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USAAAO — 2014 National Astronomy Olympiad
Question 1
Which of the following constellations are visible during the summer?
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 2
Which stars make up the Winter Triangle asterism?
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 3
The moon is at its upper culmination at 8pm, mean solar time. Estimate the phase of the moon.
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 4
Arrange the following stages of the life cycle of a star of one solar mass in chronological order - Red-giant branch, Pl...
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 5
How are the rings of Saturn thought to be formed?
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 6
The James Webb Space Telescope is to be sent to the second Lagrange point of the Earth-Sun system. What is the significa...
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 7
Which of the following is not a possible method of detecting exoplanets?
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 8
An 8 inch Dobsonian telescope with a focal ratio of f/6 is used with a 12mm Plossel eyepiece. Calculate the magnifying p...
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 9
Approximately how much higher is the limiting magnitude of a telescope than that of the human eye? Assume that the teles...
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 10
What is the advantage of an Equatorial telescope mount as compared to an Alt-az mount?
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 11
Alberio (β Cygni) is a double star system in the constellation Cygnus. The magnitudes of the component stars Alberio A &...
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 12
Which of the following stars is circumpolar in Romania (44°25'N 26°06'E)? (Circum-polar stars are stars that never set).
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 13
Haley's comet last appeared in the night sky in 1986. The Perihelion and Aphelion of its orbit are given by 0.586AU & 35...
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 14
What would be the maximum speed of a meteor on a parabolic orbit around the sun, whose point of closest approach is 1AU?
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 15
Estimate the lifespan of the Sun. (Mass of H : 1.00794u; Mass of He : 4.002602u)
Open questionUSAAAO — 2014 National Astronomy Olympiad
Question 16
Calculate the length of the shortest day that can be experienced in Romania (44°25'N 26°06'E). (Earth's axial tilt is 23...
Open questionUSAAAO — 2015 Practice Round
Question 1
Light from distant galaxies appears to be:
Open questionUSAAAO — 2015 Practice Round
Question 2
Given a star of 70 solar masses and 20 solar radii, what type of star is this?
Open questionUSAAAO — 2015 Practice Round
Question 3
The Sun has three major zones in its interior. What are these three zones, listed from center of the Sun outward?
Open questionUSAAAO — 2015 Practice Round
Question 4
The latitude and longitude of LA are 34.05 degrees N and 118.25 degrees W, respectively. A star at which of the followin...
Open questionUSAAAO — 2015 Practice Round
Question 5
The semi-major axis of an asteroid in the asteroid belt is 3 AU. What is its orbital period, in years?
Open questionUSAAAO — 2015 Practice Round
Question 6
What object is left at the middle of a planetary nebula, and what is the largest mass at which this object can exist?
Open questionUSAAAO — 2015 Practice Round
Question 7
The mean orbital velocity of Jupiter is 13.1 km/s, its mass is 1.9 × 10²⁷ kg, and its orbit has a semi-major axis of 7.9...
Open questionUSAAAO — 2015 Practice Round
Question 8
In a distant solar system, two planets, A and B, orbit a central main sequence star, like our sun. A day on Planet A las...
Open questionUSAAAO — 2015 Practice Round
Question 9
Which of the Solar System planets causes the “Kirkwood Gaps” found in the asteroid belt?
Open questionUSAAAO — 2015 Practice Round
Question 10
Calculate the escape velocity from a planet with twice the mass and 1/3 the radius of Earth.
Open questionUSAAAO — 2015 Practice Round
Question 11
Two neutron stars, each with a mass of 3 solar masses, merge to form a black hole. Assuming no mass is lost, find the ra...
Open questionUSAAAO — 2015 Practice Round
Question 12
What size telescope is needed to resolve Hellas Planitia (a 2,300 km wide crater) on Mars through a v-band filter (effec...
Open questionUSAAAO — 2015 Practice Round
Question 13
Fifteen minutes after sunset, you look west and see the moon rising. What phase is the moon in?
Open questionUSAAAO — 2015 Practice Round
Question 14
When taking the spectrum of a galaxy with redshift z=1, the H-alpha line (λ=656 nm) appears at what wavelength?
Open questionUSAAAO — 2015 Practice Round
Question 15
Which of the following Messier objects is grouped incorrectly with its type and constellation?
Open questionUSAAAO — 2015 Practice Round
Question 16
Star X has an apparent magnitude of 5.7 and is located 26.3 pc from the Sun. If there are 2.0 magnitudes of extinction t...
Open questionUSAAAO — 2015 Practice Round
Question 17
In a nearby star system, two stars are seen to orbit each other every 8 years. At their closest, the stars are 2” apart....
Open questionUSAAAO — 2015 Practice Round
Question 18
The Triangulum Galaxy has coordinates (RA: 1.564h, Dec: 30.660°). Which answer is closest to the local time at which it...
Open questionUSAAAO — 2015 Practice Round
Question 19
The peak wavelength of radiation from a certain star is 644 nm. If the absolute magnitude of this star is -0.17, what is...
Open questionUSAAAO — 2015 Practice Round
Question 20
Jupiter has a mass of 1.9 × 10²⁷ kg and a semimajor axis of 5.2 AU. Assume someone “out there” can resolve star position...
Open questionUSAAAO — 2015 First Round
Question 1
At arms length, the width of a fist typically subtends how many degrees of arc?
Open questionUSAAAO — 2015 First Round
Question 2
To have a lunar eclipse, the line of nodes must be pointing at the sun. The moon must also be in what phase?
Open questionUSAAAO — 2015 First Round
Question 3
Mars orbits the sun once every 687 days. Suppose Mars is currently in the constellation Virgo. What constellation will i...
Open questionUSAAAO — 2015 First Round
Question 4
To calculate the field of view of a telescope, you measure the time it takes Capella (RA:5.27h, dec:45.98°) to pass acro...
Open questionUSAAAO — 2015 First Round
Question 5
A telescope with focal length of 20 mm and aperture of 10 mm is connected to your smartphone, which has a CCD that measu...
Open questionUSAAAO — 2015 First Round
Question 6
What is its the resolution in arcseconds per pixel?
Open questionUSAAAO — 2015 First Round
Question 7
Comet 67P/Churyumov–Gerasimenko has an orbital period around the Sun of 6.44 years. What is its semimajor axis, in AU?
Open questionUSAAAO — 2015 First Round
Question 8
Which of the following techniques most directly constrains the mass of an exoplanet?
Open questionUSAAAO — 2015 First Round
Question 9
Which two properties of galaxies does the Tully-Fisher relation utilize a correlation between?
Open questionUSAAAO — 2015 First Round
Question 10
A binary star system has two components: Star A and Star B. Star A has a mass of 5 solar masses, and Star B has the same...
Open questionUSAAAO — 2015 First Round
Question 11
What is, approximately, the peak wavelength of electromagnetic radiation emitted by a star at a temperature of 5,000 K?
Open questionUSAAAO — 2015 First Round
Question 12
Stars A and B are observed over a period of 1 year. Both stars appear to move with respect to the background stars from...
Open questionUSAAAO — 2015 First Round
Question 13
Suppose that you measure the parallax angle for a particular star to be 0.25 arcsecond. The distance to this star is
Open questionUSAAAO — 2015 First Round
Question 14
On the main sequence, stars obtain their energy
Open questionUSAAAO — 2015 First Round
Question 15
Star A has a radius that is 2 times larger than the radius of star B, and a surface temperature that is 2 times smaller...
Open questionUSAAAO — 2015 First Round
Question 16
A and B, two main sequence stars of the same spectral class, have apparent magnitudes of 17 and 12, respectively. If sta...
Open questionUSAAAO — 2015 First Round
Question 17
Given that dark energy is vacuum energy, and that the densities of dark energy, dark matter and normal matter in the uni...
