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DISPLAYING POSTS TAGGED: night sky (4)

New exoplanet in our neighbourhood

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by Tanya
Publish date
29 October 2012
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Alpha Centauri is one of my favourite stars and it just got even more interesting. Astronomers from the European Southern Observatory have found a planet orbiting around it.

These days finding another exoplanet, that is a planet that orbits a distant star, isn’t so unusual. We know of over 800 exoplanets and the Kepler spacecraft has spied 2,000 more that are waiting confirmation.

But this one is special because of its star. Here’s why…

Alpha Centauri is lovely and bright, the third brightest star in the night sky, and it is prominent in our southern sky. It is the brighter star of the Two Pointers, which lead us to the Southern Cross.

Southern Cross and Two Pointers Alpha Centauri (yellow star on the far left) and Beta Centauri (blue star to the right of Alpha Centauri) point towards the Southern Cross.
Image: Akira Fujii
Source: Akira Fujii
 

Alpha Centauri is also great to look at through a telescope. What appears as a single bright star in the night sky, becomes two stars when seen through even a modest telescope. Both of the Sun-like stars – Alpha Centauri A and Alpha Centauri B – are quite similar so it looks like you’re seeing double. (A fair distance away there’s a third star too, Alpha Centauri C or Proxima Centauri, a faint red dwarf star).

At just over four light years away (or roughly 40 million million km) Alpha Centauri is the closest star to our Sun. If ever we manage to develop the capability for space travel, this is sure to be the star system we set our sights on.

And now it has a planet! The planet is orbiting Alpha Centauri B and it was hard to find, taking over four years of observations. Many follow up investigations will now begin so as to be absolutely certain.

Artistic impression of planet around Alpha Centauri B Artistic impression of the planet around Alpha Centauri B.
Source: ESO/L. Calcada/Nick Risinger
 

The new found planet has a mass similar to Earth, but takes only 3.2 days to orbit the star. It’s a scorched world, with temperatures soaring over 2000°C.

But finding one planet in this star system is really encouraging and there just might be others. If a planet was found at a more reasonable distance from this Sun-like star, it would be very interesting as far as life is concerned.

Any night sky talk I’ve ever given always includes Alpha Centauri. It’s exciting after all these years to learn something new about it.

Total Lunar Eclipse

Author
by Tanya
Publish date
8 December 2011
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I don’t know about you, but I’m already feeling the pressure of December madness. Really it’s a fantastic time of the year when we catch up with friends, celebrate with colleagues and generally wind things up for the summer. But cramming all this in alongside final deadlines and the Christmas shopping can be a mighty task!

When it all gets a bit too frantic and crazy, there’s nothing like sitting back and taking in the night sky. And this month, there’s even more reason to do so.

This beautiful composition shows the extent of Earth's shadow. It was taken from Europe, so might recognise that the Moon appears upside down.This beautiful composition shows the extent of the Earth's shadow. It was taken from Europe, so you might notice that the Moon appears upside down.
Source: Laurent Laveder

During the early hours of Sunday 11th December there will be a Total Lunar Eclipse. We can watch the Moon change colour as it plunges into the Earth’s shadow.  

The eclipse begins at 11:46pm (AEDT) on Saturday 10th December as the Sun, Earth and Moon fall into line. At first, the shadow will appear to take a bite out of the Moon. Then, the Moon will enter full shadow or totality, just after 1am on Sunday morning. It will stay in shadow for 51 minutes, a little on the short side for a lunar eclipse as they often continue for over an hour.

By 2am, the Moon will begin to light up again and it’s amazing how bright that first glimpse can be. At 3.17am all will be back to normal.

The interesting thing about an eclipse is that the shadow isn’t completely dark. The Moon takes on a reddish glow as light travels through the Earth’s atmosphere. Depending on conditions, it can also take on a hint of blue around the edges from light that passes through the ozone layer in the Earth’s upper atmosphere.

So what might we see during this eclipse? On NASA’s Science news website, atmospheric scientist Richard Keen of the University of Colarado says:

"I expect this eclipse to be bright orange, or even copper-coloured, with a possible hint of turquoise at the edge."

Sounds lovely, doesn't it? Apparently our atmosphere is nice and clear at the moment. Let's just hope the clouds stay away.

Best to try for this eclipse as we are coming up to some lean years. The next lunar eclipse will be a partial in June 2012. But to see a Total Lunar Eclipse, we'll have to wait until April 2014.

