Daily Bulletin


Daily Bulletin

News

  • Written by Belinda Nicholson, Lecturer, University of Southern Queensland

Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

Why is the Sun orange when white stars are hottest? – Rain, age 6, Toowoomba.

Hi Rain. Thanks for sending in your excellent question.

The reason the Sun shines so bright is that it’s hot. And the colour it glows depends on how hot it is.

You are right that a star that glows white is hotter than one that glows orange.

And it’s true the Sun often looks orange. But it isn’t really orange. It is white. Well, it’s a bit on the yellow side but it’s mostly white.

But even white stars aren’t the hottest.

Read more: Curious Kids: What existed before the Big Bang? Did something have to be there to go boom?

The blue giants that burn bright and briefly

The very hottest stars actually glow blue. We call them blue giant stars.

These blue giants are around 80 times larger than our Sun – so they are really, really big. They live and die very quickly. They are so hot and so big they burn through their fuel very quickly and last just a few million years.

That might sound like a long time but it’s not much compared to how long our Sun will live.

When our Sun was a million years old, it was still just a child. It’s about 5 billion years old now and will live to about 10 billion years. So you could say the Sun is now middle-aged. It’s about halfway through its life.

So blue giants are hottest, white stars are very hot, but there are also orange stars that burn less hot. There are even red stars, which are a bit cooler again. They are a half or even a quarter the size of our Sun and while they are still burning hot, they are nowhere near as hot as our lovely Sun.

Curious Kids: why is the Sun orange when white stars are the hottest? The hottest stars are actually blue. Shutterstock

So why does the Sun look orange, then?

A lot of the pictures we take of the Sun make it look orange because of special filters we use to take the photo. The Sun is putting out so much light that we would not be able to photograph the detail on its surface unless we cut some of the brightness out. That’s what the filters do.

Curious Kids: why is the Sun orange when white stars are the hottest? NASA uses filters to take photos of the Sun and the filters make it look orange. NASA

At sunrise and sunset, the Sun can look especially orange to our eyes. That’s because, at those times of day, its light has to travel through a lot of the Earth’s atmosphere (the layer of swirling air that surrounds our planet). And all the dust and stuff in the atmosphere makes the light scatter and change so it looks less blue and more orangey-red.

Only Bored Astronomers Find Gratification Knowing Mnemonics

In the olden days, astronomers used letters to try to sort different types of stars. As we learned more about stars, the order changed, and labels became quite mixed up! Today we still use this naming system to remember the order of stars from hottest to least hot. It goes like this: O, B, A, F, G, K, M. (Some versions have more letters at the end).

The O-stars are the blue giants, while our Sun is a “G-class” star. That means it’s not the hottest but it’s not the coolest either.

Those letters are hard to remember, so astronomers came up with different tricks to remember it. One memory trick is called a “mnemonic” where you pretend each letter stands for a word. It’s easier to remember a sentence instead of a bunch of letters.

One student in my class came up with this mnemonic: “Only Bored Astronomers Find Gratification Knowing Mnemonics” (gratification means something like happiness).

Another one I like is: “Orange Butterflies And Frogs Get Knitted Mittens”.

Read more: Curious Kids: Why do stars twinkle?

Curious Kids: why is the Sun orange when white stars are the hottest? Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.

Authors: Belinda Nicholson, Lecturer, University of Southern Queensland

Read more http://theconversation.com/curious-kids-why-is-the-sun-orange-when-white-stars-are-the-hottest-120216

Writers Wanted

Coronavirus disrupted my kid's first year of school. Will that set them back?

arrow_forward

What are manufactured home estates and why are they so problematic for retirees?

arrow_forward

Things to Ask To Your Removalists

arrow_forward

The Conversation
INTERWEBS DIGITAL AGENCY

Politics

Did BLM Really Change the US Police Work?

The Black Lives Matter (BLM) movement has proven that the power of the state rests in the hands of the people it governs. Following the death of 46-year-old black American George Floyd in a case of ...

a Guest Writer - avatar a Guest Writer

Scott Morrison: the right man at the right time

Australia is not at war with another nation or ideology in August 2020 but the nation is in conflict. There are serious threats from China and there are many challenges flowing from the pandemic tha...

Greg Rogers - avatar Greg Rogers

Prime Minister National Cabinet Statement

The National Cabinet met today to discuss Australia’s COVID-19 response, the Victoria outbreak, easing restrictions, helping Australians prepare to go back to work in a COVID-safe environment an...

Scott Morrison - avatar Scott Morrison

Business News

Ten tips for landing a freelance transcription job

Transcription jobs are known to be popular in the field of freelancing. They offer fantastic job opportunities to a lot of people, but there are some scammers who wait to cheat the freelancers. ...

News Company - avatar News Company

How To Remove Rubbish More Effectively

It can be a big task to remove household rubbish. The hardest part is finding the best way to get rid of your junk. It can be very overwhelming to know exactly where to start with so many option...

News Company - avatar News Company

4 Tips To Pass Skills Certifications Tests

Developing the right set of skills is valuable not only to your career, but for life in general. You can get certified in these skills through obtaining a license. Without a certified license, y...

News Company - avatar News Company



News Company Media Core

Content & Technology Connecting Global Audiences

More Information - Less Opinion