APOD: Venus Transits the Midnight Sun (2012 Jun 20)

APOD Robot · Post by **APOD Robot** » Wed Jun 20, 2012 4:06 am

Venus Transits the Midnight Sun

Explanation: Today's solstice, the astronomical beginning of summer in the north, is at 23:09 UT when the Sun reaches the northernmost declination in its yearly trek through planet Earth's sky. While most in the northern hemisphere will experience the longest day of the year, for some the Sun won't set at all, still standing just above the horizon at midnight as far south as about 66.6 degrees northern latitude. Of course, as summer comes to the north the midnight Sun comes earlier to higher latitudes. Recorded near midnight, this time series from June 6 follows the Sun gliding above a mountainous horizon from a latitude of 69 degrees north. The remarkable scene looks north over the Norwegian Sea from Sortland, Norway. The 2012 transit of Venus is already in progress, with Earth's sister planet in silhouette at the upper left against the bright disk of the midnight Sun.

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Boomer12k · Post by **Boomer12k** » Wed Jun 20, 2012 4:27 am

I hope everybody has a wonderful Summer, and a nice Winter down under...oh, and plenty virgin sacrifices....that always helps....

:---[===} *

Beyond · Post by **Beyond** » Wed Jun 20, 2012 6:03 am

YUCK

Now we start the down-hill slide into the coldness of winter,

: emo62.gif (4.15 KiB) Viewed 3690 times

which we could probably use some of during the next two months.

: emo63.gif (2.38 KiB) Viewed 3690 times

saturno2 · Post by **saturno2** » Wed Jun 20, 2012 8:49 am

It¨s a strange Sun with Venus as a mole on his face

K1NS · Post by **K1NS** » Wed Jun 20, 2012 10:16 am

Interesting. If we didn't already know about the photograph, there'd be enough information in the image to calculate the time, date, and latitude where it was taken. I don't think it's possible to calculate the longitude, though (unless you happened to recognize the exact shape of that mountain). Anyone?

Steve Dutch · Post by **Steve Dutch** » Wed Jun 20, 2012 11:07 am

Perhaps the most interesting place to view the transit would have been Iceland. The transit began before sunset and was in progress at sunset, but because the sun was only below the horizon for a couple of hours, the transit was still in progress when the sun rose again.

orin stepanek · Post by **orin stepanek** » Wed Jun 20, 2012 12:07 pm

I found this item interesting http://astro.unl.edu/classaction/animat ... lorer.html Out here in the middle of the country; our days range from 8.9 hours to 15.i hours! Wow there are places up north that have no night! Around the equator; probably isn't much of a difference!

Ed Thompson · Post by **Ed Thompson** » Wed Jun 20, 2012 12:16 pm

In the discussion --- "for some the Sun won't set at all, still standing just above the horizon at midnight as far south as about 66.6 degrees northern latitude." Would the sun be above the horizon, or half the sun be above the horizon?

neufer · Post by **neufer** » Wed Jun 20, 2012 12:45 pm

K1NS wrote:
If we didn't already know about the photograph, there'd be enough information in the image to calculate the time, date, and latitude where it was taken. I don't think it's possible to calculate the longitude, though (unless you happened to recognize the exact shape of that mountain). Anyone?

We know that the local time is ~midnight from the fact that the sun maintains a constant altitude.

We also know the UTC time from the progression of the transit. Ego....

Moonlady · Post by **Moonlady** » Wed Jun 20, 2012 1:24 pm

saturno2 wrote:It¨s a strange Sun with Venus as a mole on his face

and I thought all the time that the sun looks like a cylops-smiley...

Chris Peterson · Post by **Chris Peterson** » Wed Jun 20, 2012 2:02 pm

Ed Thompson wrote:In the discussion --- "for some the Sun won't set at all, still standing just above the horizon at midnight as far south as about 66.6 degrees northern latitude." Would the sun be above the horizon, or half the sun be above the horizon?

The Sun will appear above the horizon because atmospheric refraction bends its rays. When you observe a normal sunset, the Sun is actually below the horizon as you observe it sitting on the horizon.

ozproff · Post by **ozproff** » Wed Jun 20, 2012 2:46 pm

"Today's solstice, the astronomical beginning of summer in the north"

No it does not!!!!!!! The solstice marks the MIDDLE of astronomical summer in the north!

