Ultraviolet emissions from novae are a special class of transient astronomical event that causes the sudden appearance of a bright, apparently new star that slowly fades over weeks or months, during their outburst.
| Photo Credit: SPECIAL ARRANGEMENT

Astronomers from the Indian Institute of Astrophysics (IIA) have spotted far ultra violet (FUV) emissions from novae for the first time in the neighbouring Andromeda galaxy.

The ultraviolet emissions from novae are a special class of transient astronomical event that causes the sudden appearance of a bright, apparently new star that slowly fades over weeks or months, during their outburst.

The IIA team used ultraviolet imaging telescope (UVIT/AstroSat) data of the Andromeda galaxy from public archives, to look for FUV emission from novae during their dormancy.

AstroSat is India’s first dedicated space astronomy observatory and the UVIT is one of the primary payloads which was developed by IIA.

According to the Department of Science and Technology, the team stumbled upon the novae around their eruption phase.

It added that the team, consisting of Judhajeet Basu (IIA and Pondicherry University), Krishnendu S. (IIA and Amrita University), Sudhanshu Barway (IIA), Shatakshi Chamoli (IIA and Pondicherry University), and G. C. Anupama (IIA), also discovered ultraviolet emission from 42 novae, a special class of stellar explosions, and even caught four of them in the act of outburst itself.

The department said that this could help scientists study these interacting binary star systems in our nearest neighbor galaxy at different phases of their life, some piling up matter from their companion, while others spewing it into space.

“UVIT’s fine spatial resolution and unique capability to observe simultaneously in far UV and near UV helped us investigate the fluxes in different UV bands, which led to the detection of accretion disks in some of these systems, 2.5 million light years away. The brighter the disk, the more rapidly it is consuming its companion’s matter. We also studied how the flux from these discs changes with time, and as per our expectations, the accretion process was found to be stable in these systems.” Mr. Basu, a PhD student at IIA, who led the project, said.

Dipankar Banerjee
| Photo Credit: Special arrangement

Astrophysicist Dipankar Banerjee took charge as Director, Indian Institute of Space Science and Technology (IIST), on Monday.

Professor Banerjee, a senior professor at the Indian Institute of Astrophysics, Bengaluru, was serving as Director, Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, prior to the current assignment. He has headed ARIES, a facility under the Department of Science and Technology, since December 2019. It is after a gap of three years that the IIST, at Valiamala here, is getting a full-time director.

Professor Banerjee has taken over the charge of IIST from S. Unnikrishnan Nair, Director, Vikram Sarabhai Space Centre, who had been holding additional charge of IIST since September 2022. IIST was established in 2007 as a deemed to be university under the Department of Space for moulding space scientists for the Indian space programme.

New Delhi:

In a first, scientists at the Indian Institute of Astrophysics (IIA), an autonomous institute of the Department of Science and Technology (DST), have discovered interaction between a radio jet from a dwarf galaxy and interstellar gas causing shock waves.

The team found that the radio jet emitted from the Active Galactic Nuclei (AGN) — a black hole — from the centre of the galaxy NGC 4395. AGN is known to emit bright jets and winds and shape their galaxies.

The bright jet interacted with the surrounding interstellar medium at a small spatial scale of about or about 30 light years. The dwarf galaxy is situated at a distance of about 14 million light years.

In the study, published in a paper in the Astrophysical Journal, the team combined data from radio to X-ray wavebands from the galaxy NGC 4395 to find the interaction around the black hole.

“We decided to investigate how the radio jet from a small black hole interacts with the gas in a dwarf galaxy called NGC 4395,” said lead author Payel Nandi, and doctoral student at IIA.

The team used data from the UltraViolet Imaging Telescope (UVIT) on board AstroSat — India’s first dedicated space observatory — launched by ISRO in 2015, as well as Chandra for X-ray data Gemini-North and Hubble Space Telescope for optical data.

The findings showed a unique radio structure resembling a bipolar jet, whose core was centred at the black hole location.

“This jet is relatively weak, but our multi-wavelength analysis of this 30-light-year region showed that the jet is interacting with the surrounding gas, and possibly causing shock waves to propagate through it,” said Prof. C. S. Stalin at IIA, a co-author of the study.

