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Venus at Peak Brilliance and the Voyager Golden Record · Star Trails: From Backyard Astronomy to Cosmic Wonder

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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 February 16th through
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the 22nd.
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This week Venus takes center stage as it approaches peak brightness.
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We'll discuss the phases of Venus and why its brightness fluctuates over the course
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of a year.
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Plus we'll examine one of astronomy's oldest mysteries, the ashen light of Venus.
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Later in the show we'll hop aboard the Voyager space probes and listen to the Voyager Golden
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Record, humanity's message in a bottle that's still adrift in the cosmic ocean.
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But first let's start with what you can see from your backyard this week.
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So grab a comfortable spot under the night sky and let's get started.
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Our moon starts the week in a waning gibbous phase, gradually decreasing in illumination
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each night.
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By the 20th the moon will enter its third quarter with exactly half of the surface illuminated.
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During this period the moon rises relatively late around midnight so you'll have darker
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skies to chase down those dimmer objects such as nebula, galaxies, and star clusters.
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Saturn is becoming challenging to observe as it moves closer to the sun's glare.
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By mid-February it appears low in the western sky shortly after sunset and sets within a
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couple hours.
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On February 16th Venus will reach its peak brightness for the year, shining at a very
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bright magnitude of negative 4.2.
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It will be prominently visible in the western sky after sunset, remaining observable for
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several hours into the evening.
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This is an ideal opportunity for observation as it will outshine all other celestial objects
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except the moon.
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Jupiter will be high overhead in the evening sky, appearing very bright.
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It's an excellent time to observe the planet's features and its Galilean moons through a
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telescope, and because it's high in the sky there's less atmospheric turbulence, resulting
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in a clearer view.
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Mars continues to be visible in the evening sky, located in Gemini, high in the east after
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sunset.
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Its reddish hue makes it distinguishable from other celestial objects nearby.
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While a complete 7-planet alignment, including Mercury, is expected around February 23rd,
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this week you can still observe a notable alignment of Venus, Mars, Jupiter, and Saturn,
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all following the ecliptic plane across the evening sky.
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Uranus and Neptune are also positioned along this arc but require binoculars or a telescope
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to view.
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As always, for optimal viewing, find a location with minimal light pollution and a clear view
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of the horizon.
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Using a stargazing app can help you identify and locate these celestial objects in the
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night sky.
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As Venus is on its way to peak brightness this week, I thought I'd take a moment to
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offer up some viewing tips for our planetary neighbor, which is often referred to as the
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evening star or morning star, depending on its visibility.
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If you've never looked at Venus through a telescope, you may be surprised to learn it
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exhibits phases, much like our moon.
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This cycle was first recorded by Galileo in the early 17th century and provided crucial
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evidence for the heliocentric or sun-centered model of the solar system.
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Through a telescope, you'll notice that Venus is quite dynamic.
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It changes both in shape and apparent size over time, going through the following phases.
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Full Venus occurs at superior conjunction, when Venus is on the far side of the sun,
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completely illuminated but appearing small and distant.
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It's also in the sun's glare, making it more difficult to see.
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As Venus moves along its orbit toward Earth, we begin to see a shadowed portion similar
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to a waxing or waning moon.
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This is the gibbous phase.
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Half Venus occurs when it reaches greatest elongation, meaning it appears at its farthest
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angular distance from the sun in the sky.
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As Venus moves closer to Earth, the illuminated portion shrinks into a crescent, but the planet
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itself appears much larger in our sky.
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This phase is called crescent Venus.
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A new Venus, or inferior conjunction, occurs when it passes directly between the Earth
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and Sun, appearing as a dark silhouette against the solar disk if perfectly aligned, which
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is a rare event known as a transit of Venus.
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Then the cycle reverses as Venus moves back toward the far side of the sun.
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The phases of Venus occur because of its orbit around the sun and our changing perspective
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from Earth.
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Unlike the moon, which orbits Earth, Venus orbits the sun in an inner orbit, meaning
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that it moves between us and the sun periodically.
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This causes different portions of its sunlit side to be visible at different times.
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Galileo's observations of these phases were groundbreaking because they disproved the
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old geocentric model of the solar system.
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If Earth were at the center, Venus would not show the full range of phases.
