Dr Kirsten Banks

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Dr Kirsten Banks AstroKirsten | Astrophysicist | Science Communicator Welcome to the official page of Kirsten Banks, also known as AstroKirsten!
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Kirsten is an astrophysicist and science communicator who is passionate about making science accessible and engaging for everyone. Through her fun and informative videos, Kirsten shares her love for space and science with the world. She covers a wide range of topics, from the latest space news to the basics of astronomy, and everything in between. Her approachable and relatable style makes learnin

g about science a fun and enjoyable experience for people of all ages. Kirsten's dedication to science communication has earned her a large following on social media, where she has become a well-known personality in the science community. Her positive and uplifting content inspires and educates people around the world, while her infectious enthusiasm encourages everyone to pursue their interests in science and space. This page is the go-to place for all things AstroKirsten. Follow along for updates on her latest videos, appearances, and projects, as well as behind-the-scenes looks at the life of a science communicator. Join the community and connect with others who share a love for space and science. Let's explore the wonders of the universe together with AstroKirsten!

21/12/2025

What is heat, really? 🌡️

We usually think of heat as just “warmth” — like when it’s cold and someone says “turn up the heat.” But in physics, heat has a very specific meaning. Heat is the transfer of energy that causes a temperature change.

And that energy can move in three different ways:
🔥 Conduction
When a hot object touches a cooler one, energy flows through direct contact — from hot to cold.

🌬️ Convection
This happens in liquids and gases. Warmer material rises, cooler material sinks, and the fluid starts swirling — like water heating up in a kettle.

☀️ Radiation
This one’s wild because it doesn’t need matter at all. Heat can travel as electromagnetic radiation, meaning it can cross empty space. That’s how energy from the Sun reaches Earth.

And judging by today’s weather… that radiation is working.

I put the washing out an hour ago and it’s already bone dry 😅

Good morning and happy December Solstice! 🌏☀Today is the day when the Sun is at its southernmost point over Earth, and a...
21/12/2025

Good morning and happy December Solstice! 🌏☀

Today is the day when the Sun is at its southernmost point over Earth, and at precisely 2:03 AM (AEDT), the Sun was directly overhead the Tropic of Capricorn.

Here's what the December Solstice means for our world:
🌏 Today marks the changing of the astronomical seasons (Summer in the Southern Hemisphere and Winter in the Northern Hemisphere)
🌏 Today is the longest day in the Southern Hemisphere and the shortest day in the Northern Hemisphere

Here's a fun little exercise for those who wish to partake:
At solar noon today (the moment when the Sun is directly north of me), the Sun will be at an altitude of 79° above the horizon. At what latitude will I be on Earth today?

17/12/2025

How much does a cloud actually weigh? ☁️⚖️

Spoiler: a LOT more than you’d expect.

Clouds float, so it’s easy to assume they’re light — but floating doesn’t mean weightless. Boats float too, and they’re very much not light. Anything made of stuff has mass.

Clouds are made of tiny water droplets and sometimes ice crystals suspended in air. A typical cloud has a density of about 1.003 kg per cubic metre. For comparison, dry air at sea level has a density of about 1.2 kg per cubic metre — which is why clouds can float even though they’re heavy.

So the real question becomes: how big is the cloud?

Take a small, fluffy cumulus cloud about 1 km wide, 1 km tall, and 1 km deep. That’s a cubic kilometre of cloud — and it would weigh roughly 1 billion kilograms.

Now scale that up to a massive cumulonimbus storm cloud, which can be 5–10 km wide and up to 20 km tall. That absolute unit of a cloud can weigh around 1 trillion kilograms.

Clouds: heavy… but floaty.

Nature is wild.

15/12/2025

There are red stars, blue stars, orange stars, yellow stars… so why aren’t there green stars? 🌈⭐️

The short answer: stars don’t emit just one colour of light — they emit lots of colours at once. Which colours dominate depends on the star’s temperature.

Cool stars emit much more red light than blue, so when all their colours mix together, they look reddish. Hotter stars emit more blue light, so their combined glow looks blue-ish.

But what about stars that emit most of their light in the green part of the spectrum?

That’s actually stars like our Sun. The Sun peaks in green light — but it also emits plenty of red, orange, yellow, blue, and violet. When you mix all those colours together, you don’t get green… you get white.

10/12/2025

Mountain Trivia for International Mountain Day: Do you know your Solar System mountains? Let's test your knowledge!

09/12/2025

with What even is a black hole anyway?

Hi Joe and Frankie, I'm Dr Kirsten Banks! I'm an astrophysicist, and I work at a place that researches black holes. I've got you on this one!

