Astronomy Definition and 832 Threads

Astronomy (from Greek: ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates outside Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole.Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonians, Greeks, Indians, Egyptians, Chinese, Maya, and many ancient indigenous peoples of the Americas. In the past, astronomy included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars. Nowadays, professional astronomy is often said to be the same as astrophysics.Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results.
Astronomy is one of the few sciences in which amateurs play an active role. This is especially true for the discovery and observation of transient events. Amateur astronomers have helped with many important discoveries, such as finding new comets.

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  1. D

    Astronomy question - Sidereal time calculation

    Homework Statement (a) Calculate sidereal time at 11am on December 8th of any year. (b) Calculate the Greenwich Sidereal Time when the local sidereal time on longitude 20 degrees (West) is 20h 45m. Homework Equations I know from my notes that a Sidereal day is 4 minutes shorter than...
  2. M

    Science Fair Project Ideas for Astronomy

    Hey there guys! I haven't been on this forum a while, been busy with school work and assessments, but still catching up on astronomical developments and physical advancements (Higgs Boson around the corner soon?!) Anyways, as the title suggests, I'm definitely entering a local science fair...
  3. T

    Should I Pursue Astronomy or Planetary Science in Grad School?

    My main interest in physics is b/c of astronomy. I'm doing physics undergrad as a stepping stone to grad school astronomy/astrophysics. However upon introspection I notice that my main interest in space lies in the solar system and exoplanets and the potential for life. Is astronomy then the...
  4. F

    Focal Length problem for astronomy class

    Homework Statement A telescope has a focal ratio of f/7.5. You wish to use it with a spectrometer that requires an f/10 beam at its input. Compute the focal length of a 50mm diameter lens that, when inserted in the beam 150mm in front of the unmodified focal plane, produces the required beam...
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    Astronomy - Hohmann Transfer Orbit

    The most efficient way to reach Mars from Earth is following the Hohmann Transfer Orbit (Wolfgang Hohmann, 1925). A spaceship must first get free of Earth (it still orbits the Sun together with Earth, at 30 km/s, at a distance of 1 AU), then it adds speed so that its aphelion (in its orbit...
  6. N

    Physics or Astronomy informative speech ideas?

    I need some ideas for a physics or astronomy related speech?
  7. P

    Programs Should I Pursue an Astronomy Degree?

    Hi guys, I am wondering whether I would be taken seriously by the admissions committees if I were to apply for a B.S. degree in Physics-Astronomy (concentration) because I am in the social sciences, getting my M.A. in a social science field this May. I want to earn my Ph.D. in Astronomy...
  8. N

    Is anyone familiar with The Open Astronomy Journal?

    http://www.benthamscience.com/open/toaaj/index.htm, published as part of http://www.benthamscience.com/open/index.htm. From the website:
  9. L

    What is the difference between Astronomy, Astrophyics and Cosmology?

    What is the difference between Astronomy, Astrophyics and Cosmology?
  10. D

    Continue EE or change to Physics and Astronomy

    I'm currently a second-year student in EE at a large state school (top 30, I think). I chose EE when I applied, but I never really put any thought towards what major I wanted. I had taken AP physics, etc in high school and was always pretty good in math and sciences, so people told me to go...
  11. A

    What are the differences between Astrophysics and Astronomy?

    Hello, i am deciding between a career in astronomy or astrophysics and need help. I wish to know the differences in the two careers. What do each study? what is the pay difference in Canada? Where do each work and what do they work on?
  12. Y

    Can you please check my answers to those short astronomy questions?

    Please tell me if there are mistakes, however small, in the answers I have provided to these questions. Thank you in advance. 1. Why are pulsars not always associated with supernova remnants? Most pulsars are created by Type II supernovae, but out of all the pulsars detected yet (around...
  13. S

    2012 Physics and Astronomy REU Programs

    I'd like to make a thread for those who are applying to REU programs in physics and the like this summer. Please post where you have applied, what your research interests are, and post when you hear from specific programs to help others make their decisions. Also feel free to discuss any...
  14. B

    Computational Astronomy career advice please?

    Hi All! My name is bergw, I'm new here and I'm looking for some advice. I'm a software engineer in the CAD business who is dying for more interesting work! I'd really like to get back to the interests I had back from college(Astronomy) but I'm finding it difficult even finding software...
  15. A

    What Happens to Photons Near a Black Hole?

    1. Photons approaching a black hole will initially a. all of the above are possible depending on distance from the event horizon b. pass by with their direction changing (bending/curving) c. fall into the black hole d. go into orbit around the black hole e. pass by without...
  16. J

    Indoor Astronomy: Viewing Options for Cold Places

    most good observing locations seem to be located in high-altitude, COLD, places. even though i am not at high altitude, it is still mighty cold at night here in oregon. what would you recommend for an affordable method to do basic observation where the scope is located outdoors but viewable...
  17. B

    Schools Astronomy and Astrophysics at University of Toronto; Admission requirements?

