Lighting Undiscovered Places Quiz - A History of Astronomy | Astronomy

Quiz Answer Key and Fun Facts

1. Astronomy began with what is still the most complex observational tool we possess - the human eye. When prehistoric humans gazed up at the stars with their naked eyes, which of the following would they NOT have been able to see?

Answer: Neptune

Two planets in the Solar System, Uranus and Neptune, are too distant and faint to be visible to the naked eye, lit up only by reflected sunlight.

Alpha Centauri sits almost 10,000 times further away at a distance of 4 light years yet, as a light-emitting star, it is clearly visible as the third brightest star in the sky.

The Orion Nebula is even further away at 1,500 light years away from Earth, and is a nursery for newly forming stars.

At a remarkable distance of 2.5 million light years, the Andromeda Galaxy is the most distant object visible to the naked eye. Despite the distance, its 1 trillion stars emit enough light to reach our retinas here on Earth.

2. Starting in 1609, Galileo Galilei was a pioneer in the use of the newly invented telescope to expand our astronomical horizons beyond the naked eye's view. Aside from his famous discovery of the four largest moons of Jupiter, he was the first to observe a number of new phenomena in the universe. Which of these is NOT one of his discoveries?

Answer: The black hole at the centre of the Milky Way

The first telescope was invented some time around 1608 and the design quickly spread through Europe. Though it was likely put to more terrestrial uses initially, Galileo made his own refined design in 1609 and began pointing it towards the night sky. The magnification and extra light it could collect vastly expanded the visible astronomical horizon, bringing into focus the craters of Earth's moon, the Galilean moons of Jupiter, the phases of Venus, Saturn's rings, sunspots, and even distant stars of the Milky Way.

Though he did not recognise it as a planet, Galileo also observed Neptune in 1612, over two centuries before it was officially discovered in 1846.

3. Since Galileo's pioneering work, a plethora of optical telescope designs have emerged, based on a few fundamental design types. Which of the following is NOT a type of optical telescope?

Answer: Refreshing

Galileo's pioneering telescope was a refracting telescope. These use lenses to refract (bend) light and focus it at the eyepiece, hence magnifying the light source.

Reflecting telescopes were theorised soon after word of the refracting telescope had spread, with Isaac Newton being credited as building the first working model. These telescopes use a concave curved mirror which reflects light and focuses it onto the eyepiece, typically by means of a secondary mirror. They have the advantage of reducing spherical (shape) and chromatic (colour) aberration inherent to refraction.

Catadioptric telescopes use both refraction and reflection which allows for better correction of aberrations in the images produced by refraction or reflection alone. The earliest such telescope was developed in 1930 by German astronomer Bernhard Schmidt.

4. By the 20th century, astronomers started to expand their horizons beyond visible light and into other parts of the electromagnetic spectrum. In the 1930s, the first astronomical sources of radio waves were detected when Karl Jansky detected a radio wave signal coming from the centre of the Milky Way, located in which 'archer' constellation?

Answer: Sagittarius

Jansky was trying to identify sources of interference in short wave transatlantic voice transmissions. He detected a signal that peaked roughly every 24 hours, causing him to suspect the Sun as the source. However, with further analysis he realised it peaked every 23 hours and 56 minutes (the exact length of a sidereal day - the time it takes for stars to reach the same point in the sky after one rotation of the Earth on its axis). Realising the source must be out amongst the stars, it was eventually pinpointed to a region called Sagittarius A which is the densest part of the Milky Way. We now know that the source of these radio emissions is a supermassive black hole that exists there at the centre of the galaxy.

Radio astronomy has identified entirely new classes of astronomical objects and phenomena not identified by visible light alone, such as radio galaxies, quasars, pulsars, masers and the cosmic microwave background. It remains a significant part of modern astronomical research to this day.

5. In 1946, the technique of radio interferometry was introduced, allowing radio signals from multiple antennas to be combined to achieve much greater resolution than the individual signals alone. Taking advantage of this technique, the Square Kilometre Array (SKA) was proposed, comprising of hundreds of dishes and thousands of antennas with a total collecting area of 1 square kilometre. In the vast deserts of which two countries did construction of the SKA begin in 2018?

Answer: Australia and South Africa

Interferometry is a brilliant technique where the angular resolution (essentially the magnification) of the image produced is equal to the maximum separation between the component telescopes. For the SKA, the maximum image resolution is the equivalent of a 150km (93 mile) diameter single dish which would cover over 17,000 square km (4 million acres). Rather impressive for an array with a surface area of just 1 square km.

Of course, there is a catch (no such thing as a free lunch in physics). The amount of light collected depends on the total surface area, so the SKA will collect 17,000 times less light than the equivalent large dish. This can limit its ability to image less luminous radio sources.

