the dust particles left behind by a passing comet, we see a meteor shower. For example, the comet Swift-Tuttle is responsible for the Perseid meteor shower which occurs every August 12th.
Q. I´m a novice in astronomy, a chemical engineer who wants to go a little further. I really like astronomy and when I see a documentary on TV or read books I always think how wonderful must be to see the moon and so many other things in real life! My question is, I´d like to buy a telescope. Which kind do you recommend? Also, which software is quite easy to use and find the planets?
A. I recommend an 8" Dobsonian style reflector (available from http://www.telescopes.com/site_search/index.php?keywords=dobsonian&cat=17&brand=&display=&sort=&lp=&hp=). Download the file "begin.zip" from this site; it is a text file that explains in greater detail many of the aspects of astronomy, especially the different types of telescopes and where to get them. As for the software, look at the software section of this site.
Q. I was wondering if you may be able to assist me. I am trying to find a site on the web which gives me access to pictures etc on all of the planets in our solar system. I'm trying to teach my kids about the planets, how they line up, names, pictures etc. Any information you could give me would be greatly appreciated as I am having trouble finding anything on a fairly simple basis.
A. There is a lot of planetary info available at the following url's: http://pds.jpl.nasa.gov/planets/ & http://seds.lpl.arizona.edu/nineplanets/nineplanets.html. Of course, if you have specific questions that you cannot find answers to, I am always willing to answer them!
Q(1). Since nothing can escape from a black hole once it has traversed the event horizon, I presume black holes are always increasing their mass.
A(1). A good assumption, on the face of it. However, Hawking et al has shown that black holes "radiate"; see Hawking's "A Brief History Of Time" and his subsequent writings for more details.
Q(2). As a result, I also assume that the black hole's gravitational field will also increase thus consuming more and more material from regions increasingly distant to it. I find it hard to understand that galaxies are meant to have black holes at the core. Why don't the galaxies just get sucked in and will this be the fate of the universe.
A(2). There is evidence that black hole's masses do increase as they "eat" material. As far as "galaxies are meant to have black holes at the core"; "meant" would seem to infer interference by an intelligence. I believe that black holes form at the center of galaxies as a natural part of galactic evolution.
Have just found your home page so I'm afraid you may get deluged with my questions.
Deluge away! That's why I put the site up! :}
Q(1). I take it you are talking about Hawking radiation, if I remember correctly and in my own lay terms, matter can form out of "nothing" which gets split, some entering the black hole and some escapes, is it this matter antimatter stuff which I don't fully comprehend?
A(1). Yup. Essentially, "hawking radiation" works from the same principle that alpha radiation does, from a quantum mechanical standpoint, instead of at an atomic level tho'. It can be hard to explain is lay terms, but a good read of the subject by Hawking or Wheeler goes a long way.
Q(2). Ok, then does this mean that the ultimate fate of the galaxy is to be swallowed by the black hole at it's core? It's just that I can't imagine a scenario in which the incredible gravitational pull of these supermassive black holes will stop swallowing material until these is nothing left to swallow?!
A(2). Probably, unless something happens to stop it. What that something could be, I have no idea, but we cannot rule out such a possibility. Remember, the only absolute is, "there ain't no absolutes"!
It is logical that each galaxy w/a black hole at its core could eventually be entirely swallowed up by the black hole, but either 1) the universe isn't old enough for this to have happened yet; 2) it has happened many times (or at least once) and there's currently no way we simple humans can conceive a way to observe the "after effects" (if any); 3) it is happening right now somewhere in the universe and there's currently no way we simple humans can conceive a way to observe the event.
