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This is Space Time Series 27 Episode 30 for broadcast on the
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8th of March 2024. Coming up on Space Time, could a hypothetical
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axion star pinpoint where and what dark matter is? A new study
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looking at Martian groundwater, and we pose the question, is it
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possible to fry food in space? All that and more coming up on
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Space Time.
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Welcome to Space Tiled with Stuart Garing.
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Thank you Thank you Astronomers plan on using the expected
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characteristics of a hypothetical type of star to
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improve their understanding of mysterious dark matter. The star
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is known as an axion star. It's never been seen, and even its
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component axions are just hypothetical.
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First theorized back in 1977, axions, if they exist, are light
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mass particles that could be a contender for dark matter due to
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the heat they should be giving off. However, due to the wide
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range of sizes and masses that there could possibly be, their
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potential discovery has remained elusive.
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Now a series of papers reported in the journal Physical Review
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Letters suggest that a new approach to locate this wonder
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particle if it exists could explain both dark energy and
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dark matter.
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One of the study's authors, Malcolm Fairburn from King's
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College London, says axions are one of the prime candidates for
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dark matter. Fairburn and colleagues theorized that they
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would have the capacity to heat the universe just like
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supernovae and ordinary stars after coming together in dense
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clumps.
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And it's those dense clumps that provide a target to search for.
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Einstein's general theory of relativity suggests that around
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85% of the material of the universe is dark matter, a
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mysterious invisible substance which scientists know exists
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because they can see its gravitational impact on ordinary
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baryonic matter.
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The stuff stars, planets, cars, people, dogs and cats are made
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out of. Observations show that something, some invisible
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matter, is preventing galaxies from spinning apart as they
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rotate. And that invisible matter has been named dark
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matter. But scientists have no idea what dark matter is, and
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the hypothetical axion particle is one of the contenders.
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Axions would be extremely low mass particles, but they must be
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present in very large numbers to explain the amount of dark
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matter which we infer from galaxies.
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Now, according to this new hypothesis, they could also be
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packed very densely into specific areas, meaning they're
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subject to the laws of quantum mechanics. And that would mean
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individual axions would begin to act in concert. That suggests
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there could be large groupings of axion, possibly as dark
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matter, at the centre of galaxies.
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And these could be the so-called axion stars that the authors are
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talking about. But these axion stars would become unstable once
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they moved beyond a certain mass threshold, exploding into the
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electromagnetic spectrum through radiation and photons.
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The authors suggest that these explosions have the potential to
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have heated the intergalactic gas that existed between
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galaxies in the time between the Big Bang 13.82 billion years ago
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and the formation of the first stars some 50 to 500 million
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years after the beginning of the universe, a period we refer to
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as the cosmic dark ages.
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Now all this would change the way the cosmic microwave
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background radiation will look during this period of time. The
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cosmic microwave background radiation is the leftover heat
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from the Big Bang, now cooled down to just 2.7 degrees above
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absolute zero.
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Scientists can observe this cosmic microwave background
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radiation through the hydrogen 21 centimeter measurement. So,
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by looking for signals of where axion stars might have exploded
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in the early or present universe, scientists may be able
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to use these methods to track down the so far unobserved axion
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and discover the sources of some, if not all, dark matter.
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Febern says coherent axion stars, even those which are
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relatively compact, have the potential to burst into a halo
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of electromagnetism and light. Knowing the kind of structures
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axion dark matter can form, and its impact on the surrounding
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intergalactic gas, could pave new ways for its detection.
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Being able to find axions would therefore help scientists and
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physicists solve one of science 's big questions over a century
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in the making, and at the same time help lay bare the history
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of the early universe.
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By computing the total number of axion stars in the universe, and
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by extension their latent explosive potential on
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intergalactic gas, the authors have also surmised the size of
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the signal that axion stars would give out in the cosmic
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microwave background radiation.
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And this would allow the 21cm measurements to categorise what
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is and what isn't originating from axions accurately, thereby
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aiding in the search. This is Space Time. Still to come, we
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look at the story of Martian groundwater, and we ask the
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question, would it be possible to fry foods in space? All that
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and more still to come on Space Time.
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Obrigado.
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Scientists studying the Red Planet Mars have begun searching
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for possible underground water supplies. But a new study
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predicts there'd be very little groundwater recharge in the
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ancient Martian aquifers. There 's plenty of evidence that Mars
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was once a warm, wet world.
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The geological record of the Red Planet shows evidence for water
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flooding across its surface, forming river deltas and valleys
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carved out by massive flash floods. In fact, much of the
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Martian Northern Hemisphere may once have been a giant Red
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Planet ocean.
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But a new study reported in the journal Icarus shows that no
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matter how much rainfall fell on the surface of ancient Mars, it
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seems very little of it seeped into an aquifer on the planet's
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southern highlands.
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Scientists made the discovery by modelling groundwater recharge
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dynamics for the aquifer using a range of methods from computer
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models to simple back-of-the-envelope
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calculations. But it turns out that no matter the degree of
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complexity, the results converged on the same answer, a
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minuscule 0.03 millimetres of groundwater recharge per year on
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average.
