A day on Mercury is 1 year. And the day lasts longer than a year. Sidereal and sunny days
> > Day on Mercury
- the first planet in the solar system. Description of the influence of the orbit, rotation and distance from the Sun, the day of Mercury from a photo of the planet.
Mercury- an example of a planet in the solar system that loves to go to extremes. This is the planet closest to our star, which is forced to experience strong temperature fluctuations. Moreover, while the illuminated side suffers from incandescence, the dark one freezes to critical levels. Therefore, it is not surprising that the day of Mercury does not fit into the standards.
How long is a day on Mercury
The situation with Mercury's diurnal cycle does seem strange. A year spans 88 days, but a slow rotation doubles the day! If you were on the surface, you would watch the sunrise/sunset for 176 days!
Distance and orbital period
This is not only the first planet from the Sun, but also the owner of the most eccentric orbit. If the average distance extends to 57,909,050 km, then at perihelion it approaches 46 million km, and at aphelion it moves off 70 million km.
Due to its proximity, the planet has the fastest orbital period, which varies depending on the position in the orbit. Moves fastest at short range and slows down at a distance. The average speed orbital index is 47322 km/s.
The researchers thought that Mercury repeats the situation of the Earth's Moon and always turned to the Sun on one side. But radar measurements in 1965 made it clear that the axial rotation is much slower.
Sidereal and sunny days
We now know that the resonance of axial and orbital rotation is 3:2. That is, there are 3 revolutions per 2 orbits. With a speed mark of 10.892 km / h, one revolution around the axis takes 58.646 days.
But let's be more precise. Rapid orbital velocity and slow sidereal rotation make it so that a day on Mercury lasts 176 days. Then the ratio is 1:2. Only the polar regions do not fit into this rule. For example, the crater on the north polar cap is always in shadow. There, the temperature mark is low, so it allows you to save ice reserves.
In November 2012, the assumptions were confirmed when MESSENGER used a spectrometer and looked at ice and organic molecules.
Yes, add to all the oddities the fact that a day on Mercury spans as much as 2 years.
Here on Earth, we tend to take time for granted, never thinking that the step in which we measure it is rather relative.
For example, how we measure our days and years is the actual result of our planet's distance from the Sun, the time it takes to orbit it, and rotate around its own axis. The same is true for other planets in our solar system. While we earthlings calculate a day in 24 hours from dawn to dusk, the length of one day on another planet is significantly different. In some cases, it is very short, while in others, it can last more than a year.
Day on Mercury:
Mercury is the closest planet to our Sun, ranging from 46,001,200 km at perihelion (the closest distance to the Sun) to 69,816,900 km at aphelion (farthest). Mercury rotates on its axis in 58.646 Earth days, which means that a day on Mercury takes about 58 Earth days from dawn to dusk.
However, it takes Mercury only 87,969 Earth days to go around the Sun once (in other words, the orbital period). This means that a year on Mercury is equivalent to approximately 88 Earth days, which in turn means that one year on Mercury lasts 1.5 Mercury days. Moreover, the northern polar regions of Mercury are constantly in shadow.
This is due to its 0.034° axial tilt (Earth's is 23.4° by comparison), meaning that Mercury does not experience extreme seasonal changes where days and nights can last for months, depending on the season. It is always dark at the poles of Mercury.
Day on Venus:
Also known as Earth's twin, Venus is the second closest planet to our Sun, ranging from 107,477,000 km at perihelion to 108,939,000 km at aphelion. Unfortunately, Venus is also the slowest planet, this fact is obvious when you look at its poles. Whereas the planets in the solar system experienced flattening at the poles due to rotational speed, Venus did not survive it.
Venus rotates at only 6.5 km/h (compared to Earth's rational speed of 1670 km/h), which results in a sidereal rotation period of 243.025 days. Technically, this is minus 243.025 days, since Venus's rotation is retrograde (i.e. rotation in the opposite direction of its orbital path around the Sun).
