APOD: Eclipse Over New York (2013 Nov 04)

APOD Robot · Post by **APOD Robot** » Mon Nov 04, 2013 5:06 am

Eclipse Over New York

Explanation: A sunrise over New York City rarely looks like this. Yesterday, however, the Sun rose partly eclipsed by the Moon as seen from much of the eastern North American and northern South America. Simultaneously, much of Africa, already well into daytime, saw the eclipse from beginning to end. The eclipse was unusual in that it was a hybrid -- parts of the Earth saw the Moon as too angularly small to cover the whole Sun, and so at maximum coverage left the Sun surrounded by a ring a fire, while other parts of the Earth saw the Moon as large enough to cover the entire Sun, and so at maximum coverage witnessed a total solar eclipse. Slight changes in the angular size of the Moon as seen from the Earth's surface are caused by the non-flatness of the Earth and the ellipticity of the Moon's orbit. Pictured above, the famous Empire State Building in New York City is seen to the left of the partially eclipsed Sun, adorned with scenic clouds. The next solar eclipse visible from New York City -- a very slight eclipse -- will occur during the sunset of 2014 October 23.

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Boomer12k · Post by **Boomer12k** » Mon Nov 04, 2013 9:14 am

Awesome lookin'.....

:---[===] *

neufer · Post by **neufer** » Mon Nov 04, 2013 11:06 am

On average:

1) an annular eclipse happens every 15 months
2) a total eclipse happens every 19 months
3) a hybrid eclipse happens every 105 months

Beyond · Post by **Beyond** » Mon Nov 04, 2013 11:57 am

On average:

1) I have cloud filled skies whenever an astronomical event occurs.
2) I spend a lot of time with my head below the clouds.

FloridaMike · Post by **FloridaMike** » Mon Nov 04, 2013 1:29 pm

Click to play embedded YouTube video.

Guest · Post by **Guest** » Mon Nov 04, 2013 1:50 pm

Fantastic picture today - one of the best I have seen.

Nick

MarkBour · Post by **MarkBour** » Mon Nov 04, 2013 3:56 pm

Beyond wrote:On average:
1) I have cloud filled skies whenever an astronomical event occurs.
2) I spend a lot of time with my head below the clouds.

Hear, hear. It seems to happen to me a lot, too. I'm hoping ISON will be good and that I won't have party-spoiling weather.
----------
I can understand that the angular size of the Moon from Earth's surface is nearly the same as the angular size of the Sun. It seems like an amazing coincidence, but there it is. And I'm guessing that when the Moon is farther away from the Earth during an eclipse, we get an annular eclipse, and when closer, to us, we get a full eclipse. For a hybrid eclipse, then, I guess it has to be at just about the right distance for a minimal full eclipse, and is it correct that lower elevations on the Earth would see the annular eclipse, while higher elevations would get the full eclipse, by being a little closer to the Moon? (They're also closer to the Sun, but the relative distance change to the Moon would be much greater than to the Sun.) And it's a matter of "true elevation" from the center of the Earth, rather than elevation above sea level, which is a bit irregular.

As a rank amateur, I believe I can figure this out, but I'm really just asking if I have this correct ...

ta152h0 · Post by **ta152h0** » Mon Nov 04, 2013 4:03 pm

yeah, my brother in law has a telescope that collects more dust than light. I am hoping we have a really really cold winter where the skies will be clear for Comet ISON. And that other comet that is/is not going to hit Mars.

neufer · Post by **neufer** » Mon Nov 04, 2013 4:19 pm

ta152h0 wrote:
I am hoping we have a really really cold winter where the skies will be clear for Comet ISON.

And that other comet that is/is not going to hit Mars.

Which other comet

http://en.wikipedia.org/wiki/Comet_ISON wrote:
<<On its closest approach, C/2012 S1 passed about 0.07248 AU from Mars on 1 October 2013.>>

ta152h0 · Post by **ta152h0** » Mon Nov 04, 2013 4:24 pm

http://www.space.com/20512-mars-comet-c ... -odds.html

neufer · Post by **neufer** » Mon Nov 04, 2013 4:26 pm

http://astrobob.areavoices.com/2013/11/03/photos-of-sundays-rare-hybrid-solar-eclipse/ wrote:
<<Total solar eclipse photographed by Finnish photographer Janne Pyykkö, who traveled to Gulu, Uganda. He befriended a local university student there named Irene who holds two plates of oranges in this photo taken during totality.