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That means that whatever rain fell in the model, only an
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average of 0.03 millimetres per year could have entered the
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aquifer and still produced the landforms remaining on the
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planet today.
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Now, for a comparison, the annual rate of groundwater
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recharge for the Trinity and Edwards Trinity Plateau
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aquifers, which provide water to San Antonio and Texas, generally
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ranges from 2.5 to 50 per year, or about 80 to 1 times more
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than the Martian aquifer recharge rate.
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The study's lead author Eric Hyatt from the University Of
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Texas at Austin says there's a variety of potential reasons for
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such a low groundwater flow rate. When it rains, the water
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may mostly have washed across the Martian landscape as runoff,
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or it may just not have rained very much on Mars at all.
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These findings can help scientists constrain the
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climatic conditions capable of producing rainfall on early
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Mars. They also suggest a very different water regime on the
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Red Planet compared to what exists on planet Earth today.
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Hyatt says the fact that the groundwater isn't as big of a
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process on Mars could mean that it just didn't rain very much on
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the Red Planet, or that runoff might simply be more important.
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What it does show is just how fundamentally different the two
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planets Earth and Mars really are. The models used in the
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study work by simulating groundwater flow in a
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steady-state environment where inflow and outflow of water into
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the aquifer is balanced.
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The study also incorporated modern topographical data
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collected by satellites. Hyatt says Mars still preserves one of
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the planet's oldest and most influential topographical
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features and extreme difference in elevation between the
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Northern Hemisphere lowlands and the Southern Hemisphere
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highlands, known as the Great Martian Dichotomy.
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And this dichotomy preserves signs of past groundwater
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upwelling in which groundwater rose up from the aquifer to the
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surface. The authors used geological markers of these past
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upwelling events to evaluate different model outputs.
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Understanding groundwater flow can help inform scientists of
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where to find water on Mars today. Whether you're looking
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for signs of ancient Martian life, or simply trying to
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sustain human explorers on the Red Planet, or making rocket
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fuel to get back home to Earth, it's essential to know where the
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Martian water is most likely to be.
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This is Space Time.
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Still to come, is frying food possible in space? And the March
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Equinox. The constellations Taurus, LEO, Corvus and
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Eridanus, and don't forget Pi Day, are among the harlots of
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the night skies on March Skywatch.
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Thank you.
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Well, if you like your fries and hash browns as much as I do,
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then there's one very obvious question that you ask yourself
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when it comes to space travel. Is it possible to fry foods in
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microgravity? And it's a legitimate question. You see,
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the food we eat determines how we feel, and as far as I'm
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concerned, nothing beats a good old fryer.
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Although in moderation, of course. As we prepare for
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missions to the moon and eventually onto Mars and beyond,
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astronauts will be happy to hear that one single comfort food is
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no longer out of reach, even in space, and that food is fries.
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Even though frying potatoes is done everywhere around the
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world, it involves complex physics and chemistry, and of
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course in space, everything becomes more complicated. You
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see, without gravity and therefore the buoyancy pulling
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upwards, bubbles might stick to the surface of the potato,
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shielding the potato in a layer of steam that might leave it
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undercooked.
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To study how microgravity influences cooking techniques
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such as frying, a novel experimental carousel-type
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apparatus was designed to be safe while also operating in
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microgravity conditions on a parabolic flight aboard a Vomit
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Comet airliner. The experiment filmed the frying process with a
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high-speed, high-resolution camera in order to capture the
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bubbling dynamics such as growth rate, size and distribution.
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As well as the escape velocity from the potato, the bubble's
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speed and direction of travel in the oil was also noted. The
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experiment also measured the temperature of the boiling oil,
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as well as the temperature inside the potato.
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Scientists reporting in the Food Research International Journal
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found that shortly after the potato was added to the oil in
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low-gravity conditions, vapor bubbles detached easily from the
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potato's surface, just like they do here on Earth. And that's got
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to be a good news story. This is Space Time.
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Time now to turn our eyes to the skies and check out the
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celestial sphere for March on Skywatch. Happy New Year! Well,
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it would be if this was ancient Mesopotamia or Rome. That's
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because March was the first month of the New Year, going
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back to the earliest concept of celebrating New Year's Day at
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the time of the vernal equinox, around 2000 BCE.
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See, the ancient Roman calendar, which had just 10 months,
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designated March 1st as the New Year. That 10-month calendar is
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still reflected today. With the name September or Septum being
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Latin for seven, October or Octo meaning eight, November or Novem
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Nine, and December or Deci meaning ten.
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It wasn't really until the Gregorian calendar that January
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1st marked the start of the New Year, but in the beginning it
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was mostly Catholic countries that adopted it. Protestant
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nations only gradually moved across, with the British, for
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example, not adopting the reformed calendar until 1752.
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Prior to that date, the British Empire and its American colonies
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still celebrated New Year's Day on March 25th.
