What is Magnitudes: Definition and 110 Discussions

Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
The word magnitude in astronomy, unless stated otherwise, usually refers to a celestial object's apparent magnitude. The magnitude scale dates back to the ancient astronomer Ptolemy, whose star catalog listed stars from 1st magnitude (brightest) to 6th magnitude (dimmest). The modern scale was mathematically defined in a way to closely match this historical system.
The scale is reverse logarithmic: the brighter an object is, the lower its magnitude number. A difference of 1.0 in magnitude corresponds to a brightness ratio of 5√100, or about 2.512. For example, a star of magnitude 2.0 is 2.512 times brighter than a star of magnitude 3.0, 6.31 times brighter than a star of magnitude 4.0, and 100 times brighter than one of magnitude 7.0.
The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46. The faintest stars visible with the naked eye on the darkest night have apparent magnitudes of about +6.5, though this varies depending on a person's eyesight and with altitude and atmospheric conditions. The apparent magnitudes of known objects range from the Sun at −26.7 to objects in deep Hubble Space Telescope images of magnitude +31.5.The measurement of apparent magnitude is called photometry. Photometric measurements are made in the ultraviolet, visible, or infrared wavelength bands using standard passband filters belonging to photometric systems such as the UBV system or the Strömgren uvbyβ system.
Absolute magnitude is a measure of the intrinsic luminosity of a celestial object rather than its apparent brightness and is expressed on the same reverse logarithmic scale. Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of 10 parsecs (3.1×1014 kilometres). When referring to just "magnitude", apparent magnitude rather than absolute magnitude is normally intended.

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  1. Jd1431

    I How would one convert measured magnitudes of a satellite object to radiant intensity?

    I have the measured magnitudes of a satellite object in four filters and I want to convert this into into Radiant Intensity. I was told that if I integrated the solar spectrum over my filter bandpasses , I could obtain the visual mag of the sun in each of these filters and use this to obtain the...
  2. WMDhamnekar

    MHB Velocity and acceleration vectors and their magnitudes

    How to answer this question? I am working on this question. Any math help, hint or even correct answer will be accepted.
  3. K

    B Magnitudes of the sum of two vectors

    This is a question that I saw in a textbook: "If the magnitude of a+b equals the magnitude of a+c then this implies that the magnitudes of b and c are equal. Is this true or false?" The textbook says that this statement is true, but I'm inclined to believe it is false. I made a quick sketch to...
  4. H

    The magnitudes of the applied force F and the frictional force f of a wheel

    I calculate in this way as follows and get a correct answer. Howere I am not sure if I am using the right way. F R = (½ MR^2 + MR^2 ) a/R F = 3/2 Ma F - f = Ma f = 3/2 Ma - Ma = Ma/2
  5. G

    How to calculate the magnitudes of three forces around a hexagon

    Can anyone please help me with the following? Three forces which act along the sides AB, BC and CD of a regular hexagon ABCDEF of side 2a, have a resultant which acts along DF. When a couple of 4Pa in the sense CBA is added in the plane of the hexagon, the resultant acts along CA. Find the...
  6. T

    B Why is an inverse logarithmic scale chosen for the magnitudes of stars?

    Star magnitudes of brightness seem to use inverse logarithmic scales, is there a benefit to this? Why was this chosen, i can understand logarithmic might make it easier to interpret data in same way we do similar for earthquakes etc. But why inverse ? When i look at a HR diagram for example (...
  7. T

    What are the uncertainty values for my corrected magnitudes?

    Homework Statement I need to work out the errors of my corrected apparent magnitudes. The Colour Excess is 0.36 with uncertainty = 0.01 The star was observed in two wavebands. r-band = 2.285 g-band = 3.303 The 2.285 and 3.303 are the ratios R_V for the SDSS (Sloan digital sky servery) r and...
  8. StillLearningToronto

    Calculating Quasar Variability Using CCD Camera and Magnitude Comparison

    Homework Statement You have decided to use a CCD camera to check if a 16th magnitude quasar is variable. With your telescope/camera combination, you know that a star with a magnitude of 0 would deliver 1 × 109 photons/second to one pixel, so this allows you to work out the photons/second from...
  9. A

    Fuel cell mass flow rate magnitudes

    Hello, Can you tell me please the mass flow rate of hydrogen and oxygen per unit of area of electrodes in fuel cells? Or if you have information on the mass flow rate of hydrogen and air per volume of fuel cell stack? I understand this may vary, but I am looking for publications or other...
  10. T

