What is Astronomy: Definition and 823 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. P

    Programs Should I do a math or an astronomy double major for general relativity?

    Hi! I'm going into college during the fall, (Stony Brook University in the US) and I want to research general relativity in the future. I can choose to do an astronomy or math double major alongside my physics degree, and I want to know which degree will best prepare me for a graduate program in GR
  2. Da_Rex

    Need Ideas for a Physics Astronomy EE for IB

    TL;DR Summary: I had a physics EE idea for finding the age of Andromeda using data from the university our school is linked with, however this turned out to be near impossible, therefore I wanted to find more doable things. Need Ideas for Physics EE
  3. grahamoctave

    New Member

    I am a retired musician and music teacher (woodwinds). I have had a lifetime amateur interest in astronomy and physics generally. I am also interested in the physics of musical instruments. For many years I was an amateur pilot so I also have an interest in the physics of flight.
  4. Field physics

    B Waves in space

    So I've seen that radar can be used in space which is interesting and brings questions to mind as well as theories. Unrelated Sonar which uses sound waves don't work as sound isn't transmittable through space. Questions: 1) What techniques are used in radar to prevent "wondering" or the radio...
  5. Somoth Ergai

    B New Paradox Discovered, I Think

    User New here but this conundrum is something that occurred to me as I was watching a physics video and I have run out of ways to ask about this. So here I am. Ok first principle. the setup. let's say we have invented a perfect telescope on earth. such that we can resolve any object no matter...
  6. DaveC426913

    B What Does the Astro Physics Equation from Lewis Season 8 Episode 2 Mean?

    I know, I know, I'm committing the cardinal sin of putting any stock in the technobabble of a TV show, but this one seems egregious. Lewis (English WhoDunnit-in-Oxford on Britbox) Season 8 Episode 2 "The Lions of Nemea" had an astro physics professor who said this: "... and so we see that one...
  7. Sciencemaster

    I Observational Astronomy Project Ideas to Show Special Relativity

    This semester, I'm taking a class on Observational Astronomy which requires us to perform observations for a final project over the course of roughly a month (mid-March to Mid-april, although it could be a bit longer or shorter). As we get to choose the project, I'd like to take this opportunity...
  8. Wyvyrn

    What is an Intelligent Dilettante?

    Just a guy with huge Curiosity Quotient, in subjects ranging from Astronomy to Quantum Physics, to Geology and Ancient Mythology, Chemistry to Science Fiction & Fantasy, and finally Science in General.
  9. Greg Bernhardt

    Astro/Cosmo Award

    Please select up to 3 members who were most impactful in the Astronomy and Cosmology forums in 2023. This is a popular vote. Polls were created by weighing activity and measure of helpfulness. Everyone nominated should feel honored. Many more could be added to this poll, we can never...
  10. T

    What Have We Learned from Studying the North Ecliptic Pole?

    Astronomer - have built and used lots of stuff for ground and space based astronomy, and worked on top of countless mountain tops across many continents; studying the radio Universe from the deserts of New Mexico, taking pictures from mountain tops in Chile, Hawaii, La Palma, listening to the...
  11. DiamondTiara

    Exploring the Universe: A Journey through Astronomy and Cosmology

    Hello there. I am Diamond Tiara and I am interested in Astronomy and Cosmology. I am also into fictional works involving solar systems and planets.
  12. Physicsperson123

    I Terrell rotation is confusing!

    Imagine in the distance you see a glowing spherical object hovering in the air. Suppose light from point B on the surface of the sphere facing away from you can arrive at the camera simultaneously with light from A: Since the object is moving at relativistic speeds, by the time light begins to...
  13. peabody1998

    Newbie needs help with angle iron load calculation

    I am trying to decide on the material and dimensions for the rail. The rails are supported on either side of a 10ft span. -- What dimension steel angle can carry a 200lb load across a 10ft span? a=? b=? c=? -- What dimension aluminum angle can carry a 200lb load across a 10ft span? a=? b=? c=?
  14. Glenstr

    B Did I photograph some sunspots?

    I was editing a timelapse I did of a sunset this summer with my Pentax K70, using 18-270mm lens at full zoom, using raw photos. At first I thought I had a speck on the lens when I saw a spot on the left side about the middle, then I noticed it stayed on the sun as it went down. Then I noticed...
  15. WesKnight

    B Questions about relative Space-Time in the Universe

    Hello everybody. I have been having a lingering question about the State of the Universe. As humans, we view the Universe's expanse as historical from the vantage point of Earth. For example, 10,000 light years away would have occurred 10,000 years ago. On that same logic, looking at Earth from...
  16. AndreasC

    Astrophysics Up to date astrophysics and astronomy books for physicists

    With all the recent debates about CDM vs MOND etc, I decided I need some more background on astrophysics and phenomenology. I have the physics background, I prefer concise books even if they are harder. I was considering something like this for phenomenology...
  17. Graham 1956

    Stargazing Question about my photos of a Full Moon -- What is this point of light?

