What's Directly Above And Below The Sun? — Transcript

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1. 0:00What's Directly Above and Below the Sun? Spacecraft have reached every planet in the solar
2. 0:05system. Rovers are driving across Mars right now.  A probe was dropped through the clouds of Saturn,
3. 0:10and Pluto was photographed from less than 8,000  miles away. Crossing billions of miles of empty
4. 0:16space has started to feel almost routine. But there is one direction we have barely
5. 0:21touched. One place that should be the easiest to  reach, and turns out to be one of the hardest.
6. 0:27Straight up. Out of the flat plane the  planets all share, directly above or below
7. 0:32the sun. The vertical exit from our solar system. It sounds simple. Just point the rocket up and
8. 0:38go. The problem is that physics will not let you. What follows is why escaping vertically is harder
9. 0:45than going to Pluto. You will see what waits  up there if a spacecraft ever makes the trip,
10. 0:51and you will see the strange maneuver  scientists are now considering. A maneuver
11. 0:56where a probe has to first fall toward the  sun before it can ever climb away from it.
12. 1:03Act 1: The prison of orbital velocity To understand why vertical escape is hard,
13. 1:05you have to understand what speed you  already have, without doing anything.
14. 1:10The Earth is moving. Right now. Around the sun  at roughly 30 kilometers per second, or about
15. 1:1567,000 miles per hour. That is not a typo.  Every second, the planet you are standing on
16. 1:22travels 30 kilometers sideways around the sun. Every rocket we launch from Earth inherits
17. 1:28that motion. When SpaceX or NASA puts a probe in  space, the probe is not starting from rest. It is
18. 1:35already moving sideways at 30 kilometers  per second, the same as the rest of us.
19. 1:40This is normally a gift. If we want to  reach Mars, the existing sideways motion
20. 1:44does most of the work. We just have to adjust  slightly. A few kilometers per second of extra
21. 1:50velocity in the right direction, and we  are on a trajectory to another planet.
22. 1:55But what happens when you want to  go up? Not toward Mars or Jupiter
23. 1:59or anywhere else in the plane. Straight  up, perpendicular to everything else.
24. 2:06Now that sideways motion becomes your enemy.  To go straight up, you first have to cancel
25. 2:11out the 30 kilometers per second you already  have. Then you have to add new velocity to
26. 2:16climb. The total energy required is staggering. Mission planners measure this in something called
27. 2:22delta-v, the change in velocity a spacecraft  has to produce on its own. Going to Mars from
28. 2:29Earth orbit needs about 4 kilometers  per second of delta-v. Going straight
29. 2:33up out of the ecliptic plane needs roughly 30  kilometers per second. Almost ten times as much.
30. 2:40That is the prison. Earth's orbital motion  gives us free speed in one direction and
31. 2:45effectively walls us in. We can go around the  sun easily. We can hop to other planets in the
32. 2:51same plane easily. But the moment we try to  leave the plane itself, we have to fight 4.6
33. 2:56billion years of orbital momentum, all at once. It is one of the most counterintuitive facts
34. 3:03in astrodynamics. Reaching Pluto, three and a  half billion miles away, requires less energy
35. 3:08than reaching a point just a few million  miles directly above the sun's north pole.
36. 3:14Act 2: The mystery of the solar poles Because the vertical exit is so expensive, almost
37. 3:16no spacecraft has ever made the trip. Which means  almost everything that happens directly above
38. 3:21or below the sun is still, in 2026, a frontier. We have detailed maps of Mars and high-resolution
39. 3:28photographs of Pluto. We can show you  close-up imagery of comets, asteroids,
40. 3:33the rings of Saturn, and the moons of  Jupiter. But the poles of our own sun,
41. 3:38the closest star to Earth, have barely been seen. There is a reason this matters more than it
42. 3:43sounds. The polar regions of the sun are where  the most violent and most important solar activity
43. 3:48actually happens. The fastest solar winds come  from there. The magnetic field of the sun reverses
44. 3:54itself every 11 years through processes that  begin at the poles. The entire space weather
45. 4:00environment of our solar system is shaped by what  happens above and below the equator of our star.
46. 4:08And we have been observing it almost  entirely from the side. Like trying to
47. 4:12understand the weather of an entire planet  by only ever standing at the equator.