Nevertheless, Venus still rotates around its axis in 243 Earth days, that is, a lot of days pass between its sunrise and sunset. This may seem strange until you know that one Venusian year is 224.071 Earth days long. Yes, Venus takes 224 days to complete its orbital period, but more than 243 days to go from dawn to dusk.
So one day of Venus is a little more than a Venusian year! It is good that Venus has other similarities with the Earth, but this is clearly not a daily cycle!
Day on Earth:
When we think of a day on Earth, we tend to think it's just 24 hours. In truth, the sidereal period of the Earth's rotation is 23 hours 56 minutes and 4.1 seconds. So one day on Earth is equivalent to 0.997 Earth days. Oddly enough, again, people prefer simplicity when it comes to time management, so we round up.
At the same time, there are differences in the length of one day on the planet depending on the season. Due to the tilt of the earth's axis, the amount of sunlight received in some hemispheres will vary. The most striking cases occur at the poles, where day and night can last for several days and even months, depending on the season.
At the North and South Poles in winter, one night can last up to six months, known as "Polar Night". In summer, the so-called “polar day” will begin at the poles, where the sun does not set for 24 hours. It's actually not as easy as one would like to imagine.
Day on Mars:
In many ways, Mars can also be called Earth's twin. Add seasonal fluctuations and water (albeit in frozen form) to the polar ice cap, and a day on Mars is pretty close to Earth. Mars makes one revolution on its axis in 24 hours. 
37 minutes and 22 seconds. This means that one day on Mars is equivalent to 1.025957 Earth days.
The seasonal cycles on Mars are more similar to ours than on any other planet, due to its 25.19° axial tilt. As a result, Martian days experience similar changes with the Sun rising early and setting late in the summer and vice versa in the winter.
However, seasonal changes last twice as long on Mars because the Red Planet is at a greater distance from the Sun. This results in a Martian year being twice as long as an Earth year - 686.971 Earth days or 668.5991 Martian days or Sol.
Day on Jupiter:
Given the fact that it is the largest planet in the solar system, one would expect a day on Jupiter to be long. But as it turns out, officially a day on Jupiter lasts only 9 hours 55 minutes and 30 seconds, which is less than a third of the length of an Earth day. This is due to the fact that the gas giant has a very high rotational speed of approximately 45,300 km / h. Such a high rotation speed is also one of the reasons why the planet has such violent storms.
Note the use of the word formal. Since Jupiter is not a solid body, its upper atmosphere moves at a different speed than at its equator. Basically, the rotation of Jupiter's polar atmosphere is 5 minutes faster than that of the equatorial atmosphere. Because of this, astronomers use three frames of reference.
System I is used at latitudes from 10°N to 10°S, where its rotation period is 9 hours 50 minutes and 30 seconds. System II applies at all latitudes north and south of them, where the rotation period is 9 hours 55 minutes and 40.6 seconds. System III corresponds to the rotation of the planet's magnetosphere, and this period is used by the IAU and IAG to determine Jupiter's official rotation (i.e. 9 hours 44 minutes and 30 seconds)
So, if you could theoretically stand on the clouds of a gas giant, you would see the Sun rise less than once every 10 hours at any latitude of Jupiter. And in one year on Jupiter, the Sun rises about 10,476 times.
Day on Saturn:
The situation of Saturn is very similar to Jupiter. Despite its large size, the planet has an estimated rotational speed of 35,500 km/h. One sidereal rotation of Saturn takes approximately 10 hours and 33 minutes, making one day on Saturn less than half an Earth day.
The orbital period of Saturn's rotation is equivalent to 10,759.22 Earth days (or 29.45 Earth years), and a year lasts approximately 24,491 Saturn days. However, like Jupiter, Saturn's atmosphere rotates at different speeds depending on latitude, requiring astronomers to use three different frames of reference.
