Thursday, December 21, 2017

Winter Begins; Ursid Meteors Peak Friday

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 Winter Solstice, as well as the other solstice and equinoxes of the year, in Earth's Northern Hemisphere.
(Graphic Source: ©1999, Eric G. Canali, former Floor Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science 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 season of Winter, in the Northern Hemisphere of Earth, begins at the moment of the Winter / December Solstice, Thursday, 2017 December 21 at 11:28 a.m. Eastern Standard Time (EST) / 16:28 Coordinated Universal Time (UTC)---the moment of the posting of this blog-post. This moment also marks the astronomical beginning of the Summer season in the Southern Hemisphere.

Almost 24 hours later, Friday morning will mark the peak time for the annual Ursid Meteor Shower; of course dark skies are needed to actually see meteors. This meteor shower peaks Friday, 2017 December 22 at 10:00 a.m. EST / 15:00 UTC.

                                               Winter Solstice 2017

In etymology, the word solstice comes from the Latin terms sol (Sun) and sistere (to stand-still). In ancient times, astronomers / astrologers / priests recognized that one day of the year when the Sun would appear to reach its lowest point in the sky for the entire year. The motion of the Sun's apparent path in the sky (what is known astronomically today as the Sun's declination) would cease on this day, and the Sun would appear to stand-still, before reversing direction.

With our Gregorian Calendar, this usually occurs on, or very close to, December 21. In ancient times, when people used the Julian Calendar, the Winter Solstice was on, or very close to, December 25, what we now know as Christmas Day. Mid-Winter festivals, at the time of the Winter Solstice, were common in ancient times. Instead of competing with these traditions, the early Roman Catholic Church Christianized the Winter festivals by observing the birth of Jesus Christ on December 25 (the actual birth date of Jesus was probably in September).

Today, we know that, while the Sun does have motions, it is actually the motion of the Earth, tilted on its axis 23.44 degrees from the plane of our Solar System while revolving around the Sun, that causes the Earth's seasons. Hence, as the Earth arrives at the point in its orbit around the Sun, where the south polar axis is most directly inclined toward the Sun (thus, the Sun appears at its lowest point for the year in the Northern Hemisphere sky) around December 21, this marks the Winter Solstice in the Northern Hemisphere (and the Summer Solstice in the Southern Hemisphere).

Alternately around June 21, the Summer Solstice marks the beginning of Summer in the Northern Hemisphere (and this date also marks the Winter Solstice, which is the beginning of Winter in the Southern Hemisphere) as the Earth reaches the point in its orbit where the north polar axis is most directly inclined toward the Sun.

The day of the December Solstice is the only time of the year when the Sun reaches the point of Local Solar Noon at the South Pole. Conversely, it is also the only time of the year when Local Solar Midnight occurs at the North Pole. And, of course, it is the reverse during the June Solstice: the only time the Sun reaches the point of Local Solar Noon at the North Pole and the only time when Local Solar Midnight occurs at the South Pole.

Although the Winter months in the Northern Hemisphere are known for the year's coldest weather, the Earth is actually at the point in its orbit closest to the Sun (astronomically known as the point of perihelion) on or very near January 2. The Earth is farthest from the Sun, each year shortly after the Northern Hemisphere's Summer Solstice, on or very near July 5 (the point of aphelion).

Solar radiation, and hence heat from the Sun, to warm an Earth hemisphere depends on the length of daylight and the angle of the Sun above the horizon. The tilt of the planet's axis toward the Sun determines the additional and more direct solar radiation received by a planet's northern or southern hemisphere, and hence, the warmer season of the respective hemisphere.

The Earth's perihelion in January and aphelion in July is due to the elliptical nature of the Earth's orbit around the Sun. Perihelion and aphelion would not occur if the Earth's orbit was a true circle.

