What is the smallest planet in the solar system?

what is the smallest planet in the solar system

The smallest planet in the solar system is the planet Mercury. Also the closest planet to the sun, Mercury is about 20 times smaller than Earth and orbits the Sun once every 87.969 Earth days. Although bright, Mercury is not easily seen from Earth as it is normally lost in the glare of the Sun. … Read more

What Did the Soviet Vega Probes Achieve During Their Mission and When Did Vega 1 Reach Halley’s Comet?

The USSR’s Martian program did not meet expectations, whereas its 1985 Vega probes to Venus and Halley’s comet were unmitigated successes. By 1985, international relations had eased to the point where the USSR, the United States, Europe, Brazil, and Australia all shared information on this venture. Vega 1 and Vega 2 were launched in December … Read more

Why Did NASA Put the Hubble Space Telescope In Space and Why Do Space Telescopes Take Sharper Images?

Since telescopes were first used by Galileo in the early seventeenth century, astronomers have dreamed of placing them where Earth’s atmosphere would not get in the way of viewing the universe. The Hubble Space Telescope (HST) fulfills that dream. The Hubble Space Telescope, a reflecting telescope, is not the largest telescope made on Earth. Its … Read more

Which Space Probes Were Sent To Observe Halley’s Comet and Why Was Giotto Knocked Out of the Comet’s Path?

An international fleet of probes were launched to intercept the orbit of Halley’s comet in 1986. The Soviet Vega 1 probe was the first to reach its destination, on March 6, coming within 5,000 miles (8,000 km) of the comet’s nucleus. Vega 2 arrived to take photos from a distance of 13,000 miles (21,000 km) … Read more

How Many Years Did NASA Spend Designing the Hubble Space Telescope and What Was The Hubble Telescope’s Mission?

NASA spent some 30 years thinking about, designing, creating, and testing a telescope that would be launched into orbit. The result, the Hubble Space Telescope, was ready for launch in 1985. Its mission would be to observe the solar system and the galaxies beyond it without the interference of Earth’s atmosphere. Early in 1986, however, … Read more

When Was the Hubble Space Telescope Launched Into Orbit and Who Is the Hubble Telescope Named After?

Fortunately, NASA made plans for repairing the Hubble Space Telescope throughout its projected 15-year orbit. Two months after the Hubble Space Telescope’s launch in 1990, it was discovered that the primary mirror had not been ground properly, among other problems. The telescope could not be focused. While this was a major embarrassment, the dangerous and … Read more

When Will There Be Human Settlements On Other Planets and What Would a Human Colony On the Moon Be Used For?

The idea of colonies of humans on the Moon or Mars lies not only between the pages of science fiction paperbacks. NASA has been planning a lunar base since the 1960s. Investment in the space shuttle program drew attention away from this goal, but interest has been revived. In 1991, veteran astronauts described some likely … Read more

What Is the Next Major NASA Mission and When Did the Spacecraft Cassini Reach the Planet Saturn?

Plans change all the time, due to budgetary and governmental constraints, but the next planned space spectacular is an extended trip around Saturn and a landing on its moon Titan. The mission is a collaborative effort between the ESA and NASA. The spacecraft Cassini, as it is called, has been partly developed from Mariner, Viking, … Read more

When Did NASA’s Voyager Probes Reach the Planet Jupiter and What Is the Farthest Human Made Object From Earth?

Voyager 2 was launched first, on August 20, 1977, but Voyager 1, launched on September 5, 1977, beat it to Jupiter. Voyager 1 made its closest pass on March 5, 1979, and collected detailed information about the planet and its moons. Voyager 2 got to Jupiter in July 1979. In November 1980, Voyager 1 transmitted … Read more

When Did NASA’s Viking Space Probe Land On the Planet Mars and Did the Viking 2 Lander Find Any Life On Mars?