Q. My thirteen year old daughter has requested a telescope. Since this is the first request she's ever made in recent years for anything other than electronic games or game machines, and also since she is not at all academically oriented, I am anxious to find a solution if we can afford to do so. I've read your zip file and she hasn't done any of those things yet. On the other hand, her mother at least can identify stars and constellations and has some long held interest in astronomy. We (my wife and I, not my daughter) went to a meeting of the Spokane Astronomical Society and viewed Saturn through a 80mm refractor and found it very disappointing because all we saw was a tiny shiny disk/ellipse object, showing no gradations whatsoever and no space between the rings and the planet. Although this scope was on the outer edge of what we could consider spending ($300-$400) this was so disappointing that if this is all my daughter could see she would rapidly lose interest. Given that this is an interest we would like to nurture, what do you recommend ?
A. Since she will be easily disappointed w/scopes in the price range you mention, I would suggest she stick to looking at pictures off the net, I'm afraid. What you saw in the 'scope that night is the way the real world looks. The trick is to teach your daughter to not just glance at something and say "is that it?". She must be taught how to "observe", to pull detail from objects in the eyepiece; to be patient. This is how all knowledge has been obtained. She should be brought through the steps of becoming an observer; taught how to locate the constellations, get to know individual stars, etc.
If you are truly intent on getting an inexpensive scope (realizing that it sounds to me like she's just gonna lose interest soon anyway and the scope'll just collect dust, instead of photons), I suggest buying one of the 8" Coulter Dobsonian scopes; they're about $500.00 pre-built & shipped right to your door.
Q. What percentage of the physical universe can we see and hear with the visible eye and normal hearing?
A. A VERY tough (& GOOD) question! Current belief has it that we have not yet even catalogued ALL of the "physical universe". Therefore, the part we "see & hear" is a small percentage at best.
As for the "seeing" part, you must have some understandings & some basic assumptions to start from. . ASSUMING the Big Bang actually happened, then light has only had so far to travel since then (because light's speed is finite). We currently have the ability to see to the visible edge of the universe, but this DOES NOT mean we can see EVERYTHING in the universe! There are many things hidden from us due to (1)perspective (some things are behind others from our point of view), and (2)size; some things are just to darn small for us to see! Also, you have to decide what spectrum you want to "see" in. We have the ability to "look" in not just the visible part of the spectrum our human eyes have evolved to; we can "see" in radio (see below, "hearing" section), as well as microwave, gamma wave, x-wave, etc, etc.
As for the "hearing" part, sound requires a medium (such as air, water, etc) to propagate. Since there is no such medium in space, there is no sound. We DO however, have the ability to "listen" to the universe in radio waves, which are simply a tiny portion of the energy spectrum that our ears have evolved to handle. Listening at these frequencies, the universe sounds like an AM radio tuned off-station. In fact, if you tune an AM radio off-station, much of what you hear IS the universe! (depending on how close you are to terrestrial interference sources). It is because of this fact that radio astronomy was accidentally"discovered" by Karl M. Jansky. Be aware that "listening" in this sense is simply a matter of semantics; it is really the same as "looking" (above).
Hope this answers your questions. If not, email some more! :}
Q. How is a black hole created?
A. The same way as suns are created, in fact, a black hole is the result of stellar formation run amok. Gravity begins condensing material together, and the process just runs wild.
Q. Why can't I find out what happens inside a black hole? Dose it have something to do with escape velocity?
A. Kinda. No-one knows what goes on inside a black hole because we cannot put any recording/measuring devices inside one - they'd just get torn apart by the tremendous gravity there. We can speculate however, using gravitational calculations: inside a black hole, things just get ripped apart into a stream of their component subatomic particles.
Q. What is the Schwatrzchild radius, also known as the event horizon?
A. It is a spherical region surrounding a black hole that marks the "spot of no return"; cross the event horizon, and the gravitational pull from the black hole is so strong that you cannot escape it.
Q. What is a singularity, and what do they have to do with black holes?
A. A singularity is a weird beast; in order to explain it well, I'd have to get into quantum physics. . .
Q. What is the minimum mass for a black hole?
A. Theoretically, there is no minimum, but I believe practically there is. Hawking (et al) has mathematically demonstrated the possibility of pinhole sized black holes.