Since the Earth is closest to the Sun near the beginning of the Northern Hemisphere's Winter Season, the Earth, then, moves faster in its orbit around the Sun than it moves in July, making the Northern Hemisphere's Winter a shorter season than Summer. Winter will last for only 89 days, while this past-Summer lasted nearly 93 days. This is one of the observed consequences of Johannes Kepler's Laws of Planetary Motion, which he published at the beginning of the 17th century.

The day of the Winter Solstice is known as the “shortest day of the year” and the “longest night of the year” as the Sun shines on the Northern Hemisphere for the shortest length of time for the entire year, on this day. For this reason, Homeless Persons' Memorial Day is commemorated on December 21.

Interestingly, the climate of a locale in the Southern Hemisphere is, on average, slightly milder than a location at the same latitude in the Northern Hemisphere, because the Southern Hemisphere has significantly more ocean water and much less land. Water warms-up and cools-down more slowly than does land. The only exception is the Antarctic, which is colder than the Northern Hemisphere's Arctic region, possibly because most of the Arctic region is covered with water (although, often frozen water on the surface, but liquid water beneath the ice) while Antarctica is mostly a land mass.

                                              Ursid Meteor Shower

Almost 24 hours after the Winter Solstice comes the peak of the annual Ursid Meteor Shower, which actually begins on December 17 and usually lasts about a week ending December 24, 25, or 26. The Ursids seem to comprise a narrow stream of debris originating from Comet Tuttle. Hence, it is difficult to see Ursid meteors outside of a 12-hour window before and after the peak, where possibly 12 meteors per-hour could be seen, under ideal conditions.

The Ursid Meteor Shower is so-named because most meteors appear to radiate from a point near the Star Beta Ursae Minoris (apparent meteor shower radiant) in the Constellation Ursa Minor (better known as the asterism the “Little Dipper”), which is the brightest star in the bowl of the Little Dipper. Some people call these meteors “Ursids,” in an attempt to emphasize that their apparent radiant is Ursa Minor, not Ursa Major (the asterism the “Big Dipper”).

However, you should not, necessarily, be looking only at the Little Dipper when looking for meteors in this shower. Meteors can appear in any part of the sky at any time (although a meteor's tail may tend to point back toward the radiant).

Of course meteor showers, like all celestial observations, are weather-permitting. If there are more than a few clouds in the sky, meteors will be much more difficult to find. Clear skies are not always available in the skies of late Autumn and early Winter. And, it is always best to get away from city lights, for the opportunity to see the smaller, dimmer meteors. As always, the best time to view any meteor shower is between local midnight and local dawn, when the Earth is actually rotating into the stream of meteoric debris.

Binoculars and telescopes are not very useful for finding meteors. Meteors streak across the sky in a very short period of time, far too short to aim binoculars or a telescope. So, the best way to view a meteor shower is to lie on a blanket or beach towel on the ground, or use a reclining a chair, outdoors in an area with a good view of the entire sky (with few obstructions such as buildings, trees, or hills), and keep scanning the entire sky.

So, if you go out to see the Ursid Meteor Shower, start looking for meteors around local midnight, or perhaps a little later. Make sure you have a good site where you can see most of the sky, and that sky is relatively clear. Be sure to dress properly for the early morning temperatures, now that we are at the very beginning of Winter.

And, you want to go out ahead of time, before you actually start looking for meteors, to get your eyes accustomed to the dark sky. Dark-adapting your eyes for meteor-watching could take up to a half-hour.

Special Thanks: Eric G. Canali, former Floor Manager of Pittsburgh's original Buhl Planetarium and Institute of Popular Science and Founder of the South Hills Backyard Astronomers amateur astronomy club.