    Combined magnitudes of two solar-type stars

    I am having a issue with part a) of this question, I am not entirely sure if what I am saying is correct, could somone if possible check my logic 1. Homework Statement Two solar type stars (all physical properties are the same as for the Sun) are in a close binary system. Each individual star...
  11. Callum Plunkett

    Help with NEXT and FEXT volatage magnitudes

    Homework Statement A transmission line is formed by two identical parallel tracks in a printed circuit board. The line has a length of 50 mm and all line terminations are of 70 Ω. The line can be assumed to be lossless. calculate the magnitude of the NEXT and FEXT voltages generated in the...
  12. C

    Find C vector, with two known magnitudes

    Homework Statement https://i.imgur.com/UtLzb34.png Homework Equations the law of cosinus The Attempt at a Solution I have not been available to scan my work, but I'm kinda stuck at the beginning. And our teacher have not show us this kind of physics yet. Thanks.
  13. G

    Speed and Velocity vs magnitudes

    Can the magnitudes of speed and velocity be different for the same given situation?
  14. C

    Calculating the Cross Product Vector: Is It Possible to Find VxW?

    Okay so, I am wondering if it is possible to find the actual cross product (not the magnitude of the cross product) from this information 1. magnitude of both vectors 2.angle between vectors 3.plane the vectors lie in Is there any way to calculate that cross product vector? Thank you very much...
  15. DevonZA

    Determine the magnitudes and nature of forces in space truss

    Homework Statement Homework Equations equivalent tension coefficient tDE= applied force/distance between points D and E = 17/SQRT(1[^2+2^2+4^2) = 3.7097 The component of the 17kN in the x-direction = Δx X tDE = -1...
  16. Rodriesk

    Magnitudes and Directions In Uniform Circular Motion

    Homework Statement A biker is 40.0m to the east of a flag in a park, heading south at 10m/s. 30.0 seconds later, the biker is 40.0m north of the flag and heading east at 10.0m/s. For the biker in this 30.0s interval, what are: a) the magnitude and direction of the displacement? b) the magnitude...
  17. TheSodesa

    Magnitude of a component of a triple star

    Homework Statement The apparent total magnitude of a triple star is ##m_0 = 0,0##. The apparent magnitudes of two of its components are ##m_1 = 1,0## and ##m_2 = 2,0##. What is the apparent magnitude of the third component? Answer: 0,9 Homework Equations Since according to Norman Pogson...
  18. G

    I Differentiating Vectors and their Magnitudes in Physics

    I've taken up to Calc. III (vector/multi-variable calculus) but have not had any classes that used intensive calculus for a few semesters. However, I'm now in a quantum physics class (its a glorified title really--it's more or less "modern physics") and am looking to see if I am correct in my...
  19. samjohnny

    Calculating distance to a star using magnitudes

    Homework Statement Homework Equations ##m = m_0 − 2.5 log_{10} f## where ##m## is the absolute magnitude of an object, and ##m_0## is the zero point. The Attempt at a Solution I'm having difficulty with is part b, the answer to which I believe is required for the subsequent parts. I...
  20. S

    Solving Eclipsing Binary Homework

    Homework Statement Two main sequence stars have the following properties: #1: apparent magnitude m_v=2.5, λ_eff = 551nm radius r=1.6R_sun #2: m_v = 5.77, r = 1.25R_sun 1) Calculate the apparent brightness of the system when #2 is in front of #1. Assuming that #1 has constant apparent...
  21. 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) ≈...
  22. P

    Calculating magnitudes of vectors

    1. Homework Statement Given the two vectors in the diagram, calculate their magnitudes if A+B-225j=0 Homework Equations sum of x component= Acos(42)--Bcos(56) sum of y component= Asin(42)+Bsin(56)--225j The Attempt at a Solution Find A and B use substitution A= [Bcos(56)]/cos(42) from x...
  23. G

    Why is impossible measurement of the magnitudes when his val

    Why is impossible measurement of the magnitudes when his values are smaller than Planck units??
  24. Kerrigoth

    Calculating multiple magnitudes for induced electric field

    Let's say I place two different size conducting loops inside of a uniform magnetic field. For the sake of the diagram I have the loops share a point, but just treat them as though they are not touching. Then I decrease the value of the magnetic field very quickly. \frac{dB}{dt} =...
  25. S

