Archive for the ‘Science’ Category
A full Moon is set to disrupt the spectacular Perseids meteor shower when the annual display peaks on the 12 and 13 August.
The full Moon introduces natural light pollution that can be as bad the man-made glare in a city center and for the best views, star gazers are advised to escape the city lights and head out to the big open and dark skies of the countryside where the stars and meteors will be at their brightest.
The National Trust has produced a handy online guide to star gazing and listed some of its best ‘dark skies’ locations to catch a glimpse of this special and natural light show.
Dr Marek Kukula, Public Astronomer at the Royal Observatory Greenwich, said: “The Perseids are always an exciting meteor shower to watch out for. Even in large cities it’s often possible to catch site of some of the brighter Perseid meteors streaking across the sky, but from a really dark site you can sometimes see dozens per hour.
“But despite this year’s Perseid shower coinciding with the full Moon it’s still well worth going out for a look. The meteors can appear anywhere in the sky so try looking away from the bright Moon to maximise your chances of seeing one.
It always amazes me to think that what you’re seeing are tiny specks of dust from the tail of Comet Swift-Tuttle burning up high in our atmosphere. The comet left the dust behind hundreds of years ago and every August the Earth ploughs through it as it moves around the Sun. So each meteor is a little piece of evidence of the Earth’s motion through space.”
Some of the locations highlighted in the National Trust guide include the dramatic landscape around the world famous Stonehenge in Wiltshire and Mam Tor in the Peak District, high above Sheffield and only a short distance from the city of steel.
Philip Broadbent, National Trust Outdoors Programme Manager, said: “Its worth spending the time to find the perfect spot to gaze up at the stars; as once you’re there looking into the night sky it will take your breath away.
“And the best thing is that it won’t cost you a penny and this star time will always stay with you as one of those experiences that money can’t buy.”
This year the National Trust will be working with the team at meterowatch.org (twitter.com/virtualastro) to track the meteors from the Perseid shower as they appear. Tweeting the hashtag #meteorwatch on twitter, with the first part of a postcode and how many meteors seen will build an interactive map of the UK. As well as the map, meteorwatch.org is where you can find all the tips you need for observing the Perseids and lots more info.
August isn’t the only time for star gazing; its great all year round and the Trust website offers a basic introduction to astronomy, including monthly constellation guides, useful facts about the universe and where to find local astronomy groups and events.
More information can be found at http://www.nationaltrust.org.uk/darkskies or www.meteorwatch.org.
Notes to Editors:
The seven best National Trust sites for star gazing and see the wonders of the night sky are:
- Black Down in Sussex – Get closer to the stars on the highest point in the South Downs, just over a mile from the town of Haslemere.
- Teign Valley in Devon – Discover the stars at this Trust property within Dartmoor National Park and close to Castle Drogo.
- Penbryn Beach in Wales – Beautiful, unspoilt mile-long beach on the Ceredigion coast in west Wales, great for a bit of star gazing and a late night paddle.
- Stonehenge Landscape in Wiltshire – Step back in time and discover the ancient skies of Salisbury Plain’s chalk downlands, home to the impressive prehistoric stone monument.
- Wicken Fen National Nature Reserve in Cambridgeshire – Close to historic Ely, the wild landscape of the National Trust’s oldest nature reserve offers dark skies and a wealth of nocturnal wildlife to listen out for.
- Mam Tor in Derbyshire – Escape the bright city lights of Sheffield and experience the peace and tranquillity of Mam Tor’s dark skies in the Peak District.
- Friar’s Crag in Cumbria – Surrounded by the breathtakingly beautiful scenery of the Lake District, Friar’s Crag in Keswick juts out into the spectacular lake of Derwentwater; a restful place to contemplate the world above us.
More information about all of these sites is available by visiting: http://www.nationaltrust.org.uk/darkskies
Other great sites include: Flatford and the Dedham Vale on the Essex/Suffolk border, Leith Hill in Surrey, Clent Hills in Worcestershire, Buckstones in Yorkshire, Golden Cap in West Dorset, Slindon on the south Downs, South Milton Sands in south Devon, Winchelsea in East Sussex, Goldolphin Hill and Rinsey Cliff in West Cornwall, the Quantocks in Somerset, Divis Mountain above Belfast, Knole Park in Kent and Trelissick in Cornwall.