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Even though Venus is fully illuminated when it's on the far side of the sun, it appears
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smaller and dimmer because of its greater distance from us.
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Conversely, when it's in its crescent phase and closer to Earth, it appears much larger
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and brighter.
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This is why Venus shines most brilliantly as a thin crescent just before or after inferior
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conjunction.
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The complete cycle of Venus' phases from full to crescent and back to full takes about
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19 months.
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This corresponds to Venus' synodic period, which is the time it takes for Venus to return
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to the same position relative to the sun as seen from Earth.
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However, each phase does not last an equal amount of time because Venus' movement is
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more apparent when it's closer to Earth and slower when it's farther away.
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Here's a breakdown.
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Full Venus to half Venus' de Gibbes phase lasts about 146 days as Venus moves from
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fully illuminated but far away to when it appears half lit.
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Half Venus to crescent Venus takes about 72 days as Venus moves towards Earth and its
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crescent becomes thinner.
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Crescent Venus to new Venus is much quicker, taking about 36 days since Venus is moving
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rapidly in its closer inner orbit.
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These phases are the same lengths but in reverse as Venus cycles back to full, new Venus to
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crescent crescent to half, and so on.
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Venus Watchers may also want to try chasing down the elusive Ashen light.
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It's one of the most mysterious phenomena in planetary astronomy.
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Some observers have reported seeing a faint glow on the dark side of Venus, the side not
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directly illuminated by the sun.
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No one knows what causes it or if it's even real.
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Unlike Earth's shine, where sunlight reflects off of Earth to softly illuminate the moon's
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surface, Venus has no nearby celestial body to provide this kind of light.
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Yet for centuries, astronomers have claimed to see a dim glow on Venus' shadowed side.
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There are several unconfirmed theories.
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One possibility is air glow, a faint emission of light from chemical reactions in Venus'
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dense atmosphere, similar to Earth's auroras.
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Another idea is lightning.
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Some researchers suspect that massive electrical storms could be producing the glow, but so
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far we haven't detected lightning on Venus.
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Other theories suggest volcanic activity where glowing lava or atmospheric reactions might
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illuminate the planet's dark side.
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Some believe it's simply an optical illusion caused by the bright crescent of Venus tricking
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the human eye.
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And there's the idea of scattered sunlight where Venus' thick cloud cover might be redirecting
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light in unexpected ways.
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It's not easy to spot the ash and light, but if you want to try, you'll need the right
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conditions.
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The best time to observe it is when Venus is in its crescent phase, just before or after
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new Venus.
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That's when the dark side is most visible.
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To have the best chance, use a high-quality telescope, at least 4-6 inches in aperture,
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and try observing from a very dark location.
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Using averted vision, where you look slightly off to the side instead of directly at Venus,
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can sometimes make faint details more noticeable.
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And if you're into astrophotography, long exposure images and stacking techniques might
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reveal something your eyes can't.
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The ash and light has been reported as far back as the 1600s and even famous astronomers
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like Sir William Herschel claim to have seen it.
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Most recently, NASA's Parker Solar Probe, which made a series of flybys of Venus, seemed
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to confirm a glow in the visible spectrum.
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In the near-infrared spectrum, Venus's hot surface glows like iron pulled from a forge.
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Its thought some of this glow also creeps into the visible spectrum, and if cloud cover
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is translucent, perhaps we can see some of that surface glow.
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Whatever the answer may be, the ash and light remains one of the great unsolved mysteries
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of Venus.
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If you ever manage to catch a glimpse of it, you'll be joining a long history of observers
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trying to unlock one of the solar system's greatest secrets.
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A lone spacecraft drifts through the void, further from Earth than any human-made object
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has ever traveled.
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It carries no crew, no passengers, except perhaps a message.
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A golden disk designed to last a billion years, etched with the sounds and sights of an entire
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planet.
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This artifact is the Voyager Golden Record, humanity's time capsule for the universe.
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We know full well that our planet and all its inhabitants are about a small part of this
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immense universe that surrounds us, and it is with humility and hope that we take this
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step.
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We'll take a look at the science, technology, and ingenuity that went into crafting this
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interstellar greeting.
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But to understand why the Golden Record exists, we have to start with the spacecraft carrying
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it, Voyager 1 and 2.
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In the early 1970s, NASA was preparing for one of the most ambitious missions in history.
