DIFFICULT LEVEL

Which of the following best describes the shape of the universe according to current cosmological models?

• Perfectly spherical

• Flat with possible curvature

• Hyperbolic

• Cylindrical

What is the Chandrasekhar limit, and why is it significant in stellar evolution?

• The minimum mass a star needs to become a supernova

• The maximum mass a white dwarf can have before collapsing into a neutron star or black hole

• The temperature required for nuclear fusion to begin in a star

• The distance a planet must be from its star to have liquid water

Which of these methods is used to detect exoplanets?

• Transit method

• Doppler shift (radial velocity)

• Direct imaging

• All of the above

What is the primary force counteracting gravity inside a main-sequence star?

• Magnetic pressure

• Nuclear fusion pressure

• Radiation pressure

• Electron degeneracy pressure

What is the Roche limit, and why is it important?

• The distance where a planet's gravity is too weak to hold a moon

• The minimum distance a satellite must maintain before being torn apart by tidal forces

• The maximum radius of a black hole's event horizon

• The point at which a star stops nuclear fusion

What is the significance of the Schwarzschild radius of a black hole?

• It marks the distance where the gravitational force is strongest

• It defines the event horizon beyond which nothing can escape

• It is the radius of the singularity inside a black hole

• It measures the spin rate of a black hole

A planet orbits a star at a distance of 5 AU. Using Kepler’s Third Law, determine its orbital period. (Assume the mass of the star is equal to the Sun's.)

• 5 years

• 11.2 years

• 25 years

• 7.5 years

If the parallax angle of a star is 0.2 arcseconds, how far away is it in parsecs?

• 2 pc

• 5 pc

• 10 pc

• 50 pc

A distant galaxy is moving away from Earth at 60,000 km/s. If the rest wavelength of hydrogen’s H-alpha line is 656.3 nm, what is the observed wavelength due to redshift?

• • 670.3 nm

• 656.3 nm

• 668.1 nm

• 675.0 nm

Which indigenous Filipino group is known for using the position of the Pleiades (Moroporo) to determine the best time for planting?

• Ifugao

• Tagbanua

• Manobo

• Subanen