The light emitted by the ionised oxygen in the optical band, molecular hydrogen in the infrared region, and the X-ray emission, closely match the path of the radio jet.

Nandi noted that the study found “strong evidence for an outflow of material carried by jet into the surrounding medium”.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

Vampire stars, known as blue straggler stars (BSS), defy simple models of stellar evolution and show many characteristics of younger stars. Photo: PIB

Team of astronomers from the Indian Institute of Astrophysics (IIA) have made the discovery that a vampire star has been rejuvenating its youth by sucking up material from a companion in the star cluster M67 located in the constellation Cancer.

Vampire stars, known as blue straggler stars (BSS), defy simple models of stellar evolution and show many characteristics of younger stars.

“This anomalous youth is explained theoretically as due to rejuvenation by eating up material from a binary stellar companion. Star clusters are useful test-beds to test this theory as they host a large number of binary stars, some of which can lead to the formation of vampire stars. Once rejuvenated, these stars follow a different path of evolution when compared to Sun-like single stars. So far, detection of sucked up material along with the sighting of their remnant binary companion was elusive,” said the department of science and technology.

However, recently, a team of astronomers from IIA made a groundbreaking discovery of a vampire star in M67, that sheds light on a complex rejuvenation process, known as mass-transfer in a binary system.

The key to this detection was data from the UltraViolet Imaging Telescope, on board AstroSat, India’s first dedicated space observatory.

The scientists studied the surface composition of the vampire star in M67, called WOCS 9005, using spectroscopy, a technique where the light of the star is dispersed into its colors like the rainbow.

“This star is expected to show chemistry very similar to our Sun, but we found that its atmosphere is rich in heavy elements such as barium, yttrium, and lanthanum”, said Harshit Pal, the lead author of the paper.

“The presence of heavy elements in the spectrum pointed to a polluted atmosphere of the vampire star and the source of pollution being an external source. The external source is likely to be its binary companion, which must have made the heavy elements when it passed through its AGB phase, and later became a white dwarf star”, said Prof. Annapurni Subramaniam, co-author of the paper and Director IIA.

Prof. Subramaniam added that the blue straggler star that we see now must have eaten up most of this barium-rich material due to its gravitational pull, and is now presenting itself as a rejuvenated star.

While moving in its orbit roughly once a month, the moon will occasionally occult, or hide, bright stars that are behind, and sometimes, even planets. 
| Photo Credit: AP

The Bengaluru-based Indian Institute of Astrophysics (IIA) has filmed the passing of the moon in front of Antares, a bright red star.

The moon passed in front of Antares on April 27, hiding it for roughly 40 minutes. IIA said that this event was visible only from southern India. IIA filmed the event from its Bengaluru campus using a camera on an 8-inch telescope.

While moving in its orbit roughly once a month, the moon will occasionally occult, or hide, bright stars that are behind, and sometimes, even planets. This happens now and then for the star Antares (Jyeshtha), which is the brightest star in the constellation of Scorpius. Since the moon is relatively close to the Earth, such occultations will be visible only from some locations on the globe, similar to why a solar eclipse is seen only from a particular part of the globe.

The last such occultation of Antares, which was visible from India, was on February 5 this year. The next one will be in June 2027. However, the occultation of the planet Saturn by the moon can be seen from India on July 24, and again on October 14 in 2024.

As seen from Bengaluru, Antares disappeared behind the bright side of the gibbous moon around 1.13 a.m. and reappeared at the darker side around 1.53 a.m. IIA has a video of the disappearance and reappearance. In the videos, the telescope is tracking Antares, and the relative motion of the moon is also clearly visible. The shaking of the image is due to winds buffeting the telescope, and the shimmering of the image is due to the Earth’s atmosphere.

You spoke at this recent lecture at IISc about how science fiction often draws people towards science. Was that something that happened to you?

I read a lot of different things, including historical novels, Agatha Christie and P.G. Wodehouse. Science fiction was one of the things I read. Did it push me into science? I certainly found it exciting, but I can’t say that it was specifically what pushed me.

In 1981, the Space Telescope went to Johns Hopkins University, where you completed an undergraduate and postgraduate degree in physics. Did that influence your decision to continue studying there for your PhD?

