Category: Astronomy

Ancient people have known about the planets for millennia. It was only in the last few hundred years that new planets have been discovered that required a telescope to see. The earliest people thought of the planets as divine beings, moving across the heavens in unpredictable ways. If you’re wondering about the discovery of Mercury, though, it’s been known since prehistoric times, so there’s no way to really know who made the original discovery of planet mercury.

The five original naked-eye planets were Mercury, Venus, Mars, Jupiter and Saturn, and they had a significant impact on mythology, cosmology, and ancient astronomy. Any caveman could have made the Mercury discovery.

Mercury itself has been mentioned as early as the 2nd millennium BC by the Sumerians, and recorded by the Babylonians – they called the planet Nabu. The ancient Greeks associated Mercury with the god Hermes, who was thought to carry the Sun across the sky in his chariot. Later the Greeks called the planet Apollo when it was visible in the morning sky, and then Hermes in the evening sky. The Romans named the planet after the Roman messenger god Mercury, who was the same mythological figure as the Greek god Hermes.

The first telescopic observations were made by Galileo in the 17th century with his crude telescope; unfortunately, his crude instrument wasn’t powerful enough to see that the planet had phases, like Venus.

Mercury can occasionally be seen to pass directly in front of the Sun, as seen by Earth. This is called a transit. The last transit of Mercury happened in 2004, and was broadcasted worldwide across the Internet. But the first Mercury transit was seen in 1737 by John Bevis at the Royal Greenwich Observatory.

Until the 1960s, Mercury was thought to be tidally locked to the Sun, always facing one side towards our star. There were skeptics, who noted that if Mercury always faced one side towards the Sun, it should have a hot and a cold side, but research data didn’t back that up. Astronomers thought that maybe an atmosphere around Mercury kept the temperatures more even.

In 1962, Soviet scientists bounced the first radar signals off Mercury’s surface, and then American astronomers calculated that Mercury does rotate. It actually takes 59 days to turn once, and not the 88 days it takes to complete an orbit.

The first spacecraft to see Mercury up close was Mariner 10 back in 1974. Unfortunately, it was only able to see one hemisphere of the planet in total over the course of 3 flybys. Many of the missing pieces were filled in by NASA’s MESSENGER spacecraft, which completed its first flyby in January, 2008.

Descubrimiento del planeta Mercurio

References:
NASA Cosmic Distance Scales
NASA Solar System Exploration: Mariner 10

We can’t just talk about Mercury. Sometimes you’ve just got to see it. Before NASA’s MESSENGER spacecraft, there weren’t a lot of Mercury pictures to choose from. But now the floodgates are open, MESSENGER is sending back more pics of Mercury with each flyby. So here are some of the best photos of Mercury taken so far. I also recommend you to read these amazing books for more information about the planet Mercury.

This first image of Mercury was actually taken by NASA’s Mariner 10 spacecraft, while the others were seen by MESSENGER. As you can see, the new images are so much better than the older ones.

---

This is one of the first close-up images of Mercury captured by NASA’s MESSENGER spacecraft just before its January 14th, 2008 flyby. It’s a full color image of Mercury, captured by the spacecraft’s Wide Angle Camera (WAC) filters in the infrared, far red, and violet wavelengths (red, green, and blue filters for this image.)

---

This image of Mercury was captured when the spacecraft was much closer to the planet. The prominent feature is crater Matisse, named after the French artist Henri Matisse. This same crater was imaged by Mariner 10, so this gives scientists a chance to see the difference.

---

Here’s an image of Mercury’s north pole, captured by MESSENGER during its January 14, 2008 flyby. It’s interesting to note that the planet’s southern regions are much more heavily cratered than its northern regions, which are relatively smooth in comparison. If you read the interesting facts about Mercury, you would know that there could be craters at the planet’s north pole that harbor deposits of ice.

---

This is a side of Mercury that had never been seen by spacecraft until NASA’s MESSENGER arrived to photograph it on January 14, 2008. Until now, astronomers had only made ground observations of this side of the planet. These images will help astronomers tune their methods and let them compare their ground observations to the close up images captured by spacecraft.

Here are some facts about Mercury.

When you imagine cold, icy Pluto, orbiting in the distant regions of the Solar System, you imagine snowy white ball.

You can also look through these books from Amazon.com if you want more information about Pluto.

But images of Pluto, captured by the Hubble Space Telescope have shown that Pluto’s surface isn’t just pure ice. Instead, it has a dirty yellow color, with darker and brighter regions across its surface. Hubble studied the entire surface of Pluto as it rotated through a 6.4 day period.

The images revealed almost a dozen distinctive features never before seen by astronomers. This included a “ragged” northern polar cap cut in half by a dark strip, a bright spot seen to rotate around the dwarf planet, and a cluster of dark spots. The images also confirmed the presence of icy-bright polar cap features.

Some of the variations seen on Pluto’s surface could be topographic features, like basins and fresh impact craters. But most of them are probably caused by the complex distribution of frosts that move across Pluto’s surface during its orbital and seasonal cycles.

