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Howdy Stargazers, and welcome to this episode of Star Trails.

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I'm Drew, and I'll be your guide to the night sky for the week starting January 19th through

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the 25th.

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This week we're getting back to the basics with a look at the building blocks of the

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night sky, stars, where they come from, what they are, their diverse colors and types,

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and how the night sky changes with the seasons.

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Of course, we'll look at what's in the night sky this week, so let's get started.

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Hopefully you managed to catch last week's stunning full moon occultation of Mars.

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Last Tuesday started as a gloomy cloudy day here in my hometown, so I didn't get my

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hopes up.

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But by 7pm the clouds were rolling out, leaving a hazy but workable night sky.

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Mars was visible below the moon.

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By 9pm I had a clear view of the moon, and it was almost painfully bright in my 11x70

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binoculars.

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By then Mars was exactly below the moon, and because the moon was so bright it washed out

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Mars, meaning you'd need a scope or binoculars to even see it.

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I found a comfortable chair in my backyard and braced my elbows against the chair arms

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to steady my binoculars, and then watched as Mars slowly approached the moon.

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It finally vanished behind the moon's south pole around 9.12pm Eastern time.

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I went back outside around 10pm and waited until Mars emerged from behind the moon's

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northeast edge around 10.15pm, barely visible as a tiny dot and finally separating from

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the moon.

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Across town a few miles away my friend Stuart was observing the phenomenon with his 10 inch

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Dopsonian reflector, and reported being able to see ice caps on Mars.

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Overall it was a stunning night of stargazing and the first time I've witnessed an occultation

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of a planet.

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The moon is in a waning gibbous phase at the start of the week but shrinking to a crescent

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by week's end, bringing darker skies for tracking down those deep sky objects.

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The planets haven't shifted much in a week with Venus still dominating the twilight and

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early evening in the southwest.

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Saturn is still dancing nearby.

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Jupiter is the brightest object in the southern sky, rising high in the evening.

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Mars, having just reached opposition last week, remains a striking red object in Gemini,

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lining up with the bright stars, caster and Pollux.

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Winter's famous constellations like Orion, Taurus, and Gemini are still up there, but

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here are a few others you might enjoy.

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Look almost overhead if you're in mid-Northern latitudes to locate Cassiopeia.

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It's a distinctive W shape of bright stars.

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Just below Cassiopeia, Perseus arcs across the sky.

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This constellation boasts several star clusters, including the famous double cluster NGC 869

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and NGC 884.

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A pair of binoculars reveals these two close-knit clusters glimmering with countless stars.

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High in the east to southeast after sunset, Auriga is marked by its brightest star, Capella.

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Within Auriga's boundaries lie three lovely open clusters, M36, M37, and M38, all visible

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in a small telescope or even binoculars under dark skies.

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Let's get really basic here.

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Of course, we all know astronomy is the study of celestial objects, but translated from

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its Greek roots, Aster and Nomiya, it literally means name stars.

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In this Astronomy 101 segment, we're taking a very top-level look at stars.

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There's so many of them when we look up that it's easy to overlook how fascinating they

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are.

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In fact, if it weren't for stars, we wouldn't exist.

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More on that later.

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A star is essentially a colossal, luminous sphere of gas, mostly hydrogen and helium,

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held together by its own gravity.

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At its core, nuclear fusion fuses hydrogen into helium, releasing immense energy that

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radiates outward and gives the star its distinctive glow.

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Stars form in nebula, also called stellar nurseries.

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These are giant clouds of gas and dust where matter collapses under gravity.

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The star's life cycle depends heavily on its initial mass.

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All to medium stars, like our sun, can live for billions of years, while massive stars

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burn through their fuel rapidly and often end in dramatic supernova explosions.

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On a clear dark night, you can typically see a few thousand stars with the naked eye, but

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all of them lie within our own Milky Way galaxy, which contains hundreds of billions of stars.

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Though that number is staggering, our eyes aren't sensitive enough to resolve stars

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in other galaxies.

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The Andromeda galaxy, for instance, is visible from Earth with the naked eye under very dark

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skies, but only the most recent observations from space telescopes such as the James Webb

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scope have been able to resolve stars outside the Milky Way.

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Stars classify stars into different spectral types, O, B, A, F, G, K, and M, arranged from

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hottest and most massive to coolest and more common.

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O and B stars tend to be extremely hot, luminous, and blue-white in appearance.

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A and F stars are still quite bright but slightly cooler.

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G stars, such as our sun, are moderate in temperature and often yellowish-white.

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K stars appear slightly cooler and more orange, while M stars are red and they're the most

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common type, often known as red dwarves.

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The variety of colors you see among stars ties directly to their surface temperatures.

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Hotter stars can appear blue-white, while cooler stars will glow orange or red.

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This color, or spectral signature, reveals essential details about a star's life stage

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and composition.

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Blue or white stars generally burn through their hydrogen quickly because of their higher

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mass and temperature, whereas cooler red stars can have extraordinarily long lifespans, sometimes

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lasting tens of billions of years.

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When you scan the sky on any given night, you'll notice that some stars stand out more than

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others.

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This difference in brightness primarily comes from two factors, the star's intrinsic luminosity

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and its distance from Earth.

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Intrinsically luminous stars are simply more energetic because they're either larger,

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hotter, or both, which makes them shine with greater intensity.

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A star's distance from this also plays a crucial role because even a powerful star will appear

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fainter if it lies far enough away.

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Astronomers distinguish between apparent magnitude, which measures how bright a star appears to

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us on Earth, and absolute magnitude, which describes how bright a star would appear if

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it were placed at a standard distance of about 32.6 light-years.

