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Dr Iain McDonald answers your astronomical questions:

Dr Iain McDonald answers your astronomical questions:

Dr Tim O'Brien answers your astronomical questions:

The first question is from Philip, who also asks about the Big Bang. He says: "It's often stated that the relative abundances of primordial elements is strong supporting evidence for the Big Bang. Please could you explain this, because, intuitively, one might have thought that, as the Universe cooled, it would have passed through temperatures high enough to synthesise even the heaviest elements, yet we're told that theory predicts pretty well what we see - hydrogen, helium and a trace of lithium."
Tim referred to two classic papers:
Alpher, Bethe and Gamow (1948) - The Origin of Chemical Elements.
Burbridge, Burbridge, Fowler and Hoyle (1957) - Synthesis of the elements in stars.
He also mentioned a book to which he had contributed some work on the history of the discovey of the cosmic microwave background (and also Henrietta Leavitt's work on Cepheid variables). The book is called Litmus: Short Stories from Modern Science.

The second question this month is from Freddie, who emailed us to say: "Hi, I was wondering - are there any meteor showers to look forward to this month?"
Good meteor shower information can be found on the websites of the International Meteor Organisation, Meteor Watch, the British Astronomical Association and the American Meteor Society.

Dr Tim O'Brien answers your astronomical questions:

The first question this month is from Roupen, who says: "I've located a star that seems to be flickering several colours in an odd way. The star is called Canopus, but I'd like to know why it flickers and why in different colours. p.s. You guys rock!"
Tim talked about ESO's adaptive optics instrumentation.

The next question is from Matthew Hyman. "In the last Jodcast you talked about our Milky Way Galaxy colliding in the future with the Andromeda Galaxy. We are told that the Universe is expanding ever quicker from the Big Bang, so my question is: if everything goes out from a central point (the Big Bang), how can two galaxies collide? Is one galaxy slower than the other? Thanks and great work!"

Next up is Philip Jones, who says: "Can you please explain how black holes lose energy by radiation and how this forms a jet of particles? Surely if it's a black hole then nothing can escape? Also, if these particles are formed from vacuum energy, how come they form a jet and are not present all around the event horizon?"
Tim referred to the radio galaxy Cygnus A - the VLA produced this classic picture of the double radio source produced by oppositely directed relativistic jets.

The final question this month is from Martin Webb, who writes: "I was wondering: is there any evidence that the speed of light in a vacuum (299,792,458 m/s) could be exceeded,or will faster-than-light travel always remain in the realm of science fiction?"
In his answer, Tim mentioned the recent paper on "faster-than-light" neutrinos. He also described how this might relate to observations of Supernova 1987A.

Dr Tim O'Brien answers your astronomical questions:

We start with a couple of questions about constellations. The first one is from Dominic who says: "I'm a junior astronomer. I can find Orion and Ursa Major/the Plough. Can you help me find other constellations from those two?"

In his answer Tim recommends downloading Stellarium and also checking out one of the nice books on constellations that are available.

Tim's answer refers to the IAU webpages on constellations, Ian Ridpath's Star Tales and the patterns of Hans Rey.

Tim discusses a paper by Cox & Loeb (2008).

Dr Tim O'Brien answers your astronomical questions:

First question this month is from Sean Mulcahy who asks "How often is the Lovell telescope struck by lightning each year, and what effect, if any, does this have on the science instruments?"Charles Woolley has a question about comets and the Oort Cloud. "Every comet that I've heard about seems to come from the Kuiper Belt. Has anyone ever discovered a comet that has an orbit that takes it back to the Oort Cloud or a comet they can say originated from there?"Next question is from Ernie Stephenson who asks "How is it that galaxies, like Andromeda for example, can exhibit a 'coherent structure' despite being thousands of light years across and given that information is carried at the speed of light? Is there some discernible difference between the top and the bottom (or left/right)?Geoff Mutton asks "The fluctuations in the cosmic microwave background are apparently caused by cold dark matter. How could it be so cold when the baryonic matter was in thermal equilibrium with radiation, then at a very high temperature?"Final question this month is from Richard Elvin. He says "After the big bang the universe cooled sufficiently to form neutral hydrogen. Ultraviolet radiation from the first stars then re-ionised it. Assuming the universe is open and continues expanding forever, will the universe ever 'de-ionise' again on its road to heat death?"

