The Orion Nebula is one of the most famous deep-sky objects in the night sky. Being one of the brightest deep sky objects, it can be seen with the naked eye in dark parts of the Earth. Its full beauty is revealed in long exposed photographs. The Orion Nebula is a star birth area. New stars are formed from hydrogen gas, and the newly born stars stimulate the remaining hydrogen gas clouds to emit the typical red light.

This triple star system is located right next to the Flame Nebula (NGC2024). It consists of two close binary components and a third star, Alnitak (ζ Orionis). It is one of the three belt stars in the famous constellation Orion.
 
Alnitak is a rare hot blue-white star, which shines about 10.000 times brighter than our own Sun. Its diameter is about 20 times that of our Sun, which makes it a real giant. Its surface temperature measures at around 25.000 degrees Celsius. This is extremely hot compared to our own Sun which reaches only around 5.500 degrees Celsius.

Antares is on average the fifteenth-brightest star in the night sky, and the brightest object in the constellation of Scorpius. Distinctly reddish when viewed with the naked eye, Antares is a slow irregular variable star that ranges in brightness from apparent magnitude +0.6 to +1.6. Often referred to as "the heart of the scorpion", Antares is flanked by σ Scorpii and Paikauhale (τ Scorpii) near the center of the constellation.
 
Classified as spectral type M1.5Iab-Ib, Antares is a red supergiant, a large evolved massive star and one of the largest stars visible to the naked eye. Its exact size remains uncertain, but if placed at the center of the Solar System, it would reach to somewhere between the orbits of Mars and Jupiter. Its mass is calculated to be around 12 times that of the Sun.

This wonderful spiral galaxy is about twice the size of our own Milky Way Galaxy. It is surrounded by several smaller satellite galaxies, whose gravitational forces may have led to a single, very distinct spiral arm, that is much longer than the other arms. Two supernovae have been observed in NGC 772.

Only 25 lightyears away, Fomalhaut (α Pisces Austrini) belongs to our cosmic neighborhood. It was the first stellar system with an extrasolar planet candidate. Today, it is assumed that no planet was detected, but rather an expanding dusk disk. At an age of 100 to 300 million years, Fomalhaut (α Pisces Austrini) is a rather young star, with a potential life span of a billion years.

Whirlpool Galaxy (M51, NGC5194) is one of the most beautiful spiral galaxies in the night sky. It is interacting with its smaller companion NGC 5195, which is also easily observable in amateur telescopes. Several supernovae have been observed in the Wirlpool Galaxy, which is a great event to help determine the distance of the galaxy. It's diameter is estimated at 76,000 lightyears, which brings it at an overall size of 43% of our own Galaxy.

HR 5171 is a triple star system in the constellation of Centaur. It's distance to Earth is rather uncertain, but it is estimated at 5000 or 12000 light years. With a diameter between 1100 and 1600 times that of the Sun, it is one of the largest known stars, containing either a red supergiant star or a yellow hypergiant star.

NGC 2440 is a planetary nebula which is nice to observe in telescopes. Planetary nebulas are usually only a few hundred or thousand years old. As the gas moves out into space at high velocities, it will at one point become so thin it won't be visible anymore. Eventually, the gas will form new stars and planets.

Zeta Puppis is a blue supergiant star, one of the most luminous stars in our Milky Way Galaxy. It is of spectral type O5, which makes it one of the hottest and most luminous stars in the galaxy.

The Great Carina Nebula is a beautiful deep-sky cloud formation surrounding η Carinae. Next to it is the small but beautiful NGC 3324.

A binary star system, with its companion being ζ² Reticuli. At a distance of slightly less than 40 lightyears, the star pair of ζ Reticuli can even be seen with the naked eye. Both stars of this binary system are yellow dwarf stars, very much like our own Sun.

This carbon star is a luminous red giant. Ordinary stars have more oxygen in their atmosphere than carbon. In contrast, carbon stars have more carbon than oxygen in their atmosphere. Those carbon compounds give the star its strikingly ruby red appearance.
 
It is also a variable star with a pulsation period of around 376 days. The star is shedding its outer atmosphere. It is surrounded by a thin shell of dust and gas that was created during the most recent thermal pulse some 2000 years ago.

This globular cluster in the constellation of Altar contains around 400.000 stars. It is approximately 8,200 lightyears away from earth, which makes it one of the closest globular clusters. It has undergone a core collapse, which means that the center of the cluster has contracted into a very dense stellar agglomeration. White dwarfs, neutron stars, and black holes are likely to be at the center of the cluster.

Among all known stars, Barnard's star is the fourth-nearest star to Earth. With about 14% of our own Sun's mass, it is a red dwarf star. Despite its proximity to Earth, it is too faint to be seen with the naked eye. It is named after E. E. Barnard, an American astronomer who studied it in 1916.

The Monkey Head Nebula is a wonderful hydrogen emission nebula in the constellation Orion. It is quite a huge object, about 75 lightyears in diameter. Photographs reveal glowing areas of bright gas covered by dark dust clouds.
 
