APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 5410
Joined: Fri Dec 04, 2009 3:27 am

APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by APOD Robot » Fri Apr 27, 2012 4:06 am

Image Jupiter and the Moons of Earth

Explanation: Planet Earth has many moons. Its largest artifical moon, the International Space Station, streaks through this lovely skyview with clouds in silhouette against the fading light of a sunset. Captured from Stuttgart, Germany last Sunday, the frame also includes Earth's largest natural satellite 1.5 days after its New Moon phase. Just below and left of the young crescent is Jupiter, another bright celestial beacon hovering near the western horizon in early evening skies. Only briefly, as seen from the photographer's location, Jupiter and these moons of Earth formed the remarkably close triple conjunction. Of course, Jupiter has many moons too. In fact, close inspection of the photo will reveal tiny pin pricks of light near the bright planet, large natural satellites of Jupiter known as Galilean moons.

<< Previous APODDiscuss Any APOD Next APOD >>
[/b]

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by neufer » Fri Apr 27, 2012 4:23 am

http://en.wikipedia.org/wiki/Many_Moons wrote:
Image
<<Many Moons is a children's picture book written by James Thurber and illustrated by Louis Slobodkin. It was published by Harcourt, Brace & Company in 1943 and won the Caldecott Medal in 1944. Princess Lenore becomes ill, and only one thing will make her better: the moon. Despite winning the Caldecott Medal with Slobodkin's original illustrations, a reprint in 1990 by Harcourt featured the text accompanied by new illustrations by Marc Simont. It was made into an opera by American composer, Celius Dougherty. It was also made into a play, adapted by Charlotte Chorpenning. Many Moons is about a sick princess who wants the moon. The princess is perhaps more sick at heart than body. Her father, the king, is enraged when the wizards, the Lord High Chamberlain, and the mathematician court can't get the moon. In the end, it is the jester who realizes that the princess thinks the moon is only as big as her thumbnail and made of gold, so he goes to the goldsmith, who makes a necklace with a gold sphere on it. the jester gives it to the princess. The King then worries that she will see the moon in the sky that night and realize that the necklace was not the real moon. The jester goes to check on her. The princess thinks that whenever something is taken, it is replaced, like her tooth, a unicorn's horn, and flowers.>>
Art Neuendorffer

agulesin
Ensign
Posts: 46
Joined: Mon Mar 15, 2010 12:38 pm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by agulesin » Fri Apr 27, 2012 12:32 pm

I was wondering about "the others":

"Earth's largest natural satellite"

Have NASA visited the others? or was the landing on the "largest" enough to satisfy everyone's curiosity?

User avatar
geckzilla
Ocular Digitator
Posts: 9180
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by geckzilla » Fri Apr 27, 2012 1:07 pm

The others are really hard to see so not very many people care about them. :(
Just call me "geck" because "zilla" is like a last name.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by neufer » Fri Apr 27, 2012 1:26 pm

geckzilla wrote:
agulesin wrote:
I was wondering about "the others": "Earth's largest natural satellite"

Have NASA visited the others? or was the landing on the "largest" enough to satisfy everyone's curiosity?
The others are really hard to see so not very many people care about them. :(
<<Between 1993 and 2002, four missions repaired, upgraded, and replaced systems on the (24,500 lb) Hubble Space Telescope (HST); a fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved one final servicing mission, completed in 2009. The telescope is now expected to function until at least 2014. Its scientific successor, the James Webb Space Telescope (JWST), is to be launched in 2018 or possibly later.>>
Art Neuendorffer

User avatar
Chris Peterson
Abominable Snowman
Posts: 18284
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by Chris Peterson » Fri Apr 27, 2012 1:43 pm

agulesin wrote:I was wondering about "the others":

"Earth's largest natural satellite"

Have NASA visited the others? or was the landing on the "largest" enough to satisfy everyone's curiosity?
We have no other permanent natural satellites except for the Moon. At any time we may have several small natural satellites in unstable orbits, lasting a few years. None have been visited, none are likely to be visited anytime soon.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

westminster

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by westminster » Fri Apr 27, 2012 2:38 pm

Is it possible to identify the individual moons? There seems to be one to the upper left and two to the lower right.

btoman

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by btoman » Fri Apr 27, 2012 3:38 pm

Still amazed that the Galilean moons showed up in this image. Looking at their positions for what I figure was around sunset in that part of the world, looks like the two at bottom right of Jupiter would be Io and Ganymede. They are around 6 mag so they could show up. I'm still stumped as to why more stars of similar magnitudes did not show up though. Especially higher up where it would should be darker due to the sun setting. Jupiter was pretty low and still in the sun a bit. Also, the Galilean moons always look so tiny and relatively close to Jupiter (even when spread out to their furthest in the orbits) through my telescopes or binoculars; I didn't realize they would look that far away from Jupiter with so little magnification.

nafpie
Ensign
Posts: 17
Joined: Thu Jun 16, 2005 6:52 am
Location: Stuttgart, Germany

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by nafpie » Fri Apr 27, 2012 3:44 pm

westminster wrote:Is it possible to identify the individual moons?
Sure.

