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The Mid-October Sky and The House of a Thousand Mirrors · Star Trails: From Backyard Astronomy to Cosmic Wonder

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  Howdy Star Gazers and welcome to Star Trails.
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  I'm Drew and I'll be your guide to the night
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  sky for the week of October the 12th to the 18th.
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  This week we're moving deeper into autumn and
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  the sky is shifting gears. Longer nights, crisp
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  air, and the fading moon are about to make for
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  some excellent observing conditions. Also, we
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  continue our march toward Halloween with another
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  eerie observation. This week we journey into
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  the house of a thousand mirrors to examine one
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  of my favorite topics, the weird world of gravitational
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  lensing. Whether you're tuning in from the backyard,
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  the balcony, or just your imagination, I'm glad
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  you're here. So find a cozy spot, let your eyes
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  adjust, and let's see what the sky holds for
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  us this week. The week begins with a waning gibbous
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  moon just past full. On Monday the moon reaches
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  last quarter and thins into a waning crescent
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  rising later each night. That means the second
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  half of the week will bring darker skies in the
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  late evening perfect for galaxies, nebula and
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  faint star clusters. The planetary lineup is
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  solid this week. Saturn takes the spotlight right
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  after dusk. It's hanging in Aquarius, high enough
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  for steady views by mid -evening. It passed opposition
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  back in September, so it's still bright and its
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  moon Titan is easy to spot even in a modest telescope.
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  Neptune is over in Pisces, best seen around midnight.
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  Look for it as a tiny bluish dot in binoculars.
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  Uranus rises later in the evening in Aries, steadily
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  climbing toward its November opposition. Under
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  suburban skies, it's easy to catch with binoculars
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  and shows a small greenish disk in a telescope.
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  Jupiter doesn't make its entrance until the early
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  morning hours, but when it does, it dominates
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  the sky. It's rising earlier each night and will
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  reach opposition in January. So this is the beginning
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  of its best observing season. And don't miss
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  Venus now reemerging as a brilliant morning star
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  in the pre -dawn sky. By week's end, you'll see
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  it low in the east with a delicate crescent moon
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  nearby. An excellent photo opportunity if you
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  have a clear horizon. Mars and Mercury are low
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  and tricky this week. Mars is fading into the
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  twilight. and Mercury will become more visible
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  later in the month. The Orionid meteor shower,
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  made of dust from Halley's Comet, is ramping
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  up. The official peak is on October 21st, but
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  during our week, early Orionids are already visible.
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  For your best chance, head out after midnight,
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  face east, and watch as Orion climbs higher in
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  the sky. Late in the week, the dimming moon will
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  make it easier to spot them. Constellations of
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  autumn are rising. We mentioned the great square
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  of Pegasus last week, and how to locate the Andromeda
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  galaxy. If you revisit that same area, look for
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  M33, the Triangulum galaxy, a faint but rewarding
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  catch. And while you're in Pegasus, don't miss
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  M15, a bright, compact globular cluster that
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  looks great even under moderate light pollution.
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  Overhead at dusk, Cygnus is still well placed,
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  its Milky Way lanes glowing faintly in darker
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  skies. A telescope with a nebula filter can reveal
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  the Veil Nebula or the North America Nebula,
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  especially during the moon -free later part of
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  the week. Down south near Saturn, swing your
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  scope to M2 in Aquarius, a fine globular cluster,
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  and the Helix Nebula, a ghostly planetary nebula
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  that really pops with an O3 or UHC filter. And
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  if you're up late or early, you'll see Taurus
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  rising in the east. The Hyades and Pleiades star
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  clusters sparkle in the pre -dawn sky, signaling
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  that winter constellations are on their way.
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  And don't forget to check NASA's Spot the Station
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  app for ISS flyovers. A bright pass can add a
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  little unexpected excitement to your observing
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  session. In a moment, we'll step into a place
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  where light bends, time folds, and a single galaxy
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  can appear a dozen times over. We'll explore
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  the House of a Thousand Mirrors, where gravity
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  itself builds a cosmic funhouse. That's coming
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  up after the break. Stay with us. Welcome back.
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  Imagine drifting alone through intergalactic
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  space, no stars, no planets, no sound, just the
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  faint cold light of distant galaxies. Then there
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  it is, a single quasar, bright and sharp, and
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  another, and another, and another. The same object
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  repeated again and again, hanging in the void
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  like reflections in a hallway of mirrors. What
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  you're seeing isn't a trick of your eyes. It
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  isn't a glitch in your telescope. It's the universe
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  itself bending light into impossible shapes.
