Ask an Astronomer - The Jodcast

Ask an Astronomer
George Bendo answers your astronomical questions:
Chris Gaunt asks: "What happens to a gravitational wave when it reaches the edge of the universe? Is it reflected back, and if so, could we detect these waves and learn something new? Does it affect the edge, perhaps pushing it further out and helping to expand the universe?" Phillip Le Riche asks: "I'm wondering whether Ultima Thule took on its present form not in the protoplanetary solar disk but in the ejecta of a previous supernova. Has any research been carried out into how supernova ejecta condenses, which would throw any light on this?" Ianto Guy asks: "Is there any evidence that the Oort Cloud really exists? How long will it be before Voyager 1 and 2 reach it? And what will be the next significant landmark they get to after that?"

Ask an Astronomer
Guillaume Voisin answers your astronomical questions:
Piran Montford asks: "I've been south of the equator recently, and I noticed that meteors seemed to move more slowly there than when viewed from the UK. In the countryside I see "shooting stars" which move incredibly quickly, but down near the equator, I saw "falling stars" which seemed to move much more slowly as they came down towards the horizon. Why is this? Is it the difference in viewing angle, darker skies, or something else?" Denis Avery asks: "If a photon of light has no mass (hence it can travel at the speed of light), why is it attracted to a black hole? I know gravity can bend light but is it a different matter with disappearing over the even horizon and into the black hole's massive gravity?" RC Davison asks: "Typically when we see an illustration of a binary system, such as a white dwarf and larger companion star, we see matter being drawn from the companion star in a tightly constrained tube. I can't see how the physics of this would work to maintain a stable structure as is commonly depicted. I think that the white dwarf would be living in a dusty disk gradually accreting matter. Can you provide some insight to what the proper system would look like?"

Ask an Astronomer
George Bendo answers your astronomical questions:
Jo Cal asks: "Telescopes are looking back into the past. What happens when they can see light that is equal to, or older than, the age of the known universe?" John asks: "What is/was the source of the cosmic microwave background radiation? Is the source still in existence and still generating radiation that will go on for ever, or has the source disappeared?" A visitor at Bluedot this year asked: "How far away from the Earth would you have to be to look back and see dinosaurs?"

Ask an Astronomer
George Bendo answers your astronomical questions:
Uranzaya asks: "How was the first telescope created, and why?" David Findlay asks: "Can you explain the equivalent of visual magnitude as applied to radio astronomy? Is there an equivalent to limiting magnitude with radio telescopes?" Graham asks: "Now that we know gravitational redshift occurs, does this also mean that the speed of light is not necessarily a constant?"

Ask an Astronomer
Mateusz Malenta answers your astronomical questions:
Colin Stenning asks: "Are there any non-Newtonian fluids that could be used in neutrino detectors instead of water, that would help limit the damage caused when one of the modules blows up and so prevent the extensive damage caused by such a situation? I'm guessing custard isn't suitable!" Frances Day asks: "Does the recent finding that there are 10 times more galaxies in the universe than previously thought have any impact on estimates of dark matter's contribution to total mass (in the Universe)?" Simon Street asks: "Is it just me, or are others worried with the degree of effort to look for (or the possibility of) life in the solar system or exoplanets? Would we be better spending the budget looking at chemistry in general on Mars, than focusing mainly on hydrocarbons? Or is this a media distortion? I totally agree it would be amazing to eventually find extraterrestrial life (independent origin from Earth), but are we in danger of not doing good science and missing something, e.g. Mars Curiosity, ExoMars, 2020 etc..?

Ask an Astronomer
Dr. Iain McDonald answers your astronomical questions:
Francis Day asks: "I saw this on FB and remembered the Ask an Astronomer section in May's Extra edition, where it was said that black holes could not account for dark matter. Also I gather that medium sized black holes were thought not to exist. Now here is NASA saying the opposite. It would be great if the Jodcast could tell us more about this extraordinary finding from NASA. I find it hard to understand how the simulation puts galaxies inside these holes." Stanley Fertig asks: "It is estimated based on MAVEN data that Mars lost at least 0.5 bar of its original CO2-rich atmosphere due to "sputtering" caused by the solar wind, against which Mars's lack of a magnetic field provided little or no protection. Venus also lacks a strong magnetic field, yet it has kept its atmosphere. Why Mars and not Venus? Is this simply the result of the latter's greater gravity?" Ann Stone asks: "The Universe has been in existence for billions of years. In that time, stars have converted huge amounts of matter to energy which travels at the speed of light away from galaxies, but the amounts of energy in transit would always be greater closer to stars/galaxies. Photons exert pressure and theoretically have energy equivalent to mass. Couldn't this account for the missing mass accounted for by the theoretical dark matter and the same photon pressure drive universal expansion (i.e. dark energy)?"

Ask an Astronomer
George Bendo answers your astronomical questions:
Phillip Rushton asks: "If neutron stars spin because of the conservation of angular momentum, do black holes spin too, and how fast?" James Walters asks: "What would we see/experience on earth if the black hole at the centre of our galaxy was active?" Owen Gwynne asks: "I've been interested in KELT as it is (with typical astronomers humour) named the Kilodegree Extremely Little Telescope. What I'm interested in though is knowing why it's described as the kilodegree telescope. My understanding is that its field of view is a lot less than 1000 'square' degrees. Can you investigate why it has that name?"

Ask an Astronomer
George Bendo answers your astronomical questions:
James Walters asks: "Have any black holes been found that are not at the centre of a galaxy?" David Kings asks: "Would there be any noticable orbitable changes in the Local Group of galaxies, following the merger of the Andromeda and the Milky Way galaxies? i.e I'm assuming the combined mass would possibly have greater gravitational effect on other objects." Hein Du Plessis asks: "How do we know that C (the speed of light) is constant over time and size of the universe? Would a C relative to the size of the universe not explain accelerating expansion more elegantly?"

Ask an Astronomer
Prof. Tim O'Brien answers your astronomical questions:
Ann Stone asks: "Our galaxy (and others) rotate which presumably stop it collapsing inwards into a massive black hole. This I believe, has been observed. Do globular clusters have a similar, independent rotation to stop their collapse, has it been observed and measured, and is it consistent with current theories?" Robert H Jenkins asks: "Is it possible to detect neutrinos and gravitational waves from the same event?" John Bowdler asks: "Gravity: What is it? Where is it? How do you turn it off?!"