I have enough trouble in my classes with this without APOD adding to the confusion.

owlice · Post by **owlice** » Wed Jun 20, 2012 3:00 pm

Astronomical
The precise timing of the seasons as viewed by astronomers is determined by the exact times of transit of the sun over the tropics of Cancer and Capricorn for the solstices and the times of the sun's transit over the equator for the equinoxes. [9] For 2012 these times are:
Code: Select all
Equinoxes                Solstices 
Mar 20, 05:14 UTC        June 20, 23:09 UTC 
Sept 22, 14:49 UTC       Dec 21, 11:12 UTC 
The following diagram shows the relation between the line of solstice and the line of apsides of Earth's elliptical orbit. The orbital ellipse (with eccentricity exaggerated for effect) goes through each of the six Earth images, which are sequentially the perihelion (periapsis—nearest point to the sun) on anywhere from 2 January to 5 January, the point of March equinox on 20 or 21 March, the point of June solstice on 20 or 21 June, the aphelion (apoapsis—farthest point from the sun) on anywhere from 4 July to 7 July, the September equinox on 22 or 23 September, and the December solstice on 21 or 22 December.

In astronomical reckoning, the solstices and equinoxes ought to be the middle of the respective seasons, but, because of thermal lag, regions with a continental climate often consider these four dates to be the start of the seasons as in the diagram, with the cross-quarter days considered seasonal midpoints. The length of these seasons is not uniform because of the elliptical orbit of the earth and its different speeds along that orbit.[10]

(Emphasis mine)
http://en.wikipedia.org/wiki/Season#Astronomical

Chris Peterson · Post by **Chris Peterson** » Wed Jun 20, 2012 3:43 pm

ozproff wrote:"Today's solstice, the astronomical beginning of summer in the north"

No it does not!!!!!!! The solstice marks the MIDDLE of astronomical summer in the north!

I have enough trouble in my classes with this without APOD adding to the confusion.

Well, since almost nobody knows what "astronomical summer" is, or uses it, there should be little confusion.

In most countries, the first days of the seasons begin, by convention or statute, on the solstices and equinoxes. Most countries quite properly consider today to mark the first day of summer, for the simple reason that they define it that way! Climatologically, the midpoint of the seasons occurs some time after the equinoxes or solstices, with that time determined mostly by latitude. For instance, at temperate latitudes, the climatological mid-summer occurs about a month after the solstice. This is consistent with considering "summer" to be June, July, and August, since the temperature in early June is typically similar to that in early September.

LocalColor · Post by **LocalColor** » Wed Jun 20, 2012 5:24 pm

Lovely APOD today!

We are at 44.9650 N latitude and 4800' (1463M) elevation. Our seasons pretty much correspond to the Solstices and Equinoxes - due to the elevation. (It got below freezing last night.) Looking forward to summer so we can stop burning wood at night to keep warm!

vofl · Post by **vofl** » Wed Jun 20, 2012 6:03 pm

It is difficult to understand - but todays image is KIND OF FAKE. When the midnight sun in on in Sortland, the daylight is on all day and all night. Real daylight all 24 hours. No darkness at all - The sky never gets dark and no stars visible.

Chris Peterson · Post by **Chris Peterson** » Wed Jun 20, 2012 6:07 pm

vofl wrote:It is difficult to understand - but todays image is KIND OF FAKE. When the midnight sun in on in Sortland, the daylight is on all day and all night. Real daylight all 24 hours. No darkness at all - The sky never gets dark and no stars visible.

The sky is always dark when you view the Sun through a dark enough filter to allow it to be seen safely. If this image were exposed so that the sky appeared as it actually does, the Sun would be a blown-out white blob and Venus would be lost in the glare. Venus transit images that show the sky as something other than black are the ones most likely to be "faked".

vofl · Post by **vofl** » Wed Jun 20, 2012 7:30 pm

Today's solstice, the ... OOPS - solstice is tomorrow ! At least in most of Europe and eastwards. In Denmark Solstice is at 1:09 21. june 2012 (MET summer time).

