6 April 2007

The Green Sun

Confused by the title? I'm not trying to make an April Fool here. We have indeed witnessed the Green Sun. This video of the setting Sun from a site atop Mt. Autore (altitude 1,850 meters) in Italy has captured a green flash while the Sun was setting. How can the Sun turn green? Why does it occur? When can we observe this phenomenon?


(The time between frames in the gif image above varies from over one minute in the beginning to about one second as the flash becomes visible. If the image is not changing try to refresh the page.)


It is quite difficult to observe the Green Flash. It usually occurs during sunrise or sunset. This phenomenon is caused by the atmospheric bending or refraction of sunlight. Like a weak prism, the Earth's atmosphere breaks white sunlight into the seven colours, bending red colours slightly and green and blue colours through increasingly larger angles. When the sky is clear, a green flash just above the Sun's edge can sometimes be seen for a second or so, when the Sun is close to the horizon.

The above image was taken at the western horizon of Madagascar


This image of Green Flash was taken at the La Silla Observatory, in Chile, on October 15, 2005. The sun has almost set behind the mountain ranges of the western Chile when the Green Flash was observed.

Note: Click on the pictures for a better view.

Picture of the Month - April 2007


Brilliant Venus, slender crescent Moon, and lights along the Ponte 25 de Abril, which is a 2.3 km long suspension bridge across Tagus river glow against the western twilight in this lovely Moonset scene from Lisbon, the capital city of Portugal, recorded on March 20, 2007. In fact, such serene views were enjoyed across planet Earth this week, as the young Moon remained near the setting Sun following a partial solar eclipse, and Venus ruled as the evening star. Because of strong Earthshine - light from the sunlit Earth - even the Moon's night side is clearly visible in the picture.

5 February 2007

Picture of the Month - February 2007


This is dedicated to my friend who was asking me to change the usual topic - Astronomy. This brilliant photo was taken just a second before the Sand Storm that took place at Sumatra Island, Indonesia. This photo was found in a digital camera which was found about one month after the disaster.

28 January 2007

Goddess of Love - Venus

Hi everyone. This is the right time for us to see a Goddess with our own eyes – it’s the Goddess of Love. Goddess of Love is nothing but the planet ‘Venus’. Venus is the Greek Goddess of Love and Beauty. The Planet is named so because it is the brightest object in the sky let alone Sun and Moon. The picture below shows the planet Venus taken by a spacecraft.



Venus is the brightest object because its atmosphere consists of carbon dioxide and thick clouds of Sulphuric Acids which covers the planet completely. We can never see the surface of Venus unless we go into its atmosphere. Due to this reason Venus acts as a ‘Green House’. Thus the atmosphere of Venus reflects more than 95% of the light from the sun making it the brightest object in the sky. During the early periods Venus was confused for a UFO. The bright star on the top left of the picture below is the Planet Venus. We can clearly see that Venus is very bright compared to the other stars.



Venus is one of the two Inferior Planet (the other being Mercury). Inferior planets are simply planets whose orbits are within the orbit of Earth. Since Venus is the Inferior Planet we can only see the planet near the Sun i.e. either before sunrise or after sunset. When Venus is seen in the morning before sunrise it is called as the ‘Morning Star’ and when it is seen in the evening after sunset it is called as the ‘Evening Star’.

We can see Venus through our naked eye. It looks like any other star but no star can match its brightness. When you look at the planet through a telescope you can see special phenomenon which can only be noticed by the inferior planets. But Mercury is too close to the Sun and so only Venus exhibit this character very clearly. So far this phenomenon has only been noticed in the Moon, yet it is more special in Venus. This phenomenon is nothing but the ‘Phases of Venus’. It is no different from that of the Moon. Just as Moon, Venus changes its phases from ‘New Venus’ to ‘Full Venus’ and again back to ‘New Venus’. But this effect can only be viewed through a telescope.

When Venus is behind the Sun we can see the full phase of Venus. As Venus moves through its orbit it reduces its shape into a Gibbous, just like Moon. When Venus is exactly at right angles to Sun and Earth we can see Half-Venus. And as Venus continues to move around the sun and as it comes in-between the Earth and the Sun, it reduces its shape to a cresent and finally a new-Venus, exactly as that of the Moon. Yet, there is something different in its formation of phases which makes it phenomenon. During the full phase, the Venus is usually behind the sun and hence it is smaller in size due to the longer distance from the Earth. But during the cresent, Venus comes in-between Sun and Earth and hence it appears larger in size. So as Venus goes around the Sun it not only changes its shape but also its size. This phenomenon could also be seen in Mercury but to a small extent.

The picture below shows the different phases and the sizes of Venus during April-May 2004.


When Venus is exactly in between in the orbit of Earth and Sun we can see its Transit. Transit of Venus is nothing but the movement of Venus on the surface of Sun. We can see Venus as a dark spot on the sun. The picture below shows the transit of Venus over the surface of Sun. The dark spot on the Sun in the left is Venus.


The first person to notice the Phases of Venus is Galileo Galilei with his newly invented telescope. We can now see Venus at this very day as the ‘Evening Star’. We can see the planet clearly with our naked eyes. It looks just like a star but look for the brighest in the west. It is so bright that you can see the planet even before it gets dark completely. The planet will be visible until an hour or so after sunset.

If you want to look at the phases of Venus go to a planetarium nearby.

3 January 2007

Picture of the Month - January 2007

Hi Friends! From this year on, I'll post some exciting pictures every month for you all.




This picture shows the full moon with Andromeda Galaxy(aka M13) in the background. This galaxy is only about 2.5 million LY (Light Years) away and it is known as the closest spiral galaxy to Milky Way. This entertaining image compares the zoomed in image of the galaxy and the normal sized image of the mooon with the same angular view. In the normal view this galaxy looks like a small, faint, fuzzy patch near the constellation of Andromeda.