Q. I've heard this is called the Chandrasekhar limit (maximum mass) for a certain kind of star? As of yet, I have been unable to find the answer to the question I can understand. I have looked in several web sights and have only been fortunate in understanding part of the information.
A. The Chandrasekhar Limit is a calculation on the amount of mass that can be supported by electron pressure. You see, the more massive things get, the more they squeeze the center. After a certain point, the atoms at the center get torn apart into their constituent electrons. A big ball of these can support a lot of mass, but if the ball gets to be bigger than 1.4 solar masses, their own gravitational pressure will cause them to continue gravitational collapse until they form a black hole.
Q. I was also wondering were I might find information on the Laser Interferometer Gravity Observatory (LIGO) project built at Hanford In eastern Washington?
A. Here's a website to start from: http://www.geo600.uni-hannover.de/
Q. I am 13 years old in the Nashville area. I was wondering if it is possible to see a planet with a 402 powered telescope, if so do you think it is possible to distinguish if it has rings around it with the same powered telescope. I was looking in the southern sky last night and thought I seen a planet with rings. Also I would like to know where I would be able to find a beginners map of the constellations so I can know exactly where and what I am seeing. Thank you very much in advance for any assistance you are able to provide.
A. You are making a mistake common to astronomy, over-magnifying. you ALWAYS want to use the lowest passable magnification. Over magnifying anything with a telescope just makes the image "mushy". Remember, this is a TELESCOPE, not a MICROSCOPE. You want more magnification w/a microscope, NOT a telescope. A more important consideration in telescopes is focal ratio. In observing planets, you want a scope with a fairly large ratio, as opposed to say observing planetary nebulae, which can be pretty extended objects, in which case you'd want what's known as a "rich field" scope. For planetary observing, a scope w/a focal ratio of f/7 to f/14 is good, at about 35-50x. If you do not have your choice of scopes, just stick to eyepieces that produce a magnification of 35-50x. If you were looking at Saturn w/this setup, you would easily see the rings. Jupiter, Neptune & Uranus also have rings, but I have observed these planets with a scope as large as a 32" f/17 and not seen their rings, so the ONLY planet you will see rings around is Saturn. The other planets have their charms tho'; Jupiter has the Galilean moons as well as bands of color, Uranus & Neptune are beautifully colored (you tell me what colors they appear to you - they're not the same!).
As for the comment "I was looking in the southern sky". . .; we need more info, such as, what is your latitude & longitude? What direction were you observing (compass direction, with north being zero degrees), and what altitude was the object (the horizon is zero degrees; your fist at the end of your extended arm is about equal to 10 degrees); also, what time were you observing (& time zone)?
As for beginner's maps, an excellent book in general to learn the constellations is the one entitled "Star Maps For Beginners" (appropriately enough!), by Leavitt & Marshall. Your local library/book store should have it. There is no published book of maps for finding the planets however, because they move over time, so where a planet is this month is not where it'll be next month.
A good thing for you to do is to d/l one of the software programs from the software section.. Most all of 'em will tell you where the planets are after you configure the program so it knows where you are on Earth.
Q. First of all I wanted to congratulate you on your site. I am just starting out in Astronomy as an amateur, and your site has some great resources to point beginners in the right direction.
A. Thanx - feel free to take full advantage of it!
Q. Now my question: The current belief is that the universe is a closed system. Pictured in 3 dimensions it would be equivalent to saying that the universe is the surface of a beach ball whose radius has been increasing since the Big Bang. As you said, this means that there is no "center" of the universe. However, it is often said that we now have the ability to look to the "edge" of the universe. If the universe is indeed a closed system, wouldn't it have NO edges?
A. When it is said we can "see" to the "edge" of the universe, it is meant the VISIBLE edge, since light has a finite speed, it could only have gotten so far since the big bang. So what really should be said is 'we can see as far as light has made it since the beginning of the universe'.