    I have just taken three photos of the full moon. I am in Southern Spain and the photos were taken around 22.40 (CET). In each of the three photos, taken within seconds of each other, there is a bright point of light (a dot). In one frame it is in front of the surface of the moon. In the other...
  18. P

    B Looking for help Understanding Inertia

    Just a thread to see how inertia works, just studied the laws of motion, and have been fascinated with it.. could use some help on it tho :)
  19. mihaivzr

    Optical What would an amateur need to make accurate astronomical measurements?

    Planning to manually rediscover or confirm our exact place in the Solar System, Galaxy and Universe. I've noticed that even 50 mm high quality amateur telescopes are likely well better than what Galileo Galilei era scientists had for the first half century. The theodolite looks like an inspiring...
  20. T

    I Star cluster in the Milky Way appears to be as old as the Universe

    https://www.sciencenews.org/article/star-cluster-milky-way-old-universe https://doi.org/10.48550/arXiv.2306.02180 Cheers, Tom
  21. DaveC426913

    B Has Earth Lost Its Status as a Planet?

    The International Astronomical Union (IAU) defined in August 2006 that, in the Solar System,[1] a planet is a celestial body that: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighbourhood" around its orbit...
  22. Vanadium 50

    B Which star is the closest red giant to Earth according to The Guardian?

    The Guardian claims Betelgeuse is the closest red giant to Earth. Not even close. Aldebaran Arcturus Mira Delta Andromedae The abominably named Gacrux Capella, which despite the color is a red giant Possibly Antares (distances are similar) And, what is likely the correct answer, Pollux. Think...
  23. J

    B How can the Universe be flat? Ridiculous

    The earth is a sphere. I can stand anywhere on its surface and look up directly above my head at the night sky and see lots of stars many light years away. I see this view wherever I stand on the earth's surface although the stars will be different ones, depending on where I'm standing...
  24. F

    Admissions Profile evaluation for astronomy Phd applicant in the fall 2023 cycle

    I will apply for a Ph.D. in Astronomy in the fall of 2023. I want to have a realistic evaluation of my profile to see if I am over-ambitious or not. I think I am out of reach for the "big four" universities. I will donate money to two of them only and will be targeting other top schools...
  25. xpell

    B At what distance would a Venus-like planet have a HZ temperature?

    Well... that: Please, could you please assist me in obtaining a rough estimate of the distance from the Sun at which a planet resembling Venus or a hypothetical Venus-like planet (for the sake of simplicity) would have a habitable-zone surface temperature? A "back-of-the-envelope" educated...
  26. J

    Why globular clusters don't collapse.

    I asked Bard that question and it responded (among other things) that a) globular clusters are spherical and b) that they are spinning rapidly. Aren't those two things contradictory, as in they should be flattened by centrifugal forces?
  27. Astronuc

    B Saturn's 145 Moons: The Latest Discoveries and What Sets Them Apart

    Saturn reclaims 'moon king' title with 62 newfound satellites, bringing total to 145 https://www.space.com/saturn-moon-king-62-newfound-satellites Astronomers have discovered 62 new moons orbiting the ringed planet Saturn, bringing to total to 145 Moons, with 121 irregular moons and 24 regular...
  28. F

    Tusi discovering laws of planetary motion before Kepler?

    I was reading about the Tusi couple and read it "as a solution for the latitudinal motion of the inferior planets, and later used extensively as a substitute for the equant". Since the Tusi couple is related to plotting out an ellipse, did Nasir al-Din al-Tusi already discover the laws for...
  29. L

    B Can anyone suggest a good website to buy astronomy equipment?

    I am looking into proper and well tested solar glasses for the upcoming total eclipse next year. Also solar film and clip to attach to my camera so I can do a video. I'm scared to just buy randomly on Amazon.
  30. Ken G

    Is ChatGPT useful yet for answering astronomy questions?

    TL;DR Summary: It seems inevitable that internet searches to answer astronomy questions will someday involve AI assistance. Is ChatGPT reliable enough yet for that, or still nowhere close? The issue for me at this point is how to distinguish the errors ChatGPT currently makes, versus the...
  31. E

    I Research paper and sources investigating Earth's moons

    Hi. I am looking for scientific papers, articles and/or even simulations that investigate how many moons it would be possible for earth to have and maybe modern theories about what these moons can be and look like (i.e what characteristics they have) if they were to exist. I have googled and...
  32. G

    Programs Should I major in Physics & Astronomy or Physics & Math?

    I'm currently in my first year of a combined major in Physics and Astronomy. I'm hoping to study theoretical cosmology, and get a PhD in physics. I've been told it would be wise to get a double major in Physics and Math if I wish to study theory, but would it also be wise to get a combined major...
  33. M

    B Would the Giant Arc be visible from a hypothetical exoplanet?

