TOEFL Complete the Words: Astronomy (Difficult)
Astronomy on TOEFL
In the TOEFL Reading section, astronomy is often considered a difficult topic. One reason is that many astronomy-related terms are highly specialized and cannot be easily inferred from the words themselves. For example, the term red dwarf frequently appears in TOEFL passages, yet its meaning is not obvious from the phrase alone.
Although academic texts usually provide clear definitions when such technical terms appear, many test takers become hesitant to continue reading once they encounter a series of unfamiliar terms. This hesitation can interrupt comprehension and slow down reading.
On this page, each question is designed to help you become familiar with common astronomy-related vocabulary while also practicing the Part 1 question format of the TOEFL Reading section. By working through these questions, you can reduce resistance to technical terms and read more confidently during the exam.
Practice Questions
Question 1
Many stars _ _ the night sky appear st_ _ _ _ and unchanging to the naked eye. Careful obs_ _ _ _ _ _ _ _, however, shows that some of them brighten and fade o_ _ _ time. Astronomers record these shifts in bri_ _ _ _ _ _ _ in order _ _ study how stars evolve and how energy moves through their outer layers. Such stars are known as variable stars. Their cha_ _ _ _ _ brightness may result f_ _ _ internal pulsations, surface activity, or the presence of a nearby companion star that peri_ _ _ _ _ _ _ _ blocks some of their light. By examining the patterns of variability, researchers can est _ _ _ _ _ stellar size, temperature, and distance.
Explanation
Complete passage
Many stars in the night sky appear stable and unchanging to the naked eye. Careful observation, however, shows that some of them brighten and fade over time. Astronomers record these shifts in brightness in order to study how stars evolve and how energy moves through their outer layers. Such stars are known as variable stars. Their changing brightness may result from internal pulsations, surface activity, or the presence of a nearby companion star that periodically blocks some of their light. By examining the patterns of variability, researchers can estimate stellar size, temperature, and distance.
Variable stars are stars whose brightness changes over time. Unlike most stars, which appear constant in brightness when viewed from Earth, variable stars show measurable increases and decreases in light. These variations can occur over periods ranging from hours to years.
The changes in brightness may have different causes. In some cases, the star itself expands and contracts, which alters the amount of light it emits. In other cases, the variation occurs because another object, such as a companion star, periodically blocks part of the light.
Astronomers study variable stars because their brightness patterns provide valuable information about stellar properties. In certain cases, the regularity of these variations can even be used to estimate cosmic distances, making variable stars an important tool in modern astronomy.
Question 2
Planets outside our so_ _ _ system are difficult to see directly because their host stars are much br_ _ _ _ _ _ and tend to outshine them. To d_ _ _ with this problem, astronomers often se_ _ _ _ for ind_ _ _ _ _ evidence instead of trying to observe the planets themselves directly. One common method inv_ _ _ _ _ tracking a small drop in starlight when a planet moves across the front of its star. This event is called a transit. By measuring how regularly the dimming occurs and how much light is bl_ _ _ _ _, researchers can estimate the planet’s size and orbital per_ _ _. Rep_ _ _ _ _ transit observations have shown that planets are common in many different kinds of star sy_ _ _ _ _.
Explanation
Complete passage
Planets outside our solar system are difficult to see directly because their host stars are much brighter and tend to outshine them. To deal with this problem, astronomers often search for indirect evidence instead of trying to observe the planets themselves directly. One common method involves tracking a small drop in starlight when a planet moves across the front of its star. This event is called a transit. By measuring how regularly the dimming occurs and how much light is blocked, researchers can estimate the planet’s size and orbital period. Repeated transit observations have shown that planets are common in many different kinds of star systems.
Exoplanets are planets that orbit stars outside our solar system. Because they are usually much dimmer than their host stars, astronomers often cannot see them directly. The light from the star tends to overwhelm the much fainter light from the planet, which makes direct observation difficult.
For that reason, astronomers often rely on indirect methods. One important example is the transit method. When a planet passes in front of its star from our point of view, the star appears slightly dimmer for a short time. By studying this repeated pattern, scientists can learn useful information about the planet, including its size and the length of its orbit.
The study of exoplanets has become an important area of astronomy because it has shown that planets are widespread in the universe. It has also revealed that planetary systems can look very different from our own, which has changed how scientists think about planet formation and the possibility of life elsewhere.
Question 3
A dis_ _ _ _ galaxy may appear brighter, more stretched, or even duplicated when viewed from Earth, despite no change in the galaxy itself. The dist_ _ _ _ _ _ occurs because light does not always travel al_ _ _ what seems to be a straight pa_ _. When a massive object lies between the observer and a faraway source, its gravity can b_ _ _ the light and alter the image that finally reaches a telescope. Astronomers describe this phen_ _ _ _ _ _ as gravitational lensing. It has become an important tool not only for det_ _ _ _ _ _ extremely distant galaxies but also for infe_ _ _ _ _ the presence of matter that cannot be seen directly. In some cases, the amount of visible matter is not enough to account _ _ _ the observed distortion, which is one reason the phenomenon is closely connected with the study of dark matter.
Explanation
Complete passage
A distant galaxy may appear brighter, more stretched, or even duplicated when viewed from Earth, despite no change in the galaxy itself. The distortion occurs because light does not always travel along what seems to be a straight path. When a massive object lies between the observer and a faraway source, its gravity can bend the light and alter the image that finally reaches a telescope. Astronomers describe this phenomenon as gravitational lensing. It has become an important tool not only for detecting extremely distant galaxies but also for inferring the presence of matter that cannot be seen directly. In some cases, the amount of visible matter is not enough to account for the observed distortion, which is one reason the phenomenon is closely connected with the study of dark matter.
Gravitational lensing is a phenomenon in astronomy in which light from a distant object is bent by the gravity of another massive object located between the source and the observer. Instead of traveling in a perfectly straight line, the light follows a curved path because space itself is affected by gravity.
This effect is important because it allows astronomers to study objects that would otherwise be too faint or too far away to observe clearly. A massive galaxy or cluster of galaxies can act like a lens, magnifying or distorting the light coming from something behind it. As a result, astronomers may see arcs, stretched images, or multiple versions of the same source.
Gravitational lensing is also useful because it reveals the influence of matter that cannot be seen directly. When the amount of bending is greater than visible matter alone can explain, astronomers infer that additional mass must be present. For that reason, gravitational lensing plays an important role in research on dark matter and the large-scale structure of the universe.