Mariner probes had already orbited Mars, but NASA’s Viking program was designed specifically to land on the planet in search of, among other things, life. Viking 1 went into orbit around Mars on June 19, 1976. NASA planned to send a module to land on the surface on Independence Day, to celebrate the U.S. bicentennial, … Read more

When Was NASA’s Mars Global Surveyor Probe Launched and Why Did the Mission To Mars End Prematurely?

Launched on November 6, 1996, NASA’s Mars Global Surveyor probe was designed primarily to study past and present climate patterns, carry out studies of geology and natural resources to determine the possibility of Mars supporting manned missions; and, of course, to look for life. Many astronomers believe that signs of life on the planet point … Read more

What Probes Did the USSR Send To Venus and When Did Venera 7 Transmit Surface Images of the Planet Venus?

The Soviet Venera program focused on landing a probe on Venus, and ten Venera probes successfully landed on the planet. The first probes sent back data and images from within the planet’s atmosphere before being burned up by the incredible temperatures or crushed by the monumental atmospheric pressure. Venera 7 touched down on July 22, … Read more

When Did the USSR’s Mars Program Begin and How Many Mars Program Spacecraft Touched Down On Mars Successfully?

The USSR’s Mars program, which had probes named after the planet, had more than its fair share of misfortune, including failed launches, unsuccessful attempts to leave Earth’s orbit, completely missing Mars, and even death. Scientists set out to investigate the failed launch of an early probe; it exploded, killing most of the team. Out of … Read more

What Space Probes Has NASA Sent To Study the Sun and What Is the Purpose of Orbital Solar Observatories?

NASA developed a number of Orbital Solar Observatories (OSO), which were launched between 1962 and 1975. Their purpose was to observe the Sun’s ultraviolet, gamma, and X rays throughout an 11-year sunspot cycle. From 1973 to 1974, a special Apollo Telescope Mount (ATM) was attached to Skylab for observation of the Sun. The successor to … Read more

When Was The Space Station Freedom Proposed By NASA and How Much Does the International Space Station Cost?

Once the race to the Moon was over, attention could be refocused on long-range missions. The idea of a permanently manned, international space station came into favor. Funding was short and NASA’s first priority became the space shuttle, but in 1984, President Reagan announced in his inaugural speech that such a station would be next … Read more

What Are Space Probes Used For and Which Space Probes Have Visited Other Planets In Our Solar System?

Space probes are unmanned spacecraft fitted with instruments to gather and transmit data and images from space. Because the probes are self-sufficient, they can be sent where no person could survive: into orbit around the Sun, to the other planets, or even out beyond the solar system. The downside of unmanned probes is that malfunctions … Read more

Why Do We Send New Probes To the Same Planets and How Many New Moons Did Voyager 1 Discover Orbiting Jupiter?

Advances in understanding and technology, as well as the failure of some probes to perform their tasks, make it important to send probes time and again to the same planet. We don’t know what we will find when we receive information from a distant probe. Every probe sent to Jupiter, for example, raises more questions … Read more

Which Other Countries Besides the United States and Russia Have Space Programs and How Many Have Astronauts?

Most industrialized countries probably have some kind of space program. This is not to say that they all put people into space. Most concentrate on launching communications and/or surveillance satellites. Manned space flight is becoming more and more a cooperative international effort. For example, the Freedom space station, announced in President Ronald Reagan’s 1984 State … Read more

What Was the Purpose of The Spacelab Mission and When Was Spacelab First Launched Into Earth Orbit?

A joint space mission between NASA and the European Space Agency (ESA), Spacelab was first launched in November 1983. Spacelab is not a spacecraft in and of itself. It consists of varying modules that travel attached to the space shuttle for the purposes of conducting specific research. Spacelab allowed scientists to perform experiments in microgravity … Read more

Why Did Cosmonauts Fly Missions In Their Underwear and When Did Cosmonauts Start Wearing Space Suits?

Cosmonauts wear space suits now, at least during takeoff, landing, and docking. Originally, space suits were not required, and some cosmonauts flew in their underwear. But on June 29, 1971, when the three cosmonauts in Soyuz 11 undocked from the space station Salyut 1, an air release valve suddenly opened. Without the life-support systems of … Read more

What Was the First Space Station In the World and How Long Did the Soviet Salyut 1 Spend In Earth Orbit?

