A star in the east on a morning in July. Which planet is called the "morning star" and why? Features of movement in the sky

In July, the moment of opposition passes a distant dwarf planet Pluto, Mars conjunction with the Sun will take place, and Mercury reaches evening elongation (not visible in middle and northern latitudes). Venus can be found in the morning above the eastern horizon, as well as in the afternoon in a clear cloudless sky. Jupiter shines in the evening sky in the constellation Virgo. Uranus And Neptune can be found at night in the constellations of Pisces and Aquarius.

Moon will approach the indicated planets: on July 1 in the evening with a lunar phase of 0.54 - with Jupiter, on July 07 at night near the full moon - with Saturn, on July 14 in the morning with a lunar phase of 0.79 - with Neptune, on July 17 in the morning with a lunar phase of 0.48 - with Uranus, on July 20 in the afternoon with a lunar phase of 0.13 - with Venus, on July 23 in the afternoon with a new moon - with Mars, on July 25 in the evening with a lunar phase of 0.05 - with Mercury, on July 28 in the evening with a lunar phase of 0.30 - with Jupiter . For observations, it is better to choose nights when the Moon near the full phases does not pass near the observed planet.

The visibility conditions are given for the middle latitudes of Russia (about 56°N). For cities to the north and south, celestial bodies will be located at the indicated time, respectively, slightly lower or higher (by the difference in latitudes) relative to their places in the sky of Bratsk. To clarify the local conditions for the visibility of planets, use planetarium programs.

MERCURY moves in the same direction as the Sun through the constellations of Gemini, Cancer and Leo. The elongation of Mercury on July 30 reaches a maximum of 27 degrees east of the Sun, but it will be possible to observe Mercury against the background of the evening dawn only from the southern latitudes of Russia during this period, it is not visible in the middle and northern latitudes. The apparent size of Mercury increases from 5 to 7 arc seconds with decreasing brightness from -1.2m to +0.4m. The phase of Mercury decreases from 0.9 to 0.45. Successful observations of Mercury during periods of visibility require binoculars, an open horizon, and a clear twilight sky.

VENUS moves in the same direction as the Sun in the constellation Taurus. The angular distance (elongation) from the Sun is reduced from 43 to 38 degrees in a month. The planet is visible at about 2 o'clock in the twilight morning at the eastern horizon. The angular dimensions of the planet's disk are reduced from 17 to 14 arcseconds. The phase of the planet increases from 0.63 to 0.74 with decreasing brightness from -4.3m to -4.1m. Such a bright brilliance and angular distance from the Sun make it possible to observe Venus during the day with the naked eye (assuming a transparent clear blue sky). A half-disk is visible through the telescope, gradually turning into an oval with a simultaneous decrease in the size of the planet, because. the distance between Venus and Earth is increasing.

Venus in the morning sky July 2017

MARS has a direct movement in the constellation of Gemini, is not visible the whole month, because. On July 27, there is a conjunction with the Sun. The brightness of the planet adheres to the value +1.7m, and the angular size is about 3".

For observations, a telescope with a lens diameter of 60-90 mm is required. To observe the details on the disk of Mars, the moment of opposition, which occurs once every two years, is best suited. At other periods, Mars appears in a telescope as a tiny reddish disk with no details. The next opposition of Mars will occur on July 27, 2018 (Great Opposition!).

JUPITER moves in the same direction as the Sun in the constellation Virgo. The gas giant is visible for about 2 hours at the beginning of the month, reducing visibility in the evening sky to 1 hour by the end of the period under consideration. The angular diameter of the giant planet in the sky decreases from 37 to 34 arc seconds, and the brightness from -1.9m to -1.7m.

Position of Jupiter in the evening twilight sky of July 2017

Four bright satellites of the giant are visible through binoculars - due to the rapid orbital movement, they noticeably change their position relative to each other and Jupiter during one night (the configurations of Io, Europa, Ganymede and Callisto can be found in astronomical calendars or in planetarium programs).

The telescope distinguishes bands (northern and southern equatorial bands), shadows from satellites periodically pass across the planet’s disk, as well as the famous huge oval cyclone BKP (Great Red Spot), which makes a complete revolution along with the planet’s atmosphere in 9.5 hours. The current longitude of the BKP can be found at http://jupos.privat.t-online.de/rGrs.htm. The BKP appears about 2 hours before passing through the meridian and disappears after 2 hours (goes beyond the disk).

