Amazing Astronomical Phenomena and Terminology Quiz

Answer: Refraction nebulae

Nebulae are visible, relatively dense, regions in space made up mostly of gasses. Nebulae at cooler temperatures can be visible due to reflecting the light of nearby stars.

Cooler nebulae can also be dark nebulae which have a significant concentration of dust. The dust absorbs or scatters light blocking the light from sources behind the nebulae. They are seen as darker than normal regions in space.

Emission nebulae are at higher temperatures and are energized by sources such as new stars, which emit ultraviolet radiation. They can also be supernova remnants which are still at high temperatures. Energized gas atoms and molecules in emission nebulae emit light when they drop from higher energy states down into lower energy states.

Answer: They are the core remains from most burned out stars

White dwarf stars are indeed the remnants of lower mass stars which make up over 95% of the stellar population. White dwarfs are very dense with a mass similar to the Sun's and a volume similar to Earth's. They are not very bright because their light comes from left over thermal radiation rather than fusion, which is no longer occurring.

As lower mass stars, such as our sun, use up their hydrogen for fusion, they first expand into red giant stars. They then shed their outer material which becomes a planetary nebula. The remaining core is a white dwarf.

Answer: Rotating neutron stars

The word pulsar is a portmanteau of "pulsating radio source." Pulsars are rotating neutron stars that emit beams of electromagnetic (EM) radiation out from their magnetic poles. The first signals from pulsars were in the radio wavelength of the EM spectrum, hence the term pulsating radio source.

Subsequently, pulsars have been found which emit EM radiation at shorter wavelengths including visible light and X-rays. The emitted EM radiation can be observed only when a beam is pointing toward Earth. This is analogous to the way the light from a lighthouse on a clear night can only be seen when the light is pointed in the direction of the observer.

Answer: Lenticular galaxies

Active galactic nuclei are condensed regions at the center of many galaxies that emit large amounts of energy across the electromagnetic spectrum. The radiation emitted by an AGN is theorized to be caused by the accretion of matter by a supermassive black hole at the center of the galaxy. Gas in the spinning accretion disc, which is pulled towards the black hole, heats up and emits electromagnetic radiation. Some of the gas is also shot out in the form of extremely powerful jets of ionized matter at near the speed of light.

There is a theory that quasars, blazars and radio galaxies are all the same phenomenon seen at different angles from Earth. Blazars appear to have the most energy because the jet is pointed toward us. Quasars are seen with the jet at an angle. Radio galaxies are seen with the jet being perpendicular to us.

Lenticular galaxies are somewhat lens shaped when viewed edge-on so the term simply refers to their shape.

Answer: Greater than a lightyear

A parsec is approximately equal to 3.26 light-years or 30.9 trillion kilometres (19.2 trillion miles). The parsec is useful in astronomy because a parsec unit is obtained by the use of the parallax effect and trigonometry. It is defined as the distance at which 1 Astronomical Unit (AU), which is the distance from the Earth to the Sun, subtends an angle of one arcsecond (1/3600 of a degree of a circle).

Answer: At the periphery of our solar system

The Oort Cloud is a region at the gravitational margins of our Solar System. Objects at this distance (as far as 3.2 light-years) are very weakly bound to the Solar System. Most of the material in this region is in the form of frozen compounds such as water, methane, ethane, carbon monoxide and hydrogen cyanide.

The Oort Cloud is the primary source of long-period comets (those which take more than 200 years to complete an orbit around the Sun) . Because objects in the Oort Cloud are weakly affected by the sun's gravity, perturbations in the gravitational field can dislodge them from the Oort Cloud and send them into inner solar system orbits as comets.

Answer: Brown dwarfs

Brown dwarfs are in between planets and typical active stars in mass. Although they can be roughly the same size as Jupiter, they have more mass than the biggest gas giant planets but less than the main-sequence stars. Main-sequence stars, like our own Sun, fuse hydrogen into helium. Brown dwarfs do not have enough mass to sustain nuclear fusion of ordinary hydrogen into helium but they can emit some electromagnetic radiation and heat from the fusion of deuterium (hydrogen with a neutron in addition to the proton in the nucleus).

The first definite brown dwarf was discovered in the mid-1990s. Because they have relatively low surface temperatures, they are not very bright at visible wavelengths of light and instead emit most of their electromagnetic energy in the infrared.

Answer: Small galaxies which orbit our galaxy

The Magellanic Clouds are two small galaxies in the southern celestial hemisphere which orbit our Milky Way galaxy. They are descriptively named the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). It has been estimated that the total mass of the LMC is about 1/10 that of the Milky Way and the LMC is about twice the diameter of the SMC . Both can be seen by the naked eye in the Southern Hemisphere but cannot be observed from the most northern latitudes.

Answer: It is smaller than the asteroid belt

The Kuiper belt is a doughnut-shaped region extending from the orbit of Neptune outward. It is similar to the asteroid belt but is far larger - it has 20-200 times the mass and is about 20 times wider. It mainly contains small bodies which are remnants from when the Solar System formed, that is, stuff that didn't accumulate to become part of a full-fledged planet. While many asteroids in the asteroid belt are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen compounds such as methane, ammonia, and water.

The Kuiper belt is where objects that are now considered dwarf planets reside including Pluto, Haumea, Orcus, Quaoar, and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region and were captured by the planet. Also, short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt.

Answer: Gravitational waves

Neutrinos are electrically neutral, have very low mass and don't interact via the strong force. Therefore neutrinos typically pass through normal matter unimpeded and undetected. Measuring them is very difficult but useful for a number of astronomical studies including our Sun, supernovae and cosmic background radiation. Neutrino detectors are generally built underground or underwater to isolate the detector from background noise.

Muons are elementary particle similar to electrons but substantially more massive. Muons that hit the Earth are created indirectly as decay products of collisions of cosmic rays with molecules in the Earth's atmosphere. Since muons are unusually penetrative of ordinary matter, as with neutrinos, they are detectable deep underground and underwater.

Another weakly interacting phenomenon, WIMPs (Weakly Interacting Massive Particles), are hypothetical particles that are one of the proposed candidates for dark matter. The Cryogenic Dark Matter Search (CDMS) is a series of experiments designed to directly detect WIMPs. The SuperCDMS project ran from 2011 to 2015 and was located deep underground in the Soudan Mine in northern Minnesota.

Gravitational waves are measured using ground-based laser interferometers which span several kilometers. The first direct observation of gravitational waves was made in 2015. Waves generated by the merger of two black holes were measured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in Louisiana and Washington state.