APOD: Neptune: Once Around (2011 Jul 14)

[APOD Robot]

Neptune: Once Around

Explanation: Neptune rotates once on its axis in about 16 hours. So, spaced about 4 hours apart these 4 images of the solar system's most distant gas giant cover one Neptune day. Recorded by the Hubble Space Telescope in late June they combine exposures made with visible and near-infrared filters to show high-altitude clouds composed of methane ice crystals against the planet's normally blue cloud tops. Because Neptune's axis of rotation is tilted to its orbital plane by 29 degrees, compared to Earth's 23.5 degrees, Neptune experiences seasons analogous to Earth's. As early summer comes to Neptune's southern hemisphere and winter to the north, Hubble observations have shown cloud activity shifting to the northern hemisphere. In fact the progression of Neptune's seasons has come around once since its position was predicted by French mathematician Urbain Le Verrier and British mathematician John Couch Adams, and the planet was subsequently discovered by German astronomer Johann Galle on September 23, 1846. With an orbital period of approximately 165 years, this week on July 12, Neptune has been once around the Sun since its discovery date.

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[petermadelaine]

4 images x 4 hours apart gives 12 hours (3 intervals) not 16, and the time dfference between the first and last image shown is in fact 11 hours and a half. hence you have not shown a complete day.

[Neil Stahl]

One image from each quarter of the day "covers" it as far as I'm concerned.

I'm looking forward to what the solons here have to say about Neptune. We don't hear a lot about it.

[Brem2]

I'm confused by the N/E indicators in the lower right corner. Do the mean north and east, and is the east to the left?

[Indigo_Sunrise]

So..... what was Tuesday's image again?????


And WOW! Look at the lurkers oozing out of the woodwork!

@petermadelaine: Picky, picky! Regardless of the number of images, the time stamps tell how much of Neptune's day is shown.....

@Neil Stahl: I like the word use - 'solons'. Thanks! I learned something else today!

@Brem2: Yes, those are the directions. Many images are 'mirrored' because of how they are acquired with telescopes. (I'm short on time, so I'm probably not being clear, but I'm sure the solons that frequent these forums will be along to clarify!)

Great image and even better links!

[neufer]

I'm confused by the N/E indicators in the lower right corner. Do the mean north and east, and is the east to the left?

Go outside at night and look towards Polaris and to your right will be the east.

Now turn around 180º and draw a map of the sky with east to your left and north (towards Polaris) up above your head.

Sky maps are reverse mirror images of Earth maps because we look down on the convex Earth but up at the concave sky.

[neufer]

One image from each quarter of the day "covers" it as far as I'm concerned.

Me too.

I'm looking forward to what the solons here have to say about Neptune.

<<Solon (Σόλων, c. 638 BC – 558 BC) was an Athenian statesman, lawmaker, and poet. He is remembered particularly for his [failed] efforts to legislate against political, economic and moral decline in archaic Athens. He wrote poetry for pleasure, as patriotic propaganda. His works only survive in fragments and it is possible that fragments have been wrongly attributed to him.

Solon met with Croesus and gave the Lydian king advice. Croesus had considered himself to be the happiest man alive and Solon had advised him, "Count no man happy until he be dead", because at any minute, fortune might turn on even the happiest man and make his life miserable. It was only after he had lost his kingdom to the Persian king Cyrus, while awaiting execution, that Croesus acknowledged the wisdom of Solon's advice.>>

Oh...you must be talking about Chris.

[biddie67]

(( laughing )) solons, eh?? I had to look the word up also. Well, you solons keep it up - whatever your observations/opinions are, you make this forum interesting!!

As for the 4 pictures/3 quarters question :: if indeed, a 16-hour revolution of Neptune is accurate, then it seems like the 1st picture of Neptune is an implicit indication of what a 5th picture taken after the same time interval would look like - especially since it's reasonable to assume that the rate of rotation would more-or-less remain the same.

[orin stepanek]

Geez! on Neptune; I'd be less than 1/2 year old!

[neufer]

Geez! on Neptune; I'd be less than 1/2 year old!

How many months would that be?

(Triton orbital period: 5.877 earth days)

[Steve D]

The East arrow can be confusing. It's east on the sky, not on the planet.

[moonstruck]

It gets this way every year when school lets out for the summer. Too many solons.

[Beyond]

Gee,i woke up this morning feeling pretty good. Then i saw today's APOD. Now i'm feeling a little blue.

[Chris Peterson]

The East arrow can be confusing. It's east on the sky, not on the planet.

It is true that the arrows are intended to show the cardinal directions on the sky. However, except for the Earth, "east" on a planet is defined as the direction from which that planet rotates, so in this case, the arrows are approximately correct for Neptune as well: north is the upper part of each image, and east is to the left (adjusted for the axial inclination, of course).

[orin stepanek]

Geez! on Neptune; I'd be less than 1/2 year old!

How many months would that be?

(Triton orbital period: 5.877 earth days)

I come up with a bit over 5 months based on a 12 mo. year! I didn't do the day thing! but I came up with around 7528 Neptunium days in a Neptunium Month based on 12 months. ? is that pretty close?