Dr Marek Kukula is the Public Astronomer at the Royal Observatory Greenwich, which is part of the National Maritime Museum. He has 15 years’ experience of astronomy research, specialising in the study of distant galaxies and supermassive black holes. Designed by Christopher Wren, the Royal Observatory, Greenwich is home of Greenwich Mean Time and the Prime Meridian and one of the most important historic scientific sites in the world. Today the galleries describe the achievements of the early astronomers, explain the history of the search for longitude at sea and tell the story of precision timekeeping, as well exploring modern astronomy. The Royal Observatory also is home to the state-of-the-art Peter Harrison Planetarium (PHP), London’s only public planetarium which has a regularly updated programme of shows.
The National Trust is Europe’s biggest conservation organisation and looks after special places across England, Wales and Northern Ireland for ever, for everyone. People and places are at the heart of everything it does. Over 3.8 million members and 61,000 volunteers help the Trust look after 300 historic houses and gardens, 1,100 kilometres of coastline and 250,000 hectares of open countryside. Find out more at: http://www.nationaltrust.org.uk/
Thursday 11th to Sunday 14th of August 2011
From Thursday 11th to Saturday 13th of August 2011 @VirtualAstro on Twitter with the help of The National Trust, Universe Today, Royal Astronomical Society and many more, will be holding a Twitter Meteorwatch for the Perseid Meteor Shower.
Everyone is welcome to join in, whether they are an astronomer, have a slight interest in the night sky or just wonder?
As well as looking up, enjoying the night sky with us and seeing meteors, maybe for the first time? You will have the opportunity to contribute for fun with images and online, or to Science if you wish, by tweeting and seeing your results on a map, or by submitting Observing Forms if you are a more serious observer.
Use the hash tag: #Meteorwatch and get involved, ask questions, do some science, follow the event and enjoy the wonders of the night sky with us. Images and other information will be tweeted as it happens. Live!
Join in on Twitter, Facebook and Google+
The highlight of the summer meteor showers: The Perseids reach maximum around the 12th/ 13th of August and may put on a display of approximately 80 to 100 meteors per hour under ideal viewing conditions.
Conditions this year aren’t ideal due to there being a full moon, but the brighter meteors will be seen. Let’s hope the skies stay clear.
Perseid meteors are often bright with persistent trails which can linger for a while after the meteor has burned up. Further information on the Perseid meteor shower and how to view it, can be found here.
While you are looking for meteors, there will be other objects to look out for such as the Planet Jupiter late in the evening, the Milky Way, Summer Triangle, manmade Satellites and more.
The Twitter Meteorwatch will start at 21.00 BST on the 11th of August and will continue through to the evening of the 13th. Amateur and professional astronomers and stargazers from the US and other countries are invited to join in and take over from the UK, when the sun comes up here, helping make the event run continuously and be truly international.
Watch the awesome new trailer here….
Tonight (actually around 0130 tomorrow morning) the Full Moon will reach its highest point due south, just an hour and a half after the eclipse ends. Despite being at its highest in the sky, you’ll still struggle to see it, as it is very low down. In fact the Full Moon nearest the Summer Solstice is the lowest Full Moon of the Year
First, let’s begin with the definition of “Full Moon”. A Full Moon occurs when the Moon is diametrically opposite the Sun, as seen from the Earth. In this configuration, the entire lit hemisphere of the Moon’s surface is visible from Earth, which is what makes it “Full”. There is an actual instant of the exactly Full Moon, that is the exact instant that the Moon is directly opposite the Sun. Therefore when you see timings listed for the Full Moon they will usually include the exact time (hh:mm) that the Moon is 180° round from the Sun (we call this point opposition). Here’s a list of the times of all Full Moons between June 2011 and June 2012:
|Month||Date of Full Moon||Time of Full Moon (UT)|
|June 2011||15 June||2014*|
|July 2011||15 July||0640*|
|August 2011||13 August||1857*|
|September 2011||12 September||0927*|
|October 2011||12 October||0206*|
|November 2011||10 November||2016|
|December 2011||10 December||1436|
|January 2012||09 January||0730|
