Amazing Moons

When the Space Age began, explorers were eager to visit the planets of the solar system. As the years have passed, however, astronomers have realized that the moons of the solar system may be even more interesting.
Moons - also called natural satellites - come in many shapes, sizes and types. They are generally solid bodies, and few have atmospheres. Most planetary moons probably formed from the discs of gas and dust circulating around planets in the early solar system.

There are hundreds of moons in our solar system - even a few asteroids have been found to have small companion moons. Moons that begin with a letter and a year are considered provisional moons. They will be given a proper name when their discoveries are confirmed by additional observations.

Of the terrestrial (rocky) planets of the inner solar system, neither Mercury nor Venus have any moons at all, Earth has one and Mars has its two small moons. In the outer solar system, the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune have dozens of moons. As these planets grew in the early solar system, they were able to capture smaller objects with their large gravitational fields

How Moons Get Their Names

Most moons in our solar system are named for mythological characters from a wide variety of cultures. The newest moons discovered at Saturn, for example, are named for Norse gods such as Bergelmir, a giant.

Uranus is the exception. Uranus' moons are named for characters in William Shakespeare's plays so you'll find Ophelia and Puck in orbit. Other Uranian moon names were chosen from Alexander Pope's poetry (Belinda and Ariel).

Moons are given provisional designations such as S/2009 S1, the first satellite discovered at Saturn in 2009. The International Astronomical Union approves an official name when the discovery is confirmed.

Moons of the Inner Solar System

Earth's Moon probably formed when a large body about the size of Mars collided with Earth, ejecting a lot of material from our planet into orbit. Debris from the early Earth and the impacting body accumulated to form the Moon approximately 4.5 billion years ago (the age of the oldest collected lunar rocks). Twelve American astronauts landed on the Moon during NASA's Apollo program from 1969 to 1972, studying the Moon and bringing back rock samples.

Usually the term moon brings to mind a spherical object, like Earth's Moon. The two moons of Mars, Phobos and Deimos, are different. While both have nearly circular orbits and travel close to the plane of the planet's equator, they are lumpy and dark. Phobos is slowly drawing closer to Mars and could crash into the planet in 40 or 50 million years. Or the planet's gravity might break Phobos apart, creating a thin ring around Mars.

Moons of the Giant Planets

Jupiter's menagerie of moons includes the largest in the solar system (Ganymede), an ocean moon (Europa) and a volcanic moon (Io). Many of Jupiter's outer moons have highly elliptical orbits and orbit backwards (opposite to the spin of the planet). Saturn, Uranus and Neptune also have some irregular moons, which orbit far from their respective planets.

Saturn has two ocean moons-Enceladus and Titan. Both have subsurface oceans and Titan also has surface seas of lakes of ethane and methane. The chunks of ice and rock in Saturn's rings (and the particles in the rings of the other outer planets) are not considered moons, yet embedded in Saturn's rings are distinct moons or moonlets. These shepherd moons help keep the rings in line. Titan, the second largest in the solar system, is the only moon with a thick atmosphere.

In the realm of the ice giants, Uranus's inner moons appear to be about half water ice and half rock. Miranda is the most unusual; its chopped-up appearance shows the scars of impacts of large rocky bodies.

Neptune's moon Triton is as big as Pluto and orbits backwards compared with Neptune's direction of rotation.

Moons of Dwarf Planets

Pluto's large moon Charon is about half the size of Pluto. Like Earth's Moon, Charon may have formed from debris resulting from an early collision of an impactor with Pluto. Scientists using the Hubble Space Telescope to study Pluto found four more small moons.

Eris, another dwarf planet even more distant than Pluto, has a small moon of its own, named Dysnomia. Haumea, another dwarf planet, has two satellites, Hi'iaka and Namaka. Ceres, the closest dwarf planet to the Sun, has no moons.

More Moons

Scientists weren't sure if asteroids could hold moons in their orbits until the Galileo spacecraft flew past asteroid Ida in 1993. Images revealed a tiny moon, later named Dactyl.