Q. I know we can estimate the current size of the visible universe by calculating the distance that light could have traveled since the big bang, and that "seeing to the edge of the visible universe" means we can now see THAT far. However, it all depends how you measure the distance. Sticking to the beach ball concept, the ball has been growing in radius ever since the big bang. Thus, would the size of the visible universe be a beach ball of a radius equal to the distance that light has traveled since the Big Bang?
A. The size of the universe is really the age, so we can say the universe is, say, 17 billion light years old, the distance to the visible edge of the universe is 17 billion light years away.
Q. However, when we observe the universe we are NOT looking towards the center of the beach ball (since there is no universe there!). Instead, we are looking"along" the surface of the beach ball and the light would bend to follow the surface. Thus, there would be no edge!
A. Exactly.
Q. As a thought experiment, suppose we could see as far as the circumference of the beach ball (which,if we take the radius of the ball to be the size of the visible universe, would be a greater distance than what light has traveled since the Big Bang, so it is really impossible), we would still not see any edges - in fact, since the light we are observing has traveled around the circumference of the ball, wouldn't we be seeing the same spot where we are observing from?
A. No, but your question has been asked in various formats since humans were capable of this depth of thought. A good reading of Einstein, Hawking, Wheeler, & Feynman will go a long way to clear this up for you. Also, I feel you are at the stage where you should find a physics mentor for long discussions and hand-waving sessions.
Q. Could my confusion arise from trying to picture the universe in only three dimensions?
A. No. Your confusion is caused by not quite having all the information you need to complete your mental picture. See my above statement. . .
Q. I guess my main question boils down to "What is the 'edge' of the visible universe?" (It seems I could simplify after all :-)
A. The visible edge of the universe is simply the point at which light has traveled since the beginning of the universe. No more.
Q. I live in Belgium, and already know some things on how to become an astronomer. Since no university has it as a direct course, you have to follow math or physics. In one university math is the best way.
But here is the question: Is there still job perspective in astronomy? What is my degree worth in other countries? I know that most big telescopes are in exotic places, but can I also work for lets say America or even South Africa. Meaning that nationality and place where you got an degree doesn't matter and any astronomer can apply for any job in the world.
A. Following math or physics as a route to astronomy is not so bad, after all, it's the way all the GREAT astronomers went before modern times!
As for the relative worth of your degree in other countries, I can tell you it's not so much the degree as the degree-holder. You must be a very good observer, with excellent scientific skills. You must be patient. While you are studying for a degree, apply for research assistant positions. Once you have reached your degree, apply for observing positions until you get one.
Remember Humason, and learn from his example!
Q. I acquired a 4-1/2" reflector telescope for Christmas. I remember seeing the black spot on Jupiter when I was a kid. I remember the planet rotates on its axis every few hours. I have not seen the spot even after a multitude of observations. Is my telescope to week or did the spot go away.
A. The Great Red Spot on Jupiter should be just visible in your telescope, but timing your observation during the time it is facing Earth is the tricky bit! I advice subscribing to Sky & Tel magazine, which publishes a monthly chart of its apparitions, thus making it easy for you to see it quite frequently!
Q. I assume it is not just luck that the moon rotates on it's axis at the same rate that it orbits the earth. What is the explanation?
A. You're right! The moon has become "tidally locked" with the Earth, which means that, over a very long period of time, the gravitational forces interacting between these 2 bodies has caused the less massive one to present the same face to us. There is a little bit of "libration" though, and the careful observer will notice that slightly better than 50% of the moon's surface is available to observe over time from Earth.
Q. I often see low-earth-orbit satellites, but are geo-synchronous satellites visible? How about with binocs or a small telescope?
A. Geo-synchronous sat's are very difficult to spot, due to the fact that they do not move and are very faint. You have to know EXACTLY where to look! They are visible in a telescope tho', assuming the above! Of course, they're just gonna look like spots of light once you do find 'em anyway!
