ASP Observational Techniques and Telescopes 1 — Questions and Answers
Question 1: What is the main advantage of a reflecting telescope over a refracting telescope?
- Reflectors are cheaper to manufacture
- Reflectors avoid chromatic aberration and can be made larger without distortion (Correct answer)
- Reflectors have better color contrast
- Reflectors are more portable
Correct answer: Reflectors avoid chromatic aberration and can be made larger without distortion
Reflecting telescopes use mirrors instead of lenses, which eliminates chromatic aberration (color fringing) and allows construction of very large, structurally supported mirrors that could not be achieved with glass lenses.
Question 2: What is the purpose of adaptive optics in ground-based astronomy?
- To magnify faint objects digitally
- To correct for atmospheric distortion in real-time, producing sharper images (Correct answer)
- To block out bright stars to reveal nearby planets
- To extend the wavelength range of optical telescopes
Correct answer: To correct for atmospheric distortion in real-time, producing sharper images
Adaptive optics systems use deformable mirrors controlled by computers to compensate for atmospheric turbulence in real-time, allowing ground-based telescopes to achieve near-diffraction-limited resolution.
Question 3: What is the resolving power of a telescope?
- The maximum magnification achievable
- The ability to distinguish two closely spaced objects as separate (Correct answer)
- The brightness of the image produced
- The range of wavelengths the telescope can detect
Correct answer: The ability to distinguish two closely spaced objects as separate
Resolving power (or angular resolution) is a telescope's ability to distinguish fine details or two closely spaced objects as separate, determined by aperture size and observing wavelength via the Rayleigh criterion.
Question 4: What is interferometry in radio astronomy?
- A technique to filter out radio frequency interference from satellites
- Combining signals from multiple separated telescopes to achieve the resolution of a much larger single dish (Correct answer)
- Using interference patterns to measure stellar distances
- A calibration method for individual radio dishes
Correct answer: Combining signals from multiple separated telescopes to achieve the resolution of a much larger single dish
Radio interferometry combines signals from multiple telescopes spread over large baselines to produce angular resolution equivalent to a single telescope the size of the baseline separation, achieving incredible detail.
Question 5: What is the transit method of exoplanet detection?
- Detecting the wobble a planet causes in its host star
- Measuring the dimming of a star's brightness as a planet passes in front of it (Correct answer)
- Using gravitational lensing to detect planetary companions
- Direct imaging of planets around nearby stars
Correct answer: Measuring the dimming of a star's brightness as a planet passes in front of it
The transit method detects exoplanets by measuring the small, periodic decrease in a star's brightness as an orbiting planet passes between the star and the observer, blocking a fraction of the starlight.
Question 6: What is spectroscopy used for in astronomy?
- Measuring the angular diameters of stars
- Analyzing the spectrum of light to determine composition, temperature, velocity, and other properties (Correct answer)
- Taking high-resolution images of solar system objects
- Measuring the polarization of light from stars
Correct answer: Analyzing the spectrum of light to determine composition, temperature, velocity, and other properties
Spectroscopy splits light into its component wavelengths, producing spectra with characteristic absorption or emission lines that reveal a celestial object's chemical composition, temperature, radial velocity, and more.
ASP Observational Techniques and Telescopes 1
What is the main advantage of a reflecting telescope over a refracting telescope?