Check out Janne’s blog for more information.

Credit: Janne Pyykkö (janne.pyykko@gmail.com)>>

Chris Peterson · Post by **Chris Peterson** » Mon Nov 04, 2013 4:39 pm

neufer wrote:
ta152h0 wrote:
I am hoping we have a really really cold winter where the skies will be clear for Comet ISON.

And that other comet that is/is not going to hit Mars.

Which other comet :?:

I assume he's referring to C/2013 A1 (Siding Spring), which will make an extremely close pass of Mars in October 2014. Colleagues of mine who have analyzed the encounter are predicting that Mars (which will pass through the debris stream) may see a meteor shower with a ZHR exceeding one million events per hour. There is real concern for the safety of our various orbiters around Mars (the rovers should be fine on the ground, but if they lose the communications relays in orbit, their operation will be severely limited).

geckzilla · Post by **geckzilla** » Mon Nov 04, 2013 4:50 pm

Chris Peterson wrote:
neufer wrote:
ta152h0 wrote:
I am hoping we have a really really cold winter where the skies will be clear for Comet ISON.

And that other comet that is/is not going to hit Mars.

Which other comet

I assume he's referring to C/2013 A1 (Siding Spring), which will make an extremely close pass of Mars in October 2014. Colleagues of mine who have analyzed the encounter are predicting that Mars (which will pass through the debris stream) may see a meteor shower with a ZHR exceeding one million events per hour. There is real concern for the safety of our various orbiters around Mars (the rovers should be fine on the ground, but if they lose the communications relays in orbit, their operation will be severely limited).

Oh crap, micrometeorite storm just like from a movie!

Ron-Astro Pharmacist · Post by **Ron-Astro Pharmacist** » Mon Nov 04, 2013 5:34 pm

It was sun many in New York might identify with… It’s got on a Yarmulke.

neufer · Post by **neufer** » Mon Nov 04, 2013 6:55 pm

Chris Peterson wrote:
neufer wrote:
ta152h0 wrote:
I am hoping we have a really really cold winter where the skies will be clear for Comet ISON.

And that other comet that is/is not going to hit Mars.

Which other comet

I assume he's referring to C/2013 A1 (Siding Spring), which will make an extremely close pass of Mars in October 2014. Colleagues of mine who have analyzed the encounter are predicting that Mars (which will pass through the debris stream) may see a meteor shower with a ZHR exceeding one million events per hour. There is real concern for the safety of our various orbiters around Mars (the rovers should be fine on the ground, but if they lose the communications relays in orbit, their operation will be severely limited).

Ah, yes

Now I remember that MAVEN & Mangalyaan (which are both just about to take off) were supposed to be at Mars for that event. With all the excitement about ISON's photo being taken from MARS I had conflated the two comets.

http://en.wikipedia.org/wiki/C/2013_A1 wrote:
The spacecraft MAVEN & Mangalyaan will arrive at Mars one month before the comet's closest approach. The comet is not expected to create a spectacular meteor shower on Mars or be a threat to the spacecraft in orbit or on the ground. The comet will have to be extremely close to Mars for its debris to pose any real risk. At the time of closest approach, the comet will be ~142,000 km (42 R_M) from the center-point of Mars on the sunward side of the planet. Millimeter-sized grains will be ejected at about 1 m/s, and would take more than a year to travel 100,000 km from the comet.
Code: Select all
Perihelion 	     1.39875 AU
Eccentricity 	   1.00046
Inclination 	    129.0°
Next perihelion 	25 October 2014
Orbital period 	~700,000 yr
(Barycentric solution for epoch 2050)

Chris Peterson · Post by **Chris Peterson** » Mon Nov 04, 2013 7:01 pm

neufer wrote:
http://en.wikipedia.org/wiki/C/2013_A1 wrote:
The spacecraft MAVEN & Mangalyaan will arrive at Mars one month before the comet's closest approach. The comet is not expected to create a spectacular meteor shower on Mars or be a threat to the spacecraft in orbit or on the ground. The comet will have to be extremely close to Mars for its debris to pose any real risk. At the time of closest approach, the comet will be ~142,000 km (42 R_M) from the center-point of Mars on the sunward side of the planet. Millimeter-sized grains will be ejected at about 1 m/s, and would take more than a year to travel 100,000 km from the comet.