Q. How do amateur astronomers measure or estimate an object's magnitude?
A. To do reliable estimates, you must first practice. Pick a starfield that is fairly well populated with a good spread of stars from faint to bright (there are plenty such star fields along the band of the Milky Way); look up the field using a good starchart and learn the magnitudes of several stars, again making a spread. Then, by visually comparing the stars you DON'T know the mag's of, try to guess their mag by comparing them visually with the stars you do know. Compare your guesses with the chart to see how you did. I've known people that can guess to within a tenth of a magnitude w/a lot of practice!
Q. Thanks for being a resource to us beginners. Having someone sort through all the software out there, and answer questions that may not be addressed elsewhere, is invaluable to someone like me who's just starting out. Your website and your 'begin.txt' file both show a lot of careful thought, and I think they are great!
A. Thanx for the cudos!
Q. I recently purchased a Meade ETX-90EC (currently 30% off at Learningsmith!). The finder is sometimes very difficult to get behind, so I'd like to get a right-angle finder. Meade has one that fits the mounting brackets on the ETX-90EC for around $50. Should I consider another vendor such as Edmund Scientific? I'm a little squeamish about drilling holes in my new telescope to accommodate someone else's mounting rings. e-scopes (www.escopes.cc - is this site associated with Coulter Optical?) has an erect-image right-angle finder, but the price is $120.
A. Personally, I would never recommend drilling holes into a scope; ifsomething goes wrong. . .Look into Edmund's or the Orion catalogue, there's no reason you can't find a good right angle finder that will fit in the existing mounting rings.
Q. I'm also concerned about eye relief. I've been reading everything I can about telescope designs, but haven't seen much written about this topic. When I bought a nice pair of binoculars a few years ago, I got a pair with longer-than-usual eye relief since I wear glasses. My eyesight is good enough to observe without them (I only have astigmatism) but my eyes get tired more quickly that way. Can you tell me anything about eye relief as it applies to telescope eyepieces, particularly as a concern for those who wear glasses? What is the range I should be looking for - 10mm or more? Is it something I should look for in a finder, or just on the main telescope eyepiece?
A. Concerning eye relief, I take my glasses off and focus the instrument to my uncorrected eye. Then, your eye relief is much better, and you have 2 less surfaces to reflect light off of. . .I also got the rubber eyecups from Edmund's to put over my eyepieces, as this allows me to keep my eye at the correct distance from the eyepiece's lens and helps block out stray light. As for your eyes getting tired, this is because you haven't learned how to relax your eyes while observing. The trick is to learn how to completely relax your face muscles and try not to change the shape of your eye/lens by tensing up any muscles (familiarly known as squinting, etc). Just let your eye be open and make your instrument do the work by focussing it to your relaxed eye. This will take some practice, much like learning how to observe off-iris (using the side of your eyes), but it's worth the effort in the long run, for once you've learned how to relax your face muscles, you'll be able to observe all night w/o getting tired eyes!
Q. Finally, I know I'll eventually invest in several more eyepieces. I'd like to get at least one with a wider field of view than the 28mm Super Plossl that came with the ETX-90. I'd like to consider others with more magnification, too. Do you have any suggestions for trading off field of view for magnification? Edmund has a set of 4 RKE eyepieces that look like a good deal. I've also seen several 'zoom' eyepieces, that would presumably take the place of several fixed eyepieces. What is your opinion of using a single zoom eyepiece instead of individual eyepieces?
A. I don't like the 'zoom' eyepieces at all. I usually recommend the Edmund's RKE series for several reasons; parfocal (important to me!), good quality, good eye relief, good FOV, good price (also important to me!). Regarding magnification, remember that this is a TELEscope, not a MICROscope; magnification is not as important. In fact, too much magnification can actually be detrimental to good observing. If you feel it necessary however, get a good quality barlow lens. I got mine from the Orion catalogue.