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The highlight of the month is the March Equinox, which this
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year takes place at 14.06 in the afternoon of Wednesday, March
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20, Australian Eastern Daylight Time. That's 23.06 in the
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evening of Tuesday, March 19, US Eastern Daylight Time, and 3.06
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in the morning Greenwich Mean Time.
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For our listeners in the Northern Hemisphere, it means
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the vernal equinox, the start of spring. Although south of the
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equator, it's the autumnal equinox, meaning a move into
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autumn. The day marks the point in Earth's orbit around the Sun
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when the planet's rotational axis means the Sun will appear
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to rise exactly due east and set exactly due west to someone
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standing on the equator.
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It means almost equal hours of darkness and light. In fact, the
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very word equinox is derived from the Latin, meaning equus or
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equal, and nox meaning night. It all comes about because Earth's
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rotational axis is tilted at an angle of around 23.4 degrees in
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relation to the ecliptic, the plane created by Earth's orbit
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around the Sun.
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That axial tilt is always pointed at the same position in
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the Sky, regardless of Earth's orbital position around the Sun.
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So on any other day of the year, either the northern or Southern
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Hemisphere, it tilted more towards the Sun.
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But on the two Equinoxes, usually around March 21st and
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September 23rd each year, the The tilt of Earth's axis is
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directly perpendicular to the Sun's rays. However, there's a
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complication called precession. This causes Earth's spin axis to
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wobble ever so slightly, just like the axle of a spinning top.
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The rate of precession is only about half a degree per century,
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so people don't notice it on human timescales. And because
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the direction of Earth's axis of rotation determines at which
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point in Earth's orbit the seasons occur, precession will
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cause the particular season, for example the Southern Hemisphere
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autumn, to occur at a slightly different place from year to
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year over a 21 year cycle.
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At the same time, Earth's orbit itself is subjected to small
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changes called perturbations. See, Earth's orbit's an ellipse,
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and there's a slow change in its orientation which gradually
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shifts the point of perihelion, Earth's closest orbital position
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to the Sun.
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Now, these two effects, the precession of the axis of
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rotation and the change in the orbit's orientation, work
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together to shift the seasons with respect to perihelion. And
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because we use a calendar year that's aligned to the occurrence
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of the seasons, the date of perihelion gradually regresses
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through a 21 year cycle.
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And there's another complication. Australia and some
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of the other Commonwealth countries start their seasons on
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the first day of the month, what are referred to as
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meteorological seasons, rather than on the solstice season
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Equinoxes, which are referred to as astronomical seasons.
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So, that means Australia's autumn officially began on March
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1st, rather than on the day of the March Equinox.
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Meteorological seasons are used because it makes it easier for
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meteorologists and climatologists to break the
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seasons down into more exact three-month calendar groupings
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for comparing seasonal and monthly statistics.
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The moment of the March Equinox is also important in astronomy
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because it's used to define the celestial coordinate system of
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right ascension and declination. In astronomy, the celestial
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coordinate system is the astronomical equivalent to the
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latitude and longitudinal coordinates used on Earth's
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surface.
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It's used to specify the position of objects in
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three-dimensional space and the direction of those objects on
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the celestial sphere, the imaginary globe surrounding the
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Earth. In other words, it lets scientists determine the
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position of a celestial object, such as a satellite, a planet,
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stars, galaxies and so on.
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Right ascension, which uses the symbol Alpha, is the angular
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distance measured eastwards along the celestial equator from
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the vernal equinox. On the celestial sphere, it's analogous
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to terrestrial longitude. Declination, which uses the
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symbol delta, measures the angle north or south of the celestial
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equator, and so it's the celestial equivalent to
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terrestrial latitude.
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Marking the vernal equinox and setting the western evening Sky
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this time of year is one of the oldest recognized constellations
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in the heavens, Taurus The Bull, so named around 6 years ago.
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In Greek mythology, Taurus represents the king of the gods
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Zeus. Zeus lusted after King Agenor's daughter Europa, who
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was looking after a herd of cattle. Now being a god and with
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godlike powers, Zeus decided to transform himself into a
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powerful white bull so that he could get closer to the
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beautiful Europa.
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Now once transformed into a bull, Zeus convinced Europa to
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climb on his back and he then carried her off to the island of
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Crete. Taurus's head is represented by a dominant
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V-shaped grouping of stars. The bright reddish star in the group
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is Aldebaran, an orange giant one and a half times the mass of
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the Sun located 65 light years away. A light year is about 10
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trillion kilometres.
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The distance a photon can travel in a year at 300 kilometres
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per second, the speed of light in a vacuum, and the ultimate
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speed limit of the universe. Aldebaran is the 14th brightest
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star in the night Sky and the closest bright star to the point
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of the vernal equinox.
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In ancient Arabic, Aldebaran's name means the follower, as it
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appears to follow the seven sisters of the Pleiades. It's
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also the first of the four Royal or Guardian stars identified by
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the ancient Mesopotamians. Now that V-shaped grouping of stars
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near Ulubaran is known as the Hyades. It's the nearest young
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open star cluster to Earth, located just 153 light years
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away.