Hydrogen emission nebulae are cradles for new stars. Gravity pulls the hydrogen gas closer and closer together until it eventually becomes so dense it can form a new star.

A binary star system at a distance of about 65 light years, Aldebaran is one of the most significant stars in the night sky. It is the main star in the constellation Bull and there marks the eye of the Bull. While the main star of this binary star system is only slightly heavier than our own Sun, its diameter is almost 45 that of our Sun. This makes it about 150 times as bright as our Sun. The companion of this huge main star is a red dwarf.

A famous planetary nebula in the night sky, that is around 10,000 years old. The central star of this nebula blew away its outer hull in an eruption, leading to this wonderful gas cloud formation. It is still lit my its central star, making it so wonderful for us to look at.
 
The nebula was already discovered by William Herschel in 1787, who already described it as a very remarkable phenomenon. Our own Sun will undergo a similar procedure as the central star 1372:1287:1 of this nebula already has and will likely blow out its outer hulls for some other civilizations on distant planets to watch.

Betelgeuse is a red supergiant star, about 800 times the diameter of our own Sun. In the visual range, it is about 10,000 times brighter. Betelgeuse has reached the end of its life span and may explode into a supernova at any time. In fact, it may already have. Since it takes the light of betelgeuse around 550 years to reach our Earth, what we see today is what actually happened 550 years ago.
 
Betelgeuse is one of the main stars in the well-known constellation Orion. It is the upper left shoulder star and can easily be identified due to its red color. It

M15 is one of the most densely packed globular clusters in our Milky Way Galay, containing more than 100.000 stars. Still, it is hard to see with the naked eye, but makes for an excellent object to be viewed with binoculars. It was first discovered by Jean-Dominique Maraldi in the 18th century and subsequently included in his catalogue by Charles Messier. Scientists estimate its age to about 12 billion years, making it one of the oldest globular clusters in our Milkyway.

γ Cassiopeiae is one of the brightest stars in the night sky, and the center star of the W-shape of Cassiopeia. It is also a binary star system and an eruptive variable star, whose brightness varies from 1.6 to 3.0 mag. Its brightness variation is caused by material being lost from the star.
 
Easy to find due to its brightness and its position within the W-shape of Cassiopeia, it has traditionally be used to fine geographic North, as the W of Cassiopeia roughly points to the Polar Star Polaris (α Ursae Minoris).
 
γ Cassiopeiae is located next to the beautiful reflection nebulae IC 59 and IC 63, which can be seen as red clouds on long-exposed astro photos. Being only 3 to 4 lightyears away from γ Cassiopeiae, they are cosmic neighbors.

The Pinwheel Galaxy is a spiral galaxy, just like our own Milky Way Galaxy. However, while our own galaxy hosts "only" around 100 billion stars, the Pinwheel Galaxy is really huge, with an estimated one trillion stars. It is around 50-70% larger in size and sits at distance of around 21 million light years. That means, the light we see today travelled 21 million years through space before reaching us. Looking at the Pinwheel Galaxy is like looking 21 million years into the past.
 
The Pinwheel Galaxy is also known as Messier Object 101 (M101). Charles Messier was a famous astronomer of the 18^th and 19^th century, who compiled a list of 110 well visible deep sky objects - the Messier Catalog. However, it was not discovered by Messier itself, but by Pierre Méchain in 1781.
 
Like our Milky Way Galaxy, the Pinwheel Galaxy has a number of much smaller companion galaxies, such as NGC 5204 or NGC 5474.

Castor can be found high up in the northern hemisphere. Together with his twin half-brother Castor B (α Geminorum) from the Greek and Roman mythology, Castor and Pollux are the main stars of the constellation Twins, marking the heads of the two twins.
 
Long known as a double star system, well visible in telescopes, Castor is in fact a system comprising six stars. All six stars are bound together by their gravity, where the two main components Castor A (α Geminorum) and Castor B (α Geminorum) revolve around each other in 420 years. Such complex multi star systems are very rare, which makes Castor truly amazing.

This wonderful planetary nebula was discovered by William Herschel already in 1786. It consists of the remnants of an old star that blew its gas out into deep space. The gas will wander through our galaxy and eventually become part of new stars and planets. Planetary nebulas are usually not very old, and the age of the Cat's Eye Nebula is estimated at around 1000 years, not very old on a cosmic scale.

Polaris, also known as the Pole Star or North Star, is the main star in the constellation Little Bear. It is very close to the northern celestial pole, hence its name. Visually, Polaris is a double star, with the much fainter companion being visible only in telescopes. It was discovered in 1780 by William Herschel, a British-German astronomer, musician, and composer. The main star is a double star itself, but it took until the year 2006 when it could be resolved into two components using the Hubble Space Telescope.
 
Polaris is one of the most important stars in the night sky, at least on the northern half of our planet, since Polaris makes it easy to determine North and the latitude of one's position on Earth. For centuries sailors have relied on Polaris to determine their position on the ocean. Only since the introduction of GPS this has become less important, but it is still a popular exercise for people who want to get along without electrical aides.