Rum ble fische

Introduction to astronomical drawing

You are enough people that when seeing one of the drawings that in these pages are exposed you are interested in how they have been made, and you even consider trying it. I will start here what I intend to be a series of articles in which I will explain how I make my astronomical drawings, and offer some advice for those who encourage you to try.

Go ahead that the drawing and its techniques are something totally personal, that each one is developing according to their preferences with time and practice. There are other ways to do it, and of course you are all invited to expose and comment on these pages.

The drawings on these pages are made in negative , black on white, and then scanned, labeled and inverted for publication. Drawing in negative has several advantages: it looks better in the dark, the pencils are more precise and versatile, it is easier to correct, and it is much cheaper.

It’s just that I do not draw …

It is the phrase that I can hear most times when I encourage people to do it. Let’s not kid ourselves, nobody knows how to draw at the beginning. The keyword is practical , if you do not try, it sure does not come out.

Luckily, astronomical drawing does not require great means or complex techniques, nor great manual skill: almost everything that is seen by the eyepiece are dots and objects without much detail. We will talk about the Moon and the planets much later.

The main objective of amateur astronomical drawing is to support astronomical observation. They are natural notes, made with very simple techniques, and in short times.

To make learning easier, you can start by drawing naked eye constellations or asterisms. This avoids having to fight with the telescope in addition to the paper.

Basic tools

To start, you need some very simple tools: paper, pencil, red light, and a diffuser (optional).

The paper can be at first any, although I would recommend a white pad of acid-free paper, which is something consistent to resist moisture, and have some grain, but little. The size, according to the tastes; mine are A5, type field notebook .

The pencil , of ordinary graphite, can be of different hardnesses. Everyone has their preferences about it. I recommend having at least three pencils, one fairly soft (4B), one medium (B) and one somewhat hard (HB to 2H), although you might be more comfortable with something harder: do tests.

The pencils have to be sharpened. A pencil sharpener does not always offer the right sharpening we need, and a blade can be dangerous to handle in the dark. That’s why I use mechanical pencils, with a standard 2mm blade, and I sharpen them with a sharpener, with a metal body better than plastic, or with a scraper . Fine mechanical pencils, of 0.5 mm mines and the like, are not practical for these uses.

The scraper is a tablet with a block of sandpaper stapled into it, and a sponge to clean the graphite powder from the tip of the pencil. It also serves to sharpen and clean the blurs. It allows to leave the tip of the mine more or less blunt, according to the need of the moment.

The red light flashlight is very important. It serves to see in the dark without harming the adaptation of our eyes to night vision. The view takes a half hour to adapt to optimal performance in the dark. However, in tenths of a second exposed to a bright light this adaptation is lost and you have to wait another half hour to recover it. The red light however does not harm this process; The rods, which are responsible for vision in low light conditions, are insensitive to the lights of these wave frequencies.

The light must be really red. If you are going to use a normal flashlight, you will have to put several layers of red acetate or similar until you get a totally red light and no cracks. However, today they are very common those that use LEDs instead of incandescent bulbs. In these, it is usually easy to replace the white LEDs with other bright red ones (the normal red ones are too dim). If you do not drive with the welder, surely you know someone who can do it.

Normally the light of the lanterns is very concentrated in certain points, creating areas brighter than others, or fences and halos. This can be very annoying to draw, and yet it is very easy to solve: just place a paper screen or Scotch Magic 3M adhesive tape.

If you are going to draw diffuse objects, you will need a medium thickness blur , although there are those who work with your finger. I do not recommend it for the simple reason that a dirty finger is unwise when handling eyepieces, filters, etc. The blur should be good, bought in a specialized stationery, better than in a school. Even so, as it comes from the factory, any blur is too rigid: you have to give it good hammering, placing it on a hard surface, until it is soft and flexible. Then you can sharpen or clean with the scraper.

As you can see, I have not spoken of deleting. Erase is not a simple matter and I will discuss it later in depth. For now, if you make a mistake, mark the error with a cross and keep drawing.

First exercises

First, you should familiarize yourself with the material before going out to the field to draw.

To test the reaction of our pencils with the chosen paper, you have to make some test stars. Make several series of stars of different caliber, experiment with the different mine hardnesses, and with the tip more or less blunt.

To prevent stars from sticking out , you have to hold the pencil in a different way than usual. You have to keep it totally vertical, support it on the page and lift it. To give a little intensity to the star, turn the pencil a little; more spin, thicker. It is a mistake to tighten more to get more intensity. In the photo you can see how to pick up the pencil that I prefer.

It is also convenient to blur some paper with the difumino, to test how it reacts. For this, you start staining with the softest pencil in the margin of the sheet. Then the “fuzz” is “loaded” by rubbing it and turning on that spot. Also in the margin, they make strokes with the blur until they are very faint, and then it is applied in the area of ​​the drawing to be made. Soft circular strokes should be made, with very little pressure. Make tests with the more or less loaded diffuser and with different pressures.

To draw with the difumino one acts by applying very soft layers, one over another, until achieving the level of “brightness” (in our case darkness) desired. It is very common for things to remain larger than they are when drawing with the blur; the drawing tends to extend. As always, only practice solves this problem. If we have gone off tone, it can be clarified using the clean tip of the diffuser.

So far we have drawn in the comfort of a well-lit table. When you draw in the field with red light and weak, the thing changes. It is normal, in addition to tending to make things bigger than they are, to make a stronger mark with the pencil or with the blur of what is really necessary. You have to learn to control yourself, a strong brand is impossible to erase.

I said it at the beginning and here I repeat it, practice , blur many sheets, it is the only way.

Can it happen that someday our galaxy, the Milky Way , collides with its biggest neighbor, the Andromeda galaxy ?

Most likely, yes.

The meticulous study of the slight displacements of the stars of M31 in relation to the background galaxies in the last images of the Hubble Space Telescope indicates that the center of M31 could be in a direct trajectory of collision with the center of our home galaxy.

However, the errors in the lateral velocity seem to be large enough to admit a good chance that the central parts of the two galaxies will not collide completely, but they will get close enough that their outer halos will end up gravitationally entangled.

Once this happens the two galaxies will connect, dance around, and eventually merge to become a large elliptical galaxy , over the next billion years.

The image of today is an artistic illustration of the sky of a world in the distant future, when the central parts of each galaxy begin to destroy each other.

The exact future of our Milky Way and the entire Local Group of surrounding galaxies will probably remain an active research topic for many years to come.

Click here to see today’s image in higher resolution.
Credit for illustration: NASA , ESA , Z. Levay and R. van der Marel ( STScI ), and A. Mellinger.

This series of illustrations shows the planned fusion between our galaxy, the Milky Way and the neighboring Andromeda galaxy.

• First row, left: Today.
• First row, right: In 2 billion years the disc of the Andromeda galaxy approaching is noticeably larger.
• Second row, left: In 3.75 billion years, Andromeda fills the field of vision.
• Second row, right: In 3.85 billion years, the sky is burning with the formation of new stars.
• Third row, left: In 3.9 billion years, the formation of stars continues.
• In the third row, right: In 4 billion years, Andromeda stretches due to the tides and the Milky Way is deformed.
• Fourth row, left: In 5.1 billion years the nuclei of the Milky Way and Andromeda appear as a pair of bright lobes.
• Fourth row, right: In 7 billion years the fused galaxies will form an immense elliptical galaxy, its bright core will dominate the night sky.

