Thursday, September 23, 2021

175th Anniversary: Discovery of Neptune

   Neptune - Voyager 2 (29347980845) flatten crop.jpg     Narrow Angle Camera image of the planet Neptune taken by the NASA Voyager 2 spacecraft on 1989 August 20, as the spacecraft approached the planet for an August 25 fly-by, the first and only visit to Neptune by a human-produced space probe. "The Great Dark Spot" and cirrus clouds are seen in the center. "Dark Spot, Jr." is seen rotating into view at the lower left of the disk, with a patch of cirrus clouds (called "Scooter") visible just north of Dark Spot, Jr.

 (Image Sources: NASA, Wikipedia.org, By Justin Cowart - https://www.flickr.com/photos/132160802@N06/29347980845/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=82476611)

By Glenn A. Walsh

Reporting for SpaceWatchtower

September 23 marks the 175th anniversary of the discovery of Neptune (1846 September 23), the eighth planet in our Solar System. It took only one night to discover Neptune, once mathematicians directed astronomers where to look.

Actually, it seems that famous Italian astronomer Galileo Galilei observed Neptune in 1612 and 1613, confusing Neptune for a star that was in conjunction with Jupiter.

For years, astronomers had noticed that there were discrepancies in the orbit of Uranus, the Solar System's seventh planet. In 1821, French astronomer Alexis Bouvard noticed irregularities in the movements of Uranus, in tables he published on the motions of Uranus. He, then, hypothesized that there must be an eighth planet in the Solar System.

Two scientists, independently, determined through mathematical calculations that the orbit of Uranus was being perturbed by an unseen and unknown planet even further from the Sun, using the observations of the late Mr. Bouvard.

British astronomer John Couch Adams, in 1843, began working on the calculations of the Uranus orbit, from Mr. Bovard's data as well as from other information provided by British Royal Astronomer Sir George Airy. John Couch Adams came-up with several estimates for the location of a new planet in 1845 and 1846. Not much was done with Mr. Adams' predictions.

At about the same time, French astronomer Urbain Le Verrier produced his own calculations for the position of the-then unknown planet. Again, there was little interest in searching for a new planet using a telescope.

After evaluating the calculations of both Mr. Adams and Mr. LeVerrier in June of 1846, George Airy convinced British astronomer James Challis to search for the planet. However, he found nothing after searching in August and September of 1846.

Mr. Le Verrier sent a letter, including his calculations, to Johann Galle at the Berlin Observatory. Mr. Galle received the letter on 1846 September 23, then looked for Neptune that night and found it! However, it was through a little bit of luck that he did find the newly-discovered planet, since Mr. Le Verrier's calculations were somewhat in error, by one degree.

Neptune was named for the Roman God of the sea. It is the fourth largest planet, by diameter, in the Solar System, one of the two “ice giants” (the other being Uranus). Neptune is the third most massive planet and the densest of the four giant planets.

Neptune is 17 times the mass of Earth. It is slightly more massive than Uranus, as well as denser and physically smaller than Uranus.

As the farthest major planet from the Sun, it takes Neptune 164.8 years to make one solar revolution.

Neptune's largest moon, Triton, was discovered shortly after the discovery of Neptune. The planet's other 13 known moons were discovered in the 20th century.

Prior to Pluto being reclassified as a Dwarf Planet, Neptune was either the eighth or ninth planet from the Sun, depending on the year. Due to Pluto's eccentric orbit, Pluto was actually closer to the Sun than Neptune from 1979 to 1999. For a 20-year period, during Pluto's 247.94-year orbital period, Pluto is closer to the Sun than Neptune.

Until 1989, a limited amount of information regarding Neptune could be discovered using only Earth-based telescopes. The first NASA probe to fly past Neptune, in August of 1989, would change all that.

The NASA spacecraft, Voyager 2, finished its “Grand Tour of the Planets” when it passed Neptune on 1989 August 25, as well as passing Neptune's largest moon, Triton. Previously, Voyager 2 had passed near Jupiter, Saturn, and Uranus. As part of the “Grand Tour,” Voyager 1 had passed Jupiter, Saturn, and Saturn's largest moon, Titan, earlier.