On April 19, 1971, the USSR launched the first manned space station, Salyut 1, into orbit around Earth. The station consisted of four compartments, and was meant to house three crew members for up to 4 weeks. The entry compartment had the docking equipment for the spacecraft that would carry cosmonauts to and from the … Read more

What Was the Space Shuttle Originally Designed For and How Many Astronauts Can the Space Shuttle Carry?

Originally, the space shuttle was meant to be a transport system to and from a space station. Due to financial cutbacks and shifts in priority at NASA, the space station never materialized back then, but the space shuttle did. The space shuttle became an orbiting laboratory as well a reusable spacecraft for transportation into space. … Read more

How Many Tragedies Have There Been In Space and What Was NASA’s First Fatal Accident On a Spacecraft?

Traveling in space is dangerous. No possibility of life exists beyond the support functions brought from Earth. Getting off and back onto Earth requires the use of highly volatile and dangerous materials. Space travelers are face-to-face not only with the laws of physics, but also their own mortality. The first fatal accident occurred on January … Read more

Why Are Space Suits Necessary To Protect Astronauts In Space and How Were Space Suits For NASA Developed?

Space suits are required by astronauts because body fluids would boil under the natural pressure in space. Even pilots of high-flying aircraft need pressurized suits, and NASA developed space suits for the Mercury astronauts from those originally worn by U.S. Navy jet pilots. Space suits have come a long way since Soviet cosmonauts flew in … Read more

How Were Gemini Space Suits Designed To Protect Astronauts and What Were NASA’s Gemini Space Suits Made of?

When astronauts began walking in space, their suits had to be further altered to give more mobility and comfort while providing more protection from micrometeorites and accidental rips and tears. The Gemini space suits were airtight casings enclosed by a layer of woven fishnet fabric that prevented ballooning when the suit was pressurized. A layer … Read more

How Were the Apollo Mission Space Suits For Lunar Landings Different From the Gemini Mission Space Suits?

Experience showed that overheating was a problem in the Gemini space suits. The Apollo space suits had a layer of fabric made of tubing through which cool liquid flowed. A layer of linen provided some comfort, and the use of rubber, nylon, and aluminum ensured protection. Life support had to be mobile, so a backpack … Read more

When Did the First Humans Land On the Moon and How Many Astronauts Were On the The Apollo 11 Mission?

After ten Apollo test missions, both manned and unmanned, Apollo 11 was launched on July 16, 1969. The astronauts on board were Commander Neil Armstrong, Lunar Module Pilot Edwin “Buzz” Aldrin, and Command Module Pilot Michael Collins. On July 20, 1969, Armstrong and Aldrin landed the lunar module Eagle on the Moon’s surface in the … Read more

How Many Modules Did NASA’s Apollo Spacecraft Have and How Was the Command Module Linked To the Lunar Module?

The Apollo spacecraft that sent American astronauts to the moon had two modules, the command module and the service module. The command module, where the three astronauts spent their time, measured 10 feet (3 m) x 12.5 feet (3.8 m). It had five windows and contained three couches for the astronauts; storage facilities; navigation, instrument, … Read more

Who Built the Saturn Rockets For the Apollo Space Missions and How Many Stages Did Saturn Rockets Have?

Saturn rockets, based on missiles developed by the U.S. Department of Defense, launched most of the Apollo missions. The Saturn rocket boosters were developed by a team of German rocket scientists led by Wernher von Braun to launch heavy payloads into space. They were originally meant as a military satellite launcher, but they were adopted … Read more

Who Was the First Person To Walk In Space and When Did Soviet Cosmonaut Alexei Leonov Perform His Space Walk?

