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DISPLAYING POSTS TAGGED: sun (4)

Solar eclipse from space

Author
by Tanya
Publish date
31 January 2014
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During the early hours of this morning, from 12:30am to 3am, NASA's Solar Dynamics Observatory captured a stunning solar eclipse from space.  The Observatory sees a number of eclipses each year, but this was the longest one that's been recorded so far.

 

The eclipse was visible from the Observatory's vantage point, orbiting 36,000km above Earth. Since it could only be seen from space, the event is technically called a lunar transit. At its peak, the Moon covered up to 90% of the Sun.

Just as the Moon moves away, you can see a solar flare erupting from the left hand side of the Sun. This is just the kind of activity that the Observatory is helping scientists to better understand.

Solar Flare from the Solar Dynamics Observatory Perfect timing as the Sun releases a solar flare.
Source: NASA
 

Launched into space on 11 February 2010, the Observatory is on a 5 year mission to study the Sun as part of NASA's Living with a Star program. Our Sun is very active releasing flares and eruptions that can send energetic particles hurtling towards Earth. This can play havoc with our technological systems, bringing down power grids and causing blackouts. The ultimate aim is to better understand the cause of the Sun's activity so that one day we may be able to predict when such flares will occur to give us some prior warning.

The Observatory takes an image of the Sun every 0.75 seconds, and you can see all the beautiful images at the Observatory's Gallery. We have been loving the Gallery here at the Planetarium, and some of the footage will be featured in a new planetarium show to be released later this year.

Goodbye, Comet ISON

Author
by Tanya
Publish date
29 November 2013
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Comet ISON has not survived its close encounter with the Sun. Time-lapse from NASA's Solar and Heliospheric Observatory shows the comet's head fading away, leaving only a dusty tail. A few hours later something - perhaps a small fragment or stream of debris - emerges from behind the Sun. Updates are continually being posted on http://spaceweather.com/.


Final views of Comet ISON from NASA's Solar and Heliospheric Observatory (SOHO) satellite, taken on the morning 29 November (AEDT).
Source: NASA/SOHO consortium


The environment of the Sun is a tough place for comets. ISON has been bombarded by heat and radiation, buffeted by the solar wind and also stretched by the Sun's gravity (think of a micro-version of a black hole's spaghettification). It's a love-hate relationship because comets need the Sun if they are to produce an impressive tail and put on a good show.

Comet ISON was discovered in September last year from Russia, by astronomers Vitali Nevski and Artyom Novichonok. Two things made this comet special - it would be the first time the comet would travel in towards the Sun from the outer solar system but, what's more, it would be a sungrazer, coming within 1.6 million kilometres of our star.

Northern hemisphere observers have been particularly interested, because if the comet had survived its passage, they would've had the best seats. From here in the south, the comet would not have been visible, unless it had erupted brightly enough to be seen during the day.

Comet ISON - 15 November Comet ISON photographed on 15 November from the UK. Amateur astrophotographer Damian Peach used a 17-inch telescope for 12 minutes of combined exposures.
Image: Damian Peach
Source: Damian Peach


NASA's Solar TErrestrial RElations Observatory (STEREO) captured the solar wind buffeting Comet ISON and Comet Encke on 21 November.
Image: Karl Battams
Source: NASA, STEREO, CIOC

Watching the total solar eclipse

Author
by Tanya
Publish date
14 November 2012
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I had never seen a total solar eclipse before, and I was very excited to travel to Queensland to watch Australia's first solar eclipse in a decade just before 6AM this morning. 

It was incredible to wander down to the beach at 4AM and see it already packed with eclipse chasers! Thousands of people were at Palm Cove alone, more in surrounding Cairns and Port Douglas, while some headed inland where the weather prospects were better.

People on beach Eclipse chasers on the beach at Palm Cove, Queensland, awaiting the total solar eclipse.
Image: Tanya Hill
Source: Tanya Hill
 

We saw a magnificent sunrise over the water, but minutes later, when the partial eclipse was due to begin, the Sun disappeared behind clouds. It was an anxious wait but half an hour later, the clouds parted and we all donned our eclipse glasses to see a large chunk missing from the Sun.

The totality was perfect. Just beforehand you could tell that the surrounding light was different; it seemed sharp and unnatural. Then the brilliant diamond ring effect lit up the bottom of the sun and the moment had begun.

Total solar eclipse The moment of perfect totality, when the Moon was exactly in front of the Sun.
Image: Tanya Hill
Source: Tanya Hill
 

I was amazed by the colour - we could really see the pink prominences dancing around the Sun. Everyone cheered and just enjoyed the beauty of this natural show. We could see Venus shining bright above the Sun, the wispy corona and the Sun's outer gaseous layer, along with a dazzling bright ring encircling the Moon. It was surprising how long the two minutes lasted. The second diamond ring effect was blinding and spectacular as the Sun began to emerge once again.

The Yolngu of Arnhem Land tell their eclipse story of the sun-woman and moon-man coming together in the sky as husband and wife. It struck me that this is a phenomena that has been seen by so many, across thousands of years. I feel so fortunate to have shared in the experience.

Links:

'Eclipse groupies take shot in the dark,' The Age, 11 November 2012

'Eclipse sheds light on sizzling sun,' The Age, 14 November 2012 

Winter solstice

Author
by Martin Bush
Publish date
21 June 2012
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Martin is the programmer at the Planetarium at Scienceworks.

Today is the shortest day of the year, also known as the winter solstice. More correctly, it's the day on which the solstice fell, at 9:09am AEST.

Solstice means 'the Sun stands still'. Although we never see the Sun stop moving across our sky from east to west, it does stop moving in a south-north direction. Our winter solstice is the precise moment at which the Sun reaches its northernmost point in the sky, stops, then starts moving south again.

After the solstice, the Sun starts rising higher in the sky, and the points on the horizon where the Sun rises or sets start moving south.

Analemma Image of an analemma taken over the course of a year by Robert Price in Bethanga, Victoria, consisting of 48 images of the Sun superimposed on a single background image. The winter solstice occurs when the Sun is at the lowest point in this image.
Image: Robert T. Price
Source: Robert T. Price
 

Of course the Sun is not really moving south and north. Its apparent movement is a result of the Earth’s tilted axis moving around the Sun. On the winter solstice the axis is tilted away from the Sun, the Sun rises lowest in the sky and the sunlight's energy is the most diluted across the ground. You can learn more about the cause of the seasons in the Melbourne Planetarium show Tilt!

The day on which the solstice falls is the shortest day of the year, but not the day with the latest sunrise or the earliest sunset. This is because Sun time is not exactly the same as clock time.

At the winter solstice, Sun time is drifting later relative to clock time because the solar day is a little bit longer than 24 hours. For a few days after the solstice the small increase in the length of a day is not enough to overcome this drift, so the time of sunrise as measured by our clocks keeps getting later. Similarly the earliest sunset was a few days before the solstice.

Nor is the solstice the coldest day of the year. This is because of what is known as thermal inertia. It takes a lot of energy to heat up the ground and the oceans. At the moment the ground is still too warm to be heated by the amount of sunlight we are receiving, so it is continuing to cool. In around a month the balance will change. The ground will be a bit cooler and the sunlight a bit stronger, and the earth will start warming up again.

Links:

Infosheet: The Sun and the Seasons

Infosheet: The path of the Sun

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Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.

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