Computer simulation of the foreseeable collision

This scientific visualization of a computer simulation shows the inevitable collision between our galaxy, the Milky Way and the Andromeda galaxy (also known as Messier 31).

Measuring the lateral movement of Andromeda

This video focuses on a region in the halo of the neighboring Andromeda galaxy that astronomers studied with the Hubble Space Telescope to make accurate measurements of the movement of the galaxy. It was previously known that Andromeda is approaching the Milky Way, but these new measurements of lateral (or sideways) movement of Andromeda can be used to predict that the galaxy is destined for a frontal collision with our Milky Way. Images from the same halo field captured at seven-year intervals were used to accurately measure the small amount of movement relative to the background galaxies. When this change is projected over the next 32,000 years, the movement in the sky becomes evident.

3 June 2012

The extraordinary transit of Venus by the face of the Sun in 2004 was one of the most photographed events in the history of heaven.

Both scientific and artistic images came to us in large numbers from areas that could see traffic : Europe and much of Asia, Africa and North America.

Scientifically, the solar photographers confirmed that the effect of the black drop is more related to the clarity of vision of the camera or telescope than to the atmosphere of Venus.

Artistically, the images can be divided into several categories.

A guy captures the transit in front of a very detailed Sun.

Another category captures a double coincidence, such as Venus and a plane silhouetted at the same time, or Venus with the International Space Station in low Earth orbit.

A third type of image consists of a fortuitous distribution of some clouds with an interesting aspect, as shown for example in today’s image, taken from North Carolina, USA.

Sky enthusiasts around the world are excited by the transit of Venus that will take place on Tuesday.

It may be interesting to ask if a person will live to see, and remember to have seen, both the transit of Venus on Tuesday and the next in 2117.

The area of ​​visibility of the transit of Venus

Check in the image the visibility zone of the transit of Venus or in this other at a higher resolution .

The lucky ones who will be able to contemplate the transit of Venus are still in time to prepare a solar funnel to be able to observe it safely.

In case you can not see it live and live, you have available this website where they will broadcast it in Spanish .

The Venus project: The story of an exciting journey to the transit of Venus in the eighteenth century

The Venus project was an 18th century project in which several European countries (mainly England and France) collaborated with the aim of scrutinizing the last transit of Venus that has taken place.

This project has had enormous repercussions in the contemporary science, because it allowed to calculate the absolute distances between the stars of the solar system; in 1835 the director of the observatory of Berlin Johann Franz Encke obtained, from the data obtained in the transits of 1761 and 1769, a value of the solar parallax of 8.57 seconds of arc, the astronomical unit , which corresponded to a distance Tierra-Sol of 153,500,000 km.

It was an international event for which they had to travel vast distances (to about 70 improvised observatories) so that observation from several points allowed the necessary calculation.

The video that we present to you is a chapter of the documentary project “History of Humanity”, the chapter “Science and illustration: the transit of Venus.”

A few years ago, a more perfect method than parallax was discovered to measure the distances of celestial bodies.

It consists of emitting microwaves to space. Microwaves are very short radio waves, like those used in radar. When the waves reach a celestial body, they bounce off it and are picked up and detected on Earth again. The speed at which the microwaves move is known; The time between the emission and reception can also be measured with great precision. Therefore, this technique allows to know, with greater precision than the parallax method, the round trip distance traveled by the microwaves and, therefore, the distance of a celestial body.

There are four ways to express distances, all of them very interesting to know.

They can be expressed in millions of miles. This unit is very common in Great Britain and the United States to measure great distances.

They can also be expressed in millions of kilometers. The kilometer is the unit that is normally used in civilized countries, except for the Anglo-Saxons, to measure great distances. It is also used by scientists from all over the world, including the United States and Great Britain. One kilometer is 1093.6 yards or 0.62137 miles. We can also say that a kilometer is 5/8 of a mile.

If we want to avoid millions of miles or kilometers, we can establish that the average distance from Earth to the Sun is worth an “astronomical unit”, which is abbreviated UA Thus, we can express the distances in UA, where 1 AU is worth 92,950,000 of miles or 149.588.000 of kilometers. Normally, it is said that 1 AU equals 150,000,000 kilometers.

And finally, distance can also be expressed in terms of the time it takes for light to travel. In a vacuum, the light moves at a speed of 299,792.5 kilometers per second, although this value can be rounded up to 300,000 kilometers per second without making an excessive error. It also equals 186,282 miles per second.

Thus, we can define a distance of 300,000 kilometers as “a second-light”, that is, the distance traveled by light in a second. Sixty times that amount, that is, 18,000,000 kilometers is “one minute-light”, and sixty times this, 1,080,000,000 kilometers, is “one light-hour”.

Average distance from the Sun

Therefore, from the time of Cassini it was already known that the diameter of the solar system, from one end of Saturn’s orbit, to the other, measured almost three billion kilometers.

This figure was also overcome with the passage of time. In 1781, this diameter increased twice as much, when William Herschel , the German-English astronomer, discovered Uranus. This diameter was doubled again twice, in 1846, when the French astronomer Urbain Jean Joseph Leverrier discovered Neptune, and in 1930, when the American astronomer Clyde William Tombaugh discovered Pluto.

Average distance from the Sun

As the outermost orbit is that of Pluto, and not that of Saturn, we see that the diameter of the solar system is not three billion kilometers, but twelve billion. A beam of light would take almost half a day to traverse the solar system.

The English scientist Isaac Newton formulated the law of universal gravitation in 1684. This law explains in a direct mathematical way, the existence of the Keplerian model of the solar system and allows to calculate the orbit of a celestial body around the Sun even if it is only visible during part of said orbit.

This also made possible the study of comets. Formerly, and also in medieval times, astronomers believed that comets arose at irregular intervals and that they followed trajectories not subject to any natural law. People thought that comets predicted some kind of disaster.

The English astronomer Edmund Halley , friend of Newton , applied the gravitational calculations to the comets, and observed that some appeared in the sky every seventy-five or seventy-six years. In 1704, Halley formulated the hypothesis that all comets were really a single body that moved around the Sun in a regular ellipse, but so elongated, that most of the orbit was very far from the Earth. In that case, it was not visible, but every 75 or 76 years it passed closer to the Sun and the Earth and then it could be seen.

Halley calculated the comet’s orbit and predicted that it would be visible again in 1758. Sixteen years after Halley’s death, the comet reappeared, and since then the comet is called “Halley’s Comet.” The first appearance of this comet dates from the year 240 a. C.

At the time of its closest approach to the Sun, the Halley comet is only ninety million kilometers away from it, reaching across the orbit of Venus, although at the moment of its maximum distance from the Sun, the Halley is about three times and average Saturn’s orbit, about 5300 million kilometers. This means that in the year 1760, astronomers had already realized that the solar system was much greater than the Greeks had imagined.

Comet Halley is one of the closest to the Sun. There are others whose orbits around the Sun are so elongated that they are only visible every many centuries and even millennia. They move away from the sun, not billions of kilometers, but hundreds of billions. In 1950, Jan Hendrik Oort, Dutch astronomer, formulated a theory according to which it is possible that a great cloud of comets exists with orbits very distant from the Sun and therefore never visible.