The Moon plunges into the Earth's shadow.The Moon plunges into the Earth's shadow.
Source: Public Domain

Eclipses are uncommon because the Moon's orbit (shown in green) is misaligned with the Earth's orbit around the Sun (shown in blue). If the Moon and Earth orbited in the same plane, we'd see an eclipse every Full Moon (as well as a solar eclipse every New Moon). But because the Moon's orbit is tilted by just 5 degrees, most of the time the Moon misses the Earth's shadow and moves either above or below it.

So enjoy taking some time out to appreciate the Universe we live in, as long as the weather lets us!

 

Vesta, the brightest asteroid

Author
by Tanya
Publish date
29 July 2011
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Comments (1)

Now is your chance to see an asteroid from within the asteroid belt. Vesta will be at its best for the next few weeks and it is the only asteroid that can ever be seen with the naked eye. Even thought it's smaller and further away than the dwarf planet Ceres (the largest object in the asteroid belt), Vesta's surface is great at reflecting sunlight.

Mind you, it still won't be easy. Astronomers measure brightness in magnitudes and by historic convention, the lower the magnitude, the brighter the object. The Sun comes in at a whopping -27. Alpha Centauri, a famous bright star and the closest star to the Sun, clocks in at -0.3.

In comparison Vesta, at its brightest, will reach a magnitude of 5.6. That's only just above the naked eye limit. So you will have to get out to a dark location to see it. Of course with binoculars or a small telescope you'll be doing much better. Remember though, it's only 530km across, so it will only ever look star-like.

Finding chart for Vesta at 9pm on 5th August.Finding chart for Vesta looking eastward at 9pm on 5th August, prepared with the help of "Starry Night" software.
Source: Museum Victoria

So what's so special about now? Vesta will be at opposition on the 5th August, which means opposite the Sun in the sky. It will be in the sky all night and all of the Sun's light will be shining on it (just like a Full Moon occurs when the Moon is at opposition).

And there's more - objects are generally closer to us at opposition and this opposition will bring the asteroid particularly close - still 184 million km away, but 27 million km closer than last year.

NASA's Dawn Spacecraft was 5,200km from Vesta when it took this image.NASA's Dawn Spacecraft was 5,200km from Vesta when it took this image.
Source: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

But for a really close view of Vesta, nothing can beat the Dawn Spacecraft which entered orbit around the asteroid just two weeks ago. Dawn is the first craft to orbit an asteroid and will stay with Vesta for a year before moving on to study Ceres.

Exploring Vesta is sure to uncover some fascinating science. Asteroids are the oldest objects in the Solar System and from them we hope to learn more about how the planets, including Earth, formed.

And did you know that we have more pieces of Vesta here on Earth, than we have of the Moon! It's clear that something crashed into Vesta creating a huge crater and all that rock was sent flying out into space. About 5 percent of all meteorites that fall to Earth are said to have come from that collision.

Asteroids are fascinating relics of the Solar System, if you've ever wanted to see one now's the time to do it.

Bright light in the sky

Author
by Tanya
Publish date
1 July 2011
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As I collected my boys from after school care the other evening, my seven year old stopped in the middle of the playground and cried out “Mum, what’s that in the sky? It looks like a rocket!”

He had stumbled upon the International Space Station, and let me tell you, it really couldn’t be missed. It was shining more brightly than any star and of course, it was moving. We stopped to watch it for a minute or so, as it slowly made its way across the sky before becoming lost in cloud.

International Space Station Sunlight glinting off the International Space Station.
Source: NASA
 

The boys were thrilled, especially when I told them that people were living up on that shiny dot of light. Right now, it’s home to “Expedition Crew 28”, made up of six astronauts who will live on the station from May to September.

We wondered what kind of view they were getting of the Earth. Perhaps looking down on us and seeing the twinkling lights of Melbourne and the other capital cities.

ISS Expedition 28 Crew The Expedition 28 crew members (from left to right): Flight Engineers Satoshi Furukawa, Mike Fossum, Ron Garan, Alexander Samokutyaev, Sergei Volkov and Commander Andrey Borisenko
Source: NASA
 

Maybe, like us, the astronauts were looking forward to dinner. The boys were chuffed to discover that even astronauts can eat Spaghetti Bolognese (a favourite in our household). Of course, up there you have to bolt your dinner plate down or have it float away.

If you haven’t seen the ISS, I really suggest you try. We might have lucked upon it, but there are great websites like Heavens Above that give the precise time and direction for your next chance to see it.

And while you stare up at that bright little light, travelling steadily across the night sky, I encourage you to imagine what it might be like to trade places, just for a moment,with a spacefaring astronaut.

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