Why Do Stars Twinkle at Night?I'm often asked Why do Stars Twinkle? So I'll answer the question with an article and few tips for astronomers to eliminate star twinkling.
Why do Stars Twinkle? The fact is that they are not, in reality, twinkling at all. The light from the star has travelled for many millions of years through space, nice and steadily. When the photons of light meet the Earth's atmosphere, all the twinkling occurs.
In the atmosphere, the light is reflected, bent, shimmered, and shaken by turbulent particles from the top of the atmosphere down to your eye. From our point of view, the light from a star will appear in a single location, and then milliseconds later, it will be distorted to a different spot from the turbulence.
Stars would not seem to twinkle if we viewed them from outer space, a planet or the moon that did not have an atmosphere.
Astronomers measure the amount of twinkling and call it scintillation, although it is commonly known as seeing, and it may also be noticed when looking at the moon - even though the moon doesn't twinkle, you'll be able to see the effects of the turbulent atmosphere by the way it wobbles.
A turbulent atmosphere can also be seen on a hot day; you can see a haze just above a road, car park, or even over a car. This is also tied to the thermal distortions in the air.
Why Don't Planets Twinkle Like Stars Twinkle
Stars seem like a single point in the sky because of the great distance between us and them. This single point is extremely affected by atmospheric turbulence. Planets, however, are much closer and appear as disks. Although we can't resolve them as disks with our eyes, the difference in distance means the twinkling averages out, and we see a more stable light in the sky.
How to Combat Poor Seeing
The most efficient means of preventing poor seeing is eliminating the atmosphere. Therefore, space-based telescopes such as Hubble are essential.
Ground-based telescopes, on the other hand, can't be moved into space; there are some techniques that they can use to help get rid of the turbulence in the atmosphere. Adaptive optics use lasers and powerful computers to physically distort the telescope's mirror many times a second to compensate for the turbulence in the atmosphere.
For most people, on the other hand, it isn't practical to move into space, and we can't afford pricey adaptive optics, so there isn't a lot we can do to get rid of poor seeing. We can reduce the effects of atmospheric turbulence by following these simple guidelines.
- Leave your scope outside to cool to the ambient temperature, eliminating air currents within the tube.
- Observe on grass rather than concrete. Concrete absorbs more heat from the Sun and radiates it to the air above it for longer.
- Air currents stay low to the ground, so lifting your scope on a platform is a good suggestion.
- If you construct an observatory, make it with thin materials like wood that can cool fast.
- The geography of your observing site affects how air behaves. Being near the sea will give you calmer air than near a range of hills, where the air is forced up, causing turbulence.
Another method that can be utilized is known as "lucky imaging", which dates to pre-war naked-eye observations of moments of excellent seeing, followed by observations of the planets on cine film after World War II. The method depends on the fact that every so often, the effects of the atmosphere can be negligible, and by recording large numbers of images as quickly as possible, a 'lucky' excellent image can be picked out. This is most frequently accomplished via a webcam or planetary digital camera.