On March 18, 1965, Alexei Leonov stepped out into space from his Vokshod 2 spacecraft, while his comrade Pavel Belyayev commanded the flight. Leonov wore a space suit and was connected to Vokshod 2 by a tether and radio communication. His space walk was successful, but Leonov’s space suit had expanded, and he was forced … Read more

What Was the First U.S. Spacecraft To Photograph the Moon and When Did Ranger 7 Transmit Lunar Images To Earth?

During the final 13 minutes before it crashed into the Moon, Ranger 7 sent back 4,316 photographs of the lunar surface. In 1965, two more Ranger satellites took pictures of the Moon before crashing, providing a total of more than 17,000 photographs. In February 1966, the USSR’s Luna 9 didn’t crash, but landed safely on … Read more

What Was the Last Lunar Lander of the Surveyor Program To Explore the Surface of the Moon and When?

Surveyor 7, launched on January 6, 1968, was the fifth and final spacecraft of in NASA’s Surveyor program to achieve a lunar soft landing. The spacecraft carried out equipments to test the Moon’s soil. Surveyor 7 scooped up lunar dust and rocks, and performed more than fifteen experiments on the soil, including tests to determine … Read more

Who Was the First Person In Space and How Long Was Yuri Gagarin’s Orbit Around the Earth?

John Glenn wasn’t the first person in space. The honor went to Soviet cosmonaut Yuri Gagarin, on April 21, 1961, almost a year before Glenn orbited the earth. The USSR reported a completely successful 1-hour and 48-minute orbit of the manned capsule Vostok 1. Later it was learned that trouble upon reentry caused the capsule’s … Read more

What Was NASA’s Second Human Spaceflight Program and How Many Manned Gemini Missions Were There?

Project Gemini was NASA’s second human spaceflight program, and consisted of 10 manned flights between 1965 and 1966. The American Gemini spacecraft were the first to carry two people into space. NASA used the Gemini program to develop techniques for advanced space travel, and to prepare for the Apollo missions, whose objective was to land … Read more

How Many Cosmonauts Did the Russian Spacecraft Vokshod 1 Carry Into Orbit and What Was the Altitude Record Set?

The USSR felt that they were lagging behind in the space race since the United States had sent two men, not just one, into space aboard Gemini 3. They converted the Vostok capsule, which had been designed for one cosmonaut, an astronaut in the Soviet, now Russian, space program, into a very cramped three-person spacecraft. … Read more

How Many Explorer Satellites Were Launched Into Space and What Was the Purpose of the Explorer Space Program?

Sixty-five Explorer satellites, all unmanned, were launched from Earth between 1958 and 1984, seven failed to launch successfully. They were all sent into space to collect data and conduct experiments on specific phenomena. The areas of study included radiation belts, magnetic fields, solar wind, electromagnetic rays, the ionosphere, and Halley’s comet. In the aftermath of … Read more

When Did the United States Begin Its First Manned Flight Program and What Does NASA Stand For?

After the Soviet space program’s launch of the world’s first artificial satellite on October 4, 1957, the U.S. Congress, alarmed by the threat to national security and technological leadership, urged immediate and swift action. In 1958, President Dwight D. Eisenhower established the National Aeronautics and Space Administration, or NASA for short, to run the country’s … Read more

When Did a Mercury Capsule First Orbit the Earth and Who Was On Board To Pilot the Spacecraft?

On September 13, 1961, a Mercury capsule was launched into orbit and, after one complete revolution, landed safely. On board was a simulation of an astronaut. Afterwards, a Mercury capsule successfully carried the chimpanzee Enos twice around Earth. Despite the astronauts’ test pilot experience NASA first intended for them to be “minor participants” during their … Read more

What Was the First Human Spaceflight Program of the United States and How Many Spaceflights Included Monkeys?

Project Mercury was the first human spaceflight program of the United States and ran from 1959 through 1963 at a cost of $384 million dollars. Four of the Project Mercury spaceflights included monkeys, or non-human primates. Sam, a Rhesus macaque, was launched on 4 December 1959 on Little Joe 2 to 85 km altitude. Miss … Read more

Who Was the First American To Orbit the Earth and How Long Did the Spacecraft Friendship 7 Spend In Orbit?

