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"Will it be possible to see the aurora from Kent tonight (17 Feb 2011)?"
Roger, Kent, UK

The last time we had aurora clearly visible from northern England (Lancaster) was in January 2005 and that followed an X-ray solar flare classed as an X7.

On Tuesday 15 Feb 2011 (at about 2am) we had the biggest solar X-ray flare that we have had for something like 4 years. It was an X2 class flare, that means the energy flux was greater than 0.002 Watts per square metre.

This flare was accompanied by a coronal mass ejection, which is currently travelling through interplanetary space and our best guess is that it is heading straight towards Earth. If and when it hits it could trigger a geomagnetic storm. If the CME has a large southward magnetic field component it might lead to conditions ripe for aurora over mid-latitudes (i.e. the UK).

The important words there are 'if', 'might' and 'could'. Nothing is guaranteed although this is the best chance for quite some time. The CME is still yet to strike so we don't know how big a storm we might experience; however it will need to be a severe storm for the northern lights to be visible from Kent and I suspect that is unlikely. The timing of the impact is also not favourable as it is likely to hit around 9 GMT on the 18th February - daylight!

I suspect that if any aurora is to be seen from the UK for this event it will be from Scotland or Northern Ireland. But this recent activity is an indication that solar activity is increasing as the next next solar maximum (2013) approaches, so the chances of seeing the aurora over the UK will continue to increase for the next couple of years.

Dr Andrew Kavanagh, Physics Department, Lancaster University.

"Where and when can I see the northern lights or aurora borealis?"
,

This is one of the most common questions posted by visitors to the SunEarthPlan! If you want to see some of the answers posted in response, click on the "view all questions" link below.

You might also be interested in some of the following articles within this site.

The Northern Lights: How are scientists trying to find out what causes the most intense aurora?
Aurora Alert!: Find out how Lanacster University's AuroraWatch scheme can help you see the aurora from the UK
Seeing the northern lights from Britain: Can it be done?
Man Made Aurorae: Is it possible to create aurora at the flick of a switch?
Extra-Terrestrial Aurora: Do other planets have aurora?

"What is a star made out of?"
Josie, Morecambe

A star is a gigantic ball of plasma, or gas with electrically charged particles freely moving within it.

The main element in stars is hydrogen. Our Sun is roughly made out of 90% hydrogen, 9% helium, and then traces of other elements.

Dr. Nicolas Labrosse, University of Wales Aberystwyth

"If a typical star can only ?burn? up to iron before it colapses on it?s self, how large does a star need to be to ?burn? up to plutonium or are the elements only produced during supernova?"
Philip, Derby

Stars make energy by fusing hydrogen to make helium. Late in their life, they fuse helium to make carbon. More massive stars continue producing energy by fusion making heavier and heavier elements, up to iron. Beyond iron the process doesn?t release energy.

So where do the heavier elements come from? Mostly they are made as a side effect of other processes in stars, processes that produce neutrons. Light elements capture these neutrons then undergo radioactive (beta) decay making heavier elements.

Stars like our sun do this slowly at the end of their lives making all the elements from iron to bismuth. In supernovae these and even heavier elements (like plutonium) can be made by a more rapid burst of neutrons.

Jamie Gilmour, SEAES, University of Manchester

"We want to visit Iceland this year to possibly see the northern lights. When is the most likely time of the year to see them and can anyone predict if they are more likely to appear at any particular time?"
Jenny, Leicester

This is one of the most common questions posted by visitors to the SunEarthPlan! If you want to see some of the answers posted in response, click on the "view all questions" link below.

You might also be interested in some of the following articles within this site.

The Northern Lights: How are scientists trying to find out what causes the most intense aurora?
Aurora Alert!: Find out how Lanacster University's AuroraWatch scheme can help you see the aurora from the UK
Seeing the northern lights from Britain: Can it be done?
Man Made Aurorae: Is it possible to create aurora at the flick of a switch?
Extra-Terrestrial Aurora: Do other planets have aurora?

"Is the Sun a star?"
Ron, Liverpool

The short answer is "yes"!

In fact, it's a pretty average star - the only reason is seems so different to the other stars we can see from Earth is that it's so close by.

The Sun is "only" about 150 million kilometers away from the Earth. At this distance it only takes light just over 8 minutes to get from the Sun to the Earth.

The next nearest star, Alpha Centauri, is 4.3 light years away. This means that it takes light 4.3 years to get to the Earth from Alpha Centauri. That's why Alpha Centauri appears to be a tiny pin prick of light in the sky even though it's about the same size as the Sun - it's over a quarter of a million times further away!

