07 March 2011

Sunspot photos

Dilip Kumar shares these photos that he took of the Sun

He writes
" The photos 336 and 37d, were taken in the evening directly without filter, since its safe to shoot when the Sun is close to horizon with Red disc, without the glare.

Its better to take many shots in Manual mode with different exposures since, its difficult to judge the correct exposure. On the other hand if Programme or Auto modes are used, the correct exposures may not be possible, since if the disc of the Sun is small the camera will try to take reading from the larger outer area and resulting in Sun getting over or under exposed.

When longer focal length lens is used, the Sun's disc will be larger and better exposures can be achieved, but, its still better to bracket the exposures to get best photo. Its always better to use lower ISO to take advantage of getting finer grains ( 200 to 400 ) since Sun is bright, a fairly good shutter speed can be achieved with larger openings of the aperture, as the Sun is a far object, Depth of field is negligible.

In case of longer focal length lens or with compact cameras with 12X or higher zoom, its better to use a tripod, stand or place the camera on some support like wall or take support of a tree to avoid shake.

The photos, 124d & 135 were taken with a flter in place (Baader), it was taken in midday with manual exposurre. The filter sheet is cut to the size of the lens diameter and it is mounted between two KG Card sheets, which is attached to the front of the lens with scotch tape.

All pic.s were taken with 300mm lens with 1.7x teleconverter, which works out to 500mm. Even with small compact camera with fairly good zoom like 12X and above, fairly good photos can be taken."

03 March 2011

IISER Kolkata researchers Crack the Mystery of the Missing Sunspots

In 2008-2009, sunspots almost completely disappeared for two years. Solar activity dropped to hundred-year lows; Earth's upper atmosphere cooled and collapsed; the sun’s magnetic field weakened, allowing cosmic rays to penetrate the Solar System in record numbers. It was a big event, and solar physicists openly wondered, where have all the sunspots gone?

Now they know. An answer is being published in the March 3rd edition of Nature.

"Plasma currents deep inside the sun interfered with the formation of sunspots and prolonged solar minimum," says lead author Dibyendu Nandi of the Indian Institute of Science Education and Research in Kolkata. "Our conclusions are based on a new computer model of the sun's interior."

For years, solar physicists have recognized the importance of the sun's "Great Conveyor Belt." A vast system of plasma currents called ‘meridional flows’ (akin to ocean currents on Earth) travel along the sun's surface, plunge inward around the poles, and pop up again near the sun's equator. These looping currents play a key role in the 11-year solar cycle. When sunspots begin to decay, surface currents sweep up their magnetic remains and pull them down inside the star; 300,000 km below the surface, the sun’s magnetic dynamo amplifies the decaying magnetic fields. Re-animated sunspots become buoyant and bob up to the surface like a cork in water—voila! A new solar cycle is born.

For the first time, Nandi’s team believes they have developed a computer model that gets the physics right for all three aspects of this process--the magnetic dynamo, the conveyor belt, and the buoyant evolution of sunspot magnetic fields.

"According to our model, the trouble with sunspots actually began in back in the late 1990s during the upswing of Solar Cycle 23," says co-author Andrés Muñoz-Jaramillo of the Harvard-Smithsonian Center for Astrophysics. "At that time, the conveyor belt sped up."

The fast-moving belt rapidly dragged sunspot corpses down to sun's inner dynamo for amplification. At first glance, this might seem to boost sunspot production, but no. When the remains of old sunspots reached the dynamo, they rode the belt through the amplification zone too hastily for full re-animation. Sunspot production was stunted.

Later, in the 2000s, according to the model, the Conveyor Belt slowed down again, allowing magnetic fields to spend more time in the amplification zone, but the damage was already done. New sunspots were in short supply. Adding insult to injury, the slow moving belt did little to assist re-animated sunspots on their journey back to the surface, delaying the onset of Solar Cycle 24.

"The stage was set for the deepest solar minimum in a century," says co-author Petrus Martens of the Montana State University Department of Physics.

Colleagues and supporters of the team are calling the new model a significant advance.
"Understanding and predicting solar minimum is something we’ve never been able to do before---and it turns out to be very important," says Lika Guhathakurta of NASA’s Heliophysics Division in Washington, DC.

