FINAL STAGE 2024
Mfantsipim School: 47 points (Winner)
St. Augustine's College: 46 points (1st Runner-up)
Keta Senior High Technical School (Keta SHTS): 33 points (2nd Runner-up)
ROUND 2 - SPEED RACE
QUESTION
2024 PT5 has magnitude 22.
State the property of 2024 PT5 that is measured by its magnitude, and rank in increasing order of that property: 2024 PT5, a magnitude 11 object, and Pluto.
ANSWER: The property is brightness (measured by apparent magnitude — the brighter the object, the lower its magnitude number). Increasing order of brightness: 2024 PT5, Pluto, magnitude 11 object
SOLUTION:
The astronomical magnitude scale is inverse and logarithmic: smaller (or more negative) magnitude means a brighter object. 2024 PT5 (magnitude 22) is the dimmest of the three, Pluto (average apparent magnitude ≈14) is brighter, and the magnitude-11 object is brightest, since $11<14<22$.
So brightness increases in the order 2024 PT5 → Pluto → the magnitude 11 object.
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PRACTICE QUESTIONS
1. QUESTION: State the property of a heavenly body measured by its apparent magnitude, and rank in increasing order of brightness: star P (apparent magnitude 4.5), star Q (apparent magnitude −1.2) and star R (apparent magnitude 2.3).
ANSWER: The property is brightness as seen from the Earth. Increasing order of brightness: star P, star R, star Q
SOLUTION:
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-1.2 < 2.3 < 4.5$, so from brightest to dimmest: star Q, star R, star P.
Increasing brightness runs from the dimmest to the brightest.
2. QUESTION: Rank in increasing order of brightness: the Sun, Sirius and the full Moon, as seen from the Earth.
ANSWER: Increasing order of brightness: Sirius, the full Moon, the Sun
SOLUTION:
Typical apparent magnitude of the Sun: −26.7.
Typical apparent magnitude of Sirius: −1.46.
Typical apparent magnitude of the full Moon: −12.7.
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-26.7 < -12.7 < -1.46$, so from brightest to dimmest: the Sun, the full Moon, Sirius.
Increasing brightness runs from the dimmest to the brightest.
3. QUESTION: Rank in decreasing order of brightness: object X (apparent magnitude 8.6), object Y (apparent magnitude 0.5) and object Z (apparent magnitude 13.2).
ANSWER: Decreasing order of brightness: object Y, object X, object Z
SOLUTION:
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$0.5 < 8.6 < 13.2$, so from brightest to dimmest: object Y, object X, object Z.
Decreasing brightness runs from the brightest to the dimmest.
4. QUESTION: Rank in decreasing order of brightness: Polaris, Venus at its brightest and Vega, as seen from the Earth.
ANSWER: Decreasing order of brightness: Venus at its brightest, Vega, Polaris
SOLUTION:
Typical apparent magnitude of Polaris: 1.98.
Typical apparent magnitude of Venus at its brightest: −4.6.
Typical apparent magnitude of Vega: 0.03.
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-4.6 < 0.03 < 1.98$, so from brightest to dimmest: Venus at its brightest, Vega, Polaris.
Decreasing brightness runs from the brightest to the dimmest.
5. QUESTION: Rank in increasing order of brightness: star A (apparent magnitude 1.5), star B (apparent magnitude 3.6), star C (apparent magnitude −0.7) and star D (apparent magnitude 5.2).
ANSWER: Increasing order of brightness: star D, star B, star A, star C
SOLUTION:
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-0.7 < 1.5 < 3.6 < 5.2$, so from brightest to dimmest: star C, star A, star B, star D.
Increasing brightness runs from the dimmest to the brightest.
6. QUESTION: Rank in increasing order of brightness: Neptune, Jupiter at its brightest and the Andromeda Galaxy, as seen from the Earth.
ANSWER: Increasing order of brightness: Neptune, the Andromeda Galaxy, Jupiter at its brightest
SOLUTION:
Typical apparent magnitude of Neptune: 7.8.
Typical apparent magnitude of Jupiter at its brightest: −2.9.
Typical apparent magnitude of the Andromeda Galaxy: 3.4.
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-2.9 < 3.4 < 7.8$, so from brightest to dimmest: Jupiter at its brightest, the Andromeda Galaxy, Neptune.
Increasing brightness runs from the dimmest to the brightest.
7. QUESTION: State the property of a heavenly body measured by its apparent magnitude, and rank in increasing order of apparent magnitude: a comet (apparent magnitude 6.8), a planet (apparent magnitude −2.1) and a star (apparent magnitude 1.2).
ANSWER: The property is brightness as seen from the Earth. Increasing order of apparent magnitude: a planet, a star, a comet
SOLUTION:
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-2.1 < 1.2 < 6.8$, so from brightest to dimmest: a planet, a star, a comet.
Increasing magnitude number runs from the brightest to the dimmest.
8. QUESTION: Rank in decreasing order of brightness: Pluto, Canopus, the full Moon and Polaris, as seen from the Earth.
ANSWER: Decreasing order of brightness: the full Moon, Canopus, Polaris, Pluto
SOLUTION:
Typical apparent magnitude of Pluto: 14.4.
Typical apparent magnitude of Canopus: −0.74.
Typical apparent magnitude of the full Moon: −12.7.
Typical apparent magnitude of Polaris: 1.98.
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-12.7 < -0.74 < 1.98 < 14.4$, so from brightest to dimmest: the full Moon, Canopus, Polaris, Pluto.
Decreasing brightness runs from the brightest to the dimmest.
9. QUESTION: Rank in increasing order of brightness: galaxy G (apparent magnitude 9.4), nebula N (apparent magnitude 5.8) and star S (apparent magnitude 11.6).
ANSWER: Increasing order of brightness: star S, galaxy G, nebula N
SOLUTION:
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$5.8 < 9.4 < 11.6$, so from brightest to dimmest: nebula N, galaxy G, star S.
Increasing brightness runs from the dimmest to the brightest.
10. QUESTION: Rank in decreasing order of brightness: asteroid K (apparent magnitude 17.5), star L (apparent magnitude 2.4), planet M (apparent magnitude −3.5) and star N (apparent magnitude 0.8).
ANSWER: Decreasing order of brightness: planet M, star N, star L, asteroid K
SOLUTION:
The magnitude scale is inverse: the smaller (or more negative) the magnitude, the brighter the object.
$-3.5 < 0.8 < 2.4 < 17.5$, so from brightest to dimmest: planet M, star N, star L, asteroid K.
Decreasing brightness runs from the brightest to the dimmest.
11. QUESTION: Which is brighter as seen from the Earth: a star of apparent magnitude −1.5 or a star of apparent magnitude 3.5?
ANSWER: The star of apparent magnitude −1.5
SOLUTION:
The smaller (more negative) the apparent magnitude, the brighter the star.
$-1.5 < 3.5$, so the magnitude −1.5 star is brighter.
12. QUESTION: What does a negative apparent magnitude tell us about a star?
ANSWER: The star is very bright as seen from the Earth
SOLUTION:
The magnitude scale is inverse, so negative magnitudes belong to the brightest objects in the sky, such as Sirius.