Your Questions / Answered
"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
"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
"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
"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?
"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.
"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 Róbert (Erdélyi) von Fáy-Siebenbürgen - Sheffield University
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