Open questionUSAAAO — 2015 First Round
Question 18
A type Ia supernova was observed in a galaxy with a redshift of 0.03. The supernova was determined to be 1.3 × 10⁸ pc aw...
Open questionUSAAAO — 2015 First Round
Question 19
In a main sequence star, gravitational collapse is counteracted by:
Open questionUSAAAO — 2015 First Round
Question 20
If the hydrogen alpha line of a star, normally 656.3 nm, is observed to be 662.5 nm, what is the star’s radial speed rel...
Open questionUSAAAO — 2015 First Round
Question 21
Within M-type stars, heat transfer occurs primarily through:
Open questionUSAAAO — 2015 First Round
Question 22
If a 1.2 solar mass star shows a radial velocity variation with a period of 9.2 days and amplitude of 32 m/s, estimate t...
Open questionUSAAAO — 2015 First Round
Question 23
Calculate the total angular distance swept by Venus (a = 0.7 AU) during the flight time of a probe completing a Hohmann...
Open questionUSAAAO — 2015 First Round
Question 24
Calculate the blackbody equilibrium temperature of Mars. Take Mars’s albedo to be 0.25 and semimajor axis to be 1.5 AU
Open questionUSAAAO — 2015 First Round
Question 25
Calculate the semimajor axis of a satellite orbiting the Earth with a velocity of 8.3 km/s at a distance of 300 km from...
Open questionUSAAAO — 2015 First Round
Question 26
On the night of December 23rd-24th 2015, an occultation of a bright star by the moon will be visible from Britain to Jap...
Open questionUSAAAO — 2015 First Round
Question 27
A synodic day on Mars is 24 hours and 40 minutes. If one Martian year is 687 earth-days, which of the following is close...
Open questionUSAAAO — 2015 First Round
Question 28
Suppose at the equator, a star passes through the zenith at local noon on the summer solstice. What is the right ascensi...
Open questionUSAAAO — 2015 First Round
Question 29
40 light years away, an exoplanet orbits a star of 5 solar masses every 14 years. Assuming this system has an inclinatio...
Open questionUSAAAO — 2015 First Round
Question 30
A planet orbits a star with a projected semimajor axis of 0.24”. What is the necessary aperture size of a telescope than...
Open questionUSAAAO — 2016 First Round
Question 1
All RR Lyrae variables have an absolute magnitude M of approximately 0.75. If an RR Lyrae star is observed with an appar...
Open questionUSAAAO — 2016 First Round
Question 2
If the closest distance from a planet to its host star is 1.50 AU and its farthest distance from its host star is 4.50 A...
Open questionUSAAAO — 2016 First Round
Question 3
A star exhibits periodic variations in brightness suggestive of a transiting companion. If the minimum stellar flux is 9...
Open questionUSAAAO — 2016 First Round
Question 4
Suppose you are on the surface of the Moon, and you want to launch an object into an elliptic orbit with a perilune of 1...
Open questionUSAAAO — 2016 First Round
Question 5
Estimate the minimum mass of a galaxy with a radius of 40,000 ly if stars at the edge of the galaxy orbit with a velocit...
Open questionUSAAAO — 2016 First Round
Question 6
Estimate the mass of an old globular cluster if the escape velocity at the edge of the cluster is 8.5 km/s. The cluster...
Open questionUSAAAO — 2016 First Round
Question 7
What delta V must an earth orbiting spacecraft apply to transfer from a 200 km parking orbit to a transfer orbit with an...
Open questionUSAAAO — 2016 First Round
Question 8
Suppose a probe has a velocity of 20 km/s when it’s 100 AU away from the Sun. What type of orbit is the probe on? The Su...
Open questionUSAAAO — 2016 First Round
Question 9
Phobos orbits around 9,376 km away from the center of its host planet, Mars, and has an orbital period of 8 hours. What...
Open questionUSAAAO — 2016 First Round
Question 10
Mercury’s orbit around the Sun has a semimajor axis of 0.387 AU. Knowing that the mass of the Sun is 1.99*10³⁰ kg and as...
Open questionUSAAAO — 2016 First Round
Question 11
Mercury’s orbit has a semimajor axis of 0.387 AU. What would be the maximum angular separation between Mercury and the S...
Open questionUSAAAO — 2016 First Round
Question 12
A geostationary satellite orbits Earth so that it appears at all times to be at the Zenith as viewed from a fixed point...
Open questionUSAAAO — 2016 First Round
Question 13
What would be the angular size of the sun as seen from Mars in arcminutes? Assume Mars orbits at a distance of 1.5 AU. (...
Open questionUSAAAO — 2016 First Round
Question 14
Only some stars rise (cross the horizon from below) due East (at Azimuth 90°). For an observer at Latitude 37°, Longitud...
Open questionUSAAAO — 2016 First Round
Question 15
On March 3, 2012, Mars experienced retrograde motion. The configuration of the Sun, Mars, and Earth that led to retrogra...
Open questionUSAAAO — 2016 First Round
Question 16
Suppose there are two main-sequence stars, A and B. Star A has a temperature of 10,000 K, while Star B has a temperature...
Open questionUSAAAO — 2016 First Round
Question 17
An active galactic nucleus is observed to produce a hydrogen emission line at 687.2 nm. The rest wavelength of this hydr...
Open questionUSAAAO — 2016 First Round
Question 19
Suppose the absolute magnitude of a star is 3.25. What would its apparent magnitude be as seen from a planet orbiting th...
Open questionUSAAAO — 2016 First Round
Question 20
Which of these is the correct sequence of events in the Universe, from earliest to latest?
Open questionUSAAAO — 2016 First Round
Question 21
Suppose a star has an absolute bolometric magnitude of -0.77 and a bolometric correction of -1.02. If it has an apparent...
Open questionUSAAAO — 2016 First Round
Question 22
A planet orbits a star with a temperature of 6500K and a radius of 1.2 solar radii at a distance of 1.5 A.U. The planet...
Open questionUSAAAO — 2016 First Round
Question 23
Which constellation is not on the Zodiac?
Open questionUSAAAO — 2016 First Round
Question 24
One of the constellations that will be visible in Bhubaneshwar, India (20° 16’ 20.67” N, 85° 50’ 1.85” E) in December 20...
Open questionUSAAAO — 2016 First Round
Question 25
Which of the following famous Messier objects is in the constellation Hercules?
Open questionUSAAAO — 2016 First Round
Question 27
Which of the following famous Messier objects is in the constellation Orion?
Open questionUSAAAO — 2016 First Round
Question 28
What is the brightest star in the constellation Taurus?
Open questionUSAAAO — 2016 First Round
Question 29
What is the brightest star in the constellation Perseus?
Open questionUSAAAO — 2016 First Round
Question 30
Which of these Messier objects is NOT in the constellation Auriga?
Open questionUSAAAO — 2016 First Round
Question 31
To which constellation does your previous response belong?
Open questionUSAAAO — 2016 First Round
Question 32
What type of object is M44?
Open questionUSAAAO — 2016 First Round
Question 33
To which constellation does M44 belong?
Open questionUSAAAO — 2016 First Round
Question 34
Which three stars make up the Summer Triangle?
Open questionUSAAAO — 2017 First Round
Question 1
What would be the radius of the Sun when it becomes a black hole (although the probability is almost zero)?
Open questionUSAAAO — 2017 First Round
Question 2
A comet called “SMukherjee2017” which has physical values of e = 0.12, a = 4AU was visible from the Earth in 2017. In wh...
Open questionUSAAAO — 2017 First Round
Question 3
What is the perihelion of comet “SMukherjee2017”?