Therefore the solar system could have a diameter of one billion kilometers or more. A beam of light would need forty days to cover this distance, so the diameter of the solar system could be estimated at more than 1 light-month.

On the other hand, the insignificance of the Earth is not only a question of distances. Through a telescope, the four outer planets, Jupiter, Saturn, Uranus and Neptune, become fully measurable spheres. But any of them is a giant compared to the Earth, although they are dwarves if we compare them with the Sun.

This is the ‘PaleBlueDot’ photograph of Earth taken by Voyager 1 on July 6, 1990. Earth is the relatively bright particle inside the blue circle.

Each of these giant planets has a satellite system, and next to them the Earth is insignificant. Of the outer satellites, the first to be discovered were the four largest of Jupiter, observed by Galileo through his first telescope in 1610. Of the great satellites, Triton, the satellite of Neptune, was discovered last. It was detected in 1846 by the English astronomer William Lassell. Later smaller satellites were discovered.

Equatorial diameter

Cumulus, nebulae and galaxies

The clusters

There are also stars that form groups. In the first rung of the scale of clusters are the globular ones, they are giant clusters of stars that began to appear in the Universe about 11,000 million years ago.

On the last step are the open clusters. Next a small introduction on these celestial bodies.

The globular clusters

More organized and compact than the open clusters are the globular clusters. A globular cluster is a ball of densely packed stars that contains hundreds of thousands of individual stars. The globular clusters of our Galaxy are scattered along a spherical halo that surrounds the Galaxy, and contain some of the oldest stars in the Galaxy.

There are about 150 globular clusters in our Galaxy. Other similar globular clusters distributed in spherical halos have been identified in other galaxies, for example more than 300 in the Andromeda M31 galaxy, and approximately 6,000 in the vicinity of M87. The number of stars is so high and the relative distances so minimal that they constitute groups gravitationally linked, in a single cubic parsec of space there can be up to 1,000 stars, in which each star travels a more or less elliptical orbit around the center of the conglomerate.

The distribution of the clusters suggests that they were formed when the Galaxy was young, 15,000-18,000 million years ago, any model of the big bang should give an age of the universe of about 20,000 million years or more. Globular clusters contain mainly Population II stars, many of which have evolved into red giants.

The object M5 (NGC 5904) of the image is a beautiful globular cluster of the northern hemisphere, belonging to the constellation of Serpent. Its location is very easy in the summer months.

Observed through a small telescope, they appear as small, fuzzy balls, but with instruments with a larger aperture (200 mm or more in diameter), these balls become thousands of stars.

The best globular cluster of the northern hemisphere is M13 in the constellation of Hercules, with a magnitude of 5.8, a diameter of 14 ‘and located 23,000 light years away, it has a width of 100 light years. Easy to find in the small trapeze of Hercules, in the line that joins the two stars Zeta and Eta.

 Open clusters

An open cluster is an irregular grouping or swarm of stars that appear to the naked eye as spots of light. They are also called galactic cluster, being located relatively close to us in the plane of our Galaxy.

Open clusters contain young, hot stars from Population I that have recently formed on the disk of the Galaxy. Open clusters worthy of mention are the following, all are visible within the northern hemisphere:

The nebulae that surround the open cluster M45, commonly called the Pleiades, are reflective (photo).

The nebulae

Nebulae are clouds of gas and dust that seem foggy to the naked eye. These celestial objects are some of the most beautiful objects that can be observed in space. The word nebulous comes from the Greek and means cloud. Nebulae play an important role, since new stars are formed in their interior due to gravitational collapse. Part of the gas was formed at the beginning of the history of the universe. The dust and the heavy elements are of more recent origin, since they have been formed in stars that liberated the interstellar medium at the end of their lives in a more or less violent way (supernovas).

Nebulae are divided into three basic types:

1. Reflection nebulae
2. Emission nebulae
3. Dark or absorption nebulae
4. Planetary nebulae

1. Reflection nebulae: are clouds of dust whose atoms reflect the light of a nearby star, so they appear the same color as the stars whose light they reflect, an example of this is the bluish nebula that surrounds the Pleiades . They appear bluer than the star because of the way starlight is scattered by the dust particles in the nebula (equivalent to the scattering of light that makes the sky blue).

2. The emission nebulae: they shine because their atoms, excited by the radiation emitted by nearby stars, become sources of radiation. They are gas clouds that receive energy radiated by nearby hot stars, and they are red in astronomical photographs due to the characteristic radiation of hydrogen in the red region of the spectrum.

The North American nebula in the constellation of the Swan, is an example of an emission nebula with an absorption nebula that defines the limits we perceive. In the zone equivalent to the Gulf of Mexico, few stars are observed due to the dark absorption nebula located in it.

3. The absorption nebulae: they are vast clouds rich in dust that absorb light and are only optically visible when behind them there is a light source on which they can stand out.

The great dark line that divides the Milky Way in two in the constellations of the Swan and the Eagle is also due to a cloud of dark dust.

4. Planetary nebulae: some nebulae represent gas envelopes detached from dying stars. The term was used by Herschell because of its circular and very delimited appearance reminiscent of a planet’s disk, hence its name.

A planetary nebula shines because the light (ultraviolet radiation) from the star with which it is associated is absorbed by the atoms of the nebula and reirradiada. They are old stars that are expelling material into space (enriching interstellar matter with heavy elements) and are on the way to becoming white dwarfs, that is, red giant star nuclei that have lost their outer layers. A planetary nebula is a transition from the red giant to the white dwarf state. There are some 1,500 planetary nebulae cataloged.

The Trifid nebula, M20, in Sagittarius, is a reddish emission nebula, while the blue color is from a reflection nebula.

The galaxies

A galaxy is a giant set of millions or billions of stars, gas and dust that are held together by gravity to form a disk galaxy of 30 kiloparsecs (1 kiloparsec = 1000 parsecs and 1 parsecs = 3.2616 light years) in diameter and surrounded by a halo of visible globular clusters. Galaxies are the most magnificent celestial objects. It is an island of matter in space.

M81 located in Uma, is a galaxy of the type Sb similar to our Galaxy, called the Milky Way.

The stars of the disk describe orbits around the center of the galaxy. The speed of each star in its orbit around the center depends on its distance from the galactic center: the stars furthest from the center move more slowly than the stars closest to it. The Sun moves in its orbit at about 250 km / s, and needs about 225 million years to describe an orbit around the Galaxy.

The parts of a spiral galaxy are:

1. Core or protuberance
2. Accretion disk.
3. Globular clusters.

From the central nucleus of the spiral galaxies two or more spiral arms that unfold around the nucleus in the form of spirals emerge at two diametrically opposed points.

In the halo and in the central region there are only red and old stars (15 million years old), especially in the globular clusters, known as Population II. The young stars, Population I, are typically hot stars of the main sequence and are found in the spiral arms of the galaxies, where a continuous star formation is triggered, the stars of the spiral arms are moving and fading steadily as They age, but the spiral structure does not wear out because blue stars are constantly being born along the inner edges of the arms. Population I stars are found in open clusters and in diffuse objects such as nebulae.

Most galaxies are too pale and too far away to be seen with the naked eye or with binoculars, except the Andromeda M31 galaxy which is visible to the naked eye as a blur, but it is fascinating to study its shapes with a telescope.

