15 November 2016

Aldebaran occultation by Moon tonight


Most of you would have enjoyed the supermoon yesterday evening and most of you have taken wonderful photos. Today evening we have one more exciting astronomical event and that is occultation of star Aldebaran by Moon. Tonight moon will occult giant Aldebaran. since both objects are bright enough it will be easy to observe even with naked eye, a pair of binoculars and of course with telescopes. I would suggest you get all the setup ready before the given time and wait for the event rather than waiting until last minute. The chart below will be helpful to show the entry point and exit point of the star during occultation. 

Astronomers have used occultation to know about the size, shape and distance of the objects. Aldebaran is the brightest star in the constellation of Taurus, it is at a distance of 65 light years from Sun. By measuring the time taken for that star from disappearing and reappearing and getting reports from different parts of the world we get a pretty good idea of the shape of the object. Today evening moon will occult Aldebaran from the south near the crater Tycho. Use the chart below to follow the star from disappearance to its re emergence. Try and measure the time taken between the star disappearance and re emergence using stop watch. All the best and hoping for clear skies. 



Time of disappearance 15:26:46 UT
Time of re emergence 15:57:45 UT


 Moon in the constellation of Taurus and close to star Aldebaran.

Moon about to Occult the star.

Aldebaran re emerging after Occultation.


14 November 2016


A Hype called Super Moon:


I am sure you have come across this Super Moon through print media, TV Channels, blogs, Face Book, Twitter or through friends. Today's Full moon will be the closest in 70 year and if you miss it now, you will have to wait until 2034 for next Super Moon. Moon in its orbit around earth come close to earth and this is called Perigee and moves farthest from earth called Apogee every month. Perigee can happen at any phase of the moon, it may be in Crescent, Half or gibbous phase. When Perigee and Full moon phase coincides, the name given is Super Moon.


What to Expect?


Looking at this picture of Moon can you tell if the Moon is bigger or smaller? 



You will agree just by looking at the picture its not possible, you will need reference, something to compare with or measure the size. This is the same thing that will happen when you go out tomorrow and look at the Moon. Lets for a moment see the numbers involved. This month perigee distance is close to 3,56,509 km and when we compare this with last perigee month's perigee in the month of October, distance which was close to 3,57,861 km the difference is just 1352 km. This when we convert it to angle subtended by moon in the sky and the difference from two perigee is 0.127 arc minutes. This as you can imagine is not possible to notice just by looking. You may need to photograph this full Moon and take photographs of upcoming full moons with the same settings and compare the difference.


This is also the implies to the brightness of the moon today. If we have not really observed the moon form some time it will not be evident to casual observer the difference in brightness in this light polluted conditions.


I would suggest that people should observe the moon not during full moon, but to observe in crescent to half moon and take guidance from local astronomy group. If you come to ABAA on any Sunday evening, you can learn about night sky and also when there is moon in the sky you can use our telescope and learn to observe moon and other celestial objects.

20 October 2016

Highest Resolution Image of Eta Carinae


VLT Interferometer captures raging winds in famous massive stellar system


An international team of astronomers have used the Very Large Telescope Interferometer to image the Eta Carinae star system in the greatest detail ever achieved. They found new and unexpected structures within the binary system, including in the area between the two stars where extremely high velocity stellar winds are colliding. These new insights into this enigmatic star system could lead to a better understanding of the evolution of very massive stars.


Led by Gerd Weigelt from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, a team of astronomers have used the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory to take a unique image of the Eta Carinaestar system in the Carina Nebula.
This colossal binary system consists of two massive stars orbiting each other and is very active, producing stellar winds which travel at velocities of up to ten million kilometres per hour. The zone between the two stars where the winds from each collide is very turbulent, but until now it could not be studied.
The power of the Eta Carinae binary pair creates dramatic phenomena. A “Great Eruption” in the system was observed by astronomers in the 1830s. We now know that this was caused by the larger star of the pair expelling huge amounts of gas and dust in a short amount of time, which led to the distinctive lobes, known as the Homunculus Nebula, that we see in the system today. The combined effect of the two stellar winds as they smash into each other at extreme speeds is to create temperatures of millions of degrees and intense deluges of X-ray radiation.
The central area where the winds collide is so comparatively tiny — a thousand times smaller than the Homunculus Nebula — that telescopes in space and on the ground so far have not been able to image them in detail. The team has now utilised the powerful resolving ability of the VLTI instrument AMBER to peer into this violent realm for the first time. A clever combination — an interferometer — of three of the four Auxiliary Telescopes at the VLT lead to a tenfold increase in resolving power in comparison to a single VLT Unit Telescope. This delivered the sharpest ever image of the system and yielded unexpected results about its internal structures.
The new VLTI image clearly depict the structure which exists between the two Eta Carinae-stars. An unexpected fan-shaped structure was observed where the raging wind from the smaller, hotter star crashes into the denser wind from the larger of the pair.
Our dreams came true, because we can now get extremely sharp images in the infrared. The VLTI provides us with a unique opportunity to improve our physical understanding of Eta Carinae and many other key objects”, says Gerd Weigelt.
In addition to the imaging, the spectral observations of the collision zone made it possible to measure the velocities of the intense stellar winds. Using these velocities, the team of astronomers were able to produce more accurate computer models of the internal structure of this fascinating stellar system, which will help increase our understanding of how these kind of extremely high mass stars lose mass as they evolve.
Team member Dieter Schertl (MPIfR) looks forward: “The new VLTI instruments GRAVITY and MATISSE will allow us to get interferometric images with even higher precision and over a wider wavelength range. This wide wavelength range is needed to derive the physical properties of many astronomical objects.