48. 4:17There have only been two missions that ever  managed a real polar view of the sun. The first
49. 4:21was Ulysses, launched in 1990 by a joint NASA and  ESA partnership. To get out of the ecliptic plane,
50. 4:28Ulysses had to take a wild detour. The spacecraft  first traveled outward to Jupiter, and then used
51. 4:35the gas giant's gravity as a slingshot to  bend its trajectory nearly 80 degrees out of
52. 4:40the planetary plane. From there it fell back  inward toward the sun on a tilted orbit. The
53. 4:47mission worked. Ulysses gave us our first direct  measurements of the fast solar wind streaming from
54. 4:52the polar coronal holes. But the spacecraft was  built with 1980s instruments. It had no cameras
55. 4:58capable of imaging the poles. We learned about  the conditions there, but never actually saw them.
56. 5:04The second mission is happening right now. Solar  Orbiter, a European Space Agency probe launched
57. 5:09in 2020, has been gradually tilting its orbit  using gravity assists from Venus. In March 2025,
58. 5:16Solar Orbiter sent back the first direct  images of the sun's south pole ever taken
59. 5:21in human history. The pictures show a chaotic,  magnetically tangled region nothing like the
60. 5:27smoother solar surface we see from Earth. Think about that. Until last year,
61. 5:33no human or robot had ever seen what the  top or bottom of our sun looks like. Not
62. 5:38really. Not from above. The closest and  brightest object in our local universe,
63. 5:43and arguably the most important, still has two  regions we have only just begun to photograph.
64. 5:49Act 3: The shape of our bubble There is a second reason vertical
65. 5:51escape matters. We do not actually know what  our own solar system looks like from outside.
66. 5:57Around the sun there is a vast bubble called  the heliosphere. It is the region of space
67. 6:02where the solar wind dominates, pushing  back against the interstellar medium
68. 6:06beyond it. Inside this bubble live  the planets and the comets and every
69. 6:11human spacecraft we have ever launched.  Outside, the deep galactic environment,
70. 6:15full of cosmic rays and interstellar  particles that our bubble shields us from.
71. 6:20For decades we assumed the heliosphere was shaped  like a comet. A rounded front, where it pushes
72. 6:26against the interstellar wind in the direction  of our galactic motion, and a long tail trailing
73. 6:31behind. This was the standard textbook image.  It was a good guess, given the data we had.
74. 6:37In 2020, a team led by Merav Opher at Boston  University, using a new model based on NASA data,
75. 6:44came to a different conclusion. The heliosphere  is probably not comet-shaped at all. The new
76. 6:50prediction looks closer to a deflated croissant.  A curved central bulge with two short jets curling
77. 6:56away from it, and notably no long tail. The reason we cannot tell for certain is
78. 7:02that we have never seen our bubble from  outside, and we have never sent a probe
79. 7:06high above the ecliptic plane far enough to  take its measurements from a useful angle.
80. 7:11The Voyager spacecraft crossed the heliopause  sideways, almost in the plane of the planets.
81. 7:16Useful, but limited. To actually understand the  shape of our home in the galaxy, we would need a
82. 7:21probe traveling well out of the ecliptic,  looking down at the structure from above.
83. 7:26There is a NASA mission called IMAP, the  Interstellar Mapping and Acceleration Probe,
84. 7:31designed to refine our understanding from  the inside. But for a direct view of the
85. 7:35bubble's true shape, the only way is to escape  vertically and look back at it. A vantage no
86. 7:41spacecraft has ever reached, for a structure  we live inside without knowing its real form.
87. 7:47Act 4: To climb, you must first fall How do you actually solve the vertical
88. 7:48escape problem? You cannot just build  a bigger rocket. The energy required to
89. 7:52cancel Earth's orbital motion is too  large for any reasonable fuel load.
90. 7:57There is a counterintuitive solution that has been  discussed in mission design circles for years, and
91. 8:02it is starting to move from theory toward concrete  proposals. It is called the solar Oberth maneuver.
92. 8:09The idea works backwards from how rockets normally  fly. Instead of pointing your engines upward and
93. 8:15trying to climb, you do the opposite. You drop  your spacecraft toward the sun. You let it fall
94. 8:19inward, accelerating under solar gravity, until  at its closest approach it is moving at hundreds
95. 8:25of kilometers per second, possibly more than  100 kilometers per second at perihelion. Then,
96. 8:30at exactly that moment, you fire your engines. Why? Because of a principle Hermann Oberth wrote
97. 8:37down in 1929. A rocket burn is dramatically more  efficient when performed at high velocity in a
98. 8:43deep gravitational well. The same amount  of fuel gives you a much larger increase
99. 8:48in orbital energy at perihelion than it  would in empty space. By burning at the
100. 8:53closest possible approach to the sun, you get  a slingshot effect without the slingshot. The
101. 8:58fuel you carried up from Earth turns into far more  kinetic energy than it would have anywhere else.
