What is Astronomy: Definition and 820 Discussions

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. O

    Average time per week early-career academics in the US work?

    Hello. I've got two questions: 1) In the U.S., what's the average time per week that a graduate student doing a PhD in astronomy work? 2) In the U.S., what's the average time per week that a postdoctoral researcher in astronomy work? Thanks in advance for your answers.
  2. S

    Astronomical source extraction in non uniform background

    I have been working with some Herschel images and I am finding it difficult to extract the astronomical sources from the image. The image background is extremely non uniform so i am not able to differentiate between the background and the source. I used some tasks in HIPE like source extractor...
  3. JoAstro

    Surface temperature of a star?

    I am trying to find the temperature of a star given its wavelength in micrometres, but I am not sure if my conversion is right therefore don't know if the answer is correct. Star A has a maximum emission wavelength of 1 μm and Radius 100 Rsun. What is its Effective Temperature and Luminosity...
  4. JoAstro

    Stargazing How to calculate the amount of light a telescope collects?

    Having the unaided eye's pupil to be 6.4mm and the diameter of a telescope 8-inches, how can I calculate the amount of light the a scope collects over the human eye?
  5. jamalkoiyess

    Astronomy/Astrophysics subdivisions

    hello, can anyone give me what they know about astronomy and astrophysics subdivisions in masters degrees and Ph.D.s . thank you
  6. W

    Yet another read-my-REU-essay-please thread

    Hi guys! Like the title says, I'm applying for 10 astrophysics-related REUs, and I'm a frosh, so I have few other people to ask for guidance. Please let me know if this is a good baseline to add to. Thank you all in advance!Sitting in the middle of an abandoned lab, late on a Friday night, head...
  7. O

    In astronomy what is the average duration of doing postdocs?

    Hello. I read that in astronomy a PhD lasts an average of 6.1 years. But what about postdoctoral research? In astronomy, what is the average duration of doing postdocs before finally getting a real job? (a job as an astronomer; not reconverting to another field to get a job in this other...
  8. JoAstro

    What's the thermal energy of a helium atom?

    I have this formula "E= 1/2 mv^2" which I don't fully understand. Also, I don't have the values for helium's mass and velocity.
  9. T

    Confusion in Doppler shift equation?

    I'm just trying to build Doppler shift equation for Moving observer and stationary source. I have an problem in a step. I'm attaching a screen-shot please check it and tell me where to this step ( 1 - v/u)^-1 comes from ? Thanks in advance.
  10. M

    Anyone in Honolulu interested in astronomy, etc.?

    Hi! I'm new to the forum, but I'm looking for some people who live in Honolulu who are interested in astronomy, astrophysics, cosmology, etc.. I'm especially interested in clubs/group meets and getting together to view astronomical events. Check out my profile to learn more about me. :)
  11. M

    Exploring the Depths of Astronomy and Astrophysics in Hawai'i

    Hello, all! My name is Marina and I currently live in Honolulu, HI. I'm an ocean engineering major, but my primary interests are in astronomy and astrophysics! I'm hoping to meet a lot of people here that can help me deepen my understanding of those subjects, and maybe even find some people...
  12. R

    Astronomy Non Calculus Astronomy Math textbook

    I am participating in science olympiad just for fun this year, because i have a mild interest in astronomy. I am in the astronomy event, my partner has decided to split the knowledge into math and non-math, and as i will be handling the math I would like a book(or however many) that has...
  13. S

    What are the job prospects for Astronomers in the next 10-15 years?

    Hello all! I am currently a freshman (just finished my first semester) and I need to choose a career path. I have had a burning love and passion for Astronomy/Astrophysics from a very young age but I hear that the job market for Astro Ph.D's is complete and utter dang (pardon my French). I grew...
  14. ujjwal3097

    Programs Physics major vs astronomy major

    I am attending college next year but I am really confused between two majors. I am interested in astronomy and my dream is to pursue my career doing astronomy and I can wait to study astronomy in college. I know that astronomy is completely physics but I am confused whether should I choose...
  15. C

    Signal to noise ratio and uncertainty in magnitude

    1. The problem statement, all variables and given/known dat Show that if you have a signal f and noise σf for a stellar flux measurement, then the uncertainty on the observed magnitude is given by σm = 1.0875 x σf / f Homework Equations (you should use the fact that when ε<<1 then log(1±ε) ≈...
  16. planethunter

    Astro PhD at 34: Chances w/Math & Physics Bkgrd & Good PGRE Score

    I am 34 years old and have a bachelors in math from about 10 years ago. I've also taken 3 graduate physics courses throughout the years. I work full time as a systems analyst, and have been doing this type of work since I graduated from college in 2005. I also have an MBA. I’m wondering, with...
  17. Astrodent

    How many stars we can see from Earth?

