Starship Asterisk*

Fred the Cat wrote: ↑Thu Nov 14, 2019 12:52 am
Like watching an exoplanet’s transit very close-up.

What could we glean?

Transits have and should yield very interesting science in the future.

Chris Peterson wrote: ↑Wed Nov 13, 2019 5:28 pm

aildoux wrote: ↑Wed Nov 13, 2019 5:10 pm Oh, thank you. Did not see that a Wiki page existed on the subject. Future astronauts on Mars (if there by 2084) should bring a small telescope with sun filter to see that. Presently, I presume that robots and satellites on and around Mars cannot point and zoom in at the sun without damage.

Curiosity imaged a Mercury transit from Mars in 2014.
_

NASA/JPL-Caltech/MSSS/Texas A&M

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aildoux wrote: ↑Wed Nov 13, 2019 5:10 pm Oh, thank you. Did not see that a Wiki page existed on the subject. Future astronauts on Mars (if there by 2084) should bring a small telescope with sun filter to see that. Presently, I presume that robots and satellites on and around Mars cannot point and zoom in at the sun without damage.

SteveMiall wrote: ↑Wed Nov 13, 2019 3:56 pm When I look at the sun, just behind Mercury, it looks like the convection cells form a circle around the image of Mercury. Is anyone else seeing this effect? Is it real, or computer-generated?

aildoux wrote: ↑Wed Nov 13, 2019 12:44 pm
I wonder... could a transit of our planet Earth be seen from planet Mars ?

https://en.wikipedia.org/wiki/Transit_of_Earth_from_Mars wrote:

The next possible Earth and Moon transit of the Sun in 2084, as seen from Mars. Image created using JPL Solar System Simulator

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<<A transit of Earth across the Sun as seen from Mars takes place when the planet Earth passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars. During a transit, Earth would be visible from Mars as a small black disc moving across the face of the Sun. During the event, the Moon could almost always also be seen in transit [at ~63% the relative Mercury to Sun transit size as seen in today's APOD], although due to the distance between Earth and Moon, sometimes one body completes the transit before the other begins (this last occurred in the 1800 transit, and will happen again in 2394).

No one has ever seen a transit of Earth from Mars, but the next transit will take place on November 10, 2084. The last such transit took place on May 11, 1984. A [Chesley Bonestell illustrated] science fiction short story published in 1971 by Arthur C. Clarke, called "Transit of Earth", depicts a doomed astronaut on Mars observing the transit in 1984. This short story was first published in the January 1971 issue of Playboy magazine.

A transit of Earth from Mars corresponds to Mars being perfectly uniformly illuminated at opposition from Earth, its phase being 180.0° without any defect of illumination. During the 1879 event, this permitted Charles Augustus Young to attempt a careful measurement of the oblateness (polar compression) of Mars. He obtained the value 1/219, or 0.0046. This is close to the modern value of 1/154 (many sources will cite somewhat different values, such as 1/193, because even a difference of only a couple of kilometers in the values of Mars' polar and equatorial radii gives a considerably different result).>>