News Credit:ESO

30 December 2015

Looking and Observing


When crowd gather around binoculars and see the Moon for the first time through binoculars, their reaction is that, the moon looks the same even without the aid of binoculars. Ask them to spend some time at the binoculars and slowly they will start enjoying the view, as they start to Observe the details on the moon surface. This is true even with low power telescopes.

This is the difference between looking and observing which I am sure most people would have experienced in their initial stages.

Even when it comes to other celestial wonders, the situation is the same spend very little time at eyepiece and there is little to be seen but spend more time at eyepiece and details we can see are amazing.

Let me give an example of difference between looking and observing. Take a look at the image and at first sight it appears the same, little closer look will show couple of differences but as on spending time and studying the details will show lots of differences in the images.


When at eyepiece spend as much time as possible studying the object, for example if it is the moon study the shape of the craters, the shadow patterns at different phases of moon and so on. If it is a galaxy, study the dust lane, the arms and structure.  Cluster offers their own challenges like resolving and types of stars in the cluster. We cannot pick up such fine details if we are in a hurry, more time at eyepiece more details we will pick up.  Change the magnification, use different filters, study the object in different telescopes, you will be amazed on how on objects appears in different magnification, filters and apertures.



I always advice people not to fill the pages with number of objects they saw in a single night, but to fill the pages with the details on what they observed. There is no rush, take time in observing and keep challenging yourselves on how much more details you can see and minimum aperture needed to see the details. 

Why just Look when you can Observe!

08 June 2015

Venus and Jupiter Conjunction on July 1st



In the western evening sky we have 2 bright objects, one closer to horizon is Planet Venus and next is Planet Jupiter. As we are observing from past couple of weeks, we have noticed something curious, Venus and Jupiter are getting closer to each other.



These two planets appear getting close to each other, this is as seen from earth, the fact is Venus, the brightest planet in the sky and Jupiter the largest planet in the solar system are 0.5AU and 6AU respectively from earth (1 Astronomical Unit =14,95,97,871 km).  

We will continue to track these planets in coming days and we will notice that the separation will get even smaller. The separation of these planets as seen from earth is measured in angles.

In the middle of June the separation between Venus and Jupiter will be 14 degrees and on 20th the separation will be reduced to 6 degrees.




Minimum separation between Venus and Jupiter will happen on July 1st with a separation of 24 minutes, close enough to fit both planets in field of view of telescope. Venus and Jupiter will set at 9:30pm on 1st July.




25 February 2015

Neptune Conjunction


Neptune will be in Conjunction with Sun on February 26th. This means that Sun and Neptune will be close to each other.  At this point, the planet will be farthest from earth and the distance between earth and Neptune will be 463,75,33,991 km that is 31 times the distance between earth and Sun.
We will  have to wait until last part of March to see the planet in the morning skies when it rises one hour before sunrise. A good pair of binoculars or a small telescope is good enough to spot the planet Neptune.
Here are star charts to find the planet Neptune towards end of March.



23 February 2015

Mercury Greatest Elongation


Mercury will reach greatest elongation on the morning of February 24th with maximum separation of 27 degrees from Sun as measured from earth. Mercury is difficult planet to spot and observe, as it stays very close to Sun most of the time. Best times are near elongation for spotting and observing the planet. This is because the angular separation between Sun and the planet Mercury will be large and we can see the planet away from Sun’s glare.  
 

Since it will be low in the horizon, just 27 degrees, better search for a place, where there is clear view of the eastern horizon not obstructed by buildings or trees. Early morning 6am will be good time to spot the planet as the planet would have reached an altitude of 14degrees.

After elongation, the planet will start getting closer to Sun, meaning the angular separation between the planet and Sun keeps decreasing and towards end of March the planet will be lost in Sun’s glare again.