The moments of the passage of the BKP through the central meridian of Jupiter in JULY 2017 (universal time UT)
To get the time for Bratsk, you need to add 8 hours to UTC

Current longitude BKP 270°

SATURN moving backwards through the constellation Ophiuchus. The planet is observed all the dark time of the day (June 15, Saturn passed the moment of its opposition to the Sun) low above the horizon. The angular diameter of Saturn decreases from 18 to 17 seconds of arc at magnitude +0.3m. The best period in 2017 for observations of the ringed planet continues, which will last until August.

In a small telescope, the ring around the planet and the satellite Titan (+8m) are clearly distinguished. The visible dimensions of the planet's ring are about 40x18 arc seconds. At present, the rings of the planet are open at 26 ° and the north pole of the gas giant is illuminated by the Sun.

Position of Saturn in the evening sky in July 2017

URANUS moves in the same direction as the Sun in the constellation Pisces near *omicron Pisces. The duration of morning visibility by the end of the month reaches 5 hours. The brightness of the planet adheres to the value +5.7m at an angular diameter of 3".

During opposition periods, Uranus can be observed with the naked eye in a clear transparent sky, in the absence of illumination from the Moon (near the new moon) and away from city lights. In a 150-mm telescope with a magnification of 80x and higher, you can see a greenish disk ("pea") of the planet. The satellites of Uranus have a brightness weaker than +13m.

NEPTUNE moves backward in the constellation Aquarius near *lamda (3.7m), moving towards the moment of its opposition on September 5th. The planet can be found low above the horizon, where it is visible in optical instruments around 3-6 am. The brightness of the planet is +7.8m magnitude and almost does not differ from the surrounding stars.

Binoculars or a telescope using star charts and a clear, transparent and moonless sky will help you find Neptune during periods of visibility. To view the disk of the planet, you need a 200-mm telescope with a magnification of 100 times or more (with a transparent sky). The satellites of Neptune have a brightness weaker than +13m.

The path of Neptune among the stars in 2017 (search map)© Fyodor Sharov's blog

PLUTO moves back against the background of the constellation Sagittarius and is at a distance of 32.347 AU. from the earth. On July 10, the moment of its opposition to the Sun passes. The brightness of the planet is +14.8m magnitude and does not differ from the surrounding stars.

The morning sky brightens quite quickly with the dawn, and the stars disappear from it one by one. Only one luminary remains visible longer than the others. This is Venus, the planet is the morning star. It is many times brighter than Sirius for an earthly observer and is second only to the Moon in the night sky in this sense.

Features of movement in the sky

Today, almost everyone knows which planet is called the "morning star" and why. The beautiful Venus appears in the sky shortly before sunrise. After dawn, it remains visible longer than other luminaries due to its brightness. The most vigilant observers can see a white dot in the sky for several hours after sunrise - this is the planet "morning star".

Venus also appears before sunset. In this case, it is called the evening star. As the sun dips below the horizon, the planet gets brighter. You can observe it for several hours, then Venus sets. It doesn't show up in the middle of the night.

Second from the Sun

The answer to the question “which planet is called the morning star” could be different if Venus was in a remote part of the solar system. A similar nickname was given to the cosmic body not only because of the peculiarities of its movement through the sky, but also because of its brightness. The latter, in turn, is the result of the position of the planet relative to the Earth and the Sun.

Venus is our neighbor. At the same time, it is the second planet from the Sun, almost identical in size to the Earth. Venus is the only one of its kind that comes so close to our home (the minimum distance is 40 million kilometers). These factors make it possible to admire it without the help of telescopes or binoculars.

Things of bygone days

In ancient times, the answers to the question of which planet is called the morning star and which planet is called the evening star did not coincide. It was not immediately noticed that the luminaries, anticipating their appearance, sunrise and sunset, are one and the same cosmic body. Ancient astronomers carefully watched these stars, poets wrote legends about them. After some time, careful observation paid off. The discovery is attributed to Pythagoras and dates back to 570-500. BC e. The scientist suggested that the planet, known as the morning star, is also the evening star. Since then, we know a lot about Venus.

mysterious planet

The cosmic body, named after, as if justifying its name, excited the minds of astronomers for a long time, but did not allow them to get closer to unraveling its secrets. Almost until the 60s of the last century, Venus was considered a twin of the Earth, there was talk about the possibility of discovering life on it. Much of this was facilitated by the discovery of her atmosphere. The discovery was made in 1761 by M. V. Lomonosov.