My 11 year old is doing some homework on astronomy and here are the words that we CAN'T find a definition for:
Q. Barred spiral galaxy
A. A sub-classification of galaxies; look for Hubble's Classifications; our galaxy is thought to be a barred spiral galaxy. See http://zebu.uoregon.edu/~js/ast123/lectures/lec13.htmlQ. Irregular galaxy
A. A sub-classification of galaxies; look for Hubble's Classifications, the Magellanic clouds are examples. See http://zebu.uoregon.edu/~Js/ast123/lectures/lec13.htmlQ. Local Group
A. The group of galaxies our galaxy belongs to; a group of galaxies bound together by gravity moving through space in (roughly) the same direction & velocity. See http://www.airdigital.com/Local_cluster_plot.htmQ. Star cluster
A. A group of stars all born at roughly the same time from the same cloud of hydrogen & dust. Look for "Open cluster or Stellar cluster" (the Pleiades is a good example), See http://uregina.ca/~astro/ast202/notes/week2/cluster/sld001.htm or "Globular cluster" (M13 is a good example). See http://uregina.ca/~astro/ast202/notes/week2/cluster/sld004.htmQ. Axis of rotation (How a planet spins?)
A. One of the properties of electrons, planets, moons, asteroids, etc. Describes how the object spins. See http://www.racquetresearch.com/axis_of_rotation.htm for a general description.Q. Large and small Magellanic clouds
A. 2 nearby galaxies visible from Earth's southern hemisphere; also members of the local group. See http://www.seds.org/messier/irre.htmlQ. Ursa major (Is this the BIG Dipper?)
A. Ursa Major is the constellation that the Big Dipper is a part of. The Big Dipper as is commonly known is not a constellation per se, but an "asterism". See http://www.dibonsmith.com/uma_con.htm & http://www.dibonsmith.com/constel.htmQ. It's been a long time since I have been around this stuff, I and my wife have searched the web, but we ain't havin too much luck. It would be great if there is a place where I can look these up in a Astronomy Dictionary... is there such a thing?
A. Turns out there is! See http://www.users.skynet.be/sky03361/dictionary/dictionary.html & http://www.fitzroydearborn.com/dicastron.htm & http://www.kidsastronomy.com/dictionary.htm & http://www.starshine.com/frankn/Astronomy/AstroDictionary.asp & http://www.angelfire.com/ky/astronomy/glossary.html. For a master list of astronomy dictionaries goto http://google.yahoo.com/bin/query?p=%22astronomy+dictionary%22&hc=0&hs=0
Q. What does Roche limit mean? Where can I find out more about it?
A(1). From http://www.treasure-troves.com/physics/RocheLimit.html:
The Roche limit is the orbital distance at which a satellite with no tensile strength (a "liquid" satellite) will begin to be tidally torn apart by the body it is orbiting. A real satellite can pass well within its Roche limit before being torn apart.
A(2). From http://curriculum.calstatela.edu/courses/builders/lessons/less/les1/roche.html:
Roche's Limit gives us a formula that tells us how close the satellite will be when gravitational forces start to pull it apart. You can have rings inside this limit, but not moons. Be sure to locate your moons outside Roche's Limit. If the moon and the planet have the same densities, the limit is at about 2.45 of the planet's radius, measuring from the center of the planet to the center of the moon. If the densities are different, this number changes, too.
A(3). From http://www.cvc.org/astronomy/roche_limit.htm:
Roche's Limit is the distance from a planet inside which a satellite will be torn apart by tidal forces. EXAMPLE: For example, consider the rings of Saturn. All of the ring systems are inside Roche's Limit, which is the distance from a planet at which the planet's tidal force on a satellite (force that stretches apart) is equal to the satellite's self-gravity (force that holds it together). Satellites closer than Roche's limit will experience stronger tidal force, and since the self-gravity is the same regardless of distance from the planet, tidal force will dominate, and keep an object from forming, or break an already-formed object held together by self- gravity into fragments. Roche's limit, if both planet and satellite have the same density, is 2.45 planetary radii. The comparison is with the strength of self-gravity in holding the satellite together. Smaller rocks are held together by crystalline forces in the solid. Such forces are far stronger than self-gravity, and prevent them from being broken up.