    Greetings, Hi, I am new member of Physics Forums. Here is my question: How many stars can we see from Earth? and also If you know, How far can we see? Thanks!
  18. GiantSheeps

    Schools Schools with astronomy, observatory, and planetary science

    Hi! So I've begun the process of looking at colleges now and I really would like to go to a school in the US or Canada with an astronomy major, an observatory of its own, and some sort of planetary science program. I've made a list of the schools that I've been able to find with those things...
  19. K

    Flat Rotation Curve Astronomy Question

    I've been struggling with part (a) of this question. I'm not quite sure what the relation is. Any help is greatly appreciated! Thanks! Consider a spiral galaxy with a “flat” rotation curve beyond the central 2 kpc. a. Derive the general relation giving the orbital period, P, of a star (or...
  20. MidgetDwarf

    Introductory Astronomy or Astrophysics book

    Interested in learning about Astronomy/ Astrophysics. I do not know anything besides the planets, and apparently I learned today that Asteroids are rich in metals.?? I am looking for a book that is introductory, but is not to easy. I have taken a course in freshman calculus based mechanics and...
  21. S

    Difference between Cosmology and Astronomy

    Well I was just wondering that what exactly difference between Cosmology and Astronomy...?
  22. Diego Fernandez

    Ideas for Physics project? IB IA on Astronomy

    Good day :smile: For quite some time now, I've been thinking about what I should make my Internal Assessment for the IB course in physics on. The main objective of the IA is to find and prove a mathematical relationship between an independent and dependent variable. A very, very, simple example...
  23. Ravyan Asro

    Pros and cons for a career in stellar astronomy

    I am really interested in learning more about the space and the universe. And studying about stars interests me the most. So, I have decided for a career in stellar astronomy. However, stellar astronomy is a very huge field of space science and a rarely chosen career. I have a thousand of...
  24. J

    Calculating Jean's length for neutral hydrogen cloud

    Homework Statement What is the Jean's length in parsecs for a typical neutral hydrogen cloud, which has a density of n(H I) ~10^8 atoms/(m^3) and a temperature of 100K? Homework Equations jean's length = sqrt[(15*K*T)/(4pi*G*u*p)] where: 'K' is the Boltzmann constant 'T' is the temperature of...
  25. J

    What is Imaging Science and How Does it Impact Astronomy and Planetary Science?

    I am a sophomore at RIT studying imaging science, which is essentially a major dedicated to the engineering and development of imaging technologies. i.e. MRIs, lasers, telescopes---anything that involves light. I love my major and plan to use it to pursue a career in astronomy and planetary...
  26. Klashta Neali

    I choosing a career in physics to pursue

    I am only in grade 10 but stupid Careers course says I have to choose a career to do a summative study on. I want to choose something that I might go into but I can't choose. The NOC list for "Physics and Astronomy" is very long--I deleted the ones I am not interested in: aerophysicist...
  27. H

    Python 2.7 on Windows installation for Astronomy

    Hello people i know this program is better to use on Linux, but for personal reasons i can't change to Linux OS. So I'm having a little problema on how to use python and install the modules of astropy, ipython, I've already installed pip but i have a error on python shell that says: Error...
  28. Kelson Adams

    Use 3D laser scanning to map Outer Space?

    Mobile, airborne, and terrestrial 3D laser scanning gives an unprecedented amount of data to companies, organizations, and governments. However, I am wondering whether or not 3D laser scanners have ever been used in astronomy, astrophysics, and in astrocartography... If they haven't, I believe...
  29. O

    Schools Which are the best American universities for astronomy?

    Hello. I'm a French student and I'm planning to go to the United States for a graduate program in astronomy. When I will arrive in the U.S. I will begin by the first year of graduate. Then I will pursue with a Ph.D. and some postdoctoral research. I would like to know which are the best...
  30. G

    K Corrections: Explaining Fluxes in 250μm (Janskys)

    So I'm trying to k-correct some fluxes in 250μm (janskys) using the M82 template found here and the relevant equations found here (I also have the transmission filter function). The template is normalised to 5500 A and doesn't have a brightness so I fail to see how I can correct my observed...
  31. GiantSheeps

    Stargazing Remote Controlling Truss Dobsonian Telescope?