Enjoying The Geminids From Above And Below

The Geminids meteor shower will be viewed from above by the Meteor camera on the International Space Station, as well as from below by sky watchers on Earth


On the night of December 13, into the morning of December 14, 2018, tune into the night sky for a dazzling display of fireballs. Thanks to the International Space Station, this sky show - the Geminids meteor shower -- will be viewed from both above and below

Sky watchers on the Earth will be sprawled flat on their backs, scanning the skies for fleeting streaks of light or meteors from small particles or meteoroids burning up as they plunge into the atmosphere. While most of those viewers won't be pondering what the shooting stars are made of, astronomers and planetary scientists will be. The Meteor camera on the space station will provide clues.

Meteor records HD video from inside the Window Observational Research Facility (WORF) - looking through thehighest optical-quality window ever installed on a human space vehicle.

This camera helps scientists identify and monitor the activity of meteors, from bolides, extremely bright meteors that typically explode in the atmosphere, to much fainter ones not visible to the naked eye. The camera is equipped with a diffraction grating, an optical component that allows incoming light to be split into selected visible wavelengths of light that are signatures of various elements (Iron, Sodium, Calcium, and Magnesium). By measuring a spectrum or chemical fingerprint from the meteor, the presence of these elements is revealed.

Meteor Science Principal Investigator Tomoko Arai of the Chiba Institute of Technology in Japan says, Our observations focus on annual meteor showers, such as Geminids and Perseids, because their meteoroids originated from known comets or asteroids, so-called meteor showers' parent bodies. The spectral information will tell us the chemical makeup of meteoroids and of their parent bodies. This can help us understand their origin and evolution.

The instrument also helps improve estimates of how much material actually enters Earth's atmosphere. Findings could help mission planners protect spacecraft and Earth from potential collisions with meteoroids.

So what parent body spawns the debris that results in the dazzling Geminids?

Many researchers hypothesize that they are related to a rocky asteroid known as 3200 Phaethon, which passes closer to the sun than any other named asteroid.Phaethon may be a rock-comet-a dormant comet that has accumulated a thick mantle of interplanetary dust grains that can slough off as the comet nears the sun. Phaethon may be an asteroid that was once rich in ice and organics like comets, originally located in the main asteroid belt, which has become active as its orbit has evolved closer to the Sun.

Another possible explanation for the Geminids source is as follows:

There is another object - Apollo asteroid 2005 UD - that seems to be dynamically related to Phaethon and has physical similarities.Some researchers believe that 2005 UD, 3200 Phaethon, and the massive amounts of debris that cause the Geminids are all products of a larger object that has broken apart.

Researchers continue to debate the cosmic drama underlying the Geminids.

Best viewing is Friday morning around 2 AM your local time, after moonset. In the suburbs you could see around 40-50 meteors per hour. Under ideal conditions you could see about 100 meteors per hour! Darker is always better when viewing meteor showers.

The Period Of The Solar Minimum

Intense solar activity such as sunspots and solar flares subsides during solar minimum, but that doesn't mean the sun becomes dull. Solar activity simply changes form
High up in the clear blue noontime sky, the sun appears to be much the same day-in, day-out, year after year.

But astronomers have long known that this is not true. The sun does change. Properly-filtered telescopes reveal a fiery disk often speckled with dark sunspots. Sunspots are strongly magnetized, and they crackle with solar flares-magnetic explosions that illuminate Earth with flashes of X-rays and extreme ultraviolet radiation. The sun is a seething mass of activity.

Until it's not. Every 11 years or so, sunspots fade away, bringing a period of relative calm.

This is called solar minimum and it's a regular part of the sunspot cycle.

The sun is heading toward solar minimum now. Sunspot counts were relatively high in 2014, and now they are sliding toward a low point expected in 2019-2020.

While intense activity such as sunspots and solar flares subside during solar minimum, that doesn't mean the sun becomes dull. Solar activity simply changes form.

For instance, during solar minimum we can see the development of long-lived coronal holes.