Open questionUSAAAO — 2017 First Round
Question 4
A comet called “LQi2017” which has physical values of e = 1.2, a = 19AU was visible from the Earth in 2017. In which yea...
Open questionUSAAAO — 2017 First Round
Question 5
How far away is the horizon from you, when your height is about 5ft 11in (1.8m)? You are standing on a plain that has no...
Open questionUSAAAO — 2017 First Round
Question 6
Consider that the absolute magnitude of a star is m₀. Imagine that the first star gets split into N smaller identical st...
Open questionUSAAAO — 2017 First Round
Question 7
Taking the radius of the black hole to be the Schwarzschild radius (the radius at which the escape velocity of an object...
Open questionUSAAAO — 2017 First Round
Question 8
In 1974, Stephen Hawking proved that black holes emit blackbody radiation according to the Stefan-Boltzmann law (due to...
Open questionUSAAAO — 2017 First Round
Question 9
We observe that a quasar’s brightness varies within less than a day. What is the best upper bound on the quasar’s size t...
Open questionUSAAAO — 2017 First Round
Question 10
A student group from California Institute of Technology is planning a massive prank for this year. This year, they are p...
Open questionUSAAAO — 2017 First Round
Question 11
The MIT students have found out about the plans of the Caltech students of sending a rocket to fly a parachute above the...
Open questionUSAAAO — 2017 First Round
Question 12
The following series of photos were taken on March 17 around noon time (each photo taken about 3 minutes apart from the...
Open questionUSAAAO — 2017 First Round
Question 13
Imagine you are at the South Pole on December 21st. Which of these statements best describes your shadow on this day?
Open questionUSAAAO — 2017 First Round
Question 14
The USAAAO team successfully launched a satellite to be in the orbit within the boundary of the Solar System. The satell...
Open questionUSAAAO — 2017 First Round
Question 15
At which of the following phases of the Moon’s orbit is the tidal bulge of Earth largest?
Open questionUSAAAO — 2017 First Round
Question 16
A predicted (A) and observed (B) rotation curve of a typical spiral galaxy is shown below. What component of the galaxy...
Open questionUSAAAO — 2017 First Round
Question 17
What is a star burning in its core when it is on the horizontal branch?
Open questionUSAAAO — 2017 First Round
Question 18
What is the final stage in the evolution of a G1 star with mass of 1.1MSun?
Open questionUSAAAO — 2017 First Round
Question 19
The following graph shows spectral flux density as a function of wavelength for the 2 stars in a binary system. Assume t...
Open questionUSAAAO — 2017 First Round
Question 20
What is the ratio of the radius of the hotter star to that of the colder star?
Open questionUSAAAO — 2017 First Round
Question 21
Given that the apparent magnitude of the system is 8.2, what is the apparent magnitude of the brighter star?
Open questionUSAAAO — 2017 First Round
Question 22
Assuming that the radius of the smaller star is 2 solar radii, what is the distance to the system? [Answer choices updat...
Open questionUSAAAO — 2017 First Round
Question 23
Astronomers have observed the Cosmic Microwave Background (CMB) radiation. Which of these is a correct description of th...
Open questionUSAAAO — 2017 First Round
Question 24
Which is the correct chronological order of events?
Open questionUSAAAO — 2017 First Round
Question 25
Edwin Hubble published in 1929 the paper “A Relation Between Distance and Extragalactic Nebulae” explaining his find tha...
Open questionUSAAAO — 2017 First Round
Question 26
An astronomical interferometer is an array of separate radio telescope antennas that work together as a single telescope...
Open questionUSAAAO — 2017 First Round
Question 28
Choose the values (x, y, z) that would best complete the descriptions below for the 3 different types of twilights. i) c...
Open questionUSAAAO — 2017 First Round
Question 29
The Small Magellanic Cloud is located in the southeast corner of which of the following constellations:
Open questionUSAAAO — 2017 First Round
Question 30
Due to the precession of the equinoxes, the north and south celestial poles trace out circles on the celestial sphere wi...
Open questionUSAAAO — 2017 First Round
Question 31
What is the 13’th constellation that crosses the ecliptic, which is not included in the 12 zodiacal constellations?
Open questionUSAAAO — 2018 First Round
Question 1
A planet’s orbit around a star has a semimajor axis of 16 AU. What is the period of the planet’s orbit?
Open questionUSAAAO — 2018 First Round
Question 2
Which of the following has the longest wavelength?
Open questionUSAAAO — 2018 First Round
Question 3
What is the peak wavelength in Angstroms (Å) of electromagnetic radiation emitted by a star at a temperature of 10,000 K...
Open questionUSAAAO — 2018 First Round
Question 4
Determine the azimuth of Capella (Aurigae) in its upper culmination as seen from geographic latitude of φ = +45°58′.
Open questionUSAAAO — 2018 First Round
Question 5
From which geographic latitude does the star Antares (α Scorpii, δ = −26°19′) never rise?
Open questionUSAAAO — 2018 First Round
Question 6
For the following problem find the range in which the answer lies: on the day of summer solstice, on which geographic la...
Open questionUSAAAO — 2018 First Round
Question 7
For the following problem, find the range in which the answer lies: looking from Greenwich on February 10th (s₀ = 9h17m4...
Open questionUSAAAO — 2018 First Round
Question 8
What is the main energy transport process in the core of the Sun?
Open questionUSAAAO — 2018 First Round
Question 9
What are the bright regions on the solar photosphere called?
Open questionUSAAAO — 2018 First Round
Question 10
When seen from Earth, what is Venus’ phase when it is at greatest elongation?
Open questionUSAAAO — 2018 First Round
Question 11
Which planets have primary atmospheres?
Open questionUSAAAO — 2018 First Round
Question 12
Which of the following planets or dwarf planets has not been visited by a spacecraft?
Open questionUSAAAO — 2018 First Round
Question 13
Star A has a surface temperature of 10,000 K while Star B has a surface temperature of 4,000 K. Star B is 10 times large...
Open questionUSAAAO — 2018 First Round
Question 14
What property of the interiors of stars changes at the Kraft break, around 1.6 Solar masses?
Open questionUSAAAO — 2018 First Round
Question 15
Which of the following stages will our Sun not evolve through?
Open questionUSAAAO — 2018 First Round
Question 16
Which of the following are not high mass stars (relative to the others)?
Open questionUSAAAO — 2018 First Round
Question 17
On a Hertzsprung-Russell diagram, where would we find stars that are cool and dim?
Open questionUSAAAO — 2018 First Round
Question 18
What do the cores of low-mass and high-mass main-sequence stars have in common?
Open questionUSAAAO — 2018 First Round
Question 19
The thermal pressure of a gas depends on
Open questionUSAAAO — 2018 First Round
Question 20
What happens to the core of a star after a planetary nebula occurs?
Open questionUSAAAO — 2018 First Round
Question 21
Find the visual magnitude of the binary star α Piscium, given that the visual magnitudes of each component in the binary...
Open questionUSAAAO — 2018 First Round
Question 22
Which of the following is not a method used to detect exoplanets?
Open questionUSAAAO — 2018 First Round
Question 23
Which of the following type of planet was the first to be discovered around a Solar-type star?
Open questionUSAAAO — 2018 First Round
Question 24
A star of radius 0.72 solar radii experiences a periodic dip in brightness once every 13.8 days, thought to be a result...
Open questionUSAAAO — 2018 First Round
Question 25
The center of the Milky Way is a part of which zodiac constellation?
Open questionUSAAAO — 2018 First Round
Question 26
The youngest stars in the Milky Way are found predominantly in which part of the galaxy?
Open questionUSAAAO — 2018 First Round
Question 27
In the 1920s Harlow Shapely estimated the size of the Milky Way galaxy using which of the following?
