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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The Perseverance Rover Landing on Mars in Indian Standard Time (IST)

 

Perseverance Rover Credit:NASA

Mars Perseverance Rover is all set to start the landing sequence and explore Mars from February 18^th. The 1025kg rover which will weigh only 384kg on mars is equipped with scientific instruments to take readings and samples of the Martian surface to answer the question, "Did life exists on Mars at some point in the past". The descent to Martian surface will start on February 18^th and here are the sequence of events that are planned.

The Perseverance Rover Landing on Mars in Indian Standard Time (IST)

For USA it will be 18th but for India it will 19th Morning

 Credit: NASA/JPL-Caltech

The red planet's atmosphere is very thin compared to earth, about 1% in volume, mainly made up of carbon dioxide. Even at this thin atmosphere, the heat shield protecting the rover will experience a temperature of 1300 centigrade during descent. The atmosphere breaking will slow the spacecraft descent to 1000km/h and when  at this speed the parachute is deployed, it will slow down the spacecraft further.

  Atmosphere breaking. Credit: NASA/JPL-Caltech

When the spacecraft is slowed down to 320km/h the parachute is detached, the instruments on the spacecraft guides, using radar and camera to safely land the rover on the Martian surface.

You can watch the events Live from NASA's YouTube channel.

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Sun as Blind(Bright) Spot

 

Blind Spot, something we are all familiar with and have experienced it one time or the other. With all the mirrors around in the car or truck there will be one area where we cannot see and we have to adapt and work around it. Sometimes its a matter of life and death. Something which we cannot observe even with mirrors, this got me thinking of astronomers and their mirrors, the telescope and blind spot ,that area where observation is not possible. Earth rotates on its axis every 24 hours and if a solar eclipse is happening in USA, we in India will be at the opposite side with nightfall, but at-least someone got to see the eclipse. But there are places in the sky where if some events happen nowhere on earth can we see or observe the event. This is the portion of the sky where the Sun is placed.

On a new moon day we cannot the see the moon, it's not that moon has vanished from the sky but its hidden in the glare of the Sun. When a celestial object is close to the Sun we call that object as, in conjunction with Sun. During new moon phase the moon is in conjunction with the Sun. This applies to planets too, planets Jupiter and Saturn were in conjunction with Sun in late January of this year and as you know by now, conjunction means close to the Sun. When planets are in conjunction with the Sun observations cannot happen and we have to wait for the planets to come out of Sun's glare. This can take from several days to months and during that time there is nothing that the earth bound astronomers can do but wait.

The dreaded wait, how many of you reading this article remember the wait for the emergence of COMET ISON in 2013. The COMET ISON was dubbed to be the comet of the century and was to be the brightest comet in the sky after its perihelion (close approach to Sun). The comet was observed and followed until it fell into the glare of the Sun, amateurs and professional astronomers waiting to see the reappearance never got the chance as the comet got disintegrated during its close approach to Sun. We had wonderful images before it went close to Sun, but as it got close to Sun all we could do was to wait for emergence as sun's glare hid the comet.

If we go back in time to 1994 and the event of great impact of comet Shoemaker Levy 9 on to the planet Jupiter, which proved Eugene Shoemaker's theory of the impacts by comets and asteroids on Planets are common, well in astronomical timeline of-course. The event took place in July and telescopes around the world were pointing at Jupiter and astronomers studied the event in great detail. At that time Jupiter was in the constellation of Virgo and the Sun was in the constellation of Gemini. Imagine if the same event would have taken place during conjunction of Jupiter with Sun, we would have missed the great event.

Its not only planets but stars and other celestial objects too that come close to the Sun in the sky during the year, reaching conjunction, and those objects also cannot be observed until they emerge out of the glare. For example ,in the month of February Sun is in the constellation of Capricornus and we cannot see the stars or the objects in the constellation due to the bright Sun.

In the month of January of 2020 the red star in Orion constellation, Betelgeuse, dimmed in brightness unexpectedly and astronomers were able to measure the brightness until it came back to its original brightness in April of 2020. This was a good opportunity to study the brightness variation of the star as Betelgeuse was well placed in the sky away from the bright Sun. The same event if it had happened in the month of June, you know where I am going with this, yes Betelgeuse will be in conjunction with Sun in June.

There are many such rare events that we could have missed if the event had taken place during conjunction with Sun, even the closest supernova in Large Magellanic Cloud which took place in 1987 if it had happened during conjunction.

Sun is a big blind spot for astronomers, even with their mirrors they will miss anything close to Sun. Astronomers take advantage of even the smallest window and try to learn everything they can, because they know that these are rare events. For astronomers there is no such thing as being at right time at right place, they have to make best of what they get.

Knowing this I am very sure that it will make us look at each event and night as a gift and accept it with a sense of gratitude.

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