Light Pollution: Limiting Our View Of The Stars

Light pollution is making it increasingly difficult to see the stars. Caused by human-generated illumination, light pollution is causing the sky to glow, washing out the stars. In fact, if the brightening of the night sky continues at its current rate, a child born in a place where 250 stars are visible will only be able to see 100 stars on their 18th birthday.

Light pollution is causing the sky to glow, washing out the stars

The impact of light pollution on stargazing is significant. In locations with high levels of light pollution, such as suburban areas near cities, most stars become invisible against the overhead glare from artificial light sources. Even the diffuse radiance of the Milky Way, which is the combined glow of 100 billion stars, can be dimmed to near nothingness.

The magnitude of a celestial object refers to its apparent brightness. Light pollution sets a limit on the faintest observable objects in the night sky, causing fainter stars and diffuse objects to be washed out. Each integer reduction in magnitude corresponds to a 2.5x increase in brightness. As a result, a magnitude +2 star appears 2.5 times brighter than a magnitude +3 star.

The problem of light pollution is worsening over time. Globally, light pollution has been increasing by 9.6% annually, with Europe and North America experiencing even higher rates of increase at 6.5% and 10.4%, respectively. This exponential growth rate means that the brightness of the night sky is doubling roughly every seven to eight years. According to a study published in the journal Science, if there are 250 visible stars in the sky when a person is born, they will only be able to see 100 stars by their 18th birthday.

The number of visible stars is decreasing

The impact of this is that fewer stars are visible to the naked eye. The apparent brightness of an object in the sky is called its magnitude, and for most people, the naked-eye limiting magnitude in ideal skies is about +6.5. Each integer reduction in magnitude corresponds to a 2.5x increase in brightness. So, a magnitude +2 star appears 2.5x brighter than a magnitude +3 star. As light pollution washes out fainter stars, it sets a limit on the faintest observable celestial object for a given location.

The consequences of light pollution are not trivial. It is affecting the lives of many different animals, as well as being an expensive waste of power. It also means that humans are losing the ability to use the stars for navigation and telling the seasons, which was an important part of our culture.

If the brightening of the night sky continues at the current rate, a child born in a place where 250 stars are visible will only be able to see 100 stars there on their 18th birthday. This is a significant loss of visibility and a reminder of the impact of light pollution on our view of the stars.

Light pollution has negative consequences for the well-being of plants, animals and humans

Light pollution is a growing problem, with the night sky becoming around 10% brighter each year on average. This has a negative impact on the number of stars we can see, with the brightness of the sky doubling roughly every seven or eight years. If there are 250 visible stars in the sky when someone is born, by the time they're 18 they'll see only 100.

Plants are also affected by light pollution. Disrupted circadian rhythms can affect flowering times and pollination processes, ultimately impacting the ecosystem's health. Artificial light can reduce native plant growth, reproduction and fruit production by distracting, repelling or killing pollinators, reducing flower visits and the amount of pollen transported, and restricting the movement of seed-dispersing animals across the landscape.

Light pollution also has negative consequences for humans. The stars are an important part of our culture, and we are losing the experience of looking up at the night sky and using it for navigation and telling the seasons.

The night sky is becoming brighter each year

The brightening of the night sky is increasing at an exponential rate. Research has found that globally, light pollution increased by 9.6% a year over the study period. This means that sky brightness is doubling roughly every seven or eight years. If this continues, a child born in a place where 250 stars are visible will only be able to see 100 stars by their 18th birthday.

Light pollution sets a limit on the faintest observable celestial object for a given location. In astronomy, the apparent brightness of an object is called its magnitude. This logarithmic brightness scale can seem strange at first, with larger positive numbers corresponding to fainter objects. However, with practice, it is possible to become very proficient at estimating magnitudes by memorising a number of familiar stars. For most people, the naked-eye limiting magnitude in ideal skies is about +6.5. Each integer reduction in magnitude corresponds to a 2.5x increase in brightness.

The problem of light pollution is not consistent across the world. For example, on average, Europe saw a 6.5% increase in light pollution annually, whereas North America saw a 10.4% increase. However, the overall trend is clear: the night sky is becoming brighter, and the stars are becoming harder to see.

Light pollution is increasing at an exponential rate

The impact of light pollution on our view of the stars is significant. Light pollution washes out fainter stars and diffuse objects, setting a limit on the faintest observable celestial object for a given location. The apparent brightness of an object in the sky is called its magnitude, and each integer reduction in magnitude corresponds to a 2.5x increase in brightness. So, a magnitude +2 star appears 2.5x brighter than a magnitude +3 star.

The loss of our view of the stars is more than just a romantic or aesthetic concern. As Dr Ashley King, a Future Leaders Fellow at the Natural History Museum, notes, 'The first humans could look up at the sky and use it in so many parts of their lives. Whether it was for navigation or telling the seasons, the stars are an important part of our culture.'

Additionally, light pollution has real and negative consequences for the well-being of many living things, including plants, animals, and even humans. It is also an expensive waste of power.

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