APOD: Moon, Mars, and Milky Way (2018 Aug 11)

[APOD Robot]

Moon, Mars, and Milky Way

Explanation: Just two weeks ago, dark skies over the desert in northern Iran held this alluring celestial vista. The dramatic digital mosaic finds the Moon and Mars alongside the Milky Way's dusty rifts, stars, and nebulae. Captured through a series of exposures to cover a range in brightness, that night's otherwise Full Moon is immersed in Earth's shadow. It actually appears fainter and redder than the Red Planet itself during the widely watched total lunar eclipse. For cosmic tourists, the skyscape also includes the Lagoon (M8) and Trifid (M20) nebulae and planet Saturn shining against the Milky Way's pale starlight. The Moon isn't quite done with its shadow play, though. Today, the New Moon partially eclipses the Sun for much of northern planet Earth.

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[Chris Peterson]

There's something horribly wrong with this image. No lunar eclipse has ever looked remotely like that.

[Ann]

There's something horribly wrong with this image. No lunar eclipse has ever looked remotely like that.

And I was about to say that I like the picture.

Ann

[alter-ego]

There's something horribly wrong with this image. No lunar eclipse has ever looked remotely like that.

I thought the same thing. I think it's the result of the multiple images and the range of exposures. An overexposed lunar eclipse image simply summed with a correctly exposed image might produce the bright annular ring that bothered me.

[Ann]

There's something horribly wrong with this image. No lunar eclipse has ever looked remotely like that.

I thought the same thing. I think it's the result of the multiple images and the range of exposures. An overexposed lunar eclipse image simply summed with a correctly exposed image might produce the bright annular ring that bothered me.

I get your point. Lunar eclipses don't have annular rings.

Ann

[De58te]

Grateful for the description, because at first I thought that the red object was Mars and the cameraman was lying on his back taking the picture. However I didn't think that Mars, the brighter light in the photo, even though it was making its closest approach to Earth, still it didn't look the same size as the Moon when I looked. Was it true then what they said on youtube, that Mars would grow as big as the Moon in the sky?

[heehaw]

I think we have, at last, an astronomical picture from a parallel universe. I like OUR universe!

[Sa Ji Tario]

it resembles an annular eclipse and appears with the same diameter of Mars

[BDanielMayfield]

Grateful for the description, because at first I thought that the red object was Mars and the cameraman was lying on his back taking the picture. However I didn't think that Mars, the brighter light in the photo, even though it was making its closest approach to Earth, still it didn't look the same size as the Moon when I looked. Was it true then what they said on youtube, that Mars would grow as big as the Moon in the sky?

(Color chosen to display my reaction upon reading that question.) Sorry De58te, but seriously? The explanation is that bright, overexposed objects in photographs appear much larger than they actually are ...

Or,

I think we have, at last, an astronomical picture from a parallel universe.

in which the other Earth has a small moon that eclipsed the system's second sun (a red dwarf) and there is a nearby globular cluster.

Bruce

[Ann]

Grateful for the description, because at first I thought that the red object was Mars and the cameraman was lying on his back taking the picture. However I didn't think that Mars, the brighter light in the photo, even though it was making its closest approach to Earth, still it didn't look the same size as the Moon when I looked. Was it true then what they said on youtube, that Mars would grow as big as the Moon in the sky?

Certainly not. From my vantage point in Malmö, Sweden, the eclipsed Moon was a pink disk, whereas Mars was a brilliant point of yellow-orange light below it.

The reason why Mars looks as big as the Moon in today's APOD must be pixel bleeding. This causes tiny bright objects to look larger in photographs than they do in the sky.

Edit: If Mars really looked as large as the Moon in the sky, us human passengers on spaceship Earth, who enjoy our planet's stable orbit around the Sun, would be in trouble. The Earth might decide it would follow an entirely different orbit around the Sun if Mars got close enough to look as big as the Moon. Alternatively, our favorite planet might get kicked out of the Solar system altogether if Mars paid us such an intimate visit. In any case, we wouldn't like it.

Ann (who is a fan of a small-looking Mars)

[BDanielMayfield]

If Mars really looked as large as the Moon in the sky, us human passengers on spaceship Earth, who enjoy our planet's stable orbit around the Sun, would be in trouble. The Earth might decide it would follow an entirely different orbit around the Sun if Mars got close enough to look as big as the Moon. Alternatively, our favorite planet might get kicked out of the Solar system altogether if Mars paid us such an intimate visit. In any case, we wouldn't like it.

Ann (who is a fan of a small-looking Mars)

Me too Ann. But in your senario I think Mars would get kicked out of the solar system, while Earth might collide with Venus. Not cool, in more ways than one.

Another thing that appears off in this APOD is the color of Mars (or the globular mascurading as Mars ) Shouldn't it appear redder?

Bruce

[neufer]

There's something horribly wrong with this image. No lunar eclipse has ever looked remotely like that.

<<The Monolith suddenly disappears, and a growing black spot appears on Mars itself. The spot is actually a vast group of Monoliths that are exponentially multiplying. The Monoliths begin shrinking Mars's volume, increasing the planet's density, and modifying its chemical composition.>>

[Chris Peterson]

There's something horribly wrong with this image. No lunar eclipse has ever looked remotely like that.

