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By NASA
3 Min Read September’s Night Sky Notes: Marvelous Moons
Jupiter’s largest moons, from left to right: Io, Europa, Ganymede, Callisto. Credits:
NASA by Kat Troche of the Astronomical Society of the Pacific
September brings the gas giants Jupiter and Saturn back into view, along with their satellites. And while we organize celebrations to observe our own Moon this month, be sure to grab a telescope or binoculars to see other moons within our Solar System! We recommend observing these moons (and planets!) when they are at their highest in the night sky, to get the best possible unobstructed views.
The More the Merrier
As of September 2024, the ringed planet Saturn has 146 identified moons in its orbit. These celestial bodies range in size; the smallest being a few hundred feet across, to Titan, the second largest moon in our solar system.
The Saturnian system along with various moons around the planet Saturn: Iapetus, Titan, Enceladus, Rhea, Tethys, and Dione. Stellarium Web Even at nearly 900 million miles away, Titan can be easily spotted next to Saturn with a 4-inch telescope, under urban and suburban skies, due to its sheer size. With an atmosphere of mostly nitrogen with traces of hydrogen and methane, Titan was briefly explored in 2005 with the Huygens probe as part of the Cassini-Huygens mission, providing more information about the surface of Titan. NASA’s mission Dragonfly is set to explore the surface of Titan in the 2030s.
Enceladus is an icy world much like Hoth, except that it has an ocean under its frozen crust. Astronomers believe this moon of Saturn may be a good candidate for having extraterrestrial life beneath its surface. NASA/ESA/JPL-Caltech/Space Science Institute Saturn’s moon Enceladus was also explored by the Cassini mission, revealing plumes of ice that erupt from below the surface, adding to the brilliance of Saturn’s rings. Much like our own Moon, Enceladus remains tidally locked with Saturn, presenting the same side towards its host planet at all times.
The Galilean Gang
The King of the Planets might not have the most moons, but four of Jupiter’s 95 moons are definitely the easiest to see with a small pair of binoculars or a small telescope because they form a clear line. The Galilean Moons – Ganymede, Callisto, Io, and Europa – were first discovered in 1610 and they continue to amaze stargazers across the globe.
The Jovian system: Europa, Io, Ganymede, and Callisto. Stellarium Web Ganymede: largest moon in our solar system, and larger than the planet Mercury, Ganymede has its own magnetic field and a possible saltwater ocean beneath the surface. Callisto: this heavily cratered moon is the third largest in our solar system. Although Callisto is the furthest away of the Galilean moons, it only takes 17 days to complete an orbit around Jupiter. Io: the closest moon and third largest in this system, Io is an extremely active world, due to the push and pull of Jupiter’s gravity. The volcanic activity of this rocky world is so intense that it can be seen from some of the largest telescopes here on Earth. Europa: Jupiter’s smallest moon also happens to be the strongest candidate for a liquid ocean beneath the surface. NASA’s Europa Clipper is set to launch October 2024 and will determine if this moon has conditions suitable to support life. Want to learn more? Rewatch the July 2023 Night Sky Network webinar about Europa Clipper here. Be sure to celebrate International Observe the Moon Night here on Earth September 14, 2024, leading up to the super full moon on September 17th! You can learn more about supermoons in our mid-month article on the Night Sky Network page!
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By European Space Agency
On 8 September 2024, the first of four Cluster satellites will return home and burn up in the Earth’s atmosphere in an uncontrolled ‘targeted reentry’ over a remote area of the South Pacific Ocean.
In the nearly 70 years of spaceflight about 10 000 intact satellites and rocket bodies have reentered the atmosphere. Yet we still lack a clear view on what actually happens during a reentry.
An airborne observation experiment will now attempt to witness the ‘Salsa’ (Cluster 2) reentry. Scientists onboard a small plane will try to collect rare data on how and when a satellite breaks up, which can be used to make satellite reentries safer and more sustainable in the future.
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By NASA
2 min read
Hubble Reaches a Lonely Light in the Dark
NASA, ESA, C. Gallart (Instituto de Astrofisica de Canarias), A. del Pino Molina (Centro de Estudios de Fisica del Cosmos de Aragon), and R. van der Marel (Space Telescope Science Institute); Image Processing: Gladys Kober (NASA/Catholic University of America) A splatter of stars glows faintly at almost 3 million light-years away in this new image from NASA’s Hubble Space Telescope. Known as the Tucana Dwarf for lying in the constellation Tucana, this dwarf galaxy contains a loose bundle of aging stars at the far edge of the Local Group, an aggregation of galaxies including our Milky Way, bound together by gravity. The Tucana Dwarf was discovered in 1990 by R.J. Lavery, the same year Hubble launched.
What makes the Tucana Dwarf distinct from other dwarf galaxies comes in two parts: its classification, and its isolation. As a dwarf spheroidal galaxy, it is much smaller and less luminous than most other dwarf galaxies. Dust is sparse and the stellar population skews towards the older range, giving them a dimmer look. Additionally, the Tucana Dwarf lies about 3.6 million light-years from the Local Group’s center of mass, far from the Milky Way and other galaxies. It is only one of two dwarf spheroidal galaxies in the Local Group to be this remote, making astronomers theorize that a close encounter with a larger galactic neighbor called Andromeda slingshotted it into the distance about 11 billion years ago.
Having such pristine properties enables scientists to use the Tucana Dwarf as a cosmic fossil. Dwarf galaxies could be the early ingredients for larger galaxies, and with older stars residing in such an isolated environment, analyzing them can help trace galaxy formation back to the dawn of time. For that reason, Hubble reached far across the Local Group using the capabilities of the Advanced Camera for Surveys and Wide Field and Planetary Camera 2 to meet this distant, lonely galaxy. Examining its structure, composition, and star formation history sheds light on the epoch of reionization, when the first stars and galaxies arose from the dark billions of years ago.
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Hubble’s Galaxies
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov
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Last Updated Aug 23, 2024 Editor Michelle Belleville Location NASA Goddard Space Flight Center Related Terms
Astrophysics Galaxies Goddard Space Flight Center Hubble Space Telescope Stars Keep Exploring Discover More Topics From NASA
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
Hubble Science
Hubble’s Galaxies
Stars
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By European Space Agency
On 8 September 2024, the first of four satellites that make up ESA’s Cluster mission will reenter Earth’s atmosphere over the South Pacific Ocean Uninhabited Area.
This marks the end of the historic mission, over 24 years after it was sent into space to measure Earth’s magnetic environment. Though the remaining three satellites will also stop making scientific observations, discoveries using existing mission data are expected for years to come.
This ‘targeted reentry’ is the first of its kind. ESA’s efforts to ensure a clean end to the Cluster mission go beyond international standards, making the agency a world-leader in sustainable space exploration.
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By NASA
NASA This view of the Earth’s crest over the lunar horizon was taken on July 29, 1971, during the Apollo 15 lunar landing mission. Astronauts David Scott, Alfred Worden, and James Irwin launched from NASA’s Kennedy Space Center in Florida aboard a Saturn V launch vehicle.
Designed to explore the Moon over longer periods, greater ranges, and with more instruments for the collection of scientific data than before, Apollo 15 included the introduction of a $40 million lunar roving vehicle (LRV) that reached a top speed of 10 mph (16 kph) across the Moon’s surface.
Upon landing on the Moon at the Hadley-Apennine site, Scott and Irwin conducted four spacewalks, including three excursions using the LRV, for a combined total of 19 hours. Worden remained in orbit aboard the command module Endeavour.
See more photos from the Apollo 15 mission.
Image credit: NASA
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