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# GCSE Astronomy

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1. (Original post by Ujjwal Dhakal)
The primary star was bigger compared to the star we were told to calculate. so i dont think we had to divide it by 2
It's a planet that we had to find out, not a star. A planet doesn't give off light
2. (Original post by Ujjwal Dhakal)
The primary star was bigger compared to the star we were told to calculate. so i dont think we had to divide it by 2
What? That wasn't a binary star system
3. (Original post by Gredore)
That was my initial thought, but what about the slopes on the graph? Surely you have to take into account the time from when it started to cross the star to the time it finished crossing. Which I think was 7.5 hours. I don't know though, it gave horrible numbers...

What did people get for the magnitude one?
i ignored that because i think it would be to diffulcult haha
4. I put the apparent retrograde motion of superior planets
5. (Original post by Andreahdlfuente)
Which magnitude one? For the Andromeda one I got 3.5 for the first and -1.5 for the second part
I can't remember exactly the question. But it was something about calculating the difference in luminosity and it gave us 2 magnitudes. It was on the binary star question I think.
6. Well according to everyone else's answers I messed up badly on the planet question
7. (Original post by Gredore)
I can't remember exactly the question. But it was something about calculating the difference in luminosity and it gave us 2 magnitudes. It was on the binary star question I think.
Omg that one was like 2.5^11
8. I just did 100*100*2.5 for that
9. (Original post by Andreahdlfuente)
Omg that one was like 2.5^11
I did the fifth root of 100 to the power of 11 (cos I like to be ridiculously accurate)
10. (Original post by Andreahdlfuente)
The diameter of the star is 9000000, not the diameter of the planet. The planet travels for 6 hours at 150,000km/h. Therefore it covers the star which is 9,000,000km in diameter. Since it takes away 50% of the light, then the planet must cover up 50% of the star. And 50% of the star is 9,000,000/2 which is 4,500,000.
Ooooh now it makes sense that you very much... shouldn't matter too much cause it's the only question I didn't answer and I think I jotted down 50% of star which should get a mark
11. I think I did fairly well I got a high B on my coursework and needed a high mark to get an A*. But the test was one of the hardest ones I have done compared to past paper. I think the grade boundaries will be low. That essay question shocked me as there haven't been one before. I think I did pretty well on the multi choice but the one about the two different magnitudes and the planet graph thing really got me. The mathy ones were okay, a couple trips but overall I think I did fairly well.
12. (Original post by Bearmail)
I think I did fairly well I got a high B on my coursework and needed a high mark to get an A*. But the test was one of the hardest ones I have done compared to past paper. I think the grade boundaries will be low. That essay question shocked me as there haven't been one before. I think I did pretty well on the multi choice but the one about the two different magnitudes and the planet graph thing really got me. The mathy ones were okay, a couple trips but overall I think I did fairly well.
Yeah the planet graph thing was hard... I remember panicking 2 minutes before the exam finished and jotting down 50% just to hedge my bets. The two magnitudes wasn't two bad, just inverse square law
13. In 2011 the A* was 89/120 and I found this paper a lot harder. I did last year's paper and got a high A but i resat this year to try to get an A* so praying for really low grade boundaries!!
14. Can someone explain to me how to find the apparent magnitude by changing the equation on the questions where they give you absolute mag? I got really confused there
15. you add the 5logd part to the absolute magnitude then take away 5 for apparent magnitude
16. (Original post by KayaTengiz)
Can someone explain to me how to find the apparent magnitude by changing the equation on the questions where they give you absolute mag? I got really confused there
Remember that 100kpc is 100,000 (or something like that, I don't remember exactly what it was. So you just stick everything into the equation. Put the M part in, and the d part into the log, which gives you 6 (I think). So it was like -21.5=m + 5 - (5x6), which is -21.5=m-25, so m is -21.5+25 which is 3.5.
17. (ಥ﹏ಥ) i thought that absolute magnitude was -21
18. (Original post by Tarick)
(ಥ﹏ಥ) i thought that absolute magnitude was -21
Yeah the absolute magnitude is -21.5, but it asked for the apparent magnitude
19. It was a much harder paper but overall I'm happy, coursework was a low A so I need a comfortable A* in the exam. Grade boundaries will be lower so fingers crossed
20. Did anyone get the graph were it said something like describe the curve but the graph was a straight line???

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