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 will be in between earth and Neptune.  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.

21 February 2015

Venus and Mars Conjunction

In the evening twilight after sunset, we find Venus shining bright in the western sky. These days we find a red star very close to Venus, in fact this is not a star but red planet Mars. On 22nd of February these two planets come closest to each other, at just below half a degree. Our moon measures half a degree in the sky.

If we continue observing these planets for few days more, we can see that Venus is moving up in the sky and Mars is getting closer to Sun.
Hope you all get a chance to see this during the weekend.

23 September 2014

Happy Equinox Everyone

Today, September 23rd at 7:51am, Sun reached Zero declination, if we observe Sun’s position at Equator on this day, we will see Sun will be exactly overhead at noon. In coming days if we keep observing the Sun’s position we will notice that Sun is moving towards south with each passing day. Sun will reach southernmost point on December 21st. 
Sun reaching the Zero declination point is called Equinox. This happens twice in a year; first one will be on March 20/21 and second will be on September 23rd.
From March, the Sun will be in northern hemisphere of the sky reaching northern most point on June 21st at 23.50 and returning to Zero declination in September. From September Sun will be in Southern hemisphere of the sky reaching extreme south point of -23.50 on December 21st , from December Sun will start moving towards north and reach Zero declination on March 21st .
March Equinox is called Vernal Equinox and September Equinox is called Autumnal Equinox.