|February 2012||07 February||2154|
|March 2012||08 March||0939|
|April 2012||06 April||1919*|
|May 2012||06 May||0335*|
|June 2012||04 June||1112*|
* UK observers should add on one hour for BST As you can see from this table, the instant of the Full Moon can occur at any time of day, even in the daytime when the Moon is below the horizon. So most often when we see a “Full Moon” in the sky it is not exactly full, it is a little bit less than full, being a few hours ahead or behind the instant of the Full Moon. I’ll refer to this with “” marks, to distinguish this from the instant of the Full Moon (they look virtually identical in the sky). The Moon rises and sets, like the Sun does, rising towards the east and setting towards the west, reaching its highest point due south around midnight (although not exactly at midnight, just like the Sun does not usually reach its highest point exactly at noon). And like with the Sun the maximum distance above the horizon of the “Full Moon” varies over the year. The Sun is at its highest due south around noon on the Summer Solstice (20 or 21 June) and at its lowest due south around noon on the Winter Solstice (21 or 22 Dec) (of course the Sun is often lower than this, as it rises and sets, but we’re talking here about the lowest high point at mid-day, i.e. the day of the year in which, when the Sun is at its highest point that day, that height is lowest…) And because Full Moons occur when the Moon is directly opposite the Sun, you can imagine the Moon and Sun as sitting on either sides of a celestial see-saw: on the day when the Sun is highest in the middle of the day (in Summer), the Moon is at its lowest high point at midnight; and on the day when the Sun is at its lowest high point in the middle of the day (in Winter), the Moon is at its highest high point at midnight. This means, in practical terms, that Summer “Full Moons” are always very low on the horizon, while Winter “Full Moons” can be very high overhead. Here’s a table of the altitude of the “Full Moon” when due south. Remember the times in this table don’t match the exact time of the Full Moon, but instead have been chosen as the closest in time to that instant, and so have be labelled “Full Moon” (in quotes).
|Month||Date of Full Moon||Time of Full Moon (UT)||Time/Date of “Full Moon” due S||Time from/since instant of Full Moon||Altitude due S (degrees)**|
|June 2011||15 June||2014*||0127BST 16 June 2011||+4h13m||10° 05′|
|July 2011||15 July||0640*||0012BST 15 July 2011||-7h28m||10° 24′|
|August 2011||13 August||1857*||0126BST 14 August 2011||+5h27m||19° 19′|
|September 2011||12 September||0927*||0049BST 12 September 2011||-9h38m||31° 49′|
|October 2011||12 October||0206*||0053BST 12 October 2011||-1h13m||44° 16′|
|November 2011||10 November||2016||0005GMT 11 November 2011||-3h49m||53° 24′|
|December 2011||10 December||1436||0030GMT 11 December 2011||+9h54m||56° 03′|
|January 2012||09 January||0730||0006GMT 09 January 2012||-7h24m||53° 36′|
|February 2012||07 February||2154||0031GMT 08 February 2012||+2h37m||43° 47′|
|March 2012||08 March||0939||0000GMT 08 March 2012||-9h39m||35° 37′|
|April 2012||06 April||1919*||0145BST 07 April 2012||+5h26m||21° 45′|
|May 2012||06 May||0335*||0102BST 06 May 2012||-3h33m||15° 20′|
|June 2012||04 June||1112*||0047BST 04 June 2012||-11h25m||11° 49′|
* UK observers should add on one hour for BST ** The altitude here is based on my observing location in Glasgow, Scotland. You can find out how to work out how high these altitudes are here. As you can see from this table, the highest “Full Moon” due S this year occurs at 0030 on 11 December 2011, when the Moon will be over 56° above the southern horizon (approximately the height of the midsummer mid-day Sun which culminates at 57°34′). Compare this to the “Full Moon” this month, just after the eclipse, in the morning of 16 June, when the Moon barely grazes 10° above the horizon, and you can see just how low the midsummer Full Moon can be. In fact the closeness of summer “Full Moons” to the horizon means that this is an ideal time of year to try and observe the Moon Illusion.
Today, 13 June, is one of only four days in the year when the time as read on a sundial will be exactly correct.
Sundials usually tell the time using the shadow of the gnomon as cast by the Sun. This is possible as the Sun appears to move across the sky at an approximately constant speed, and so the shadow of the gnomon also moves at an approximately constant speed. The inconstancy of the Sun’s apparent motion in the sky – and therefore of the gnomon’s shadow on a sundial – is the subject of this article, and is calculated using the Equation of Time.
