Articles on exploits in space.

MYSTERIES OF THE OORT CLOUD AT THE EDGE OF OUR SOLAR SYSTEM


The entirely theoretical cloud of icy space debris marks the frontiers of our solar system.



The Oort cloud represents the very edges of our solar system. The thinly dispersed collection of icy material starts roughly 200 times farther away from the sun than Pluto and stretches halfway to our sun’s nearest starry neighbor, Alpha Centauri. We know so little about it that its very existence is theoretical — the material that makes up this cloud has never been glimpsed by even our most powerful telescopes, except when some of it breaks free.

“For the foreseeable future, the bodies in the Oort cloud are too far away to be directly imaged,” says a spokesperson from NASA. “They are small, faint, and moving slowly.”

Aside from theoretical models, most of what we know about this mysterious area is told from the visitors that sometimes swing our way every 200 years or more — long period comets. “[The comets] have very important information about the origin of the solar system,” says Jorge Correa Otto, a planetary scientist the Argentina National Scientific and Technical Research Council (CONICET).

A Faint Cloud, in Theory
The Oort cloud’s inner edge is believed to begin roughly 1,000 to 2,000 astronomical units from our sun. Since an astronomical unit is measured as the distance between the Earth and the sun, this means it’s at least a thousand times farther from the sun than we are. The outer edge is thought to go as far as 100,000 astronomical units away, which is halfway to Alpha Centauri. “Most of our knowledge about the structure of the Oort cloud comes from theoretical modeling of the formation and evolution of the solar system,” the NASA spokesperson says.

While there are many theories about its formation and existence, many believe that the Oort cloud was created when many of the planets in our solar system were formed roughly 4.6 billion years ago. Similar to the way the Asteroid Belt between Mars and Jupiter sprung to life, the Oort cloud likely represents material left over from the formation of giant planets like Jupiter, Neptune, Uranus and Saturn. The movements of these planets as they came to occupy their current positions pushed that material past Neptune’s orbit, Correa Otto says.

Another recent study holds that some of the material in the Oort cloud may be gathered as our sun “steals comets” orbiting other stars. Basically, the theory is that comets with extremely long distances around our neighboring stars get diverted when coming into closer range to our sun, at which point they stick around in the Oort cloud.

The composition of the icy objects that form the Oort cloud is thought to be similar to that of the Kuiper Belt, a flat, disk-shaped area beyond the orbit of Neptune we know more about. The Kuiper Belt also consists of icy objects leftover from planet formation in the early history of our solar system. Pluto is probably the most famous object in this area, though NASA’s New Horizons space probe flew by another double-lobed object in 2019 called Arrokoth — currently the most distant object in our solar system explored up close, according to NASA.

“Bodies in the Oort cloud, Kuiper belt, and the inner solar system are all believed to have formed together, and gravitational dynamics in the solar system kicked some of them out,” the NASA spokesperson says.



Estonian philosopher Ernst Öpik first theorized that long-period comets might come from an area at the edge of our solar system. Then, Dutch astronomer Jan Oort predicted the existence of his cloud in the 1950s to better understand the paradox of long-period comets.

Oort's theory was that comets would eventually strike the sun or a planet, or get ejected from the solar system when coming into closer contact with the strong orbit of one of those large bodies. Furthermore, the tails that we see on comets are made of gasses burned off from the sun’s radiation. If they made too many passes close to the sun, this material would have burned off. So they must not have spent all their existence in their current orbits. “Occasionally, Oort cloud bodies will get kicked out of their orbits, probably due to gravitational interactions with other Oort cloud bodies, and come visit the inner solar system as comets,” the NASA spokesperson says.

Correa Otto says that the direction of comets also supports the Oort cloud’s spherical shape. If it was shaped more like a disk, similar to the Kuiper Belt, comets would follow a more predictable direction. But the comets that pass by us come from random directions. As such, it seems the Oort cloud is more of a shell or bubble around our solar system than a disk like the Kuiper Belt. These long-period comets include C/2013 A1 Siding Spring, which passed close to Mars in 2014 and won’t be seen again for another 740,000 years.

“No object has been observed in the distant Oort cloud itself, leaving it a theoretical concept for the time being. But it remains the most widely-accepted explanation for the origin of long-period comets,” NASA says.

The Oort cloud, if it indeed exists, likely isn’t unique to our own solar system. Correa Otto says that some astronomers believe these clouds exist around many solar systems. The trouble is, we can’t even yet see our own, let alone those of our neighboring systems. The Voyager 1 spacecraft is headed in that direction — it’s projected to reach the inner edge of our Oort cloud in roughly 300 years. Unfortunately, Voyager will have long since stopped working.

“Even if it did [still work], the Sun’s light is so faint, and the distances so vast, that it would be unlikely to fly close enough to something to image it,” the NASA spokesperson says. In other words, it would be difficult to tell you’re in the Oort cloud even if you were right inside it.

Oort cloud

HAS ANY HUMAN MADE OBJECT LEFT OUR SOLAR SYSTEM? EVER?

Of the major spacecraft, Voyager 1, Voyager 2, and New Horizons are still functioning and are regularly contacted by radio communication, while Pioneer 10 and Pioneer 11 are now derelict.

These objects are leaving the Solar System because their velocity and direction are taking them away from the Sun, and at their distance from the Sun, its gravitational pull is not sufficient to pull these objects back or into orbit. They are not impervious to the gravitational pull of the Sun and are being slowed, but are still traveling in excess of escape velocity to leave the Solar System and coast into interstellar space.

