Messenger Enters Mercury’s Orbit

On Thursday, March 18^th the Messenger unmanned spacecraft entered Mercury’s orbit.  The last time a spacecraft sent to Mercury was Mariner 10 in 1974 and at that time Mariner 10 was only able to photograph 75% of Mercury’s surface.  Messenger will orbit Mercury for one year and will map the entire surface including color photographs.  On April 4^th, the science portion of the mission will begin as NASA scientists and engineers will begin getting data to interpret from Mercury’s surface.  Over the next few months we should be getting some never before seen images of Mercury.  NASA has a website dedicated Messenger webpage with updates on the mission and photographs.

Weather on Mercury today: very hot (again)

Mercury is a strange, small planet.  Mercury is a bit smaller than Earth’s moon.  Mercury takes 88 Earth days to circle the sun – this is the length of its year.  Oddly, one day on Mercury is equal to 59 days on Earth.  It takes Mercury 1,407 hours to rotate 360^o.  Mercury does not have an atmosphere to retain heat so its temperatures range from 800 ^oF in the day to -279 ^oF at night.  Mercury is a dense planet and its core is 65% iron in a form that is not normally seen on Earth.  This composition is unexpected in such a small planet.  Some scientists theorize that Mercury could have been a larger planet at one time and some sort of massive collision caused it to lose its outer layers.  The elemental composition of Mercury is one of the topics that is being studied in the Messenger mission.  You can learn more about Mercury on NASA’s Mercury page.

Look, it’s the Empire’s Death Star!

Click here to see a photograph of the Empire’s Death Star.  No… wait…  it’s actually Mimas, a moon of Saturn.  Mimas has a large crater named Herschel which makes it look like the Death Star in the Empire Strikes Back.

Mimas was discovered in 1789 by William Herschel.  It is the moon closest to Saturn and the eighth moon orbiting Saturn.  It is quite small at only 250 miles in diameter (approximately the distance from New York City to the suburbs of Washington DC).  The surface of Mimas is dominated by the crater Herschel which was probably created by a large asteroid hitting the moon.  The entire surface of Mimas appears to be covered by smaller craters. 

William Herschel’s son suggested that the moon keep in the tradition of naming celestial objects after Greek Mythological figures.  Herschel named this moon Mimas after the son of Gaia.  Mimas and his brothers were Gigantes, serpent-footed giants.  Ares, the Greek God of War, killed Mimas killed in battle. 

William Herschel built his own telescopes, the most powerful at that time.  In 1781, he had another very important find, Uranus, the first planet identified with a telescope and the first discovered since ancient times. 

Jupiter has how many moons?!?

Jupiter has 63 moons!  Some are very small and others are larger than Pluto.  The four largest moons are called the Galilean moons because they were discovered by Galileo Galilei in the year 1610.  Ganymede is the largest moon and it is bigger than Mercury.  It is the ninth largest object in our solar system.  The other three Galilean moons are Io, Europa, and Callisto and all are larger than Pluto.  The 59 smaller moons tend to be less than 160 miles in diameter.  Some of these smaller moons have irregular (non-spherical) shapes and astronomers theorize that they have originated from passing asteroids that were pulled into Jupiter’s’ orbit by gravity. 

In February 2007, NASA’s New Horizons spacecraft flew near Jupiter and took pictures of Ganymede, Io, Europa and Callisto.    Click here to see those pictures.

Why isn't Pluto a planet anymore?

When I was a kid, Pluto was a planet, the smallest planet in our solar system.  But in 2006, the International Astronomical Union (IAU) determined that Pluto is not really a planet, but a dwarf planet.  A dwarf planet is a celestial body that 1) is in orbit around the sun, 2) keeps a nearly round shape, 3) hasn’t cleared the neighborhood around its orbit and 4) is not a satellite.  Pluto was determined to be a dwarf planet because it “hasn’t cleared the neighborhood” around its orbit meaning that there are other celestial objects in its orbital path around the sun. 

Pluto is actually part of the Kuiper Belt.  The Kuiper Belt is in the solar system extending beyond Neptune and it is made up of frozen objects made up of methane, ammonia and water.  Pluto is the largest dwarf planet in the Kuiper Belt.  The two other dwarf planets in the Kuiper Belt are Haumea and Makemake.

NASA has sent a spacecraft to visit Pluto and the Kuiper Belt called New Horizons.  New Horizons left Earth in January 2006 and is not expected to reach Pluto until 2015.

Click here to see NASA’s homepage for Pluto.

The Sun in 3D (no glasses needed)

This week NASA released the first pictures of our sun in 3D.  Back in 2006, NASA sent into space two probes called STEREO probes and now those satellites are in place orbiting the sun and sending images back to Earth in Stereo.  Click here to see a link of the Sun in 3D.

The STEREO probes (called A and B) are located 180 degrees apart on essentially on either sides of the sun.  With the 3D view o the sun, scientists can better monitor solar flares and predict the path -of solar storms.  For example, in August 2010, scientists observed a massive solar storm – link here to see the solar storm.  If the STEREO mission had been in place at that time, scientists could have better observed the path of the storm around the sun.

Do you know what planet in our solar system is not named after an ancient Greek or Roman god?

Earth!

Mercury is the Greek god that is the messenger of Zeus.  The god Mercury is often shown with wings on his shoes so he can fly fast.  If you saw the movie Percy Jackson & the Olympians: The Lightening Thief, Percy used a pair of Mercury’s hightops with wings to fly.

Venus is the Roman goddess of beauty.  Venus is easy planet to see in the sky - it is very bright.

Mars is the Roman god of war.  

Jupiter is the Roman name for the Greek god Zeus.  Zeus was the king of all the Greek gods.  The biggest planet in our solar system is named after the most powerful god.

Saturn is the Roman god of time.

Uranus is the grandfather of Zeus (Jupiter).

Neptune is a Roman god also know as Poseidon, the god of the sea.  Neptune is blue, - it looks like the water on earth.

Pluto (which is no longer a planet, but a dwarf planet) is a god also known as Hades, the king of the underworld.

Space.com is a great website to learn generally about space.  Another fun site specifically for kids is KidsCosmos.com.