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What Cassini Saw - Incredible 4K Video of the planet Saturn
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By NASA
5 Min Read Planetary Alignments and Planet Parades
A sky chart showing Mars, Jupiter, Saturn, and Venus in a “planet parade.” Credits:
NASA/JPL-Caltech On most nights, weather permitting, you can spot at least one bright planet in the night sky. While two or three planets are commonly visible in the hours around sunset, occasionally four or five bright planets can be seen simultaneously with the naked eye. These events, often called “planet parades” or “planetary alignments,” can generate significant public interest. Though not exceedingly rare, they’re worth observing since they don’t happen every year.
Why Planets Appear Along a Line in The Sky
“Planet parade” isn’t a technical term in astronomy, and “planetary alignment” can refer to several different phenomena. As the planets of our solar system orbit the Sun, they occasionally line up in space in events called oppositions and conjunctions. A planetary alignment can also refer to apparent lineups in our sky with other planets, the Moon, or bright stars.
The planets of our solar system always appear along a line on the sky. This line, referred to as the ecliptic, represents the plane in which the planets orbit, seen from our position within the plane itself. NASA/Preston Dyches When it comes to this second type of planetary alignment, it’s important to understand that planets always appear along a line or arc across the sky. This occurs because the planets orbit our Sun in a relatively flat, disc-shaped plane. From Earth, we’re looking into that solar system plane from within. We see the racetrack of the planets from the perspective of one of the racers ourselves. When viewed edge-on, this disc appears as a line, which we call the ecliptic or ecliptic plane.
So, while planet alignment itself isn’t unusual, what makes these events special is the opportunity to observe multiple planets simultaneously with the naked eye.
Will the Planets Actually be Visible?
Before preparing to observe a planet parade, we have to consider how high the planets will appear above the horizon. For most observers to see a planet with the naked eye, it needs to be at least a few degrees above the horizon, and10 degrees or higher is best. This is crucial because Earth’s atmosphere near the ground dims celestial objects as they rise or set. Even bright planets become difficult or impossible to spot when they’re too low, as their light gets scattered and absorbed on its path to your eye. Buildings, trees, and other obstructions often block the view near the horizon as well.
This visibility challenge is particularly notable after sunset or before sunrise, where the sky is still glowing. If a planet appears very low within the sunset glow, it is very difficult to observe.
The Planets You Can See, and Those You Can’t
Five planets are visible without optical aid: Mercury, Venus, Mars, Jupiter, and Saturn. Ancient civilizations recognized these worlds as bright lights that wandered across the starscape, while the background stars remained fixed in place. In fact, the word “planet” comes to us from the Greek word for “wanderer.”
The solar system includes two additional major planets, Uranus and Neptune, plus numerous dwarf planets like Pluto and Ceres. Uranus and Neptune orbit in the dim, cold depths of the outer solar system. Neptune absolutely requires a telescope to observe. While Uranus is technically bright enough to detect with good eyesight, it’s quite faint and requires dark skies and precise knowledge of its location among similarly faint stars, so a telescope is recommended. As we’ll discuss in the next section, planet parades necessarily must be observed in twilight before dawn or after sunset, and this is not a good time to try observing extremely faint objects like Uranus and Neptune.
Thus, claims about rare six- or seven-planet alignments which include Uranus and Neptune should be viewed with the understanding that these two distant planets will not be visible to the unaided eye.
What Makes Multi-Planet Lineups Special
Lineups of four or five planet naked-eye planets with optimal visibility typically occur every few years. Mars, Jupiter, and Saturn are frequently seen in the night sky, but the addition of Venus and Mercury make four- and five-planet lineups particularly noteworthy. Both orbit closer to the Sun than Earth, with smaller, faster orbits than the other planets. Venus is visible for only a couple of months at a time when it reaches its greatest separation from the Sun (called elongation), appearing just after sunset or before sunrise. Mercury, completing its orbit in just 88 days, is visible for only a couple of weeks (or even a few days) at a time just after sunset or just before sunrise.
Planet parades aren’t single-day events, as the planets move too slowly for that. Generally, multi-planet viewing opportunities last for weeks to a month or more. Even five-planet events last for several days as Mercury briefly emerges from and returns to the Sun’s glare.
In summary, while they aren’t once-in-a-lifetime events, planetary parades afford an uncommon opportunity to look up and appreciate our place in our solar system, with diverse worlds arrayed across the sky before our very eyes.
Other Planet Lineups
Other recent and near-future multi-planet viewing opportunities:
January 2016 – Four planets visible at once before sunrise Late April to Late August 2022 – Four planets visible at once before sunrise Mid-June to Early July 2022 – Five planets visible at once before sunrise January to mid-February 2025 – Four planets visible at once after sunset Late August 2025 – Four planets visible at once before sunrise Late October 2028 – Five planets visible at once before sunrise Late February 2034 – Five planets visible at once after sunset (Venus and Mercury challenging to observe) About the January/February 2025 Planet Parade
The current four-planet lineup concludes by mid-February, as Saturn sinks increasingly lower in the sky each night after sunset. By mid-to-late February, Saturn appears less than 10 degrees above the horizon as sunset fades, making it difficult to observe for most people. While Mercury briefly joins Saturn in the post-sunset glow at the end of February, both planets will be too low and faint for most observers to spot.