These fly-bys, of four planets and two natural satellites of two of the planets, by only two spacecraft were made possible by a periodic configuration of the planets during the late 1970s and the 1980s. When NASA discovered this special planetary configuration, early in the Space Age, the space agency arranged for the launch of Voyage 1 and Voyager 2.

Voyager 2's fly-by of Neptune provided a great deal of new information, as well as close-up images, of our Solar System's eighth planet. This included discovery of the previously unknown rings around Neptune. It is said that this fly-by completely re-wrote the science textbooks regarding what is known about Neptune!

Several planetaria and science museums across the country showed a live video feed, via the “NASA Select” satellite television channel, of the Voyager 2 passage of Neptune to the general public. This included Pittsburgh's original Buhl Planetarium and Institute of Popular Science (a.k.a. Buhl Science Center); images from Neptune were shown continuously in Buhl's 250-seat Little Science Theater / Lecture Hall.

Buhl Planetarium had provided similar coverage of Voyager 2's passage of Uranus in January of 1986. Buhl kept the leased satellite dish the next week to provide live coverage of the “Teacher-in-Space” mission of the Challenger Space Shuttle, which tragically ended shortly after launch with the explosion of the space vehicle.

Today, live coverage of a space mission passing a planet, such as the Voyager 2 passage of Neptune, would be provided on an Internet live-stream. During the 1989 August 25 passage of Neptune, the Public Broadcasting Service (PBS) provided live coverage of the passage in a continuous program titled, “Neptune All Night.” In Pittsburgh, this was shown on the city's second educational channel, WQEX-TV 16 (first sister educational television station in the nation, going on the air in 1959).

This month, Neptune is in great view with a telescope, weather-permitting. A telescope or very strong binoculars would be needed to find Neptune, which would appear as a small blue disk, somewhat similar to Uranus.

Neptune reached Opposition, when the Earth lies directly between the Sun and Neptune, on September 14 at 5:00 a.m. Eastern Daylight Saving Time (EDT) / 9:00 Coordinated Universal Time (UTC). Right now, Neptune is visible, again weather-permitting, approximately from local sunset to local sunrise. Neptune is now located in the constellation Aquarius the Water Bearer.

At the time of Opposition, Neptune had a distance of 28.92 Astronomical Units (a.u.) from Earth (the closest to Earth this year); one Astronomical Unit is the average distance between the Sun and the Earth (92.9 million statute miles / 149.6 million kilometers). This distance could also be expressed as 4.0 Light-Hours, the time it takes light and radio waves to travel between the two planets. At the time of Opposition, Neptune had an Apparent Visual Magnitude of +7.8, with a 2.3 arc-seconds disk visible.

As of 2021 September 23, Neptune reaches the local meridian transit point (highest point in the sky for the evening) at ~12:41 a.m. local time. At this time, Neptune's celestial coordinates - Right Ascension: 23 hours, 29 minutes, 39.0 seconds; Declination: -4 degrees, 33 minutes, 3 seconds; Altitude: 35.7 degrees; Azimuth: 222.1 degrees. At this time, Neptune is 28.931 a.u. from Earth, with an Apparent Visual Magnitude of +7.8, and a 2.36 arc-seconds disk visible.

Internet Links to Additional Information ---

 Neptune: Link >>> https://en.wikipedia.org/wiki/Neptune

Neptune Moon Triton: Link >>> https://en.wikipedia.org/wiki/Triton_(moon) 

NASA Voyager 2 spacecraft: Link >>> https://en.wikipedia.org/wiki/Voyager_2 

Grand Tour of the Planets: Link >>> https://en.wikipedia.org/wiki/Grand_Tour_program

 Related Blog-Posts ---

"Undiscovered 'Planet Nine' May Be Cause of Tilt of Our Solar System." Sat. 2016 Oct. 22.

