Category: sistemasolar

This photograph of Neptune’s southern …

This photograph of Neptune’s southern hemisphere was taken by the narrow-angle camera on NASA’s Voyager 2 when the spacecraft was 4.2 million km (2.6 million miles) from the planet.

Image credit: NASA/JPL

An Alien Spacecraft May Have Passed Through Ou…

Slightly more than one year ago, we spotted an object from another star traveling through our Solar System for the first time. There was some debate over whether it was a comet or an asteroid – but could it instead have been an alien spacecraft equipped with a solar sail?

Well, no. But still, two scientists have looked into the plausibility of such a scenario anyway, noting some peculiarities in the object – dubbed ‘Oumuamua – that could lend credence to such an explanation. The story was first picked up by Matt Williams at Universe Today.

Oumuamua was odd in that, as it swung past the Sun, it appeared to get a strange speed boost. Scientists have put this down to an outgassing event – with the object firing material from its surface like a jet as it was heated by the Sun.

Bialy and Loeb, however, argue against such an idea. They say the lack of additional rotation in the 400-meter-long object (1,300 feet) caused by the event makes it unlikely an outgassing event was the cause of the change in motion. Instead, they say the acceleration “may be explained by solar radiation pressure”.

“If radiation pressure is the accelerating force, then ‘Oumuamua represents a new class of thin interstellar material, either produced naturally, through a yet unknown process in the ISM [interstellar medium] or in proto-planetary disks, or of an artificial origin,” they write.

“Considering an artificial origin, one possibility is that ‘Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment.”

Such ideas have been considered on Earth for our own journeys to distant stars. The Breakthrough Starshot project, for example, proposed using a lightsail to reach our nearest star system – Alpha Centauri – within a generation.

If this were true for ‘Oumumamua, the duo are unsure whether the object was accidentally sent towards us – “equipment that is not operational any more” – or an operational probe “sent intentionally to Earth vicinity by an alien civilization.” They say it could have come from any star within 16,000 light-years.

Unfortunately, ‘Oumuamua is now too far from Earth to study it further, let alone visit it, and it will never return again. So we’ll never be able to test this theory, however ridiculous it might be.

“The key issue with this theory is that it cannot possibly be tested,” Dr René Heller from the Max Planck Institute for Solar System Research told IFLScience. “It is also an extraordinary claim without extraordinary evidence.”

source

Parker Solar Probe Breaks Record, Becomes Cl…

Parker Solar Probe Breaks Record, Becomes Closest Spacecraft to Sun

Parker Solar Probe now holds the record for closest approach to the Sun by a human-made object. The spacecraft passed the current record of 26.55 million miles from the Sun’s surface on Oct. 29, 2018, at about 1:04 p.m. EDT, as calculated by the Parker Solar Probe team.

The previous record for closest solar approach was set by the German-American Helios 2 spacecraft in April 1976. As the Parker Solar Probe mission progresses, the spacecraft will repeatedly break its own records, with a final close approach of 3.83 million miles from the Sun’s surface expected in 2024.

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On this day in 1989 the Galileo spacecraft was…

On this day in 1989 the Galileo spacecraft was launched to explore Jupiter and its moons.

Galileo was an American unmanned spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space Shuttle Atlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon, Dactyl, around 243 Ida. In 1994, Galileo observed Comet Shoemaker–Levy 9’s collision with Jupiter.

Jupiter’s atmospheric composition and ammonia clouds were recorded, the clouds possibly created by outflows from the lower depths of the atmosphere. Io’s volcanism and plasma interactions with Jupiter’s atmosphere were also recorded. The data Galileo collected supported the theory of a liquid ocean under the icy surface of Europa, and there were indications of similar liquid-saltwater layers under the surfaces of Ganymede and Callisto. Ganymede was shown to possess a magnetic field and the spacecraft found new evidence for exospheres around Europa, Ganymede, and Callisto. Galileo also discovered that Jupiter’s faint ring system consists of dust from impacts on the four small inner moons. The extent and structure of Jupiter’s magnetosphere was also mapped.

On September 21, 2003, after 14 years in space and 8 years in the Jovian system, Galileo’s mission was terminated by sending it into Jupiter’s atmosphere at a speed of over 48 kilometers per second (30 mi/s), eliminating the possibility of contaminating local moons with terrestrial bacteria. (source)

Johannes Kepler

Johannes Kepler

Johannes Kepler was a German mathematician, astronomer, and astrologer.

Kepler is a key figure in the 17th-century scientific revolution. He is best known for his laws of planetary motion, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican Astronomy. These works also provided one of the foundations for Isaac Newton’s theory of universal gravitation.

In astronomy, Kepler’s laws of planetary motion are three scientific laws describing the motion of planets around the Sun.

  • The orbit of a planet is an ellipse with the Sun at one of the two foci.
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  • A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
  • The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.
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Most planetary orbits are nearly circular, and careful observation and calculation are required in order to establish that they are not perfectly circular. Calculations of the orbit of Mars, whose published values are somewhat suspect, indicated an elliptical orbit. From this, Johannes Kepler inferred that other bodies in the Solar System, including those farther away from the Sun, also have elliptical orbits.

