URANUS RETROGRADE MOTION 2023

Uranus is in retrograde motion now, starting from 30th Aug 2023. All planets move from west to east with reference to stars, this is the direct motion. Months before reaching the opposition, we notice the daily angular motion of the outer planet, in this case, Uranus keeps reducing and at a point it appears stationary. The planet’s motion will be eastward until the stationary point.

After this we see the planet moving westward with respect to stars and the angular motion also increase but in westward direction. This movement, westward, we call it retrograde motion.

Months after Opposition, the opposition of Uranus will take place on 13^th November 2023, again we observe the angular motion reducing and becoming stationary at one point, this will be Jan 28th 2024, and the planet will start moving eastward again with slowly increasing in angular motion as days passes.

Uranus will move 4 degrees west in the retrograde motion before turning east again.

Using binocular or telescope you can track the movement and measure the changes. Even with necked eye it is possible but interval of each observation should be far enough (in days) to notice the changes.

If you pick delta and rho Arietis, you can notice the movement of Uranus from delta to rho…

 

Happy Observing 

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Comet PANSTARRS closest to Earth on July 14th

 

Comet PANSTARRS, C/2017 K2, will be closest to earth on 14th July 2022. The comet at its closest to earth will have a distance of 1.8AU or 269,276,167km in the constellation of Ophiuchus, this distance puts the comet beyond the planet Mars orbit.. The comet is bright enough to be seen in binoculars and small telescopes, the comet has a magnitude of 8. The comet PANSTARRS is well placed for observation, at the time of Sunset the comet will have an altitude of 45 degrees from the horizon, this gives plenty of time to observe, the comet will set at 3:45am.

Comet PANSTARRS, C/2017 K2, is easy to spot in the sky thanks to its closeness to the M10 globular cluster. The comet will be well within the field of view of binoculars, 20X80, until 18th July. Globular cluster M10 is a bright object at 6.6 magnitude, once M10 is the field it won’t be difficult to spot the fuzzy comet . The size of the comet will be roughly the size of M10. 

On 15th July the Comet PANSTARRS, C/2017 K2, will be closest to M10 with a separation of 25 arc minutes. At this small separation the comet and the globular cluster will be in the same field in the telescope, making it a wonderful sight and also to compare the brightness and size of the comet. Hope you all get a chance to view and photograph the comet. 

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Best Times to See Milky Way Galaxy from India

The Milky Way is one of the brightest and famous arms of our galaxy. This is in the region of Scorpius and Sagittarius constellations, this region is also the center of our galaxy. It is a magnificent view when seen under dark skies away from the city light pollution. The Milky Way will appear as a hazy band in the sky, rich with stars, with the brightest region at Sagittarius and dimmer toward north. Many people mistake it for clouds, if you get the doubt, wait for some time and the Milky Way will move along with the stars.

The band of the Milky Way extends from constellations Sagittarius, Sagitta, Cygnus, Cassiopeia to Perseus in the north. To enjoy the full Milky Way band, a place with an unobstructed view of the horizons is essential.        

The Milky Way will be in opposition in the middle of June, that means as the Sun is setting in the west, the Milky Way will be rising in the east. June and July are the best months to enjoy the Milky Way all through the night. I thought making this list of rise, meridian transit and set times of the Milky Way would be useful, so I made one.

Here are the Times for viewing the Milky Way.  

June 15: The Milky Way will rise at 7pm, it will reach meridian, highest altitude in the sky, at midnight and the Milky Way  will set at 5:30am. The Milky Way will be visible all night. 

July 15: The Milky Way will rise at 5pm, reach meridian, highest altitude in the sky at 10:30pm and the Milky Way will set at 3:45pm.

August 15: Milky way will be at meridian, highest altitude in the sky at 8:30pm and the Milky Way will set at 2am.

September 15: By the time the Sun sets, the Milky Way will be at meridian, highest altitude in the sky and it will set at midnight.

October 15: Milky Way will set at 9:30pm.

November 15: Milky Way will set at 7:30pm.

The Sun will be in Sagittarius in December so the Milky Way is not visible. 

Jan 15: The Milky Way will rise at 5am, in twilight.

Feb 15: The Milky Way will rise at 3am.

March 15: The Milky Way will rise at 1am.

April 15: The Milky Way will rise at 11pm and will reach meridian, highest altitude at 4:30am.

May15: The Milky Way will rise at 9pm and it will reach meridian, highest altitude at 2:30am.

As the best months to view the Milky Way galaxy are in the months of June and July, this will make it difficult for south India due to the arrival of Monsoon. To see the band full night or to photograph the band, it is better to move to places where the monsoon has not yet reached. 

You can use the list when going on a trek in a remote place. Check the times during the month and enjoy the view of the Milky Way. 

