Czech ‘ESO photo ambassador’ Petr Horálek, asteroid 6822, and the Long Tails of Comet NEOWISE

Milky Way, photo: Petr Horálek

Petr Horálek travels the globe to observe and photograph solar and lunar eclipses, and delivers lectures in schools across the Czech Republic to encourage young people to cast their eyes towards the heavens. A few years ago, he became a Photo Ambassador for the European Southern Observatory, and even has an asteroid named for him (“6822 Horálek”). I spoke to him about his life’s work, shortly after NASA named his breath-taking picture of the comet NEOWISE – now closer than ever to the Earth – as “Astronomy Picture of the Day”.

I began by asking Petr Horálek, an astronomer by education, how he first got into star-gazing.

“It all started when I was very young, in 1997, when I was at my grandparents at their cottage. My grandmother wanted to show me the Big Dipper in the sky. At that time, it wasn’t all that interesting to me at first. But then she showed me its shape on paper, and I got interested and went outside again. More than the shape, it was interesting to me that the Big Dipper was in a different place in the sky because of the rotation of the Earth. And that was the impulse that got me so fascinated by astronomy.”

Petr Horálek, photo: ESO / P. Horálek, CC BY 4.0

You went on to study theoretical physics and astrophysics in Brno. In layperson’s terms, what did you focus on there? What was your thesis on?

“I wanted to learn every about astronomy, and when I got to university, the most interesting thing to me was the total solar eclipses because they are very interesting not only from the scientific perspective but also for everyone who sees one. They always get people so excited and fascinated – you want to see it again and again.

And after graduating, you joined the Astronomical Institute at the Academy of Sciences at Ondřejov. Was that also your focus there, solar eclipses, especially? Or was it a different kind of work?

“When I graduated from Masaryk University, I started to work on observing fireballs [bolides] in the sky. I was part of a big team monitoring fire balls. But in my personal interests, I started to focus more on photography. So, professionally I was focused more on interplanetary matter, but I wanted to know more about solar eclipses and the solar atmosphere, which made me even more fascinated with the eclipses.”

I understand that 2014 was a key year for you – that [after working for some time at the Úpice observatory] you went to New Zealand to work in the fruit orchards and photograph the night sky of the southern hemisphere. What constellations or phenomena did you have a chance to observe there, and later, in the Cook Islands, the Canary Islands, and South Africa?

“In 2014, I stopped doing any professional astronomy and went to the New Zealand orchards to just enjoy the dark skies of the southern hemisphere. I was really fascinated and motivated when I saw the whole of the constellation Scorpius, which is probably the most beautiful constellation in the sky also because it is close to the centre of the Milky Way.

“Unlike in our part of Europe, there you can see the centre of the Milky Way just above the horizon. The centre reaches the zenith and you have it just above your head. And it’s so bright, especially in such a dark sky, that if you have a good camera, even an average camera, you can capture your own shadow, cast by the Milky Way – which is completely crazy.”

Zodiacal arc over La Silla, photo: Petr Horálek

In 2015, you went to the Atacama Desert at the European Southern Observatory’s (ESO) La Silla and Paranal Observatory, and began working to popularize astronomy, in part by giving lectures in schools. How did that come about, and could you give me an idea of what a typical lecture might be, how you try to get students interested in the field?

“I was always somehow more interested in the popularization of astronomy that the professional astrophysics and astronomy. So, I always tried to be part of some group which focuses on showing the night skies to people.

“When I became a Photo Ambassador for the European Southern Observatory, which brought be to Chile and the Atacama Desert, I was able to make some good photographs and use them to show people what is so amazing in the sky, and why we should fight against light pollution. A part of what I do in popularizing astronomy is always about the fight against light pollution.”

So, making people more aware of light pollution is a big part of getting them to look up into the night sky. And you are especially interested in solar and lunar eclipses, and travel the world to observe and photograph them – and published a collection of them in the book Mysterious Eclipses (2015). What are some of your most memorable trips, and the most amazing eclipses that you have viewed?

“Each one is very unique, and of course every experience completely different, so I can’t share them all. But I can share one or two, maybe.

Namibian Geminid night, photo: Petr Horálek

“One was the second solar eclipse I saw, which was in Turkey and one of the longest I have seen. It was unforgettable because we were in a small village by the Mediterranean, and we could clearly see such a beautiful corona, which was huge – it can seem to be five times larger than the Sun in the sky. Also because of the emotions, of course. Thousands and thousands of people were on the beach, and the emotions around were very clear. And you are a part of that. So, that was more about the emotions than what was in the sky.