Open questionUSAAAO — 2018 First Round
Question 28
What is the theoretical diffraction limited angular resolution in visible light (5,500 Å) of a typical 20-cm (8 in) amat...
Open questionUSAAAO — 2018 First Round
Question 29
To improve the angular resolution of a telescope one must
Open questionUSAAAO — 2018 First Round
Question 30
Find the total sum of the binary system of the star Capella, if semi-major axis between them is 0.85 AU, and period of 0...
Open questionUSAAAO — 2019 First Round
Question 1
Which of the following relates the intrinsic luminosity of a spiral galaxy with its asymptotic rotation velocity?
Open questionUSAAAO — 2019 First Round
Question 2
Which of the following correctly gives the location of Population I vs. Population II stars in the Milky Way?
Open questionUSAAAO — 2019 First Round
Questions 3–4
A quasar with a bolometric flux of approximately 10⁻¹² erg s⁻¹ cm⁻² is observed at a redshift of 1.5, i.e. its comoving...
Open questionUSAAAO — 2019 First Round
Question 5
An observer is standing atop the Burj Khalifa, the tallest building on Earth (height = 830 m, latitude = 25.2 N, longitu...
Open questionUSAAAO — 2019 First Round
Question 6
Which of the following is closest to the ratio of the farthest distance to the horizon that can be seen by an observer s...
Open questionUSAAAO — 2019 First Round
Question 7
An observer measures the blackbody spectrum for a variety of bodies as a function of temperature and wavelength in the l...
Open questionUSAAAO — 2019 First Round
Question 8
Suppose a spacecraft were orbiting in a low Earth orbit at an altitude of 400 km. The spacecraft makes a single orbital...
Open questionUSAAAO — 2019 First Round
Question 9
After entering Mars orbit, a spacecraft finds that over the course of the Martian year, the position of Star A varies by...
Open questionUSAAAO — 2019 First Round
Question 10
Star A, of mass 3.5 M☉, shows radial-velocity variations 24.2 m/s in amplitude and 23.22 years in period, suggesting the...
Open questionUSAAAO — 2019 First Round
Question 11
Whether or not a diffraction-limited optical system can resolve two points as distinct can be determined by the Rayleigh...
Open questionUSAAAO — 2019 First Round
Question 12
The celestial coordinates of the Orion Nebula are RA 05h35m, dec −05°23′. Which of the following is closest to the time...
Open questionUSAAAO — 2019 First Round
Question 13
A yellow hypergiant located 1.04 kpc away has an apparent visual magnitude of 1.49 and a B − V color excess of 0.29. Ass...
Open questionUSAAAO — 2019 First Round
Question 14
The pp chain is a primary energy generation mechanism in the Sun. Each run of the process 2H + e → D + ν releases 26.73...
Open questionUSAAAO — 2019 First Round
Question 15
A relation between which of the following pairs of properties of Cepheid variables makes Cepheid variables, specifically...
Open questionUSAAAO — 2019 First Round
Question 16
Assuming that the Chandrasekhar Limit is 1.4 Solar masses, estimate the maximum average density (in kg/m³) of a Chandras...
Open questionUSAAAO — 2019 First Round
Question 17
The Sun’s differential rotation can be estimated with the equation ω = X + Y sin²(φ) + Z sin⁴(φ), where ω is angular vel...
Open questionUSAAAO — 2019 First Round
Question 18
An observer generates a light curve of a binary system and notices two different minima that repeat periodically in alte...
Open questionUSAAAO — 2019 First Round
Question 19
Eltanin, the brightest star in Draco, has approximate coordinates RA 17h56m, Dec +51.5°. Given that at the observer’s lo...
Open questionUSAAAO — 2019 First Round
Question 20
Stellar bodies located in the top left of a Hertzsprung-Russell diagram necessarily have which properties?
Open questionUSAAAO — 2019 First Round
Question 21
Which of the following correctly orders the following distance indicators from the smallest to largest scale?
Open questionUSAAAO — 2019 First Round
Question 22
As seen from Mars, what phase will Earth appear to be in when Mars is at quadrature from Earth?
Open questionUSAAAO — 2019 First Round
Question 23
Which of the following stars is almost always never visible to observers in the Northern hemisphere?
Open questionUSAAAO — 2019 First Round
Question 24
Two amateur astronomers A and B living in Ecuador are standing on the Equator at the Galapagos Islands (height 0 m, long...
Open questionUSAAAO — 2019 First Round
Question 25
The spectra of two stars A and B peak at wavelengths 500 nm and 250 nm respectively. What is the ratio of their luminosi...
Open questionUSAAAO — 2019 First Round
Question 26
Two stationary observers at a distance 100 AU from the Sun observe transits of Mercury across the diameter of the Sun’s...
Open questionUSAAAO — 2019 First Round
Question 27
Find the total sum of the binary system of the star Capella, if semi-major axis between them is 0.85 AU, and period of 0...
Open questionUSAAAO — 2019 First Round
Question 28
The New Horizons spacecraft completed a flyby of 2014 MU69 on New Year’s Day of this year. 2014 MU69 is a Kuiper Belt Ob...
Open questionUSAAAO — 2019 First Round
Question 29
HD 209458b is an extrasolar gas giant planet with a radius of 1.38 Jupiter radii and a mass of 0.69 Jupiter masses (1 Ju...
Open questionUSAAAO — 2019 First Round
Question 30
Imagine that our Sun was suddenly replaced by an M-dwarf with a mass half that of the Sun. If Earth kept the same semima...
Open questionUSAAAO — 2020 First Round
Question 1
The spectrum of a blackbody peaks at a wavelength inversely proportional to its temperature. This is known as Wein’s law...
Open questionUSAAAO — 2020 First Round
Question 2
Calculate the speed of the Sun around the center of mass due to the presence of Jupiter.
Open questionUSAAAO — 2020 First Round
Question 3
Hα is a prominent absorption line in the Sun’s spectrum with λ = 656.281 nm. For an observer on α-Centauri, assuming the...
Open questionUSAAAO — 2020 First Round
Question 4
Why does helium burn much faster than hydrogen in a star?
Open questionUSAAAO — 2020 First Round
Question 5
The Earth’s rotation axis happens to be pointing almost exactly at Polaris now, but Polaris will not always be the North...
Open questionUSAAAO — 2020 First Round
Question 6
A 13 kg telescope is mounted on a tripod such that the angle between tripod legs is 30°. How much is the force exerted o...
Open questionUSAAAO — 2020 First Round
Question 7
Capella, the brightest star in Auriga, has celestial coordinates 05h18m12.78s, +46°00′59.8″. At midnight local solar tim...
Open questionUSAAAO — 2020 First Round
Question 8
Kerbyn is a small rocky planet in a circular orbit around a 0.2 M☉ star with a semimajor axis of 0.1 AU. Kerbyn has an a...
Open questionUSAAAO — 2020 First Round
Question 9
Which of the following is responsible for the opacity of the Sun’s photosphere?
Open questionUSAAAO — 2020 First Round
Question 10
Planet Nine is a hypothetical planet in the outer Solar System, with a semimajor axis between 400 and 800 AU. Which of t...
Open questionUSAAAO — 2020 First Round
Question 11
The main reason why Io is volcanically active is due to:
Open questionUSAAAO — 2020 First Round
Question 12
Knowing that the distance between the Sun and Uranus is 2.87 × 10⁹ km and Uranus’ rotation period is 17h 14 min, determi...
Open questionUSAAAO — 2020 First Round
Question 13
The angular diameter of star A with apparent bolometric magnitude 2 is 2.5 times greater than the angular diameter of st...
Open questionUSAAAO — 2020 First Round
Question 14
As a consequence of the virial theorem, how does the stellar temperature (T) change if we add more arbitrary energy (E)...