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  Welcome to what I call the cosmic version of
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  the house of a thousand mirrors. This strange
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  funhouse is built by gravity, more specifically
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  gravitational lensing, one of the most breathtaking
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  predictions of Einstein's general theory of relativity.
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  Einstein showed that massive objects, stars,
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  galaxies, star clusters, don't just sit in space,
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  they curve space -time itself. Light, always
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  following the straightest possible path, bends
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  along those curves like a car following a winding
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  mountain road. Picture a glass marble placed
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  on a stretched rubber sheet. Roll a bead of light
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  nearby and it veers off course. Now, scale that
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  up to a galaxy weighing trillions of suns. The
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  result is a natural lens, an effect that can
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  resemble a funhouse mirror. There are different
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  kinds of gravitational lensing. Strong lensing
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  is the funhouse variety, the one that splits
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  a single object into multiple distinct images.
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  These are the mirrors you can actually see. Weak
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  lensing is subtle, like a warped reflection in
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  an old window. Astronomers use it statistically
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  to map the invisible skeleton of the universe.
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  And micro -lensing happens when stars briefly
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  magnify distant objects like flickering lanterns
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  in the dark. But for our purposes tonight, it's
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  strong lensing that turns the universe into something
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  eerie. A place where a single object can appear
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  dozens of times, scattered across the sky like
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  a shattered reflection. One of the most famous
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  examples is the Einstein Cross, a quasar billions
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  of light years away, whose light is split into
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  four identical points arranged neatly around
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  a foreground galaxy. It looks like a cosmic emblem.
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  Then there's Abell 1689, a massive galaxy cluster
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  that bends light so dramatically it produces
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  arcs, rings, and multiple mirror images of galaxies
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  hiding far behind it. If you've ever seen those
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  long ghostly arcs and Hubble images, that's Abell
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  1689 at work. Perhaps the most astonishing example
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  is Max J1149. In 2014, astronomers witnessed
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  the explosion of a distant supernova named Refsdal.
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  Then, a year later, they saw it again. The light
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  had traveled through different routes in the
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  warped space -time of a galaxy cluster. One path
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  was shorter, one was longer. It was the same
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  explosion appearing twice. This is time itself,
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  folded by gravity. In an actual hall of mirrors,
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  light bounces from surface to surface, arriving
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  at your eyes at different moments. Gravitational
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  lensing works in a similar way, but the mirrors
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  aren't made of glass. They're made of space -time.
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  Light from a distant quasar might arrive at Earth
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  by multiple routes, some taking longer than others.
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  It's kind of like watching the same film twice,
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  but from different theater seats. This cosmic
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  rerun is eerie, but it's also incredibly useful
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  to astronomers. By carefully measuring the time
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  delays between these mirror images, astronomers
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  can calculate the expansion rate of the universe.
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  That's the Hubble constant. And interestingly,
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  these lensing -based measurements don't quite
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  match other methods, hinting at something strange
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  about our cosmos. Gravitational lensing also
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  has another use. It reveals the distribution
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  of dark matter, the invisible mass that shapes
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  the universe. It helps us discover galaxies too
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  distant and faint to detect otherwise. The lens
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  acts like a magnifying glass, boosting their
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  light. The James Webb Space Telescope is already
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  peering through these natural telescopes to find
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  some of the earliest galaxies after the Big Bang.
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  For backyard astronomers, strong lensing is challenging
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  to spot directly, but not impossible. With a
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  large enough telescope under dark skies, the
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  arcs of able clusters can be teased out. More
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  accessible, though, are the iconic images captured
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  by Hubble and the James Webb. The Einstein cross,
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  the frontier fields, the incredible deep field
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  mosaics are all freely available online. The
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  next time you look at one, take a moment to ponder.
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  Every arc, every ghostly streak is the distorted
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  light of a galaxy billions of years old, seen
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  through another galaxy's gravity. You're looking
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  into a cosmic mirror maze built by mass itself.
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  These lenses in space replay the past and reveal
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  the secrets hidden at the edge of time. If the
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  stars spoke to you this week or if a question's
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  been on your mind, I'd love to hear it. Visit
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  our website StarTrails .Show where you can contact
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  me and explore past episodes. Be sure to follow
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  us on Blue Sky and YouTube. Links are in the
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  show notes. Until we meet again beneath the stars,
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  clear skies everyone.