If you look at the shadow of a sundial’s gnomon it will fall onto a curve of numbers, along hour lines indicating local solar time. This is not equal to the official clock time until three important corrections are made:
Please read the rest of this article on Dark Sky Diary
I am often asked or hear about bright fireballs in the sky, often reported by non astronomy minded people, so when you ask where was it and what direction it was travelling etc, you get very sketchy information back like: It was over my house and headed towards town, I think?
Only if you have many sightings of the same fireball can you interpolate where it was and what direction etc it was travelling? Things are going to be made a lot easier if you live in some parts of the United States.
NASA is building a network of "Meteor Cameras" in a few of States in the US called the "All-sky Fireball Network". This is a network of cameras set up by the NASA Meteoroid Environment Office (MEO) with the goal of observing meteors brighter than the planet Venus, which are called fireballs. The collected data will be used by the MEO in constructing models of the meteoroid environment, which are important to spacecraft designers.
The Network will eventually consist of up to 15 overlapping cameras in north Alabama, northwest Georgia, and southern Tennessee, placed on public buildings and schools. The network will use sensitive black and white cameras which are able to see the whole of the sky (All Sky).
Because the cameras have overlapping fields of view, more than one camera can see the same meteor at the same time, helping in getting data about its trajectory and with clever data collection software, ascertain if the meteor came from a comet or an asteroid.
NASA’s All-sky Fireball Network uses ASGARD (All Sky and Guided Automatic Realtime Detection). ASGARD not only handles all the data processing (which is considerable) it also automatically pushes the results to the web. See the results here: http://fireballs.ndc.nasa.gov
I’ll make a prediction: on or around 19 March, when the so-called “Supermoon” occurs, at its closest approach to Earth in two decades, people will indeed report that the Moon looks much bigger than normal. But it won’t really be much bigger in the sky at all. It’s all in our heads!
You’ve probably all seen it before, a huge Full Moon sitting on the horizon. Time and again I have had people ask me why the Moon is so much bigger some times than others, and the answer is: it isn’t, really.
The Moon orbits the Earth in an elliptical orbit, meaning that it is not always the same distance from the Earth. The closest the Moon ever gets to Earth (called apogee) is 364,000km, and the furthest is ever gets (perigee) is around 406,000km (these figures vary, and in fact this Full Moon on 19 March 2011 will see a slightly closer approach of 357,000km).
So the percentage difference in distance between the average perigee and the average apogee is ~10%. That is, if the Full Moon occurs at perigee it can be up to 10% closer (and therefore larger) than if it occurred at apogee.
This is quite a significant difference, and so it is worth pointing out that the Moon does appear to be different sizes at different times throughout the year.
But that’s NOT what causes the Moon to look huge on the horizon. Such a measly 10% difference in size cannot account for the fact that people describe the Moon as “huge” when they see it low on the horizon.
What’s really causing the Moon to look huge on such occasions is the circuitry in your brain. It’s an optical illusion, so well known that it has its own name: the Moon Illusion.
If you measure the angular size of the Full Moon in the sky it varies between 36 arc minutes (0.6 degrees) at perigee, and 30 arc minutes (0.5 degrees) at apogee, but this difference will occur within a number of lunar orbits (months), not over the course of the night as the Moon rises. In fact if you measure the angular size of the Full Moon just after it rises, when it’s near the horizon, and then again hours later once it’s high in the sky, these two numbers are identical: it doesn’t change size at all.
So why does your brain think it has? There’s no clear consensus on this, but the two most reasonable explanations are as follows:
1. When the Moon is low on the horizon there are lots of objects (hills, houses, trees etc) against which you can compare its size. When it’s high in the sky it’s there in isolation. This might create something akin to the Ebbinghaus Illusion, where identically sized objects appear to be different sizes when placed in different surroundings.
2. When seen against nearer foreground objects which we know to be far away from us, our brain thinks something like this: “wow, that Moon is even further than those trees, and they’re really far away. And despite how far away it is, it still looks pretty big. That must mean the Moon is huge!”.
These two factors combine to fool our brains into “seeing” a larger Moon when it’s near the horizon compared with when its overhead, even when our eyes – and our instruments – see it as exactly the same size.
There seems to be a growing excitement about the “Supermoon” that is due to occur on 19 March 2011, when the Moon will be at its closest to Earth in this orbit, and closer than it has been at any time since 1992.
The Moon orbits the Earth in an elliptical orbit, i.e. it is not perfectly circular, and so in each orbit there is a closest approach, called “perigee” and a furthest approach, called “apogee”.