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Between Aldebaran and the Orion constellation, you'll see a
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bright red star. That's Betelgeuse, the ninth brightest
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star in the night Sky, these days more commonly called
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Betelgeuse.
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If you turn to the north now, you'll see the two bright stars
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Polax and Castor, which represent the northern
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constellation of Gemini the twins. In Greek mythology, they
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were brothers who travelled with Jason aboard the ship Argo in
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search of the Golden Fleece. Polax is an orange-hued evolved
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giant star, located 34 light-years away.
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It has about twice the Sun's mass and has bloated out to
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around 11 times the Sun's diameter. In 2006, an extrasolar
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planet or exoplanet, designated Polarx B, was discovered
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orbiting the star. The planet is a gas giant, orbiting its host
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star every 1.61 Earth years. The other star, Castor, is located
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some 51 light years away.
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It's actually a system of six stars comprising three eclipsing
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binaries. Eclipsing binaries are binary star systems in which the
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orbital plane of the two stars in the system lies so nearly
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along the line of sight from the observer here on Earth that the
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stars appear to eclipse each other.
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Looking to the northeast now, and you'll see the star Regulus,
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or Little King, the brightest star in the constellation LEO
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the Lion. LEO is mentioned by Homer in his famous 8th century
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BC poem, The Odyssey.
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According to Greek mythology, LEO was killed by Hercules as
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the first of his twelve labours. Located some 79 light years
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away, Regulus is a multiple star system, composed of at least
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four stars.
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Regulus A, designated Alpha Leonis, is a spectroscopic
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binary comprising a rapidly spinning spectral type B
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blue-white star around 3.5 times more massive than the Sun, with
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some 288 times the Sun's luminosity, and a small
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companion star, most likely a white dwarf, the stellar corpse
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of what once would have been a Sun-Like star.
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The pair take about 40 days to orbit each other. Spectroscopic
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binaries are double star systems orbiting each other so closely
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and at such an angle that they can only be visually separated,
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from our viewpoint here on Earth at least, by their spectroscopic
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signatures.
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Astronomers describe stars in terms of spectral types. It's a
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classification system based on temperature and characteristics.
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The hottest, most massive and most luminous stars are known as
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Spectral Type O blue stars. They're followed by Spectral
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Type B blue-white stars, then Spectral Type A white stars,
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Spectral Type F, Then there's whiteish yellow stars, then
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spectral type G yellow stars, that's where our Sun fits in.
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Then there's spectral type K orange stars, and the coolest
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and least massive of all stars are spectral type M red stars,
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commonly referred to as red dwarfs. Each spectral
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classification system is further subdivided using a numeric digit
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to represent temperature, with 0 being the hottest and 9 the
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coolest.
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And then you add a Roman numeral to represent luminosity. So, our
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Sun technically is a G2V or G2-5 yellow dwarf star. Also included
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in the stellar classification system are spectral types LT and
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Y, which are assigned to failed stars known as brown dwarfs,
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some of which were born as spectral type M red dwarf stars
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but became brown dwarfs after losing some of their mass.
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Brown dwarfs fit into a unique category between the largest
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planets, which can have around 13 times the mass of Jupiter,
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and the smallest spectrotype M red dwarf stars, which are
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around 75 to 80 times the mass of Jupiter, or about 0.08 solar
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masses.
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The primary star in Alpha Leonis completes a full rotation around
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its axis in under 16 hours. That 's incredibly quick, especially
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when compared to our Sun's 30-day rotational period. Now
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this gives the primary star an oblate appearance, and it causes
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what's known as gravity darkening, meaning its poles are
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considerably hotter and five times brighter per unit surface
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area than its equatorial region.
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Scientists estimate that if it were rotating just 15% faster,
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the star's gravity would be insufficient to hold it
00:22:25
together, and it would literally spin itself apart.
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Located further away are Regulus B, C and D, which are all dim
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main sequence stars. Main sequence stars are those
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undergoing hydrogen fusion into helium in their core, like the
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Sun's currently doing. Regulus B and C are thought to orbit each
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other every 600 Earth years and are located around 5
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astronomical units away from Regulus A.
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An astronomical unit is the average distance between the
00:22:53
Earth and the Sun, around 150 million kilometres, or 8.3 light
00:22:58
minutes. Regulus B is a spectrotype F white-yellow star,
00:23:02
while its companion, Regulus C, is a small spectrotype M
00:23:06
red-dwarf star. Regulus D is a bit more of a question Mark. It
00:23:10
's a dim star.
00:23:11
And, at least from our point of view, it appears to be sharing
00:23:13
motion across the Sky with other members in the group. At the
00:23:17
opposite end of the constellation of Regulus is the
00:23:20
star Beta Leonis, or Denebola, the horse's tail. It's a
00:23:24
luminous white star thought to be spectra type A, about half as
00:23:27
bright as Regulus, and the third brightest star in the
00:23:30
constellation LEO.