Astronaut John Glenn Jr. was the first American to orbit the Earth. After numerous delays, his Mercury capsule, named Friendship 7, took off on February 20, 1962, and kept him in orbit for 5 hours. During reentry, NASA suspected that the capsule’s heat shield, protection against the deadly heat of friction caused by falling through … Read more

Who Built the First Liquid Fueled Rocket In the World and When Was the First Liquid Fueled Rocket Launched?

In 1926, Robert Goddard, a rocket engineer, fired the first rocket propelled by liquid fuel, solid fuel had already been discounted as not powerful enough to send anything into space. The first flight of a vehicle powered by a liquid-rocket took place on March 16, 1926 at Auburn, Massachusetts. Goddard’s rocket reached a velocity of … Read more

When Was Sputnik Launched Into Orbit By the USSR and How Long Did the First Satellite Orbit the Earth?

On October 4, 1957, Sputnik 1 was launched in the former Soviet Union, in Kazakhstan, near the town of Leninsk. This represented the first successful space launch. Sputnik 1 was little more than a radio transmitter, but its 90-minute orbit of the Earth ushered in the space age. Apart from being a technological first, Sputnik … Read more

When Did the United States Launch Its First Satellite Into Space and Who Designed the Satellite Explorer 1?

The Soviet launch of Sputnik spurred the United States to get its first satellite, Explorer 1, into orbit. The National Advisory Committee on Aeronautics (NACA), the predecessor of the National Aeronautics and Space Administration (NASA), adopted a U.S. Navy plan called Vanguard to launch the country’s first satellite. However, the satellite’s test run, in December … Read more

Why Don’t Pluto and Neptune Collide When They Orbit the Sun and What Is the Planet Pluto’s Orbital Inclination?

Since the tiny Pluto crosses the gas giant’s path, it is reasonable to think that the two would collide. Perhaps Pluto would get caught by the larger planet’s gravitational force and become a satellite. This doesn’t happen because Pluto’s orbital inclination, the angle of its orbital plane is 17°, while Neptune’s is 1.8°. The two … Read more

How Is Pluto Different From the Other Outer Planets and Why Is Pluto’s Orbit Around the Sun So Chaotic?

Why Pluto is so different is not well understood, but it is obviously a unique planet. It is the farthest planet from the Sun, the smallest planet, and resembles the terrestrial planets more than its Jovian neighbors. Pluto has a peculiar orbit. It crosses Neptune’s orbital path so that at certain times Neptune is actually … Read more

Where Did Pluto Come From, How Did the Planet Pluto Get Its Name, and What Is the Planet Pluto Like?

Many astronomers believe that Pluto was an escaped moon of Neptune, knocked out of orbit by its largest current moon, Triton. This hypothesis has been heavily criticised because Pluto never comes near Neptune in its orbit. The discovery of Pluto made headlines across the globe, and its name was proposed by Venetia Burney, an eleven-year-old … Read more

How Was the Planet Pluto Discovered and How Long Did It Take Astronomers To Discover Pluto After Neptune?

When astronomer William Herschel identified Uranus in 1781, astronomers determined that there must be at least one more planet beyond it to cause the idiosyncracies of its orbit. This led to the discovery of the planet Neptune in 1846. But even Neptune’s existence did not justify the peculiarities of Uranus’s orbit. Another planet had to … Read more

Where Is Planet X Located, Why Was Pluto Called Planet X, and Why Hasn’t Planet X Been Found?

When Uranus was discovered in 1781, astronomers concluded that yet another, more distant, planet had to exist. Something, they figured, was exerting a strong gravitational influence on Uranus’s orbit. They called that something Planet X. The search for Planet X led to the identification of Neptune, but Neptune was not strong enough alone to so … Read more

What Is the Ninth Planet From the Sun, How Far Away Is Pluto, and Is Pluto a Planet, a Moon, or an Asteroid?