Coronal holes are vast regions in the sun's atmosphere where the sun's magnetic field opens up and allows streams of solar particles to escape the sun as the fast solar wind.

We see these holes throughout the solar cycle, but during solar minimum, they can last for a long time - six months or more. Streams of solar wind flowing from coronal holes can cause space weather effects near Earth when they hit Earth's magnetic field. These effects can include temporary disturbances of the Earth's magnetosphere, called geomagnetic storms, auroras, and disruptions to communications and navigation systems.

During solar minimum, the effects of Earth's upper atmosphere on satellites in low Earth orbit changes too.

Normally Earth's upper atmosphere is heated and puffed up by ultraviolet radiation from the sun. Satellites in low Earth orbit experience friction as they skim through the outskirts of our atmosphere. This friction creates drag, causing satellites to lose speed over time and eventually fall back to Earth. Drag is a good thing, for space junk; natural and man-made particles floating in orbit around Earth. Drag helps keep low Earth orbit clear of debris.

But during solar minimum, this natural heating mechanism subsides. Earth's upper atmosphere cools and, to some degree, can collapse. Without a normal amount of drag, space junk tends to hang around.

There are unique space weather effects that get stronger during solar minimum. For example, the number of galactic cosmic rays that reach Earth's upper atmosphere increases during solar minimum. Galactic cosmic rays are high energy particles accelerated toward the solar system by distant supernova explosions and other violent events in the galaxy.

During solar minimum, the sun's magnetic field weakens and provides less shielding from these cosmic rays. This can pose an increased threat to astronauts traveling through space.

Solar minimum brings about many changes to our sun, but less solar activity doesn't make the sun and our space environment any less interesting.

For more news about the changes ahead, stay tuned

Elucidating The Black Holes

"Black holes" is one of the most highly searched terms about our universe. There's a fascination with the idea of a region of space having a gravitational pull so strong, nothing can escape its deadly grasp, not even a sliver of light. Well, not quite. In fact, much of what we think we know about black holes turn out to be myths.

Myth 1 - All black holes are black. As the photograph below from the Event Horizon telescope demonstrated, light can be detected near a black hole's event horizon. This is the boundary between normal space and the space affected by the black hole's gravity, from which no escape is possible. Part of this light comes from the black hole's accretion disk, a flat, pancake like structure composed of dust, gas and other debris. Friction constantly moves the disk's material inward toward the event horizon. Light also comes from jet streams which propel matter outward along the disk's north and south poles.

Myth 2: All black holes are about the same size. Black holes actually come in several different sizes which are defined by their mass. Small black holes are usually the result of a relatively short and violent collapse of a star. Recent work suggests that Intermediate black holes are found in the nuclei of some active galaxies. Super massive black holes on the other hand, are found at the center of nearly every galaxy.

Dr. Dan Evans, an Astrophysicist at NASA Headquarters says, "There's a direct relationship between the beginning of super massive black holes and the beginning of their corresponding galaxy. This strongly suggests the two were born about the same time and slowly grew in size together over billions of years."

Myth 3: If you get within a few thousand miles of a black hole, its super gravity will pull you into its center. It turns out you can get surprisingly close to a black hole. If you approached a black hole with mass equal to our Sun's for example, you could get as close as tens of miles. So imagine if we replaced our sun with a black hole of the same mass. All of the planets would continue to revolve around it, at exactly the same speed and distance as they do now.

Myth 4: Once inside a black hole, nothing ever comes out. Nope. It turns out that radiation can escape from a black hole. One of Stephen Hawking's contributions was a theory that a black hole is not so dense in a quantum mechanical sense. The slow leak of what's now known as Hawking radiation would, over time, cause the black hole to simply evaporate.

The image from the Event Horizon telescope confirmed what Albert Einstein's general theory of relativity predicted over 100 years ago - that a black hole's form is that of a perfect circle. And as scientists learn even more about the properties of this gigantic cosmic mystery we call a black hole, they'll be able to puncture even more myths.