Improvements in technology and research methods have made it possible to study Venus in more detail. It turned out that the dense atmosphere of the planet mainly consists of carbon dioxide. Its surface is always hidden from observation by a layer of clouds, probably consisting of sulfuric acid. The temperature on Venus exceeds all thresholds conceivable for a person: it reaches 450 ºС. This and other features of the planet became the reason for the curtailment of all theories that suggested life on a cosmic body close to us.

gas giant

However, the question “which planet is called the morning star” has another answer, and more than one. Jupiter is sometimes referred to by this name. The gas giant, although it is at a decent distance from our planet and is located farther from Mars from the Sun, follows Venus in brightness in the sky. Often they can be seen close to each other. More recently, in early July 2015, Venus and Jupiter were visible as a beautiful double star.

It should be noted that the gas giant is quite often available for observation throughout the night. Therefore, it cannot be called as suitable a candidate for the role of the morning star as Venus. However, this does not make it less interesting and beautiful object of the sky.

closest to the sun

There is another morning star. The planet other than Venus and Jupiter so designated is Mercury. The closest cosmic body to the Sun is named after the Roman herald of the gods for its speed. Either ahead of or catching up with the daylight, for an earthly observer, Mercury is visible alternately in the evening and morning hours. This makes him related to Venus. The small planet is therefore also historically called the morning and evening star.

Elusive

Features of the movement of Mercury and proximity to the Sun make it difficult to observe. The ideal places for this are low latitudes and the equatorial region. Mercury is best visible during the period of maximum distance from the Sun (this time is called elongation). In mid-latitudes, the probability of seeing falls sharply. This is possible only during the best elongations. For observers from high latitudes, Mercury is inaccessible.

The visibility of the planet is cyclical. The period is from 3.5 to 4.5 months. If Mercury, moving in orbit, overtakes the daylight clockwise for an earthly observer, then at this time it can be seen in the morning hours. When it is behind the Sun, there is a chance to observe the fastest planet in the system in the evening. Each time Mercury is visible for about ten days.

Thus, this planet is called the morning star for good reason. However, this “nickname” of Mercury is not known to everyone for obvious reasons: to see it in the sky is a rare success due to its proximity to the daylight, as well as its relatively small size.

So which planet is called the morning star? With all certainty, we can say that such a question implies the answer "Venus", less often "Mercury" and almost never, although this is possible, "Jupiter". The planet, named after the goddess of love, due to its proximity to the Earth and high reflectivity, and hence brightness, is more noticeable to an observer inexperienced in astronomy, and therefore will always firmly take the place of the most beautiful morning star for most.

In March, 3 planets visible to the naked eye can be observed in the morning sky: UPITE R (m= -2.1) * , SATURN(m= +0.7) and MARS(m=+1.0). They rise before dawn and are visible not far from each other, being in the same constellation - in the constellation of Sagittarius, very low above the horizon. Joins them at the end of the month MERCURY.

MARS appears above the horizon more than two hours before sunrise. At the beginning of the month, he rises first among these planets - at six in the morning and as a yellowish star is visible before dawn very low above the horizon in the southeast at an altitude of 7 degrees. At the end of the month it rises at five in the morning.

JUPITER rises two hours before sunrise. At the beginning of the month, it rises half an hour later than Mars, at the end of the month, Jupiter is the first among these planets to appear above the horizon and rise 20 minutes earlier than Mars. Visible in the southeast very low on the horizon as a very bright star.

March 20 at 11:23- Mars conjunct Jupiter. Mars will be visible 0.7 degrees south of Jupiter.

SATURN rises last. At the beginning of the month, it rises an hour later than Mars, at the end of the month they appear above the horizon almost simultaneously. Visible below and to the left of bright Jupiter. February 17 passes from the constellation of Sagittarius to the constellation of Capricorn.

March 31 at 15:59- Conjunction of Mars with Saturn. Mars will be visible 0.9 degrees south of Saturn.

At MERCURY(m= +0.7) morning visibility, but it rises at dawn and is not visible against the background of dawn. On March 24, it is at the maximum angular distance from the Sun - 28 degrees, but it rises 30-40 minutes before sunrise and is also not visible against the bright sky. Moves in the constellation Aquarius.