Keep Exploring Discover More Topics From NASA
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By NASA
With the historic first international space docking mission only six months away, preparations on the ground for the Apollo-Soyuz Test Project (ASTP) intensified. At NASA’s Kennedy Space Center (KSC) in Florida, workers in the Vehicle Assembly Building (VAB) stacked the rocket for the mission, the final Saturn rocket assembled for flight. In the nearby Manned Spacecraft Operations Building (MSOB), the Apollo prime crew of Commander Thomas Stafford, Command Module Pilot Vance Brand, and Docking Module Pilot Donald “Deke” Slayton, and their backups Alan Bean, Ronald Evans, and Jack Lousma conducted vacuum chamber tests of the Command Module (CM), the final Apollo spacecraft prepared for flight.
Inside the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center in Florida, workers attach fins to the Saturn IB’s first stage. In the VAB, workers secure the first stage of the Saturn IB rocket onto the milk stool, perched on Mobile Launcher-1. Workers lift the second stage of the Saturn IB rocket prior to mating with the first stage. Workers lower a boilerplate Apollo spacecraft onto the Saturn IB rocket. The Saturn IB rocket, serial number SA-210, used for ASTP had a lengthy history. Contractors originally built its two stages in 1967, at a time when NASA planned many more Saturn IB flights to test Apollo spacecraft components in Earth orbit in preparation for the Moon landing. By 1968, however, after four uncrewed Saturn IB launches, only one launched a crew, Apollo 7. Four more Saturn IBs remained on reserve to launch crews as part of the Apollo Applications Program, renamed Skylab in 1970. Without an immediate mission, the two stages of SA-210 entered long-term storage in 1967. Workers later modified and refurbished the stages for ASTP before shipping them to KSC. The first stage arrived in April 1974 and the second stage in November 1972.
On Jan. 13, 1975, inside the cavernous VAB, workers stacked the Saturn IB rocket’s first stage onto Mobile Launcher-1 (ML-1), modified from its use to launch Saturn V rockets during the Apollo program with the addition of the milk stool pedestal. The milk stool, a 128-foot tall platform, allowed the Saturn IB to use the same Launch Umbilical Tower as the much larger Saturn V rocket at Launch Complex 39. The next day, workers lowered the second stage onto the first, followed by the Instrument Unit two days later. Finally, on Jan. 17 workers topped off the rocket with a boilerplate Apollo spacecraft while engineers continued testing the flight article in the MSOB.
The ASTP Apollo Command and Service Modules arrive at NASA’s Kennedy Space Center (KSC) in Florida. The ASTP Command Module arrives in KSC’s Manned Spacecraft Operations Building. The Command and Service Modules – CSM-111 – arrived at KSC from the Rockwell International plant in Downey, California, on Sept. 8, 1974, by C-5A Galaxy cargo plane. Rockwell had finished building the spacecraft in March 1970 and placed it in storage until July 1972. Modifications for ASTP took place between August 1972 and August 1974, following which Rockwell shipped the spacecraft to KSC. The sign on the shipping container bore the legend “From A to Soyuz – Apollo/Soyuz – Last and the Best.” Workers at KSC towed the modules to the MSOB for inspection and checkout, joined the two modules, and placed the combined spacecraft into a vacuum chamber.
The prime Apollo crew of Thomas Stafford, left, Vance Brand, and Donald “Deke” Slayton suit up in preparation for an altitude chamber test in the Command Module (CM). The astronauts inside the CM in the altitude chamber. In the MSOB, the prime and backup ASTP crews conducted tests of their spacecraft in an altitude chamber. After both crews completed simulated runs in December 1974, the prime crew of Stafford, Brand, and Slayton suited up, entered the CM inside the chamber, closed the hatch, and conducted an actual test on Jan. 14, with the chamber simulating altitudes of up to 220,000 feet. Two days later, the backup crew of Bean, Evans, and Lousma completed a similar test.
he backup Apollo crew of Alan Bean, left, Ronald Evans, and Jack Lousma suit up in preparation for an altitude chamber test in the Command Module (CM). Workers assist backup crewmember Lousma into the CM. To solve the problem of the Apollo and Soyuz spacecraft operating at different atmospheric pressures and compositions and using incompatible docking mechanisms, engineers designed a Docking Module (DM) that acted as both an airlock and a transfer tunnel and a Docking System (DS) that allowed the two nations’ spacecraft to physically join in space. NASA contracted with Rockwell International to build the DM. Engineers equipped one end of the DM with the standard Apollo probe-and-drogue docking mechanism and the other end with the androgynous system that linked up with its opposite half installed on the modified Soyuz spacecraft. During launch, the DM rested inside the Spacecraft Lunar Module (LM) Adaptor (SLA) atop the rocket’s upper stage, much like the LM during Apollo flights. Once in orbit, the astronauts separated the CSM from the upper stage, turned the spacecraft around, docked with the DM and pulled it free.