6. Beyond visible light and radio waves, there is still a broad range of electromagnetic radiation including microwaves, infrared, ultraviolet, X-rays and gamma rays. The universe is awash in these forms of radiation, however their observation is limited by the Earth's atmosphere which absorbs and scatters most of the radiation. How does NASA's Chandra X-ray Observatory overcome this challenge?

Answer: It was launched into space by the Space Shuttle Columbia and orbits the Earth above the atmosphere

Early X-ray astronomy used rockets, high-altitude balloons and satellites to get above the atmosphere, however their observations were limited by short flight durations and technological limitations of the detectors.

Chandra was launched in 1999 and revolutionised X-ray astronomy. It significantly improved on the resolution of previous X-ray telescopes and has made countless discoveries of X-ray sources such as neutron stars, nebulae and black holes. It is named after Indian-American theoretical physicist Subrahmanyan Chandrasekhar, who contributed much towards our understanding of stellar evolution and black holes, and won the 1983 Nobel Prize in Physics.

7. Gamma ray astronomy observes the highest energy radiation in the electromagnetic spectrum. Naturally, it also captures the most energetic explosions known in the universe after the Big Bang itself. What are these violent outbursts of energy called?

Answer: Gamma ray bursts

Gamma ray bursts (GRBs) are thought to originate from events like neutron star and black hole formation from supernovae, and mergers of binary neutron stars. The initial high-energy gamma ray release can last from a few milliseconds to several hours, followed by an afterglow of lower energy radiation including anything from X-rays to radio waves.

All recorded GRBs have occurred outside of our galaxy, the Milky Way, which is quite fortunate for us here on Earth. If a GRB in the Milky Way were pointed directly at Earth, it would likely sterilise life on the planet, causing a mass extinction.

8. The James Webb Space Telescope (JWST) is seen as a 21st century spiritual successor to the famous Hubble Space Telescope. It utilises the infrared spectrum to open yet another window into the cosmos. From which overseas department of France, located in South America, was the telescope launched in 2021?

Answer: French Guiana

JWST orbits a unique position called the Sun-Earth L2 Lagrange point. This is about 1.5 million km (930,000 miles) beyond the Earth's orbit around the sun (about 4x the distance to the Moon). Due to the gravitational effects of the Earth and the Sun, objects orbiting this point will remain at the same distance from Earth, allowing it to maintain constant communication with Earth while being far enough away to avoid interference from the heat of the Earth and Moon.

JWST has produced many stunning images available to the public, including a re-creation of the iconic Hubble Deep Field long-exposure image, false colour images of solar system planets (such as the Cover Photo of this quiz - Jupiter), various nebulae and more. It is well worth taking some time after this quiz to view these inspiring images.

9. Now we move from the electromagnetic spectrum to gravity, another fundamental force of physics. Almost 100 years after Albert Einstein predicted their existence in his general theory of relativity, the LIGO observatory made the first direct observation of what phenomenon in 2015?

Answer: Gravitational waves

Gravitational waves had been long theorised, and their existence was supported by indirect experimental observations, however observing them directly proved to be an extreme technical challenge. They ripple through spacetime whenever matter moves, causing changes in the length of objects they pass through. However, even the largest sources of gravitational waves produce almost imperceptible effects. LIGO uses highly sensitive laser interferometry to detect changes in length of just 1/10,000th of the diameter of a proton in its 4km (2.5 mile) long perpendicular detector arms.

It is hoped that with more gravitational wave observatories being built and with greater sensitivity, they will offer additional information about the largest objects in the universe, particularly mergers of black holes and neutron stars.

10. We move beyond the fundamental forces to particles. Neutrinos are subatomic particles with no charge, interacting only weakly with other matter. Trillions of neutrinos pass through Earth every second with most sailing straight through undisturbed. To isolate the few neutrinos that do interact from other background radiation, such as cosmic rays, where are most neutrino detectors located?

Answer: Underground

Neutrinos only interact with other matter through gravity and the 'weak' force (one of the four fundamental forces in physics alongside gravity, electromagnetism and the strong force). Because their mass is so small, observing their gravitational interaction is not feasible and physicists rely on their weak force interaction to detect them.

The majority of neutrinos detected on Earth are created in the atmosphere from interactions of other particles, or originate from nuclear reactions in the Sun. Scientists have slowly uncovered other extraterrestrial sources including supernovae, active galaxies and even the Big Bang. It is hoped that with the rise of neutrino astronomy, we can learn more about things like the origin of cosmic rays and the Big Bang itself.

Source: Author patrickk

This quiz was reviewed by FunTrivia editor rossian before going online.
Any errors found in FunTrivia content are routinely corrected through our feedback system.

Lighting Undiscovered Places Trivia Quiz

A History of Astronomy

Astronomical observation is much more than just visible light and telescopes. Take a historical journey through the various frontiers of astronomy that have lit up undiscovered places in our universe.

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