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Kritti Sharma and Kunal Deshmukh, two undergraduate students in their third and fourth year respectively, have made a discovery that has made the entire institute proud. They discovered the closest asteroid flyby of Earth ever recorded without impacting the planet! The discovery was made just hours after the flyby using the data from the Zwicky Transient Facility (ZTF) at Caltech.

A representation of the Path of the Asteroid

Kunal and Kritti are a part of the IITB wing of GROWTH collaboration led by Prof. Varun Bhalerao from the Physics Department. Caltech leads the GROWTH collaboration which stands for Global Relay of Observatories Watching Transient Happen. It is an international scientific collaborative project in astronomy studying the physics of fast-changing events in the cosmos like supernovae, neutron stars or black-hole mergers and near-earth asteroids. Kunal and Kritti work on the objective of finding asteroids as part of the ZTF Solar System Working Group led by Caltech. This group has members from India, Taiwan, UK, and the US who collectively work on finding asteroids.     

A look into how the asteroid was detected:

The process begins in the Palomar Observatory, California, United States. Here, the Zwicky Transient Facility, a wide-field sky astronomical survey, uses a camera attached to the Samuel Oschin Telescope to survey the skies with the massive field of view of 47 square degrees. For comparison, the moon is about 0.2 square degrees when viewed from the earth. To capture such a wide field of view, the camera uses 16 CCDs (a CCD is an array of photosensitive capacitors) of 6144 X 6160 pixels each. Such wide-field facilities are designed to detect transient changes in the night sky—moving objects such as comets and asteroids, collisions between neutron stars, gamma-ray bursts and supernovae. These phenomena are referred to as transients.

Now, the asteroid detection process consists of three key steps.

1) Image capturing and processing – This step involves capturing a multitude of images, processing them into science images and vetting them using Machine Learning and Deep Learning algorithms to look for transients. The two classification problems here are real/bogus separation to separate astrophysical sources from artefacts and separation into different classes among the astrophysical sources. The challenge of real/bogus classification is the construction of a training set that is representative of nightly data across filters, sky location, and in the case of multi-CCD surveys like ZTF, possible variations between CCDs, as well as cross-talk. The real/bogus separation algorithms are trained using pictures of actual asteroid streaks, artificially injected streaks and false positives. This is done to remove biases which may creep into the classification during training and to ensure that no real transient goes unnoticed. The ML and DL algorithms eliminate a large number of images, which do not have any transients in them for sure. 

2) Scanning of images – This is where the team at IIT Bombay comes in. Experts are needed to inspect the shortlisted images manually and try to figure out whether it was a false positive. Close examination of these images involves looking for streaks, diffraction effects, reflections, reverse image subtraction errors, edges and cosmic rays. Other streaks may correspond to either satellites or asteroids. A satellite usually has a blurry end to the streak, whereas an asteroid has more well defined and clear endpoints. Such details are used to differentiate between satellites and asteroids. Thus the students at IIT Bombay manually scanned the data to find a near-earth asteroid which was the size of an SUV.

3) Verification through Minor Planet Center – MPC is a worldwide body responsible for verifying and cataloguing data about minor planets. This involves confirming their presence, calculating their orbits and their distance from the earth by astrometrical analysis. This third and final step confirms the discovery of an asteroid.

First Image of the asteroid as viewed from the ZTF facility

Significance of the Discovery

This discovery takes us one step closer towards understanding smaller (~50m or less) Near-Earth Asteroids (NEAs) which statistically pose no threat to humanity as a whole, but still cause significant damage as we saw in the case of Tunguska and Arizona. The discovery of one such NEA by Kunal and Kritti demonstrated how close extraterrestrial bodies can get without getting detected. The asteroid travelling at 12km/s missed the surface of the earth by merely 2950km. That is roughly the distance between Kashmir and Kanyakumari!

Every year we see undergraduates reaching further into the depths of research and technology. With increased collaboration between universities across the world and the sharing of infrastructure and technical knowledge, more such scientific discoveries can be made. Kritti and Kunal have proven that through such collaborations, even space exploration lies within reach of an enthusiastic undergraduate researcher. 

Kritti and Kunal both will soon be promoted to a more senior level in this program, to be precise from  “scanners” to “measurers”. But since Kunal is switching projects, we are left with Kritti for now from IIT Bombay who will be going to the next level of her space endeavour and we extend our heartfelt congratulations to Kunal and Kritti for their achievement.

What’s in stock for the future?

GROWTH India Telescope

Kunal and Kritti made history by becoming the co-discoverers of “2020 QG” but the majority of the credit goes to ZTF, Caltech. In the future, however, when more researchers like Kunal and Kritti start working with the GROWTH India telescope in Ladakh, Indian researchers working with data collected by Indian telescope will bring all the name and fame to our beloved nation. Kritti has already decided, her next goal is to employ her skills with Prof. Varun Bhalerao and team, to write planning and observational scripts (read codes) for the GROWTH India telescope to enable data collection from space. Sure, this target comes with its own challenges but Kunal and Kritti believe that with dedication and perseverance, all hurdles can be tackled. They are positive that the GROWTH team in India have an excellent chance of future breakthroughs with the exceptional skill set of the Indian team combined with the clear skies of Ladakh. 

Message from the team!

“Genuine interest in Observational Astronomy with some background in amateur astronomy and motivation to learn new concepts is the best combination for someone who would like to work on this project. I have been just two weeks into this research project and I have discovered 6 asteroids so far, all of them are published in MPECs.”

— Kritti Sharma

“I started off as just an amateur astronomer and with time, I was still able to do a lot in terms of research. Of course the opportunities you get play a big role, but given that, astronomy is not that long a shot if you have a strong enough interest, basic knowledge and the willingness to work hard. ”

— Kunal Deshmukh

GROWTH-India is a partnership between the Indian Institute of Astrophysics, Bangalore and the Indian Institute of Technology Bombay, with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India ( It is a part of the international GROWTH collaboration. Caltech’s ZTF is funded by the NSF and an international collaboration of partners. Additional support comes from the Heising-Simons Foundation and from Caltech. ZTF data are processed and archived by IPAC. NASA supports ZTF’s search for near-Earth objects through the Near-Earth Object Observations program.

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