I have not made any study myself of this comet at Mars. But several people who are very much experts on this, and whose analyses I do trust, feel that the risk to our assets at Mars has been significantly understated. Whether that is deliberate or not, I can't say (and I'm not one for conspiracy theories). But I do think that this encounter is likely to be an interesting one.

ta152h0 · Post by **ta152h0** » Mon Nov 04, 2013 7:06 pm

interesting encounter like the type Gen Custer had ? Certainly not a " quiet universe " lately

neufer · Post by **neufer** » Mon Nov 04, 2013 8:04 pm

Chris Peterson wrote:
neufer wrote:
http://en.wikipedia.org/wiki/C/2013_A1 wrote:
[Comet ISON] is not expected to create a spectacular meteor shower on Mars or be a threat to the spacecraft in orbit or on the ground. The comet will have to be extremely close to Mars for its debris to pose any real risk. At the time of closest approach, the comet will be ~142,000 km (42 R_M) from the center-point of Mars on the sunward side of the planet. Millimeter-sized grains will be ejected at about 1 m/s, and would take more than a year to travel 100,000 km from the comet.
I have not made any study myself of this comet at Mars. But several people who are very much experts on this, and whose analyses I do trust, feel that the risk to our assets at Mars has been significantly understated. Whether that is deliberate or not, I can't say (and I'm not one for conspiracy theories). But I do think that this encounter is likely to be an interesting one.

Those analyses might be somewhat outdated by now:

"Initial observations by Leonid Elenin on 27 February 2013, suggested
[Comet ISON would probably] pass 41,300 km from the center-point of Mars."

http://www.universetoday.com/102257/astronomers-detect-dust-feature-in-comet-isons-inner-coma/ wrote:
Astronomers Detect Dust Feature in Comet ISON’s Inner [Dust] Coma
by Nancy Atkinson on May 20, 2013

<<Estimates suggest that the nucleus of ISON is no larger than 4-6 km across
while the comet’s dusty coma, or head of the comet is approximately 5,000 km across.>>

Chris Peterson · Post by **Chris Peterson** » Mon Nov 04, 2013 8:20 pm

neufer wrote:Those analyses might be somewhat outdated by now:

"Initial observations by Leonid Elenin on 27 February 2013, suggested
[Comet ISON would probably] pass 41,300 km from the center-point of Mars."

No, they are based on the best current orbital elements and well accepted flux models. I guess we'll see.

BTW, it would be a mistake to underestimate the possible size of the coma when the comet passes Mars, and the sort of ejection velocities a Whipple-type model suggests for millimeter-scale particles is more in the 20-40 m/s range, not 1 m/s.

FloridaMike · Post by **FloridaMike** » Mon Nov 04, 2013 8:44 pm

Just a wild guess here but I'm thinking Mars will have its own annual meteor shower as a result of the commit fly-by you guys are discussing. True?

neufer · Post by **neufer** » Mon Nov 04, 2013 9:21 pm

FloridaMike wrote:
Just a wild guess here but I'm thinking Mars will have its own annual meteor shower as a result of the commit fly-by you guys are discussing. True?

Yes. The question is only whether it starts in 2014 or 2016.

Anthony Barreiro · Post by **Anthony Barreiro** » Mon Nov 04, 2013 9:22 pm

MarkBour wrote:
Beyond wrote:On average:
1) I have cloud filled skies whenever an astronomical event occurs.
2) I spend a lot of time with my head below the clouds.
Hear, hear. It seems to happen to me a lot, too. I'm hoping ISON will be good and that I won't have party-spoiling weather.
----------
I can understand that the angular size of the Moon from Earth's surface is nearly the same as the angular size of the Sun. It seems like an amazing coincidence, but there it is. And I'm guessing that when the Moon is farther away from the Earth during an eclipse, we get an annular eclipse, and when closer, to us, we get a full eclipse. For a hybrid eclipse, then, I guess it has to be at just about the right distance for a minimal full eclipse, and is it correct that lower elevations on the Earth would see the annular eclipse, while higher elevations would get the full eclipse, by being a little closer to the Moon? (They're also closer to the Sun, but the relative distance change to the Moon would be much greater than to the Sun.) And it's a matter of "true elevation" from the center of the Earth, rather than elevation above sea level, which is a bit irregular.

