My Science School

Centaurs are icy planetesimals located between Jupiter and Neptune. They cross the orbits of one or more of the giant planets in their journey around the Sun, and interactions with these outer planets cause the orbits of Centaurs to be inherently unstable.

No centaur has been photographed up close, although there is evidence that Saturn's moon Phoebe, imaged by the Cassini probe in 2004, may be a captured centaur that originated in the Kuiper belt. In addition, the Hubble Space Telescope has gleaned some information about the surface features of 8405 Asbolus.

Of the objects known to occupy centaur-like orbits, approximately 30 have been found to display comet-like dust comas, with three, 2060 Chiron, 60558 Echeclus, and 29P/Schwassmann-Wachmann 1, having detectable levels of volatile production in orbits entirely beyond Jupiter.Chiron and Echeclus are therefore classified as both asteroids and comets, while Schwassmann-Wachmann 1 has always held a comet designation. Other centaurs, such as 52872 Okyrhoe, are suspected of having shown comas. Any centaur that is perturbed close enough to the Sun is expected to become a comet.

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In astronomy, a trojan is a small celestial body (mostly asteroids) that shares the orbit of a larger one, remaining in a stable orbit approximately 60° ahead or behind the main body near one of its Lagrangian points L4 and L5. Trojans can share the orbits of planets or of large moons.

In the Solar System, most known trojans share the orbit of Jupiter. They are divided into the Greek camp at L4 (ahead of Jupiter) and the Trojan camp at L5 (trailing Jupiter). More than a million Jupiter trojans larger than one kilometer are thought to exist, of which more than 7,000 are currently catalogued. In other planetary orbits only nine Mars trojans, 28 Neptune trojans, two Uranus trojans, and a single Earth trojan, have been found to date. A temporary Venus trojan is also known. Numerical orbital dynamics stability simulations indicate that Saturn and Uranus probably do not have any primordial trojans.

The same arrangement can appear when the primary object is a planet and the secondary is one of its moons, whereby much smaller trojan moons can share its orbit. All known trojan moons are part of the Saturn system. Telesto and Calypso are trojans of Tethys, and Helene and Polydeuces of Dione.

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The Voyager Golden Records are two phonograph records that were included aboard both Voyager spacecraft launched in 1977. The records contain sounds and images selected to portray the diversity of life and culture on Earth, and are intended for any intelligent extraterrestrial life form who may find them. The records are a sort of time capsule.

The Voyager 1 probe is currently the farthest human-made object from Earth. Both Voyager 1 and Voyager 2 have reached interstellar space, the region between stars where the galactic plasma is present. Like their predecessors Pioneer 10 and 11, which featured a simple plaque, both Voyager 1 and Voyager 2 were launched by NASA with a message aboard—a kind of time capsule, intended to communicate to extraterrestrials a story of the world of humans on Earth.

Voyager 1 was launched in 1977, passed the orbit of Pluto in 1990, and left the Solar System (in the sense of passing the termination shock) in November 2004. It is now in the Kuiper belt. In about 40,000 years, it and Voyager 2 will each come to within about 1.8 light-years of two separate stars: Voyager 1 will have approached star Gliese 445, located in the constellation Camelopardalis, and Voyager 2 will have approached star Ross 248, located in the constellation of Andromeda.

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A white hole is a bizarre cosmic object which is intensely bright, and from which matter gushes rather than disappears. In other words, it’s the exact opposite of a black hole. But unlike black holes, there’s no consensus about whether white holes exist, or how they’d be formed.

However, some theorists think that a combination of Einstein’s theory and quantum theory points to a new way of thinking about white holes. Instead of being the ‘exit’ from a wormhole, they may be a slow-motion replay of the formation of the original black hole.

The process starts when an old massive star collapses under its own weight and forms a black hole (see diagram, above). But then, quantum effects occurring around the surface of the black hole halt further collapse to a singularity, and instead begin to gradually turn the black hole into a white hole that’s spewing out the original star matter again. The process is mind-bendingly slow, though, so we may be in for a very long wait to find out if white holes really exist.

Credit : Science Focus

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Venus revolves or orbits around the Sun once every 0.615 Earth years, or once every 224.7 Earth days. Venus travels at an average speed of 78,341 miles per hour or 126,077 kilometers per hour in its orbit around the Sun.