    I am interested in the Astronomy and Astrophysics program at the University of Toronto. How well does one need to do in high-school to get into the program? What are the required courses and what marks would be advantageous? Any help would be greatly appreciated.
  18. S

    Programs Would it be possible for me to major in Astronomy advice please.

    I'm a freshman in university, just finishing up my first semester (I've got 3 finals left and then I'm done). I just turned 18 last week, too. I'm in arts at the moment, but I've been thinking that I want to switch to sciences and aim for a degree in astronomy...the problems I face, however: -...
  19. Vorde

    Schools Undergrad Astronomy Safety Schools

    As part of my junior curriculum I'm taking a college prep course. As part of this course I am gathering a list of colleges I plan on applying to, including several safety schools. I have several schools that I am totally confident that I will be able to get in, but I wouldn't quite call them...
  20. E

    Bill O'Reilly the master of Astronomy?

    talks about our moon its fascinating.
  21. W

    Radio astronomy - integration time vs. sample rate

    Sooo I wasn't sure if I should put this here or in the astrophysics section, but I figured electrical engineering was more relevant for my question. I'm involved in a project at my university to build a (very) simple radio telescope, but I'm having a bit of trouble with the radiometer...
  22. S

    Schools James Cook University Online Astronomy Degree: Worth it or Not?

    Hey everyone! I am new to the forum so be kind. I tried using the search function to find an answer to this question but could not dig one up. I have come to a point in my life where I need a career change I am 26 and considering a few options to shake up my life. I have long had a passion for...
  23. S

    How to Accurately Convert FK5 to Altitude and Azimuth?

    Hello all, I'm a surveyor working on an Excel spreadsheet to convert FK5 positions into altitude and azimuth system. Yeah, I know there's an FK6, but one step at a time. I know it sounds simple, right. But I have to account for proper motion, precession, nutation, aberration, parallax...
  24. M

    Programs Astronomy-related PhD without Astronomy Undergrad

    Hi All, Just some quick background that may be relevant before my question: I am 29 years old and am back in school after not knowing what I wanted to after high school. Originally, I did well some terms and not so well other terms starting out, and I ended up taking a ~5year break. In my...
  25. C

    PhD Astronomy Prof: Paucity of evidence for the Big Bang

    PhD Astronomy Prof: "Paucity of evidence for the Big Bang" an acquaintance of mine who holds a PhD in physics and teaches astronomy at a university says the is "a paucity of evidence for Big Bang theorizing". After I close my gaping mouth how should I respond?
  26. H

    Stargazing Telescope for my astronomy class next semester

    :biggrin: I need a telescope for my astronomy class next semester :biggrin::biggrin::biggrin: and a $700 budget...having a difficult time deciding which one to get :-/
  27. M

    Astronomy career academic guidance.

    Hey I'm 21 years old, I have been going to a community college for about a year and a half.. ofcourse this college is not difficult and I have close to a 4.0.. Basically I've always have been fascinated with outer space, I'm wondering if anyone here can guide me on the degrees I would need to...
  28. P

    Stellar Astronomy - Measuring surface temp of the Sun

    Homework Statement "Determine a surface temperature value for the Sun from the angular diameter of the Sun and the solar constant." Homework Equations L=4π(R^2)σT^4 The Attempt at a Solution At this point my only stumbling block is I don't understand the relationship between the solar...
  29. I

    Graph using Maple for Astronomy

    Homework Statement I am not sure what to do with Maple. I've barely used it at all, but trying to figure out why this won't work with what I have below. Plot schematically the change in equilibrium temperature of Earth, if its albedo changes from 0.3 to 0.7 (in 0.1 jumps). Homework Equations...
  30. T

    Astronomy - Measure distance to other galaxies

    I have understand that the Parallax method can be used to measure the distance to stars, but what happens when the parallax angle gets to small to be measures accurate? What kind of methods are used to measure distance to star that are like 5000 light years away, or to Superclusters that are...
  31. T

    Astronomy - Main sequence and red giants

    What is the main reason why there are so many more stars in the Main sequence in comparison with the number of red giants?
  32. T

    Astronomy - Correct solution? Part 2

    Homework Statement I have made a solution to an exercise and I need some to check it and please notify me if I have made any misstakes. Exercise A satellite that is a black body, spherical and rotates around its own axis is send towards the Sun. How far will the satellite reach before its...
  33. T

    Astronomy - Correct solution? Part 1

    Homework Statement I have made a solution to an exercise and I need some to check it and please notify me if I have made any misstakes. Exercise Calculate the radiation flux density of the surface of Earth from the sunlight that is reflected against the surface of Mars. As seen from the...
  34. A

    Astronomy - binary magnitude conceptual question

    astronomy - conceptual, trigonometric parallax Homework Statement To determine a star's trigonometric parallax, we need at least 3 measurements of its position relative to much more distanct objects. Explain why this is true. (What else could change its position on the sky?) Homework...
  35. Vorde

    What are the differences between studying astrophysics and astronomy in college?