Q. Dear Mr. Astronomer, Why do comets keep shooting?
A. Well, I'm not certain what you mean by "shooting", but the reason we keep observing comets is because there is a LARGE repository of them a long way from the Earth & Sun called the "Oort Cloud". This repository is thought to be left over material from the formation of the Solar System. Occasionally one of them gets "bumped" and due to gravity falls in towards the Sun; when this happens we can observe them when they get bright/close enough. Also many comets are in small enough orbit around the Sun that we re-observe them periodically.
Q. What makes them move?
A. Primarily gravity; the same reason you fall down when you trip on something. The Sun is the largest gravitational body in our Solar System, and it pulls things like comets in towards it.
Q. Why don't they stop?
A. Sometimes they do; a good example happened a few years ago when comet Levy-Shoemaker broke up and smashed into Jupiter. Comets also just "dry up" over time; everytime they pass near the Sun, they lose material (you see this material loss as the 'tail' of a comet). If the comet passes often enough past the Sun it'll eventually use up all it's material and simply disappear. Also lots of times comets come so close to the Sun that the actually burn up completely.
Q. I recently visited the Lowell Observatory at Flagstaff, AZ and actually got to look through the telescope they discovered Pluto with! Can you tell me a little more?
A. A VERY cool place you were at! I've been there myself; the whole grounds is neat!
Here's a good website with an article on the discovery of Pluto: http://www.discoveryofpluto.com/ .
As for the telescope, Pluto wasn't actually "discovered" at a telescope; rather, series of photographic plates were taken of overlapping sky regions where it was postulated that another planet should be (based on mathematical models due to perturbations on Neptune's orbit), and Tombaugh (http://www.oarval.org/tombaughen.htm) spent a LONG time "blinking" the plates in a comparator (an apparatus that rapidly causes 2 images to blink back & forth, thus making any differences stand out (http://en.wikipedia.org/wiki/Blink_comparator)) until eventually something popped out.
Then, further observations were made & the planet's existence was confirmed, then models were developed based on positional observations that revealed it's orbital path, which led them to believe that indeed Pluto was responsible for the perturbations in Neptune's orbit.
An interesting side note is that if the astronomers at the time had been a bit more unbiased they would have realized that Pluto alone does not account for all the perturbation in Neptune or it's moons. This was later discovered (mathematically), and a search for other planets ensued.
Once ground based telescopes got better, and with the launch of space based telescopes, many hundreds of objects have been discovered in orbits beyond Pluto's (and sometimes crossing Pluto's orbit). It is now thought that the combined gravitational tugs of all these objects account for Neptune's perturbations. We'll see. Recently Pluto has been reclassified as no longer being a planet but instead is now officially considered to be in the same class of objects as the others since discovered, collectively known as inner Oort cloud objects, inner kuiper belt objects, trans-neptunian objects, or sometimes proto-cometary matter (http://solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs&Display=OverviewLong)).
Q. Written by a physicist about practical interstellar travel. Worth reading when you have some free time: http://strangepaths.com/interstellar-ark/2007/02/14/en/
A. Yeah, there's a lot of crackpot theorists out there; while this fellow references Einstein's equations, he completely ignores the "meat" of it, which is essentially that an infinite amount of energy (mass) is required to push anything over the relativistic boundary (or even to approach it, for that matter (pun intended!)). Since this physical requirement results in essentially a "vicious circle", one can easily understand why it is physically impossible for matter to approach/go beyond the "speed limit" revealed/imposed by the equation(s). This fellow, and others reading his "work" would do well to engage in a serious study of physics from a more elementary level first, then hold some serious discussions with a college level physics professor.