    Spectroscopic system, AB magnitudes

    Suppose we have a galaxy at redshift z=4 with monochromatic UV luminosity λUV *LUV = 4.2×1046 erg /s and an absolute K -band magnitude of K = −23.5 mag (in the AB system). Assuming a K -band absolute magnitude M⊙,AB = 5.14 for the sun, how can i determine the luminosity L_K of the galaxy ?? I...
  26. N

    Find the magnitudes of all of the forces acting on the sled

    Homework Statement A person pulls on a rope attached to a 5 kg sled. The rope makes an angle of 30 degrees with the horizontal. Sled accelerates horizontally at 1.7 m/s^2. There is no friction. Homework Equations ma = Fnet mg = Fgravity The Attempt at a Solution Fnorm = Earth force up on sled...
  27. S

    Rank Torque Magnitudes of 6 Forces on Door

    Homework Statement Six forces, each of magnitude either F or 2F, are applied to a door as seen from above in the figure. Rank in order, from smallest to largest, the six torques τ1to τ6 about the hinge. Homework Equations torque=RFsintheta The Attempt at a Solution τ1 = F*L/2 τ2 = 2F*L/4 τ3 =...
  28. entropy1

    Why do ket vectors not have magnitudes?

    Why does the magnitude of a ket vector not matter? The motivation appears to be that a state vector only can decribe a particle, or no particle. But why shouldn't the magnitude of ket vectors not be used to represent the density of the particles, the average number of particles? I'm am fairly...
  29. L

    Binary Stars and Apparent Magnitudes

    Homework Statement A binary star system at a distance of 85pc consists of two stars of equal luminosity that are so close together that they are observed in a telescope as a single image. If the apparent magnitude of the two stars combined is 10.7 what would be the apparent magnitude of just...
  30. T

    Magnitudes of Velocity and Acceleration

    Homework Statement I need to determine the magnitude of velocity and acceleration for an aircraft moving away from a fixed position (for example a radar station). I need to calculate the magnitude of velocity and acceleration for each time step. The following table of information is given...
  31. K

    Intro physics question involving magnitudes and vectors

    You’re hanging from a chinning bar, with your ;arms at right angles to each other. The magnitudes of the forces exerted by both your arms are the same, and together they exert just enough upward force to support your weight, 620 N. (a) Sketch the two force vectors for your arms, along with their...
  32. O

    Forces on Identical Bricks: Ranking Magnitudes

    Three identical bricks are pushed across a table at constant speed as shown. Rank the magnitudes of all the horizontal forces that you identified in your free body diagram. So I identified the horizontal forces of push, friction, system a on system b, and b on a. I understand the force will...
  33. Maxo

    Comparing Magnitudes of Forces on Two Boxes

    Homework Statement Two boxes have masses m1 and m2, and m2 is greater than m1. The boxes are being pushed across a frictionless horizontal surface. As the drawing shows, there are two possible arrangements, and the pushing force is the same in each. In which arrangement, (a) or (b), does the...
  34. G

    Mass and Tension: Comparing Magnitudes

    Homework Statement In the figure, M2 has more mass than M1 and M1 has more mass than M3. The questions refer to the magnitudes of tensions and weights. There is friction between the horizontal plane and M2 (μk ≠ 0). M2 is observed to travel at a constant speed. Assume that the pulleys are...
  35. B

    MHB Understanding How to Solve Vector Magnitudes and Angles

    I just don't understand others way solving this problem to solve for the unknown magnitudes of the two vectors I have to sum up all of the components in x and y and set them equal zero and from there I'll get some systems of equation. I saw a method where they let the x-component of AB and BE...
  36. N

    What is the magnitude of vector C in a balanced vector equation?

    Homework Statement Vector A has magnitude 3 and points to the right. Vector B has magnitude 4 and points vertically upwards. Find the magnitude of vector C such that A + B + C = 0 The Attempt at a Solution C = SQRT[4^2 + 5^2] = 6.4
  37. D

    Vector Magnitudes and projectile motion

    Homework Statement A plane traveling at a speed of 1300 km/h in a northernly direction at a height of 5 km above the the ground suddenly climbs at an angle of 45 degrees to to horizon. Maintaining the speed and angle it releases a projectile as it passes through 7 km in altitude. Find the...
  38. N

    Determine the magnitudes and directions of the currents in each R's.

