Measuring the sizes of stars: fringe benefits of interferometry

Nityananda, Rajaram (2017) Measuring the sizes of stars: fringe benefits of interferometry. Resonance : Journal of Science Education, 22 (7). pp. 645-657. ISSN 0973-712X

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Stars, other than the Sun, appear to our unaided eyes as points of light. Large telescopes show an image whose size is dictated by refractive index irregularities in the Earth’s atmosphere. The size of this blurring is much greater than that of the star, and hence it is difficult to measure the stellar size. Fizeau showed how one might overcome this limitation using the two-slit interference technique. It was Michelson who carried out this programme and made the first direct measurement of the giant star Betelguse in the constellation of Orion. His value for the angular diameter, 47 milliarcseconds or 2.6×10−7 radians, was completely confirmed by later work following his methods. The key concept introduced was ‘fringe visibility’, which turned out to be very fruitful in the later development of optics as well as astronomy.

Item Type: Article
Authors: Nityananda, Rajaram
Uncontrolled Keywords: Fringes interference spectral lines interferometer Fizeau mask angular size parallax
Subjects: Natural Sciences > Astronomy & allied sciences
Natural Sciences > Physics
Divisions: Azim Premji University > School of Arts and Sciences
Full Text Status: Public
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