As a rank amateur, I believe I can figure this out, but I'm really just asking if I have this correct ...

My understanding is that the Earth's total size is a much more significant factor in causing hybrid annular-total eclipses than are variations in elevation. The highest points on Earth are less than 10 km above sea level. With a diameter of about 13,000 km, the surface of the Earth at the noontime meridian is about 6,000 km closer to the Sun than the surface of the Earth at the sunrise and sunset meridians.

Solar eclipses happen at new Moon, when the Moon is between the Earth and the Sun in space. The surface of the Earth at the sunrise meridian is farther from the Moon than the surface of the Earth at the noontime meridian. So as the Moon orbits the Earth her umbral shadow is not quite long enough to reach the surface of the Earth at sunrise, but as she orbits toward the Earth's noon meridian there is less distance between the surface of the Earth and the Moon, so the Moon's umbra is just long enough to reach the surface of the Earth. Voila.

Chris Peterson · Post by **Chris Peterson** » Mon Nov 04, 2013 10:02 pm

Anthony Barreiro wrote:My understanding is that the Earth's total size is a much more significant factor in causing hybrid annular-total eclipses than are variations in elevation. The highest points on Earth are less than 10 km above sea level. With a diameter of about 13,000 km, the surface of the Earth at the noontime meridian is about 6,000 km closer to the Sun than the surface of the Earth at the sunrise and sunset meridians.

While I agree completely with what you are saying, I'd like to point out that "sea level" isn't a very useful metric in this case. What matters is the distance of the observer from the center of the Earth, and in addition to the approximately 10 km variation due to surface roughness, there is also another 20 km because of the oblateness of the mean surface. Still small compared with the radius of the Earth, of course.

Anthony Barreiro · Post by **Anthony Barreiro** » Mon Nov 04, 2013 11:36 pm

Chris Peterson wrote:
Anthony Barreiro wrote:My understanding is that the Earth's total size is a much more significant factor in causing hybrid annular-total eclipses than are variations in elevation. The highest points on Earth are less than 10 km above sea level. With a diameter of about 13,000 km, the surface of the Earth at the noontime meridian is about 6,000 km closer to the Sun than the surface of the Earth at the sunrise and sunset meridians.
While I agree completely with what you are saying, I'd like to point out that "sea level" isn't a very useful metric in this case. What matters is the distance of the observer from the center of the Earth, and in addition to the approximately 10 km variation due to surface roughness, there is also another 20 km because of the oblateness of the mean surface. Still small compared with the radius of the Earth, of course.

Thanks Chris.

By the way, this article from earthsky.org has very clear simple diagrams of a hybrid solar eclipse, a cool animation of the eclipse path, and lots of lovely pictures of the eclipse.

alter-ego · Post by **alter-ego** » Tue Nov 05, 2013 6:26 am

Anthony Barreiro wrote:
Chris Peterson wrote:
Anthony Barreiro wrote:My understanding is that the Earth's total size is a much more significant factor in causing hybrid annular-total eclipses than are variations in elevation. The highest points on Earth are less than 10 km above sea level. With a diameter of about 13,000 km, the surface of the Earth at the noontime meridian is about 6,000 km closer to the Sun than the surface of the Earth at the sunrise and sunset meridians.
While I agree completely with what you are saying, I'd like to point out that "sea level" isn't a very useful metric in this case. What matters is the distance of the observer from the center of the Earth, and in addition to the approximately 10 km variation due to surface roughness, there is also another 20 km because of the oblateness of the mean surface. Still small compared with the radius of the Earth, of course.
Thanks Chris.

By the way, this article from earthsky.org has very clear simple diagrams of a hybrid solar eclipse, a cool animation of the eclipse path, and lots of lovely pictures of the eclipse.

And don't forget the Moon's elliptical orbit. It ranks second to the earth's size/rotation affect on the hybrid eclipse. Over the 3 1/2-hour eclipse duration, the Moon's geocentric distance from Earth decreased by 490 km.

Starship Asterisk*

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