Largest Satellites of Our Solar System

Here is a table of the 12 largest satellites in our solar system.  In addition to the size of each satellite, its home planet, its median distance from that planet, and discovery information, its median distance from its home planet is given in terms of the median lunar distance from the Earth.  Remarkably, Pluto’s moon Charon is just 0.05 lunar distances from Pluto, only 19,591 km.  Only one other of the largest satellites orbits closer to its home planet than the Moon orbits around the Earth, and that is Neptune’s moon Triton at 92% of the Earth-Moon distance.  At the other end of the scale, Saturn’s moon Iapetus orbits Saturn over nine times further away than the Moon orbits the Earth.

Now let’s look at the orbital eccentricity of each of the largest moons, and the orbital inclination relative to the equator of its home planet.

Our familiar Moon is really an oddball: it has the greatest orbital eccentricity of all the largest satellites, and, with the exception of Triton and Iapetus, by far the greatest orbital inclination relative to the equator of its home planet.  Triton is the oddball among oddballs as it is the only large satellite in our solar system that has a retrograde orbit: it orbits Neptune in a direction opposite the planet’s rotation.  Iapetus has an orbital inclination relative to Saturn’s equator almost as much as the Moon’s orbital inclination relative to the Earth’s equator, but this anomaly can perhaps be forgiven because Iapetus orbits so very far away from Saturn.  Its orbital period is over 79 days.

Note that the Moon’s orbital inclination relative to the equator of the Earth varies between 18.33˚ and 28.60˚.  This occurs because the intersection between the plane of the Moon’s orbit around the Earth and the plane of the Earth’s orbit around the Sun precesses westward, making an entire circuit every 18.6 years.

Ganymede
Titan
Callisto
Io
The Moon
Europa
Triton
Titania
Rhea
Oberon
Iapetus
Charon

88 Constellations, One Musical Instrument

Of all the constellations in our sky, only one is a musical instrument: Lyra the Lyre.  A lyre is a stringed harplike instrument used to accompany a singer or reader of poetry, especially in ancient Greece.  One wonders what strange and lonely enchantments await the contemplative listener as Lyra wheels through our zenith these short summer nights.

Lyra crossing the celestial meridian at 12:06 a.m. CDT 15 Jul 2018 at 42°58′ N, 90°09′ W

Nova Scuti 2018

Nova Scuti 2018 (or N Sct 2018, for short) was discovered by prolific nova finder Yukio Sakurai of Japan on June 29, 2018.  His discovery image at 13:50:36 UT showed the nova shining at magnitude 10.3 (unfiltered CCD magnitude), using only a 180-mm f/2.8 lens plus a Nikon D7100 digital camera.  One of his many discoveries is named after him: Sakurai’s Object.

What is a nova?  A classical nova is a close binary star system that includes a white dwarf and a “normal” star.  The white dwarf siphons material off the other star until a critical density and temperature is reached in the atmosphere of the white dwarf, and a thermonuclear detonation occurs.

Nova Scuti 2018 will eventually receive a variable star designation (V507 Sct?).  Here are some typical nova light curves.

Nova Scuti 2018 is located fortuitously close to the 4.7-magnitude star Gamma (γ) Scuti.

Scutum Region (Source: Voyager 4.5)
Gamma Scuti Region (Source: Guide 9.1)

Here is a time sequence of images I’ve acquired of Nova Scuti 2018.  Comparing with the star chart above, can you find the nova?

Gorgeous Grieg

Edvard Grieg (Photo EGM0270, Edvard Grieg Archives at the Bergen Public Library)

Norwegian composer Edvard Grieg (1843-1907) is best known for his iconic Piano Concerto in A minor, op. 16, written in 1868 when the composer was just 24 years old, and his Peer Gynt suites, No. 1, op. 46 (1875, 1888), and No. 2, op. 55 (1875, 1891).  Like Tchaikovsky, Grieg had a gift for melody.

Grieg once wrote, “Artists like Bach and Beethoven erected churches and temples on the heights.  I only wanted to build dwellings for men in which they might feel happy and at home.”  With this in mind, you will find no better introduction to some of the other gorgeous music that Grieg wrote than Norwegian conductor Bjarte Engeset conducting Sweden’s Malmö Symphony Orchestra on Naxos 8.572403.

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Bjarte Engeset

Seldom have I found a disc of music so beautifully paced and played.  These five pieces for string orchestra (augmented by oboe and horn on “Evening in the Mountains”) followed by one piece for full orchestra provide the listener with over 71 minutes of pure enjoyment that will convince you (if you weren’t already convinced) that Grieg deserves a place alongside the most significant composers of the late 19th and early 20th centuries.  For me, personally, every one of these pieces is a favorite.  There is nothing to skip over here!

Naxos 8.572403

Two Elegiac Melodies, op. 34 (1880)
+ The Wounded Heart
+ The Last Spring

Two Melodies for String Orchestra, op. 53 (1890)
+ Norwegian
+ The First Meeting

From Holberg’s Time: Suite in Olden Style, op. 40 (1884)
+ Prelude
+ Sarabande
+ Gavotte
+ Air
+Rigaudon

Two Lyric Pieces, op. 68 (1897-1899)
+ Evening in the Mountains
+ At the Cradle

Two Nordic Melodies for String Orchestra, op. 63 (1895)
+ In Folk Style
+ Cow-Call & Peasant Dance

Lyric Suite, op. 54 (1905)
+ Shepherd Boy
+ Gangar
+ Notturno
+ March of the Dwarves

Don’t let words like “gorgeous” and “pure enjoyment” give you the impression that this music is lightweight fare.  There is a sadness in this beautiful music that evinces that it is anything but superficial.  Grieg and his wife Nina lost their only child, Alexandra, to meningitis when she was little more than a year old, Nina later miscarried a second child, and Grieg himself suffered all his adult life from the effects of pleurisy he had contracted when he was 17 years old.

Nina Grieg with her daughter Alexandra (Edvard Grieg Archives at the Bergen Public Library)