Internet Links to Additional Information ---

More on the Winter Solstice:
Link 1 >>> http://scienceworld.wolfram.com/astronomy/WinterSolstice.html
Link 2 >>> http://en.wikipedia.org/wiki/Winter

More on a Solstice: Link >>> http://en.wikipedia.org/wiki/Solstice

Popular Winter Planetarium Sky Shows Shown at Pittsburgh's original Buhl Planetarium and Institute of Popular Science (1939 to 1991), including full scripts of each show:
The Star of Bethlehem >>> http://buhlplanetarium3.tripod.com/skyshow/bethlehem/
The Stars of Winter >>> http://buhlplanetarium3.tripod.com/skyshow/winter/

More on calendars ---
       Gregorian Calendar: Link >>> http://en.wikipedia.org/wiki/Gregorian_calendar
       Julian Calendar: Link >>> http://en.wikipedia.org/wiki/Julian_calendar

More on the Ursid Meteor Shower: Link >>> http://en.wikipedia.org/wiki/UrsidsA

More on the Homeless Persons' Memorial Day:
Link >>> http://nationalhomeless.org/about-us/projects/memorial-day/

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2017 December 21.

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Glenn A. Walsh, Project Director, Friends of the Zeiss: < http://buhlplanetarium.tripod.com/fotz/ >
& SpaceWatchtower Editor / Author: < http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/ >
Electronic Mail - < gawalsh@planetarium.cc >
Astronomy Links: < http://buhlplanetarium.tripod.com/#astrolinks >
Science Links: < http://buhlplanetarium.tripod.com/#sciencelinks >
SpaceWatchtower Twitter News Feed: < https://twitter.com/spacewatchtower >
SpaceWatchtower Blog: < http://spacewatchtower.blogspot.com/ >
LibraryWatchtower Blog: < http://librarywatchtower.blogspot.com >
TransportWatchtower Blog: < http://transportwatchtower.blogspot.com  >
South Hills Backyard Astronomers Blog: < http://shbastronomers.blogspot.com/ >
Barnestormin Blog: Writing, Essays, Pgh. News, etc.: < http://www.barnestormin.blogspot.com/ >
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
  < http://www.planetarium.cc >
* Adler Planetarium, Chicago:
  < http://adlerplanetarium.tripod.com >
* Astronomer, Educator, Optician John A. Brashear:
  < http://johnbrashear.tripod.com >
* Andrew Carnegie & Carnegie Libraries:
  < http://www.andrewcarnegie.cc >
* Civil War Museum of Andrew Carnegie Free Library:
  < http://garespypost.tripod.com >
Duquesne Incline cable-car railway, Pittsburgh:
  < http://inclinedplane.tripod.com >
* Public Transit:
  < http://andrewcarnegie2.tripod.com/transit >

Thursday, December 7, 2017

Nano-Space Probes to Star Alpha Centauri by Laser-Sail ?


One possible concept for a Laser-sail mounted on a nano-space probe, which could reach
the Alpha Centauri star system, possibly as early as mid-century.
(Image Sources: Wikipedia.org , By Kevin Gill from Nashua, NH, United States - Solar Sail, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=42599221 )

By Glenn A. Walsh
Reporting for SpaceWatchtower

Last month, SpaceWatchtower talked about Lasers in Space ? (posted November 13; reference Internet link near the end of this blog-post). Today, SpaceWatchtower looks at a very ambitious proposal to use Lasers for space propulsion, for very small space probes to reach nearby star systems.

Known as Breakthrough Starshot, this is one of four projects in Breakthrough Initiatives. The other three projects are ---

  • Breakthrough Watch – Astronomical program to produce new technologies to help determine if life exists on Earth-like planets in nearby solar systems.
  • Breakthrough Listen – Search for radio and optical signals from extra-terrestrial civilizations.
  • Breakthrough Message – Competition to create a message about Earth, life, and humanity that could be transmitted, received, and understood by an extra-terrestrial civilization. This project includes a public debate regarding the ethics of sending messages beyond the Earth.

Breakthrough Initiatives was launched “in 2015 by Yuri and Julia Milner to explore the Universe, seek scientific evidence of life beyond Earth, and encourage public debate from a planetary perspective,” according to the Breakthrough Initiatives Internet web-site. A Russian entrepreneur, venture capitalist, and physicist, Yuri Milner has invested several hundred million dollars into these projects.