Open questionUSAAAO — 2020 First Round
Question 15
How do we increase the reaction time for hydrogen fusion at the stellar core leaving other factors unchanged?
Open questionUSAAAO — 2020 First Round
Question 18
Recently, the exoplanet Proxima Centauri b was discovered using the radial-velocity method. Its orbital period is 11.19...
Open questionUSAAAO — 2020 First Round
Question 19
Proxima Centauri b has an orbital period of 11.19 days and orbits Proxima Centauri, which has a mass of 0.122 Solar mass...
Open questionUSAAAO — 2020 First Round
Question 20
A star cluster with a main-sequence turn-off at around 6000 K effective temperature is about:
Open questionUSAAAO — 2020 First Round
Question 21
The 21 cm absorption line is a tracer for what kind of gas?
Open questionUSAAAO — 2020 First Round
Question 22
From the shortest distances to the longest, what is the correct order of distance determination techniques?
Open questionUSAAAO — 2020 First Round
Question 23
In a particular compact binary system consisting of a black hole and a main sequence star, the black hole has a mass of...
Open questionUSAAAO — 2020 First Round
Question 25
The Hα line (λ₀ = 656.28 nm) of a galaxy is observed to be redshifted to λ = 814.35 nm. Assuming only cosmological redsh...
Open questionUSAAAO — 2020 First Round
Question 26
At what redshift would the average temperature in the universe have been hot enough to emit 1 nm photons? The current CM...
Open questionUSAAAO — 2020 First Round
Question 27
In April, the Event Horizon Telescope released the first image of the supermassive black hole of M87. The black hole has...
Open questionUSAAAO — 2020 First Round
Question 28
At optical wavelengths, star formation is strongly obscured by dust. Studies of protoplanetary disks therefore usually o...
Open questionUSAAAO — 2020 First Round
Question 29
A very curious astronomer decided to cover the left half of the objective lens of a telescope with opaque material. If h...
Open questionUSAAAO — 2021 First Round
Question 1
On December 21, 2020, Jupiter was at (α, δ) = (20h 10m, −20° 34′). Which constellation was Saturn in?
Open questionUSAAAO — 2021 First Round
Question 2
What is the spectral type of a star with a luminosity of 5.86 × 10^26 W and radius of 8.51 × 10^8 m?
Open questionUSAAAO — 2021 First Round
Question 3
The exoplanet HD 209458b has a mass of 0.71 Jupiter masses and orbits HD 209458 with an orbital period of 3.53 days. HD...
Open questionUSAAAO — 2021 First Round
Question 4
The photon number density of a blackbody depends on temperature as n_d = a (k_B T / ħc)^n, where k_B is the Boltzmann co...
Open questionUSAAAO — 2021 First Round
Question 5
HD 209458b has a radius of 1.35 Jupiter radii, while the radius of HD 209458 is 1.20 Solar radii. What is the transit de...
Open questionUSAAAO — 2021 First Round
Question 6
Which of the following is a problem of the conventional Big Bang theory that is resolved by the theory of inflation?
Open questionUSAAAO — 2021 First Round
Question 7
Comet C/2020 F3 (NEOWISE) last reached perihelion on July 3, 2020. Comet NEOWISE has an orbital period of ≈ 4400 years a...
Open questionUSAAAO — 2021 First Round
Question 8
An astronomer detected a galaxy and decided to analyze its different parts and physical aspects. The frequency generated...
Open questionUSAAAO — 2021 First Round
Question 9
A stable open cluster of about N = 1000 Sun-like stars has an angular diameter of θ = 60 arcminutes and distance d = 500...
Open questionUSAAAO — 2021 First Round
Question 10
What would happen to the analemma of the Sun if the obliquity of the Earth's orbit suddenly went to zero degrees and its...
Open questionUSAAAO — 2021 First Round
Question 11
Let Td,C and Td,S be the temperatures at the core and the surface of the sun, respectively. Similarly, let TA,C and TA,S...
Open questionUSAAAO — 2021 First Round
Question 12
The spectral line Hα in the spectrum of a star is recorded as having displacement of ∆λ = 0.043 × 10^-10 m. At rest, the...
Open questionUSAAAO — 2021 First Round
Question 13
The reflector telescope built by Sir Issac Newton was a f/5 telescope and had a primary mirror of diameter 30mm. He used...
Open questionUSAAAO — 2021 First Round
Question 14
Take a look at the following image: Three Messier objects are circled in the image. Select the alternative that correctl...
Open questionUSAAAO — 2021 First Round
Question 15
An interesting phenomena that happens in the Solar System is the capture of comets in the interstellar medium. Assume th...
Open questionUSAAAO — 2021 First Round
Question 16
In a certain day, when it is 0h UT, the sidereal time of Prime Meridian is 5h 56min 9.4s. For this day, with start and e...
Open questionUSAAAO — 2021 First Round
Question 17
Consider the following horrifying scenario. The Sun has become a Red Giant, and its radius is doubling every 100 years....
Open questionUSAAAO — 2021 First Round
Question 18
TESS Object of Interest (TOI) 402.01 has an orbital period of 4.756 ± 0.000023 (days) and was last observed to transit o...
Open questionUSAAAO — 2021 First Round
Question 19
Jupiter has a mass of 1.90 × 10^27 kg and a radius of 7.15 × 10^7 m. To the closest order of magnitude, estimate the pre...
Open questionUSAAAO — 2021 First Round
Question 20
Which of the following statements is wrong?
Open questionUSAAAO — 2021 First Round
Question 21
Consider a horizontal sundial where the triangular gnomon rises at an angle equal to the sundial site's latitude, φ = 38...
Open questionUSAAAO — 2021 First Round
Question 22
Consider an eclipsing binary star system observed (in some fixed band) to have a combined apparent magnitude of 5.67. Du...
Open questionUSAAAO — 2021 First Round
Question 23
An astronomer observes that a Solar type star has an apparent V magnitude of 6.73 when seen from the Earth. Assuming tha...
Open questionUSAAAO — 2021 First Round
Question 24
1. The temperature of the Sun is 5000K while that of Sirius is 10000K. Which star has a higher integrated radiance i.e....
Open questionUSAAAO — 2021 First Round
Question 25
Suppose a spaceship is attempting a slingshot maneuver on a gas giant with mass 100 times that of the spaceship. Because...
Open questionUSAAAO — 2021 First Round
Question 26
Let's imagine that our Universe would be filled with basketballs, each having a mass of mb = 0.62 kg. What would be the...
Open questionUSAAAO — 2021 First Round
Question 28
An often-repeated fun fact is that humans produce more power per unit volume than stars. If the sun were the same size,...
Open questionUSAAAO — 2021 First Round
Question 29
Given that the redshift of cosmic microwave background (CMB) is 1100, what was the temperature of the Universe when phot...
Open questionUSAAAO — 2021 First Round
Question 30
Where and when should we place a radio telescope such that, when combined with a radio telescope on Earth, the system co...
Open questionUSAAAO — 2022 First Round
Question 1
Classify the following galaxies according the Hubble galaxies classification: Figure 1: Galaxy 1 Figure 2: Galaxy 2 Figu...
Open questionUSAAAO — 2022 First Round
Question 2
A comet’s orbit has the following characteristics: eccentricity e = 0.995; aphelion distance r_a = 5 × 10^4 AU. Assume w...
Open questionUSAAAO — 2022 First Round
Question 3
Consider the following elliptical orbit of a comet around a star: Which of the following expressions corresponds to the...
Open questionUSAAAO — 2022 First Round
Question 4
What is the shortest distance (along the surface of the Earth) between two points on the Equator separated by 30° of lon...