Chris Peterson · Post by **Chris Peterson** » Wed Jun 20, 2012 7:38 pm

vofl wrote:Today's solstice, the ... OOPS - solstice is tomorrow ! At least in most of Europe and eastwards. In Denmark Solstice is at 1:09 21. june 2012 (MET summer time).

But since UT is the standardized way the time of the solstice is given, it really is today: 20 June 2012, UT 23:09. And for me here in Colorado, it's at 17:09... today.

Anthony Barreiro · Post by **Anthony Barreiro** » Wed Jun 20, 2012 10:35 pm

All definitional contention aside, I hope everyone has a joyful Solstice, whether you call it Midsummer as was the common usage in Shakespeare's time (thus "A Midsummer Night's Dream" happens on the shortest night of the year, i.e. Solstice), or the first day of Summer as is more common today, or even the first day of winter if you happen to be down under. When I was outside around noon (1:11 pm Pacific Daylight Time here in San Francisco), my shadow was pretty darn short!

Chris Peterson · Post by **Chris Peterson** » Wed Jun 20, 2012 11:05 pm

Anthony Barreiro wrote:All definitional contention aside, I hope everyone has a joyful Solstice, whether you call it Midsummer as was the common usage in Shakespeare's time (thus "A Midsummer Night's Dream" happens on the shortest night of the year, i.e. Solstice), or the first day of Summer as is more common today, or even the first day of winter if you happen to be down under. When I was outside around noon (1:11 pm Pacific Daylight Time here in San Francisco), my shadow was pretty darn short!

Dang! With the whole state under a red flag fire warning, we can't do our ritual naked midnight bonfire dance!

Anthony Barreiro · Post by **Anthony Barreiro** » Wed Jun 20, 2012 11:33 pm

Chris Peterson wrote: Dang! With the whole state under a red flag fire warning, we can't do our ritual naked midnight bonfire dance!

You can still go outside and dance naked. This year Mother Nature seems to be providing one hell of a bonfire for Colorado. I hope all will be well for you and yours.

Guest · Post by **Guest** » Thu Jun 21, 2012 12:46 am

The caption for today's image refers to Venus as our "sister planet". Does that make Mars the eath's brother planet?

canesvenatici · Post by **canesvenatici** » Thu Jun 21, 2012 3:31 am

Chris Peterson wrote:
Anthony Barreiro wrote:All definitional contention aside, I hope everyone has a joyful Solstice, whether you call it Midsummer as was the common usage in Shakespeare's time (thus "A Midsummer Night's Dream" happens on the shortest night of the year, i.e. Solstice), or the first day of Summer as is more common today, or even the first day of winter if you happen to be down under. When I was outside around noon (1:11 pm Pacific Daylight Time here in San Francisco), my shadow was pretty darn short!
Dang! With the whole state under a red flag fire warning, we can't do our ritual naked midnight bonfire dance!

Wait, wasn't that the Maypole dancing bit for Spring? Right now not even my musically inclined chocolate lab wants to dance in this high desert heat; even the weeds are choking. Skies a bit hazy, too, maybe from those various forest fires? At 4-5 a.m. there looks to be a distinct brownish layer of "air" ground-up, much as in winter-time inversion layers.

Perk Cartel · Post by **Perk Cartel** » Thu Jun 21, 2012 4:22 am

For any who may still be confused why APOD is understandably only a litle north hemisphere centric, this quote from the Museum of Victoria, Australia :
"In some parts of the world, such as Australia, seasons begin on the first day of a particular calendar month - in March for Autumn, June for Winter, September for Spring and December for Summer. In most other countries such as Britain and the US, it’s accepted that the seasons begin on the dates that the Earth passes four special points in its orbit about the Sun, the two equinoxes and two solstices that occur each year." In the State of Victoria in the south eastern part of Australia, the indigenous folk recognise six seasons ( no so called "autumn" or "fall" perhaps because indigenous vegetation here is non-deciduous. There's more here: http://home.vicnet.net.au/~herring/seasons.htm

Starship Asterisk*

APOD: Venus Transits the Midnight Sun (2012 Jun 20)

APOD: Venus Transits the Midnight Sun (2012 Jun 20)

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