Why is Mars red when viewed from the earth?

Including our earth, there are nine planets that have been discovered in the solar system (excluding Pluto), namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Five of them are easy to see. They are Mercury, Venus, Mars, Jupiter and Saturn. The other three are far away from us and it is difficult to observe. There are many asteroids between the orbits of Mars and Jupiter, and we can only see a few bright ones at most.

Planets all revolve around the sun from west to east, and period of revolution is from the 88th day of Mercury to the 248th day of Pluto. We look at other planets starting from the moving earth and only see their movements relative to the earth. Because the speed of planets in orbit is different, the apparent motion of the planets we "see" is a bit complicated.

1, apparent motion of inner planet

There are only two inner planets. They are Mercury and Venus. Relative to the sun, the inner planet always just swings back and forth near the sun, and the angular distance from the sun is limited to a certain range.

There are several situations in the position of the internal astrology relative to the sun: when the earth, the internal planet and the sun are in a straight line, the internal planet is called downward convergence, and when the internal planet is on the extension line of the earth and the sun, it is called upward convergence. Before and after the upper and lower conjunctions, the inner planets were too close to the sun and were submerged by sunlight, so we couldn't see them.

When the angular distance between the inner planet and the sun is the largest, it is called large distance, which can be divided into east distance and west distance. Obviously, the inner planet is located in the east of the sun when it moves eastward. We can see it on the western horizon before and after the sun goes down, which is called the evening star. The inner planet is the morning star far to the west, which can be seen on the eastern horizon before and after the sun rises. The distance between Mercury and Venus will not exceed 28 degrees and 48 degrees respectively.

The positional relationship between the earth and the internal astrology relative to the sun, such as upward or downward, returns to the original positional relationship after a period of time, which is called planetary rendezvous. During the rendezvous, the apparent motion and visibility of the inner planet are as follows:

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2. Apparent motion of outer planets

Mars is an exoplanet as far as Pluto. Relative to the sun, the angular distance between the outer planets and the sun is not limited, and the range can be 0 to 360 degrees.

There are several situations in the position of amateur astrology relative to the sun: when the earth, the sun and the outer planets are in a straight line and the sun is in the middle, it is called merging. Obviously, before and after this period, the outer planets were invisible; If the earth is between the sun and an alien planet, it is called a collision. Obviously, when the outer planet is closest to the earth and makes a 90-degree angle with the sun before and after the collision, it is called a square photo. There are two kinds of photos: oriental photos and western photos. When the sun shines in the east, the time to observe it can be from sunset to midnight; When the sun shines in the west, it is observed from midnight to sunrise.

Like inner planets, outer planets have their own rendezvous periods. During the rendezvous, the apparent motion and visibility of the outer planets are as follows:

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3. Ways to find planets

At night, the sky is full of stars, including planets and more stars. How can we find the planet we want to observe from so many stars? The best way is to have an astronomical almanac of that year, such as the astronomical almanac published every year in China. In the almanac, the positions of the planets and so on are introduced in detail, and there are many useful materials. For those who have no almanac for the time being, we provide some features of planets to help you find them from the stars as soon as possible. Of course, you can also use the electronic star map, which is mainly recommended here (skymap 10.0.0).

Planets always move near the ecliptic. We can take a star map and compare the bright stars near the ecliptic with the actual starry sky. The star not marked on the map is probably a planet.

Planets are generally brighter than stars, and the change garden of brightness of the five planets is as follows:

Venus: -4.4 to -3.3 and so on. White light, even in the darkest time, is brighter than any star.

Mars: -2.8 to+1.6 and so on. Flaming red, especially when the brightness is high.

Jupiter: -2.5 to 1.4 and so on. Even in the darkest hours, it is one of the brightest stars in the sky.

Mercury:-1.9 to+1. 1 and so on. It can only appear as a morning star at dawn in the east, or as a dim star on the western horizon at dusk, when there will be no bright stars nearby.

Saturn: -0.4 to +0.9, slightly yellow, with only a dozen or twenty such bright stars all day.

Planetary brightness is basically stable and flicker is small; The stars are twinkling all the time.

The position of the planet is changeable, which can be seen after several days or days of observation, while the position of the star in the starry sky can be said to be unchanged.

Step 4 observe the planets

Observing and studying planets is one of the important tasks of astronomers.

We astronomy enthusiasts can also carry out many observation projects, directly with the naked eye, or with binoculars and small telescopes.