Pioneer 10 –

launched in 1972, flew past Jupiter in 1973 and is heading in the direction of Aldebaran (65 light years away) in the constellation of Taurus. Contact was lost in January 2003, and it is estimated to have passed 120 astronomical units (AU; one AU is roughly the average distance between Earth and the Sun: 150 million kilometers (93 million miles)

Pioneer 11 –

launched in 1973, flew past Jupiter in 1974 and Saturn in 1979. Contact was lost in November 1995, and it is estimated to be at around 100 AU. The spacecraft is headed toward the constellation of Aquila, northwest of the constellation of Sagittarius. Barring an incident, Pioneer 11 will pass near one of the stars in the constellation in about 4 million years.

Voyager 2 – launched in August 1977, flew past Jupiter in 1979, Saturn in 1981, Uranus in 1986, and Neptune in 1989. The probe left the heliosphere for interstellar space at 119 AU on 5 November 2018. Voyager 2 is still active. It is not headed toward any particular star, although in roughly 40,000 years it should pass 1.7 light-years from the star Ross 248. If undisturbed for 296,000 years, it should pass by the star Sirius at a distance of 4.3 light-years

Voyager 1 – launched in September 1977, flew past Jupiter in 1979 and Saturn in 1980, making a special close approach to Saturn's moon Titan. The probe passed the heliopause at 121 AU on 25 August 2012 to enter interstellar space. Voyager 1 is still active. It is headed towards an encounter with star Gliese 445 (AC +79 3888), which lies 17.6 light-years from Earth, in about 40,000 years.

New Horizons – launched in 2006, the probe flew past Jupiter in 2007 and Pluto on 14 July 2015. It flew past the Kuiper belt object 486958 Arrokoth on January 1, 2019, as part of the Kuiper Belt Extended Mission (KEM).

HOW MANY PLANETS DO WE HAVE IN OUR SOLAR SYSTEM

There are eight planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

The four inner solar system planets (Mercury, Venus, Earth, and Mars) fall under the category of terrestrial planets;

Jupiter and Saturn are gas giants (giant plants composed mostly of hydrogen and helium)

while Uranus and Neptune are the ice giants (containing mainly elements heavier than hydrogen and helium).


Pluto, a dwarf planet, was classified as one of the solar system planets when it was first discovered by Clyde Tombaugh. However, it is now considered to be one of the largest known members of the Kuiper Belt — a collection of icy bodies on the outer fringes of the solar system. Pluto was demoted from its planetary status in 2006 when a body of scientists decided a formalized definition for the term “planet.”

According to the International Astronomical Union's definition, a planet is “a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.” Because Pluto is part of the Kuiper Belt, and therefore has not met the third criterion, it is no longer considered a planet. Instead, it is classified as a dwarf planet.
Other dwarf planets include Ceres, Haumea, Makemake, and Eris.

With an atmosphere, stark surface features, and at least five moons, Pluto is the most complex dwarf planet we know, and one of the most surprising solar system planets. New Horizons flew by our favorite dwarf planet in July 2015 and scientists continue to uncover surprising details about this faraway world.

Order of planets

HOW MANY SPACE STATIONS HAVE HUMANS BUILT TO LIVE IN SPACE.

A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. Stations must have docking ports to allow other spacecraft to dock to transfer crew and supplies.

Since 1971, 12 space stations launched into a low orbit around Earth have been occupied for varying lengths of time. In chronological order they are Salyut 1, Skylab, Salyuts 3, 4, 5, 6, and 7, Mir, the International Space Station, Tiangongs 1 and 2, and a larger Chinese space station simply called Tiangong

SALYUT

The Salyut programme was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research space stations and two crewed military reconnaissance space stations over a period of 15 years, from 1971 to 1986.

SKYLAB

Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4.

MIR

Mir was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996. It had a greater mass than any previous spacecraft.
In June 1997, an unmanned supply vessel crashed into the Mir space station. The collision meant that the station began to leak air. The astronauts on board desperately tried to seal the leak.
The Russian space station Mir ended its mission on 23 March 2001, when it was brought out of its orbit, entered the atmosphere and was destroyed. ... The atmospheric entry at the altitude of 100 kilometres (62 mi) occurred at 05:44 UTC near Nadi, Fiji.

INTERNATIONAL SPACE STATION

The International Space Station is a modular space station in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA, Roscosmos, JAXA, ESA, and CSA. The ownership and use of the space station is established by intergovernmental treaties and agreements.
In February, the Crew-1 astronauts passed the record for the most days in space by a crew launched on a U.S. spacecraft, surpassing the milestone of 84 days that was set by the Skylab 4 crew in 1974. Since then, they have doubled that record, staying onboard the International Space Station for 168 days

TIANGONG


The first crewed mission, Shenzhou 9, arrived at Tiangong 1 in June 2012. Shenzhou 8 and 9 were, respectively, China’s first uncrewed and crewed space docking. Shenzhou 10, the last crewed flight to visit Tiangong 1, arrived in June 2013. Chinese engineers monitored Tiangong 1 until March 2016, when they ended communications with the station. Tiangong 1 reentered Earth’s atmosphere in April 2018.


Tiangong 2 launched on September 15, 2016. Only one spaceflight, Shenzhou 11, visited Tiangong 2. Two astronauts stayed aboard the station for 33 days beginning in October 2016. An uncrewed cargo spacecraft, Tianzhou 1, performed docking and refueling maneuvers with the station in 2017. Tiangong 2 reentered Earth’s atmosphere in July 2019.


Tiangong space station will have three modules: the core module, Tianhe, was launched in 2021, and two science modules, Wentian and Mengtian, will follow. The first crewed mission, Shenzhou 12, carried three astronauts and docked with Tianhe in June 2021. The new space station is planned to share its orbit with the Xuntian space telescope to allow astronauts to easily repair and upgrade the telescope. Like Tiangong 2, the station will be serviced by Tianzhou spacecraft.