     

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Sunday Activity at ABAA: Talk on James Webb Space Telescope

After closing three times due to lockdowns and weekend curfews, ABAA is now back to meeting and conducting activities on Sunday evenings at Planetarium. Last Sunday at ABAA there was a talk on the James Webb Space Telescope given by Ravindra Aradhya, President of ABAA.  This was the part one of the series and concentrated on the optics of James Webb Telescope. The idea behind the talk was on how Amateur Astronomers can relate their making of telescopes with JWST. 

As all telescope makers know, the first and most important part is selecting and buying glass blanks. The selection of glass blanks is done based on the need, thermal expansion is one most important of all the criteria. From Speculum metal, used by Newton and William Herschel, Plate glass, a familiar glass to all amateurs, Pyrex used by many amateurs and observatories to Zerodur used by observatories. The talk covered in detail on the advantages and disadvantages of each type of mirror. 

Beryllium used in the making of the James Webb Space telescope was chosen again with the same criteria. The ability of Beryllium to keep the optical shape intact in different temperatures, this is something all Amateur Telescope Makers (ATM) can relate to and has first had experience in that. 

The next concern is the weight, Beryllium was chosen keeping this also as priority. At ABAA members are very familiar with J. Texerea’s mirror diameter to thickness ratio of 1:6.  This is followed for smaller mirrors but the ratio of 1:10 is considered from larger mirrors. This is done to reduce the weight of the primary mirror. For observatory class mirrors, weight is reduced with hollow mirrors with honeycomb support. We can see this kind of mirror used in Hale telescope at Palomar Observatory. 

After covering the topic of choice of glass and weight reducing methods in mirror making the talk covered in detail on the shape of the James Webb Space Telescope, the Hexagon, The geometry and advantages of multi mirrors with Hexagon mirrors was discussed in detail. When it comes to aligning the mirrors, amateurs can understand the importance and difficulties in collimating a telescope. Many were fascinated to know that the hexagon mirrors are already being used in keck telescopes

Next was on the topic of type of telescopes and amateur astronomers know the two kinds of optics most used, the Newtonians and the Cassegrains. The optics and light path was discussed in detail and members could relate the light path in James Webb telescope. Little more time was spent on understanding theThree-mirror anastigmat optics of James Webb. 

It became easier for members to relate their telescope making experience of grinding, polishing and testing. The method of polishing, difficulties and the precision is something that amateur telescope makers are too familiar with. Members now could appreciate and admire the engineering that went into making of JWST.

The surface error that was allowed and achieved for JWST mirrors was 20 nanometers. This number does not make much sense, it's just a number. Until we convert the 1.3 meter segment into nanometers, this will be 1,300,000,000 nanometers, now there were a lot of raised eyebrows in the room. The deformity on the surface should not exceed 20 nanometers at temperature of 40 kelvin (-233 C). To visualize this, our DNA is just 2 nanometers in diameter. Members and audience were excited to realize how small an error astronomers and amateurs work on.

Finally the topic of coating was discussed. Amateur telescope makers, after polishing and testing their mirrors, send the mirror for aluminum coating. Different kinds of coating 

and their applications were discussed. The sliver, aluminum and gold coating is used for different wavelengths. Since JWST is going to study mainly in InfraRed, gold is the best choice. The talk later covered briefly the process of coating mirrors.

         

 

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How to find Largest Asteroid passing closest to earth?

 

How to find Largest Asteroid passing closest to earth? Is a good question. The asteroid 2001 FO32 will pass very close to earth and it will be visible in moderate sized backyard telescopes, 8inch aperture and above with dark skies. The asteroid in the eyepiece or in the photograph will appear as a tiny star indistinguishable from the surrounding stars. This makes it a challenging object to spot and confirm. Keeping this in mind I have prepared a star chart and also provided the co ordinate systems of the object so that you can enter this in your GOTO telescope and spot the asteroid.

The apparent motion of the asteroid is fast enough for the motion to be detected with respect to background stars. Only way to confirm that you were successful in spotting the asteroid it so make observations at regular intervals and check for the movement. Taking photos of the region at regular intervals and blinking the photos will help to confirm the asteroid.

Here are the details of the asteroid 2001 FO32 path from 20^th of March to 21^st of March, this includes chart with hourly movement of the asteroid. The Time and Chart is for Indian Subcontinent. 

Asteroid 2001 FO32 will rise in the constellation of Lupus at 10:50pm IST on 20th March, Moon will be in the sky at the time of asteroid rising but moon will set at midnight giving lot of time to track the Asteroid 2001 FO32.

Above are the co-ordinates for GOTO telescopes to spot Asteroid 2001 FO32. The Asteroid will rise at 4am on 22nd morning making it difficult to spot in low horizon.

Happy hunting.

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Sunday Talk at ABAA: The Ways of Magnetic Fields

The Ways of Magnetic Fields

Talk Given By Raviraj Shinde, Member ABAA and  doing his post graduation in geo magnetism and magnetohydrodynamics at Indian Institute of Science (IISc). 