System I covers the equatorial zones of the South Equatorial Pole and the North Equatorial Belt, and has a period of 10 hours and 14 minutes. System II covers all other latitudes of Saturn except for the north and south poles, with a rotation period of 10 hours 38 minutes and 25.4 seconds. System III uses radio emission to measure Saturn's internal rotation rate, which resulted in a rotation period of 10 hours 39 minutes 22.4 seconds.
Using these various systems, scientists have obtained various data from Saturn over the years. For example, data acquired during the 1980s by the Voyager 1 and 2 missions indicated that a day on Saturn is 10 hours 45 minutes and 45 seconds (± 36 seconds).
In 2007 this was revised by researchers at the UCLA Department of Earth, Planetary and Space Sciences, resulting in the current estimate of 10 hours and 33 minutes. Much like Jupiter, the problem with accurate measurements is that different parts rotate at different speeds.
Day on Uranus:
As we approached Uranus, the question of how long a day lasts became more difficult. On the one hand, the planet has a sidereal rotation period of 17 hours 14 minutes and 24 seconds, which is equivalent to 0.71833 Earth days. Thus, we can say that a day on Uranus lasts almost as long as a day on Earth. This would be true were it not for the extreme axial tilt of this gas-ice giant.
With an axial tilt of 97.77°, Uranus essentially orbits the Sun on its side. This means that its north or south faces directly towards the Sun at different times of the orbital period. When it is summer at one pole, the sun will shine there continuously for 42 years. When the same pole is turned away from the Sun (that is, it is winter on Uranus), there will be darkness for 42 years.
Therefore, we can say that one day on Uranus from sunrise to sunset lasts as much as 84 years! In other words, one day on Uranus lasts as long as one year.
Also, as with other gas/ice giants, Uranus rotates faster at certain latitudes. Therefore, while the rotation of the planet at the equator, approximately 60° south latitude, is 17 hours and 14.5 minutes, the visible features of the atmosphere move much faster, making a complete revolution in just 14 hours.
Day on Neptune:
Finally, we have Neptune. Here, too, the measurement of one day is somewhat more complicated. For example, Neptune's sidereal rotation period is approximately 16 hours 6 minutes and 36 seconds (equivalent to 0.6713 Earth days). But due to its gas/ice origin, the planet's poles rotate faster than the equator.
Taking into account that the speed of rotation of the planet's magnetic field is 16.1 hours, the equatorial zone rotates approximately 18 hours. Meanwhile, the polar regions rotate for 12 hours. This differential rotation is brighter than any other planet in the solar system, resulting in strong latitudinal wind shear.
In addition, the planet's 28.32° axial tilt results in seasonal fluctuations similar to those on Earth and Mars. Neptune's long orbital period means the season lasts for 40 Earth years. But because its axial tilt is comparable to Earth's, the variation in its day length over its long year is not as extreme.
As you can see from this summary of the various planets in our solar system, the length of the day depends entirely on our frame of reference. In addition to that, the seasonal cycle varies, depending on the planet in question, and from where on the planet measurements are made.
The science
Imagine that every day you become older by 3 years. If you lived on the same exoplanet, you would feel it for yourself. Scientists have discovered a planet the size of Earth revolves around its star in just 8.5 hours.
The exoplanet, named Kepler 78b, is 700 light-years from Earth and has one of shortest orbital periods.
Since it is very close to its star, its surface temperature reaches 3000 degrees Kelvin or 2726 degrees Celsius.
In such an environment, the surface of the planet is most likely completely molten, and is huge stormy ocean of very hot lava.
Exoplanets 2013
Finding the planet was not easy. Before finding the superhot exoplanet, scientists examined more than 150,000 stars observed by the Kepler telescope. Researchers are now looking at the telescope's data in hopes of find an earth-sized planet that was potentially habitable.
Scientists have caught the light reflected or emanating from the planet. They determined that Kepler 78b is 40 times closer to its star than Mercury is to our Sun.