Galaxies tend to occur in groups, called clusters of galaxies linked by gravity. Our Galaxy is a member of a cluster called the Local Group, which only has about 40 members, including the Andromeda Galaxy, the Magellanic Clouds and several dwarf galaxies.

The largest cluster of galaxies close to us is the Virgo cluster, with 2,500 galaxies. The galaxy clusters are grouped into superclusters, and the Local Group is part of the same Virgo supercluster.

Walk through the sky of the circumpolar boreal region

This second tour is centered in part of the constellations of Ursa Major and Ursa Minor, which have a lot of interesting objects to observe, as well as the constellations of Cepheus, Cassiopeia and part of Perseus. Visible all year round from the northern hemisphere. It is not visible south of latitude 10ºS.

In Greek mythology, the two bears are the beautiful Callisto and her son Árcade, whom Hera transformed into bears in a fit of jealousy. Hera’s husband and Calisto’s lover, Zeus, the king of the gods, made them immortal and placed them in the heavens.

Cassiopeia was the wife of King Cepheus and mother of Andromeda. Cepheus and Cassiopeia consulted an oracle that told them that to appease the god of the sea they had to offer their daughter Andromeda as a sacrifice, so they chained her to a rock in the sea to be killed by Ceto, the sea monster. But Perseus fell in love with Andromeda and defeated the monster. Finally Perseus and Andromeda got married.

By placing the pointer over the image you can magnify it with the magnifying glass. With the mouse wheel you can enlarge or decrease the size of the magnifying glass field.

Let’s see some of the objects visible in this area.

1 Polar Star (Polaris, α Ursae Minoris). It is a Cepheid variable 46 times greater than the Sun and is at a distance of 432 light years. Visible to the naked eye, although with a telescope you can see a weak companion (mag.9) and a blue color at about 18 seconds of the Polar arc.

2 Mizar and Alcor (ζ and 80 Ursae Majoris). Of the three stars that form the car’s pole, Mizar is the central one. To the naked eye you can see a weak star just above it. It’s Alcor. With prismatic we can separate them easily, and with telescope we will see that Mizar has another companion of magnitude 4. It is Mizar B and is 14 seconds of arc.

3 Double Perseus Cluster (NGC 884 and NGC 869). This magnificent conglomeration of bright stars is known since ancient times. Because of their size, these two 100-member clusters of mids are best seen with binoculars or with a wide-field eyepiece.

4 M103 (NGC 581). At 1 degree northeast of Ruchbah we find M103. It was discovered by Pierre Méchain in 1781. The brightest stars of the cluster of magnitude 6.2 seem to trace the tip of an arrow. With a 100 mm telescope you can resolve many of the weakest stars, some of beautiful colors. Perhaps M103 is not a group of stars united by gravity, but simply a group of about 60 stars that appear as a cluster scattered from our point of view.

5 M52 (NGC 754). About 6 degrees northwest of NGC 7789 is this beautiful open star cluster. The 200 members of this cluster are located on the western edge of Cassiopeia. There is a thin row of stars that extend like an arm in an east-west direction through the cluster that are a good test for telescopes of 100 mm or more. In areas like this, replete with objects relatively easy to see with binoculars, it is a pleasure to wander around the many open clusters.

6 M81 (NGC3031) and M82 (NGC 3034). Drawing a line from γ to & alpha; Ursae Majoris and extending it to the north, these two galaxies are found. With binoculars are visible as two small cottony spots. With a telescope, the spiral M81 appears as an elliptical glow, while the irregular M82 is shaped like a cigar.

7 M108 (NGC 3556) and M97 (NGC3587), Lechuza nebula. They are below the Cart’s box, near β Ursae Majoris, or Merak. M87 is a planetary, the envelope that ejected an old star. The M108 galaxy is within walking distance. It is a spiral galaxy seen from the edge, with a milky white profile that appears flattened, with no trace of the central protuberance of most other spiral galaxies. With a magnitude of 10.1, M108 has a mottled texture with about four bright spots that can be seen on the arms. With a 250 mm telescope, there is an elongated band of dust that runs along the long axis of the galaxy.

8 NGC 188. It is the open cluster more north of the sky. It is located at 4º of Polaris towards γ Cassiopeiae and has a magnitude of 8.1. In a 6-inch telescope it appears as a great glow of 14 arc munutos with some brighter stars of magnitude 8 to 10, brighter around the western edge. An 8-inch sample shows that it has a granular texture, which illuminates smoothly towards its core. It is well above the plane of the Milky Way. Here, the forces of gravitational tides that attract open clusters are reduced and have allowed this cluster to remain together for 6.8 billion years.

9 IC 3568. It is a planetary nebula in the constellation of Camelopardalis. Also called Lemon Slice Nebula for the images that Hubble sent. It has a remarkably simple spherical shape. It has a magnitude of 10.7 and a diameter of 18 “. A 12-inch telescope shows a weaker outer ring surrounding a brighter core 10 “in diameter. It is located about two fifths of the distance between Polaris and Kappa Draconis.

10 M101 (NGC 5457). The Molinillo Galaxy. This beautiful spiral galaxy is located 5 degrees east of Mizar and Alcor. It is one of the largest and most beautiful front spirals that can be seen and, although it is quite luminous, around magnitude 9, it is also diffusive, so it is difficult to locate even with a 250 mm telescope. A dark sky and few increases with wide field is the best way to detect the knotty arms that extend from the nucleus. It was discovered by Pierre Méchain in 1781.

11 NGC 654, NGC 663 and NGC 659. About half a degree northwest of Ruchbach, within the same field of binoculars or finder, is an accumulation of open clusters in the form of U: NGC 654, NGC 663 and NGC 659. NGC 654 consists of 60 stars in loose association, but it is very easy to see with binoculars and appears as a diffuse glow of small and weak stars. NGC 663 is half grando south of NGC 654. It has a rounded appearance, similar to a mixture of open and globular cumulus if we look at it with 150 mm telescope. It has about 80 stars. Finally, NGC 659 is half a degree southwest of NGC 663. It is an X-shaped cluster formed by about 40 stars. Near it is the yellow-gold double star of magnitude 5.8, 44 Cassiopeiae, which is not a member of the cluster.

12 Caph (β Cassiopeiae). This double star and pulsating variable of short period is of a rare type called Delta Scuti. It is very difficult to detect its variability visually because its magnitude of 2.2 fluctuates very slightly during its cycle is only 2 hours long.

13 NGC 7789. Four degrees southwest of Caph we find this broad open cluster. It is quite large and lies between the semi-regular yellow variable 7 Rho (ρ) Cassiopeiae and the broad white multiple-star system 8 Sigma (σ) Cassiopeaiae. It can be seen very well with binoculars or a wide field eyepiece because it covers an area of ​​the apparent size of the Moon.

14 Delta (δ) Cephei. With telescope we can solve this double star formed by a pale orange component and a blue one. The yellow star is the prototype of the Cepheid variables, yellow supergiants whose sizes and brightness pulsate regularly.

15 Mu (μ) Cephei, garnet star of Herschel. This cold supergiant star is so big that if it were placed in the place of the Sun, it would eat Jupiter. It is one of the reddest stars in the sky that can be observed with small telescopes.

Walk through the sky of Andromeda and Triangulum

This walk can be observed from both hemispheres. There are many interesting objects in this area, among which the Andromeda and the Molinillo galaxy stand out. The Andromeda galaxy is the furthest object visible to the naked eye. Of course, for this, we need to leave the city.

