Monday, August 8, 2022

Daylight observations

Although most of astronomical observations are conducted at night, when the Sun is below the horizon, there are some celestial objects that are bright enough to be detected even during the day.

The brightest of these is obviously the Sun (remember never to look at it directly to not damage your eyes), followed by the Moon.

In perfect weather conditions and at the right time of year, you can also see a few planets in daylight. The easiest to observe is Venus, one of the brightest celestial objects. More than with the naked eye, the planets during the day are observable with a telescope. In the image, for example, Venus is shown, but it is also possible to identify Jupiter and Mars.

Even more complex to observe during the day is the International Space Station. Depending on its location in orbit, the ISS may become the third brightest object in the sky, after the Sun and the Moon. However, being able to locate it is extremely complex: the station moves along the sky very quickly and you must therefore know its exact position at all times.

There are three other categories of celestial objects that can be detected during the day. These are brighter than the planets and the ISS and therefore easier to see in the sky, but their nature makes it difficult, if not impossible, to predict when they will be visible.

Of these, comets are the only ones where a kind of prediction can be made. When a new comet is discovered, estimates are made of how bright it can become (although predicting the exact brightness of a comet is almost impossible). It can happen that a comet becomes so bright that it can be observed during daylight hours. The last such example was Comet mcnaught in 2007.

Very rare and unpredictable are the meteors. In most cases, these are dust particles or small stones that burn into the atmosphere, giving rise to shooting stars. When the object entering the atmosphere is of the order of a meter, the wake created by the burning in the atmosphere is bright enough to be seen during the day. One of the most well-known and recent examples is the 2013 Chelyabinsk meteorite, which had a diameter of about twenty meters.

The last class of objects visible during the day are supernovae. These, however, are very rare. The last supernova that was visible to the naked eye during the day was the Tycho Supernova, which exploded in November 1572 and remained visible to the naked eye during the day for two weeks.

Credit: Pete Lawrence (Digital Sky).

0 commenti:

Post a Comment