Why We Can Reach Pluto But Can’t Fly Above the Sun

Scientific concepts, discoveries, and nature phenomena

Orbital mechanics: velocity inherited from Earth

• Earth orbits the Sun at approximately 30 km/s, so a rocket launched from Earth already has a significant sideways (tangential) component of velocity.
• Reaching deep space is often easier than going “straight up” relative to the solar system’s (and a planet’s) orbital plane, because many missions already move in the correct general orbital direction.

Inefficiency of making a 90° “out of plane” turn

• Redirecting motion to go perpendicular to the planetary/orbital plane would require an additional ~42 km/s of delta-v.
• This exceeds what chemical rockets can practically provide.

Orbital inclination changes and the Oberth effect

• Oberth effect: burning while moving faster produces a larger change in orbital energy, which is useful for speeding up or slowing down.
• However, changing orbital inclination is more efficient when the spacecraft is moving more slowly.
• As a result, engineers often rely on gravity assists rather than only engine-based maneuvers.

Heliosphere and heliopause

• The Sun’s solar wind creates the heliosphere, which is bounded by the heliopause (its outer edge).
• The heliosphere shields much of the galactic cosmic rays; it is often described as a “giant protective bubble” (a magnetized cavity).

Shape of the heliosphere (updated models)

• Earlier intuitions likened the shape to a comet tail, but a 2020 model (using data from multiple spacecraft plus computer simulations) challenges that idea.
• Proposed shape: a “deflated croissant” rather than a long comet-like tail.

Oort Cloud (inner frontier beyond the heliosphere)

• The Oort Cloud is an extremely distant, spherically distributed reservoir of icy bodies.
• Identification idea (indirect):
  • In 1950, Jan Oort studied long-period comet orbits and inferred a near-spherical cloud far beyond the planets.
  • Because it is not directly visible, its existence is inferred from comet dynamics.
• Scale note (as stated): Voyager 2 would take hundreds to tens of thousands of years even to reach the inner edge / begin passing through the region discussed.

Perturbations by passing stars

• A described historical event: about 80,000 years ago, a wandering binary system (referred to as “Schultz’s star”) passed by and grazed the outer Oort Cloud.
• Disturbances may take millions of years to propagate inward toward the inner solar system.

Local interstellar cloud and the “local bubble”

• The solar system is traveling through a local interstellar medium region with slightly higher density than surrounding space.
• Larger context: the Local Bubble
  • Approximately 1,000 light-years wide
  • Very low gas density—described as a cavity in the interstellar medium

Origin of the Local Bubble: supernova feedback

• The bubble is attributed to clustered supernova explosions (multiple massive stars) starting roughly 14 million years ago (about 15 supernovae over several million years, as stated).
• Mechanism: supernovae push gas away, leaving a low-density interior with denser material forming the surrounding walls.

Evidence from Earth’s deep-sea sediments: Iron-60

• Researchers reported finding radioactive isotope Iron-60 (^60Fe) in deep-sea sediments.
• ^60Fe is produced largely in massive stars and released by supernovae / stellar winds.
• Reported fallout time windows:
  • roughly 2–3 million years ago
  • and 6–9 million years ago

Galactic structure above the Milky Way’s disk

• “Straight up” relative to the solar system/planetary plane does not map cleanly onto the Milky Way’s geometry.
• Mentioned features:
  • Stellar streams, e.g., the Sagittarius stream (debris from a dwarf galaxy tidally disrupted by the Milky Way)
  • Fermi bubbles
    • two large gamma-ray emitting regions
    • associated with very hot gas and high-energy particles
    • extent stated as ~25,000 light-years from the galactic center
  • Possible energy sources (a two-suspect scenario):
    • the central supermassive black hole Sagittarius A* (video spelled it as “Sagittarius AAR”)
    • or a period of intense star formation near the galactic center

Dark matter as the galaxy’s gravitational “glue”

• The Milky Way is held together by a large, invisible dark matter halo.
• Evidence types mentioned:
  • galaxy rotation behavior
  • motion of galaxy clusters
  • gravitational lensing (light bending due to unseen mass)
• Direct detection is not claimed here—only gravitational effects.

Actual “flying above the Sun”: Voyager/Ulysses example

• The video highlights Ulysses (launched 1990):
  • used a Jupiter gravity assist
  • achieved an orbit inclined about ~80° to the ecliptic/planetary plane
  • became the first probe to pass over the Sun’s northern and southern polar regions
• Limitation: Ulysses lacked a suitable camera for a “top-down solar system family portrait.”
• Even with a camera, the view would likely be dominated by the bright Sun, with planets appearing as tiny pixels unless heavily processed or stitched.

Solar Orbiter and growing view from above

• Solar Orbiter (expected to reach a vantage point in 2025, per the video) obtained a view about ~17° south of the solar equator.
• Planned progression: Venus gravity assists increase inclination further (to 24°, then up to ~33°; the video contained a garbled number like “333,” but the intent was increasing inclination).
• Scientific focus:
  • magnetic fields
  • solar wind
  • the solar magnetic-cycle behavior of polarity flips every ~11 years

No universal “up” in space (coordinate geometry / reference frames)

• “Up” depends on the chosen reference plane:
  • planetary/ecliptic plane
  • Milky Way disk plane
  • Earth’s orbital/cosmic frame
• Key point: there is no single universal up—moving “straight up” relative to one plane can mean moving diagonally through another structure, including the galactic disk.

How the solar system’s plane formed (origin of the “sideways” motion)

• About 4.6 billion years ago, the Sun and planets formed from a spinning cloud of gas and dust.
• Conservation of angular momentum and flattening processes formed a disk.
• Planets continued motion inherited from the primordial rotating material—explaining why Earth is “sideways” in its orbit rather than fixed.

Mission strategy: gravity assists and multi-year “hopping”

• Sharp out-of-plane changes are energy-expensive, so spacecraft “haggle with gravity”:
  • using planetary flybys (notably Jupiter and Venus, as mentioned)
  • transferring between orbits efficiently
  • squeezing performance from limited fuel due to rocket mass constraints

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Methods / sequences outlined

To reach space “above” the solar system (conceptual approach)

• Launch a rocket straight up relative to the planetary plane
• Attempt to cross boundaries outward:
  • the heliopause
  • the heliospheric region / interstellar medium (with the Oort Cloud extending through parts)
  • then the Milky Way’s halo / other galactic structures

How real missions change planes

• Instead of engine-only perpendicular launch:
  • use gravity assists (e.g., Jupiter for Ulysses)
  • plan multi-year trajectories to minimize required delta-v
  • exploit timing/geometry to influence orbital inclination

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Researchers or sources featured (named)

• Jan (Yan) Oort (1950) — inferred the Oort Cloud from long-period comet orbits
• Voyager 2 (spacecraft mission; referenced as an example)
• Ulysses (1990 spacecraft mission; gravity assist to study solar poles)
• Solar Orbiter (spacecraft mission; viewing progress toward solar polar/southern regions)
• Schultz’s star (described wandering binary system)
• Sagittarius A* (Milky Way’s central supermassive black hole; cited as a possible driver of the Fermi bubbles)