00:23:32
Beta Leonis has about 1.8 times the mass of the Sun and about 15
00:23:36
times the Sun's luminosity. It's suspected of being a dwarf
00:23:40
Cepheid or Dita Scuti type variable star, meaning its
00:23:43
luminosity varies very slightly over a period of several hours
00:23:46
due to pulsations on its surface.
00:23:49
Also at the other end of LEO are the stars Theta and Lota Leonis,
00:23:53
the loins of the lion. Theta Leonis is about 165 light years
00:23:57
away. It's a very young spectra type A white star, about two and
00:24:02
a half times the mass of the Sun. With an age of just 550
00:24:06
million years, Theta Leonis spectra shows enhanced
00:24:09
absorption lines for metals, that is elements other than
00:24:12
hydrogen and helium.
00:24:14
This increased metallicity appears around 12% higher than
00:24:17
the Sun, allowing the star to radiate with some 141 times the
00:24:21
luminosity of the Sun from its outer atmosphere, at an
00:24:23
effective temperature of 9350 Kelvin.
00:24:26
Literally giving it a white-hot glow. Located some 79
00:24:30
light-years away, Lothar Leonis is another spectroscopic binary,
00:24:34
consisting of two stars orbiting each other every 183 Earth
00:24:38
years. The primary star is the spectrotype F yellow dwarf star,
00:24:42
a little hotter and more massive than the Sun.
00:24:45
Algebra, or Gamma Leonis, is a binary star system with a
00:24:48
visible third component. The two primary stars are located 126
00:24:53
light-years away and can be resolved in a backyard
00:24:55
telescope. Both are yellow giants, orbiting each other
00:24:59
every 600 Earth days.
00:25:01
The unrelated tertiary star, named 40 Leonis, is a yellow
00:25:05
tinned star which can be seen through binoculars. Its
00:25:08
traditional name, Algebra, means the forehead. Other stars in the
00:25:12
system include Delta Leonis or Zosma, which is a blue-white
00:25:15
star 58 light-years from Earth, Epsilon Leonis, a yellow giant
00:25:19
some 251 light-years from Earth, and Zeta Leonis, an optical
00:25:22
triple star.
00:25:23
The brightest component is a white giant about 260 light
00:25:27
years from Earth, while the second brightest star, 39
00:25:29
Leonis, is widely spaced and is located to the south of the
00:25:33
primary, with the third and faintest star in the system, 35
00:25:36
Leonis, located to the north.
00:25:39
Also located in LEO is Tau Leonis, visible as a double star
00:25:43
through binoculars. It includes a yellow giant located some 621
00:25:47
light years from Earth and a binary secondary star, 54
00:25:50
Leonis. ...a pair of blue-white stars divisible in small
00:25:53
telescopes and located 289 light-years from Earth.
00:25:58
Also in the constellation LEO, you'll find the LEO Triplet, a
00:26:01
group of three galaxies, Messier 65, Messier 66 and NGC 3628, all
00:26:08
appearing relatively close together. Messier 65, also known
00:26:12
as NGC 3623, is an intermediate spiral, possibly barred spiral
00:26:17
galaxy, about 37 million light-years away.
00:26:21
M65 disk appears to be slightly warped. And a relatively recent
00:26:26
burst of star formation is suggestive of some gravitational
00:26:29
interaction with the other two galaxies in the LEO Triplet,
00:26:32
possibly around 800 million years ago.
00:26:34
Nearby is Messier 66 or NGC 3627, another intermediate
00:26:40
spiral galaxy, some 95 light-years wide and about 36
00:26:44
million light-years away.
00:26:46
Gravitational interaction from its past encounters with the
00:26:49
neighbouring galaxies in the triplet has resulted in
00:26:51
extremely high central mass concentration, a high
00:26:55
molecular-to-atomic-mass ratio, and a resolved non-rotating
00:26:58
clump of neutral atomic hydrogen apparently removed from one of
00:27:01
its spiral arms.
00:27:03
The third member in the group is NGC 3628, the Hamburger Galaxy,
00:27:08
a spiral galaxy with a spectacular 300
00:27:11
light-year-long tidal trail of gas and stars.
00:27:15
NGC 3628 is located 35 million light years away. Its most
00:27:20
conspicuous feature is the broad and obscuring band of dust
00:27:24
located along the outer edge of its spiral arms, effectively
00:27:27
transecting the galaxy to the view from Earth.
00:27:31
Other bright well-known galaxies in LEO include Messier 95,
00:27:35
Messier 96, Messier 105 and NGC 2903. M95 and M96 are both
00:27:44
spiral galaxies, each about 20 million light-years from Earth.
00:27:48
M95 is a barred spiral. Another barred spiral galaxy is NGC2903,
00:27:55
which is thought to be very similar in size and structure to
00:27:58
our own Milky Way galaxy. It was discovered by William Herschel
00:28:03
in 1784. Close to the M95-M96 pair is the elliptical galaxy
00:28:09
M105, which is also around 20 million light years from Earth.