Workers lower the DM into Chamber B in the Space Environment Simulation Laboratory at NASA’s Johnson Space Center in Houston. Workers lower the DM into Chamber B in the Space Environment Simulation Laboratory at NASA’s Johnson Space Center in Houston. After extensive vacuum testing in Chamber B of the Space Environment Simulation Laboratory at NASA’s Johnson Space Center in Houston, the flight DM arrived at KSC on Oct. 29, 1974, and workers prepared it for more testing in a vacuum chamber in the MSOB. The flight DS arrived at KSC on Jan. 3, 1975, and two weeks later workers installed it on the DM. On Jan. 27, engineers lowered the DM onto the CM in the altitude chamber to conduct a mechanical docking test. Engineers conducted 10 days of joint tests of television and audio equipment to ensure systems compatibility.
Workers conduct a docking test of the Docking Module with the Command Module at NASA’s Kennedy Space Center in Florida. NASA support astronaut Robert Overmyer, right, works with engineers during compatibility testing. To be continued…
Major events around the world in January 1975:
January 5 – Musical The Wiz opens on Broadway, runs for 1,672 performances.
January 6 – The game show Wheel of Fortune debuts on NBC.
January 8 – Ella Grasso of Connecticut becomes the first elected female governor in the U.S.
January 11 – The S-II second stage of the Saturn V rocket that launched Skylab reenters the Earth’s atmosphere over the Indian Ocean.
January 12 – The Pittsburg Steelers beat the Minnesota Vikings in Super Bowl IX, played in Tulane Stadium in New Orleans.
January 15 – Space Mountain opens at Disney World in Orlando.
January 18 – The Jeffersons premieres on CBS.
January 22 – Launch of the Landsat-2 Earth resources monitoring satellite.
January 30 – Ernő Rubik applies for a patent in Hungary for his Magic Cube, later known as Rubik’s Cube.
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By NASA
3 min read
January’s Night Sky Notes: The Red Planet
by Kat Troche of the Astronomical Society of the Pacific
Have you looked up at the night sky this season and noticed a bright object sporting a reddish hue to the left of Orion? This is none other than the planet Mars! January will be an excellent opportunity to spot this planet and some of its details with a medium-sized telescope. Be sure to catch these three events this month.
Martian Retrograde
Mars entered retrograde (or backward movement relative to its usual direction) on December 7, 2024, and will continue throughout January into February 23, 2025. You can track the planet’s progress by sketching or photographing Mars’ position relative to nearby stars. Be consistent with your observations, taking them every few nights or so as the weather permits. You can use free software like Stellarium or Stellarium Web (the browser version) to help you navigate the night as Mars treks around the sky. You can find Mars above the eastern horizon after 8:00 PM local time.
This mid-January chart shows the path of Mars from September 2024 to June 2025 as it enters and then exits in retrograde motion. Mars appears to change its direction of motion in the sky because Earth is passing the slower-moving Mars in its orbit. Stellarium Hide and Seek
On the night of January 13th, you can watch Mars ‘disappear’ behind the Moon during an occultation. An occultation is when one celestial object passes directly in front of another, hiding the background object from view. This can happen with planets and stars in our night sky, depending on the orbit of an object and where you are on Earth, similar to eclipses.
A simulated view of the Moon as Mars begins its occultation on January 13, 2025. Stellarium Depending on where you are within the contiguous United States, you can watch this event with the naked eye, binoculars, or a small telescope. The occultation will happen for over an hour in some parts of the US. You can use websites like Stellarium Web or the Astronomical League’s ‘Moon Occults Mars’ chart to calculate the best time to see this event.
Closer and Closer
As you observe Mars this month to track its retrograde movement, you will notice that it will increase in brightness. This is because Mars will reach opposition by the evening of January 16th. Opposition happens when a planet is directly opposite the Sun, as seen from Earth. You don’t need to be in any specific city to observe this event; you only need clear skies to observe that it gets brighter. It’s also when Mars is closest to Earth, so you’ll see more details in a telescope.
Want a quick and easy way to illustrate what opposition is for Jupiter, Saturn, Mars, or other outer worlds? Follow the instructions on our Toolkit Hack: Illustrating Opposition with Exploring the Solar System page using our Exploring Our Solar System activity!
A mosaic of the Valles Marineris hemisphere of Mars projected into point perspective, a view similar to that which one would see from a spacecraft. The mosaic is composed of 102 Viking Orbiter images of Mars. NASA/JPL-Caltech Mars has fascinated humanity for centuries, with its earliest recorded observations dating back to the Bronze Age. By the 17th century, astronomers were able to identify features of the Martian surface, such as its ice caps and darker regions. Since the 1960s, exploration of the Red Planet has intensified with robotic missions from various space organizations. Currently, NASA has five active missions, including rovers and orbiters, with the future focused on human exploration and habitation. Mars will always fill us with a sense of wonder and adventure as we reach for its soil through initiatives such as the Moon to Mars Architecture and the Mars Sample Return campaign.
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