[Ann]

There is a nice animation of Neptune's spin here: http://www.skyandtelescope.com/observin ... 92958.html

Ann

[neufer]

Geez! on Neptune; I'd be less than 1/2 year old!

How many months would that be?

(Triton orbital period: 5.877 earth days)

I come up with a bit over 5 months based on a 12 mo. year! I didn't do the day thing! but I came up with around 7528 Neptunium days in a Neptunium Month based on 12 months. ? is that pretty close?

No..no
A month isn't 1/12 of a year; a month is the synodic period of the main moon
~ 5.877 earth days. ~ 0.0161 earth years.

T

[neufer]

"east" on a planet is defined as the direction from which that planet rotates,

.

[neufer]

Gee,i woke up this morning feeling pretty good.
Then i saw today's APOD. Now i'm feeling a little blue.

At least you are not feeling blue-green.

[Chris Peterson]

"east" on a planet is defined as the direction from which that planet rotates,

. :?:

Seems clear enough. From which a point on the surface rotates? On any planet besides Earth, the stars rise in the west and set in the east?

[orin stepanek]

No..no
A month isn't 1/12 of a year; a month is the synodic period of the main moon
~ 5.877 earth days. ~ 0.0161 earth years.

T

OK! Well in that case Earth year is 13 Lunar orbits give or take. Art; this is tough! let me see--- 60,266 Earth days/5.877=10254 Neptunium months/year. 71/165= .4545+ of a year oldX10254= 4660 Neptunium months old or there abouts That's probably wrong also; but Oh well! Trouble is; Who knows how one from Neptune would measure time!

[neufer]

71/165= .4545+ of a year oldX10254= 4660 Neptunium [sic] months old or there abouts

4660 Neptunian months?

<<Neptunium (named for the planet Neptune, the next planet out from Uranus, after which uranium was named) was discovered by Edwin McMillan and Philip H. Abelson in 1940 at the Berkeley Radiation Laboratory of the University of California, Berkeley. The team produced the neptunium isotope 239Np (2.4 day half-life) by bombarding uranium with slow moving neutrons. It was the first transuranium element produced synthetically and the first actinide series transuranium element discovered.

The periodic table of Dmitri Mendeleev published in the 1870s showed a — in place after uranium similar to several other places for at that point undiscovered elements. At least three times, discoveries of the element 93 were falsely reported, as bohemium, ausonium in 1934 and then sequanium in 1939.

The search for element 93 in minerals was encumbered by the fact that the predictions on the chemical properties of element 93 were based on a periodic table which lacked the actinides series and therefore placed thorium below hafnium, protactinium below tantalum and uranium below tungsten. This periodic table suggested that element 93, at that point often named eka-rhenium, should be similar to manganese or rhenium. With this misconception it was impossible to isolate element 93 from minerals although later neptunium was found in uranium ore in 1952.

Enrico Fermi believed that bombarding uranium with neutrons and subsequent beta decay would lead to the formation of element 93. Chemical separation of the new formed elements from the uranium yielded material with low half-life and therefore Fermi announced the discovery of a new element in 1934, though this was soon found to be mistaken. Soon it was speculated and later proven that most of the material is created by nuclear fission of uranium by neutrons. Small quantities of neptunium had to be produced in Otto Hahn's experiments in late 1930s as a result of decay of 239U. Hahn and his colleagues experimentally confirmed production and chemical properties of 239U, but were unsuccessful at isolating and detecting neptunium.>>

[nstahl]

Ok, Neil Stahl, above, is me. Or maybe I'm Neil Stahl. For some reason I wasn't automatically myself this morning. Maybe my computer hadn't had its coffee? And maybe "solon" wasn't exactly the word I was reaching for, but close enough.

I ran across one link of interest at Centauri Dreams by Paul Gilster.

The story of Neptune’s discovery is a fascinating topic in itself. Galileo actually recorded Neptune in his notebooks but didn’t follow up the observation. British astronomer William Herschel would later note that the orbit of Uranus did not behave as expected according to Newton’s laws, leading to speculations (like those of French astronomer Alexis Bouvard in 1821) that another planet was tugging at Uranus. Both Urbain Le Verrier and John Couch Adams predicted the location of the putative planet in the 1840s, but it was Le Verrier who described his prediction to Galle at the Berlin Observatory. After that, it was a matter of two nights of observation before Galle was able to identify the planet. Although the Royal Society would award Le Verrier the Copley Medal for his work, supporters of Adams defended his right to be considered a co-discoverer. Recent work has cast doubt on the idea.

He also gives some Sci Fi refs to Neptune and a short H.G. Wells story and this image:

[saturn2]

On 1846, a German astronomer discovered the planet Neptune.
Orbital period of Neptune is 165 years.
On 2011, this planet has been once around the Sun.
Distance from Sun to Neptune 4.5 billon kilometers.( 30 AU )

[bystander]

Click to play embedded YouTube video.