Link >>> http://spacewatchtower.blogspot.com/2016/10/undiscovered-planet-nine-may-be-cause.html

 

"Another Odd Object Found Beyond Neptune!" Tue., 2016 Aug. 16.

Link >>> http://spacewatchtower.blogspot.com/2016/08/another-odd-object-found-beyond-neptune.html

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.

                 Thursday, 2021 September 23.

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           More Astronomy & Science News - SpaceWatchtower Twitter Feed:
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gaw

Glenn A. Walsh, Informal Science Educator & Communicator:
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>>  http://www.planetarium.cc  Buhl Observatory: Link >>>  http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

* Other Walsh Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

Monday, September 20, 2021

Harvest Moon Mon.; Fall Begins Wed.

http://buhlplanetarium.tripod.com/pix/graphics/solsticeimage008.png
This diagram shows the position of the Earth, in relation to the Sun, at the time of the Autumnal Equinox, as well as the other equinox and solstices of the year.
(Graphic Source: ©1999, Eric G. Canali, former Floor Operations Manager of the original Buhl Planetarium and Institute of Popular Science (a.k.a. Buhl Science Center - Pittsburgh's science and technology museum from 1939 to 1991) and Founder of the South Hills Backyard Astronomers amateur astronomy club; permission granted for only non-profit use with credit to author.) 

By Glenn A. Walsh

Reporting for SpaceWatchtower

The Harvest Moon, this year the Full Moon of September, occurs early Monday evening. Fall or Autumn begins less than two days later on Wednesday afternoon.

                                                        Harvest Moon

For the year 2021, the Harvest Moon will be the Full Moon of Monday Evening, September 20, at 7:54 p.m. Eastern Daylight Saving Time (EDT) / 23:54 Coordinated Universal Time (UTC). For farmers eager to finish harvesting their crops, the bright Full Moon which shines on their farms for the several evenings closest to the Autumnal Equinox (the Autumnal Equinox is the astronomical beginning of the season of Autumn or Fall in Earth's Northern Hemisphere) is called the Harvest Moon.

The Harvest Moon is one of the signature astronomical events near the beginning of, or shortly after the beginning of, the Fall season. It is an event particularly anticipated by farmers of both the past and the present. As many crops reach the time of harvest in late Summer and early Autumn, often the work of the harvest has to continue past sunset, which comes earlier and earlier each evening.

Nature has come to the rescue of these farmers, with a bright Full Moon (weather-permitting), which arrives just around the time of sunset, that allows farmers and their staff to continue the harvest after the Sun's light has dissipated. Hence, long-ago this Full Moon came to be known as the Harvest Moon.

For a similar reason, the Full Moon of October is often known as the Hunter's Moon, which allowed Native Americans to continue the hunt after sunset, to begin to store meat for the coming Winter months. However, the Harvest Moon is designated as the closest Full Moon to the Autumnal Equinox, and such a Full Moon does not always occur in September. Every few years the Harvest Moon occurs in October, shortly after the Autumnal Equinox. During those years, the Hunter's Moon occurs in November.

On average, the Moon rises about 50 minutes later each day. However, during the days near the Autumnal Equinox, the Moon rises each day only about 25-to-35 minutes later each day in the U.S.A., and only 10-to-20 minutes later in much of Canada and Europe. Thus, for several days around the time of the Autumnal Equinox, the Harvest Moon appears to rise around the same time each evening (roughly coinciding with local sunset), providing light at the time most needed by farmers.

The reason for this is due to the ecliptic, the apparent path of the Sun, Moon, and planets through Earth's sky, which makes a narrow angle with the horizon this time of year. It is this narrow angle which provides that moonrise occurs around the time of sunset, near the time of the Full Moon of September (or sometimes October). Hence, several days appear to have a rising Full Moon.

Also, at this time of year when farmers need moonlight the most, the Harvest Moon appears larger and more prominent, due to the mysterious but well-known "Moon Illusion" that makes the Moon seem larger when it is near the horizon. And, while near the horizon, the Moon is often reddened by clouds and dust, creating the appearance of a large, rising red ball.