In addition, the parent star is relatively young, as it rotates twice as fast as the Sun. This suggests that not much time has passed for her to slow down.
In addition, scientists have found planet KOI 1843.03 with an even shorter orbital period, where the year lasts only 4.25 hours.
It is so close to its star that it is almost entirely made of iron, since anything else would simply be destroyed by incredible tidal forces.
Planets of the solar system: how long is a year there?
The earth is in constant motion: it rotates on its axis (day) and revolves around the sun (year).
A year on Earth is the time it takes for our planet to make a revolution around the Sun, which is just over 365 days.
However, other planets in the solar system revolve around the sun at different speeds.
How long is a year in the solar system?
Mercury - 88 days
Venus - 224.7 days
Earth - 365, 26 days
Mars - 1.88 Earth years
Jupiter - 11.86 Earth years
Saturn - 29.46 Earth years
Uranus - 84 Earth years
Neptune - 164.79 Earth years
Pluto (dwarf planet) - 248.59 Earth years
0.147 Earth
0.056 Earth
0.055 Earth
0.984 Earth
0,38
281.01°
0.106 (geom. albedo)
24.9% sodium
9.5%, A. oxygen
7.0% argon
5.9% helium
5.6%, M. oxygen
5.2% nitrogen
3.6% carbon dioxide
3.4% water
3.2% hydrogen
Mercury in natural color (Image Mariner 10)
Mercury- the closest planet to the Sun in the solar system, revolves around the Sun in 88 Earth days. Mercury is an inner planet because its orbit is closer to the Sun than the main asteroid belt. After depriving Pluto of the status of a planet in 2006, Mercury passed the title of the smallest planet in the solar system. Mercury's apparent magnitude ranges from −2.0 to 5.5, but is not easy to see due to its very small angular distance from the Sun (maximum 28.3°). At high latitudes, the planet can never be seen in the dark night sky: Mercury is always hidden in the morning or evening dawn. The optimal time for observing the planet is morning or evening twilight during periods of its elongations (periods of maximum removal of Mercury from the Sun in the sky, occurring several times a year).
It is convenient to observe Mercury at low latitudes and near the equator: this is due to the fact that the duration of twilight is the shortest there. In middle latitudes, finding Mercury is much more difficult and only during the period of the best elongations, and in high latitudes it is impossible at all.
Relatively little is known about the planet. The Mariner-10 apparatus, which studied Mercury in -1975, managed to map only 40-45% of the surface. In January 2008, the interplanetary station MESSENGER flew past Mercury, which will enter orbit around the planet in 2011.
In terms of its physical characteristics, Mercury resembles the Moon and is heavily cratered. The planet has no natural satellites, but has a very rarefied atmosphere. The planet has a large iron core, which is the source of the magnetic field in its totality, which is 0.1 of the earth's. Mercury's core makes up 70 percent of the planet's total volume. The temperature on the surface of Mercury ranges from 90 to 700 (from −180 to +430 ° C). The solar side heats up much more than the polar regions and the far side of the planet.
Despite the smaller radius, Mercury still surpasses in mass such satellites of the giant planets as Ganymede and Titan.
The astronomical symbol of Mercury is a stylized depiction of the winged helmet of the god Mercury with his caduceus.
