APOD: Super Moon vs. Micro Moon (2016 Nov 13)

[APOD Robot]

Super Moon vs. Micro Moon

Explanation: What is so super about tomorrow's supermoon? Tomorrow, a full moon will occur that appears slightly larger and brighter than usual. The reason is that the Moon's fully illuminated phase occurs within a short time from perigee - when the Moon is its closest to the Earth in its elliptical orbit. Although the precise conditions that define a supermoon vary, tomorrow's supermoon will undoubtedly qualify because it will be the closest, largest, and brightest full moon in over 65 years. One reason supermoons are popular is because they are so easy to see -- just go outside and sunset and watch an impressive full moon rise! Since perigee actually occurs tomorrow morning, tonight's full moon, visible starting at sunset, should also be impressive. Pictured here, a supermoon from 2012 is compared to a micromoon -- when a full Moon occurs near the furthest part of the Moon's orbit -- so that it appears smaller and dimmer than usual. Given many definitions, at least one supermoon occurs each year, with another one coming next month (moon-th). However, a full moon will not come this close to Earth again until 2034.

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[CharlesE]

What is the distance to the Super Moon tomorrow, at closest approach? What I'm really asking is for the distance variation between a micro moon (or from the average moon distance) and the Super Moon tomorrow.

[Boomer12k]

The Energizer Bunny in Stereo....

Probably will rain, and not be able to see it...
Look forward to the pictures...

:---[===] *

[Case]

What is the distance to the Super Moon tomorrow, at closest approach? What I'm really asking is for the distance variation between a micro moon (or from the average moon distance) and the Super Moon tomorrow.

Universetoday: “The semi-major axis (average distance) is 384,403 km (238,857 miles). At its closest point (known as perigee) the Moon is only 363,104 km (225,622 miles) away. And at its most distant point (called apogee) the Moon gets to a distance of 406,696 km (252,088 miles).”

Wikipedia: “Perigee varies from 356,400–370,400 km (221,457–230,156 mi). Apogee varies from 404,000–406,700 km (251,034–252,712 mi).”

Timeanddate.com: “14 nov 06:20 EST - 356,509 km (221,524 mi)”

[heehaw]

I'm afraid I call it StuporMoon. Great illustration showing how small the real difference in SIZE is between biggest and smallest. The difference in brightness is considerably greater. But when you are looking at ANY full moon, you have nothing to compare it with. For purely human psychological reasons (not understood) any full moon looks much bigger near the horizon than it does high in the sky. That difference is much bigger (I think) than the real physical differences between micro- and super- moons. I'm afraid I'm sick and tired of all the silly supermoon-hysteria that we get so often.

[hamilton1]

For purely human psychological reasons (not understood) any full moon looks much bigger near the horizon than it does high in the sky.

About the moon illusion... is it not simply the case that when near the horizon the moonlight is refracted by passing through a greater quantity of atmosphere, and therefore appears bigger... although presumably the experts would have thought of that.

[CharlesE]

Case: Thank you. That is appreciated.

[Chris Peterson]

For purely human psychological reasons (not understood) any full moon looks much bigger near the horizon than it does high in the sky.

About the moon illusion... is it not simply the case that when near the horizon the moonlight is refracted by passing through a greater quantity of atmosphere, and therefore appears bigger... although presumably the experts would have thought of that.

No. Optically, the Moon can only be made to look smaller by atmospheric effects near the horizon- unchanged horizontally, compressed somewhat vertically.

(The Moon illusion isn't "not understood"; there are good explanations for how it works.)

[Ann]

Click to view full size image

Super Moon over 11th century Church of Dalby.
Photo: Michael Gehrisch.

Don't know if I'm allowed to, but I can't resist posting this beautiful orange-rose Super Moon rising over Scandinavia's oldest stone church, the Church of Dalby dating back to the eleventh century. Of course, the Moon is quite a bit older than that - and in its youth, Earth's faithful companion Luna orbited our favorite planet so closely that it would have put today's Super Moon to shame.