Some even liken a rising Harvest Moon to a rising "Great Pumpkin," of Peanuts comic-strip fame! In the Peanuts' network-television cartoon just before Halloween each year (originally aired on CBS-TV on 1966 October 27) titled, "Its the Great Pumpkin, Charlie Brown", the “Great Pumpkin” rises over the pumpkin patch to provide gifts to all good little boys and girls.

In China and Vietnam, a popular harvest festival is celebrated on the date close to the Autumnal Equinox of the Solar Cycle, as well as close to the Harvest Moon. This Mid-Autumn Festival / Moon Festival dates back more than 3,000 years to Moon worship in China's Shang Dynasty.

Native Americans also called the Full Moon of September the Corn Moon or Barley Moon, as Corn and Barley were among their main crops. Sometimes, the September Full Moon in the Northern Hemisphere is also known as the Fruit Moon.

In the Southern Hemisphere, where Winter is about to turn to Spring, the September Full Moon is known as the Worm Moon, Crow Moon, Sugar Moon, Chaste Moon, or Sap Moon.

The Harvest Moon in the Southern Hemisphere occurs in March or April, with the same advantages to Southern Hemisphere farmers as the Harvest Moon in the Northern Hemisphere.

                                                       Beginning of Autumn

The Autumnal Equinox (also known as the September Equinox), the beginning of the season of Autumn or Fall in the Northern Hemisphere of Earth, occurs Wednesday Afternoon, 2021 September 22 at 3:21 p.m. Eastern Daylight Saving Time (EDT) / 19:21 Coordinated Universal Time (UTC). In Earth's Southern Hemisphere, this equinox marks the astronomical beginning of the season of Spring.

On the day of the Equinox, the Sun appears directly overhead at local Noon on the Equator. At the moment of Equinox, the Northern and Southern Hemispheres of Earth are illuminated equally. And, the time of Equinox is the only time when the Earth Terminator (dividing line on Earth between daylight and darkness) is perpendicular to the Equator.

This, and the reason for seasons on Earth in the first place, is due to the fact that Earth rotates on its axis, which is tilted at an approximate 23.44-degree angle from the ecliptic, the plane of the Earth's orbit around the Sun. As the Earth revolves around the Sun, this axial tilt causes one hemisphere of the planet to receive more direct solar radiation during that hemisphere's season of Summer and much less direct solar radiation about a half-year later during that hemisphere's season of Winter. As mentioned, during an Equinox [about half-way between Summer and Winter (Autumnal Equinox), and about half-way between Winter and Summer (Vernal Equinox)] both planetary hemispheres receive an equal amount of solar radiation. 

Although "Equinox" in Latin means equal-night, the day of the Equinox does not actually have an equal amount of daylight and nightfall, as it appears on the Earth's surface. If the Sun was just a pin-point of light in our sky, as all other stars appear, day and night would be equal.

But, because the Sun is a disk, part of the Sun has risen above the horizon before the center of the Sun (which would be the pin-point of light); so there are extra moments of light on the Equinox. Likewise, part of the Sun is still visible, after the center of the Sun has set.

Additionally, the refraction of sunlight by our atmosphere causes sunlight to appear above the horizon, before sunrise and after sunset.

September 25 will mark the Equilux ("equal-light"), the actual day with equal hours and minutes of the Sun above the horizon, and equal hours and minutes of the Sun below the horizon. The Equilux occurs twice each year, approximately 3-to-4 days before the Vernal Equinox, when Spring begins,  and 3-to-4 days after the Autumnal Equinox, after Autumn or Fall has begun.

An urban legend that has been making the rounds for decades has it that eggs can be stood on their ends only during an Equinox, whether the Vernal Equinox in the Spring or the Autumnal Equinox in the Fall. This is completely false. Depending greatly on the size and shape of the particular egg, eggs can be stood on their ends any day of the year! Astronomy has nothing to do with whether an egg can stand on its end. If an egg can stand on its end on the Equinox (and, due to the shape and size of some eggs, this is not even possible), it can stand the same way any other day of the year.