The darker the sky, the better. But you do not need as much darkness, but rather, know where it is located and look out of the corner of your eye and not in front, because with this area you can see weaker objects better. Of course, it looks much better with the help of binoculars and much better with a telescope, even if it is small. This galaxy is known since ancient times.

By placing the pointer over the image you can magnify it with the magnifying glass. With the mouse wheel you can enlarge or decrease the size of the magnifying glass field.

Let’s see some of the objects visible in this area.

1 Alpheratz (α Andromedae). This star marks one of the corners of the Pegasus square, so it is sometimes also called Delta Pegasi. It is a bluish-white double star of magnitude between 2.02 and 2.06. It is α Andromedae, making it the brightest star in the Andromeda constellation. It is 97 light years from the Solar System. With a telescope of 200 mm or more, it is possible to see his companion, of magnitude 11.3.

2 Andromeda Galaxy (M31). To locate it we can use as reference the stars β Andromedae and μ Andromedae. As I said before, it is the farthest object that can be seen with the naked eye. When we observe it, we are looking at 2,200,000 light years. It is a large and bright object. We need dark sky to see it with the naked eye. It appears like a cottony cloud. With telescope, low power eyepieces are preferable, to be able to see it whole. Otherwise, we can only see its core. In the year 1924 Hubble showed that M31 was not part of the Milky Way. To do this, he compared the luminosity of the Cepheid variables in M31 and the Milky Way, and found that they were much weaker in M31 because they are much farther away.

3 M110 (NGC 205). It is a satellite elliptical galaxy of M31 and belongs to the Local Group. It is about 2,690,000 light years from Earth and it has a magnitude of 8, so it can not be observed with the naked eye. In a 100 mm telescope it appears as an elongated spot brighter by its nucleus. It is the last object on the list of Charles Messier .

4 M32 (NGC 221). It is an elliptical galaxy near M110. In 100 mm telescopes it appears as an oval spot of light. With larger telescopes it looks even better.

5 R Andromedae. It is located southwest of M32. It is a long-term Mira type variable, ranging from magnitude 5.3 to 15 in 409 years. Sometimes it is visible with binoculars, but when it is in its minimum magnitude it is still difficult to see it with 200 mm telescopes. To the west of R are the stars θ Andromedae, σ Andromedae and ρ Andromedae forming a triangle that helps locate the star when its magnitude is minimal.

6 Almach (γ Andromedae). It is one of the best doubles to observe with small telescopes for its contrast of colors. The primary star of magnitude 2.3 is an orange giant and its companion, which is in turn a binary, of magnitude 5.1 is greenish. The companion of the binary is, in turn, double too, so it is a quadruple system.

7 NGC 752. It is located south of Almach. It is an open cluster of about 70 stars that can be seen with the naked eye with dark skies. Seen with binoculars you can see the chains and knots of the stars that form a twisted X inside this magnificent cluster.

8 Galaxy of the Mill (M33). It is located southwest of NGC 752. Although it is a bright object of magnitude 5.5, it is difficult to see as it appears from the front and is very widespread. In dark sky and with binoculars it appears as a diffuse glow, but with a 200 mm telescope and a wide-field eyepiece you can see its diffuse arms.

9 ι Tri. It is a double with an amazing color contrast. The primary is yellow of magnitude 5 and the secondary is blue of magnitude 6.5.

Interesting data

• How many stars can we see

  The night sky seems to have millions of stars visible. That’s because we live in a galaxy that has hundreds of millions of stars. However, we can not see them with the naked eye. It turns out that the heavens of the Earth have, at most, around ten thousand stars that can be seen with the naked eye.

• How many planets have rings

  In our Solar System 4 of the 9 planets have rings: Jupiter, Saturn, Uranus and Neptune. It also has Cariclo rings, one of the centaurs. Of all of them, Saturn is the one with the largest ring system, so much so that they are visible from Earth with a small telescope. The rings of Jupiter were first seen in 1979 by Voyager 1, since they are quite difficult to see with telescopes. The ring system of Neptune is composed of 5 fairly weak rings. Finally, Uranus has 13 very dark rings.

• How many rings does Saturn have?

  Saturn has a system of 4 rings that were first observed by Galileo Galilei in July 1610. Rings A and B are very bright. There is a distance of 4,800 km between one and another, which is the division of Cassini , a dark band discovered by him in 1675. Inside there is a satellite shepherd: Mimas. Ring A is divided, in turn, into two parts by the division of Encke. The edge of ring A is also guarded by the satellite shepherd Atlas. Ring C is weaker and D weaker still. The order of the rings, from inside to outside is: D, C, B, A. The space probes Voyager and Cassini sent high-resolution photographs in which some novelties were discovered: in the outer area of ​​the ring A, there are 3 rings very pale, called E, F and G. Ring F has 2 satellite satellites, Prometheus and Pandora, the first in its internal zone and the second in the external zone, which give it shape. Later another ring was discovered between the F and the G, the ring H.

• The size of our galaxy

  Our galaxy has the shape of a disk, with a thick central area and a large spherical cloud, called halo, of old stars surrounding the disk. If we look at where the stars and visible gas reach, the diameter of the disk and the halo together is 100,000 light years. On the other hand, the disk has a thickness between 1,000 and 12,000 light years. It is known that there is matter formed by hydrogen in the form of molecules that are not observed in visible radiation. This hydrogen cloud surrounds the entire galaxy, the disk and the halo together, although not homogeneously, and can reach distances from the galactic center to twice the radius of the disk.

• The oldest astronomical observatory still preserved

  The observatory of Cheomseongdae, in Kyongju, South Korea, was built between 632-647 and was used to observe the stars and predict the weather. It measures 9.17 m high X 5.35 m at the base.

• The first living being to travel to space

  The first living creature that orbited the Earth was the dog Laika, which in Russian means “barking”. It was on November 3, 1957 on board the Soviet ship Sputnik 2. After Laika, the USSR sent 12 dogs to the space, of which only five arrived alive back to Earth.

• Who invented the telescope

•  

  The Dutchman Hans Lipershay tried to patent it, but he was denied “because it is so simple to copy” that it was such an object, which indicates that, probably, telescopes already existed throughout Europe, although none was suitable for astronomy. There are indications that a Girona artisan named Joan Roget could have manufactured the first telescopes. But it was Galileo Galilei who in 1609 was the first to aim for heaven, thus beginning four hundred years of discoveries about the cosmos.

•  

• The first woman who flew into space

  In 1963 the Soviet Valentina Tereshkova traveled around the Earth 48 times on the Vostok 6 spacecraft. The first American woman to travel into space was Sally Ride on board the Challenger spacecraft in 1983 and 1984.

• The size of our galaxy

  It has an average diameter of 100,000 light-years and is estimated to contain some 200,000 million stars. The distance from the Sun to the center of the galaxy is around 27,700 light-years. The thickness of the Milky Way is 16,000 light years in the center, becoming smaller in the outer zones, approximately of 3,000 light-years.

• The hottest planet surface in the Solar System

  The surface of Venus, 470º C. At its hottest time, Mercury reaches 427º C. The thick atmosphere of Venus retains the heat of the Sun, so the temperatures at midnight are as hot as at noon. There the rocks are so hot that they have a red glow.