Dr Tim O'Brien answers your astronomical questions:

The first two questions this month arose as a result of Twitter discussions with @jodrellbank. First off: "Why is it so hot when the Sun is at aphelion?"The second Twitter-generated question was: "How come Neptune has only just completed its first orbit around the Sun since it was discovered in 1846?"Richard Pierce wrote in to ask: "Is it assumed that the Universe appears the same in all directions from all points, and, if so, what are the current leading theories on why this is so?"The next question is from Tim Newton, who is imagining two people racing around the Universe. One starts halfway out from the centre, the other at the edge. He wonders how long it would take them if they both travelled at 99% of the speed of light.Finally, Susan Kelly asks: "What is the difference between a thermal emission spectrum and a non-thermal emission spectrum, and is a thermal emission spectrum the same as a black-body spectrum?"

Dr Iain McDonald answers your astronomical questions:

Gareth Toye asks via e-mail: When are we going to have our first interstellar telescope? I'm sure we could get one out there quicker than it has taken Voyager. Maybe 10 years?The WISE and GAIA mission homepages.MIT press release about radio telescope on far side of Moon.Jeffery, aged 9, asks via e-mail: What is the closest star to the Sun? Is it alpha Centauri or Proxima Centauri?Alpha Centauri and Promixa Centauri on Wikipedia.Astronomy Now article on free-floating planets.Jodatheoak asks via e-mail: If the Moon pulls the Earth's crust and causes the tides to flow, why couldn't the Moon cause earthquakes?National Geographic article on the same subject.

Dr Tim O'Brien answers your astronomical questions:

The first question is from Greg. He wants to know about the relationship between mathematics and astronomy. In particular he wants to know whether, as either a professional or a hobbyist, if one lacks mathematics will a pursuit of astronomy end in a frustrated exercise? Willie Wilson has several questions about the structure of our Galaxy. Is the plane of our solar system the same as the plane of the Milky Way? Why is there a central bulge in our Galaxy? Is there matter - gas, stars, etc. - lying above and below the galactic plane and, if so, how is this matter distributed? Jim Omans from Virginia writes in to say: "While landing in a plane on a very windy day, I began to wonder if galaxies wobble. Many galaxies rotate - ours does. Do galaxies also pitch, yaw and roll as they move through space?" The next question is from Ian Kennedy: "If the Universe is expanding and everything is moving apart, how come galaxies collide?" David Entwistle wants to know how we decide on the arrangement of individual elements (e.g. aerials, dishes, etc.) in the new radio telescope systems such as LOFAR and the SKA. Finally, Mark Randles asks "When can we expect to begin to get pictures of Pluto taken by the New Horizons space probe which are of better quality and resolution than the ground-based and Hubble pictures so far obtained?"

Libby Jones puts your far-out questions to Dr Iain McDonald:

Libby Jones puts your astronomical questions to Dr Iain McDonald:

Our first question comes from Philip Murphy, who asks: "If it takes 8 minutes for light to reach the Earth from the Sun (1 AU distance), and Saturn is approximately 9 AU away, does that mean that, if the Sun stop shining, Saturn would disappear 144 minutes (9x8x2) later for us? When would we stop seeing Venus: before, at the same time as, or after the Sun went out?"

Artemi has sent us an e-mail, saying: "As far as I understand, astronomers are relatively confident about the parameters of the habitable zone around a star. Are the same parameters and relationships applicable to moons? Can a habitable moon exist around a planet that is outside its star's habitable zone?"

We have also had a question from Chris Giltnane, who asks: "Is there any way of telling, from the radiation given off by the accretion disc around a black hole, whether that black hole is swallowing ordinary matter or dark matter?"

Finally, very similar questions have been posed by MarkC, iam and Lydnen Baldwin, who all want to know: "What is space expanding into?" and: "If the Universe is expanding at an accelerating rate, what is the maximum speed it can attain?"Iain recommends Michio Kaku's book Hyperspace.

Dr Tim O'Brien answers your questions:

Libby Jones puts your astronomical questions to Dr Tim O'Brien:

Our first question is from Millie. She emailed in to ask "Hello. We've been studying the theory of relativity in Physics for GCSE and I was just wondering whether you could answer my question? If there were 2 atomic clocks, one on the Earth and one in a space ship traveling near the speed of light. If the people on the Earth could see the people on the spaceship would they have the appearance of moving slower. Or would they be moving the same as the people on Earth only thinking their clock is slow?"We had an enquiry from Roupen. He says "Is there a limit to how much matter a black hole can suck up?"The next question is from Jerry. He wrote in to say "If the universe originated at a single point with the Big Bang, and it has been expanding ever since, then should it not simply be an expanding spherical shell, rather than an essentially continuous mass?
Also, although there are slight variations in the cosmic microwave background, shouldn't there be a definite thermal gradient across the universe as a result of the expansion?"The final question this month is from Marie who says: "Like lots of people, I'm really intrigued by this newly identified planet in the Goldilocks zone of the star Gliese 581. I have a few questions:
I have read that the planet is considered to have enough gravity to hold an atmosphere. Has this been misquoted, or taken out of context, and if not, then how do we know it has gravity and/or an atmosphere? How would they be identified?
How far away from its sun is the planet?
What would it be like on a planet which has a 37 day orbit?
Which general direction in our night sky is this star system? (I know I can't see it, but I just want to know which way!)
Oh, and how old is the planet?