What you do with your PhD is really about what you are interested in at that time and the opportunities in the college. This was just about the time when Hopkins got the Space Telescope, and it seemed like a good opportunity. The reality is that the people involved are busy with their own work, and there was not as much interaction between the Physics Department and the Space Telescope as might have been.  

After receiving your PhD in 1987, you went on to work at Goddard Space Flight Centre. Then you returned to Hopkins, where you spent the next decade or so as a research scientist before moving to India in 2000, where you joined IAA. Can you talk about what prompted the move? 

There were a couple of reasons. One was because AstroSat (an ISRO astronomy mission) was trying to take off, again from the ground floor of a major observatory, and it seemed like a good opportunity. As it turned out, AstroSat took a lot longer than one would have anticipated. It was launched in 2015, but discussions had started in the 1980s, and we started working on it in 2000-2001. That was too much time for me to spend on any mission, and I did less with it than I could have done.  

Also, the U.S. market is pretty saturated. While you do get to do good work, you’re not making much of a contribution; you are making an incremental contribution. In India, the community is much smaller, so you have more of an impact.  That certainly has happened. Over the last twenty years, I have probably talked to at least 10,000 students. I have been teaching a fair bit, so you have this impact.

You do a considerable amount of science outreach, constantly talking to lay people. What, in your view, is the importance of science outreach?

One reason is that it is our mandate; our salaries come from the public exchequer. It is also in self-interest because science accounts for 0.7% of the GDP, whereas in China, it accounts for 2.5%. It is abysmally underfunded, as you can tell from the output. If you go out there and show that science is interesting—hopefully we do that—it will eventually feed back into politics. 

Also, people don’t understand how integral science is to their daily lives. They don’t have an appreciation for how much their lives depend on science, whether it is the technology used in cell phones or computers or medicine; you can’t survive without basic science. Our world is built on basic science, and part of basic science is rationality. We must teach people to think. Clearly, we have not done a very good job. 

What are the biggest challenges you face with doing science outreach in India, where science and rationality must often battle with the country’s collective culture, including its values and traditions?

It is very hard. We do have a lot of dedicated people trying to do it, including the Science Society that I am part of. 

But faith is so built-in in our society. I tell the students that they should go ahead and do whatever religious stuff, but at least understand why you are doing it. Don’t just do it because your parents tell you to do it, understand the basis behind it. 

 What, in your opinion, is the biggest change that India needs to make when it comes to enhancing its scientific contribution? 

If you look at the places that are advanced, they all have robust academic establishments. Silicon Valley came up where it did because of Stanford (University) and Berkley (University of California, Berkeley). Or look at how they how they pumped the health system around Hopkins. In Bangalore, it is because of IISc and because of all the engineering colleges that developed here in the 1980s. You can say what you like about engineering colleges—and the money-making stuff—but it has given Bangalore a strong technical base and made it the science capital of the country.

When you fund academics, you are investing in your future. You will have returns that far exceed what you put in. There was a study in Australia many years ago and they said that for every dollar you put in, you get five dollars out. 

Money is one part of it, but it also requires a revamping of the educational system. The new education policy is not going to do anything. It is drawn up by a bunch of people in elite places without knowledge of ground conditions.  

You can’t just pile money into the university system that we have now, this bureaucratic system that doesn’t measure outcomes. All the students want to do is have fun in college and get out and get a job afterwards. Their parents, too, want them to get a job and money. The administration wants to sell itself, while teachers know that it’s in their best interests to give students good grades. No one cares about education in the middle. It is just a transaction. 

What do you think of India’s current space programme? 

I think the space programme has done very well. There are many places where we can do better. For instance, the Chinese space programme used to be well behind us, but now, in 20 years, it is far ahead. 

But the current revamp is good for ISRO. It was always supposed to be the Indian Space Research Organization, but they ended up getting into routine things. How is your 100th PSLV ( Polar Satellite Launch Vehicle) going to be different from your 99th?  

It is good that they are getting into private industry, but the main problem, I see, with the revamp is that the government has still not realised that space is still driven by government money. They are expecting private investors to come in, and that is not realistic. They have projected a lot of money being put into the system, but I think it may be difficult. We shall see.   