00:28:14
Okay, let's turn to the east now and the constellation of Corvus
00:28:17
The Crow. In Greek mythology, Corvus was a really clever crow,
00:28:21
in fact he could talk to people. However, after refusing to speak
00:28:25
to the god Apollo, he was banished to the Sky, together
00:28:28
with Crater the Cup and Hydra the Snake. One of the brightest
00:28:32
stars in Hydra is Alphard the Solitary One, so named because
00:28:36
it appears all alone in the Sky.
00:28:39
Okay, turning to the western horizon now, and you'll see the
00:28:42
star Achenar in the southern tip of the constellation Eridanus
00:28:45
The River. Eridanus is one of the largest and longest
00:28:48
constellations in the Sky. Achenar means the river's end,
00:28:52
as it marks the end of the river Eridanus. Located around 139
00:28:57
light-years away, Achenar is a binary star system, comprising
00:29:00
two stars Alpha Eridni A and Alpha Eridni B.
00:29:04
One of the ten apparent brightest stars in the night
00:29:06
Sky, Alpha Rydeni A is a young, hot spectro-type B blue star,
00:29:11
about 6.7 times the mass of the Sun, with a stunning 3 times
00:29:16
the Sun's luminosity. Akhenar's extremely high rotational
00:29:20
velocity of over 16 km per second gives it an oblate shape,
00:29:24
making it one of the least spherical stars in the Milky
00:29:26
Way, with an equatorial diameter some 56% greater than its polar
00:29:30
diameter.
00:29:31
This distorted shape means the star displays significant
00:29:34
latitudinal temperature variations, with its polar
00:29:37
temperature being above 20 Kelvin, while its equatorial
00:29:40
temperature, being much further away from the stellar core, is
00:29:43
only around 10 Kelvin.
00:29:46
Those high polar temperatures are generating a fast polar
00:29:49
wind, ejecting matter from the star and generating a polar
00:29:52
envelope of hot gas and plasma. The companion star, Alpha Rydeni
00:29:56
b, appears to be a spectral type A white star with about twice
00:30:00
the mass of the Sun. The two stars orbit each other at an
00:30:03
average distance of roughly 12.3 astronomical units.
00:30:09
Now, just a quick reminder that March 14th marks the yearly
00:30:13
celebration of the mathematical constant, pi. Pi is the ratio of
00:30:17
a circle's circumference to its diameter. But it's also an
00:30:21
irrational number, meaning its decimal representation never
00:30:24
ends and never repeats. More than just a number, pi has
00:30:28
important applications in astrophysics, orbital mechanics
00:30:31
and other fields of astronomy.
00:30:33
It's been calculated to over a trillion digits. And the current
00:30:37
record for reciting pi from memory is over 70 digits.
00:30:41
Imagine sitting next to that person at a dinner party. As for
00:30:44
me, 359's about it. Of course, as well as Pi Day, March
00:30:50
14 is also the birthday of the great Professor Dr Albert
00:30:54
Einstein.
00:30:55
Science writer Jonathan Alley from Sky Telescope magazine
00:30:59
joins us now for the rest of our tour of the Marching Skies.
00:31:03
We'll start with the view to the south, which we normally do,
00:31:06
which is where we find plenty of bright stars. And constellations
00:31:09
to see this time of the year. First of all, of course, there's
00:31:12
the Southern Cross, which is quite easy to see at the moment.
00:31:15
It is lying on its left-hand side, so you've got to bear that
00:31:18
in mind when you go out to have a look at it. It's not standing
00:31:20
upright. It's on its left-hand side. And by cross, we mean it's
00:31:23
a crucifix state.
00:31:25
It's not like a plus symbol type cross. It's a crucifix state,
00:31:30
but it's lying on its left-hand side, down to the southeast,
00:31:32
about halfway up from the horizon. Now, don't confuse it
00:31:36
with the thing called the False Cross. Which is a
00:31:38
similar-looking group of stars in a cruciform shape, and which
00:31:43
at the moment is higher up and also lying on its left-hand
00:31:46
side. A lot of people do get these two star groups mixed up.
00:31:51
The easy way to tell them apart is that the Southern Cross is
00:31:53
smaller. Most people actually, they go out and they look for
00:31:55
the Southern Cross, and if they've got a fair idea of what
00:31:56
shape it is, they see the False Cross first because it's bigger,
00:32:01
and they think, oh, that's the Southern Cross. But down below
00:32:03
it is the real Southern Cross, and it's much smaller. If stars
00:32:06
are brighter...
00:32:08
But the cross-section itself is smaller, so that people tend to
00:32:11
not see it sometimes. It's a bit strange. Anyway, don't get
00:32:13
confused. If you're going out to look for the Southern Cross,
00:32:16
just bear in mind that there's another group of stars up there
00:32:18
that look the same shape, but a bit bigger. Now, just near to
00:32:22
the Southern Cross are the two bright stars known as the
00:32:24
pointers.
00:32:26
These are Alpha and Beta Centauri. Alpha Centauri is the
00:32:29
star system that's nearest to our solar system and is
00:32:32
comprised of three stars. One of them, a small star called
00:32:35
Proxima Centauri, is the actual closest of the three, but it's
00:32:39
far too dim to be seen unless you have a quite big telescope
00:32:43
and know exactly where you're looking.