Libby Jones puts your astronomical questions to Dr Tim O'Brien:

Our first question is from Carol. She emailed in to ask "What passed through the sky at 8.51pm last night? Details were on the local news/weather but we missed the name etc. We were really excited at seeing this but have been unable to find out what it actually was. Hope you can help."Heavens Above - find details of visible passes of ISS and other satellites.@twisst - follow ISS on Twitter.Over Twitter - @orbitingfrog's list of feeds like @overmanchester.@jodrellbank on Twitter.

We had an enquiry from Philip Le Riche. He says "The Perseids, we are told, are the dust left behind by Comet Swift-Tuttle along its orbit around the Sun. Most of this dust (according to Wikipedia) is around 1000 years old. This puzzled me as I was watching out for them the other week. The dust certainly won't be left along the length of its orbit like an explorer carrying a leaky bag of flour in order to mark his path through a forest. In fact, the dust will be blown further and further away from the orbit by the solar wind and radiation pressure, eventually contributing to the zodiacal light, and it's hard to see how any of it could end up at the diametrically opposite end of the comet's 130 year orbit. So how is it that the Perseids can be seen year after year, and not just around the time Swift-Tuttle crosses the earth's orbit?"The International Meteor Organisation aims to encourage, support and coordinate meteor observing, to improve the quality of amateur observations, to disseminate observations and results to other amateurs and professionals and to make global analyses of observations received world-wide.Meteorwatch used Twitter to discuss the Perseid meteor shower.Calculations of the Leonid meteor shower from the Armagh Observatory group.

The next question is from Nick Beer. He wrote in to say "I gather the Universe started from a singularity at the Big Bang and has been expanding ever since. If so, in what direction relative to our Galaxy is that singularity, what is happening there, what is between it and ourselves, is matter still being created there and how far from it have we travelled in 13.5bn years? When I hear that the Universe is receding from us in all directions, and the further away the galaxies are from us, the faster they are receding, I get the impression that we are considered the centre of the universe. I hope these questions do not appear too silly; I would love to have your views. (I adore the show, by the way!)."Always a useful read: Ned Wright's FAQ in Cosmology.Recipe for currant cake - to use this as an analogue for the expanding universe you may need to adjust the amounts of ingredients!

Next we have another cosmological question from Russ Jenkins: "If I understand correctly we are not able to give an estimate of the real size of the universe, only an estimate of the furthest object it will ever be possible to see, given the age of the universe, the speed of light and a bit of adjustment for inflation. But we do have models of the Big Bang going right back to microseconds after the event. So surely we think we know what size it was then, also its total mass and total energy content. At what point do we lose track and stop being able to even estimate these things?"Ned Wright's History of the Universe.

Our final question for this month is from Ankit who writes "Dear sir, I have opted to study the electronics and communication branch of engineering (ECE). Can you please tell me whether it has any scope in astronomy. How can I then build my career in astronomy after engineering?"The e-MERLIN telescope relies on a wide range of engineering.A new view of the universe - a booklet produced by the Royal Astronomical Society which explains how technology developed for astronomy has gone to shape our world.The AAS Jobs Register includes engineering jobs relating to astronomy.

Jodrell Bank's Dr Chris Wareing answers your questions:

Emily Sellman puts her astronomical questions to Dave Jones.

Tim answers your questions:

Tim answers your questions:

Tim answers your questions:

Joe writes in to say "I've seen, as I'm sure most people have, pictures of our Galaxy. I've also seen pictures of the spiral arm where the Earth sits, usually with a circle superimposed and some text which states confidently 'you are here'. My question is, how can this be? Who or what has been far enough out to take these photographs? If these pictures are an approximation, or best guess to the structure of our Galaxy then, again, how do we know what our Galaxy should look like without being thousands of light years away from it to see?"

The 2MASS (2-Micron All-Sky Survey) near-infrared image of the whole sky.

An edge-on disc galaxy: NGC 4565.

A recent artist's impression of the structure of our Galaxy based on Spitzer Space Telescope data.

For a historical background there is the 1920 Shapley-Curtis great debate on the scale of the Universe and the 1918 paper by Harlow Shapley on the distribution of globular clusters in the Milky Way. There is a much more up-to-date paper by Gillessen et al (2009) on the distance to the black hole at the centre of the Milky Way.

Tim also mentioned a recent BBC video in which he answers the question "What is a lightyear?".

The Gaia space mission.