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Episode 3 - Astronomical Units and Astronomical Apps

(Pawling Public Radio 103.7 FM)

Welcome to The Astronomical Almanac.
I am your host - Bob Antol. I am a local astronomer in the Pawling area (Poughquag specifically), with a passion for all things astronomical.

Astronomy is the branch of science that deals with celestial objects, space, and the physical universe as a whole. This show, The Astronomical Almanac, will make you more comfortable with these concepts so you will be able to recognize, grasp and appreciate the universe around us.

This is the The Astronomical Almanac on WPWL - Pawling Public Radio - 103.7 FM - Pawling, New York.
And today's episode is entitled Astronomical Units and Astronomical Apps.


Old Business


  >   The first segment of the program is something I call Old Business. This will be devoted to answering any questions from the previous episodes or to correct anything I may have said in error.

Last week: Telescopes.
This week: Apps to help you find fascinating objects.
In the coming weeks: The wonders of the heavens to look at.

The Astronomical Almanac will have the following format:

  1. Old Business - this segment here.
  2. Expanding Your Astronomical Vocabulary - devoted to defining astronomical terms.
  3. What's Up in the Sky This Week? - from planets to meteor showers to the space station and more!
  4. Astronomical Curiosities - exploring unique aspects of the world of astronomy.
  5. Did You Know? - a fun-filled trivia section.
  6. The Buffer Zone - personal recollections from my life as an amateur astronomer.

  <   This concludes the Old Business portion of the program. Next up ... Expanding Your Astronomical Vocabulary ...


Expanding Your Astronomical Vocabulary


Astronomical Units


  >   Each week, a term (or two) will be defined laying the groundwork for a more general understanding of astronomy. This week, in Expanding Your Astronomical Vocabulary, I will be discussing ...

Distances in space are often measured in Astronomical units (AU), light-years (ly), or parsecs (pc).

An Astronomical unit is the average distance from Earth to the Sun, about 93 million miles (150 million km), and is used to measure relatively short distances, such as those between the Sun and its planets or between the stars in a binary system.

    Planet (or Dwarf Planet) Distance from the Sun
    (Astronomical Units
    miles
    km)
    Period of Revolution Around the Sun
    (1 planetary year)
    Period of Rotation
    (1 planetary day)
    Mass
    (kg)
    Diameter
    (miles
    km)
    Apparent size
    from Earth
    Temperature
    (K
    Range or Average)
    Number
    of Moons
    Mercury 0.39 AU
    36 million miles
    57.9 million km
    87.96 Earth days 58.7 Earth days 3.3 x 1023 3,031 miles
    4,878 km
    5-13 arc seconds 100-700 K
    mean=452 K
    0
    Venus 0.723 AU
    67.2 million miles
    108.2 million km
    224.68 Earth days 243 Earth days 4.87 x 1024 7,521 miles
    12,104 km
    10-64 arc seconds 726 K 0
    Earth 1 AU
    93 million miles
    149.6 million km
    365.26 days 24 hours 5.98 x 1024 7,926 miles
    12,756 km
    Not Applicable 260-310 K 1
    Mars 1.524 AU
    141.6 million miles
    227.9 million km
    686.98 Earth days 24.6 Earth hours
    =1.026 Earth days
    6.42 x 1023 4,222 miles
    6,787 km
    4-25 arc seconds 150-310 K 2
    Jupiter 5.203 AU
    483.6 million miles
    778.3 million km
    11.862 Earth years 9.84 Earth hours 1.90 x 1027 88,729 miles
    142,796 km
    31-48 arc seconds 120 K
    (cloud tops)
    69
    Saturn 9.539 AU
    886.7 million miles
    1,427.0 million km
    29.456 Earth years 10.2 Earth hours 5.69 x 1026 74,600 miles
    120,660 km
    15-21 arc seconds
    excluding rings
    88 K 61
    Uranus 19.18 AU
    1,784.0 million miles
    2,871.0 million km
    84.07 Earth years 17.9 Earth hours 8.68 x 1025 32,600 miles
    51,118 km
    3-4 arc seconds 59 K 27
    Neptune 30.06 AU
    2,794.4 million miles
    4,497.1 million km
    164.81 Earth years 19.1 Earth hours 1.02 x 1026 30,200 miles
    48,600 km
    2.5 arc seconds 48 K 14
    Pluto (a dwarf planet) 39.53 AU
    3,674.5 million miles
    5,913 million km
    247.7 years 6.39 Earth days 1.29 x 1022 1,413 miles
    2,274 km
    0.04 arc seconds 37 K 5
    Planet (or Dwarf Planet) Distance from the Sun
    (Astronomical Units
    miles
    km)
    Period of Revolution Around the Sun
    (1 planetary year)
    Period of Rotation
    (1 planetary day)
    Mass
    (kg)
    Diameter
    (miles
    km)
    Apparent size
    from Earth
    Temperature
    (K
    Range or Average)
    Number of Moons