    Homework Statement Determine the magnitudes and directions of the currents in each resistor shown in the figure. The batteries have emfs of ##\varepsilon_1 = 9.1## V and ##\varepsilon_2 = 11.6## V and the resistors have values of ##R_1 = 15 \Omega## , ##R_2 = 33 \Omega## , and ##R_3 = 30...
  39. N

    For this instant calculate the magnitudes of the force F and torque M

    Homework Statement The parallelogram linkage shown moves in the vertical plane with the uniform 6.8-kg bar EF attached to the plate at E by a pin which is welded both to the plate and to the bar. A torque (not shown) is applied to link AB through its lower pin to drive the links in a clockwise...
  40. D

    Finding the angle between two magnitudes.

    Consider two displacements, one of magnitude 3.3 m and another of magnitude 4.3 m. What angle between the directions of this two displacements give a resultant displacement of magnitude (a) 5.1 m, (b) 2.8 m, and (c) 4.7 m. Homework Equations I've been using the law of cosine to work out...
  41. N

    Unit Vector Magnitudes and Forces

    Homework Statement http://prntscr.com/p7dxt Here's a screenshot of the revision question. Homework Equations The Attempt at a Solution Co-ordinates of each point A, (0, 60, 0) B, (40, 0, 0) C, (-40, 0, 40) D, (-60, 0, -60) Position Vectors rAB, 40i + -60j + 0k rAC, -40i + -60j + 40k rAD...
  42. W

    Reaction Forces at Points A and B

    Homework Statement As shown, a roller at point A and a pin at point B support a uniform beam that has a mass 25.0 kg . The beam is subjected to the forces f1 = 50.0N and f2= 79.0N . The dimensions are l1= 0.750m and l2= 2.30m . (Figure 2) What are the magnitudes and of the reaction forces...
  43. A

    The sum of two vectors given magnitudes and included angle

    Homework Statement Given the magnitudes of vectors u and v and the angle θ between them, find sum of u + v. Give the magnitude to the nearest tenth when necessary and give the direction by specifying the angle that the resultant makes with u to the nearest degree. Homework Equations...
  44. S

    Is the Sun's luminosity in specific filters greater than its overall luminosity?

    I'm trying to calculate the luminosity of the sun in the infrared (J, H and K filters). According to http://mips.as.arizona.edu/~cnaw/sun.html, the absolute magnitudes of the Sun in each of these filters are J: 3.64 H: 3.32 K: 3.28. The absolute bolometric magnitude of the Sun is about...
  45. N

    Helmholtz Decomposition: Magnitude of Irrot. & Solenoidal Comp.

    Hi, Consider P = \boldsymbol{\nabla} f +\boldsymbol{\nabla}\times \bold{A} where f and A are scalar and vector potentials, respectively, and P is strictly positive and well behaved, and only nonzero in a domain \mathcal{D}. I want to find how the magnitude of \int \boldsymbol{\nabla} f dV...
  46. A

    How to solve a system of linear inequalities with absolute magnitudes?

    Hi everybody, I'd love to pick your brains about a problem in (seemingly?) linear algebra I've run into, trying to find the most efficient algorithm for solving a set of linear inequalities involving absolute magnitudes. During my research I've run into a problem that involves solving a...
  47. S

    Force F1 Resolved: Calculate Components & Magnitudes

    Homework Statement Resolve the force F1 into components acting along u and v axes and determine the magnitudes of the components. Refer to first attachment for full problem with diagram. Homework Equations asinθ bcosθ The Attempt at a Solution Please refer to attachments for attempt...
  48. S

    Finding the length of a vector given the magnitudes

    Homework Statement The question is as follows: if |m| = 4, |n| = 3, and the angle θ between m and n is 5pi/6, find the norm of the vector m + 2n. Homework Equations Im attempting to use the equation : cosθ = (m * n)/(|m||n|) The Attempt at a Solution I determined using the...
  49. C

    Binary stars apparent and absolute magnitudes

    Homework Statement A binary star system has two star of equal luminosity. The apparent magnitude of the two stars together is 11.2, and they are at a distance is 76pcs. How do I work out the apparent and absolute magnitudes of just one star? Homework Equations m=-2.5log(L)...
  50. W

    Constraining the element-wise magnitudes of a matrix

    I have a complex matrix, \textbf{A}, and I want to left-multiply it by a unitary matrix, \textbf{U} (i.e. \textbf{U} is square and \textbf{U}^H\textbf{U}=\textbf{I}). The goal is to find the \textbf{U} which yields the optimal solution \textbf{B}_{opt} \triangleq \textbf{U}\textbf{A}, where...