14 July 2014

Mars and Spica so close yet so far

Mars and Spica will be just one degree apart today evening. We can see the red planet mars and Spica shining bright in the southwest sky after sunset. The pair is easy to spot due to their colour difference, mars will be red and south west of mars will be blue-white star Spica. Although they appear just one degree apart from each other, the closeness ends there.
The distance from earth to these two celestial bodies are truly immense.  Mars after coming close earth on April 14th, it is slowly moving away from us and now mars is close to one AU.  Spica is at a distance of 15810494 AU form us, one AU is the distance between earth and Sun, which is 150 million kilometres. As we can see, the difference is immense. If the skies are clear, in the evening, we will enjoy the view and now we know they are so close yet so far.

07 July 2014

City Constellations

It happens every time, we attend an astronomy talk or see an astronomy documentary and after finishing that when we come out, we always involuntarily look up at the night sky. We expect to see star-studded sky as seen in that talk or documentary, diamonds in the sky. 
Credit: ESO
However, as it turns out due to high light pollution, this is what we end up getting in the city skies. Light pollution is increasingly taking stars away from us. There is no immediate solution for the light pollution issue although efforts are on around the world.
Until then we have make use of what few stars we have under city conditions. I always advice new comers interested in night sky, to go and get familiarize with the constellation whenever they get time. Although sky may look disappointing at beginning with hand full of stars in the night sky, we can in fact make that work in our favour.
It will be easy to start and recognise the basic pattern of the constellation when there are few stars. Once we have the basic shape with the help of bright stars, when we have dark skies, it will be easy to pick up rest of the constellation.
We will take couple of examples here of constellations, bright ones that can be seen easily under city conditions.  These days at 8pm we can see the bright constellation Ursa Major in the north, even with light pollution its easily spot seven stars in the constellation. Now this forms the outline of the Ursa Major, if we are familiar with the bright stars, under dark skies we can pick up full constellation, which will help in finding deep sky objects.
We can see only few stars in Ursa Major, but I am sure you can spot all the seven bright stars.
Once we are familiar with bright stars, we are ready for dark skies; here is how it will look under light pollution free conditions.
Along with bright stars, we have many stars that complete the constellation.
Like Ursa Major, there are similar constellations that we can spot even with light pollution, and spending some time getting to know the bright stars and the constellation outline will really help when we have dark sky conditions, sometimes it is difficult for newcomers to recognize the patterns with thousands of stars around.
 Cygnus also has bright stars that make the constellation easy to pick up in light polluted areas. Deneb is the brightest star in the constellation and the stars that make the outline are close to or brighter than third magnitude. The constellation lies in the mily way band and its good idea to use light pollution to our advantage and get familiar with the basic shape of the constellation, under dark skies it is a highly star-studded region. Seeing the constellation under darks skies shows what light pollution is doing to our night sky.
Under Dark Conditions:
One more wonderful constellation is Scorpius in the south. Along with Scorpius, the constellation of Sagittarius lie in the most star rich region of the night sky, as these two constellations lie in the region of centre of our galaxy, the milky way. These two are easily visible from the city skies, shows in a very frustrating way on how light pollution is affecting astronomy enthusiast. This is a region with numerous star clusters and nebulae and a favourite region for astrophotographers.
Under Dark conditions we can see the milky way...
These are just couple of examples to show how we can use light pollution to our advantage and to show how it is affecting our night sky.
With a basic star map, keep practicing in identifying the constellations with the help of bright stars, which will really help under dark skies.

01 July 2014

Occultation Demonstration setup at ABAA

At ABAA, we try to make concepts of astronomy simple so that everyone can visualise and understand. This setup I made at ABAA using materials that we can find easily and we can build this at very low cost and fast. The setup is to show occultation concept, consists of a motor, a light source that acts as a star and a dick attached to motor to show an object coming in front of the star, Occulting the star.

Moon Occulting Venus 

Occultation is an astronomical event when one astronomical object comes between observer and a distant object. For example, moon in its journey in the night sky comes in between background stars and us, this we call moon is occulting stars.

I made the video with external lights on and off, to show the setup working. With lights on, we can see the disk coming in front of the light source and Occulting the Star and with lights turned off we can simulate night sky and we can measure star light disappearing and re appearing. Using different sizes of disc, we can show that occultation helps in determining the size and shape of an object using the time of appearance and disappearance to the star.