Light-year is the distance light travels in one year, which is about 5.88 trillion miles or almost 800 times the diameter of the solar system. The nearest star (Proxima Centauri) is 4.22 light-years away, while the nearest spiral galaxy lies about 2.5 million light-years from Earth. The speed of light is 186,000 miles per second or 299,792,458 meters per second.

Light is the fastest-moving stuff in the universe. If you could travel at the speed of light, you would be able to circle the Earth's equator about 7.5 times in just one second.

    For general reference, there are ^63,000 astronomical units in one light-year, and 63,000 inches (160,000 cm) in one mile (1.6 km).
    This wonderful coincidence enables us to bring the light-year down to Earth. If we scale the astronomical unit (AU) - the Earth-sun distance - at one inch, then the light-year on this scale represents one mile (1.6 km).
    The closest star to Earth, other than the sun, is Proxima Centauri at some 4.22 light-years away. Scaling the Earth-sun distance at one inch places this star at 4.22 miles (7 km) distant.

    Scaling the Astronomical Unit at one inch (2.5 cm), here are distances to various bright stars, star clusters and galaxies:

      Alpha Centauri: 4 miles (6.4 km)
      Sirius: 9 miles (14.5 km)
      Vega: 25 miles (40 km)
      Fomalhaut: 25 miles (40 km)
      Arcturus: 37 miles (60 km)
      Antares: 600 miles (966 km)
      Pleiades open star cluster: 440 miles (708 km)
      Hercules globular star cluster (M13): 24,000 miles (38,600 km)
      Center of Milky Way galaxy: 27,000 miles (43,500 km)
      Great Andromeda galaxy (M31): 2,300,000 miles (3,700,000 km)
      Whirlpool galaxy (M51): 37,000,000 miles (60,000,000 km)
      Sombrero galaxy (M104): 65,000,000 miles (105,000,000 km)

Parsec is a unit of distance equal to 3.26 light-years. One parsec corresponds to the distance at which the mean radius of the earth's orbit subtends an angle of one second of arc. The name means PARallax-SECond, and it refers to a way to measure the distances to other stars.

    The most accurate way to measure the distances to close stars is to use basic geometry. Astronomers measure the position of a star in the sky at six-month intervals, when Earth is on opposite sides of the Sun. If the star is close, then it will appear to shift a bit compared to the background stars. It is the same effect you see if you hold your finger in front of your face and look at it with first one eye, then the other: the finger appears to move against the background of objects. This effect is called parallax. If a star has a parallax of one second - in other words, if it appears to shift back and forth across the sky by exactly one second of arc (1/3600 degree) - then its distance is one parsec.

In "Star Wars Episode IV: A New Hope," Han Solo convinces Obi-Wan that his ship is fast enough to get to Alderaan by saying:
"You've never heard of the Millennium Falcon? It's the ship that made the Kessel Run in less than twelve parsecs."

But the parsec is a unit of distance, not time. Kessel Run explanation:

  1. George Lucas made an error and did not know what a parsec was.
    Maybe he thought it was a unit of time (PARallax-SECond).
  2. Han Solo lied by making a non-sensical claim to two yokels.
    I have just run a marathon in 24 miles. Not 26.2 miles.
  3. The Falcon skirted the event horizons of black holes to reduce the total Kessel Run travel distance.
    I have just traveled the Poughquag-Pawling run in 4 miles. Not 5.9 miles. (And using an Earth boring vehicle.)

  kilometres (km) Astronomical units (AU) Light Years (ly) Parsec (pc)
kilometres (km) 1 149.6 million 9,460,000,000,000 30,857,000,000,000
Astronomical units (AU) 0.0000000067 1 63,240 206,263
Light Years (ly) 0.00000000000011 0.000016 1 3.2616
Parsec (pc) 0.000000000000033 0.0000048 0.3066 1

  <   This concludes the Expanding Your Astronomical Vocabulary portion of the program. Next up ... What's Up in the Sky This Week ...


