Friday, 6 April 2018

Aries Training School in Observational Astronomy (ATSOA) 2018

The 10 days of ARIES Training School in Observational Astronomy (ATSOA) were packed with many activities. Every day we used to have three or four lectures and then data analysis sessions. During these sessions, we first learned about image cleaning i.e. Bias subtraction, Flat correction etc. Different operating systems like Linux, Fedora, and software called IRAF was installed in laptops by guides of each group. At ARIES every computer already had this software so we first tried to practice the image cleaning commands on them. Meanwhile, we also visited different telescopes at ARIES and Devasthal.

Day 2 - A visit to Solar Telescope

Day 6 - A visit to Devasthal telescopes 

1. (3.6m) Devasthal Optical Telescope.

2. (130 cm) Telescope

3. Liquid Mirror Telescope

Day 7 - A visit to Nainital

Day 10 - Project presentation. The project of our group was to do photometry of star-forming region Sh2-305. Its part of the second catalog made by astronomer Stewart Sharpless that's why the name.
The image we used was taken by Himalayan Chandra Telescope's TIRSPEC instrument, the TIFR infrared spectrometer, an imager which has 1 Mega Pixel CCD.

The data from that telescope was already dark subtracted so we started the cleaning process by making master flat. Then we subtracted the sky image from the raw image and divided it by master flat which gave us the cleaned image.

I happened to click a picture of the computer screen when we were practicing the commands in IRAF.

Next task was to do processing to get the instrumental magnitude of stars. For this, we did aperture photometry using different commands in IRAF. Then to get the standard magnitude of all-stars we did calibration and astrometry which again involved many commands in IRAF. 

Monday, 2 April 2018

ARIES Training School in Observational Astronomy (ATSOA) 2018 - Day 1

Day 1
19th March, 07:30am. 
I was ready with my bags to join the ten days school at ARIES, Nainital - ARIES Training School in Observational Astronomy (ATSOA) 2018 . Luckily it takes only an hour to reach ARIES by car. I looked out of the car window only once or twice during the journey and then I saw the ARIES check-post. Students were already there near the auditorium. I asked where to put my bags. After taking my bags downstairs in the room adjacent to the dining hall, I walked towards the Auditorium. The first lecture was by Prof. Hum Chand. After the welcome talk by ARIES director Dr. Anil Kumar Pandey he talked about celestial coordinates. Next lecture was given by Dr. Brijesh Kumar. He introduced himself as an Optical Astronomer at ARIES and told us about different concepts related to telescopes like focal ratio, plate scale, fast vs. slow telescopes etc. He also told us to read about how our eyes work because no telescope or detector is as good as our eyes. After these two lectures, we came out of the hall for a short break of tea and biscuits. 

The door to the Dining
Trees as viewed from
outside our rooms

During the tea break, we used to stand outside the auditorium and look at the beautiful site. I used to wonder while watching cars on the road that how small they appear and how small we are as compared to these hills and how small they are as compared to the size of Earth.

In the next lecture, Prof. Amitesh Omar told us about how detectors are arranged in a telescope. He talked for an hour only using the two chalkboards in the hall without any powerpoint slides. For lunch, we walked to the dining hall and after that, we had to attend one more lecture by Anjasha Mam who is the Senior Research Fellow at ARIES. I realized later that what she talked in an hour was equivalent to what we did in the data analysis sessions in the computer lab for a week! Her talk was on photometry and how the IRAF software is used to do image cleaning, processing and then photometry. After her talk, we were divided into groups of four or five students under the guidance of a Ph.D. scholar. Our guide was Rakesh Pandey sir, SRF at ARIES. I met with group members.  

I had only read that telescopes use CCD detectors and the data or image from it can be cleaned using different software including IRAF. I was unfamiliar with the commands used to process or clean the image. 

After a little conversation, all of us headed to see the 104cm Sampurnanand Telescope. It’s really awesome to watch the dome and telescope moving. The CCD used in the telescope has 1300×1340 pixels i.e. it’s a rectangular CCD and not a square one.


104cm Telescope with dome open

104cm Telescope with the dome closed

But the best part of the day came when I saw loads and loads of stars at night. The lights from the faraway houses were also beautiful. It was very very very cold. I can tell this because my roommates were shivering. I was not feeling very cold because I was wearing a lot of clothes plus a jacket with the hood cap and a shawl. I used to remain packed because I knew that I get cold very easily. We spent some time near the auditorium and talked about stars and constellation then we walked to the dining hall and to our rooms.

Thursday, 15 March 2018

11. Very Large Array

Very Large array (VLA) is situated in New Maxico, USA and is operated by NRAO (National Radio Astronomy Observatory).