At this month’s perigee the Moon will be 356,577km away from Earth, and will indeed be at its closest in almost 20 years. But how close is it compared with other perigees?
Let’s start by comparing it to the Moon’s average distance from the Earth, which is ~385,000km. This perigee will be ~8% closer to the Earth than average. OK, that’s a bit closer, but not significantly so.
What about comparing it to the Moon’s average perigee distance, which is ~364,000km. So this “Supermoon” will be ~2% closer to the Earth than it is most months at perigee. Wow!
So what will this mean to you? Nothing at all. The Moon will be a few percent bigger in the sky, but your eye won’t really be able to tell the difference. It will also be a few percent brighter, but your eye will compensate for this too, so altogether this “Supermoon” will look exactly the same as it always does when it’s full.
As to all of those soothsayers claiming that there will be earthquakes and tidal waves. There very well might be, but they’ll be nothing at all to do with the Moon.
UPDATE: I predict that lots of people will report having seen a huge Moon on or around 19 March
The night sky has many wonderful objects to look at on a clear evening, including many man-made satellites, and the always impressive International Space Station (ISS). Now there’s a new addition to these artificial delights: the first ever solar sail to orbit the Earth, NASA’s Nanaosail-D Satellite. Want to know how you can see it?
The 10m x 10m reflective sail is designed to act like a brake and gradually create drag in the upper atmosphere, slowly pulling a satellite down and de-orbiting it at the end of its working life. Nanosail-D is testing the potential of this technology to reduce space junk and debris.
The satellite has a huge reflective sail and could potentially be many times brighter than the planet Venus when it catches a glint from the Sun. Unlike the International Space Station (ISS) and other satellites, the sail will not be visible when it is directly above us as we will be looking at it edge on, It will be more visible when closer to the horizon.
The Nanosail-D satellite will be visible from now and for the next few months. To see it you will need to know exactly when it will be visible from your location. To do this, go to heavens-above.com or spaceweather.com where star charts with times and pass details will be displayed after you enter your observing site.
Once you know the time and location in the sky of the pass of the satellite, make sure you are able to get a good view of the horizon, or part of the sky where the satellite due to appear. Give yourself plenty of time, go outside and get ready. I always set a 30 second reminder on my watch or cell phone, so I don’t have to fumble around or guess the time.
Unlike the ISS and most other satellites, Nanosail-D passes may only last a few, or a few tens of seconds, so make sure you are looking in the right place at the right time. You will see an amazingly bright star-like object rise up, get brighter and then suddenly disappear. When it “disappears” it is still passing over, it’s just no longer at the right angle or is no longer being illuminated by the sun. NanoSail-D has few reflective surfaces compared to many on the ISS.
To enjoy the Nanosail-D passes:
• Make sure you know the right place in the sky and the time of the pass, by checking on the web.
• Make sure you will be able to get a clear view of it from your viewing location.
• Set an alarm or get ready for the pass as it only lasts a few seconds.
• NASA expects NanoSail-D to stay in orbit until April or May 2011.
• If you are an astrophotographer, don’t forget, NASA and SpaceWeather.com are having an imaging contest of NanoSail-D. Find out more here.
• Most of all, get your friends and family outside with you to watch Nanosail-D and enjoy!
Over two weeks between 21 February and 06 March 2011 you can take part in the international project GLOBE at Night, an annual 2-week campaign. During GLOBE at Night, you can record the brightness of your night sky by matching its appearance against the constellation Orion with star maps of progressively fainter stars. Your measurements are submitted on-line and a few weeks later, organizers will release a map of light-pollution levels worldwide. Over the last five GLOBE at Night campaigns, volunteers from over 100 countries have contributed 35,000 measurements.
So what exactly do you need to do? It’s simple, just visit the GLOBE at Night website and follow their instructions. You’ll need to:
1. print out the Orion maps from the activity pack
2. go outside and find Orion. Make sure you wait till it’s properly dark, which is after about 2015 your time. Hint, Orion will be towards the south, and looks like this:
3. compare what you see with the seven Orion maps, and note down which one it looks like the most. This will tell you the magnitude (brightness) of the dimmest stars you can see
4. report your observation using the GLOBE at Night web app or through their website including the date and time you made the observation, and your latitude and longitude (don’t worry, there’s an interactive map that’ll help you find these).