On average, from any point on the earth’s surface, the unaided human eye can see around 6,000 stars in the night sky, provided excellent weather conditions and very dark skies. All contained within our own galaxy, these 6,000 stars are but a small fraction of the 300 billion stars estimated to make up the entire Milky Way. From Malta, the densest region of the Milky Way can be seen traversing the sky from south to north, especially in the summer months. However, even though the Maltese islands are graced with some of the best weather conditions in the world, our own galaxy is now visible from just around 10 per cent of the entire islands, and this percentage is only expected to further dwindle.
Light pollution map of the Maltese Islands, with red showing higher levels of light pollution and blue/black showing lower levels. Source: VIIRS (2017)In the 1850s, Malta was considered as one of the prime locations for astronomical observations. In fact, renowned English astronomer William Lassel set up the world’s second largest telescope of the time in Tigné, and discovered 600 new nebulae, or clouds of gas and dust, in a few years from our islands. Over the course of the past few decades, however, a drastic increase in the amount of ill-planned lighting has seen the quality of our dark skies plummet, such that from most of Malta’s urban regions only a few brighter stars can be seen at night.
One might ask if decreasing light pollution is of interest to astronomers only. No one can dispute that outdoor lighting is essential, and it is glaringly obvious that lack of such lighting would prove to be an inconvenience and a considerable safety concern. Light pollution, however, can be tackled while keeping our roads just as lit as they are today, and at a lower financial expense.
In fact, the main sources of light pollution are light fixtures installed with little regard for efficiency, facing sideways or even up towards the sky. In truth, such instalments result in a severe waste of energy, since they would entail a much lower energy consumption rate to equally light the ground if they were installed properly, facing downwards.
Additionally, reducing overall sky glow would also result in a lower impact on light-sensitive fauna which thrive on our islands, as well as an increase in our own quality of life. It is now recognised that bright lights at night disrupt the circadian rhythm, the 24-hour day-night cycle that affects many organisms’ physiological cycles, including ours. Increased levels of light pollution, and the resultant disruption of the circadian pattern, have been confirmed to be directly correlated with increasing levels of insomnia and depression, as well as cardiovascular disease. In fact, the American Medical Association listed increased overall levels of light at night as a health hazard and carcinogen in 2012.
Next time you visit one of the few remaining dark sky locations in Malta, such as Dwejra, Dingli, Mtaħleb or Miġra l-Ferħa, sit back and take in the vast beauty of the cosmos. Try to spot the majestic arching band of the Milky Way, brightest towards the south, and understand that such sights could be visible from the privacy of our own homes, all over the island. It just takes a small amount of effort to plan our outdoor lighting better, but the resulting improved dark sky heritage, together with health and environmental benefits, would be truly astronomical.
Josef Borg is currently a PhD student within the Institute of Space Sciences and Astronomy, University of Malta, and also vice-president of the Astronomical Society of Malta.
Sound bites
• Cassini spacecraft takes final plunge into Saturn’s upper atmosphere: Back in 2010, Cassini began a seven-year mission extension during which it completed many moon flybys while observing seasonal changes on Saturn and its largest moon, Titan. In April 2017, Cassini was placed on an impact course that unfolded over five months of daring dives; a series of 22 orbits that each pass between the planet and its rings. Called the Grand Finale, this final phase of the mission has brought unparalleled observations of the planet and its rings from closer than ever before. On September 15, 2017, the spacecraft made its final approach to the giant planet Saturn. But this encounter will be like no other. This time, Cassini will dive into the planet’s atmosphere, sending science data for as long as its small thrusters can keep the spacecraft’s antenna pointed at earth. Soon after, Cassini will burn up and disintegrate like a meteor.
https://saturn.jpl.nasa.gov/mission/grand-finale/overview/
• Pluto surface features officially named. The International Astronomical Union (IAU) has officially approved the names of 14 geological features on the surface of Pluto. All of these remained devoid of officially-sanctioned names two years after the flyby of NASA’s New Horizons spacecraft that obtained high-resolution images of the dwarf planet’s surface for the first time. The IAU is empowered by the world’s astronomers as the sole naming authority for astronomical objects and its features. Previously, a number of informal names were being given to several of these regions by astronomers. Some of these names, such as Cthulhu Regio, Balrog Macula, or Spock crater, were related to science fiction and fantasy literature and clearly out of the boundaries of the IAU’s traditional naming themes.
http://www.skyandtelescope.com/astronomy-news/first-pluto-features-officially-named/
Did you know?
• Like other large galaxies, the Milky Way is a cannibal galaxy. Larger galaxies can feed on smaller galaxies if they wander too close by, and the Milky Way is no exception. As a large galaxy takes up smaller ones in this fashion, its overall mass increases, making it more likely to take up further galaxies in the future.
• Our solar system is in the suburbs of our galaxy. We are on one of the outer spiral arms of the Milky Way, called the Orion-Cygnus arm. Looking towards the centre of our spiral galaxy, we see a band of brighter light in the sky due to the higher concentration of stars towards the centre of the galaxy, referred to as the galactic bulge.
• Our galaxy itself is speeding in space, and it’s on a collision course. In a few billion years, the Milky Way and the Andromeda galaxy, the only larger galaxy than the Milky Way in our neighbourhood, will merge to form a new, larger galaxy termed Milkdromeda.