The red dot is showing position of VLA on earth
Very Large Array is a collection of 27 radio telescopes, each 25m in diameter. They are distributed in a Y-configuration and each of these telescopes can be moved along the railroad tracks. In 2012 it was renamed as Karl G. Janskey Very Large Array after Karl Guthe Jansky who built his own 14.6m rotatable antenna and later in 1931 discovered radio waves coming from the center of our galaxy.

Very Large Array 
APOD May 14, 2006
Credit: Dave FinleyAUINRAONSF
VLA had been used for SETI (Search for Extraterrestrial Intelligence).
We know that our galaxy - Milky Way is the second largest in the Local Group, the first and third are M31 (Andromeda galaxy) and M33 (Triangulum galaxy) respectively. So astronomers pointed the VLA telescopes to look for radio signals of 21cm from these two galaxies but they didn't find any.

VLA radio telescopes also discovered the first Einstein Ring gravitational lens. In gravitational lensing, when a heavy object comes in front of a star, galaxy or quasar it bends the light coming from them and thus distorts is totally. Sometimes it forms a ring and sometimes multiple images. And the first Einstein Ring was made because the image of a quasar was bent by a galaxy in between.

Tuesday, 13 March 2018

10. Australia Telescope Compact Array (ATCA)

Australia Telescope Compact Array or ATCA is located in Australia and is operated by CSIRO.

The red dot on the right end of Australia shows the position of the radio telescopes.

ATCA has six 22m diameter antennas to detect radio waves from space.
Radio waves have the frequency range of 3kHz to 300GHz. These radio telescopes have parabolic dishes to reflect the radio waves to receiver.
The dish of the radio telescope is usually not solid because it would be a waste of money and time to build one. Radio waves can easily get reflected from a mesh just like from a solid surface because of their longer wavelengths.

Another difference that is seen between Radio and optical telescopes is that radio telescopes are usually an array of antennas working together just like ATCA has six Radio antennas.

One of the radio antennas at Australia Telescope Compact Array
The size of these antennas is big because a larger collecting area can help in detecting more faint sources.

Image credit: X-ray: NASA/CXC/Univ. of Hertfordshire/M. Hardcastle et al.; Radio: CSIRO/ATNF/ATCA

The above image is showing the enormous jet of energy released by the Supermassive black hole. It's a composite image showing the data from Chandra X-ray Observatory in blue and the radio data from ATCA in red.

Sunday, 11 March 2018

9. Fermi Gamma Ray Space Telescope

Fermi Gamma Ray Space Telescope orbits around Earth once per 95 minutes.

Fermi Telescope was launched on 11 June, 2008. And this year it completed 10 years in orbit. Previously it was called Gamma-ray Large Area Space Telescope (GLAST) but later in 2008 it was renamed to honour physicist Enrico Fermi.

It has two instruments on board-
1. Large Area Telescope (LAT)
2. Gamma-ray Burst Monitor (GBM)
Both of these instruments also contain many subsystems.

Fermi has detected the most distant Blazars that are 2.1 billion years old!

Friday, 9 March 2018

8. Suzaku Observatory

Suzaku was an X-ray observatory in a 96 minute orbit around earth.

Suzaku was launched on July 10, 2005. Before its launch it was known as ASTRO-E2. And it was the second launch mission of ASTRO-E observatory which was lost on 10th Feb, 2000 due to rocket failure which crashed into ocean with its payload.

The instruments on board Suzaku are-
1. X-ray Telescope (XRT)
2. X-ray Spectrometer (XRS)
3. X-ray Imaging Spectrometer (XIS)
4. Hard X-ray Detector (HXD)

Suzaku detected chromium and manganese elements in the intergalactic space - the space between galaxies of Perseus Cluster. The gas in cluster was very hot thus emitting X-rays. Suzaku's instruments detected these X-rays and split them into its component wavelengths. As every element has a different spectrum, the two atoms were identified.

This video describes more details about the discovery-

The mission was deactivated on 2nd September, 2015.

Wednesday, 7 March 2018

7. Swift Observatory

Swift observatory is in a 95.74 minute orbit around earth. Its NASA's Multi-wavelength space telescope.

NASA E/PO, Sonoma State University/Aurore Simonnet

It was launched on 20th November, 2004. Swift is named after a small bird. One of its mission is to detect Gamma Ray Bursts and their afterglows in X-ray and visible light. For this, there are three instruments on board Swift -

1. Burst Alert Telescope (BAT)
2. X-Ray Telescope (XRT)
3. Ultraviolet/Optical Telescope (UVOT)
Swift detects ~100 GRBs per year.

This year in January, Swift was renamed as Neil Gehrels Swift Observatory to honour Cornelis A. Neil Gehrels, an astrophysicist who left us on February 6, 2017.

It was the first image captured by the UVOT instrument - the pinwheel galaxy in UV and visible light.