    Hey all, I am starting to think about colleges, it's a bit early for me (I'm entering 11th grade) but knowing which colleges I am seriously interested in would be a big help for a lot of reasons. I am absolutely sure I want to pursue a path in theoretical physics (not sure if that's the right...
  36. A

    Programs Astronomy Major does anyone care if I get it or not?

    Hi, I'm a senior at the University of Wisconsin and I will be applying to grad school in physics soon. I'm currently majoring in Math, Physics, Nuclear Engineering, and Astronomy. I have 6 credits left to finish my astronomy degree and I'm seriously considering not finishing it out. As it...
  37. excelsior

    Programs Pursuing Astronomy After RTVF Degree: My Story

    Hello there! First post but I figure I'll get right into it. A lot of thoughts and I'd just like to see if anyone has done or seen anything similar. In 2006 I graduated with a BA in Radio, TV, & Film. I worked as a recording engineer (my initial career goal) for a few years, decided I liked...
  38. T

    Schools Undergrad research for astronomy grad school

    hi - does it matter if you do research or not in astronomy as an undergrad? is it ok to just do undergrad physics research for astronomy grad school? does it look any better to do astronomy research versus physics research as an undergrad, or any physics will do? I'm asking as a matter of...
  39. F

    Astronomy Careers: High Pay & Questions Answered

    Hi guys, I'm really interested in Astronomy related careers yet my parents want me to enter medicine due to its high pay. I'm a highly academic student and I am capable of entering medicine, however, I really want to do an astronomy/astrophysics course as I want to make a mark in the upper...
  40. 1

    Astronomy vs Astrology: A Comparison | Physics 191 Book Cover and Side Photo

    Get this, my Physics 191 book, which is basic astronomy Here's the cover. http://imageshack.us/photo/my-images/405/coverjgc.jpg/ Here's the side. http://imageshack.us/photo/my-images/543/sidee.jpg/ Someone wasn't paying attention.
  41. A

    Small Angle Question in relation to Astronomy

    First of all this is NOT for class! Secondly, this seems rather simple, so perhaps I am simply overlooking the obvious. Anyway, here goes: If some binary star is about 400 ly away, and a telescope gives a separation of 36" (0.01 degrees) for the binary, then can we use the small angle formula...
  42. R

    Mtech in Astronomy after Btech in IT?

    Is it possible for me to pursue Mtech in Astronomy after Btech in IT, in India? Please help
  43. S

    Books on Astrophysics and astronomy

    I have always been interested in astrophysics but my career took another direction and I have an MS in computer science. I wanted to go back and revive my interest. I have decent math/calculus background, ODE, PDE, numerical methods including solving PDE/ODEs, some linear algebra and...
  44. S

    Radio Astronomy. Baselines and Fringes, Interferometry

    As I understand Interferometry, a baseline does not refer to the distance between two RA scopes. It's the distance between two line of sites for each scope. They are parallel, when directed at the same object. Suppose we have two scopes at two stations that are some distance apart, say...
  45. T

    Astronomy - Distance with different scale factors

    Homework Statement Expansion of the universe is described by the scale factor R(t), where t is the time after the Big Bang. For a flat universe the scale factor is today R(t)=C_{1}\cdot t^{\frac{2}{3}} When the Universe was radiation dominated, for t <200,000 years, the scale factor was...
  46. T

    Changing from mech engineer to astronomy

    I am currently a mechanical engineer student in greece.I really don't find mech eng. that interesting so i am willing( when i finish my 5 year study) to change field and study graduate astronomy.WIll i be able to do that?Also i really don't want to study again in undergraduate level.I am...
  47. A

    Engaging in researchwork in Astronomy

    Hi, Recently, at our department we formed a research group in Astronomy and Astrophysics with a bunch of young enthusiastic undergraduates who are keen on engaging in research work. Since not much research work in Astrophysics being carried out in Sri Lanka, the students are bit disappointed...
  48. C

    Programs Is an Astronomy or Physics Degree the Best Path for Studying Space?

    Hello, after recently graduating high school, I'm planning on going to college soon, and I got a couple of questions regarding Astronomy and Physics. First, after recently getting interested in Astronomy, and always being interested in Physics, my question is how much is physics/mathematics...
  49. L

    Stefan-Boltzmann law question (astronomy)

    Homework Statement in about 6X10^7 y from now, the sun will be a red giant star with a temperature 1/2 its present value and a radius 100 times larger. a) what will be the luminosity of the red giant sun be compared to its current value? b) assume that the new luminosity gives you the...
  50. J

    Are Freeman's Law and the Tully-Fisher Relationship the Same?

    Homework Statement Hello I wanted clarification on freeman's law and the Tully fisher relationship. Am i correct to say that the tully fisher relationship that states L=kv^4 where L=luminosity of galaxy and v= max rotational speed of galaxy. only applies to edge-on spiral galaxies...
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