08/12/2025

The results are in! Let's see how you went!

The other week, we explored how common all of the different types of stars are, and I left you with a question: Why do you think the smaller M-dwarf stars are more common than the big, bright and hot O- and B-type stars?

Thank you to everyone who gave it a go, whether you were correct or not quite there, I'm proud of you!

NEW HARDWARE ALERT!It is such an honour to be the winner of the New Social Media Talent Award for Swinburne University o...
03/12/2025

NEW HARDWARE ALERT!

It is such an honour to be the winner of the New Social Media Talent Award for Swinburne University of Technology's Media and External Communications Recognition Awards of 2025.

I’ve been doing science communication professionally for over a decade now (wow, time really does fly) and producing educational video content on social media for 6 years. And while it has never been about the recognition, I couldn’t help but let out a tiny “WHEE!” when my name was called as the winner of this award.

It’s great to be at a university that really values sharing with the wider community. No ivory tower, just a space that’s proud of what they do, their experts, and welcomes people into their space.

Thank you so much to the Swinburne Media Team for this great honour. I can’t wait to see what we can do in 2026!

02/12/2025

How do we know how much the Sun weighs — and who figured it out first? 🌞⚖️

Believe it or not, the credit goes to Isaac Newton himself. Yep — that Newton: the apple-falling, F = ma guy.

You can’t exactly put the Sun on a cosmic scale, but you can measure how strongly it pulls on things. That pull is gravity — and Newton realised that if you know how fast a planet moves around the Sun and how far away it is, you can work backwards and calculate the Sun’s mass.

He used Venus as his starting point because its orbit was well observed in the 1600s. Then he compared the Sun’s “gravitational pull strength” to the pulls of Jupiter and Saturn, using their moons as reference points. Basically, he built the first-ever solar system weight chart!

And honestly? His numbers were wildly good for someone doing this with quill-and-ink maths.

He estimated the Sun was 170,000 times heavier than Earth (the real value is 333,000 times heavier), but he got Jupiter’s mass almost spot-on — within a few per cent of modern measurements!

Why was he so accurate with Jupiter but not with Earth? Two big reasons:
1️⃣ His distance from Earth to the Sun was off by about 20%.
2️⃣ Newton accidentally introduced a copying error that repeated through later editions of his Principia.

Maths in the 1600s was a whole adventure.

01/12/2025

Have you ever wondered why Aussie summers feel so much hotter than European summers? 👀

Spoiler: it’s not the ozone layer… and it’s not just because we’re 5 million km closer to the Sun.

When I first saw that claim, I was sceptical. Yes — the Earth is closest to the Sun during the Southern Hemisphere summer. But does that actually explain why the Australian sun feels like it’s personally attacking you? I didn’t think so… so I dug in.

Turns out, a whole bunch of factors stack together to make Australian summers feel brutal:
🌡️ The subtropical ridge
Australia sits under a belt of high-pressure systems that suppress cold fronts. Cold fronts normally bring rain, cooler temps, and wind — but in summer, they’re weaker. Less cooling, more heating.

🏜️ Australia’s desert interior
Our continent is mostly dry land that heats up fast and stays hot. That heat radiates outward and amplifies temperatures across the country.

🌬️ Few major mountain ranges
With minimal topography to block or redirect air masses, hot air just flows freely across the continent. Europe has the Alps. We… have the occasional hill.

🌞 High UV levels
Australia has some of the highest UV in the world. Yes, part of that is related to the ozone hole — but also because we have clearer skies, cleaner air, more direct sunlight, and generally sunnier summers.

And technically, yes, we are a little closer to the Sun — but that’s the least important factor here.

And here’s a fun twist: the Earth’s global average temperature is actually 2.3°C hotter when we’re farthest from the Sun, during the Northern Hemisphere summer!

So no — being closer to the Sun isn’t the reason Aussie summers feel so intense.

It’s a mix of geography, atmosphere, and climate coming together… into one giant sweat-fest. 🥵🇦🇺

27/11/2025

Yeah... the UV index next to the Sun is SO MUCH WORSE than 300...

It's more like 30 million... Ouch!

Thank you to everyone who contributed to the discussion. This is the sort of critical thinking and care for each other's learning journey that I strive to foster on this page, and I'm so glad that you've treated me with that same care. I love this community so much, you guys are the best!

25/11/2025

What's the maximum UV from the Sun?

I'm not convinced I'm right, but I'm confident enough in the steps I took to get there to put this out to the internet, so that's got to count for something, right?!

If you don't care for the maths, the answer I came to was a UV index of 300! Ouch!

Thanks to mikitothefuture on TikTok for the great challenge!

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