All four Galilean moons are visible in the original file (5616x3744 pixel).

At the left, a crop of this file is shown (reprocessed to improve the visbility of the moons). At the right, a simulation tells the moon names (Stellarium = planetarium software: April 22th, 2012, 19:08 UT).
Last edited by nafpie on Fri Apr 27, 2012 3:58 pm, edited 1 time in total.
Best regards,
Stefan

http://www.photomeeting.de

User avatar
Ann
4725 Å
Posts: 13502
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by Ann » Fri Apr 27, 2012 3:54 pm

Stefan, I'm amazed that you could bring out so much detail in Jupiter and its Galilean moons in a picture like this one! :-D :clap: :thumb_up:

Ann
Color Commentator

nafpie
Ensign
Posts: 17
Joined: Thu Jun 16, 2005 6:52 am
Location: Stuttgart, Germany

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by nafpie » Fri Apr 27, 2012 3:58 pm

Ann wrote:Stefan, I'm amazed that you could bring out so much detail in Jupiter and its Galilean moons in a picture like this one!
Thanks Ann.

The only problem was that Jupiter was so low in the sky during dawn. I had no chance to see them in my 10x42 binoculars, for example.
Best regards,
Stefan

http://www.photomeeting.de

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

3753 Cruithne and "The Bean"

Post by neufer » Fri Apr 27, 2012 4:29 pm

Chris Peterson wrote:
We have no other permanent natural satellites except for the Moon. At any time we may have several small natural satellites in unstable orbits, lasting a few years. None have been visited, none are likely to be visited anytime soon.
  • But at less that 0.1 AU what better place for the next manned invasion :?:
http://en.wikipedia.org/wiki/3753_Cruithne wrote:
Image
<<3753 Cruithne is an asteroid in orbit around the Sun in approximate 1:1 orbital resonance with the Earth. It is a periodic inclusion planetoid orbiting the Sun in an apparent horseshoe orbit. It has been incorrectly called "Earth's second moon", but it is a quasi-satellite, not a moon. Cruithne does not orbit Earth, and at times it is on the other side of the Sun. Its orbit takes it inwards towards the orbit of Mercury, and outside the orbit of Mars. Cruithne orbits the Sun in about 1 year, but it takes 770 years for the series to complete a horseshoe-shaped movement, with the Earth in the gap of the horseshoe.

Cruithne was discovered on October 10, 1986, by Duncan Waldron on a photographic plate taken with the UK Schmidt Telescope at Siding Spring Observatory, Coonabarabran, Australia. The 1983 apparition (1983 UH) is credited to Giovanni de Sanctis and Richard M. West of the European Southern Observatory in Chile. It was not until 1997 that its unusual orbit was determined by Paul Wiegert and Kimmo Innanen, working at York University in Toronto, and Seppo Mikkola, working at the University of Turku in Finland. The asteroid is named after the Cruithne or Cruthin, a people of early medieval Ireland (naturally :!: ).
Cruithne is approximately 5 km in diameter, and its closest approach to Earth is approximately thirty times the separation between Earth and the Moon (12 Gm). From 1994 through 2015, Cruithne makes its annual closest approach to Earth every November. Although Cruithne's orbit is not thought to be stable over the long term, calculations by Wiegert and Innanen showed that it has probably been synchronized with Earth's orbit for a long time. There is no danger of a collision with Earth for millions of years, if ever. Its orbital path and Earth's do not cross, and its orbital plane is currently tilted to that of the Earth by 19.8°. Cruithne, having a maximum near-Earth magnitude of +15.8, is fainter than Pluto and would require at least a 12.5-inch reflecting telescope to be seen.