A long-exposure photograph of stars over the Hanle Dark Sky Reserve in Ladakh.
| Photo Credit: Akash Anandh

The temperatures were subzero and freezing. The conditions were unforgiving. We were elated and thrilled being outdoors all night.

At 4,300 metres above sea level, we felt it could have been the Everest Base Camp. In reality, we were at Hanle, in the Union Territory of Ladakh. The air is so thin at such altitudes that the oxygen level is less than 60% of what one is normally used to at sea level. Before getting here, we had to acclimatise ourselves for 48 hours at Leh, at an altitude of 3,500 m, before climbing up to Hanle.

It is definitely not for everyone. But it was certainly for us: we were a group of amateur astronomers invited by the Indian Institute of Astrophysics (IIA) to attend the HDSR Star Party 2023, organised and conducted by IIA.

The Hanle Dark Sky Reserve (HDSR) is India’s first dark sky region, and is centred at Hanle in Eastern Ladakh, around the Indian Astronomical Observatory. HDSR preserves the dark skies by reducing light pollution in the surrounding areas, and uses these dark skies to promote astrotourism as a means to further enhance socio-economic development in the area.

Seeing into dark skies

A dark sky is the night sky as nature meant for it to be: without any light pollution. Light from the human-made objects that we use – especially outdoor lighting sources – blocks our view of the stars and most celestial objects in the night sky.

Ironically, a dark sky lets you see better. From within a light-polluted city, we can typically see only a handful of stars. But from a dark site, we can see thousands in the same location of the sky.

Apart from stars, the Milky Way’s galactic centre and its arms are clearly visible to the naked eye. We can also see several star clusters, nebulae, galaxies such as the Andromeda and the Triangulum.

Zodiacal light – a faint glow of diffuse sunlight scattered by interplanetary dust in the Solar System; airglow – an optical phenomenon caused by faint emission of light in the earth’s atmosphere; and gegenschein – a bright spot in the night sky centred at the antisolar point, caused due to backscatter of sunlight by interplanetary dust – are also visible.

Venus can be so bright in the night sky that its light can cast shadows on the ground, just as moonlight does.

A start to something big

Although some of us astrophotographers were aware of the theories of these optical phenomena and the fact that we could see so many stars and celestial objects under the darkest of skies, it was still an overwhelming feeling to actually observe and experience them under the Bortle Class 1 skies of Hanle.

The Bortle Scale helps amateur astronomers measure the night sky’s brightness at a given location. The scale ranges from Class 1, the darkest skies available over the earth, through to Class 9, which denotes the pale, light-marred skies over the insides of cities.

A sense of thrill as well as caution filled the thin air under the dark skies of Hanle. Observing outdoors in these harsh conditions – with or without equipment – meant one had to be both strong-willed and careful. But it was worth every second as caution soon led to exhilaration and then wonder.

For us amateur astronomers, the three nights and days of the HDSR Star Party made for a great opportunity to observe under pristine night skies. We could also connect with fellow amateur astronomers who had come from various parts of the country: they were experienced amateurs as well as young ones with starlit eyes.

We also got to rub shoulders with professional astronomers, exchanging ideas and information on all things astronomy, including the particulars of visual observation and the techniques of astrophotography, as well as share large telescopes and imaging equipment during the event. In all, it was an unforgettable experience.

Being the first ever dark sky reserve in the country, HDSR is certainly a source of pride for India and will be a blueprint for other dark sites in other regions. And just like at Hanle, upcoming dark sky reserves can also promote astrotourism, which will help both amateur astronomers like us as well as local communities.

The Star Party is also highly likely to evolve into an annual event, and I am glad that I was part of the successful first edition of the HDSR Star Party this year. It was expertly and thoughtfully planned and conducted by Dorje Angchuk, who is the engineer-in-charge at the Indian Astronomical Observatory in Hanle, and Niruj Mohan Ramanujam, head of the IIA SCOPE Section.

I believe the event was a great start to something big for casual stargazers, passionate amateur astronomers, and our space-loving country as a whole.

(Akash Anandh is an amateur astronomer, astrophotographer, writer, and science communicator)

akash.anandh@gmail.com