• The coldest surface recorded in the Solar System

  Triton, the largest satellite of Neptune. When the Voyager 2 probe passed this world in 1989, it discovered an extremely cold surface with a temperature of -235ºC.

• The largest crater in our Solar System

  The basin of Aitken, in the south pole of the Moon, of 2,500 km in diameter. It was not discovered until the Clementine probe visited the Moon in 1994. Scientists used the Clementine data to map the lunar surface. It was then that they discovered this basin, a vast depression on the hidden face of the Moon that is more than 12 km deep.

• The highest mountain in the Solar System

  Mount Olimpus, on Mars, reaches 24 km high. The second is the Maxwell Mountains, on Venus, which rise 11 km above the average level of the planet’s surface. The officially highest peak on Earth is Mount Everest, which reaches 8.8 km above the mean sea level. However, Hawaii’s Mauna Kea can also claim to be the tallest, since it rises 9 km above the ocean floor on which it sits.

• The largest canyon in the Solar System

  Valles Marineris, on Mars, about 4000 km long, with a maximum width of about 600 km and a maximum depth of 8 km. If it were in the United States, this canyon would extend from San Francisco, on the west coast, to the Appalachian mountains of Virginia, near the east coast. In Europe, it would occupy from Paris to the Ural mountains, in Russia.

• The largest planet in the Solar System

  Jupiter, which has a mass of 317.8 lands and about 11 times its diameter. Jupiter has more mass than all the rest of the planets, satellites, comets and asteroids.

• The largest known planet

•  

  An unnamed planet, orbiting the star HD114762. This planet seems to have 11 times the mass of Jupiter, although some astronomers think it may be a brown dwarf, an object that is like a small, dark cold star. If it is indeed a brown dwarf, then the largest planet would be one that is 6.6 times the mass of Jupiter and orbits around the star 70 Virginis.

• The largest satellite in the Solar System

  The satellite of Jupiter, Ganymede, of 5268 km in diameter. If it orbited around the Sun instead of around Jupiter, it would be classified as a planet. It is larger than Mercury and Pluto.

• The biggest shower of stars

  The Leonids of November 13, 1833, when they counted up to 200,000 meteors per hour. The spectators said that the meteorites “looked like snowflakes”, although many thought that the end of the world had arrived. The impressive display helped astronomers realize that meteorites entered the Earth’s atmosphere from outer space, and were not a typical phenomenon of the Earth as rain.

• The largest meteorite

  The Hoha meteorite, in Namibia, of about 60 tons, a weight similar to that of 9 elephants. Discovered in 1920, this 3 m long meteor continues where it fell. Originally it was even bigger since part of the meteorite has suffered erosion.

• The largest asteroid

  1 Ceres, 913 km in diameter. The largest asteroid of all was also the first to be found: it was discovered on the first day of the 19th century, on January 1, 1801. It was discovered by Giuseppe Piazzi from the Palermo observatory.

• The largest object of the Kuiper Belt

  Quaoar is 1300 km in diameter or what is the same, half Pluto. Orbit beyond Nepturno, in the so-called Kuiper Belt, and it is the largest smaller planet known. It’s bigger than all the asteroids together in the asteroid belt.

• The comet closest to Earth

  Comet Lexell passed in 1770 at a distance of 2.2 million km from Earth, less than 6 times the distance to the Moon. Although it got so close, this comet did not develop much tail and the head did not exceed the size equivalent to 5 times that of the Moon in our night sky.

• The longest comet tail

  That of the Great Comet of March 1843, 300 million km long. It was so long as to reach from the Sun until it passed the orbit of Mars.

• The biggest star in our night sky

  Betelgeuse, in Orión, has a diameter of about 800 soles. If it replaced the Sun in our Solar System, this red supergiant star would occupy beyond the orbit of Jupiter.

• The highest mass star

  Eta Carinae has a mass about 150 times greater than the Sun. Astronomers are not sure if Eta Carinae is a star or two.

• The lowest mass star

  Gliese 105C has a mass of 10% of that of the Sun. This is the smallest a star can be so that it can still be considered a true star (an object that converts hydrogen into helium).

• The nearest star

  Próxima Centauri is the third member of the Alpha Centauri System. This red and cold dwarf star is about 4.2 light years, about 0.1 light year closer to us, than the other two stars in the system.

• The globular star cluster with the highest number of stars

  Omega Centauri, with 1.1 million stars. This globular cluster measures about 180 light years in diameter.

• The highest mass galaxy

  The elliptical giant M87, in the constellation Virgo, with a mass equivalent to at least 800,000 million suns. M87 is part of the galaxy cluster of Virgo.

• The galaxy of least mass

  The elliptical dwarf galaxy Pegasus II, which has a mass equivalent to 10 million suns. There may be smaller galaxies; but, since they are not very bright, astronomers can not detect them unless they are close to us.

• The nearest galaxy

  The dwarf galaxy of Can Mayor. This galaxy is 25,000 light years from the Solar System and 42,000 light years from the center of the Milky Way. It is the current holder of this record, but new elliptical dwarf galaxies are discovered every year and perhaps an even closer one has been discovered.

• The object visible to the farthest eye

  The Andromeda galaxy (M31), which is 2.9 million light years away. When you look at this galaxy, you can see the light that came out of it when the last ice ages began on Earth. The spiral galaxy M33, in the constellation of the Triangle, is farther away and weaker, although someone with a very sharp sight may see it.

• The furthest object detected

  An unnamed galaxy in the Big Dipper, at 12,600 million light years, although it may not hold the record for long.

• The hottest planet

  The hottest planet discovered so far, according to New Scientist magazine in 2008, is the WASP-12b. This planet has a temperature of 2250º C, which means that it is half hotter than the Sun. Its mass is 1.5 times greater than that of the planet Jupiter. The finding was made by a group of European astronomers and the Institute of Astrophysics of the Canary Islands participated in it.

• The youngest supernova of the Milky Way

  A group of astronomers discovered, thanks to the Chandra Telescope of NASA and the National Observatory of Radio Astronomy, in Green Bank, West Virginia (USA), in 2008, the rest of the youngest supernova of the Milky Way. It happened only 140 years ago and the rest of it had been tracked for two decades. This is of special importance since the last supernova seen in the Milky Way was discovered by Johannes Kepler , German astronomer, in 1604.

• The largest telescope in the world

  It will be the Canary Gran Telecopio (GTC), and it will have an area equivalent to a circular mirror of 10.4 meters in diameter. It saw its first light on July 13, 2007, but when it is 100% operational, it will be one of the most advanced and with the best features for astronomical research. With a dome of 33 meters in diameter, its primary mirror will consist of 36 hexagonal glass-ceramic elements that have a diagonal of 1.9 meters each. Coupled together, they will form a hexagon of 11.4 meters and 16 tons of weight, equivalent to optical effects to a circular mirror of 10.4 meters in diameter. The GTC is being built on an area of ​​5000 square meters at the Roque de los Muchachos Observatory on the Canary Island of La Palma, at an altitude of 2400 meters.