Dr. Jim Wild, Lancaster University

"How long does it take for a light ray to travel from the Sun to the Earth?"
Mary, Alabama, USA

Light travels at about 300,000 km per second. That's fast! For comparison, at full speed Concorde flew at only about 0.75 km per second. Still, by Earth standards, the Sun is a long way away - about 150,000,000 km away (to place this in context, the distance between London and New York is about 5550 km).

Beacuse of the huge distance, it takes a finite amount of time - just over 8 minutes - for light to get from the surface of the Sun and travel across space to reach the Earth. So when we look up at the Sun in the sky, we're not actually seeing the Sun as it appears now, we're looking at the light that left the Sun just over 8 miniutes ago!

Dr Jim Wild - Lancaster University

"We are on holiday in Skye 29 March to 5 April. Will we see the northern lights and when and where is best place to look?"
Tom, Surrey

The northern lights are a very beautiful sight, and well worth seeing if you get the chance, however they are impossible to predict more than a couple of days in advance. The problem is that at the UK's latitude they generally depend on eruptions from the Sun (called Coronal Mass Ejections, CMEs), and we never know exactly when these eruptions may happen. In addition, the eruption must come towards the Earth, otherwise it won?t interact with the atmosphere to create the aurora.

The frequency of these CMEs depend on the activity of the Sun which varies on an 11 year cycle. During the most active part of the cycle, 2-3 CMEs can erupt per day. In early 2008 we just starting to climb out of the most inactive part of the solar cycle, so CMEs are a lot rarer. At the moment the chances of seeing the northern lights in Britain are low. These chances will improve over the next 4-6 years however.

To make things harder, in order to have the Northern Lights visible in the south of England, you need a large CME to erupt from the Sun and interact with the Earth. These are much rarer, but your chances improve as you go further north towards and into Scotland.

The best time to view the Northern Lights is in the winter when the skies are much darker. You are unlikely to see much in the summer time as the skies are generally too light. In spring time, when there are still several hours of true darkness, it should still be possible to say any aurora that occur during the middle of the night. It is a good idea to find a darker viewing sight away from street lights and other sources of light pollution and look toward the northern horizon.

On a positive note though, it is possible for a large eruption to go off at anytime and come towards the Earth, so you may get lucky. To help, you can sign up to the AuroraWatch alert service run by the Lancaster University. More information about the AuroraWatch project can also be found on this website by clicking here.

"One of my dearest ambitions is to see the Northern Lights. Can you tell me whether it is possible to see if from anywhere in England at any time? I will be in Scotland 1-6 July but will the sky will be too light then?"
Mary, Kent

The northern lights are a very beautiful sight, and well worth seeing if you get the chance, however they are impossible to predict more than a couple of days in advance. The problem is that at the UK's latitude they generally depend on eruptions from the Sun (called Coronal Mass Ejections, CMEs), and we never know exactly when these eruptions may happen. In addition, the eruption must come towards the Earth, otherwise it won?t interact with the atmosphere to create the aurora.

The frequency of these CMEs depend on the activity of the Sun which varies on an 11 year cycle. During the most active part of the cycle, 2-3 CMEs can erupt per day. Unfortunately, during 2007 we are in the most inactive part of the solar cycle, so CMEs are a lot rarer. At the moment the chances of seeing the northern lights in Britain are low. These chances will improve over the next 4-6 years however.

To make things harder, in order to have the Northern Lights visible in the south of England, you need a large CME to erupt from the Sun and interact with the Earth. These are much rarer, but your chances improve as you go further north towards and into Scotland.

There are also problems with the time of year. The best time to view the Northern Lights is in the winter when the skies are much darker. You are unlikely to see much in the summer time as the skies are generally too light. It is a good idea to find a darker viewing sight away from street lights and other sources of light pollution.

On a positive note though, it is possible for a large eruption to go off at anytime and come towards the Earth, so you may get lucky. To help, you can sign up to the AuroraWatch alert service run by the Lancaster University. More information about the AuroraWatch project can also be found on this website by clicking here.

Dr Daniel Brown - University of Wales Aberystwyth

"How long does it take for the Sun?s light to hit Pluto?"
Roger, New York

Pluto?s orbit means that it is located between about 30 to 49 Astronomical Units (4.4?7.4 billion km) from the Sun. Since light travels at just under 300,000 km per second, it takes between just over 4 hours to just under 7 hours, depending on it?s Pluto?s exact position.

