In these articles, you discover a little about the amazing range of beautiful objects you can see in the night sky, from the Moon and planets to star clusters, nebulae, and galaxies. This knowledge will be a huge help with your stargazing sessions. Because understanding the celestial objects you see in your binoculars or telescope is sometimes as much fun as seeing them.
The Moon
Aside from the Sun, the Moon is the brightest and most recognizable object in the sky. The Moon has no air or water so its surface has been nearly unchanged from the earliest days of the solar system some 4 billion years ago. Many skilled stargazers have examined the surface of the Moon in detail for decades and still never tire of its stark beauty, and professional and amateur astronomers continue to study the history of our solar system as written into its rocky face.
At about 1/4 the diameter of the Earth and some 250,000 miles away, the Moon spans just a tiny slice of sky, about half the width of your little finger held at arm’s length. Even with your unaided eye, you can see light and dark areas on the Moon. The light-colored areas are the lunar highlands, the oldest parts of the Moon’s surface. The highlands are peppered with craters made mostly by stray asteroids and comets left over from the solar system’s formation about 4 billion years ago.
The craters Copernicus and Tycho, and the Seas of Serenity and Tranquillity, just a few of the hundreds of features visible on the surface of the Moon
The Moon cycles through phases once every 27 days or so. As it waxes from its “new” phase to full, it’s visible in the evening or night sky; as it wanes back to new, it’s mostly visible in the daytime.
The darker patches on the Moon are newer, about 3 billion years old. They are called the lunar maria (“MAH-ree-ah”) or seas, a misnomer since they are bone-dry and covered with fine dust. The maria were flooded with lava after the solar system had been mostly cleared out of stray material that smashed into the Moon’s surface. That’s why these younger regions are smoother and have far fewer impact craters.
The crescent Moon as it appears in binoculars. The dark areas are the “maria” or seas; the cratered lighter areas are the lunar highlands.
The seas of the Moon come into clear view with a pair of binoculars. So do about a dozen large craters. When the Moon is nearly full, you can see near the south-central part of the Moon (“south” is “down” for observers in the northern hemisphere) the crater Tycho, which has a series of “rays” that shoot out in all directions, giving the Moon the appearance of a peeled orange, with Tycho as the “pip”. The rays are material ejected when Tycho was created by a large asteroid impact about 110 million years ago.
When the Moon is about a day or two past “first quarter” (when it appears half lit), another large crater comes into view near the equator of the Moon. This is the crater Copernicus, a large crater nearly 100 km across.
While binoculars show dozens of sights on the Moon, a small telescope reveals thousands, including craters of all shapes and sizes, arcing mountain ranges that tower thousands of feet above the lunar surface, and cracks and fault lines and strange domes that hint at past geological activity.
Beginners often believe the best time to observe the Moon is when it’s full. But that’s almost always the worst time. You’ll get the best views of the Moon along the terminator, the line that separates night from day. On the terminator, the craters and mountains stand out more clearly in the long shadows of lunar sunset or sunrise.
Seeing the Planets
Venus and the Moon
There are eight major planets in our solar system including Earth; Pluto was demoted to the status of a “dwarf planet” in 2008. The planets are fascinating sights for stargazers. With no optics, you can watch the five bright planets Mercury, Venus, Mars, Jupiter, and Saturn move slowly with respect to the background stars from day to day and week to week. The apparent motion of the planets is caused by their revolution around the Sun, as well as the motion of the Earth with respect to the planets.
The two planets closer to the Sun than Earth, Mercury and Venus, appear bright and fast moving in the sky. When they are visible, they always lie not far from the Sun before sunrise or after sunset. The outer planets have a little more freedom to move around the sky. They can be found anywhere on a narrow band around the sky called the ecliptic which passes through the twelve constellations of the zodiac. All eight major planets always appear in or very near these constellations.
Saturn as it appears in a small telescope
With your unaided eye, you can see Mercury, Venus, Mars, Jupiter, and Saturn. If you know just where to look, you might see Uranus too. Binoculars are not powerful enough to reveal much detail on the face of any planet, though they will reveal the four largest moons of Jupiter that move like clockwork around the planet from hour to hour and night to night (see image below). Saturn’s largest moon, Titan, is also visible in binoculars and any telescope. But to see any detail of the face of the planets, or to see the phases of Mercury and Venus, you will need a telescope.