History and name
The oldest evidence for the observation of Mercury can be found in Sumerian cuneiform texts dating back to the third millennium BC. e. The planet is named after the god of the Roman pantheon Mercury, an analogue of the Greek Hermes and Babylonian Naboo. The ancient Greeks of the time of Hesiod called Mercury "Στίλβων" (Stilbon, Brilliant). Until the 5th century BC e. the Greeks believed that Mercury, visible in the evening and morning sky, are two different objects. In ancient India, Mercury was called Buddha(बुध) and Roginea. In Chinese, Japanese, Vietnamese and Korean, Mercury is called water star(水星) (in accordance with the concept of the "Five Elements". In Hebrew, the name of Mercury sounds like "Kokhav Hama" (כוכב חמה) ("Solar Planet").
planet movement
Mercury moves around the Sun in a rather strongly elongated elliptical orbit (eccentricity 0.205) at an average distance of 57.91 million km (0.387 AU). At perihelion, Mercury is 45.9 million km from the Sun (0.3 AU), at aphelion - 69.7 million km (0.46 AU) At perihelion, Mercury is more than one and a half times closer to the Sun than at aphelion. The inclination of the orbit to the plane of the ecliptic is 7°. Mercury spends 87.97 days per orbit. The average speed of the planet in orbit is 48 km/s.
For a long time it was believed that Mercury is constantly facing the Sun with the same side, and one revolution around its axis takes the same 87.97 days. Observations of detail on the surface of Mercury, made at the limit of resolution, did not seem to contradict this. This misconception was due to the fact that the most favorable conditions for observing Mercury are repeated through a triple synodic period, that is, 348 Earth days, which is approximately equal to six times the rotation period of Mercury (352 days), therefore, approximately the same surface area was observed at different times planets. On the other hand, some astronomers believed that the Mercury day is approximately equal to the Earth day. The truth was revealed only in the mid-1960s, when the radar of Mercury was carried out.
It turned out that the Mercury sidereal day is equal to 58.65 Earth days, that is, 2/3 of the Mercury year. Such a commensurability of the periods of rotation and revolution of Mercury is a unique phenomenon for the solar system. This is presumably due to the fact that the tidal action of the Sun took away the angular momentum and slowed down the rotation, which was initially faster, until the two periods were connected by an integer ratio. As a result, in one Mercury year, Mercury has time to rotate around its axis by one and a half turns. That is, if at the moment Mercury passes perihelion, a certain point of its surface faces exactly the Sun, then during the next passage of perihelion, exactly the opposite point of the surface will face the Sun, and after another Mercury year, the Sun will again return to the zenith above the first point. As a result, a solar day on Mercury lasts two Mercury years or three Mercury sidereal days.
As a result of such a movement of the planet, “hot longitudes” can be distinguished on it - two opposite meridians, which alternately face the Sun during the passage of perihelion by Mercury, and on which, because of this, it is especially hot even by Mercury standards.
The combination of the movements of the planet gives rise to another unique phenomenon. The speed of rotation of the planet around its axis is practically constant, while the speed of orbital motion is constantly changing. In the segment of the orbit near the perihelion, for about 8 days, the speed of orbital motion exceeds the speed of rotational motion. As a result, the Sun in the sky of Mercury stops, and begins to move in the opposite direction - from west to east. This effect is sometimes called the Joshua effect, after the protagonist of the Book of Joshua from the Bible, who stopped the movement of the Sun (Joshua, x, 12-13). For an observer at longitudes 90° away from the "hot longitudes", the Sun rises (or sets) twice.
It is also interesting that, although Mars and Venus are the closest orbits to Earth, it is Mercury that is the closest planet to Earth most of the time than any other (because others move away to a greater extent without being so “tied” to the Sun).
physical characteristics
Comparative sizes of Mercury, Venus, Earth and Mars
Mercury is the smallest terrestrial planet. Its radius is only 2439.7 ± 1.0 km, smaller than that of Jupiter's moon Ganymede and Saturn's moon Titan. The mass of the planet is 3.3 × 10 23 kg. The average density of Mercury is quite high - 5.43 g / cm³, which is only slightly less than the density of the Earth. Given that the Earth is larger in size, the value of the density of Mercury indicates an increased content of metals in its bowels. The free fall acceleration on Mercury is 3.70 m/s². The second space velocity is 4.3 km/s.