Some astronomers have questioned whether Pluto should be classified as a planet, rather than an errant moon or an asteroid. The does not generate light; it is less massive than a star; it wanders through constellations; and it orbits the Sun, just like the other planets. Pluto’s orbit, however, is decidedly peculiar. Pluto’s distance from … Read more

Who Discovered the Great Dark Spot On the Planet Neptune and How Big Is the Great Dark Spot On Neptune?

Neptune’s Great Dark Spot, like Jupiter’s Great Red Spot and Saturn’s Great White Spot, indicates an atmospheric storm. It is an anticyclone, a cyclone rotating in a counterclockwise direction, about the size of Earth that travels eastward about 8° south of the equator at a pace of 100 feet (30 m) per second. The Great … Read more

What Is the Planet Neptune’s Interior Made of and What Is the Composition of Neptune’s Atmosphere?

Neptune’s internal structure is very similar to that of the planet Uranus. Neptune and Uranus are often considered a sub-class of gas giant termed “ice giants”, due to their smaller size and higher concentrations of volatiles relative to the gas giants Jupiter and Saturn. The planet Neptune has a partly rocky, but mostly icy, core … Read more

How Cold Is the Planet Neptune and Why Is Neptune About the Same Temperature As Uranus?

Neptune is over 1 billion miles (1.6 billion km) farther away from the Sun than Uranus, but the two planets are close in temperature: –365°F (-220°C) on Neptune; –355°F (-214°C) on Uranus. This results from Neptune’s interior, which is not as solid as Uranus’s. A partially fluid core will experience more movement than a solid … Read more

What Are the Two Largest Moons of the Planet Uranus and What Are the Moons Titania and Oberon Made of?

The moons Titania and Oberon, the largest and most distant satellites of the planet Uranus, show different signs of cratering. On Titania, the craters are small, which probably means that the original large craters were eroded by some kind of geological force. Astronomers believe that large surface cracks, over 600 miles (960 km) long and … Read more

What Is the Closest Moon To the Planet Uranus, Who Discovered Miranda, and Who Is the Moon Miranda Named After?

Miranda, the closest of Uranus’s large moons, has a varied surface of craters, valleys, faults, ridges, and canyons. Three large regions have ridges and valleys reminiscent of a plowed field. One of the regions displays a large V-shape called a chevron. A system of canyons, some as deep as 12 miles (19 km), can be … Read more

What Is the Eighth Planet In the Solar System and How Is the Planet Neptune Similar To the Other Gas Giants?

Neptune, the eighth planet from the sun, is the smallest of the gas giants, and the farthest from the Sun. Its discovery, in 1846, came about through mathematical calculation, rather than simple observation. We knew little about Neptune before 1989, when the spacecraft Voyager 2 began photographing it. Voyager could observe only the southern hemisphere, … Read more

What Color Is the Planet Neptune and Why Is Neptune’s Atmosphere Bright Blue?

The planet Neptune has an atmosphere of hydrogen, helium, and methane, just as Uranus does. The methane, which lies in a haze over the planet’s thick cloud cover, absorbs the red end of the spectrum, reflecting the blues. Neptune’s vivid deep azure, however, is a little different from Uranus’s milder aquamarine. Neptune’s atmospheric methane content … Read more

How Was Neptune Discovered and How Did Astronomers Determine That the Planet Neptune Existed Beyond Uranus?

Galileo first observed Neptune on December 28, 1612, but he mistook Neptune for a fixed star when it appeared very close to Jupiter in the night sky. The search for Neptune began when astronomers noticed that Uranus’s movements, particularly its orbit, didn’t correspond to their expectations. One explanation was that another planet existed beyond Uranus, … Read more

How Did Sir Frederick William Herschel Discover the Planet Uranus and What Did Herschel Do Before Astronomy?

Sir Frederick William Herschel, born in 1738, led a varied and distinctive life. As a young man, he witnessed the Seven Years’ War in Europe while playing oboe in a military band. His music skills, and his winning personality, earned him an organist position in Bath, England. While there, his studies in musical harmony led … Read more