Our Sun has a neighbour, and it’s as cold as the North Pole. An invisible brown dwarf has been found a mere 7.2 light years away, by space telescopes searching in the infrared.
On a dark night, the sky sparkles with stars beyond counting, but even the darkest night cannot reveal every object above. It took two space telescopes to spot the star-like object called WISE J085510.83-071442.5, which is thought to be a brown dwarf.
At only 7.2 light years away, it takes the title of the fourth-closest system to the Sun. Our closest star, Proxima Centauri, is just 4.2 light years away by comparison.
Our newly-found neighbour is very good at hiding. Brown dwarfs do not have enough mass to fuse hydrogen into helium, so they don’t produce lots of visible light energy like larger stars do. This new object is invisible to us. But it does produce another kind of light – infrared. We can’t see it, but infrared sensors can. The hidden brown dwarf was revealed by two NASA space telescopes, the Wide-field Infrared Survey Explorer (WISE) and the Spitzer Space Telescope.
There are plenty of reasons to be excited about our new neighbour. It is the coldest brown dwarf ever found, with a temperature between –48 and –13 degrees Celsius. That’s similar to the North Pole! It is also particularly tiny, estimated to be three to ten times the mass of Jupiter.
At that size, it could be a gas giant planet that has lost its star system. Kevin Luhman, who discovered the object, believes it is more likely to be a brown dwarf because they are known to be fairly common. Kevin also found the third-closest system to the Sun, a pair of warmer brown dwarfs.
"It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the Sun's nearest neighbours," said Michael Werner, from NASA's Jet Propulsion Laboratory, in the press release. "This exciting new result demonstrates the power of exploring the Universe using new tools, such as the infrared eyes of WISE and Spitzer."
After thousands of years of looking with eyes, and hundreds with telescopes, it seems space still has plenty of surprises.
An artist's conception shows WISE J085510.83-071442.5, the coldest known brown dwarf. Image: Penn State University/NASA/JPL-Caltech
Quiz questions
Coprolites are a kind of trace fossil. What do they form from?
Is the Sun hotter at the visible surface or the core?
How many species of snake are there in Australia?
Which force makes water droplets fall?
Which acid is found in the stomach? a) Nitric acid, b) Aqua regia or c) Hydrochloric acid?
The 13-Storey Treehouse
Andy Griffiths’ and Terry Denton’s best-selling book comes to life.
Who wouldn’t want to live in a treehouse? Especially a 13-Storey Treehouse that has everything, including a bowling alley, a secret underground laboratory, self-making beds, a vegetable vaporiser and a marshmallow machine that shoots marshmallows into your mouth whenever you’re hungry.
Award-winning playwright and author Richard Tulloch (The Book of Everything, Bananas in Pyjamas) brings the bestselling book to the stage for an action packed hour of adventure, laughs … and gorillas!
Where: Canberra Theatre Centre When: Saturday 17 May 2014 Times: 10 am, 12 pm & 2 pm Meet Andy Griffiths! Get your book signed after the show.
Try this: Star spotting
Stick coins on a piece of paper.
On the other side, decorate some coins, and leave others blank.
Put the picture in the freezer for 15 minutes.
Ask someone if they can find the hidden stars!
You will need
Freezer
Piece of paper (we used black paper)
Five or six coins (20 cent and 50 cent pieces work best)
Sticky tape
Pens
What to do
Spread the coins out on the paper and put sticky tape over them to hold them down. These will be the shining centres of your stars.
Turn the paper over.
Gently feel for lumps on the page to find the stars. Decorate some of the stars so they look like suns, but leave others blank. These will be hidden stars.
Once you are happy with the decorations, put your picture in the freezer for 15 minutes.
Take out your picture and show it to someone, with the decorations facing up so they can’t see the coins. Put it on the table and tell them that some stars are hidden and can’t be seen. Can they find the hidden stars?
What’s happening?
By touching the paper, you can feel cold spots coming from the coins underneath and find the hidden stars. Humans have many senses and ways to perceive the world. There’s five we often talk about: sight, hearing, taste, smell and touch. Looking at your star picture, you use the sense of sight.
But humans have more senses than that. We can sense temperature, pain, balance and how our body is moving. Temperature is sensed by receptors in our skin that respond to heat and cold. The receptors send messages to our brain. So when you feel a cold spot from a coin in your picture, you can think ‘I wonder if there’s a hidden star here.’
Applications
There are other ways to perceive temperature. When objects get hot, they glow – you may have seen glowing elements inside your toaster. But cooler objects, including people and even our cold coins still send out infrared energy. Devices that detect thermal infrared energy can ‘see’ heat. Using these devices, we can make infrared pictures that make hot areas appear red, and cold areas appear blue or black.
Thermal infrared sensors can see an unseen world, a world of hot and cold. Space telescopes that can ‘see’ infrared energy can spot cold stars that don’t produce visible light, such as brown dwarfs.
The Sun is hotter in the core, where it is 15 million degrees Celsius compared to only 5500 degrees Celsius at the visible surface.
Australia has approximately 140 species of land snake and 32 species of sea snake.
Gravity makes water droplets fall.
Hydrochloric acid is the type of acid found in your stomach.
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