'Moth to a flame': Pakistan names a sun-like star and its exoplanet

180 light-years away from us, an exoplanet called 'Perwana', orbits around 'Shama', its star.
Published January 18, 2020

There is a planet orbiting a star about 180 light-years from Earth. We don’t know if there are any beings that populate this planet. But the inhabitants of Earth now officially recognise this planet as 'Perwana', and its parent star with the moth’s eternal love of the flame, 'Shama'.

Shama, an Urdu word which means a candle or a lamp that burns is often used with Perwana, a butterfly or a moth. Together, they signify 'a moth to a flame': to be irresistibly and dangerously attracted to something or someone.

Perwana’s eternal love for the flame is a beautiful and well-known motif in Urdu literature. Poets believe that true lovers are like these moths who die in the flame of a beloved's love. Allama Iqbal famously emphasised the humility of the little insect in the face of the light in Shama aur Perwana:

Perwana aur zauq-i-tamashae roshnee
Keera zara sa for tamannae roshnee

The moth and the taste for the sight of light
This small insect and its longing for light

This motif of shama and perwana are now resonated in deep space as well.

Naming celestial bodies

The names of astronomical objects are officially recognised only by the International Astronomical Union (IAU). So if you have bought a star name from a company, you have been scammed.

IAU was formed in 1919 and to celebrate its 100 years, it provided an opportunity for countries around the world to name exoplanets and their stars. For example, Iran named its star and its exoplanet, Kaveh and Kavian, respectively, after the story of one of the heroes of Ferdowsi’s 10th-century epic, Shahnameh.

Sri Lanka named its star 'Sāmaya', meaning peace in the Sinhalese language, and its planet, 'Samagiya', signifying unity.

Pakistan’s names are 'Shama' for the star and 'Perwana' for its planet.

Discovering Shama and Perwana

With a growing interest in astronomy, we have seen the cropping up of astronomy societies in all major Pakistani cities and they regularly provide opportunities for stargazing to those who have not looked at the night sky with a telescope.

Read more: Magic of science

In the case of Shama and Perwana, a national committee that included representatives of the Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) as well as several astronomers solicited names from the general public and got 60 excellent proposals (I was also part of the committee). The final names of Shama for the star and Perwana for its planet were suggested by Ahmed Noor-e-Alam and Wajeeha Shakeel.

International Astronomical Union recognised “Shama” and Perwana” as new names for the star HD99109 and its planet HD99109b. — Courtesy: *nameexoworlds.iau.org/pakistan*
International Astronomical Union recognised “Shama” and Perwana” as new names for the star HD99109 and its planet HD99109b. — Courtesy: nameexoworlds.iau.org/pakistan

Before the intervention of Urdu poetry, the star was only known through its dry catalogue name, HD99109b. The little ‘b’ denoted that it is a planet around the star HD99109. The parent star, now known as Shama, is slightly smaller than our Sun and so far, we know of only one planet orbiting around it.

It is located in the direction of the constellation, Leo, but is too faint to be seen with the naked eye.

Shama is over 10 billion years old and is expected to live at least for another 10 billion years. By comparison, our Sun will run out its fuel in 5 billion years.

Perwana, on the other hand, is not like the Earth. It is 160 times more massive than our home planet (or about half the mass of Jupiter) and is likely to be made mostly of gases. It takes 493 days for it to go around its star once (compared to the 365 days for Earth).

While it is unlikely that it hosts any life. However, if it has any moons, then they might be a indicator for the possibility of life.

At the end of Shama’s life, it will be left as a dense core, roughly the size of the Earth, known as a white dwarf.

Unlike the perwana of Urdu literature, the planet Perwana will not burn into Shama, nor will it abandon it. Instead, it will keep on circling its star forever — long after the flame is gone.

Finding planets in the 'wobble of a star'

Astronomers have come up with creative methods to find exoplanets. Some have been found by direct imaging. But most of the planets have been found using one of two methods.

When a planet passes in front of its star, we see a dip in the brightness of the star (an eclipse). We call this the 'eclipsing method'. The bigger the planet, the bigger the dip, and the regularity of the dips would give us an estimate of the planet’s orbit.

For example, a planet with an orbit like the Earth would pass in front of its star every 365 days. This method was most successfully used by the Kepler Space Telescope to find several thousand exoplanets.

However, most of the earliest planets were found by looking at the wobble of a star due to the existence of a planet.

This movement is because the star and the planet (or planets) orbit around a ‘centre of mass’. In our own solar system, most of the mass is in the Sun. The centre of mass, in this case, is still inside the Sun, though not at the centre. This causes a relatively small movement of the Sun around this point.

Pakistan’s exoplanet, Perwana, was discovered using the wobble method. — Courtesy: Kainaat Astronomy in Urdu YouTube channel

Of course, planets move a lot more (hence our birthdays are every 365 days due to Earth’s motion around this ‘centre of mass’). For far-away stars, astronomers cannot see the planets directly but can infer their presence by detecting this small movement of the star.

Looking for a firefly in the floodlight

Perwana is only one of over 4,000 exoplanets detected so far. Astronomers estimate that there are hundreds of billions of planets just in our own galaxy alone, and countless more in the universe. And yet, it has been less than 25 years since the discovery of the first exoplanet around a sun-like star.

You can reasonably ask, what took so long to start discovering planets around other stars?

There are two main reasons for this: First, planets are faint as they mostly reflect the light of their parent star. This makes it difficult to see them even around some of the closest stars.

Secondly, the stars they orbit are much brighter and these planets get lost in the glow. It is like trying to find a jugnoo (a firefly) right next to a floodlight.

But in the meantime, look up at the sky and imagine Perwana orbiting its star, Shama, 180 light-years away from us.

If it has inhabitants, they don’t know that their world has been given a name in a language spoken by humans on a small portion of the Earth called Pakistan.

The writer is an Associate Professor of Integrated Science & Humanities at Hampshire College, USA. He is also an astronomer affiliated with the Five College Astronomy Department (FCAD) in Massachusetts and host shows on YouTube channel, Kainaat Astronomy in Urdu.