I thought the same thing. I think it's the result of the multiple images and the range of exposures. An overexposed lunar eclipse image simply summed with a correctly exposed image might produce the bright annular ring that bothered me.

Yes, I don't suggest anything underhanded is going on. It's just very poor image processing.

[Chris Peterson]

The reason why Mars looks as big as the Moon in today's APOD must be pixel bleeding. This causes tiny bright objects to look larger in photographs than they do in the sky.

In any wide angle image of the sky, bright stars and planets appear to be much larger than the single pixel they should occupy (and in most cases, even a single pixel is too large). A combination of diffraction and scatter in the atmosphere and optics. And in this case, Mars is overexposed, which means all the color channels are saturated, making it appear white. In creating this composite, a shorter exposure should have been used for Mars, which would have resulted in a smaller and more accurately colored rendering.

[Boomer12k]

We are truly one world....we see the same wonders...maybe not at the same time...

very nice work.
:---[===] *

[Boomer12k]

I think it is over exposed, to get the Milky Way more exposed for the image...and put stacked, or combined, it made Mars and the Moon appear...."off"...

I overexpose Jupiter to see moons better.

Still very nice.
:---[===] *

[FLPhotoCatcher]

Ok, time to change the subject a bit?
Could a Martian ever see the sun eclipsed by the Earth? What about the Earth and Moon?

[BDanielMayfield]

Ok, time to change the subject a bit?
Could a Martian ever see the sun eclipsed by the Earth? What about the Earth and Moon?

Not with her naked eyes, provided that Martians even have eyes.

Just as we can sometimes see (with optical aids) our inner planets Mercury and Venus pass across the sun's disc, someone on Mars could occasionally see those planets as well as the Earth passing in front of Sol. But such rare events, also called occultations, aren't near as noticeable as the much more common eclipses involving our Moon are here on Earth. Lunar and solar eclipses here can be spectacularly noticeable due to the effects of the Moon and the Sun appearing to be just about the same size from our vantage point on Earth.

But the Sun is about 108 times Earth's diameter, so seeing the Earth or slightly smaller Venus drifting across the face of the Sun from Mars would require magnification and filtering, and even more magnification might be needed to watch the smaller Mercury and Luna occult the Sun.

As for Earth and Moon, yes, a well equipped Martian could on very rare occasions observe both Earth and our Moon passing across the Sun at the same time. But due to orbital tilts, alignments and such some events would involve just our Moon, some just Earth, and some the Moon and then the Earth or vise versa.

Bruce

[BDanielMayfield]

Follow up questions for someone with planetarium software to answer: (1) Would it ever be possible to observe from Mars an occultion event in which the Moon also passes in front of or behind the Earth during the Solar event? (2) Is the duration of Earth/Moon occultions short enough to be completely observed during the solar passage? (3) Eclipse chasers want to know, when will this happen?

Bruce

[Chris Peterson]

Follow up questions for someone with planetarium software to answer: (1) Would it ever be possible to observe from Mars an occultion event in which the Moon also passes in front of or behind the Earth during the Solar event? (2) Is the duration of Earth/Moon occultions short enough to be completely observed during the solar passage? (3) Eclipse chasers want to know, when will this happen? :lol2:

In terms of simple geometry, I can't see why this wouldn't occur, since all the bodies cross the ecliptic and I don't think there are any resonances in the orbits involved. I'll leave it to someone else to figure out when this might occur. Not very often, I imagine!

[geckzilla]

I gave up after the year 2084, which is the first time since today Earth transits the Sun as viewed from Mars as far as I can tell.

[BDanielMayfield]

I gave up after the year 2084, which is the first time since today Earth transits the Sun as viewed from Mars as far as I can tell.

You mean it's doing so today Darn, we missed it.

[geckzilla]

I gave up after the year 2084, which is the first time since today Earth transits the Sun as viewed from Mars as far as I can tell.

You mean it's doing so today Darn, we missed it.

Yeah, yeah... I was trying to think of a way to say I started from today and looked forward.

[BDanielMayfield]

I gave up after the year 2084, which is the first time since today Earth transits the Sun as viewed from Mars as far as I can tell.

You mean it's doing so today Darn, we missed it.

Yeah, yeah... I was trying to think of a way to say I started from today and looked forward.

As I figured. But a literal reading was more amusing. And also quite possible, since all other planets in our solar system cross the ecliptic plain twice each orbit.

Bruce

[neufer]

I gave up after the year 2084, which is the first time since today Earth transits the Sun as viewed from Mars as far as I can tell.

Statistically an Earth transit occurs every 66 (Earth) years on average but a really boring transit where the Moon is hidden behind or in front of the Earth happens only once every million years or so.

Earth and Moon transiting the Sun in 2084, as seen from Mars. Image created using JPL Solar System Simulator

---

<<During an Earth transit event, the Moon could almost always also be seen in transit, 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). The last Earth transit took place on May 11, 1984. A science fiction short story by Arthur C. Clarke, called "Transit of Earth", depicts a doomed astronaut on Mars observing the 1984 transit. This short story was first published in the January 1971 issue of Playboy magazine.>>