    I recently watched History of the Universe and they talked about the Giant Arc, a large scale structure that spans 3.3 billion light years long, exceeding the hypothetical limit of 1.2 billion. The Arc was discovered last year. https://en.wikipedia.org/wiki/The_Giant_Arc They said if the Giant...
  34. P

    Maximum duration of Solar eclipses

    The result I get is 2 hours and 10 minutes. My reasoning is down here. But! Checking the map for the 2024 Solar eclipse, https://www.timeanddate.com/eclipse/map/2024-april-8, in many locations you can see a partial eclipse of over 2 hours 40 minutes. What is the main source of error here? Here...
  35. P

    Education articles about Astronomy helping learning Math and Physics

    Is there any specialize articles that talk about how Astronomy can help learning Math and Physics? In particular, how observational astronomy can help in the learning process of Math and Physics.
  36. N

    I How to calculate an unknown planet's orbital period?

    In 1846 three astronomers and mathematicians discovered Neptune because Uranus wasn't quite moving as Newton's law of gravity explains. So they did calculations and point the telescope at a specific part of the sky. They discovered Neptune. What formulas did they use? How did they calculate this...
  37. A

    Exploring the Calculus of Area: A Journey Through Space and Physics

    Umm.. yes I think. Not sure what I’m getting into, but the pursuit of knowledge eh? Teach me please. I’m just here to share thoughts and bounce between fellow big brains. Haha this strange. Good luck!
  38. V

    Exploring Opportunities in Aerospace for High School Students

    Hi! I'm Varsha and I'm going to be a junior in high school this coming fall. I'm quite interested in astronomy and engineering so I plan to study aerospace in college, but I'm not sure which topics to focus on and what I should do to stand out to colleges. I'd love to interact with others and...
  39. brainpushups

    B Where Can I Find Accurate Planetary Event Data for an Astronomy Course?

    Hi everyone, I'm looking for a database of planetary events similar to this resource but that has a longer span of time that can be accessed (the site goes back to 2009). I haven't had success in my google searches. Does anybody know where I can find this information? In particular I am...
  40. Green dwarf

    I Exploring Energy in Astronomy: Kinetic, Potential & Mass?

    I am planning to teach a school astronomy group about energy. Most people seem to accept that there are two types: kinetic energy, resulting from movement; potential energy, resulting from position in a force field with a potential gradient (convertible to KE if the object is allowed to move...
  41. megapiano

    Need help with N-body simulation

    Many years ago, for my high school senior project, I wrote a solver for the N-body problem that is performance-optimized using the Barnes-Hut algorithm. (the optimization algorithm is not relevant to my question.) In one particular simulation, I simulated a spiral galaxy. The simulation is not...
  42. DennisN

    I Discovery: A radio transient with unusually slow periodic emission

    Paper: N. Hurley-Walker, X. Zhang et.al, A radio transient with unusually slow periodic emission (Nature, 26 January 2022) Abstract: The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has...
  43. G

    Programs What can I do with a Chemistry BS and a minor in Physics?

    Just to keep this from being a long post: I went to a local CSU for Materials Science and Engineering in the fall of 2018 after graduating high school in the spring of 2018. I really like learning about everything that makes up the world around me, and why things are the way they are, and in...
  44. Joel_Entrup

    Is it possible to become a theoretical physicist with a 120 IQ?

    An IQ of 120 is plenty good, but the average IQ of Physics and Astronomy majors is higher. It's even higher for brilliant theoretical physicists and Physics PhD holders. So is it possible, with enough hard work and dedication, that someone with a 120 IQ could become a theoretical physicist? Or...
  45. V

    Stargazing Understanding the Formula for Sunrise and Sunset Calculation

    Hi, I'm developing a C++ computer library with the formulas in the book "Practical Astronomy with your Calculator or Spreadsheet, 4th edition" but I have a problem with the formula 49, "Sunrise and sunset": I don't get the same results than in the book. I've been searching to find online...
  46. gregatphysics

    I Do all geodesics begin and end at the big bang?

    So. It was late night, the limpid sky a near cloudless darkness, somewhat lightened by the waxing moon. I being somewhat stoned and looking at the stars and constellations as I sometimes do, and it came to seem to me, in my imagination, that In the spaces between the stars, I was observing (in...
  47. W

    I History of astronomy and the Phases of Venus

    Does anyone know when it was first realized that a heliocentric model of the cosmos should show the phases of Venus in the way Galileo saw them in the 17th century.?Was it known in the time of Aristarchus or did people only realize this was a consequence of helicoentrism later on, perhaps only...
  48. ohwilleke

    I Rovelli on Quantum Gravity

    Rovelli points to three pieces of existing observational evidence that should guide future quantum gravity research. Bottom line: * abandon Lorentz invariance violating quantum gravity theories, * abandon supergravity and string theory, and * stop working on the anti-deSitter/conformal field...
  49. S

    Classical Looking for Griffith-style books on mechanics, thermodynamics, astronomy

    Hello! Searching for above mentioned books for my Bsc studies. Like his style and the quantum and electro books were very well written(in my opinion) and easy to navigate through, also liked the pre-explained math tools i need for the book. Tried Goldstein and Taylor books on mechanics but they...