Prof R?bert (Erd?lyi) von F?y-Siebenb?rgen - Sheffield University

"How long does space go on for and does it ever stop?"
Emily, UK

Space is finite but unlimited. Imagine, you are a 2-dimensional flat ant living on the surface of a huge sphere. You can go around and around (unlimited) but you know that the sphere has a surface boundary (that is to say the surface is finite, provided you can see this from 3 dimensions). I know, it is tricky:)

Prof R?bert (Erd?lyi) von F?y-Siebenb?rgen - Sheffield University

"Why are the Sun?s magnetic fields twisted?"
Peter, London

The Sun is not a solid body at all. Equatorial regions rotate faster than polar regions. And to make things even more complicated, internal regions rotate with different rotation rate than surface regions. This is called differential rotation.

In general, differential rotation is seen when different parts of a rotating object move with different rates of rotation (different angular velocities).

This differential rotation spins up the dipole magnetic field lines that are generated about 200,000 km below the solar surface. This region is called the tachocline - in solar terms it is a very narrow layer.

Once the field lines are spun up, they slowly rise and emerge from the solar interior and will pop up through the visible solar surface, e.g. in the form of sunspots.

Prof R?bert (Erd?lyi) von F?y-Siebenb?rgen - Sheffield University

"I have read that over time the Earth's magnetic field will become reversed. Could you tell me over what sort of time scale this event would take place and how would we notice it?"
Derek Silvester, Kendal Cumbria.

The last reversal was about 800,000 years ago and, since the average time between reversals is about 250,000 years, you could say one is overdue. Current estimates suggest it might be another thousand years or more before the next reversal may occur. Of course the last one was so long ago that we simply don?t know the details of what happened then or will happen next time.

Our scientific models of the process suggest a reversal takes a few thousand years to complete. That?s fast on a geological time scale. During this time the well-known ?bar magnet? pattern of magnetic field lines will be distorted into much more complicated patterns.

In all likelihood there will be more than one north and one south magnetic pole, at least for a time. The overall strength of the magnetic field will decrease and may almost disappear for a time. Then the field will start to strengthen again and restore a single north and single south pole. At that time, however, magnetic ?north? on the compass will actually point south.

Dr Alan Thomson
Seismology and Geomagnetism, British Geological Survey.

"How long does it take the energy produced in the core of the Sun to travel to the Sun?s surface?"
David, London

You may be surprised: it takes about a million years for photons generated in the Sun?s core regions to reach the solar surface. Afterwards they need only about 8 minutes to reach the Earth.

The reason why it takes so long for photons to become visible is because the core is extremely dense and photons collide a lot before they can escape.

Prof R?bert (Erd?lyi) von F?y-Siebenb?rgen - Sheffield University

"What decides the colour of the northern lights?"
Angela, Fleetwood

The colour of the northern lights (or aurora) depends on the height at which they are observed. The aurora is caused by charged particles (electrons and protons) hitting the Earth?s atmosphere, which causes the atoms and molecules in the atmosphere to give off light. If the charged particles hit Oxygen atoms between about 100 and 200 km above the Earth?s surface, the atoms give off a green light. Higher up, where the atmosphere is thinner, collisions with Oxygen atoms may also give off red light. On the other hand, if the charged particles penetrate closer towards the Earth?s surface, they are more likely to hit Nitrogen molecules, which give off a blue or violet light instead.

Dr. Robert Fear, University of Leicester

"How frequently do coronal mass ejections occur?"
John, London

This depends on the level of solar activity, which has a cycle of 11 years - the Sun goes from minimal to maximal activity within 5.5 years. At solar minimum, the number of coronal mass ejections is about 1 per week, while it is 2 or 3 per day (on average) at solar maximum.

We currently are in a period of minimum activity; the next solar maximum should occur around 2011.

Dr Nicolas Labrosse - University of Wales Aberystwyth

"What creates the northern lights?"
Phil, Morecambe

The northern lights are created by charged particles from space, mainly electrons and protons, moving down along the lines of force of the Earth?s magnetic field, impacting the atoms and molecules of the atmosphere, causing it to glow. The altitude of the aurora is generally between 100 and 250 km as this is where the atmosphere becomes sufficiently dense to stop the incoming particles. The aurora are found in rings surrounding the magnetic poles of the planet, as it is here that they are guided by the dipolar shape of the magnetic field.

The ultimate source of the electrons and protons is the Sun, which blows them outwards as a constant stream known as the solar wind, at a rate of perhaps a million tonnes a second. Only a small fraction of these arrive at the environs of the Earth. How these particles then gain entrance to the region of space surrounding the Earth dominated by its magnetic field ? the magnetosphere - and how long they reside within this region before being accelerated towards the Earth to form aurora are open questions that are currently under investigation by UK scientists.