Open questionUSAAAO — 2022 First Round
Question 5
Two (spherical) asteroids, Ek and Do, are orbiting in free space around their stationary center of mass. Ek has mass 7M_...
Open questionUSAAAO — 2022 First Round
Question 6
Consider a f/9 telescope with focal length f = 1.0 m that operates at visible wavelength λ = 5000 Å. What is the farthes...
Open questionUSAAAO — 2022 First Round
Question 7
Imagine the you observe transits of earth across the sun from a far away exoplanet. Assuming earth's orbit has 0 eccentr...
Open questionUSAAAO — 2022 First Round
Question 8
An exoplanet was observed during its transit across the surface of a bright star. Estimate the variation of the apparent...
Open questionUSAAAO — 2022 First Round
Question 9
Estimate the mass of a globular cluster with a radial velocity dispersion σ_r = 16.2 km/s. The cluster has an angular di...
Open questionUSAAAO — 2022 First Round
Question 10
Jupiter's deep atmosphere is very warm due to convection leading to an adiabatic temperature profile that increases with...
Open questionUSAAAO — 2022 First Round
Question 11
An astronomer took the following picture while observing the night sky: What is the latitude of the place where the astr...
Open questionUSAAAO — 2022 First Round
Question 12
Order the following phases of the Sun's evolution from first to last chronologically. 1. Helium flash 2. White dwarf 3....
Open questionUSAAAO — 2022 First Round
Question 13
The orbit of some planet to its star has an eccentricity of 0.086. What is the ratio of the planet's closest distance to...
Open questionUSAAAO — 2022 First Round
Question 14
Figure 6 shows a 6-hr root-mean-square (rms) Combined Differential Photometric Precision (CDPP) curve for 150,000 stars...
Open questionUSAAAO — 2022 First Round
Question 15
A star with mass M goes through an energy-generating nuclear reaction 4 ¹H → ⁴He + Energy. Here, the burning efficiency...
Open questionUSAAAO — 2022 First Round
Question 16
In 2025, the Parker Solar Probe will pass just 6.9 × 10^6 km from the Sun, becoming the closest man-made object to the S...
Open questionUSAAAO — 2022 First Round
Question 17
An astronomer observes an eclipsing binary star system from Earth, and he plots the following light curve. Suppose that...
Open questionUSAAAO — 2022 First Round
Question 18
Assume that the smaller star in the binary star system shown below is brighter than the larger star. What is the ratio o...
Open questionUSAAAO — 2022 First Round
Question 19
The resolution of a space telescope is theoretically limited by diffraction from its primary mirror. In this problem, we...
Open questionUSAAAO — 2022 First Round
Question 20
The eccentricity of Pluto's orbit is 0.25. Estimate the maximum change in magnitude of Pluto as seen from Earth in one o...
Open questionUSAAAO — 2022 First Round
Questions 21–22
A satellite is in a circular, equatorial orbit, and can fire its engines to accelerate in any of the following direction...
Open questionUSAAAO — 2022 First Round
Question 23
An exoplanet discovered by the radial velocity method is found to have an orbital period of 2.45 days around a Sun-like...
Open questionUSAAAO — 2022 First Round
Question 24
Deneb is a very important star in the Northern hemisphere as it is one of the three stars in the Summer Triangle. Deneb...
Open questionUSAAAO — 2022 First Round
Question 25
Suppose you are in Houston (29°461N 95°231W) on the fall equinox and you just observed Deneb culminating (upper culminat...
Open questionUSAAAO — 2022 First Round
Question 26
Knowing that the following image was taken at 11:59pm, determine the name of which constellation was the sun passing in...
Open questionUSAAAO — 2022 First Round
Question 27
An astronomer observes a galaxy in very foggy weather. So far, she has an image of signal-to- noise ratio of approximate...
Open questionUSAAAO — 2022 First Round
Question 28
Dubhe (declination δ = 61.75 °) is a star in the constellation of Ursa Major. Is it circumpolar from the city of San Fra...
Open questionUSAAAO — 2022 First Round
Question 29
An astronomer takes a spectrum of a galaxy and observes that the hydrogen-alpha emission line is at a wavelength of 721....
Open questionUSAAAO — 2022 First Round
Question 30
What is the time difference between the longest day of the year and the shortest day of the year in San Francisco (37.7°...
Open questionUSAAAO — 2023 First Round
Question 1
According to the astronomical Julian day count, JD 2459946.0 corresponds to January 1, 2023 at 12:00 UT. What would be t...
Open questionUSAAAO — 2023 First Round
Question 2
A cluster has a radius of 2 parsecs. A Sun-like star in the cluster has an apparent magnitude of 10. When we look at the...
Open questionUSAAAO — 2023 First Round
Question 3
The radius of the Moon is about 4 times smaller than the radius of the Earth. The mean albedos of the Moon and the Earth...
Open questionUSAAAO — 2023 First Round
Question 4
The Sun has a surface temperature of about 6000 K and its blackbody emission peaks in the visible spectrum. Around 1940s...
Open questionUSAAAO — 2023 First Round
Question 5
Friedrich Bessel was the first person to quantitatively measure the annual change in stellar positions due to the motion...
Open questionUSAAAO — 2023 First Round
Question 6
Compute the blackbody luminosity of a neutron star with its surface temperature at 10^6 K and radius 10^4 m.
Open questionUSAAAO — 2023 First Round
Question 7
Fill in the blanks. The Balmer lines are a series of emission spectrum of hydrogen. In the low temperature interstellar...
Open questionUSAAAO — 2023 First Round
Question 8
A comet passes near the Sun on a parabolic orbit. While it's passing near the Sun with orbital velocity V , the Sun's he...
Open questionUSAAAO — 2023 First Round
Question 9
Consider Galaxies A and B, both of which have radius R. At a distance R from its center, Galaxy A's rotational velocity...
Open questionUSAAAO — 2023 First Round
Question 10
Consider a satellite that has a circular orbit with a radius of 6.0 × 10^8 m around Venus. Due to a failure in its ignit...
Open questionUSAAAO — 2023 First Round
Question 11
Consider a main-sequence star with mass M = 9.1 × 10^29 kg, which is sustained through the proton-proton chain reaction,...
Open questionUSAAAO — 2023 First Round
Question 12
A planet is in an elliptical orbit around a star. Let rmin be the minimum distance between the planet and star, and let...
Open questionUSAAAO — 2023 First Round
Question 13
The apparent magnitude of a star of radius 0.41R☉ as observed from Earth appears to fluctuate by 0.037. That is, the dif...
Open questionUSAAAO — 2023 First Round
Question 14
An empirically determined approximate formula for the lifetime of a star is given by: T = (M☉ / M)^2.5 × 10^10 years, wh...
Open questionUSAAAO — 2023 First Round
Question 15
With the technology currently available, it would take hundreds of millennia to send a human-made object to other stars....
Open questionUSAAAO — 2023 First Round
Question 16
Which of the following constellations is not on the sky map below?
Open questionUSAAAO — 2023 First Round
Questions 17–18
The fictional towns of Baia and Caia are located at (66.56° N, 67.55° E) and (δ, 18.95° E), respectively. It is known th...
Open questionUSAAAO — 2023 First Round
Question 19
In 1995, researchers at the University of Geneva discovered an exoplanet in the main-sequence star 51 Pegasi. This was t...
Open questionUSAAAO — 2023 First Round
Question 20
Suppose that an astronomer detects an electromagnetic wave of frequency ν. Some time later, another wave with the same a...
Open questionUSAAAO — 2023 First Round
Question 21
Consider the binary system Kepler-16, which has the primary star Kepler-16A and the secondary star Kepler-16B. It has an...