“Another beautiful moment came about a year ago, when I was an ESO Photo Ambassador and saw a total solar eclipse at the La Silla observatory. It was very unique because the next one will occur in 2231. And because you are in the Atacama Desert and at a very high altitude, about 2,400 metres above sea level, you could see such a beautiful, clear solar eclipse with such colours in the sky – because the eclipse was very low over the horizon. You could see a U shape of a lunar shadow in the sky moving your direction, the colours of the illumination of the sky against the backdrop of the desert. It was one of the most magical experiences.”

I also wanted to ask you about the asteroid 6822 Horálek [which has an orbital period of 1,522 days], named after you. It was discovered on October 28, 1986 – in the year of your birth, and on Czechoslovak National Independence day. What’s the story behind that asteroid?

Long Tails of Comet NEOWISE, photo: Petr Horálek

“Well, astronomers cannot name an asteroid after themselves. The only object that you can name after yourself is a comet. So, if an astronomer discovers an asteroid, they can only recommend after whom it should be named.

“I was very fortunate because at some point some astronomers noticed that I am very active in the popularization of astronomy, showing the beauty of the night sky through my pictures and so on, and wanted to give me this kind of ‘award’, let’s say. “

“It had been discovered by Zdeňka Vávrová at the Kleť Observatory, but not yet named after anybody. They suggested my name and the International Astronomical Union gave its okay to name it after Petr Horálek. So, that’s the story of the asteroid.”

It’s quite an honour! And just this week, one of your photos was chosen by NASA as the Astronomy Picture of the Day, of the comet [C/2020 F3] known as “Comet NEOWISE”. I understand it is the closest to Earth now, as we speak, from July 22-23 – some 103 million kilometres away, and appears right below the Big Dipper constellation. What can you tell me about that photo, and where you recommend trying to view the comet in the Czech Republic?

“The sky at the moment is really so interesting because you can see the comet very close to the Big Dipper. My friends and I went to try to find some place with a good view to see it. And the weather was not always favourable, so we went to the Eagle Mountains [Orlické hory] and found a place, coincidently with a beautiful view of the bluffs of Suchý vrch, and the comet was just above the summit.

“So, I took many exposures, and after some post-processing, I was just amazed at the tail of the comet – the ion tail of the comet is so huge it’s actually out of the field of view. Actually, even the editors of the Astronomy Picture of the Day were amazed by this, so they published it.

“As for the comet itself, it’s really an amazing one. It’s probably the most beautiful in 22 years, at least in the northern hemisphere. At this moment, it’s getting its closest to the Earth, which occurs on July 23, but it’s getting dimmer because it’s farther from the Sun, the sunlight is not so close. But photographically, it is huge, and it’s ion tail is long as the width of the Big Dipper in the sky.

“For a photographer, it’s an amazing object, but also for the public, who can just travel away from the cities and see it very easily with the naked eye or a small telescope until the end of this week, and then the Moon starts to shine too bright. So now are the best conditions.”

Lastly, what phenomena – or “pearls of astronomy”, as you have called them, are highest on your wish list to photograph some day?

“Well, I have a list of the most unique and most amazing phenomena, and the comet was actually one of them, and finally I have it. The last thing I haven’t seen in my life – and it’s actually very rare, and I don’t know if I will have a chance at all – is a galactic supernova [a powerful stellar explosion, which can create a black hole].

“It’s something that occurs, statistically, once every 200 years. The last one occurred at the beginning of the 17th century [Kepler's Supernova in 1604]. So, statistically, it could occur any day. It could make a star shine even brighter than a full moon for weeks. So, hopefully all the world, not just me, soon will have a chance to see this very rare event in the sky.”

Petr Horálek’s photograph, entitled The Long Tails of Comet NEOWISE, which captures the sky above Suchý vrch in the Orlické region, was taken on the night of July 13-14, when the Sun was almost directly below the comet, deep it the horizon. Thanks to this, the bluish, so-called ion tail of the comet appears to point almost vertically upwards, and it is possible to recognize some nodes, caused by the reaction of ionised gas to the solar wind. The Suchý vrch horizon is highlighted by light pollution from Klodzko, Poland.