THE SPECTACULAR PARADE OF PLANETS 8 APRIL 2024
At a total solar eclipse, gazing at the obscured sun and the pearly-white corona with the naked eye invokes awe and wonder even if you are a veteran eclipse viewer. But that is not the only extraordinary sight at totality. You must also avert your gaze toward the sun to look around at the twilight along 360 degrees of horizon, and also notice the stars and planets of the ‘night’ sky surrounding the sun. You should have plenty of time to see all of this at the 2024 total solar eclipse because it is a relatively long totality — four minutes or more in the Americas.
A PARADE OF BRIGHT PLANETS VISIBLE ON 8 APRIL 2024
When considering the planets, this 2024 total solar eclipse is a special one: the planets will be aligned in your favor!. ALL five of the bright planets should be visible during totality in a parade along the line of the ecliptic on the sky. The ecliptic is the line superimposed on the background of distant stars in the sky traced by the path of the sun seen from Earth. On eclipse day, the planets will be visible in the sky as shown in the image below.
Bright planet positions in the sky at the 2024 total solar eclipse. This fish-eye view of the sky was constructed using the Sky & Telescope Sky Chart Calculator as calculated for the time of totality on 8 April 2024 in Mazatlán, Mexico. The location of the moon (and of course the sun at eclipse) is indicated, and the black line across the sky is the ecliptic. The planets relative to the sun fall more or less along the ecliptic. Jupiter will be to the east of the sun, and Venus, Saturn and nearby Mars to the west. Mercury will be just east and very close to the sun. Being near its closest approach to Earth, its crescent should be clearly visible using binoculars or a telescope at totality, and will probably be visible to the naked eye.
It is unusual that all five of the bright planets will line up not too far from the sun/moon in the sky like this at an eclipse. Normally the planets nearer to the sun than the Earth, Mercury and Venus, will be visible during totality if the eclipse at your location is not near dawn or dusk, or in rare circumstances when either will be in opposition (when the planetary orbit has taken it to the other side of the sun from Earth). Those outer planets whose orbits are farther from the sun than the earth (Mars, Jupiter, Saturn, plus also Uranus, Neptune, and Pluto) are frequently seen at nighttime on an eclipse day and are then not visible during the total eclipse. A visualization of the orientation of the planets on their orbits is shown below for eclipse day 8 April 2024.
Note that if you will be viewing the eclipse at a location along the eclipse path other than Mazatlán, the location of this planetary spectacle in the sky will be somewhat different. For example, viewing near the end of the eclipse path in the North Atlantic Ocean, you will be observing totality near sunset so planets to the west of the sun (Saturn, Mars, Venus) may have set below the horizon, but Mercury and Jupiter will be visible.
If you set one of your eclipse-viewing goals to see all five of these planets at totality, it may be helpful to generate an image like the one above using the Sky & Telescope Sky Chart Calculator. Be careful to set the times in the calculator correctly. In the calculator, I set the UTC offset manually to 0 hours, then use interactive eclipse timing calculator to determine the timing of totality at your viewing location in UTC, which is then entered as the time in the Sky and Telescope Sky Chart Calculator. If you do not do this, the calculator will use the time zone of your phone, tablet, or computer, and that may not correspond to the time at your eclipse viewing location.
PLANETARY ORBITS
The illustration below depicts the orbits and locations planets on eclipse day. These diagrams show why the planets appear as they do in the sky at totality. All seven planets appear in a relatively narrow slice of sky toward the sun as seen from the earth. Pluto, now not considered to be a true planet for some strange reason, falls outside this cone, but anyway it is far too faint to be visible with anything other than a substantial telescope. Identify the earth in these diagrams by the blue planet with oceans. The planets in order of distance from the sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus Neptune, and finally non-planet Pluto.
The planetary orbits and the locations of the eight planets and Pluto on 8 April 2024. The upper view illustrates the planetary orbits as seen from the viewpoint of the north pole of the sun, and the lower image shows a viewpoint in the ecliptic plane from outside the solar system. These images were generated using this solar system simulator. The color of the orbital segments indicate locations where the orbits are above (blue) and below (green) the ecliptic plane. Of course, the planets and their orbits are not shown to scale.
WHY DO THE PLANETS MOVE ALONG THE ECLIPTIC?
The diagram of planetary orbits above illustrates that they all revolve about the sun in a very specific plane, the ecliptic plane. Planetary movement in space causes the them to journey in the earth’s sky along the ecliptic. The constellations of the zodiac fall along this line, so the orbits of the major planets provide the underpinning of astrology. Pluto is the exception to this rule, indicating that its history differs from that of the other planets.
The rotation of the sun is in the same sense as the revolution of the planets about it, and it is tilted by only about 7º with respect to the ecliptic plane. All of these observed properties of the solar system have led astronomers to believe that the entire solar system arose from a single, giant cloud of dust and gas. As the cloud began to collapse upon itself owing to its own gravity, the original tiny net rotation of the cloud caused it to rotate faster and faster as the cloud shrunk in size and became more dense (in the same fashion as a spinning figure skater). Interaction of random motions within the cloud that did not move in the direction of rotation with those parts that did would cancel out. The result of this process would leave a central massive condensation (becoming the sun) surrounded by a thin disk of gas and dust very much denser than the original cloud. The ancient proto-sun finally collapsed enough that its core regions heated above 10 million degrees, at which point its interior nuclear furnace ignited.
Around the same time, individual clumps of gas and dust revolving about the ancient sun collapsed upon themselves, forming planets with their own disks from which arose the planetary moons. Interestingly, the earth’s moon most likely did not arise from such a disk revolving around the proto-earth; it is much too large relative to the size of the earth. The earth-moon system is the only ‘double planet’ in the solar system, no other planet has a moon so large in comparison to its diameter. Our moon is thought to have formed by a collision of the earth with another planet of similar size.
So at the 8 April 2024 total solar eclipse, when you see all the planets arranged along a line in the sky through the sun and moon, reflect on the ancient disk of dust and gas that was the infant solar system.
