2012 Practice Astronomy Competition
BHSS – January 2012
1. Place the following objects in order of stellar evolutionary phase from least to most evolved:

Mira

T Tauri

Sirius B

RR Lyrae

NGC 2440
2. Place the following objects in order of distance from the Sun, from nearest to most distant:

CH Cyg

Kepler SNR

Messier 15

T Tauri

Sirius B

DEM L238 and L249
3. Place the following objects in order of size from smallest to largest in radius:

Mira

SNR 0509-67.5

Messier 15

T Tauri

Sirius B
4. Sirius B has a mass of approximately 1 solar mass. Sirius A and B orbit their common center of mass with a period of
50 years and a semi-major axis of 7.5”. The parallax of Sirius A is 0.38 arc seconds.

What is the distance to the binary pair in parsecs?

What is the mass of Sirius A?
5. The parallax of Mira is 0.0078 arc seconds and its angular diameter is 0.036 arc seconds. What is the diameter of Mira
in astronomical units?
6. The observed diameter of SNR 0509-67.5 is 23 light years, and the gas is expanding at a rate of 5000 km/second.
Assuming the gas has been expanding at a constant rate, how long ago did the supernova explosion occur?
7. The Hipparcos satellite measured the parallax of symbiotic variable star CH Cygni to be 0.0037 arc seconds. The star
reached a maximum apparent brightness of V=5.6 magnitudes in 1987. What was the absolute magnitude in 1987 and
what is the star’s distance modulus?
8. SN 1604, known as Kepler’s Supernova produced a supernova remnant that now measure 14 light years in diameter.
What is the expansion rate of the gas in the supernova remnant?
9. Tycho’s supernova was first observed in 1572. The expansion velocity of the gas is ~5000 km/sec. Since the
supernova remnant was discovered in 1952, it has expanded in radius at a rate of 0.25 arc seconds per year. What is the
distance to the Tycho SNR?
10. If a supernova were to occur in Messier 15, would it be likely to be a Type Ia or a Type II supernova, and why?
11. The Carina Nebula contains the star Eta Carina, one of the most massive stars in the Milky Way, with a mass of 100150 times the mass of the Sun. The star has an age of about 3 Myr. It’s radial velocity is about 25 km/sec. How far has it
moved from its place of origin?
12. Once the young star T Tauri settles onto the main sequence to begin hydrogen burning, approximately what range of
mass is it likely to be?
13. RR Lyrae is a pulsating variable star, with changes in both radius and temperature. It has a period of about 13 hours.
RR Lyrae has an average apparent magnitude of 7.1 and a parallax of 0.0037 arc seconds. An RR Lyrae star in the
globular cluster M15 has a similar period, but has an apparent magnitude of 15.8 . What is the distance modulus of M15?
What is the distance to M15 in parsecs?
14. What causes the repeated eruptions of the recurrent nova U Scorpii?
15. Why is BP Psc known as the “Cannibal Star” and what observations led astronomers to this conclusion?
16. The central star of NGC 2440 has a temperature of about 200,000K. At what wavelength does it emit the most
radiation? What phase of evolution preceded the current phase, and what will the star become next?
17. RJ J0808.3+1527 is a pair of white dwarf stars in orbit around their common center of mass. Each star has a mass of
about 0.5 times the mass of the Sun. The orbital period is 322 seconds and the semi-major axis of the orbit is
approximately 0.0005 AU. The orbit is decaying because of gravitational radiation, and the separation is decaying by
about 2 feet per day. How long will i be before the two stars merge?
18. The two supernova remnants DEM L238 and L249 are located in the Large Magellanic Cloud. What evidence
suggests that both of these supernovae were of Type Ia?