Book Review Sample Paper on Astronomy

Summary of the Article

Gillon et al. (2017) indicate that the main purpose of modern astronomy is to discover exoplanets that have atmospheric characterizations and features similar to earth. This means that their main function is to identify planets that can harbor life as it is on earth. The search under discussion began earlier in the decade but intensified in February 2016 when groundbreaking observations were made that would lead to the discovery of such exoplanets (Alibert & Benz, 2017). As a result, Gillon et al.  (2017) reported that they had discovered seven planets that weigh equally to the planet earth, orbiting around a dwarf star known as TRAPPIST-1. Of these seven exoplanets, five of them have the highest capability of harboring life as their sizes, temperatures, and masses are closest to those of planet Earth. This dwarf star that the exoplanets orbit around is quite a bit smaller, 20 percent, and cooler as compared to our star, the sun. These exoplanets are named after this dwarf star TRAPPIST 1, i.e. TRAPPIST-1b, TRAPPIST-1c, TRAPPIST-1e, TRAPPIST-1f, and TRAPPIST-1g. As mentioned by Gillon (2017), these planets have a lower equilibrium temperature that can make it possible to have the presence of water. Astronomers predict that one of these exoplanets has the right temperature to possess oceans. Similarly, the article suggests that the dwarf star TRAPPIST 1 and its exoplanets are comparable to other explanatory systems. First, the star is cool, similar to other red dwarfs that have become popular targets for exoplanet hunters. The planets are also super close to their star as observed in other explanatory systems. Finally, they seem to orbit in sync in what astronomers call orbital resonance in a ratio of 4:3.

The process of discovering these exoplanets was quite lengthy and involves sophisticated technology. First, the astronomers discovered that there are planets revolving around TRAPPIST-1 after they noted its light dimmed several times (Turbetet al., 2016). This implied there were objects orbiting the star which obscured the light from the star and thus the dimming effect. The second step involved substantiating these observations by establishing whether these objects were actual planets. One of the three exoplanets deemed capable of harboring life was discovered using transit signals. According to Gillon et al (2017), astronomers mounted the High Acuity Wide field K-band Imager (HAWK-I), which is an infrared viewer installed on the Very Large Telescope (VLT) in Chile (Turbetet al. 2016). These two instruments found strong light curves around TRAPPIST-1 and that was a clear indication of an observed eclipse. There were several light curves and it was challenging to relate them to a single exoplanet, hence the scientists conducted various photometric follow-ups. Twenty days later, the light curves were more precise leading to the discovery of four new transiting planets, which are, TRAPPIST-1d, TRAPPIST-1e, TRAPPIST-1f, and TRAPPIST-1g. The following phase included conducting a global MCMC analysis of these transits as observed by Spitzer (Kane, Hinkel& Raymond, 2013). This study led to the discovery of more planets as free stricture for the six interior planets.

In the third phase, they discovered that 5 exoplanets (b, c, e, f, and g) are equal to planet earth in terms of size, and the other two exoplanets (d and h) have the same size as planet Mars (which has a radius about half that of Earth) and Earth. Another discovery made by the astronomers was that these planets were very close to the dwarf star. The resultant terrestrial orbital penchant is about the 90° angle, which is a clear indication that the co-planar system is seen nearly edge-on. This makes them orbit TRAPPIST very fast with the innermost planet completing the orbit within only 1.5 days and the farthest taking 20 days. The scientists confirmed that the two innermost planets are engulfed in hydrogen and that they are rocky just like planet earth (Alibert & Benz, 2017). One side always faces the dwarf star though its atmosphere may distribute warmth to the other side. Finally, Kane, Hinkel, and Raymond (2013) outline other methods of discovering exoplanets other than transit signals as used in this case.  They include direct imaging, microlensing, timing, and radio velocity.

Personal Discussion and Analysis

To begin with, it is quite intriguing to understand that some planets that are outside the solar system can possibly harbor life.  It was a common expectation that life could be discovered on other planets within the solar system but this possibility has not yet been realized. Secondly, this study by Gillon et al. (2017) proves that technology has advanced tremendously. NASA’s Spitzer Space Telescope that was used to discover TRAPPIST is significantly more powerful as a result of advancement in technologies. Additionally, use was made of ground-based telescopes in Chile and other places around the world. Another intriguing aspect of this discovery is the fact that the exoplanets orbit their dwarf star very fast. A period of 1.5 days to 20 days is a lot shorter than what we are used to in the solar system. This raises other questions such as the existence of seasons among these exoplanets (Kane, Hinkel& Raymond, 2013). Basically, seasons are a result of the earth orbiting the sun with an inclined axis. The earth takes quite a lot longer to pass through its seasons which gives an opportunity for climatic change and other developments to occur. Will a similar situation be witnessed with the exoplanets revolving around TRAPPIST-1? Similarly, it is important for astronomers to establish whether the exoplanets spin on their own axes to form day and night as it is experienced on planet earth.

This discovery represents a milestone in the quest for the answers regarding whether there are other beings that exist outside planet earth. According to Chiang and Laughlin (2013), scientists’ and astronomers’ main question has been whether the human race is alone and if there are other habitable zones outside our solar system. Scientists have for a long time strived to find life outside planet earth with extraterrestrial beings as they are displayed in fictional movies. In the 20th century, scientists had indicated the probability of planet Mars harboring life. The main challenge to that quest was the inability to identify water vapor on this planet. This implies that the TRAPPIST 1 discovery is quite important to astronomers since they have discovered the prerequisite of water on these exoplanets. The discovery of these exoplanets shows that scientists could be close to getting feasible answers to their quest regarding the existence of life outside planet earth.

This discovery does not only contribute to astronomy but also to other disciplines such as astrobiology. Biologists will be in a position to understand that humans can exist under conditions other than the ones found on earth. Solar system science as it has now advanced will stand us in good stead to discover other systems that are probably found within the galaxy. MacDonald et al. (2016) also say that there has been a lot of anxiety regarding the existence of life outside planet earth. Actually, this was accelerated by the myth or rather the theory of extraterrestrial beings. The human race has always wanted to know the answers to these pressing questions of whether other planets can support life. As aforementioned, the film industry has been awash with fictional movies showing extraterrestrial beings and even humans visiting other planets. Similarly, there was also a suggestion of humans relocating to other planets due to population growth and depletion of resources on planet earth. Therefore, this discovery has awakened such memories and society is waiting to see the developments and how it will respond to such expectations. Therefore, the TRAPPIST-1 discovery is a major event that does not only affect the scientific world but also our entire society.


Alibert, Y.,& Benz, W.(2017) Formation and composition of planets around very low mass stars. Astron. Astrophys,598,L5.

Chiang, E.,& Laughlin, G. (2013).The minimum-mass extra solar nebula: in situ formation of close-in super-Earths. Mon. Not. R. Astron. Soc.,431,3444–3455.

Gillon, M., et al. (2017). Seven temperate terrestrial planets around the nearby ultra cool dwarf star. TRAPPIST-1.Nature, 542.

Kane, S. R., Hinkel, N. R.,& Raymond, S. N. (2013). Solar system moons as analogs for compact exoplanetary systems. Astron. J. 146,122.

MacDonald, M. G. et al(2016).A dynamical analysis of the Kepler-80 system of five transiting planets. Astron. J,152,105.

Turbet, M.,et al.(2016).The habitability of Proxima Centauri b II. Possible climates andobservability. Astron. Astrophys,596,A112.