Starship Asterisk*

APOD Robot wrote: ↑Mon Oct 21, 2019 4:11 am
Explanation: The next transit of Mercury
will take place in three weeks: on 2019 November 11.

Ann wrote: ↑Mon Oct 21, 2019 4:34 am Anyway, today's APOD reminded me of this unforgettable scene from 2001: A Space Odyssey. Johann Strauss' An der schönen blauen Donau will surely never be the same!

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

Mercury transiting the Sun as viewed by the rover Curiosity on Mars

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Mercury Passes in Front of the Sun, as Seen From Mars

<<This animated blink comparison shows five different versions of observations that NASA's Curiosity made about one hour apart while Mercury was passing in front of the sun on June 3, 2014. This animated blink comparison shows five versions of observations that NASA's Curiosity made about one hour apart while Mercury was passing in front of the sun on June 3, 2014. Two sunspots, each about the diameter of Earth, also appear, moving much less than Mercury during the hour. June 10, 2014 NASA's Curiosity Mars rover has imaged the planet Mercury passing in front of the sun, visible as a faint darkening that moves across the face of the sun. This is the first transit of the sun by a planet observed from any planet other than Earth, and also the first imaging of Mercury from Mars. Mercury fills only about one-sixth of one pixel as seen from such great distance, so the darkening does not have a distinct shape, but its position follows Mercury's expected path based on orbital calculations. The observation by the telephoto camera of Curiosity's two-eyed Mast Camera instrument is available online. "This is a nod to the relevance of planetary transits to the history of astronomy on Earth," said Mark Lemmon of Texas A&M University, College Station, a member of the Mastcan science team. "Observations of Venus transits were used to measure the size of the solar system, and Mercury transits were used to measure the size of the sun." The observations were made on June 3, 2014, from Curiosity's position inside Gale Crater on Mars. In addition to showing the Mercury transit, the same Mastcam frames show two sunspots approximately the size of Earth. The sunspots move only at the pace of the sun's rotation, much slower than the movement of Mercury.

Mercury and Venus transits are visible more often from Mars than from Earth, and Mars also offers a vantage point for seeing Earth transits. The next of [transits] visible from Mars will be Mercury in April 2015, Venus in August 2030 and Earth in November 2084.>>

JohnD wrote: ↑Tue Oct 22, 2019 10:22 am It was abberations in the appearance of the Venusian disk, called the "Black Drop Effect", that led to significant differences in transit times recorded by Cook, the professional navigator and by Green, the professional astronomer, at Tahiti in 1769. Green died on the return voyage, which allowed British astronomers, not least the Astronomer Royal, to blame him, causing Cook dismay and to defned his dead colleague.

We no longer need to measure the transits to know planetary orbits, but how would the moment when the discs become tangent be defined today, when as the video clealry shows, prominences and other disturbances blur the Sun's edge?

neufer wrote: ↑Tue Oct 22, 2019 1:08 pm

JohnD wrote: ↑Tue Oct 22, 2019 10:22 am
We no longer need to measure the transits to know planetary orbits, but how would the moment when the discs become tangent be defined today, when as the video clealry shows, prominences and other disturbances blur the Sun's edge?

• Clealry it would not be possible without the efforts of all the women at NASA.

JohnD wrote: ↑Tue Oct 22, 2019 10:22 am
We no longer need to measure the transits to know planetary orbits, but how would the moment when the discs become tangent be defined today, when as the video clealry shows, prominences and other disturbances blur the Sun's edge?

• Clealry it would not be possible without the efforts of all the women at NASA.

stowaway wrote: ↑Mon Oct 21, 2019 7:07 pm This transit could not have happened without the efforts of all the women at NASA.

pferkul wrote: ↑Mon Oct 21, 2019 7:22 pm Why does the apparent shape of Mercury change as it transits? If we were looking at its shadow on the curved surface of the Sun then it would make sense. However as a back-lit object, it is unclear to me why Mercury should appear to have a changing elliptic outline. See attached image analysis from three frames.

MarkBour wrote: ↑Mon Oct 21, 2019 8:46 pm

orin stepanek wrote: ↑Mon Oct 21, 2019 10:42 am
Sol is a small star; yet the transit kind of gives one the impression of how massive the sun is in relation to the planet Mercury!

Oops; I see another black spot! Am I pointing to a sun spot instead of Mercury? Anyway one of them is Mercury!

Yep, your second thought is correct. So it's even more impressive. Mercury is the tiny speck.

• Better Call Sol.

orin stepanek wrote: ↑Mon Oct 21, 2019 10:42 am 450px-Mercury_transit_2.jpgSol is a small star; yet the transit kind of gives one the impression of how massive the sun is in relation to the planet Mercury!

Oops; I see another black spot! Am I pointing to a sun spot instead of Mercury? Anyway one of them is Mercury!

orin stepanek wrote: ↑Mon Oct 21, 2019 3:33 pm

neufer wrote: ↑Mon Oct 21, 2019 2:25 pm

TheZuke! wrote: ↑Mon Oct 21, 2019 2:01 pm
I was a little disappointed that the music wasn't "King of Pain" by The Police. B^)

• "KoP" by The Police... oh please!

+1;

neufer wrote: ↑Mon Oct 21, 2019 2:25 pm

TheZuke! wrote: ↑Mon Oct 21, 2019 2:01 pm
I was a little disappointed that the music wasn't "King of Pain" by The Police. B^)

• "KoP" by The Police... oh please!

TheZuke! wrote: ↑Mon Oct 21, 2019 2:01 pm
I was a little disappointed that the music wasn't "King of Pain" by The Police. B^)

• "KoP" by The Police... oh please!

Ann wrote: ↑Mon Oct 21, 2019 4:34 am
Interesting. Mercury moves so fast. The sunspots, by contrast, seem stationary.

• 1) planets transit in a matter of hours
  2) starspots transit in a matter of days

FrankTKO wrote: ↑Mon Oct 21, 2019 12:27 pm
Why is it "rare"? I would think every orbit that Mercury did would place it between us and the sun? More than once a year?

Ann wrote: ↑Mon Oct 21, 2019 4:34 am

Click to play embedded YouTube video.

Interesting. Mercury moves so fast. The sunspots, by contrast, seem stationary.

Anyway, today's APOD reminded me of this unforgettable scene from 2001: A Space Odyssey. Johann Strauss' An der schönen blauen Donau will surely never be the same!

Ann