What's Up in the Sky This Week


  >   In this next segment of the program (What's Up in the Sky This Week), I will highlight events in the sky that are of interest to the average person. First up ...

  • Evening sky highlights
    18 Oct 2017 Uranus comes to opposition. It will peak at an altitude of 60, the highest it has appeared at opposition since February 1963.
    24 Oct 2017 Saturn 3 degrees south of Moon
    24 Oct 2017 Moon at apogee

  • Morning sky highlights
    N/A No morning highlights

  • Upcoming meteor showers
    22 Oct Orionid meteor shower (class I major shower)

    2017 Major Meteor Showers (Class I)

    Shower Activity Period Maximum Radiant Velocity r Max. Time Moon
    Date S. L. R.A. Dec. km/s ZHR
    Orionids (ORI) Aug 25-Nov 19 Oct 22 208.9 06:24 +15.5 67.1 2.5 15 0500 03

  <   This concludes the What's Up in the Sky This Week portion of the program. Next up ... Astronomical Curiosities ...


Astronomical Curiosities


Astronomical Apps


  >   In this segment, called Astronomical Curiosities, I will explore a unique and different aspect of the world of astronomy. Today's curiosity is ...

This is the The Astronomical Almanac on WPWL - Pawling Public Radio - 103.7 FM - Pawling, New York ... streaming live at pawlingpublicradio.org.

  1. Smartphone apps (that I use):

      (first, see III below)

    1. Astronomy
      1. SkySafari (5, 5 Plus, and 5 Pro) (https://skysafariastronomy.com/)
          Accurate Simulation
          Simulate the sky from anywhere on Earth, up to 10,000 years in the past or future. Animate transits, conjunctions, eclipses, and other events with time controls.
          Telescope Control
          With our SkyFi or SkyWire, SkySafari Plus & Pro apps can point your computer-controlled telescope anywhere in the sky.
          Largest Mobile Database
          25,000,000+ stars, 740,000+ galaxies, and over 630,000+ solar system objects, including every comet and asteroid ever discovered (numbers vary on version).
          Compass & Gyro Support
          SkySafari can help you identify stars, planets and constellations by holding your phone up to the sky - as you move the phone around, the sky chart follows your motion.
          Educational Content
          Hundreds of images from NASA space missions, the Hubble Space Telescope, and the world's foremost astrophotographers.
          Precision Graphics
          Computing the positions of solar system objects to sub-arcsecond precision with the latest JPL planetary ephemerides.
      2. Wunderground (weather app) [ PC | iPhone | Android ]
      3. myCSC (Clear Sky Clock) (http://www.cleardarksky.com/c/4173ObCTkey.html?1)
      4. Scope Nights (weather specifically for night time viewing) (http://eggmoonstudio.com/)

      5. SkyWeek + (from Sky and Telescope) (http://www.skyandtelescope.com/sky-and-stargazing-apps/)
      6. Deep Sky Browser (info on DSOs from many catalogues)
      7. Observer Pro (DSO availability from your location)
      8. Sky Survey (point phone and learn)
      9. Planisphere (similar to paper version)
      10. Sky Atlas (sky charts on your phone)
      11. Exoplanet (keep up to date on exoplanets)
      12. Star Atlas (where are objects via sky charts)
    2. Solar System
      1. What's Up (planets in the sky)
      2. Solar Monitor (latest solar data)
      3. SoHO (different views of the Sun [now])
      4. Eclipse Safari (countdown to April 8, 2024 total solar eclipse)
      5. Aurora Fcst (monitors auroral activity)
      6. iFlares (predicts brightening of polished antennas on the 90 Iridium communication satellites) (http://pleasantsoftware.com/iFlares/)
      7. Moon Atlas (view any part of the Moon)
      8. Moon Maps (highlighting the Moon's terminator)
      9. MoonMapPro (select area, view and learn)
      10. Gas Giants (Jupiter, Saturn, Uranus, Neptune - positions of Moons)
      11. JupiterMoons (positions of Moons [S&T]) (http://www.skyandtelescope.com/sky-and-stargazing-apps/)
      12. SaturnMoons (positions of Moons [S&T]) (http://www.skyandtelescope.com/sky-and-stargazing-apps/)
      13. Pluto Safari (upcoming flyby of 2014 MU69 - days until and distance to)
    3. NASA
      1. NASA TV (watch NASA TV)
      2. APODViewer (Astronomy Photo Of the Day)
      3. SatelliteSafari (monitor location of hundreds of satellites)
      4. GoSatWatch (similar to SatelliteSafari)