Observe Mercury and Venus.

These two planets can only be observed for a period of time before and after the easterly distance or the westerly distance. For Venus, this time can be as long as several months, while for Mercury, the observation time of more than 10 days is not bad!

From the earth, both mercury and venus have phase changes like the moon, which can only be seen through telescopes. It would be interesting to take a group of photos of Venus' phase transition. However, it should be noted that when Venus is far away from us, it is five or six times different from when it is near, and the apparent diameter of Venus seen from the telescope will also be five or six times different. Observing Venus with a small telescope, especially when Venus is close, it is possible to see that the edge of Venus is a little blurred and not so clear, because there is an atmosphere around Venus.

Observe mars

You can see the blood-red color of Mars only with naked eyes. If you observe it with a small telescope, you can further see the color change of the surface of Mars. The white polar caps at the poles of Mars must be seen with a small telescope. Generally speaking, you can see its polar cap at the North Pole or at the South Pole. When the position is right, you may see two polar crowns at the same time. With the seasonal change of the surface of Mars, the size of the polar cap is also changing. Whether you see one or two polar crowns, try to take pictures. After a period of time, it will help you understand the changes of the Martian season.

The apparent motion of Mars is very complicated. I suggest you take a picture of the position of Mars in the starry sky every few days. After half a year or more, you will be surprised.

In general, Mars can be seen clearly with a small telescope, and sometimes some dark spots, that is, some lowlands or canyons on its surface, can be seen. If you think the surface looks a little fuzzy, it's not necessarily your telescope. Maybe there is a big sandstorm on the surface of Mars.

When Mars is farthest from the Earth, it can reach 65.438+0.20 billion kilometers. Less than 58 million kilometers recently. Mars eclipses once every two years and once every 15- 17 years, when Mars is very close to the earth. Mars is only about 55 million kilometers away from the earth at the time of favorable impact, which is an excellent opportunity to observe it.

Observe Jupiter

For astronomy enthusiasts, Jupiter is a planet with many observation projects. From the telescope, you can see at a glance that it is a flat celestial body, which is related to its fast rotation speed. The rotation period of Jupiter's equatorial part is only about 9 hours and 50 minutes. In astronomical literature, the oblateness of Jupiter is set at 0.0648, that is, 6.48%. You might as well make a simple measurement through your own observation. You can average the results several times to see how consistent your observation results are with the data in the book.

You can also see that there are some stripes parallel to the equator on Jupiter's surface, which is caused by the atmospheric circulation on Jupiter. The stripes are different in width and color, such as light yellow, light green and brown, and their positions have changed a little. This is really a good observation target.

In Jupiter's southern hemisphere, about 20 degrees south latitude, there is a famous great red spot, which is oval in shape and easy to identify. No one knows when the Great Red Spot began. We only know that the telescope was discovered when we first observed Jupiter. It has existed for 400 years, with little change in shape and some changes in size, reaching 40,000 kilometers at the longest, and the width from north to south has remained above 1 10,000 kilometers. The color of the Great Red Spot can be said to vary greatly, sometimes bright, sometimes dim, sometimes slightly brown, sometimes light rose, sometimes even bright red, and so on. In this way, the size, shape, color and its changes of the Great Red Spot will definitely be included in your observation plan. There are the same requirements, such as taking photos, keeping the position and proportion as good as possible, and taking notes.

Jupiter is an outer planet, and the best time to observe it is a period of time before and after Jupiter hits the sun, which can last for several months.

Jupiter's four largest satellites are relatively easy to observe. At first, the Italian astronomer Galileo discovered them with a very simple telescope. The period of these four-particle satellites orbiting Jupiter is:

Io: 1.77 days

Europa: 3.55 days

Ganymede: 7. 16 days

Callisto: 16.70 days

So, be a little patient. If we are separated by two or three hours, we will see that the positions of the four sanitary objects on both sides of Jupiter have changed. These things happen at a distance of 700 million to 800 million kilometers. How interesting!

It is particularly interesting that from the earth, some of these four satellites sometimes pass through the surface of Jupiter, which is called the transit of Jupiter. At this time, the satellite is invisible, but its shadow on the surface of Jupiter is visible; Sometimes a satellite enters the shadow of Jupiter and a satellite eclipse occurs, which is a bit like the moon entering the shadow of the earth and an eclipse occurs; Sometimes a satellite simply walks behind Jupiter and so on. So, sometimes you can see four satellites, sometimes you can only see three or even two, and their positions are always changing.