Open questionUSAAAO — 2023 First Round
Question 22
The habitable zone of a star is defined as the one where water in the liquid state can exist in the surface of a planet....
Open questionUSAAAO — 2023 First Round
Question 23
Billions of years from now, as the Moon moves farther away from the Earth, the Earth's axial tilt may become unstable. I...
Open questionUSAAAO — 2023 First Round
Question 24
Erez is designing a Newtonian telescope! The equation of the primary mirror is y = x^2/(36 m) − 1 m, and the telescope t...
Open questionUSAAAO — 2023 First Round
Question 25
Consider a hypothetical planet orbiting the Sun with an obliquity angle i (angle between the axis of rotation and the no...
Open questionUSAAAO — 2023 First Round
Question 26
A comet is approaching our solar system from the depths of space with a velocity of 10000 m/s, and if it continues movin...
Open questionUSAAAO — 2023 First Round
Question 27
How far from the Solar System would a galaxy with a redshift of 0.035 be?
Open questionUSAAAO — 2023 First Round
Question 28
Two planets A and B orbit a star with coplanar orbital paths that don't intersect. The major axes of the orbits are perf...
Open questionUSAAAO — 2023 First Round
Question 29
Here is a map of MIT and the surrounding area, where North points directly upwards, as taken from https://whereis.mit.ed...
Open questionUSAAAO — 2023 First Round
Question 30
After a day spent showing a visiting friend around Boston, Leo is walking back along the bridge (see diagram below) to r...
Open questionUSAAAO — 2024 First Round
Question 1
David is walking down MIT’s infinite corridor (latitude 42°21′33″) when he suddenly sees the sun aligning with the windo...
Open questionUSAAAO — 2024 First Round
Question 2
Abhay looks at the light curves for two main sequence stars A and B, which you can assume are blackbodies. A has its pea...
Open questionUSAAAO — 2024 First Round
Question 3
Aliens in a nearby star system (located in a random direction from Earth) are looking for nearby planets using the trans...
Open questionUSAAAO — 2024 First Round
Question 4
Orion is observing the sky with two telescopes that he just made. Orion wrote down that the first telescope has a primar...
Open questionUSAAAO — 2024 First Round
Question 5
A supernova is triggered largely by neutrinos. In fact, 99% of the energy coming from the supernova is released in form...
Open questionUSAAAO — 2024 First Round
Question 6
Newly discovered planets DDP and CJ are found to orbit a nearby star, as shown in the figure below. Planet CJ has a circ...
Open questionUSAAAO — 2024 First Round
Question 7
Arjun launches a 50 kg rocket with speed 10,405 m/s from the surface of the Earth and redirects it into a stable ellipti...
Open questionUSAAAO — 2024 First Round
Question 8
The mass density of the Milky Way galaxy determines the orbital velocity of planets, stars, and other objects orbiting a...
Open questionUSAAAO — 2024 First Round
Question 9
Let’s assume that on an expedition mission to Mars, we take a telescope with 0.01 arcsecond angular resolution from eart...
Open questionUSAAAO — 2024 First Round
Question 10
Ben Chen is an alien living on a system identical to earth, except his planet’s obliquity is 0°. Located at latitude 42....
Open questionUSAAAO — 2024 First Round
Questions 11–12
Joe lives at the bottom of a vertical cylindrical hole with a radius of 10 m at a depth of 10 km below the surface. He s...
Open questionUSAAAO — 2024 First Round
Question 13
Samvit observes a binary star system of masses M1 and M2. Unfortunately, the star with mass M2 is too dim for him to obs...
Open questionUSAAAO — 2024 First Round
Question 14
The surface of the Sun exhibits differential rotation, with different rotational periods at different latitudes. We can...
Open questionUSAAAO — 2024 First Round
Question 15
Two protons A and B lie in the solar interior. In the rest frame of proton A, the proton B approaches it radially from a...
Open questionUSAAAO — 2024 First Round
Question 16
Consider a sun-planet-moon system. The rotation period of the planet is 2 days. The period of revolution of the moon aro...
Open questionUSAAAO — 2024 First Round
Question 17
The Extremely Large Telescope (ELT) is an optical telescope under construction in Chile. The primary mirror has been pla...
Open questionUSAAAO — 2024 First Round
Questions 18–19
At 6am on March 20th, as the Sun is rising, Leo, who is at (40° N, 75° W), plants a stick vertically on the ground. At t...
Open questionUSAAAO — 2024 First Round
Question 20
Imagine a very long cylindrical planet that has a satellite orbiting around it. Considering that the average density of...
Open questionUSAAAO — 2024 First Round
Question 21
The problem of magnetic monopoles — that is, the apparent absence of magnetic monopoles in the universe — arises from th...
Open questionUSAAAO — 2024 First Round
Question 22
Tara is investigating a new interesting type of stars she decides to call the X stars. She observes that in an X star of...
Open questionUSAAAO — 2024 First Round
Question 24
Tara has become obsessed with X stars and decides to look for them in other galaxies. She observes one on the edge of a...
Open questionUSAAAO — 2024 First Round
Question 25
There is a galaxy at redshift 0.5 for which we have a measurement for apparent bolometric magnitude to be 22. With a sta...
Open questionUSAAAO — 2024 First Round
Question 26
An astronomer wants to design a telescope so that the full moon fills the entire FOV of the telescope. She uses an eyepi...
Open questionUSAAAO — 2024 First Round
Question 27
The Cosmic Microwave Background is made of light that was released when the Universe first became transparent. It is a b...
Open questionUSAAAO — 2024 First Round
Question 28
Moving into MIT for the start of the spring semester, Austin is flying from Lubbock, Texas (33.58° N, 101.84° W) to Bost...
Open questionUSAAAO — 2024 First Round
Question 29
After that slight headache, Austin is back at MIT in Boston! For his astronomy research, he is observing the LARES satel...
Open questionUSAAAO — 2025 First Round
Question 1
Imagine you are on Deimos right now and you want to escape Mars because you are bored. If Deimos is currently at 23,460...
Open questionUSAAAO — 2025 First Round
Questions 2–3
Suppose a spherical gas giant has radius R, temperature T, uniform density and composition, and fixed volumetric heat ca...
Open questionUSAAAO — 2025 First Round
Question 4
Suppose a rocket around a star of mass M wishes to execute an orbital transfer from a circular orbit with radius R to a...
Open questionUSAAAO — 2025 First Round
Question 5
It may be useful to know the semi-latus rectum of an ellipse is the distance between one of its foci and the point on th...
Open questionUSAAAO — 2025 First Round
Question 6
Galileo the Tyrant has conquered the Earth. In his madness, he launched many bright satellites into space because he tho...
Open questionUSAAAO — 2025 First Round
Question 7
What is the geodesic distance between Boston (42°21′37″ N, 71°3′28″ W) and Mumbai (19°4′34″ N, 72°52′39″ E)? Assume that...
Open questionUSAAAO — 2025 First Round
Question 8
Which of the following statements are correct regarding spectral broadening? P: In the limit of zero temperature, spectr...
Open questionUSAAAO — 2025 First Round
Question 9
Which of the following statements are true about a cluster of main sequence stars: A: For two star clusters of the same...
Open questionUSAAAO — 2025 First Round
Question 10
Match each imaginary line in the sky map below to its label.
Open questionUSAAAO — 2025 First Round
Questions 11–12
An astronomer was studying the exoplanets orbiting a star with a mass of 10 M☉. The astronomer decided to draw a log T v...
Open questionUSAAAO — 2025 First Round
Question 13
A recently observed exosolar system consists of a star, a planet, and the planet’s satellite. The satellite has a revolu...
Open questionUSAAAO — 2025 First Round
Question 14
A cylindrical space station rotating about its primary axis could create artificial “spin gravity,” allowing people to l...