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Using both types of magnitude helps us separate the star's true power from the effects of

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distance.

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Over millennia, cultures around the world have observed patterns in the sky and woven

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them into myths or used them for practical navigation.

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These patterns became constellations, and modern astronomy officially recognizes 88 of them,

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each marking a specific region of the celestial sphere.

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However, not every familiar pattern you see is an official constellation.

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Astorisms are smaller or more informal arrangements of stars that span or subdivide constellations

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and serve as convenient guideposts when learning the night sky.

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People often use them to orient themselves, locate specific constellations, and teach newcomers

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the basics of stargazing.

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A great example of an asterism is the Big Dipper, which is actually part of the larger

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constellation Ursa Major.

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One of the continually fascinating aspects of stargazing is the way the sky changes from

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one season to the next.

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As Earth orbits the Sun over the course of a year, the night side of our planet faces

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different regions of space.

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This means the stars you see in the sky will shift every few months.

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Even well-known constellations such as Scorpius and Sagittarius become prominent during summer

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evenings in the northern hemisphere, while others like Cygnus or Lyra might move closer

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to the western horizon.

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In winter, a different set of constellations takes center stage.

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Greek letters are used to designate stars according to a system introduced by the German

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astronomer Johann Baer in the early 17th century.

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A method often referred to as the Baer designation.

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In this system, each star within a constellation is assigned a Greek letter, alpha, beta, gamma,

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and so on, paired with the constellation's Latin name.

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Traditionally, the brightest star in the constellation is labeled alpha, the second

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brightest is beta, and so forth.

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Although this rule isn't always perfectly followed due to variations in historical brightness

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estimates and observational data.

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For example, in the constellation Lyra, the brightest star is alpha, Lyrae, better known

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as Vega, while the second brightest is beta, Lyrae.

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This scheme helps astronomers refer to specific stars in a structured way.

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Other star naming conventions exist, but Baer's Greek letter labels are among the most recognizable

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to casual and seasoned stargazers alike.

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Stars move relative to one another over very long periods.

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Given enough time, the familiar outlines of constellations will morph into completely

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different shapes.

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Right now, we see the Big Dipper as a ladle-like figure, but in a hundred thousand years, those

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same stars will no longer line up in the same way.

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In our last episode, we covered the Ecliptic, which is the plane of the Earth's orbit around

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the Sun.

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The Ecliptic is like a celestial highway in the sky because the moon, sun, and planets

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line up along it.

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The group of constellations known as the Zodiac also lies along the Ecliptic.

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There are 12 constellations in the Zodiac, 13 if you include Ophiuchus, and their names

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will probably be familiar to you, Capricorn, Virgo, Ares, and so on.

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Because the Sun appears to move through these constellations over the course of a year,

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the Zodiac became a focus of ancient astrology.

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If you're in the Northern Hemisphere, you'll notice the entire sky seems to rotate around

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one point near the North.

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That point is marked by Polaris, also known as the North Star, which lies near the North

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celestial pole where Earth's axis of rotation meets the sky.

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Because Polaris is aligned with our planet's axis, it appears almost stationary to us,

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while every other star, thanks to Earth's rotation, rises in the east and sets in the

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west.

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Conservers in the Southern Hemisphere don't have a single bright star near the South celestial

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pole, but they can still see the same circular rotation around a pivot point in the southern

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sky.

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Here's an interesting fact.

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The North Star hasn't always been Polaris, and it won't always be.

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Earth's axis slowly wobbles over a cycle of about 26,000 years, a phenomenon called

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precession.

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Because of this, the star closest to the North celestial pole changes over millennia.

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Thousands of years ago, the star Thuban in the constellation Draco was the North Star,

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and in about 12,000 years, Vega in the constellation Lyra will take that title.

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Before we wrap this up, here are some other interesting notes about stars.

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One, stars don't really twinkle. The atmospheric turbulence around Earth causes the starlight

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to bend and makes it look as though stars are flickering.

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Seen from space, without an atmosphere in the way, stars appear steady.

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Planets also show less twinkling because their discs are larger in apparent size, so the

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effect of atmospheric distortion averages out more smoothly.

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Two, looking at stars is like stepping into a cosmic time machine.

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Because light takes years to travel, when you see a star that's, say, 100 light years

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away, you're actually seeing it as it was 100 years ago.

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For nearby stars, this effect is slight, but for very distant objects, you're peering

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back into events that happened thousands or even millions of years ago.

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Three, some stars spin fast enough to flatten themselves.

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Certain stars rotate at such high speeds that they appear more oblate, meaning flattened

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at the poles and bulging at the equator.

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For example, Altair in the constellation Aquila spins so rapidly that its equatorial diameter

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is significantly larger than its polar diameter.

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Four, the biggest stars we know are mind-bogglingly large.

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While our Sun has a diameter of roughly 1.4 million kilometers, a star like U.I.

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Scudy is estimated to have a diameter of more than 1,700 times that of the Sun.

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If you placed U.I.

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Scudy where our Sun is, it would extend far beyond the orbit of Jupiter.

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And finally, you may have heard the famous Carl Sagan quote, we're made of star stuff.

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And that's because heavy elements like carbon, oxygen, and iron are forged inside stars and

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spread throughout space when those stars die, especially in supernova explosions.

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That means the atoms in your body were once part of an ancient star, and that's quite

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a humbling notion when looking up at the night sky.

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If you found this episode helpful, let me know and feel free to send in your questions

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and observations.

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The easiest way to do that is by visiting our website, startrails.show.

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This is also a great way to share the show with friends.

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Until next time, keep looking up and exploring the night sky.

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Dear skies, everyone.