00:32:45
The Alpha and Beta themselves are really nice and bright and
00:32:48
Alpha, as I said, is a three-star system. The closest
00:32:50
star, the tiny star, is far too dim to be seen. And even the
00:32:53
other two stars that make up... It just may look like it's just
00:32:56
one star to the naked eye.
00:32:58
There are lots of double stars up there and binary stars and
00:33:00
even triple star systems and more in the night Sky. But to
00:33:03
look at them just with the unedited eye, you wouldn't know.
00:33:06
You need to get telescope onto them and you can then start to
00:33:08
separate the two stars or three stars apart. So when you're
00:33:11
looking at Alpha, you're looking at two main stars.
00:33:16
You can see separated, even a small telescope is separated,
00:33:21
but the third one you won't see unless you get a really really
00:33:24
big telescope onto it and you know exactly where you're
00:33:27
looking. Now the Magellanic Cloud galaxies can also be seen
00:33:30
pretty much due south this month. These are two small
00:33:33
galaxies that are companion galaxies to our own Milky Way.
00:33:36
To the naked eye, they look like just fuzzy clouds, hence the
00:33:39
name. But we do need dark skies to see them, though. Where I am
00:33:43
in Big City, I struggle to see the Magellanic Clouds because
00:33:47
we've got so much light pollution around me. But if you
00:33:49
can get somewhere dark, you don't have to be out of the
00:33:51
country, just far enough away from a sporting field that
00:33:55
doesn't have it.
00:33:56
Lights on at night or something like that, or a park, or just
00:33:59
anywhere we can get away from some lights, or just block the
00:34:01
lights from view behind a building or something. And you
00:34:03
do need to let your eyes adapt to the dark, too.
00:34:05
This is a thing that people don't often realise when they're
00:34:08
starting out, is that you're going outside from being inside,
00:34:11
and the light's bright in their house. You do need at least 20
00:34:14
minutes, 30 minutes preferably, to let your eyes get adjusted to
00:34:18
the dark, and again, keep away from street lights and things,
00:34:21
because that's just going to ruin it again. Really fine
00:34:23
protector might need them.
00:34:25
And don't use a flashlight unless it's got a red filter on
00:34:27
it.
00:34:28
Yeah, red filter is a good thing to do. You can get some red
00:34:31
cellophane. Red cellophane's not the best thing to use, but if
00:34:33
that's all you've got, that's fine. You can get special red
00:34:35
filters to put over flashlights or torches. There are certain
00:34:39
wavelengths that are better than others.
00:34:40
In fact, people have tested all sorts of colours to see whether
00:34:42
they're better than red even, but red's a good bit to use. So
00:34:46
if you do need to go out and find your way around in the
00:34:49
dark, Yes, he's a Torch or a flashlight. He's got a red Torch
00:34:52
on him. Now, the Milky Way, which is our galaxy, it's just
00:34:55
our galaxy from the inside, basically.
00:34:57
It can be seen stretching from the southeast to the northwest.
00:35:00
And as you go north along the Milky Way, heading away from the
00:35:03
Southern Cross, you go through some really good constellations,
00:35:06
some of which most people would never have heard of.
00:35:08
One such as Zela and Puppet, Canis Major, Orion. Orion's one
00:35:13
that people might have heard of. Canis Major, you've got the star
00:35:15
Sirius. It's the brightest star in that constellation. And it is
00:35:18
actually the brightest star in the night Sky as seen from
00:35:21
Earth. So you really can't miss Sirius, it's nice and bright.
00:35:26
Orion, the constellation of the hunter, it's dominated at each
00:35:30
end by bright stars. At one end you've got Rhyza, on the other
00:35:33
end you've got Betelgeuse, as it probably should be pronounced.
00:35:36
And through its middle, perpendicular, runs a belt of
00:35:39
three stars. That's the hunter's belt from which dangles his
00:35:43
sword.
00:35:44
So these three stars in a straight row are very easy to
00:35:46
see. And also within Orion, you've got the famous Orion
00:35:50
Nebula. Now through its telescope, the Orion Nebula
00:35:52
looks... Really, really good. But the naked eye is just a
00:35:54
fuzzy patch. And again, you need dark area and eyes that have
00:35:57
adapted to the dark. But it's really good, even if you don't
00:36:00
have access to the telescope.
00:36:01
If you look up a picture of the Orion Nebula on the internet or
00:36:03
something and see what it looks like, and then you go outside at
00:36:06
night, and okay, all you're seeing is a little fuzzy little
00:36:08
patch.
00:36:08
But when you think, wow, I'm actually seeing that, and that's
00:36:10
what that fantastic picture is that I saw on my screen, and I
00:36:14
can actually see it, even if it 's just a fuzzy patch, I can
00:36:16
actually see it with my own eyes, and it's 1 light years
00:36:19
away, roughly. And it's just... The most amazing, it's really
00:36:22
amazing when you see something in a book or a magazine or on
00:36:24
the internet and you think, I wonder if I can see that.