The magnetic field of the earth has a dipolar structure, with its north magnetic pole close to the south geographic pole, and south magnetic pole close to the north geographic pole. Due to its dipolar structure, it was considered earlier that there may be a giant bar magnet inside the earth. But since the earth's magnetic field has been there for billions of years and the temperature inside the earth is very high that permanent magnetism cannot sustain there. Then in the early 20th-century dynamo theory came into the picture. The Dynamo theory explains how fluid flows of conducting fluid can sustain and intensify given the initial magnetic field inside a planet or a star like a sun.

Earlier it was thought that Earth's magnetic field only helps to navigate, but it has to do a lot more than that. Earth's magnetosphere has been protecting Earth's atmosphere and indirectly all the life on earth from harmful radiation in the form of solar winds. Also, the interaction of the magnetosphere with this solar wind produces beautiful aurora near the Earth's poles. The very interesting phenomenon; the reversal of Earth's magnetic field has not been understood yet. Apart from The Earth Jupiter, Saturn, Uranus, and Neptune are known to have their own magnetic field. Some other planets and natural satellites were having their own magnetic field which is not there today.

Finally, our own star The Sun has its magnetic field which is very dynamic and capricious. The sunspots were the earliest manifestations of the magnetic field of the sun. This magnetic field is also maintained by the dynamo action in the convection layer, but unlike the Earth's case conducting fluids here is plasma not liquid metal. J.C.Maxwell was the first to observe the relation between 11 solar cycles and maximum disturbance of terrestrial magnetic fields. Sunspots are formed near the equator where azimuthal fields are very intense and these high-intensity magnetic fields suppress turbulent convective motions towards the photosphere. Making the region cooler and hence darker. Since the formation of sunspots is symmetric about the sun's equator and the direction of magnetic flux changes over 11 years so this 11-year solar cycle is related to the reversal of the azimuthal magnetic field. Magnetic flux loops that produce sunspots rise above the photosphere up to the corona layer of its atmosphere. The magnetic field lines in this layer are under tremendous stretching such that they frequently snap and rejoin, in between they release a large amount of heat energy which raises the temperature of the plasma in the corona level to 10^6K. This causes a reduction of density so that solar wind is generated which travels through the solar system spiraling around the sun with a velocity of a few hundred kilometres per second.

Field of magnetohydrodynamics which studies all these and many more phenomenon related to astrophysics. But it has its own limitations, journey started nearly about a century ago has not yet come to an end. And still today researchers are working on dynamo theory to get ourselves closer to the reality.

The discussion went on covering magnetic fields of planets and its importance for atmosphere and ways of studying the magnetic fields of rocky and gaseous planets.  

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Brightest asteroid Vesta in Opposition

 

The brightest asteroid Vesta is in opposition today, March 4^th 2021. It is easily visible through small binoculars even in the light polluted city conditions. Vesta will rise in the east as sun sets in the west. sun, earth and Vesta will be in the same line with earth at the center, this is called opposition. 

Vesta Opposition

Vesta is now placed in the constellation of Leo very close to the bright 3^rd magnitude star Theta Leonis. You can spot the asteroid Vesta just 1 degree 15 minutes north east of Theta Leonis. Around 8pm the asteroid will be well placed for spotting but if you have buildings or trees blocking the horizon then you may have to wait until 10pm to spot the asteroid.

Vesta in Leo

Looking through the binoculars or telescope the asteroid will appear as a star, with no hint of shape. This is because of the distance between the earth and Vesta which is now at 1.36 AU(203,453,379km) and the size to the asteroid is 262km in radius.

Vesta Position in Leo

Vesta will be closest to the earth on March 9 2021.

Following Vesta:

With a pair of binoculars or telescope you can notice the movement of Vesta. Choose a couple of stars in the field of view and make a sketch of the field or you can take a photo of the field. With regular observations over the days can show the movement of Vesta with non-moving stars in the field.

Vesta is moving fast at 1 minute of arc in March. If you continue to track Vesta every night or every couple of days you will notice that the distance moved by Vesta is slowing down and in middle of April 2021 Vesta will appear stationary for couple of days and slowly increase the speed as days follow.

Vesta tacking 

You will also notice that from March to April the asteroid Vesta will be moving towards western direction in the Sky, but from first week of May the asteroid will appear moving towards eastern direction in the sky. This is due to the fact that Vesta will be in retrograde motion until April and appear to move towards west and later it will start moving in east. 

Along with angular velocity and direction you will also notice that the asteroid Vesta magnitude also starts dropping. Now in March 2021 Vesta magnitude is 5.9 and post retrograde, that is after April the magnitude of Vesta will drop to 7.2 and it will keep dropping. You can notice this drop in brightness comparing with the stars you have chosen for reference.

Finding and tracking Vesta not only improves the skill of finding objects in the sky using star hopping, it will also make the hobby interesting helping in understanding the concepts like field of view, angular motion, retrograde motion and Magnitude system.

Good Luck Observing!

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