102. 9:05After the burn, your spacecraft is moving so  fast, in such a useful direction, that you can
103. 9:10finally climb out of the plane and head straight  up toward the solar poles, or directly out of the
104. 9:15solar system. The dive becomes the launch pad. Solar sails are also part of the conversation.
105. 9:22Mission concepts like the proposed Solar Polar  Imager and the more recent High Inclination
106. 9:27Solar Mission rely on enormous reflective  sheets that use the pressure of sunlight
107. 9:31itself to slowly tilt a spacecraft's orbit. No  fuel. Just photons pushing on a thin metallic
108. 9:38film thousands of square meters across. Sails  can take years to spiral up to a polar orbit,
109. 9:44but they need no propellant, and the longer they  push, the higher the inclination they can reach.
110. 9:50Combine the two. A spacecraft that uses a solar  sail to spiral closer and closer to the sun,
111. 9:56then performs an Oberth maneuver at perihelion to  redirect itself vertically, then continues riding
112. 10:02the sail out into the polar regions. This is the  kind of mission architecture that astrodynamicists
113. 10:08now think could finally give us a clean view  of what lies directly above and below our star.
114. 10:15Act 5: What we would see from above If we ever pull this off,
115. 10:17what does a spacecraft actually  see from directly above the sun?
116. 10:22First, the view changes physically.  The ecliptic plane is dirty. Earth,
117. 10:27like every planet, swims through a thin haze of  dust left over from billions of years of comets,
118. 10:32asteroid collisions, and the slow grinding  of the solar system. You can actually see
119. 10:36this dust with your own eyes. On a very dark  night, just after sunset or before sunrise,
120. 10:42a faint pyramid of light called the zodiacal light  reaches up from the horizon. That glow is sunlight
121. 10:48reflecting off the dust in our local plane.  It is the inside of our solar system, lit up.
122. 10:53A spacecraft that climbs above the ecliptic would  rise out of this dust within months. The view
123. 10:58there is dramatically cleaner. Less scattered  light. Less background haze. The kind of place
124. 11:04where a telescope could detect faint signals that,  from inside the disc, are drowned out by the dust
125. 11:09around us. It would be one of the best possible  vantage points for an instrument looking for
126. 11:14signs of life around other stars. From the same  vantage, a different instrument could measure
127. 11:19the cosmic microwave background, or study the  structure of the galactic plane from outside it.
128. 11:26Second, the solar environment changes. Above  the equator of the sun, the slow solar wind,
129. 11:31around 400 kilometers per second of turbulent  plasma, gives way to something steadier. Above
130. 11:37the polar coronal holes there is a stream  of fast solar wind, between 700 and 800
131. 11:42kilometers per second of particles flowing outward  in a thinner, smoother current. A spacecraft
132. 11:48riding through this stream would experience a  fundamentally different radiation environment,
133. 11:52with implications for both the lifespan of its  electronics and the science it could perform.
134. 11:58And third, the bigger picture. From a vantage well  above the ecliptic, the solar system itself would
135. 12:04be visible as the disc it actually is. You would  see the planets in their flat ring around the sun,
136. 12:10with the dust hugging the plane and the  heliosphere wrapped around all of it,
137. 12:14in whatever real shape it happens to  have. We would be able to look down at
138. 12:19our own neighborhood for the first time, the  same way we look down at Earth from orbit.
139. 12:24We have never seen this view. Not a single human  or robot has ever sent back the photograph. Of
140. 12:30all the images we have managed to take of the  cosmos, the one looking down at our own solar
141. 12:34system from outside its plane is still missing. And you. If you had to design the first mission
142. 12:42to climb directly above the sun, would you  bet on a solar sail, the slow patient way,
143. 12:47or on an Oberth dive, the violent and  dramatic way? Tell us in the comments.
144. 12:53And if you want to know what is actually waiting  up there, in those unexplored regions directly
145. 12:58above and below the disc of our planets,  watch 'What Exists Above and Below Our
146. 13:03Solar System?' next. This video explained the  journey. That one shows you the destination.