These interesting phenomena should be the objects you often observe. You can shoot the video in AVI format with a camera and post-stack it, so you can get a very clear picture. You can also take pictures every once in a while to get their running images!

Observe Saturn

Saturn is the farthest planet visible to the naked eye, with a distance of about 65.438+0.4 billion kilometers. When observed with a small telescope, it is undoubtedly the easiest to see its beautiful light ring. Because the relative position of Saturn's ring plane and our line of sight has been changing, the shape of Saturn's ring we see is changing constantly, once every 29.5 years. Observing Saturn with a small telescope can focus on the size, direction and shape of its ring and record it with a camera.

Among Saturn's many satellites, Titan is the largest, with a diameter of over 5,000 kilometers. Because Saturn is far from the sun and Titan is not so bright, you can try to search with your own small telescope.

Observe comets

Comets are an interesting observation object, especially bright long-tailed comets. Comets can be divided into two categories: periodic comets and aperiodic comets. The appearance and observability of aperiodic comets depend on the calculations and reports of the observatory or related parties. Periodic comets are divided into long-period comets with a period of more than 200 years and short-period comets with a period of less than 200 years. No matter how long the period is, it is generally necessary to arrange your own observations according to the forecast of the Observatory.

The observation of comets should pay attention to the following aspects:

Determination of comet position: When a comet appears in the starry sky, its position changes constantly, even faster. We can record the position of comets by drawing pictures, at least one position a day, and more positions a day if necessary. Of course, it is essential to prepare a detailed map in advance. Print out the local star map with skymap 10.0.0!

Observation of the shape of comet: When the comet is far away from the sun, it is just a fuzzy spot. As we get closer and closer to the sun, the nucleus of the comet first becomes blurred, giving birth to a comet, and then forms a tail, ranging from one to several, which gradually increases, becomes longer and brighter. In this way, it has become the most striking celestial body in the starry sky. When it is far away from the sun, the above phenomenon will be reversed. First, the tail will become black, short and small. At the same time, the tail will shrink, and then it will become a fuzzy spotted object. When observing comets, we should carefully record all these situations and pay attention to their instantaneous changes at any time.

Observation of comet brightness: While the overall shape of comet changes, its total brightness also changes. Theoretically, the brightness of each part of a comet, that is, the nucleus and the coma (both called the coma head) should be separated. In fact, the nucleus is often indistinguishable from the tail, and it is very difficult to estimate the brightness of the tail. So just estimate the brightness of the comet's head. We can find a star near Huitou that is almost as bright as Huitou, and the brightness can be roughly estimated.

Observe meteors

The twinkling meteor in the starry sky is one of the astronomical phenomena we can occasionally see. Meteors can be roughly divided into two categories, one is occasional meteors, and the other is meteors in meteor showers.

Occasional meteor refers to a meteor with irregular appearance time and orientation, which is the appearance of a single meteor. At night, about 10 meteors can be observed every hour on average. Generally, there are more meteors observed in the latter half of the night, and they are brighter than the latter half of the night. The number of meteors is relatively concentrated, and they all seem to come from the same point in the sky in all directions. This is called meteor shower. That "same point" is called the radiation point. What constellation is the radiation point in? For example, in Leo, it is said that this is the Leonid meteor shower. Every meteor shower occurs at a certain time every year, but the number of meteors radiated each year is not the same, but changes periodically.

Whether observing occasional meteors or meteors in meteor showers, we need to do some preparatory work, including: choosing suitable observation sites, mainly avoiding lights and tall buildings; Arrange suitable semi-reclining seats. If you plan to observe for more than a few hours, prepare some warm clothes, mosquito repellent drugs and even necessary food. Prepare the conventional tools needed for observation, such as star map, flashlight, clock, camera, tripod, etc. , and record book.

In the notebook, all the items to be recorded should be written in advance, so as to quickly and accurately record: the brightness (expressed in magnitude) and color of meteors, the appearance and disappearance points of meteors in the starry sky, the speed at which meteors cross the sky quickly or slowly, whether there are traces left after the meteors disappear, and so on. If two people cooperate to observe, it is ideal, especially when observing meteor showers. One person can be responsible for observing and dictating the observed ground conditions, while the other person is responsible for recording and communicating with each other after a period of time. Of course, if conditions permit, tracking or fixed-point shooting can also be carried out.