Exoplanets. Theyāre just like regular planets but found
in other planetary systems besides our own. So far over 3,600 discoveries have been confirmed
since 1992. These fuzzy dots are a few examples of the
best direct images that weāve got and these are all gas giants like Jupiter. What we donāt have is a really good image
of an Earth like exoplanet. It may actually be possible to get an image
like this, but how we could do it may surprise you --we could use the sun as a lens. The sun is massive, to say the least, therefore
so is its gravitational effect which warps the very fabric of space itself. When incoming light from a hypothetical exoplanet
approaches the sun, its path is also warped. These curved light rays are brought into focus starting from about 550 astronomical units, away from the Sun. The effect of gravity on the deflection of
light is inversely proportional to its distance from the center of the sun. Approaching light rays further from the sun
are not curved as much as light rays closer to it so they come into focus past 550 AU,
which results in a focus line rather than a single focus point. This is the solar gravitational lens. If we take a 1 meter telescope - place it
at 650 AU away on the focus line - targeting an exoplanet 100 light years away - how much
magnification and resolving power do you think it will have? From a fuzzy dot to a slightly larger fuzzy
dot? Not even close. It could resolve details at the scale of 10
kilometers squared. Thatās like resolving the width of a single
human hair on the moon from Earth or an equivalent resolution like this image of Earth. If instead you targeted the closest exoplanet
to us, proxima b at about four and a quarter light years away, the resolution would be
even greaterāin the hundreds of meters scale. But there are not as many planetary systems
to choose from right next door to us relatively speaking. The sun, obviously, does not function exactly
like a conventional lens. The sunās gravitational force warps the
incoming light in addition to focusing it, resulting in a ring shape around the sun,
called an Einstein ring. Correcting this is a lot more work than a
de-warping filter in photoshop. Adding to the difficulty, we canāt resolve
the whole Einstein ring at once with just a 1 meter telescope either. If this same example exoplanet has an Earth
like diameter of around 12,700 km then that will result in an Einstein ring approximately
1.3 km thick. This animation isnāt to scale as the ring
would look more like this compared to the sun. But with those variables in mind, the area
of the focus line that our telescope needs to cover would be a cylinder with a diameter
of about 1.3 km. You would need a telescope thatās at least
that size to resolve the entirety of the Einstein ring in one picture. Thatās 260 times larger than the primary
mirror in the hubble telescope. Fortunately, you donāt need to resolve the
whole ring in just one picture. Our 1 meter telescope can image an area on
this example exoplanet 10 kilometers squared. So you can think of each picture it takes
as a single pixel. You can still resolve the whole ring, you
just need to assemble it pixel by pixel. The proposed goal is for a final image with
1000 by 1000 pixels. But thatāll take some times as that adds
up to a total of one million pictures. Before the imaging process can even begin,
something has to be done about the sun. The telescope needs to face the sun to image
the exoplanet but, unsurprisingly, its light would outshine the exoplanet. Since the Einstein ring is around and outside
the sun, an internal coronagraph can be used which blocks the sun and the brightest part
of the solar corona. There will still be some light from the corona
mixed in but not enough to completely overwhelm the exoplanetās light. For the coronagraph to be more effective the
telescope needs to be positioned further back on the focus line, thatās why we canāt
place the telescope right at 550 AU, but still not too far back as that could add years to
the mission timeline. A good compromise would be between 650 to
800 AU. When the telescope is further from the sun,
naturally it will appear smaller. The magnification of the exoplanet stays the
same but the Einstein ring is now at a greater distance from the sunās surface, so thereās
less coronal light to contend with. But how far away are these distances really? An astronomical unit, or AU, is the distance
from the Earth to the Sun. At its greatest distance from the sun, Pluto,
is almost 50 AU away. Voyager 1 is currently travelling through
interstellar space at 138 AU away from the sun; farther than any spacecraft has travelled. The telescope needs to be almost 5 times further
than that. That distance, while considerable, may not
be insurmountable. Hereās one possible, hypothetical scenario. Using the currently in development SLS rocket
as the launch vehicle, the spacecraft can get to Jupiter within six months. It can use a gravity assist at Jupiter, slingshotting
the spacecraft towards the sun. As it falls into the sunās gravity well,
within 5-7 solar radii its velocity dramatically increases. When the spacecraft reaches maximum velocity
through this maneuver, its rocket engines fire, adding to its acceleration and sending
it on a trajectory to the focus line. Travelling between 17-22 AU per year the spacecraft
can get to 650 AU in about 30 years in the most optimistic scenario. But no spacecraft has approached this close
to the sun before, so a fairly robust solar heat shield will have to be designed and employed
in order for the spacecraft to survive. Once there, the telescope has to move with
the focus line and within it as nothing in the universe is static. The exoplanet orbits its parent star while
also rotating around its axisāif not tidally locked to its own star. While the trajectory design can account for
much of this, a novel design for the spacecraft itself is still needed for it to move stably
within the focus line. One idea is to build a spacecraft with the
telescope on one end tethered to a counter weight at the other end using ion thrusters
for propulsion at this point. The telescope can be pulled in or extended
out along this tether to move within the focus line while maintaining a stabilized anchored
position. This enables the telescope to gather a sufficient
amount of images with less difficulty than keeping an untethered spacecraft stabilized. Using this method it should take around 3
months to finish the task. But the challenges donāt end there. Each image that the telescope takes is not
a neat slice of the full ring. Instead the telescope builds a rasterized
image, where each snapshot contributes more detail and magnification of a specific area
on the exoplanet. These images end up overlapping each other,
which can be considered a benefit as we wonāt need quite as many for the desired resolution. Next, a deconvolution algorithm will be needed
to fix the warped ring. While that may be a considerable challenge,
weāll have the variables we need to correct it; the position of the spacecraft; brightness
of each image at those positions and the optical properties of the solar gravitational lens. If we are able to overcome all of these technical
hurdles we will finally have our first high resolution image of an exoplanet. Using spectroscopy, we can analyze the light
from the exoplanet in more detail than ever before. Gases absorb and emit their own distinct wavelengths
of light. So when we analyze light from its atmosphere
weāll be able to accurately define its composition. Is the air breathable? Are there any telltale signs of life in the
atmosphere like methane for example? Suppose thereās actually intelligent life,
and they too have electricity. Well if itās night time and they turn on
the lights, weāll see them. But thereās more. Radio waves are just another wavelength of
light. If ET is broadcasting, those radio transmissions
will also be magnified, but not to the extent of visible light as the radio spectrum is
actually distorted by the interference of the sunās corona. While utilizing the Solar Gravitational lens
is a daunting technical challenge, it still may be achievable in the near future. In fact, NASAās Innovative Advanced Concepts
programs, or NIAC, recently accepted a proposal, lead by Dr. Slava Turyshev to further explore
this very concept. This video is based largely on his paper and
follow up discussions with him. If you want to know more you can find a link
to his paper in the description below as well as other relevant resources.
that was interesting to say the least, wonder why it has so little views.
This is some incredible work OP. I'll go out on a limb here and guess you're a fan of Second Thought, RealLifeLore, and Wendover Productions? I wouldn't be surprised anyway, your style reminds me of their work but you've managed to be even more thorough while keeping it understandable for laymen. I subscribed to their youtube channels early on and watched them grow from a few hundred to the millions they have today. I have no doubt your popularity is going to explode if you keep pumping out videos of this caliber.