The surface area of Pluto is 1.795 x 10⁷ square kilometers; about 0.033% the surface area of Earth.

When Pluto is furthest away from the Sun, gases like nitrogen, carbon monoxide and methane partially freeze onto its surface.

All will be revealed when NASA’s New Horizons spacecraft finally arrives at Pluto in 2015, finally capturing close-up pictures of Pluto and its moon Charon.

You’re thinking about a certain Disney dog, aren’t you? Goofy’s pet dog? Nope, it was actually named after Pluto, the Roman god of the underworld.

You can also look through these books from Amazon.com if you want more information about Pluto.

When Pluto was first discovered by Clyde Tombaugh in 1930, he was given the honor of giving it a name. Although they were calling it Planet X informally, they needed something that matched the rest of the planets in the Solar System.

The name Pluto was suggested by Venetia Burney, an 11-year old school girl in England. She was interested in ancient mythology, and thought that Hades, the Greek god of the underworld, made a good name. She suggested Pluto, to match the Roman god names given to the other planets.

Each astronomer in the Lowell Observatory was allowed to vote on a short list of names: Minerva, Cronus, and Pluto. Every one of them voted for Pluto. Venetia was given a 5-pound reward for providing the name.

In other languages, the name has been translated to names that match underworld god mythology, such as Yama, the Guardian of Hell in Buddhist mythology.

In everything but the largest telescopes, Pluto appears as a tiny dot. And determining mass from so little information is incredibly hard to do.

Astronomers could only try and work out its mass by knowing how bright it was – its albedo. They could detect that it had large quantities of methane ice on its surface, and so astronomers knew that it had to be very bright. But there were sure about Pluto’s size, or even if it was larger than Mercury or Earth’s moon.

But astronomers lucked out in 1978 when James Christy discovered Pluto’s moon Charon. Once you get a system where two objects are orbiting one another, such as in the case of Pluto and Charon, you can use Newton’s formulation of Kepler’s Law to work out the mass very precisely.

Plugging in the orbital information for Pluto and its moon Charon, astronomers calculated its mass to be 1.31 x 10²² kg – less than 0.24% the mass of Earth. Followup observations were able to determine its size very accurately as 2,390 km across.You can also look through these books from Amazon.com if you want more information about Pluto.

[/caption]
With such a large distance from the Sun, Pluto is incredibly cold. But this temperature can vary enough to change the dwarf planet significantly. At its closest point, it warms up enough so that Pluto’s nitrogen atmosphere sublimates and forms a diffuse cloud around it. As Pluto gets further away from the Sun; however its this atmosphere freezes out, and falls to the surface of Pluto like snow.

First, let’s define some measurements. Room temperature is considered 21-degrees Celsius or 70-degrees Fahrenheit. The freezing point of water is 0-degrees Celsius or 32-degrees Fahrenheit. But when you’re measuring temperatures on Pluto, you really want to use Kelvin.

Zero Kelvin is the absolute zero temperature; a theoretical maximum point where no more energy can be extracted from a system. 0-degrees Kelvin corresponds to -273-degrees Celsius.

The surface of Pluto, in comparison, can range from a low temperature of 33 Kelvin (-240 degrees Celsius or -400 degrees Fahrenheit) and 55 Kelvin (-218 degrees Celsius or -360 degrees Fahrenheit). The average surface temperature on Pluto is 44 Kelvin (-229 Celsius or -380 Fahrenheit).

Back in the days when Pluto was still a planet, it was the coldest planet in the Solar System. But now it’s just a regular temperature dwarf plant – poor Pluto. Neptune is now the coldest planet.

Pluto has the most elliptical orbit of all the planets and dwarf planets. In addition to this widely varying orbital distance, Pluto is also highly inclined, orbiting above and below the planet of the ecliptic that the rest of the planets follow.

You can also look through these books from Amazon.com if you want more information about Pluto.

Pluto Distance from the Sun
Since Pluto orbits the Sun, like the rest of the planets and dwarf planets, astronomers typically measure the distance of Pluto in terms of Astronomical Units (AU). 1 AU measures the distance of the Earth to the Sun.

At its closest point, Pluto is only 29 astronomical units from the Sun (4.4 billion km or 2.75 billion miles). And at its most distant, it can be 49 AU (7.29 billion km, or 4.53 billion miles) from the Sun. In addition to being highly elliptical however, Pluto’s orbit is also inclined at an angle of over 17-degrees. At some points along its orbit, Pluto is above the plane of the ecliptic that the planets follow, and at other times, it’s below.

Pluto’s average distance from the Sun is 40 astronomical units (5.91 billion km or 3.67 billion miles).

Distance From Earth to Pluto
The Earth is only 1 AU from the Sun. When the Earth and Pluto are perfectly lined up with the Sun, their closest point is approximately 28 astronomical units. And at their furthest point, when Earth is on the opposite side of the Sun, Pluto can be 50 astronomical units.