To an observer with a small telescope, Mars, Jupiter, and Saturn reveal an astonishing array of detail on their disks. On Mars, you can see the white polar caps, darker and lighter orange-red rocky and sandy regions, and even the hint of clouds sometimes. Jupiter and Saturn in a telescope show bands of icy clouds on their faces and occasional oval “spots” which are local storms larger than the Earth. Saturn has a stunning system of rings which can be seen even in a small telescope. These rings are barely more than 10 meters thick and are made of small icy particles. Uranus and Neptune can be resolved into featureless white disks without detail; it’s an accomplishment for a beginner to see these distant and icy giants at all. Pluto is too faint to see in all but the largest backyard telescopes.
Jupiter and its 4 largest moons in binoculars
Usually at least one bright planet is visible in the night sky, and sometimes two or three are visible at sometime during the night.
Meteors and Meteor Showers
When the Earth runs into a meteoroid, it falls through the atmosphere where it grows hot and burns up in a few seconds, igniting a sudden trail of light across the sky. Such burning bits of rock and ice are called meteors. Look up on any night and you might see 3 or 4 meteors each hour shoot randomly across the sky.
Most meteors burn up before they hit the ground. The fainter meteors are the size of sand grains. Brighter ones range from the size of a pea to a golf ball, and very bright meteors might be the size of a softball. Very rarely, large meteors, perhaps the size of a basketball or a little larger, and especially if they are made of iron and nickel, will burn through the atmosphere and hit the ground, or explode before they hit the ground. When it hits the ground, it’s called a meteorite.
Meteors from the Perseid meteor shower
Sometimes, on fixed dates throughout the year, the Earth passes through the path of a comet which has left behind small clouds of icy pellet-sized debris as it orbits the Sun. When this happens we’re treated to a meteor shower during which you may see dozens or even hundreds of meteors each hour. Perhaps the finest meteor shower each year occurs around August 12 when the Earth passes through the path of Comet Swift-Tuttle. This shower is called the Perseids, since the trails of meteors all trace their paths back to a point in the constellation Perseus (see image above).
There are dozens of conspicuous meteor showers during the year. Some of the best are listed below along with dates when the most meteors are visible. The name of each shower refers to the constellation back to which the meteors trace their apparent paths. You don’t need to see each constellation to see the meteors. They can appear anywhere in the sky.
- Lyrids, April 21-22
- Perseids, August 11-12
- Orionids, October 21-22
- Leonids, November 16-17
- Geminids, December 13-14
Watching a meteor shower is one of life’s under-appreciated pleasures. You don’t need binoculars or a telescope. You just need to lay back and look up at the sky. Depending on the shower and on the time of night, you might see a meteor every 5 or 10 minutes. Or you might see one or more meteors every minute. You will see more in dark sky away from the light-pollution of the city, and look in the part of the sky away from a bright Moon if it’s out. Because the Earth usually turns into streams of meteors after midnight, the most meteor showers show more action between midnight and dawn.
Comets: Visitors from the Outer Solar System
Comets are small, dark, icy bodies that are likely remnants of the formation of the solar system. Most comets lie far from the Sun, frozen and dark in a halo of trillions of comets far past the orbit of Neptune. Sometimes a comet is sent plunging towards the inner solar system by a little gravitational push from another comet or a passing dust cloud. As the comet nears the Sun, it heats up and forms a halo of gaseous material called a coma, and in some cases, a tail which is pushed away from the Sun by the solar wind, a stream of charged particles ejected from the Sun. The central massive part of a comet is called the nucleus. It’s usually just a few kilometers across. It consists of a mixture of icy material such as ammonia, water, carbon dioxide, and methane, along with traces of rock, dust, and carbon-based debris left over from the formation of the solar system. Comets are often described, more or less accurately, as dirty snowballs.
The dusty tail of Comet McNaught in 2007 (credit: ESO)
As seen from Earth, comets are far less common than meteors. There might be a half-dozen comets visible each year, though they are usually faint enough to require a telescope to see well. Every 10 years, on average, a comet grows bright enough to become easily visible with the naked eye. Comet Hale-Bopp in 1997, and Comet McNaught in 2007 were examples.