In the last few years, with the help of the Internet and Social Media, another urban legend has become prevalent. Now it is claimed that brooms can stand, on their own, on their bristles, only on an Equinox day. This is also false. Again, as with eggs, if a broom can stand on its bristles by itself (this usually only works with newer brooms, with more even bristles) on an Equinox, it can do so any day of the year!

September 22 is also designated as the annual Falls Prevention Awareness Day for this year.

 Internet Links to Additional Information ---

Harvest Moon: Link >>> https://science.nasa.gov/science-news/science-at-nasa/2013/16sep_harvestmoon/ 

Native American Full Moon Names: Link >>> https://earthsky.org/astronomy-essentials/full-moon-names/ 

Mid-Autumn Festival / Moon Festival: Link >>> https://en.wikipedia.org/wiki/Mid-Autumn_Festival

Autumnal Equinox: Link >>> http://scienceworld.wolfram.com/astronomy/AutumnalEquinox.html


Season of Autumn or Fall: Link >>> http://en.wikipedia.org/wiki/Autumn

Equinox: Link >>> http://en.wikipedia.org/wiki/Equinox


Equilux: Link >>> https://darkskydiary.wordpress.com/2010/03/20/equinox-equilux-and-twilight-times/


Earth's Seasons: Link >>> http://en.wikipedia.org/wiki/Season

Tilt of a planet's axis: Link >>> http://en.wikipedia.org/wiki/Axial_tilt

Urban legend of eggs and brooms standing on their own, only on an Equinox:
Link >>> http://www.snopes.com/science/equinox.asp

Falls Prevention Awareness Day: Link >>> https://nationaltoday.com/falls-prevention-awareness-day/

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.

                 Monday, 2021 September 20.

                             Like This Post?  Please Share!

           More Astronomy & Science News - SpaceWatchtower Twitter Feed:
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        Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks

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gaw

Glenn A. Walsh, Informal Science Educator & Communicator:
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>>  http://www.planetarium.cc  Buhl Observatory: Link >>>  http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

* Other Walsh Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

Wednesday, September 1, 2021

Astro-Calendar: 2021 Sept. / 1st All-Civilian SpaceX Launch Sept. 15

Crew Dragon Resilience Crew-1.jpg

Image of SpaceX Crew Dragon Resilience capsule at the Kennedy Space Center. Four civilian, SpaceX astronauts will launch in this capsule for a three-day mission orbiting Earth. More information: Link >>> https://buhlplanetarium4.tripod.com/astrocalendar/2021.html#inspiration4

(Image Sources: SpaceX, Wikipedia.org, By SpaceX - https://images.nasa.gov/details-KSC-20201105-PH-SPX01_0002, CC0, https://commons.wikimedia.org/w/index.php?curid=95876932)

Astronomical Calendar for 2021 September ---
Link >>> https://buhlplanetarium4.tripod.com/astrocalendar/2021.html#sep

 Related Blog Post ---

"Astro-Calendar 2021 Aug. / Update: Boeing Starliner Launch Delayed Indefinitely." Sun., 2021 Aug. 1.

Link >>> https://spacewatchtower.blogspot.com/2021/08/astro-calendar-2021-aug-boeing.html

Source: Friends of the Zeiss.
            Wednesday, 2021 September 1.

                             Like This Post?  Please Share!

            More Astronomy & Science News - SpaceWatchtower Twitter Feed:
            Link >>> https://twitter.com/spacewatchtower

        Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks

                Want to receive SpaceWatchtower blog posts in your in-box ?
                Send request to < spacewatchtower@planetarium.cc >.

gaw

Glenn A. Walsh, Informal Science Educator & Communicator:
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>>  http://www.planetarium.cc  Buhl Observatory: Link >>>  http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

* Other Walsh Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html