Open questionUSAAAO — 2025 First Round
Question 15
A cylindrical space station rotating about its primary axis could create artificial “spin gravity,” allowing people to l...
Open questionUSAAAO — 2025 First Round
Question 16
A cylindrical space station rotating about its primary axis could create artificial “spin gravity,” allowing people to l...
Open questionUSAAAO — 2025 First Round
Question 17
Consider a giant star with radius R. The core has temperature Tc and the surface has temperature Ts ≪ Tc. Given R, Tc, a...
Open questionUSAAAO — 2025 First Round
Question 18
Connor is stranded on an island and wishes to determine his latitude, but he only wakes up at sunrise and sunset. He con...
Open questionUSAAAO — 2025 First Round
Question 19
Which of the following statements CANNOT be inferred from Kepler’s laws of motion? I: A planet moves in an elliptical or...
Open questionUSAAAO — 2025 First Round
Question 20
Just before dawn of the summer solstice, Christopher the sailor begins sailing due West from 50° N, 5° W. His watch is s...
Open questionUSAAAO — 2025 First Round
Question 21
What is the largest range of latitudes φ for which, at some time during the day, the line between Rigel (αR = 5h 14m 32s...
Open questionUSAAAO — 2025 First Round
Question 22
Observed from the equator, what is the maximum duration over which Venus can be observed (continuously) after sunset? As...
Open questionUSAAAO — 2025 First Round
Question 23
The Earth orbits the Sun with orbital eccentricity e = 0.0167. What percent more total solar irradiance does the Earth r...
Open questionUSAAAO — 2025 First Round
Question 24
Consider a main sequence star 500 times less luminous than the sun. This star must have a ______ core and a ______ envel...
Open questionUSAAAO — 2025 First Round
Question 25
Evan uses a telescope of focal distance f = 1000 mm to observe a star known to have a parallax p = 50 mas. Observing the...
Open questionUSAAAO — 2025 First Round
Question 26
Two exoplanets, A and B, have circular orbits around the same central star. Suppose that the ascending nodes of the orbi...
Open questionUSAAAO — 2025 First Round
Question 27
Cosmologists consider three possible universes: universes dominated by baryonic matter (i.e. ordinary matter), universes...
Open questionUSAAAO — 2025 First Round
Question 28
Suppose leap days were removed from the calendar, so that each calendar year has exactly 365 days. In the first year of...
Open questionUSAAAO — 2025 First Round
Question 29
It is observed that a planet orbiting a star increases the observed magnitude of the system by 0.005 when it transits ac...
Open questionUSAAAO — 2025 First Round
Question 30
What is the focal ratio of a telescope with 1.2 m in focal length and 12 cm in aperture?
Open questionUSAAAO — 2026 First Round
Question 1
A planet moves in a circular orbit in a fixed plane with angular velocity ω, and let n-hat be a unit vector perpendicula...
Open questionUSAAAO — 2026 First Round
Question 2
A planet of mass m orbits a star of mass M in an elliptical orbit with semi-major axis a and eccentricity e where M ≫ m....
Open questionUSAAAO — 2026 First Round
Question 3
Astronomers in the United States observe a spiral galaxy and measure its rotation curve. They find that beyond a radius...
Open questionUSAAAO — 2026 First Round
Question 4
You are stranded on a remote island somewhere on Earth, at an unknown date and time (in the 21st century). You look up a...
Open questionUSAAAO — 2026 First Round
Question 5
You are stranded on a remote island somewhere on Earth, at an unknown date and time (in the 21st century). You look up a...
Open questionUSAAAO — 2026 First Round
Question 6
You are stranded on a remote island somewhere on Earth, at an unknown date and time (in the 21st century). You look up a...
Open questionUSAAAO — 2026 First Round
Questions 7–8
One of Stephen Hawking’s most famous predictions was the existence of Hawking radiation. Specifically, black holes act l...
Open questionUSAAAO — 2026 First Round
Question 9
The asteroid Pallas orbits the Sun with a semi-major axis of 2.77 AU. What is its orbital period around the Sun in years...
Open questionUSAAAO — 2026 First Round
Question 10
A small satellite orbits the Earth so it stays directly above a fixed point on the equator. Using 5.97 × 10²⁴ kg for Ear...
Open questionUSAAAO — 2026 First Round
Question 11
Four bright stars were erased from the sky map below. All of these stars have magnitudes lower than 3.0. Select the alte...
Open questionUSAAAO — 2026 First Round
Question 12
An extraterrestrial form of life from a distant planetary system observed a transit of Jupiter across the Sun. The trans...
Open questionUSAAAO — 2026 First Round
Question 13
What is the smallest angular separation between Algol (β Per) and the Sun throughout the year? Algol’s declination is +4...
Open questionUSAAAO — 2026 First Round
Question 14
Consider a cloud of hot gas with radius R and total (electromagnetic) power emission rate P. Keeping the average tempera...
Open questionUSAAAO — 2026 First Round
Question 15
Lunar laser ranging experiments show that, due to tidal effects, the semi-major axis of the Moon’s orbit increases by ar...
Open questionUSAAAO — 2026 First Round
Question 16
Kepler-22b is an exoplanet discovered by transiting with an orbital period of 290 days. Suppose it has a mass of 4.84 ×...
Open questionUSAAAO — 2026 First Round
Question 17
A quickly-moving black hole passes through the center of a large star cluster. While the black hole does not experience...
Open questionUSAAAO — 2026 First Round
Question 18
The most distant known galaxy, MoM-z14, was recently observed by the James Webb Space Telescope and has a redshift of z...
Open questionUSAAAO — 2026 First Round
Question 19
Assume a spherical star has a density profile described by the equation ρ(r) = (1 − r³/R³) ρc, for 0 ≤ r ≤ R. Find ρc in...
Open questionUSAAAO — 2026 First Round
Question 20
Some stars formed in the early universe are still observable today. If an observer observed one and it is still in the m...
Open questionUSAAAO — 2026 First Round
Question 21
Consider the following graph (below), which shows the mean orbital velocity of stars around a galaxy’s center as a funct...
Open questionUSAAAO — 2026 First Round
Question 22
Consider the following graph (below), which shows the mean orbital velocity of stars around a galaxy’s center as a funct...
Open questionUSAAAO — 2026 First Round
Question 23
Consider the following graph (below), which shows the mean orbital velocity of stars around a galaxy’s center as a funct...
Open questionUSAAAO — 2026 First Round
Question 24
Suppose the Honeyhive galaxy and the Gold Leaf galaxy are diametrically opposite when viewed from the Earth, and the fol...
Open questionUSAAAO — 2026 First Round
Question 25
The Balmer-α, H-I, and Lyman-α lines are important spectral lines in astronomy, all from hydrogen. The Balmer-α line occ...
Open questionUSAAAO — 2026 First Round
Question 26
Star X and star Y form an eclipsing binary system, where star X is larger, and fully blocks star Y during an eclipse. Du...
Open questionUSAAAO — 2026 First Round
Question 27
When plotting the distribution of asteroids in the asteroid belt by their semi-major axis, we can see several regions, k...
Open questionUSAAAO — 2026 First Round
Question 28
Below is an HR diagram for a globular cluster from Gaia DR3 data. The figure has labeled regions: “A”, “B”, “C”, and “D”...
Open questionUSAAAO — 2026 First Round
Question 29
Which of the following is closest to the ratio of the number of photons from the Sun that strike the Earth each second t...
Open questionUSAAAO — 2026 First Round
Question 30
Consider two galaxies: Galaxy S is a spiral galaxy with blue spiral arms. Galaxy E is an elliptical galaxy with no blue...
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