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The space probes Voyager 1 and 2 were designed to explore the outer planets of the solar
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system, using a rare planetary alignment that occurs only once every 175 years.
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But as these robotic explorers were being prepared for launch, a small team of scientists
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and visionaries saw an even greater opportunity to attach a message for any future finders
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of the spacecraft.
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The idea of sending an interstellar message wasn't new.
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Pioneer 10 and 11 launched in 1972 and 1973 carried a small engraved plaque designed by
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Carl Sagan and Frank Drake, which depicted the location of Earth and a basic representation
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of humans.
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But the team wanted something more sophisticated for the Voyagers, something that could convey
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sights, sounds, and emotions from our world.
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The idea for the Golden Record was championed by Sagan, an astrophysicist, planetary scientist,
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and one of the greatest science communicators of his time.
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He believed deeply in the idea of sending a message to the stars, not because he thought
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aliens were likely to find it, but because it was a powerful symbol of human curiosity
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and optimism.
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Here's Sagan in his own words, describing the project.
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Voyager's passage by Jupiter accelerated it towards a close encounter with the planet
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Saturn.
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Saturn's gravity will propel it onto Uranus.
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And in this game of cosmic billiards after Uranus, it will plunge on past Neptune, leaving
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the solar system and becoming an interstellar spacecraft, destined to wander forever, the
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great ocean between the stars.
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And a Voyager should sometime in its distant future encounter beings from some other civilization
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in space.
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It bears a message, a phonograph, golden, delicate, with instructions for use.
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And on this record are a sampling of pictures, sounds, greetings, and an hour and a half
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of exquisite music.
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The Earth's greatest hits.
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A gift across the cosmic ocean from one island of civilization to another.
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And NASA approved the idea, but Sagan and his team had just six weeks to design the record
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and near impossible deadline for a project of this scope.
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Members of Sagan's team for this undertaking again included Frank Drake, famous for the
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Drake equation, which estimates the probability of extraterrestrial life in the universe.
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Andruyan later, Sagan's wife, served as creative director of the project.
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She selected much of the music and sounds.
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Timothy Ferris, a science writer and journalist, produced the final version of the audio recordings.
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Artist and designer John Lomburg helped curate the images.
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And Linda Sagan, Carl Sagan's then wife, worked on the spoken greetings and messages.
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The team's mission was straightforward, represent all of humanity.
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Sagan and his team wanted the record to be a true reflection of Earth's cultures and
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civilizations.
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This meant including not just Western music and languages, but a broad range of human
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diversity.
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And it wasn't limited to sounds.
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Using the technology of the time, a selection of images were encoded in the message.
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We'll talk more about how that was accomplished in a moment.
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How do you even begin to decide what to include?
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With only six weeks, the team had to make incredibly difficult choices.
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Here's what made it onto the final record.
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Sounds of Earth.
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These included natural sounds like wind, rain, ocean waves, thunder and fire.
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Animal calls like whale song, birds and elephants.
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Human sounds such as footsteps, laughter, a baby crying and a kiss.
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There are also spoken greetings in 55 languages ranging from English to ancient Sumerian.
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And this iconic greeting.
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Hello from the children of planet Earth.
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There's also a 90 minute playlist of global music, including examples of Western classical
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music.
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Traditional drumming from West Africa.
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Indigenous music such as these Peruvian pan pipes.
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And even modern American music, Louis Armstrong.
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Blind Willie Johnson.
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And Chuck Berry's Johnny B. Good, which Sagan notably had to fight to get included.
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A total of 116 color and black and white images were also included, ranging from illustrations
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of mathematical concepts to photos of humanity and nature.
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The first images on the record are scientific, simple binary numbers, chemical structures
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and mathematical relationships.
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And diagrams of DNA and human anatomy, the physics of gravity and planetary orbits.
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The human experience is represented by a mother nursing a child, a bustling city street, the
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Olympic sprinter Carl Lewis and Midge Stride, and finally Earth itself, forests, mountains,
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Great Wall of China and Taj Mahal.
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NASA knew that if Voyager continued its journey for millennia, it might one day be discovered
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by another civilization.
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But why a record?
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In 1977, this was still the preferred format for audio and music.
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Digital storage was still in its infancy when Voyager launched.