00:36:27
You can go out and you can. It won't look as good, of course,
00:36:30
but you know that you are actually seeing something that's
00:36:33
hundreds or thousands or tens of thousands of light years away.
00:36:36
That's part of the fun of doing stargazing. Now, what else have
00:36:39
we got? Low down on the western horizon, sort of after sunset,
00:36:42
you've got a wedge of stars.
00:36:44
There's a reddish-coloured star at one corner. This is the head
00:36:48
of the constellation Taurus, and that reddish star is called
00:36:52
Aldebaran. The eastern half of the Sky in the evening during
00:36:55
Mars is pretty bare, really, but later in the night, after the
00:36:58
Earth has turned a bit on its axis and some more stars have
00:37:00
come up in the east, we've got the constellation Virgo.
00:37:03
Now, Virgo's a very big constellation, covers a lot of
00:37:05
the Sky, and it, too, to the naked eye, looks a bit bare. But
00:37:09
amateur astronomers just absolutely love it. Because
00:37:12
within Virgo is a huge cluster of galaxies, all sorts of
00:37:16
galaxies spread over the constellation.
00:37:18
Big ones, small ones, ones with an edge going, ones with a face
00:37:21
on, different kinds, and backyard telescopes can reveal
00:37:24
dozens and dozens and dozens of these. So amateur astronomers
00:37:27
really love this time of year, getting on towards wintertime in
00:37:30
the Southern Hemisphere and summertime in the Northern
00:37:32
Hemisphere, because Virgo's up and therefore you've got lots of
00:37:35
galaxies.
00:37:35
Now, turning to the planets, what have we got? We've got
00:37:37
Jupiter. Jupiter is big and bright in the northwest after
00:37:40
sunset. You really can't miss it. It's about a third of the
00:37:42
way up from the horizon.
00:37:44
If you are struggling to work out which one of those things up
00:37:47
there is Jupiter, that's big and bright, but go out on the 14th
00:37:50
and look for the moon because the nearest bright end of the
00:37:53
moon will be the planet Jupiter. To see Mars, you have to be up
00:37:58
before dawn, I'm afraid, so you've got to be an early riser
00:38:00
or getting to bed late. Look to the east after about 5 a.m. And
00:38:05
see if you can spot it.
00:38:05
It looks like a medium brightness, reddish, orangey
00:38:09
coloured star. Although it's not a star, of course, it's planet
00:38:12
Mars. But that's what it looks like. It just looks like a
00:38:15
little orangey red dot. But that 's planet Mars with all those
00:38:19
rovers and things roving around it and that helicopter that used
00:38:23
to be flying around. I think it 's me.
00:38:25
It's done a staff now hasn't it, the helicopter, it broke one of
00:38:28
its... Yeah, but what an amazing thing though, it just lasted so
00:38:33
fucking long, which most of these things do on Mars, they
00:38:36
tend to last a long, long time.
00:38:39
That's Mars, now about half an hour after Mars rises, the same
00:38:42
part of the Sky, Venus will rise above the eastern horizon, and
00:38:47
look, you cannot miss Venus, you cannot mistake it for anything
00:38:51
else, because it's the biggest, brightest thing. In the night
00:38:54
Sky other than the Sun and the Moon.
00:38:56
So you'll see this whopping huge bright-looking star, in inverted
00:39:01
commas, but it's actually the planet Venus. And about half an
00:39:05
hour after Venus rises, there's another planet, which will be
00:39:07
Saturn. Saturn will be rising over the eastern horizon,
00:39:11
although in the first half of the month, it'll be sort of
00:39:14
beginning of the dawn light, so it'll be a bit hard to see.
00:39:16
Wait until the second half of the month, and in particular, go
00:39:18
out and take a look on the 22nd. Really, if you've got good
00:39:21
weather, get up early, before dawn, go out in the 22nd,
00:39:24
because you'll see that Venus and Saturn have moved very, very
00:39:28
close to each other. They'll only be about a third of a
00:39:30
degree apart.
00:39:31
That's really quite close. Now, of course, they're not actually
00:39:33
really close to each other out in space. It's just a line of
00:39:36
cyber effects from our point of view on Earth. They appear to be
00:39:39
in the same direction. Having them that close together, only a
00:39:41
third of a degree apart, is pretty great.
00:39:44
And they're both quite bright. Venus is very bright. Saturn is
00:39:48
probably half that bright. But these sort of things happen
00:39:54
several times during the year with different planets, but, you
00:39:56
know, it's worth getting out to have a look at any particular
00:39:59
one.
00:40:00
To get the chance because the next one might be clouded out or
00:40:02
whatever, or you might be sleeping or forget to wake up or
00:40:06
whatever. So 22nd of March, go out in the eastern part of the
00:40:10
Sky before dawn, and you should see big bright Venus, and right
00:40:15
next door, fairly bright Saturn. And that's the end of the Sky
00:40:18
for March.
00:40:19
That's Jonathan Nally from Sky And Telescope magazine. And this
00:40:23
is Space Time.
00:40:40
And that's the show for now. Space Time is available every
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