Pete Worden, former University of Arizona Astronomy Professor, NASA Ames Research Center Director, and Brig. General of the United State Air Force, was introduced as the new Breakthrough Prize Foundation Chairman (and Executive Director of Breakthrough Initiatives and Breakthrough Starshot) at a news conference held at the Royal Society in London when Breakthrough Initiatives was announced on 2015 July 20 (46th anniversary of the U.S. Apollo 11 mission, which included the first persons to land and walk on the Moon). Almost a year later on 2016 April 12 (the 55th anniversary of the Russian Vostock 1 mission, which included the first person to enter Outer Space and orbit the Earth, and the 35th anniversary of the first launch of the U.S. Space Shuttle), the Breakthrough Starshot project was announced at an event in New York City.

Breakthrough Starshot is a research and engineering project which envisions sending nano-space probes, called “StarChips,” to nearby star systems. In addition to a much closer look at nearby stars, a major objective of such a mission would be to fly past, and possibly photograph, any Earth-like worlds that may exist in the star system.

Each StarChip would be a very small, centimeter-sized vehicle weighing only a few grams. From a “mother-ship” in Earth orbit, 1000 of these StarChips would be launched toward the target star system.

Each StarChip would include 4 sub-gram-scale digital cameras, 4 sub-gram-scale central processing units, 4 sub-gram-scale photonic Laser thrusters, 150-milligram atomic battery (powered by plutonium-238 or americium-240), protective coating (to protect from dust collisions and atomic particle erosion), and a Laser light-sail (no larger than 13 x 13 feet / 4 x 4 meters).

A square-kilometer phased-array of ground-based, 10-kilowatt Lasers would then focus Laser-light on each StarChip's Laser-sail. It is estimated that the Lasers would accelerate each StarChip to the target speed within ten minutes. A Laser-sail on each StarChip may be circular, with a diameter of 5 meters.

Propulsion of these spacecraft by Laser-sail will not be easy or inexpensive. Hence, the necessity to have all on-board equipment miniaturized and engineered to survive the rigors of high-speed interstellar travel.

A Laser with a gigawatt of power (approximating the output of a large nuclear power plant) would be necessary to power 1000 such space probes during a single deployment. And, atmospheric turbulence would add difficulty to focusing Laser-light onto the Laser-sails.

In the literature I read regarding this project, there was no mention of whether a Laser in Earth orbit could solve the atmospheric turbulence problem. Of course, some national governments may be concerned with having such a strong Laser in Earth orbit, assuming the technical problems with such an installation could be overcome.

The Alpha Centauri trinary star system, being the closest star system to Earth, is the logical first target of such spacecraft. The 1960s science-fiction television series, “Lost in Space,” portrayed a crewed U.S. space mission launched in 1997 with the goal of being the first such Earth mission to reach a habitable planet outside of our Solar System, one orbiting Alpha Centauri.

Alpha Centauri (which includes the stars Alpha Centauri A & B) is 4.37 light-years from Earth. The third star in the system which is even closer to Earth, Proxima Centauri, is 4.25 light-years from Earth.

Proxima Centauri is of particular interest to scientists. In August of 2016, the European Southern Observatory announced the discovery of an exo-planet a little larger than Earth and within the habitable zone of Proxima Centauri. Known as Proxima Centauri b, it is the closest known exo-planet to Earth.

At the beginning of this year, Breakthrough Initiatives entered into an agreement with the European Southern Observatory to provide funding for upgrades to the Observatory's Very Large Telescope (VLT) in Chile. It is hoped that such upgrades will help find additional planets in the Alpha Centauri star system. Due to its location in the sky, which prevents most of Earth's Northern Hemisphere viewers from directly seeing it, Alpha Centauri can best be studied by observatories in the Southern Hemisphere.

The StarChip nano-spacecraft would be propelled by Lasers toward the Alpha Centauri star system at speeds of between 15 per-cent and 20 per-cent of the Speed of Light (Speed of Light: 186,282 statute miles per second / 299,792 kilometers per second). At that speed, each StarChip would take between 20 and 30 years to reach Alpha Centauri.