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Magnetic tape degraded quickly, hard drives were bulky and fragile.
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But a gold-plated copper record could last for millions, possibly even billions of years
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in space.
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Unlike digital formats, a record doesn't require special software to decode.
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Any intelligent species with an understanding of sound waves could reconstruct the information,
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just like we decode hieroglyphics or cuneiform tablets.
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Constructing a record player is remarkably simple.
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I think I learned this from Mr. Wizard's World when I was a kid, but I once rolled
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up a piece of construction paper into a cone shape and taped a sewing needle to the point
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of the cone.
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By placing this needle on a spinning record, I was able to hear some fairly tinny but recognizable
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sounds coming out of my paper speaker.
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And by the way, I wouldn't recommend doing this on a vinyl record nowadays because you'll
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likely damage it.
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The gold record isn't quite that fragile.
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It was made of gold-plated copper.
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Gold was chosen because it's highly resistant to corrosion.
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The record was designed to be played at about half the speed of a traditional LP at around
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16 revolutions per minute.
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This allows for a longer playtime.
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A pictorial cover provides instructions on how to decode the record and this cover is
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etched with a map designed by Frank Drake of known pulsars to show where Earth is located.
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A small amount of uranium is also embedded in the case, allowing an advanced civilization
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to determine the record's age using radioactive decay.
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The record also came with its own cartridge and needle, although the aliens would need
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to figure out a way to amplify the electrical signal generated by its stylus because speakers
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weren't included.
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So how are the images stored on the record?
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In 1977, there was no JPEG, PNG, or any sort of digital compression.
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Instead, NASA used an ingenious method, analog frequency modulation, which is similar to
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how early slow-scan television worked.
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That's what an encoded image sounds like.
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This image was scanned line by line, converting brightness levels into modulated frequencies.
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Dark areas have lower frequencies, bright areas have higher ones.
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The result is a sound that, when decoded properly, reveals a picture.
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The images are stored at 512 lines per picture, which is roughly the resolution of an early
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black-and-white television.
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The included color images required more processing.
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Instead of a single image, they were stored as three separate grayscale layers, red, green,
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and blue, which could be reconstructed into a full image.
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My ham radio brethren have likely heard of slow-scan TV.
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It's an antiquated but charming way to send images over radio waves.
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The amateur station on the International Space Station occasionally transmits images
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in this manner.
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In fact, they are scheduled to send slow-scan TV this week in celebration of World Radio
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Day.
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So if you have a receiver, try tuning in.
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The images on the Golden Record are encoded using a unique scheme that isn't compatible
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with any existing slow-scan TV standards.
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So assuming an alien species happened upon the record and recognized the structured modulation
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as data, they'd need to develop their own methodology for translating those sounds into
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images.
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If you're savvy with audio and programming, you can download the original audio and decode
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the images yourself.
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Fortunately, NASA maintains an archive of the original images so they're easily viewable
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online.
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I'll include links in the show notes.
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Sagan documented the process of creating the Golden Record in the 1978 book, Murmurs of
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Earth, the Voyager Interstellar Record.
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It's worth checking out if you want to learn more about how the record was created.
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To quote Sagan, the launching of this bottle into the cosmic ocean says something very
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hopeful about life on this planet.
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That message in a bottle is still adrift.
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After completing their planetary missions to study the gas giants, both voyagers continued
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outward.
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Today, they are in interstellar space beyond the influence of our sun's solar wind.
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At this moment, Voyager 1 is more than 15 billion miles from Earth.
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It takes radio signals more than 22 hours to reach it.
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If you recall our discussion of the scale of the cosmos from last week's episode, you'll
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know that space is an incredibly empty place.
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The chances of either Voyager encountering anything or anyone in their journey is slim
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but not impossible.
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Voyager 1 will pass within 1.6 light years of the star Glease 445 in about 40,000 years.
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If a civilization exists there, perhaps they'll detect it and hear the echoes of our distant
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Earth.
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If you enjoyed this episode, let me know.
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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, and you can find transcripts
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of every episode.
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You can find this on Blue Sky and Mastodon, and if you'd like to support the show by
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buying me a cup of coffee, be sure to visit the links in the show notes and on the website.
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Until next time, keep looking up and exploring the night sky.
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Dear Sky's Everyone!