  2. Laptop / Desktop apps (that I use):
    1. Starry Night (http://www.starrynight.com/starry-night-7-professional-astronomy-telescope-control-software.html)
    2. TheSky6 and TheSkyX (http://www.bisque.com/sc/pages/TheSkyX-Editions.aspx)
    3. KnightVision (http://knightware.biz/knightvision/knightvision.htm)
    4. New Astronomy Press CCD Calculator (http://www.newastro.com/book_new/camera_app.html)

  3. The 11 best astronomy apps (from BusinessInsider.com) with apps I use in bold:
    1. SkySafari (5, 5 Plus, and 5 Pro)
        Accurate Simulation
        Simulate the sky from anywhere on Earth, up to 10,000 years in the past or future. Animate transits, conjunctions, eclipses, and other events with time controls.
        Telescope Control
        With our SkyFi or SkyWire, SkySafari Plus & Pro apps can point your computer-controlled telescope anywhere in the sky.
        Largest Mobile Database
        25,000,000+ stars, 740,000+ galaxies, and over 630,000+ solar system objects, including every comet and asteroid ever discovered (numbers vary on version).
        Compass & Gyro Support
        SkySafari can help you identify stars, planets and constellations by holding your phone up to the sky - as you move the phone around, the sky chart follows your motion.
        Educational Content
        Hundreds of images from NASA space missions, the Hubble Space Telescope, and the world's foremost astrophotographers.
        Precision Graphics
        Computing the positions of solar system objects to sub-arcsecond precision with the latest JPL planetary ephemerides.
    2. Starmap (night's best selection and compass / gryo sky viewing)
    3. Pocket Universe
    4. Solar Walk
    5. Deluxe Moon HD (lets you keep track of the moon phases, daily moonrise and moonset times, and what distance the moon is from the Earth)
    6. Star Walk
    7. Star Chart
    8. Distant Suns
    9. NASA app (great resource for details on the latest space exploration missions)
    10. Sky View
    11. Night Sky Lite

  <   This concludes the Astronomical Curiosities portion of the program. Next up ... Did You Know? ...


Did You Know?


  >   This segment of the program will be devoted to little bits of trivia that can be shared at parties, family get-togethers, reunions. Hey, the next time you are at a bar and there is a lull in the conversation, simply yell out Did You Know ... and share the following!

Uranian Axis of Rotation: The Uranian system has a unique configuration among those of the planets because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit.

A day on Uranus is 17 hours, 14 minutes and 24 seconds. In other words, a day on Uranus is shorter than a day on Earth.

Since the Uranian axis is tilted to almost 90-degrees, unlike the other planets, which spin like tops on a table, Uranus looks like it's rolling around. For part of the year on Uranus, the Sun appears to be move through the sky, just like we have on Earth. But then, as the year goes on, one hemisphere is in light, and the other is in darkness for an entire season.

What this means is that a day on Uranus is the same as an entire season on Uranus. Even though the planet is rotating on its axis, the Sun will just spiral around in the sky until the planet has gone far enough around the Sun for it to be obscured. Day on Uranus is as long as Summer on Uranus, and night on Uranus is as long as winter on Uranus. Wrap your mind around that!

  <   This concludes the Did You Know? portion of the program. Next up ... The Buffer Zone ...


The Buffer Zone


  >   If there is still time left in the program, this segment (The Buffer Zone) will be devoted to 'personal recollections' of the things that initially got me interested in astronomy.

The Astronomical Almanac can be found on the web at http://www.stargate4173.com/wpwl/.

You will be able to see:

  • The format of the show
  • Links to the music from the show
  • Links to the notes for each episode
  • My bio

  <   This concludes the The Buffer Zone portion of the program.

This has been The Astronomical Almanac
on WPWL - Pawling Public Radio - 103.7 FM - Pawling, New York.
I have been your host - Bob Antol.
I hope you enjoyed today's show and are a little more comfortable with the topics I discussed so you can now more easily recognize, grasp and appreciate the universe around us.
On next week's show, the episode will be entitled Bayer Designations and Astronomical Apps (Part 2).

Clear skies ... and don't forget ... to look up!

copyright © 2017 Robert A. Antol