Advances in Astronomy through time

Before the 11th century

• 32000 BC In the Stone Age man makes incisions in bones to represent the lunar phases, which is possibly the oldest astronomical record.
• 4000 BC The city of Ur is founded by the Sumerians, who give their name to the first constellations.
• 3000 BC The Egyptians build the pyramids of Giza using astronomical knowledge. In England the first phase of Stonehenge is erected.
• 2000 BC circles are added to Stonehenge. The Babylonian civilization is born.
• 1300 BC The Chinese invent what was probably the first calendar in the world.
• 600 BC Genuine science is born in Greece. The first scientist, Thales of Miletus, suggests that the Earth is a disk and floats on water.
• 520 BC Anaximander of Miletus states that the earth’s surface is curved and that the Earth is a cylinder.
• 500 BC The first to suggest that the Earth is a sphere was Pythagoras. According to him, the heavens are composed of crystalline spheres with the Earth in the center.
• 350 BC Aristotle states that the Earth is the center of the universe. This theory will be maintained for more than 1800 years. It also describes the phases of the Moon and the mechanism of eclipses.
• 300 BC Aristarchus of Samos is the first to propose the idea, soon forgotten, that the Sun is the center of the universe (heliocentric theory) .
• 240 BC First sighting of the comet that we now call Halley in China.
• 235 BC Eratosthenes of Cyrene makes the first accurate measurement of the diameter of the Earth.
• 165 BC First observations of sunspots in China.
• 150 BC Hipparchus of Nicea calculates the duration of the year with an accuracy of minutes, makes the first accurate measurements of the distance between the Moon and the Sun, discovers the precession of the Earth, makes the first catalog of stars and invents the scale of magnitude of the brightness of the stars.
• 150 AD Claudio Ptolemy develops Aristotle’s idea of ​​a universe with the Earth as the center and is the first to propose the concept of epicycles to explain how the planets move.

Eleventh century

• 1054 Chinese astronomers discover a supernova in Taurus, the explosion that created the Crab Nebula.
• 1066 Comet Halley reappears in the sky.

13th century

• 1250 Albertus Magnus translates texts of Aristotle, adding his own comments and experiments, which provides the basis for later, with his disciple Thomas Aquinas, incorporate Aristotelian thoughts to Catholic theology.
• 1258 Hulagu Khan establishes the Observatory of Maraghe, in Azerbaijan, which was active for more than fifty years. It came to contain a library with more than 40,000 volumes.
• 1263-1272 Alfonso X El Sabio orders Yhuda b. Mose and Rabiçag, both Jews who lived in Toledo, the preparation of the Alfonsí Tables. They reached a rapid diffusion in all Europe, first in manuscript copies and later in printed editions.

XIV century

• 1303 Giotto paints the frescoes in the Chapel of the Arena, Padua. Two years before, he had seen Halley’s comet and was inspired by it to paint the Adoration of the Magi, the first pictorial representation of this celestial body.

XV century

• 1450 Nicolás de Cusa affirms that the Earth is not the center of the universe and that in the universe there is no stillness, but everything is in movement, including the Sun. It also speculates about the existence of other worlds.
• 1467 Johannes Muller Regiomontano calculates his breasts table “De triangulis Onmimodis”, published posthumously in 1533.
• 1472 Johannes Muller Regiomontano determines the position of a comet, which would later be called Halley.
• 1483 First edition printed in Venice of the Tablas Alfonsíes, by Alfonso X El Sabio.

Century XVI

• 1519 The Portuguese navigator Ferdinand Magellan was the first European to observe the “Magellanic Clouds”, two satellite galaxies of the Milky Way, while traveling around the Earth.
• 1531 Petrus Apianus, observed the passage of Comet Halley and suggests that the cometary tails point in the opposite direction to the Sun.
• 1532 Nicolaus Copernicus finishes his masterpiece “De Revolutionibus orbium coelestium” (On the movements of the celestial spheres). He wrote it over 25 years of work and it was published posthumously.
• 1543 Nicolás Copernicus proposes, on his deathbed, a Solar System centered on the Sun. His idea soon finds acceptance, although the Church considers it heretical.
• 1576 Tycho Brahe calculates exactly the movement of the planets.

XVII century

• 1608 The telescope is invented by Hans Lippershey.
• 1609 Johannes Kepler uses Tycho’s observations to discover that the orbit of Mars is elliptical.
• 1610 Galileo Galilei uses a telescope for the first time in astronomy. Discover, among other things, satellites around Jupiter, craters on the Moon and stars in the Milky Way.
• 1619 Kepler discovers a mathematical relationship between the orbital period of the planets and their distances from the Sun, and proposes them as three laws of the movement of the planets, now axiomatic.
• 1655 Christian Huygens discovers Titan, the most important satellite of Saturn, and suggests that Saturn’s rings are composed of small particles.
• 1675 Giovanni Cassini discovers the division of the rings of Saturn, division that still bears his name.
• 1687 Isaac Newton publishes the Principia.

Century XVIII

• 1705 Edmund Halley predicts that the comet that bears his name today will be seen again in 1758, and so it was.
• 1755 Immanuel Kant correctly states that planets and stars come from condensed interstellar clouds.
• 1759 Comet Halley makes the first predicted return in advance.
• 1771 Charles Messier publishes his first catalog of celestial objects, which he completed in 1781.
• 1781 William Herschel discovers Uranus. He was the first to use the denomination “planetary nebula”, discovered several satellites of Saturn and published a catalog that served as the basis of the New General Catalog (NGC).

XIX century

• 1801 Giussepe Piazzi , from the obsertario of Palermo, discovered the first asteroid: 1 Ceres. It was the first day of the 19th century, on January 1, 1801.
• 1814 Joseph von Fraunhofer discovers dark lines in the spectrum of the Sun.
• 1838 The star distance of a star, 61 Cygni, is measured for the first time.
• 1842 Christian Doppler states the Doppler effect, widely used today to establish distances and speeds in astronomy.
• 1845 Lord Rosse discovers the first observed spiral galaxy, the Whirlpool Galaxy, which was then called spiral nebula.
• 1846 Johann Galle and Heinrich d’Arrest find Neptune using the predictions of Urban Leverrier and (independently) John C. Adams.
• 1849 The speed of light is measured with a deviation of 5% of the current value.
• 1859 James Maxwell mathematically demonstrates that Saturn’s rings are microparticles, as Huygens suggested 204 years earlier.
• Decade of 1860 The spectroscope, used for the first time, revolutionizes astronomy and reveals the composition, until then only suspected, of celestial objects.
• 1873 The craters of the Moon are attributed to meteorite impacts.
• 1877 Two satellites are discovered on Mars.
• Decade of 1880 Photography becomes an important tool in astronomy.
• 1882 Lewis Boss directs an expedition to Chile to observe the transit of Venus.
• 1884 The meridian of Greenwich is established as principal.
• 1887 The Michelson-Morley experiment demonstrates that the “ether” (the medium in which light was supposed to propagate) is fictitious.
• 1888 Johan Dreyer publishes the New General Catalog of nebulae and star clusters (NGC) in which 7840 celestial objects are included.
• 1895 The first addition to the NGC, called Index Catalog (IC), adds another 1529 objects.

