* Astronomy

Blobrana · L

RE: Neptune

Blobrana · L

Rings of Neptune

Blobrana · L

RE: Neptune

Blobrana · L

Neptune Completes Its First Circuit Around The Sun Since Its Discovery

These four images of Neptune were taken by NASA's Hubble Space Telescope during the planet's 16-hour rotation. The snapshots were taken at roughly four-hour intervals, offering a full view of the blue-green planet. Today marks Neptune's first orbit around the Sun since it was discovered nearly 165 years ago. These images were taken to commemorate the event.
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Blobrana · L

Neptune's birthday and a beautiful piece of maths

Neptune is about to celebrate its first birthday. On 12 July it will be exactly one Neptunian year - or 164.79 Earth years - since its discovery on 24 September 1846. But why do we still know so little about the distant planet?
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Blobrana · L

Neptune begins to give up its secrets

The blue planet, the farthest out in the Solar System, remains one of Earth's most mysterious neighbours, but scientists now know one thing that they hadn't for the past 165 years: the precise length of its day.
Earlier estimates had set that figure at about 16 hours and 6 minutes. But, in a paper in Icarus, Erich Karkoschka, a planetary scientist at the University of Arizona in Tucson, now pegs it at 15 hours, 57 minutes and 59 seconds.
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Date: Jul 5 17:39 2011

Yes, the heliocentric R.A. is the same on 12th July as on the date of discovery; but Neptune orbits the Solar System barycentre, not the Sun.

These two graphs here and here make this very clear, I think. This is why we should use barycentric longitude, not heliocentric.

The Sun also moves around the Solar System barycentre, and is in a different position this July to where it was in 1846, by 300,000 miles. By taking your coordinates from the Sun, you would be making the same mistake as taking them from Earth (albeit a lot subtler).

Ed ~ Ahh, yes, barycentric longitude would be better

Blobrana · L

@Bob D

Yes, there is a bit of confusion with the dates. It seems that Neptune will not appear at its exact discovery position in our sky because the Earth will be in a different location in its 365.25-day orbit.

Observer Location: Sun (body center) [500@10]   (Heliocentric)
QUANTITIES=1,20,29

Date__(UT)__HR:MN     R.A._(ICRF/J2000.0)_DEC    delta (AU)    deldot KM/S  Cnst
1846-Sep-23 00:00     22 05 39.10 -12 16 54.3 30.0114878939835  -0.0576715  Aqr  (Discovery Date)
2011-Jul-12 00:00     22 05 39.22 -12 16 55.0 30.0079478455979  -0.0545865  Aqr  (1st Complete Orbit!)
2176-May-04 00:00     22 05 39.33 -12 16 56.6 30.0109537617283  -0.0521759  Aqr

Source

Blobrana · L

On the evening of July 12 in this month's Colorado sky, Neptune, the second planet to be discovered in historic times, will finally complete only its first 165-year orbit about the sun since its discovery in 1846.
Neptune currently rises about midnight and is located in the constellation of Aquarius just inside the Aquarius/Capricornus border. It is visible as a bluish eighth magnitude binocular object.
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Blobrana · L

Clocking Neptune's Spin

Neptune-features_web.preview.jpg

In this image, the colours and contrasts were modified to emphasize the planet's atmospheric features. The winds in Neptune's atmosphere can reach the speed of sound or more. Neptune's Great Dark Spot stands out as the most prominent feature on the left. Several features, including the fainter Dark Spot 2 and the South Polar Feature, are locked to the planet's rotation, which allowed Karkoschka to precisely determine how long a day lasts on Neptune. (Image: Erich Karkoschka)