Kuiper Crater (just below center). MESSENGER image
One of the most noticeable details of the surface of Mercury is the Heat Plain (lat. Caloris Planitia). This crater got its name because it is located near one of the "hot longitudes". Its diameter is about 1300 km. Probably, the body, upon impact of which the crater was formed, had a diameter of at least 100 km. The impact was so strong that seismic waves, having passed the entire planet and focused at the opposite point of the surface, led to the formation of a kind of intersected "chaotic" landscape here.
Atmosphere and physical fields
During the flight of the Mariner-10 spacecraft past Mercury, it was established that the planet has an extremely rarefied atmosphere, the pressure of which is 5 × 10 11 times less than the pressure of the earth's atmosphere. Under such conditions, atoms more often collide with the surface of the planet than with each other. It consists of atoms captured from the solar wind or knocked out by the solar wind from the surface - helium, sodium, oxygen, potassium, argon, hydrogen. The average lifetime of an atom in the atmosphere is about 200 days.
Mercury has a magnetic field, the strength of which is 300 times less than the strength of the Earth's magnetic field. The magnetic field of Mercury has a dipole structure and is highly symmetrical, and its axis deviates by only 2 degrees from the axis of rotation of the planet, which imposes a significant limitation on the range of theories explaining its origin.
Research
An image of a portion of the surface of Mercury taken by the MESSENGER spacecraft
Mercury is the least explored terrestrial planet. Only two vehicles were sent for his research. The first was Mariner 10, which flew past Mercury three times in -1975; the maximum approach was 320 km. As a result, several thousand images were obtained, covering approximately 45% of the planet's surface. Further studies from Earth showed the possibility of the existence of water ice in polar craters.
Mercury in art
- In Boris Lyapunov's science fiction short story "Nearest to the Sun" (1956), Soviet cosmonauts land on Mercury and Venus for the first time to study them.
- In Isaac Asimov's story "The Big Sun of Mercury" (a series about Lucky Starr), the action takes place on Mercury.
- Isaac Asimov's stories Runaround and The Dying Night, written in 1941 and 1956 respectively, describe Mercury facing the Sun on one side. At the same time, in the second story, the key to the detective story is built on this fact.
- In the science fiction novel The Flight of the Earth by Francis Karsak, along with the main plot, a scientific station for studying the Sun is described, located at the North Pole of Mercury. Scientists live on a base located in the eternal shadow of deep craters, and observations are made from giant towers constantly illuminated by the luminary.
- In Alan Noorse's science fiction novel Across the Sunny Side, the main characters cross the side of Mercury facing the Sun. The story was written in accordance with the scientific views of its time, when it was assumed that Mercury was constantly facing the Sun on one side.
- In the anime animated series Sailor Moon, the planet is personified by the warrior girl Sailor Mercury, she is Ami Mitsuno. Her attack lies in the power of water and ice.
- In Clifford Simak's science fiction story "Once Upon a Time on Mercury", the main field of action is Mercury, and the energy form of life on it - balls, surpasses humanity by millions of years of development, having long passed the stage of civilization.
Notes
see also
Literature
- Bronstein W. Mercury is the closest to the Sun // Aksenova M.D. Encyclopedia for children. T. 8. Astronomy - M.: Avanta +, 1997. - S. 512-515. - ISBN 5-89501-008-3
- Xanfomality L.V. Unknown Mercury // In the world of science. - 2008. - № 2.
Links
- MESSENGER mission website
- Pictures of Mercury taken by Messenger
- BepiColombo mission section on the JAXA website
- A. Levin. Iron Planet Popular Mechanics #7, 2008
- "The closest" Lenta.ru, October 5, 2009, photographs of Mercury taken by "Messenger"
- “New images of Mercury published” Lenta.ru, November 4, 2009, about the approach on the night of September 29 to 30, 2009 of Messenger and Mercury
- "Mercury: Facts & Figures" NASA. Summary physical characteristics of the planet.
| solar system | |
|---|---|
| See also: |