Cruithne is in a normal elliptic orbit around the Sun. Its period of revolution around the Sun, approximately 364 days at present, is almost equal to that of the Earth. Because of this, Cruithne and Earth appear to "follow" each other in their paths around the Sun. This is why Cruithne is sometimes called "Earth's second moon". However, it does not orbit the Earth and is not a moon. In 2058, Cruithne will come within 0.09 AU (13.6 Gm) of Mars. Due to a high orbital eccentricity, Cruithne's distance from the Sun and orbital speed vary a lot more than the Earth's, so from the Earth's point of view Cruithne actually follows a kidney bean-shaped horseshoe orbit ahead of the Earth, taking slightly less than one year to complete a circuit of the "bean". Because it takes slightly less than a year, the Earth "falls behind" the bean a little more each year, and so from our point of view, the circuit is not quite closed, but rather like a spiral loop that moves slowly away from the Earth.

After many years, the Earth will have fallen so far behind that Cruithne will then actually be "catching up" on the Earth from "behind". When it eventually does catch up, Cruithne will make a series of annual close approaches to the Earth and gravitationally exchange orbital energy with Earth; this will alter Cruithne's orbit by a little over half a million kilometres—while Earth's orbit is altered by about 1.3 centimetres —so that its period of revolution around the Sun will then become slightly more than a year. The kidney bean will then start to migrate away from the Earth again in the opposite direction – instead of the Earth "falling behind" the bean, the Earth is "pulling away from" the bean. The next such series of close approaches will be centred on the year 2292 – in July of that year, Cruithne will approach Earth to about 12.5 Gm. After 380 to 390 years or so, the kidney-bean-shaped orbit approaches Earth again from the other side, and the Earth, once more, alters the orbit of Cruithne so that its period of revolution around the Sun is again slightly less than a year (this last happened with a series of close approaches centred on 1902, and will next happen with a series centered on 2676). The pattern then repeats itself.>>
Art Neuendorffer

hexalm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by hexalm » Fri Apr 27, 2012 4:56 pm

That's no moon. It's a space station.

:D

nafpie
Ensign
Posts: 17
Joined: Thu Jun 16, 2005 6:52 am
Location: Stuttgart, Germany

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by nafpie » Fri Apr 27, 2012 5:07 pm

hexalm wrote:That's no moon. It's a space station.
By definition, a Moon is a natural satellite of a planet or celestial body. Therefore, the ISS can't be a moon.

But if 'The Moon' is also called a 'natural satellite' of the Earth, why should the ISS not be an 'artificial moon'?

:roll:
Best regards,
Stefan

http://www.photomeeting.de

gdreiber
Asternaut
Posts: 5
Joined: Mon Feb 20, 2012 6:12 pm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by gdreiber » Fri Apr 27, 2012 5:14 pm

the picture is great, also really liked the graphics of Cruithne circling the earth.
I have a question regarding the moons circling the earth. From a stationary point above the sun does the moon form a sine wave type orbit and does not actually form a cycloid type figure. True/ false? Can any moon have a cycloid shape orbit?

Pastorian
Ensign
Posts: 28
Joined: Wed Mar 28, 2012 3:30 pm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by Pastorian » Fri Apr 27, 2012 5:52 pm

Image

hexalm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by hexalm » Fri Apr 27, 2012 6:33 pm

nafpie wrote:
hexalm wrote:That's no moon. It's a space station.
By definition, a Moon is a natural satellite of a planet or celestial body. Therefore, the ISS can't be a moon.

But if 'The Moon' is also called a 'natural satellite' of the Earth, why should the ISS not be an 'artificial moon'?

:roll:
True... from a certain point of view.

hexalm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by hexalm » Fri Apr 27, 2012 6:33 pm

nafpie wrote:
hexalm wrote:That's no moon. It's a space station.
By definition, a Moon is a natural satellite of a planet or celestial body. Therefore, the ISS can't be a moon.

But if 'The Moon' is also called a 'natural satellite' of the Earth, why should the ISS not be an 'artificial moon'?

:roll:
True... from a certain point of view.

hexalm

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by hexalm » Fri Apr 27, 2012 9:27 pm

Pastorian wrote:Image
Exactement! :wink:

User avatar
Chris Peterson
Abominable Snowman
Posts: 18284
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by Chris Peterson » Fri Apr 27, 2012 9:44 pm

nafpie wrote:By definition, a Moon is a natural satellite of a planet or celestial body.
No, a "moon" is a natural satellite. The "Moon" is Earth's natural satellite.
But if 'The Moon' is also called a 'natural satellite' of the Earth, why should the ISS not be an 'artificial moon'?
Of course, it can. Because colloquially, any satellite, natural or otherwise, can be called a moon.