Dr Steve Milan, University of Leicester

"What?s in space and why is it black?"
Manuela, Morecambe

What is in space is not an easy question, but at least it is easy to understand why it is black: because it does not emit light.

The main celestial bodies which emit light are stars - and therefore galaxies which are large groups of stars. Between them, there are mainly dust and gas clouds which are too cold to emit light by themselves.

That is one reason why it is difficult to know what is in space: since no light is emitted, we can only get indirect evidence of what?s there.

Dr Nicolas Labrosse, University of Wales Aberystwyth

"How long does it take energy to reach the sun?s surface?"
Carla, Ohio

Energy is generated in the Sun?s core by nuclear fusion. Most of this energy is released as gamma rays. As they travel out to the surface of the Sun they bump and collide with electrons and ions. This process causes the gamma rays to slowly lose their energy and the number of rays to increase. As the rays lose their energy, they first become X-rays, then ultraviolet rays before ending up as visible light rays.

As the rays are bumping around so much, they do not take a direct route to the surface. Different rays can take different routes of different lengths, so some rays take longer than others to reach the surface. Estimates of how long this takes range from 10,000 to 50,000,000 years, however, the Cambridge Encyclopedia of the Sun gives a good average of 170,000 years.

Not all of the energy produced in the core is released as gamma rays. About 2% of the energy is released as neutrinos. These are very small sub-atomic particles that almost do not interact with matter at all. This means that they can stream out of the core virtually unhindered and they reach the surface within a few seconds of being generated.

Dr Daniel Brown - University of Wales Aberystwyth

"How large do magnetic fields need to be before reconnection can occur?"
David, London

There?s no clear threshold for magnetic reconnection to start. In fact, reconnection depends on several other factors - such as the force bringing together the two plasmas which contain the magnetic fields that you want to connect, and the angle between the two magnetic fields. (Reconnection is easier if the magnetic field lines are exactly opposite in direction than if you rotate one of the magnetic field lines by, say, 45 degrees.)

However, to give you an idea of the typical strength of the magnetic fields in this process, we measure magnetic field strength in units called nanoteslas (nT). To get a feel for this, the strength of the Earth?s magnetic field at the Earth?s surface is about 30,000 nT (but it depends on where you are!). Reconnection happens at two places in near-Earth space: at the boundary between the solar wind and the Earth?s magnetic field (which is about 60,000 km away in the direction of the Sun) and on the opposite side of the planet (the night-side: reconnection here leads to the aurora). In both these regions, the magnetic fields are typically about 20-30 nanoteslas - although they get a bit higher on the night-side - but there is no clear set level they have to reach for reconnection to start.

Dr. Robert Fear, University of Leicester

"Do you think that it will ever be possible to travel through time?"
Amanda Bebbington, Lancaster, UK

The simplest answer to this question is, of course, yes - we are constantly traveling forwards in time! According to Einstein, it is also theoretically possible to travel forwards in time at a different rate than others, by moving with a different velocity relative to them. In order for this time difference (or ?time dilation? as Einstein called it) to become particularly apparent however, you would need the difference in velocity to be something approaching the speed of light. This is all explained in his theory of Special Relativity.

Traveling backwards in time is not so easy. In fact, according to relativity, you can only travel through time in one direction. A friend and I once proved that we, at least, would never be able to travel back in time: We made a pact one afternoon that if we ever were able to time travel we would travel back to that exact point and tell ourselves. Needless to say, we didn?t turn up?

Dr. Adrian Grocott, University of Leicester

"Where does space end?"
Gemma, Morecambe

Perhaps the easiest way to answer this question is to ask another: where does the surface of the Earth end? Does it have an edge? It is thought that space is infinite, in that it has no edge. However, travel far enough in any one direction and eventually you come back to your starting point. Having said that, space is big, and it?s getting bigger all the time?.

Dr Steve Milan - University of Leicester

"How long will it take me to travel to Pluto?"
Luke, Morecambe

It will depend on your speed, and which trajectory you choose! Interplanetary spacecraft usually do not follow a straight line from A to B, as celestial bodies are moving around the Sun and using gravitational interactions with some planets can help accelerate a spacecraft quite considerably.

As an example, NASA?s New Horizons spacecraft was launched on 19 January 2006 towards Pluto, its moon, and further to study other Kuiper Belt objects. Presented by NASA as the fastest ever spacecraft, New Horizons should reach Pluto in July 2015, more than 9 years after its launch.

By comparison, light and communication signals between the spacecraft and the Earth will only take a few hours to make the journey - this time following a more conventional straight line!

Dr Nicolas Labrosse, University of Wales Aberystwyth