While in the Alpha Centauri star system, data would be transmitted back to Earth using a compact Laser communication system. The Laser-sail would be used as the transmitting antenna and the Earth-based Laser propulsion array would be the receiver. At 4.37 light-years away, then Laser communication would take 4.37 years to reach Earth.

Once a successful mission to Alpha Centauri is completed, technology may advance far enough to attempt to send StarChips to even farther star systems. With currently conceived StarChips technology, star systems that may be within reach of such an effort would include ---

  • Sirius A (brightest star in the night sky), 8.58 light-years from Earth; StarChips travel time: 68.90 years.
  • Procyon A, 11.44 light-years from Earth; StarChips travel time: 154.06 years.
  • Vega, 25.02 light-years from Earth; StarChips travel time: 167.39 years.
  • Altair, 16.69 light-years from Earth; StarChips travel time: 176.67 years.

Other possible uses for StarChips include ---

  • Exploration in our Solar System.
  • Detection of asteroids that cross Earth's orbit, that risk hitting the Earth sometime in the future.
  • Launch of a “Genesis” probe (proposed by German physicist Claudius Gros) to establish a biosphere of unicellular microbes on otherwise only transiently habitable exo-planets (such a Genesis probe would only travel at 0.3 per-cent of the Speed of Light, so the probe could be decelerated when it reached the target exo-planet by way of a magnetic sail).

Yuri Milner has provided Breakthrough Starshot an initial funding of $100 million for research into how to engineer such an ambitious proposal. He currently estimates that the entire Breakthrough Starshot project may cost between $5 and $10 billion. He believes the first StarChips could launch as early as the year 2036.

Special Note: Last month, SpaceWatchtower talked about Lasers in Space ? (posted November 13; reference Internet link near the end of this blog-post), which included information regarding the-then just-launched NanoRacks CubeSats satellites, which will help set-up a Laser-based, high-speed data communication system in Outer Space. Andrea Boyd (International Space Station Flight Operations Engineer at the European Astronaut Centre in Cologne, Germany) commented, on the November 13 post, saying that the International Space Station already has two operating Laser systems: optical [Optical Payload for Lasercomm Science (OPALS)] and LIDAR [Cloud-Aerosol Transport System (CATS)] (reference Internet links to more information on these two Laser systems near the end of this blog-post).

Internet Links to Additional Information ---

Breakthrough Starshot---
Link 1 >>> http://breakthroughinitiatives.org/initiative/3
Link 2 >>> https://en.wikipedia.org/wiki/Breakthrough_Starshot

Star Alpha Centauri: Link >>> https://en.wikipedia.org/wiki/Alpha_Centauri

Star Proxima Centauri: Link >>> https://en.wikipedia.org/wiki/Proxima_Centauri

Exo-Planet Proxima Centauri b: Link >>> https://en.wikipedia.org/wiki/Proxima_Centauri_b

Optical PAload for Lasercomm Science (OPALS) on the International Space Station (ISS):
Link >>> https://www.nasa.gov/mission_pages/station/research/experiments/861.html

Cloud-Aerosol Transport System (CATS) on the International Space Station (ISS):
Link >>> https://cats.gsfc.nasa.gov/

Related Blog Posts ---

"Lasers in Space ?" 2017 November 13.

Link >>> http://spacewatchtower.blogspot.com/2017/11/lasers-in-space.html

 

"Laser-Propelled Nano-Space Probe to Reach Alpha Centauri in 20 Years?"

2016 April 14.

Link >>> http://spacewatchtower.blogspot.com/2016/04/laser-propelled-nano-space-probe-to.html


Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2017 December 7.