I'm always amazed at how many people get focused on a single meaning for a word, and overlook all the other possible rich usage.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

Flase
Brother of Ture
Posts: 132
Joined: Wed Dec 07, 2011 7:17 am

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by Flase » Sat Apr 28, 2012 10:28 am

Eros is of course another asteroid that gets pretty close to Earth...
Image

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by neufer » Sat Apr 28, 2012 2:04 pm

Flase wrote:
Eros is of course another asteroid that gets pretty close to Earth...
  • And to Mars:
http://en.wikipedia.org/wiki/433_Eros wrote:
<<433 Eros is a near-Earth asteroid (NEA) discovered in 1898, and the first asteroid to be orbited by a probe (in 2000). It is an S-type asteroid approximately 34.4×11.2×11.2 km in size, the second-largest NEA after 1036 Ganymed, and belongs to the Amor group. Its synodic period of over 846 earth days is among the largest of any body in the Solar System. Eros was one of the first asteroids to be visited by a spacecraft, and the first to be orbited and soft-landed on. NASA spacecraft NEAR Shoemaker entered orbit around Eros in 2000, and came to rest on its surface in 2001. [Erotian escape velocity = 10.3 m/s] On January 31, 2012, Eros passed the Earth at 0.17867 AU (26.729 Gm), about 70 times the distance to the Moon, with a visual magnitude of +8.1. During rare oppositions, every 81 years, such as in 1975 and 2056, Eros can reach a magnitude of +7.0, which is brighter than Neptune and brighter than any main-belt asteroid except 4 Vesta and, rarely, 2 Pallas and 7 Iris.

As one of the larger near-Earth asteroids (NEAs), Eros has played a significant role in history. It was discovered on the same night (13 August 1898) by Gustav Witt in Berlin and Auguste Charlois at Nice. Witt was taking a 2-hour exposure of Beta Aquarii to secure astrometric positions of asteroid 185 Eunike. During the opposition of 1900–1901, a worldwide program was launched to make parallax measurements of the asteroid to determine the solar parallax (or distance to the sun), with the results published in 1910 by Arthur Hinks of Cambridge. A similar program was then carried out, during a closer approach, in 1930–1931 by Harold Spencer Jones. The value obtained by this program was considered definitive until 1968, when greater faith was placed in radar and dynamical parallax methods.

Eros is a Mars-crosser asteroid, the first known to come within the orbit of Mars. Objects in such an orbit can remain there for only a few hundred million years before the orbit is perturbed by gravitational interactions. Dynamical integrations suggest that Eros may evolve into an Earth-crosser within as short an interval as 2 million years. It is a potential Earth impactor, believed to be larger than the impactor that created the Chicxulub Crater that led to the extinction of the dinosaurs.

Erotian surface gravity varies greatly, since Eros is not a sphere but an elongated peanut-shaped (or potato- or shoe-shaped) object. The daytime temperature on Eros can reach about 100 °C at perihelion. Nighttime measurements fall near -150 °C. Eros's density is 2,400 kg/m3, about the same as the density of Earth's crust. It rotates once every 5.27 hours.
NEAR scientists have found that most of the larger rocks strewn across Eros were ejected from a single crater in a meteor collision approximately 1 billion years ago. This impact may also be responsible for the 40 percent of the Erotian surface that is devoid of craters smaller than 0.5 kilometers across. It was originally thought that the debris thrown up by the collision filled in the smaller craters. An analysis of crater densities over the surface indicates that the areas with lower crater density are within 9 kilometers of the impact point. Some of the lower density areas were found on the opposite side of the asteroid but still within 9 kilometers. It is theorized that seismic shockwaves propagated through the asteroid, shaking smaller craters into rubble.

In an experimental legal case, Eros was claimed as property by Gregory W. Nemitz of OrbDev. Nemitz argued that, according to the homestead principle, he had the right to claim ownership of any celestial body that he made use of; he claimed he had designated Eros a spacecraft parking facility and wished to charge NASA a parking and storage fee of twenty cents per year for NEAR Shoemaker. An expert in extraterrestrial real estate issues, Virgiliu Pop, responded by using the same novelty-deed registry Nemitz had used for Eros to claim ownership of the Sun, stating: "I, for one, intended this move only to show how ridiculous a property rights system in outer space would be if it were to be based solely on claim unsubstantiated by any actual possession.">>
Art Neuendorffer

nafpie
Ensign
Posts: 17
Joined: Thu Jun 16, 2005 6:52 am
Location: Stuttgart, Germany

Re: APOD: Jupiter and the Moons of Earth (2012 Apr 27)

Post by nafpie » Tue May 01, 2012 10:01 am

Chris.
Chris Peterson wrote:No, a "moon" is a natural satellite. The "Moon" is Earth's natural satellite.
Lesson learned! :)

Stefan (German native speaker)