While Solar Max is relatively brief, lasting a few years punctuated by episodes of violent flaring, over and done in days, Solar Minimum can grind on for many years. The famous Maunder Minimum of the 17th century lasted 70 years and coincided with the deepest part of Europe's Little Ice Age. Researchers are still struggling to understand the connection.

One thing is clear: During long minima, strange things happen. In 2008-2009, the sun’s global magnetic field weakened and the solar wind subsided. Cosmic rays normally held at bay by the sun’s windy magnetism surged into the inner solar system. During the deepest solar minimum in a century, ironically, space became a more dangerous place to travel. At the same time, the heating action of UV rays normally provided by sunspots was absent, so Earth’s upper atmosphere began to cool and collapse. Space junk stopped decaying as rapidly as usual and started accumulating in Earth orbit. And so on….

Nandi notes that their new computer model explained not only the absence of sunspots but also the sun’s weakened magnetic field in 08-09. "It's confirmation that we’re on the right track."

Next step: NASA’s Solar Dynamics Observatory (SDO) can measure the motions of the sun’s conveyor belt—not just on the surface but deep inside, too. The technique is called helioseismology; it reveals the sun’s interior in much the same way that an ultrasound works on a pregnant woman. By plugging SDO’s high-quality data into the computer model, the researchers might be able to predict how future solar minima will unfold. SDO is just getting started, however, so forecasts will have to wait.

Indeed, much work remains to be done, but, says Guhathakurta, "finally, we may be cracking the mystery of the spotless sun."

This research was funded by NASA’s Living With a Star Program and the Department of Science and Technology of the Government of India.

Scoure and Image credit NASA.

01 March 2011

ABAA in News

ABAA and JNP's effort of creating awareness in astronomy and telescopes during the National Science Day exhibition that was held on Feb 28th was covered by print and television media. Here is a photo from Times of India news paper dated 1/03/2011, in which ABAA member Priya S Srivatsa is explaining telescope to public. The writeup can be found on page 18 titled

ABAA again thanks all the volunteers who have helped in spreading awareness among students and public and hopes for continued support.

Eclipse photos on Annual report of JNP

Mr Prakash Subbanna, Vice-president of ABAA, shared this info with ABAA that his eclipse photos have been printed on the Cover pages of JNP's Annual report. One is a collage of Annular Solar Eclipse which occured on 15th Jan 2010, the picture was taken from Dhanushkodi, Kanyakumari and the other is of the Total Solar Eclipse which occurred on July 26th 2009. The photo was taken from Bodh Gaya, Bihar. Mr Prakash Subbanna has sent his thanks to ABAA for all its support.

Original Images of the eclipses.

Moon and Venus - the second and third brightest objects in the sky have always evoked interest among people. When they come close together it gets all the more interesting. Just like the eclipses which are rare events thanks to the orbital properties, Moon and Venus appearing together - at least at a convenient time for us to observe - are somewhat rare. Though not as wonderful or celebrated, they nevertheless attract attention. That's what happened today morning. The two celestial bodies were separated by less than a degree and it was indeed a great sight. Managed to take a few pictures of the event. The pictures were taken from Lalbagh.

The pictures of course, don't do any justice to the real thing as it happens quite often.

National Science Day exhibition from JNP and ABAA

On the occasion of Nation Science Day, held every year on Feb 28, JNP and ABAA made an effort to popularize astronomy among people. JNP had put up exhibits of different types of telescopes and ABAA volunteers were there to explain the working of telescopes and their application in different branches of astronomy.

From morning ABAA volunteers helped students and public understand the working of telescopes in detail. They explained how the refractors and reflector telescopes work, their optics, light ray path and also covered advantages and disadvantages of refractors and reflectors.

It was great to see that even on a busy week day ABAA members took time out and came to help people understand telescope and create awareness on Astronomy. ABAA thanks all its volunteers for making time and helping the cause. ABAA thanks JNP for their support during the event and hopes of more such activities.

ABAA Volunteers:

Namratha S

Priya S Srivatsa

Bharath A J

T S Madhava

Here are few Photos of the event

Priya S Srivatsa explaining refractor telescope

Namratha S explaining telescope to students

Namratha S explaining telescope to students




Namratha explaining optics to public

Bharath A J explaining refractor

Kamalesh explaining Newtonian telescope

Madhava T S, long time member and active member of ABAA.

Bharath giving details to media

Namratha explaining telescope to media

Students looking through telescope.