Twentieth century

• 1901 Annie Jump Cannon develops the system of classification of stars of Harvard that was adopted like standard.
• 1902 The Spanish astronomer, José Comas Solá, observing from the Fabra Observatory, of which he was director, demonstrates the existence of an atmosphere on Titan.
• 1904 Jacobus Cornelius Kapteyn, Dutch astronomer, announces that the movements of the stars are not random. Later this announcement was understood as the first evidence of the rotation of the Milky Way.
• 1904 Foundation of Mount Wilson Observatory, California.
• 1904 Charles Dillon Perrine discovers Himaliá, satellite of Jupiter, that in that moment was designated like Jupiter VI.
• 1904 Edward Walter Maunder publishes the results of his work at the Royal Observatory of Greenwich, with the peculiar shape of the diagram in the form of “butterfly wings”.
• 1905 Albert Einstein publishes the Special Theory of Relativity.
• 1905 George Ellery Hale discovers solar magnetism.
• 1905 Charles Perrine discovers Elara, satellite of Jupiter, which at that time was designated as Jupiter VII.
• 1906 Sherburne Wesley Burnham publishes the Burnham Catalog of Double Stars, which contained 13,665 references of double stars.
• 1906 The spiral structure of the Milky Way is proposed for the first time.
• 1908 On June 30 an aerial explosion occurs in the vicinity of Tunguska, Siberia. The Tunguska bolide raised many hypotheses about what happened, being finally attributed to a comet or an asteroid.
• 1908 Ejnar Hertzprung divides stellar populations into giants and dwarfs.
• 1908 Philibert Jacques Melotte discovers a moon of Jupiter, today known as Pasiphae, although at that time it was designated as Jupiter VIII.
• 1908 Lewis Boss calculates the converging point of the Hyades cluster.
• 1908 Following his New General Catalog of Nebulae and Star Clusters, John Louis Emil Dreyer publishes two Supplementary Index Catalogs.
• 1908 – 1912 Henrietta Leavitt discovers that Cepheid variables with short periods are less luminous than those of long periods, thus finding a valuable method to calculate stellar distances.
• 1909 The Evershed effect is discovered, named after John Evershed, who detected this phenomenon while working at the Kodaikanal Solar Observatory in India and observed the spectral lines of sunspot light.
• 1911 Ejnar Hertzprung and Henry Russell individually create a graph, now known as the HR diagram, which indicates the relationship between absolute magnitudes and their temperature.
• 1912 Vesto Slipher observes “spiral nebulae” that move away from Earth, the first detection of the expansion of the universe.
• 1912 Cosmic rays are discovered thanks to balloon flights.
• 1915 Einstein publishes the General Theory of Relativity, which greatly influences astronomy. The first white dwarf is known: Sirius B.
• 1917 The 2.5m Hooker telescope is installed on Mount Wilson, California.
• 1923 Edwin Hubble discovers that the “spiral nebulae” are actually galaxies external to ours, that all are moving away at great speed and that the Universe is expanding.
• 1929 Hubble’s observations offer estimates of the age of the universe and the rate of its expansion.
• 1930 Clyde Tombaugh discovers Pluto.
• 1931 Karl Jansky detects radio waves from space for the first time.
• 1937 Grote Reber detects radio waves from the center of the galaxy.
• 1938 Hans Bethe explains the brightness of the Sun by means of nuclear reactions.
• 1946 Cygnus A, the first known radio galaxy, is identified.
• 1948 Construction of the 5m Hale telescope on Mount Palomar, California, is completed.
• 1948 Fred Hoyle uses the term “Big Bang” for the first time.
• 1948 Fred Whipple correctly explains the nature of comets.
• 1948 George Gamow, Ralph Alpher and Robert Herman deduce the formation of the chemical elements in the Great Explosion.
• 1952 Walter Baade discovers that galaxies are twice as far from what was believed until then.
• 1957 The space race begins with the launch of Spunik 1 by the Soviet Union.
• 1959 The first photographs of the hidden face of the Moon are made.
• 1961 The first man in space is Yuri Gagarin, from the Soviet Union.
• 1962 The Mariner 2 probe travels to Venus and detects the dense atmosphere and surface heat of the planet.
• 1963 Maarten Schmidt discovers the remoteness of quasars. The first known source of X-rays discovered, apart from the Sun, is Taurus X-1.
• 1965 Arno Penzias and Robert Wilson detect microwave background radiation, which provides a real basis for the Big Bang theory.
• 1965 The Mariner 4 probe is the first spacecraft to fly over Mars.
• 1967 Jocelyn Bell-Burnell discovers pulsars. They are immediately identified as neutron stars.
• 1969 Neil Armstrong and Edwin Aldrin make the first manned landing on the Moon (Apollo 11).
• 1970 US Satellites they discover the first gamma ray explosion.
• 1971 The first black hole candidate is discovered: Cygnus X-1.
• 1973 The Pioneer 10 probe flies Jupiter for the first time.
• 1974 The Mariner 10 probe takes the first photographs of the clouds of Venus and the craterized surface of Mercury.
• 1975 The Venera 9 probe takes the first photographs of the surface of Venus.
• 1976 The Viking 1 and 2 probes land on Mars in an unsuccessful attempt to detect life.
• 1977 Discovery of the rings of Uranus from Earth.
• 1978 James Christy discovers Charon, the satellite of Pluto.
• 1979 Voyager 1 and 2 fly over Jupiter and discover their rings. Pioneer 11 flies over Saturn for the first time.
• 1980 Alan Guth describes in detail that the early universe expanded with extreme rapidity in a process called cosmic inflation, thus explaining the phases immediately following the Big Bang.
• 1980 Voyager 1 studies Saturn in detail.
• 1980 The Very Large Network of radio telescopes starts operating in New Mexico.
• 1981 Astronomers discover the first void in space, now it is known that there are empty regions among stellar superclusters.
• 1982 The first millisecond pulsar is discovered.
• 1983 IRAS, the infrared astronomical satellite, studies the infrared firmament in its entirety.
• 1986 The Voyager 2 probe flies over Uranus for the first time.
• 1987 In the Greater Cloud of Magallanes appears supernova 1987A, the first visible to the naked eye in almost 400 years.
• 1989 The Voyager 2 probe flies over Neptune for the first time.
• 1989 Margaret Geller and John Huchra explain that galaxies agglomerate in “walls” and “holes” in the universe.
• 1989 Evidence for the existence of “dark matter” is found.
• 1990 Launch of the Hubble Space Telescope. Weeks later it is detected that the main mirror is defective.
• 1990 The Magellan probe begins to map Venus by radar.
• 1991 The Galileo space probe, on its way to Jupiter, flies for the first time an asteroid, 951 Gaspra. Launch of Compton, the gamma ray observatory.
• 1992 The COBE satellite discovers “lumps” in the cosmic background radiation.
• 1992 The first 10m Keck telescope is opened in Mauna Kea, Hawaii.
• 1994 Comet Shoemaker – Levy 9 collides with Jupiter.
• 1995 The first extrasolar planet is discovered. The Galileo probe reaches Jupiter, launches a capsule in its atmosphere and begins to orbit around the planet and between its satellites.
• 1996 It is discovered that the Milky Way has a massive black hole at its center. The possibility of fossilized Martian microbes is detected in a meteorite from Mars.
• 1997 The Mars Pathfinder probe lands on Mars with the Sojouner SUV.
• 1998 It is discovered that the expansion of the universe is accelerated.
• 1999 Chandra, the orbital X-ray observatory, is launched.
• 2000 Water filtrations and extensive sedimentary deposits on Mars are discovered.

XXI century

• 2002 Exceeds the hundred known number of extrasolar planets.