Kepler’s work (published between 1609 and 1619) improved the heliocentric theory of Nicolaus Copernicus, explaining how the planets’ speeds varied, and using elliptical orbits rather than circular orbits with epicycles.

Isaac Newton showed in 1687 that relationships like Kepler’s would apply in the Solar System to a good approximation, as a consequence of his own laws of motion and law of universal gravitation. 

On this day in 1846 the astronomer William Las…

On this day in 1846 the astronomer William Lassell discovered the largest moon of Neptune, Triton.

It is the only large moon in the Solar System with a retrograde orbit, an orbit in the direction opposite to its planet’s rotation. At 2,710 kilometres in diameter, it is the seventh-largest moon in the Solar System. Because of its retrograde orbit and composition similar to Pluto’s, Triton is thought to have been a dwarf planet captured from the Kuiper belt. Triton has a surface of mostly frozen nitrogen, a mostly water-ice crust, an icy mantle and a substantial core of rock and metal. The core makes up two-thirds of its total mass.

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All detailed knowledge of the surface of Triton was acquired from a distance of 40,000 km by the Voyager 2spacecraft during a single encounter in 1989. The 40% of Triton’s surface imaged by Voyager 2 revealed blocky outcrops, ridges, troughs, furrows, hollows, plateaus, icy plains and few craters.

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Triton is geologically active; its surface is young and has relatively few impact craters. Although Triton’s crust is made of various ices, its subsurface processes are similar to those that produce volcanoes and rift valleys on Earth, but with water and ammonia as opposed to liquid rock.

Triton’s entire surface is cut by complex valleys and ridges, probably the result of tectonics and icy volcanism. The vast majority of surface features on Triton are endogenic—the result of internal geological processes rather than external processes such as impacts. Most are volcanic and extrusive in nature, rather than tectonic

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The Voyager 2 probe observed in 1989 a handful of geyser-like eruptions of nitrogen gas and entrained dust from beneath the surface of Triton in plumes up to 8 km high.

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Triton is thus, along with Earth, Io, and Enceladus, one of the few bodies in the Solar System on which active eruptions of some sort have been observed. (source)

 images: NASA/JPL-Caltech/ISS 

Image of the planet Uranus observed by the Hub…

Image of the planet Uranus observed by the Hubble Space Telescope

Credit: NASA/ESA, M. Showalter (Stanford University/NASA/ESA Ames Research Center), J. Lissauer (NASA/ESA Ames Research Center)

The heliosphere is the bubble-like region of s…

The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto. Plasma “blown” out from the Sun, known as the solar wind, creates and maintains this bubble against the outside pressure of the interstellar medium, the hydrogen and helium gas that permeates the Milky Way Galaxy. The solar wind flows outward from the Sun until encountering the termination shock, where motion slows abruptly. The Voyager spacecraft have explored the outer reaches of the heliosphere, passing through the shock and entering the heliosheath, a transitional region which is in turn bounded by the outermost edge of the heliosphere, called the heliopause.
The shape of the heliosphere is controlled by the interstellar medium
through which it is traveling, as well as the Sun and is not perfectly
spherical. The limited data available and unexplored nature of these structures have resulted in many theories. The word “heliosphere” is said to have been coined by Alexander J. Dessler, who is credited with first use of the word in the scientific literature.

On September 12, 2013, NASA announced that Voyager 1 left the heliopause on August 25, 2012, when it measured a sudden increase in plasma density of about forty times. Because the heliopause marks one boundary
between the Sun’s solar wind and the rest of the galaxy, a spacecraft
such as Voyager 1 which has departed the heliosphere, can be said to
have reached interstellar space. source

Saturn and its moons at opposition (The visi…

Saturn and its moons at opposition (The visible moons are (from left to right) Dione, Enceladus, Tethys, Janus, Epimetheus and Mimas

Credit:

NASA, ESA, A. Simon (GSFC) and the OPAL Team, and J. DePasquale (STScI)

On this day in 1977 was launched the space pro…

On this day in 1977 was launched the space probe Voyager 1.

Voyager 1 is a space probe launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 launched 16 days after its twin, Voyager 2. Having operated for 41 years as of September 5, 2018, the spacecraft still communicates with the Deep Space Network to receive routine commands and return data. At a distance of 142.31 astronomical units from the Sun as of June 4, 2018, it is the most distant man-made object from Earth.

The probe’s objectives included flybys of Jupiter, Saturn, and Saturn’s largest moon, Titan. While the spacecraft’s course could have been altered to include a Pluto encounter by forgoing the Titan flyby, exploration of the moon, which was known to have a substantial atmosphere, took priority. It studied the weather, magnetic fields and rings of the two planets and was the first probe to provide detailed images of their moons. (read more)

Voyager 1 Trajectory through the Solar System