# How can we take pictures of Earth-like exoplanets? Use the sun!

#### Helio

Wow, I wouldn't have guessed our semi-average sun could offer such magnification!

But is it really possible to track that fast moving target at that magnification? That too would be impressive.

But, according to my calculations for habitable zone qualifications (Planetary Biology), the planet is just about 2x too far to have liquid water. This does explain its estimated colder temperature, which is colder than Earth's temp.

It would be interesting if the tantrums that red dwarfs throw might somehow actually improve circumstances for the planet, somehow. [It is a little interesting to note that a 1.5 increase in magnitude would put it in the HZ, which may take place during flares.]

Catastrophe

#### rod

The article said, "One catch: That focal point, the location where we would need to place a telescope to take advantage of the solar gravitational lens, is about 550 astronomical units (AU) away. One AU is the average distance between Earth and the sun — about 93 million miles (150 million km), so that means the focal point would need to be 550 Earth-sun distances away. That's almost 20 times farther away than Pluto. Voyager 1, which has traveled farther from Earth than any other spacecraft, is currently about 40 AU from the sun."

Okay, this is some telescope operating at about 550 AU distance from Earth . Consider that a Jupiter size and diameter exoplanet is about 9.56 x 10^-4 AU diameter. A telescope that resolves to 1 arcsecond angular size, at 10 pc could see an object about 10 AU in diameter. Directly imaging an Earthlike exoplanet will take some work it seems

#### Helio

" One AU is the average distance between Earth and the sun — about 93 million miles (150 million km), so that means the focal point would need to be 550 Earth-sun distances away. That's almost 20 times farther away than Pluto. Voyager 1, which has traveled farther from Earth than any other spacecraft, is currently about 40 AU from the sun."
I missed that there was a few nits in the distances. 550AU is about 14x that of Pluto's distance, not 20.

Worse, Voyager passed Pluto's distance (~ 40 AU) a long time ago and is now about 126AU, if the site I used is current.

Okay, this is some telescope operating at about 550 AU distance from Earth . Consider that a Jupiter size and diameter exoplanet is about 9.56 x 10^-4 AU diameter. A telescope that resolves to 1 arcsecond angular size, at 10 pc could see an object about 10 AU in diameter. Directly imaging an Earthlike exoplanet will take some work it seems
At 2x10^11 magnification, as claimed, it would produce an apparent size for Proxima b to be 177 degrees! It would appear as if it was only 200 km distance (4x10^13km/200 billion)! It's apparent velocity would be a doozy!

Catastrophe

#### Pogo

I'm not so sure it'll make a very good image. From what I've seen, objects and gravity don't make a very good lens. Don't expect it to look like a telephoto image, but, we may gain some spectroscopic data from it.
Then once it gets on station, how do we lose the deltaV it needs to lose and how do we keep it on station. Not sure that a light sail at 550 AU will be very effective.

#### Catastrophe

##### "Science begets knowledge, opinion ignorance.
Light sails are suitable for moving around micrograms.

Cat

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