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Table 2 shows some properties of the four brightest stars in the constellation Canis Minor - AQA - A-Level Physics - Question 2 - 2019 - Paper 4
Question 2
Table 2 shows some properties of the four brightest stars in the constellation Canis Minor. Table 2 | Name | Apparent magnitude | Absolute magnitude | Spectra... show full transcript
Worked Solution & Example Answer:Table 2 shows some properties of the four brightest stars in the constellation Canis Minor - AQA - A-Level Physics - Question 2 - 2019 - Paper 4
Step 1
Discuss, with reference to the Hipparcos scale, why many star maps show only two stars in the constellation Canis Minor.
Answer
The Hipparcos scale categorizes stars based on their brightness, from the brightest being 1 down to 6 (which is generally only visible under good conditions). In Canis Minor, the two brightest stars, which are also used in star maps, are Gamma A and Gomeisa. Since Gamma A and HD 66141 are significantly dimmer than the brightest two stars, most star maps highlight only Gomeisa and Procyon, as they are often more visible.
Step 2
State and explain which star in Table 2 has the most prominent Hydrogen Balmer absorption lines.
Answer
Gomeisa, classified as a B class star, has the most prominent Hydrogen Balmer absorption lines. This is because B type stars have the right temperature range to ionize hydrogen atoms, allowing their spectrum to exhibit strong Balmer lines, which are transitions of electrons in hydrogen atoms.
Step 3
Deduce which star, Gamma A or HD 66141, has the larger diameter.
Answer
To deduce the larger diameter, we can use the Stefan-Boltzmann law, which states that luminosity (L) is proportional to the surface area (A) and the fourth power of the effective temperature (T):
Both stars have similar spectral classes (K), indicating they share a similar effective temperature. However, since Gamma A has a greater absolute magnitude (-0.50 compared to -0.13 for HD 66141), it implies that Gamma A is more luminous, and thus, using the Stefan-Boltzmann law, Gamma A has a larger diameter.
Step 4
Describe the main features of the radial velocity method in the detection of planets.
Answer
The radial velocity method involves measuring the Doppler shift in the spectrum of a star as it moves towards or away from the observer. When a planet orbits a star, it exerts a gravitational pull, causing the star to move slightly in response. This movement leads to periodic changes in the star's light spectrum due to the Doppler effect, where the light shifts to shorter wavelengths (blue shift) when the star moves closer and to longer wavelengths (red shift) when it moves away. By analyzing these shifts, astronomers can infer the presence of an orbiting planet, estimate its mass, and determine its orbital period.
Step 5
Calculate the distance from the Earth to Procyon. Give an appropriate unit for your answer.
Answer
To calculate the distance to Procyon, we can use the formula for distance modulus:
where:
- is the apparent magnitude (0.34),
- is the absolute magnitude (2.65), and
- is the distance in parsecs.
Rearranging the equation:
Plugging in the values:
Thus, the distance from Earth to Procyon is approximately 2.15 parsecs.