26 September 2017

Remembering names of Moon Phases


We are seeing moon getting brighter in the evening sky every day from the last new moon on 20th. With each passing day more area of the moon is illuminating and we can see lot of features on the moon. Many people have confusion when it comes to naming the phases of the moon, so here is a something useful to remember the names.


First, we start with couple of days after the new moon, the phase we are seeing is crescent phase a thin sunlit part of the moon and since the sunlit part is getting bigger with passing days we call it waxing crescent. This is from old English meaning something that grows, here the brighter side is growing.

Waxing crescent moon. Sunlit part towards west.

Next is First quarter, this phase happens when the Sun, earth and the moon align in such a way that Sun and moon are at right angles as seen from earth. We can seen this in the evening sky, on the evening of the first quarter at sunset, we can measure the angle between Sun at the horizon and the moon and the angle will be 90 degrees or close to 90 degrees depending on actual time of alignment.

First Quarter moon. Sunlit part towards west.

Between First quarter and Full Moon, when more then half of the moon is lit up by sunlight we call it gibbous phase and since the brightness is increasing its waxing gibbous phase.

Waxing gibbous moon. Sunlit part towards west. 

After the first quarter comes the Full moon phase, which we are all familiar with, in astronomy we call moon is in opposition. The moon and the sun are on the opposite sides of the earth, if they are exactly aligned then we have a lunar eclipse.

Full moon


From new moon phase the moon was in the sky before the sunset and would set late as the days passed until Full moon when it rises at sunset. After this the moon rises late after sunset and the brightness starts decreasing.

Waning gibbous moon. Sunlit part towards east.


Since its decreasing and more then half is lit, but not fully lit, we call it waning gibbous phase. After that moon reaches last quarter again attaining right angle with the sun. This means the moon will by high in the sky at sunrise. The next phase in waning crescent where we see thin lit surface of the moon and finally reaching new moon phase.

From new moon to full moon, we see the lit part is towards west and from full moon to new moon, we see the lit part towards east, the lit part will be towards the sun.

Now I think there is no problem in telling the phases below,

Last Quarter moon. Sunlit part towards east.
Waning crescent moon.Sunlit part towards east.


  

01 March 2017

Venus Watch at ABAA

After I announced about Venus being in its brightest phase many people showed interest in looking at Venus through telescope following Sunday. On Sunday we were happy to see public and members coming in large numbers to watch Venus in crescent phase. After sunset we put the telescope out and focused on to Venus, members of ABAA were present there in showing and explaining all about Venus. Using the 6 inch telescope of ABAA people saw amazing sight of the crescent phase, and immediate reaction of most people was “is it Moon?”, that lead to discussions and members helped them in getting idea of orbits and phases of inner planets.

ABAA is open on all Sundays from 5:30pm and always ready to show the celestial wonders to people and members showing interest. People can come and see moon and planets, learn about them and also learn about telescopes and how to use them. Observing through a telescope has steep learning curve, its best to learn about them before buying or going out for observing and ABAA can really help in that section. ABAA can help in choosing the best telescope for you or help you in building your own telescope, you can come to ABAA on any Sunday evening and discuss your needs.

Here are photos of Sunday sessions of Venus watch









 

    

15 February 2017

Watch Brightest Venus on Friday


After Sunset in the western twilight sky we see a bright star outshining all the starts in the evening sky, this is the planet Venus. The visual apparent magnitude of the planet Venus is now -4.6 and the apparent magnitude of brightest star in the night sky, Sirius, in the constellation of Cains Major is -1.46 this makes Venus 18 times brighter than Sirius. 
Brocken Inaglory, Venus-pacific-levelled, CC BY-SA 3.0
On February 17th Venus will reach its brightest crescent phase and this is called Greatest Illuminated Extent, the amount of illuminated crescent and the angular diameter of the planet Venus. Venus will have an angular diameter of 39 arc seconds and fraction of illumination is .273 of the angular diameter. After this day the illuminated side will start decreasing and we will see the crescent getting thinner. By second week of March the illuminated fraction will be only .085 of the diameter of the planet and magnitude would have come down to -4.4 still brightest in the evening sky. 

View Through the Telescope on 17th of Feb



View Through the Telescope on 10th March



The planet Venus will slowly fade into glare of the Sun and will reach inferior conjunction on March 25th. In April we will see Venus in early morning sky before sunrise and again the Greatest Illuminated Extent will happen on April 30th. Time to take out the telescopes and observe Venus in coming days, if you don't have one you are always welcome at ABAA on Sundays evening and see the Venus through our telescope. Venus sets at 9pm now and in middle of March the planet will set at 7:30pm.




03 February 2017

Sunday Talk "Lesson Learned:The 2003 Space Shuttle Colombia Accident"




Hi All

ABAA in collaboration with JNP presents this Sunday talk titled "Lesson Learned:The 2003 Space Shuttle Colombia Accident" and will be delivered by Christopher Kirchhoff who investigated the Columbia Space Shuttle disaster which happened in February 1, 2003. He will speak about the circumstances that led to the Space Shuttle disaster in which Indo-American astronaut Kalpana Chawla was killed along with crew of the Shuttle. All are Welcome.

Date: 5/2/2017
Time:4:30 Pm
Venue: Jawaharlal Nehru Planetarium, Bangalore.


All are welcome.

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