The most likely explanations focus on fine particles, ice crystals, or even a chemical compound called iron chloride. Although it's much less likely, another possibility considered by scientists who study astrobiology is that these streaks could be made up of microbial life, Venus-style. Astrobiologists note that ring-shaped linkages of sulfur atoms, known to exist in Venus’ atmosphere, could provide microbes with a kind of coating that would protect them from sulfuric acid. These handy chemical cloaks would also absorb potentially damaging ultraviolet light and re-radiate it as visible light.

Some of the Russian Venera probes did, indeed, detect particles in Venus’ lower atmosphere about a micron in length – roughly the same size as a bacterium on Earth.

None of these findings provide compelling evidence for the existence of life in Venus’ clouds. But the questions they raise, along with Venus’ vanished ocean, its violently volcanic surface, and its hellish history, make a compelling case for a return to our temperamental sister planet. There is much, it would seem, that she can teach us.

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An inferior conjunction is when an object passes between us and the sun. Any object in space that orbits the sun closer than Earth’s orbit might pass through inferior conjunction from time to time, assuming its orbit lies more or less close to the ecliptic. Usually, though, when you hear the words inferior conjunction, astronomers are speaking of the planets Venus and Mercury, which orbit the sun inside Earth’s orbit. Astronomers sometimes refer to Venus and Mercury as inferior planets. When they’re at or near inferior conjunction, we can’t see them. They’re hidden in the sun’s glare. Occasionally, though, Venus or Mercury can be seen to transit across the sun’s disk at inferior conjunction. Consider also the moon. It passes between the Earth and sun at new moon once each month. Therefore, it would be correct, if a little weird, to say that the moon is at inferior conjunction when it’s at its new phase.

A superior conjunction is when an object passes behind the sun from our point of view. Think of Venus or Mercury again. Half of their conjunctions with the sun – when they are brought together with the sun on our sky’s dome – are inferior conjunctions, and half are superior conjunctions. It’s kind of fun to imagine them on an endless cycle of passing in front of the sun, as seen from Earth, then behind it, and back again, like watching squirrels running around a tree. Meanwhile, the superior planets – or planets farther from the sun than Earth such as Mars, Jupiter, Saturn, Uranus and Neptune – can never be at inferior conjunction. They can never pass between us and the sun. Thus the superior planets only have superior conjunctions.

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A "blood moon" happens when Earth's moon is in a total lunar eclipse. While it has no special astronomical significance, the view in the sky is striking as the usually whiteish moon becomes red or ruddy-brown. 

The next blood moon will happen during the total lunar eclipse of May 26, 2021, which will be visible from parts of North America, Australia, the Pacific and Asia. As the full moon phase passes through Earth's shadow, viewers will be treated to a celestial sight that won't appear again until May of 2022.

How red the moon appears can depend on how much pollution, cloud cover or debris there is in the atmosphere. For example, if an eclipse takes place shortly after a volcanic eruption, the particles in the atmosphere will make the moon look darker than usual.

While there are planets and moons all over the solar system, only Earth is lucky enough to experience lunar eclipses because its shadow is just large enough to cover the moon completely. The moon is slowly drifting away from our planet (at roughly 1.6 inches or 4 centimeters a year) and this situation won't persist forever. There are roughly two to four lunar eclipses every year, according to NASA, and each one is visible over about half the Earth.

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A lunar eclipse occurs when the Moon moves into the Earth's shadow. This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned with Earth between the other two, and only on the night of a full moon. 

The Moon can also look reddish because Earth’s atmosphere absorbs the other colors while it bends some sunlight toward the Moon. Sunlight bending through the atmosphere and absorbing other colors is also why sunsets are orange and red.

During a total lunar eclipse, the Moon is shining from all the sunrises and sunsets occurring on Earth!

You might be wondering why we don’t have a lunar eclipse every month as the Moon orbits Earth. It’s true that the Moon goes around Earth every month, but it doesn’t always get in Earth’s shadow. The Moon’s path around Earth is tilted compared to Earth’s orbit around the Sun. The Moon can be behind Earth but still get hit by light from the Sun.

Because they don’t happen every month, a lunar eclipse is a special event. Unlike solar eclipses, lots of people get to see each lunar eclipse. If you live on the nighttime half of Earth when the eclipse happens, you’ll be able to see it.

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