    Is it possible to rig a Truss Dobsonian telescope like this one so that you can control it remotely from inside of a building while the telescope itself is on the roof of the building? Then is it possible to attach some sort of adapter to the telescope that would allow you to hook up a camera...
  32. H

    Vibrational Continuum in Interstellar Medium: A Closer Look

    Hello everyone, this is my first poster here. I met this problem when I was attending class of interstellar medium, and I was confused by the question.
  33. pioneerboy

    Lunar and Planetary Laboratory vs. Steward Observatory

    Hi there, The University of Arizona has these two institutes (among many others, of course): - Lunar and Planetary Laboratory, LPL for short - Steward Observatory As far as I understand, both are into space research and astronomy. If I wanted to join either one or the other, I would have no...
  34. ujjwal3097

    Programs Physics(astronomy) major vs engineer major

    Hi I am a high school student and currently planning to apply for undergrad studies but i am bit confused in deciding my major.I am pretty sure that I want to major in field related to physics .I am interested in astronomy /astrophysics and also interested in engineering .Please can anyone...
  35. S

    Difference between Astronomy and Cosmology

    What Is the difference between Cosmology and Astronomy..?
  36. GiantSheeps

    Wesleyan for Astronomy and Physics Undergrad

    I'm a junior in high school and I'm starting to look into colleges. The one that I'm most drawn to is Wesleyan University in Connecticut. I want to major in astronomy and physics, perhaps with a minor in planetary science. Wesleyan offers all of those courses, but does anyone know if they are...
  37. W

    Gravitational force confusing question

    I have this question on my practice test that I can't figure out. "Just as one jumps out of a plane what is their gravitational force given that the mass is 70kg." The thing is, for me to use the gravitational force formula I need to masses. The test only has the one. Am I missing something? Am...
  38. DHF

    Need help with astronomy details in a book.

    Hi and thanks in advance for any help. The book I am currently working on features a protagonist that is an astronomer, I was hoping those more knowledgeable then I could check the passage where she describes her work and make sure it doesn't sound like gibberish. much appreciated. "Though she...
  39. Prins

    Astronomy Books on Astrophysics and astronomy

    Hi I have done my m.Sc now I'm interested in the field of astronomy but there were no subjects regardind astronomy in my masters course work I'm thinking of going into a PhD So I wanted to check aa the topics and get myself to the level to do PhD so please suggest some books
  40. CrackerMcGinger

    Need reliable resources on basic astronomy and quantum physics

    I've been relying on Wikipedia and some other questionable sources for a basic understanding of these studies, and i don't think I should rely fully on these sources. If anyone can point me to a place that is reliable I would greatly appreciate it.
  41. S

    Best Country for studying Astronomy

    Which country is best to study astronomy? To be specific which university is preferred.?
  42. S

    Career related to Astrophysics and Astronomy or other space

    So what I want to ask is that I will be entering a university next year so career selection is one of the very tricky and difficult decisions. MY question is that what if I do Some PhD in astrophysics or astronomy what type of job can I get other then a professor.? And as an foreign I may not...
  43. A

    I Is there any international astronomy competitions for adults

    Hello every one . I am 19 years old and i can't be in olampiyad of astronomy . actully i really want to be in a international astronomy competition but i don't know whaaat ?? please help me . thanks
  44. sunrah

    Yay, starting my Astronomy MSc this month

    After all those years of doing physics, I finally get to do something that interests me :woot: Just kidding, good luck to everyone starting at uni this year!
  45. F

    Calculate flux from a radiating disk

    Homework Statement Suppose you have a disk of radius r at x=y=z=0 with its normal pointing up along the z-axis. The disk radiates with specific intensity I(\theta) from its upper surface. Imagine the observer plane is at z=Z, where Z is much greater than r. Let I(\theta) = I = constant...
  46. Armando Valle

    Hey everyone, where can i study astronomy on internet?

    hello everyone, can someone help me know where I can take a course in astronomy / cosmology on the Internet where you get recognition and diploma and to get on with my passion of the universe? This means a lot to me and I want to move on in my passion. thanks
  47. Armando Valle

    How do we know galaxies are exactly where we see them?

    i have a doubt, how do we know far away (light years) galaxies and planets are on the right spot we see them? if light takes a lot of time to reach the Earth it means we are seeing the past of the galaxy/planet. Example: If Earth is becoming extinct and we need to find an exoplanet 30,000 light...
  48. B

    Teaching Astronomy to 11-16yr Old Boy Scouts

    I'm an 18 year old scouts member; which makes me one of the "elders" of the boy scouts. My chief has asked me to prepare an astronomy session to teach to 11-16 year old boy scouts. I'll be joining them on their summer camp in 2 weeks time. So I'm supposed to wake them up in the middle of the...
  49. C

    Astronomy Good ancient to modern history astronomy books?

    Hi, Can anyone recommend some good ancient astronomy books (from around 8000BC-0) that that are historically correct (perhaps springled with a few translations from older writings) with visual images, and that show in some detail how different calculations, and observations were made? It would...
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