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gaw

Glenn A. Walsh, Project Director, Friends of the Zeiss: < http://buhlplanetarium.tripod.com/fotz/ >
& SpaceWatchtower Editor / Author: < http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/ >
Electronic Mail - < gawalsh@planetarium.cc >
Astronomy Links: < http://buhlplanetarium.tripod.com/#astrolinks >
Science Links: < http://buhlplanetarium.tripod.com/#sciencelinks >
SpaceWatchtower Twitter News Feed: < https://twitter.com/spacewatchtower >
SpaceWatchtower Blog: < http://spacewatchtower.blogspot.com/ >
LibraryWatchtower Blog: < http://librarywatchtower.blogspot.com >
TransportWatchtower Blog: < http://transportwatchtower.blogspot.com  >
South Hills Backyard Astronomers Blog: < http://shbastronomers.blogspot.com/ >
Barnestormin Blog: Writing, Essays, Pgh. News, etc.: < http://www.barnestormin.blogspot.com/ >
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
  < http://www.planetarium.cc >
* Adler Planetarium, Chicago:
  < http://adlerplanetarium.tripod.com >
* Astronomer, Educator, Optician John A. Brashear:
  < http://johnbrashear.tripod.com >
* Andrew Carnegie & Carnegie Libraries:
  < http://www.andrewcarnegie.cc >
* Civil War Museum of Andrew Carnegie Free Library:
  < http://garespypost.tripod.com >
Duquesne Incline cable-car railway, Pittsburgh:
  < http://inclinedplane.tripod.com >
* Public Transit:
  < http://andrewcarnegie2.tripod.com/transit >

Friday, December 1, 2017

Astronomical Calendar: 2017 December


The largest and closest Full Moon of 2017 comes on December 3 at 10:47 a.m. EST / 15:47 UTC;
some people refer to this as a so-called "Super-Moon." Consequently, large tides along ocean coast-lines are predicted due to a Lunar Perigee the next day, at 4:00 a.m. EST / 9:00 UTC. This particular photograph shows the "Super-Moon" of 2016 November 14.
(Image Sources: Wikipedia.org , By Tomruen - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=53147136 )

Astronomical Calendar for 2017 December: 
Link >>> http://buhlplanetarium4.tripod.com/astrocalendar/2017.html#dec

 Related Blog Post ---


"Astronomical Calendar: 2017 November." 2017 Nov. 1.

Link >>> https://spacewatchtower.blogspot.com/2017/11/astronomical-calendar-2017-november.html


Source: Friends of the Zeiss.
              2017 December 1.

                             Like This Post? - Please Share!

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gaw

Glenn A. Walsh, Project Director, Friends of the Zeiss: < http://buhlplanetarium.tripod.com/fotz/ >
& SpaceWatchtower Editor / Author: < http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/ >
Electronic Mail - < gawalsh@planetarium.cc >
Astronomy Links: < http://buhlplanetarium.tripod.com/#astrolinks >
Science Links: < http://buhlplanetarium.tripod.com/#sciencelinks >
SpaceWatchtower Twitter News Feed: < https://twitter.com/spacewatchtower >
SpaceWatchtower Blog: < http://spacewatchtower.blogspot.com/ >
LibraryWatchtower Blog: < http://librarywatchtower.blogspot.com >
TransportWatchtower Blog: < http://transportwatchtower.blogspot.com  >
South Hills Backyard Astronomers Blog: < http://shbastronomers.blogspot.com/ >
Barnestormin Blog: Writing, Essays, Pgh. News, etc.: < http://www.barnestormin.blogspot.com/ >
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
  < http://www.planetarium.cc >
* Adler Planetarium, Chicago:
  < http://adlerplanetarium.tripod.com >
* Astronomer, Educator, Optician John A. Brashear:
  < http://johnbrashear.tripod.com >
* Andrew Carnegie & Carnegie Libraries:
  < http://www.andrewcarnegie.cc >
* Civil War Museum of Andrew Carnegie Free Library:
  < http://garespypost.tripod.com >
Duquesne Incline cable-car railway, Pittsburgh:
  < http://inclinedplane.tripod.com >
* Public Transit:
  < http://andrewcarnegie2.tripod.com/transit >