21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
6th Edition
ISBN: 9780393874921
Author: PALEN
Publisher: Norton, W. W. & Company, Inc.
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Chapter 20, Problem 24QP
To determine
Astronomers use X-ray, infrared, and 21-cm radio observations to probe the centre of the galaxy.
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The very first “image" of a black hole, at the centre of galaxy M87, was recently taken by the
Event Horizon Telescope (EHT). More accurately, EHT imaged radio emission from the disc
of gas that orbits the black hole with a lack of emission from the centre being attributed to
the black hole. This image was only possible because EHT is not a single radio telescope, but
is in fact a network of telescopes from around the world that take advantage of something
known as interferometry. Interferometry is a method for combining the light from multiple
telescopes, which results in an image that could have been taken by a telescope that has a
diameter equal to the distance between the telescopes referred to as the "“baseline"-rather
than the size of each individual telescope. EHT in particular combines observations from
several Very Long Baseline Interferometry (VLBI) stations in order to achieve a high angular
resolution.
(a) Given that the "baseline" of EHT is effectively the diameter of the…
The very first "image" of a black hole, at the centre of galaxy M87, was recently taken by the
Event Horizon Telescope (EHT). More accurately, EHT imaged radio emission from the disc
of gas that orbits the black hole with a lack of emission from the centre being attributed to
the black hole. This image was only possible because EHT is not a single radio telescope, but
is in fact a network of telescopes from around the world that take advantage of something
known as interferometry. Interferometry is a method for combining the light from multiple
telescopes, which results in an image that could have been taken by a telescope that has a
diameter equal to the distance between the telescopes-referred to as the “baseline"-rather
than the size of each individual telescope. EHT in particular combines observations from
several Very Long Baseline Interferometry (VLBI) stations in order to achieve a high angular
resolution.
(a) Given that the "baseline" of EHT is effectively the diameter of the…
You observe the H-alpha line of Hydrogen in a distant galaxy to have a wavelength of 918.4 nm. What is the radial velocity of the galaxy?
Chapter 20 Solutions
21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
Ch. 20.1 - Prob. 20.1CYUCh. 20.2 - Prob. 20.2CYUCh. 20.3 - Prob. 20.3CYUCh. 20.4 - Prob. 20.4CYUCh. 20 - Prob. 1QPCh. 20 - Prob. 2QPCh. 20 - Prob. 3QPCh. 20 - Prob. 4QPCh. 20 - Prob. 5QPCh. 20 - Prob. 6QP
Ch. 20 - Prob. 7QPCh. 20 - Prob. 8QPCh. 20 - Prob. 9QPCh. 20 - Prob. 10QPCh. 20 - Prob. 11QPCh. 20 - Prob. 12QPCh. 20 - Prob. 13QPCh. 20 - Prob. 14QPCh. 20 - Prob. 15QPCh. 20 - Prob. 16QPCh. 20 - Prob. 17QPCh. 20 - Prob. 18QPCh. 20 - Prob. 19QPCh. 20 - Prob. 20QPCh. 20 - Prob. 21QPCh. 20 - Prob. 22QPCh. 20 - Prob. 23QPCh. 20 - Prob. 24QPCh. 20 - Prob. 25QPCh. 20 - Prob. 26QPCh. 20 - Prob. 27QPCh. 20 - Prob. 28QPCh. 20 - Prob. 29QPCh. 20 - Prob. 30QPCh. 20 - Prob. 31QPCh. 20 - Prob. 32QPCh. 20 - Prob. 33QPCh. 20 - Prob. 34QPCh. 20 - Prob. 35QPCh. 20 - Prob. 36QPCh. 20 - Prob. 37QPCh. 20 - Prob. 38QPCh. 20 - Prob. 39QPCh. 20 - Prob. 40QPCh. 20 - Prob. 41QPCh. 20 - Prob. 42QPCh. 20 - Prob. 43QPCh. 20 - Prob. 44QPCh. 20 - Prob. 45QP
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- You observe the H-beta line of Hydrogen in a distant galaxy to have a wavelength of 558.9 nm. What is the radial velocity of the galaxy?arrow_forwardAmong the globular clusters orbiting a distant galaxy, one is moving at 534 km/s and is located 14 kpc from the center of the galaxy. Assuming the globular cluster is located outside most of the mass of the galaxy, what is the mass of the galaxy? Convert your answer to solar masses. (Hint: Use the formula for circular velocity, Vc = GM r ; make sure you convert relevant quantities to units of meters, kilograms, and seconds. Note: 1 pc = 3.1 ✕ 1016 m.)arrow_forwardLooking for ___Mpcarrow_forward
- The figure below shows the spectra of two galaxies A and B.arrow_forwardAmong the globular clusters orbiting a distant galaxy, one is moving at 417 km/s and is located 16 kpc from the center of the galaxy. Assuming the globular cluster is located outside most of the mass of the galaxy, what is the mass of the galaxy? Convert your answer to solar masses. (Hint: Use the formula for circular velocity, V, = V GM ; make sure you convert relevant quantities to units of meters, kilograms, and seconds. Note: 1 pc = 3.1 x 1016 m.) solar masses (M.)arrow_forwardThe Sun orbits the center of the Galaxy in 225 million years at a distance of 26,000 light-years. Given that a3=(M1+M2)P2 , where a is the semimajor axis and P is the orbital period, what is the mass of the Galaxy within the Sun’s orbit?arrow_forward
- Suppose three stars lie in the disk of the Galaxy at distances of 20,000 light-years, 25,000 light-years, and 30,000 light-years from the galactic center, and suppose that right now all three are lined up in such a way that it is possible to draw a straight line through them and on to the center of the Galaxy. How will the relative positions of these three stars change with time? Assume that their orbits are all circular and lie in the plane of the disk.arrow_forwardThe center of a faint but active galaxy has magnitude 26. How much less bright does it look than the very faintest star that our eyes can see, roughly magnitude 6?arrow_forwardWhy does the disk of a spiral galaxy appear dark when viewed edge on?arrow_forward
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