Ann

[Boomer12k]

Last night as I laid down to go to bed, I looked out the window. It was BRIGHT OUT... and the Moon was almost full, so I did get a glimpse... don't know about tonight though...

:---[===] *

[alter-ego]

What is the distance to the Super Moon tomorrow, at closest approach? What I'm really asking is for the distance variation between a micro moon (or from the average moon distance) and the Super Moon tomorrow.

Universetoday: “The semi-major axis (average distance) is 384,403 km (238,857 miles). At its closest point (known as perigee) the Moon is only 363,104 km (225,622 miles) away. And at its most distant point (called apogee) the Moon gets to a distance of 406,696 km (252,088 miles).”

Wikipedia: “Perigee varies from 356,400–370,400 km (221,457–230,156 mi). Apogee varies from 404,000–406,700 km (251,034–252,712 mi).”

Timeanddate.com: “14 nov 06:20 EST - 356,509 km (221,524 mi)”

The Super Moon numbers are interesting in detail, though mostly academic. The variation in the geocentric distance of the full moon is more complicated than a constant orbital ellipse. The distance also depends on the it's position wrt the ecliptic, and where the earth is wrt the sun in its elliptical orbit (e.g. perihelion vs. aphelion). The sun and earth continually perturb the moon's orbit - the primary reason why the perigee has ~14,000 km variation in the Wiki article.

I used an Horizons-based ephemeris to tabulate all full-moon geocentric distances over 6000 years (-2999 to +3000).
=> The average full-moon distance = 381103 km
This is ~3000 km less than the Universe Today article which is significant compared to the 180-km difference between tomorrow's full moon the closest one over the 6-millenia of full moons.

Tomorrow's Super Moon has a geocentric distance of 356519 km (at the official full-moon time, ~2.5 hours after closest distance = 356508 km)
=> Tomorrow's Super Moon will be ~2.3 arcminutes bigger than the average, 6000-yr full-moon
=> Over 6 millennia, tomorrow's Super Moon is in the top 346 Super Moons
=> Wrt the largest Super Moon (at 356337 km), tomorrow's is smaller by only 1 arcsec!
=> Wrt the APOD 2012 Super Moon, tomorrow's will be bigger by only 2.5 arcsec

As a note, the 1948 Super Moon was in the top 249, and a still better one in 1930 was in the top 58. The next better one in 2034 is in the top 133. The next Super Moon closest to tomorrow's will be on Jan 2, 2018. It will be in the top 727 and be only ~1/2 arcsec smaller.
So don't feel too bad you missed the biggest Super Moon, tomorrow will be about as spectacular as they get - Not very different

[hamilton1]

For purely human psychological reasons (not understood) any full moon looks much bigger near the horizon than it does high in the sky.

About the moon illusion... is it not simply the case that when near the horizon the moonlight is refracted by passing through a greater quantity of atmosphere, and therefore appears bigger... although presumably the experts would have thought of that.

No. Optically, the Moon can only be made to look smaller by atmospheric effects near the horizon- unchanged horizontally, compressed somewhat vertically.

(The Moon illusion isn't "not understood"; there are good explanations for how it works.)

Thanks Chris.

[neufer]

.
http://cseligman.com/text/sky/atmosphericrefraction.htm

[b][color=#0000FF]Shortly after the rising moon cleared the horizon, its distorted shape was obvious. The “squeezing” is caused by refraction in the atmosphere. Credit: Bob King[/color][/b]

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... is it not simply the case that when near the horizon the moonlight is refracted by passing through a greater quantity of atmosphere, and therefore appears bigger...

No. Optically, the Moon can only be made to look smaller by atmospheric effects near the horizon- unchanged horizontally, compressed somewhat vertically.

Except, perhaps,
in some cases of an inferior mirage.