* Magnitude “m” is given in parentheses. Magnitudes express the brightness of a planet or star (the brighter the star or planet, the smaller its magnitude).

CONSTELLATIONS IN THE MORNING SKY

Constellations visible above the southern horizon snakes, Ophiuchus, Libra and at the very horizon of the constellation scorpio And Sagittarius, some of which are below the horizon.

Starry sky above the southern horizon March 15 at 06:30

Above the eastern horizon, summer constellations rise high into the sky: Lyra with bright Vega , Swan with Deneb , Eagle with Altair . And the smallest constellations in area: Arrow, Delphi n and Little Horse. At the very horizon, the autumn constellations rise: Pegasus and Andromeda .

Starry sky above the eastern horizon March 15 at 06:30

In the west, the spring constellations set beyond the horizon: Lion with Regulus, Virgo with Spica, Small Lion and high above the horizon shines the brightest star of the northern hemisphere - Arcturus from the constellation Bootes . Seen in the northwest Big Bucket constellations Ursa Major .

Starry sky over the western horizon March 15 at 06:30

In the north, a bright star shines low on the horizon Chapel from the constellation Charioteer. Above the north point "hangs" Polar star from Ursa Minor . Seen in the northwest Big Bucket constellations Ursa Major .

So, and now about the heavenly dates of Venus ...

Jupiter will enter the morning sky in the second half of December, shining low on the southeastern horizon in the constellation of Ophiuchus. On December 22, Mercury will pass very close to it (the distance from the Sun will be 20 degrees). Venus at this time will still be in the constellation of Libra.

On January 6, 2019, the morning elongation of Venus (-4.7m; El=46°57’) will occur in the constellation of Libra

The period of close visibility of Jupiter and Venus will occur in the second half of January 2019, when the distance between the luminaries will be less than 6 °, and they can be observed in the field of view of ordinary binoculars! On January 22, two bright planets will converge in the sky to 2.5 degrees - Venus will shine over Jupiter over the southeastern horizon in the constellation Ophiuchus.

Such connections are common, since the planets and the Moon move in the celestial sphere along one "broad highway" encircling the sky, called the plane of the ecliptic.

Clear skies and successful observations of Venus in the morning!

Visibility and position of the planets in the sky during the month.

June, the "brightest" month, does not really favor astronomical observations. If in the south the nights are simply short, then in temperate latitudes the period of white nights begins at all. The bright planets, the Sun and the Moon remain almost the only available objects for observation.

All four bright planets can be seen in the June sky this year. Jupiter is visible in the first half of the month in the evenings in the west, beautiful Venus throughout June - in the mornings in the east. In the evenings in the south and southwest you can observe Mars and Saturn. These two planets are the most convenient for observations in June.

But we will begin our review with Mercury, the planet closest to the Sun.

Mercury

Mercury minutes before its occultation by the Moon in the daytime sky of Sochi on June 26, 2014.

At the beginning of June, the period of evening visibility of Mercury ends. The planet closest to the Sun could be observed in the first days of the month low in the northwest for about half an hour after sunset, and only in the south, outside the zone of white nights. Almost all of June, Mercury is in the sky near our day star and therefore is not available for observation. On June 19, the planet enters into inferior conjunction with the Sun, that is, it will pass between the Earth and the Sun, after which it passes into the morning sky.

On June 26, Mercury, being in the sky only 10 ° from the Sun, will be covered by the Moon. This interesting phenomenon will be observed in the Atlantic, America and Europe, in particular, in the Crimea and on the Black Sea coast of the Caucasus. The occultation will begin around 5 pm when the Moon and Sun are in the western sky.

The brightness of Mercury will be about 2.5m, which, in principle, allows you to see the planet against a blue sky background in a good amateur telescope. However, be extremely careful! Don't forget that plating will occur near the Sun and the star's rays can accidentally hit the eyepiece and damage your eyesight! We would recommend observing this phenomenon only to experienced amateurs. For our part, we will try to publish interesting photos of the coverage, if any appear on the Internet.

Venus

Have you seen Venus yet this summer? In early June, the Morning Star rises about an hour before sunrise over the eastern (more precisely, over the northeast-east) part of the horizon.

However, the period of visibility of Venus is rather arbitrary: in Ukraine, in the Crimea and in the Caucasus, the planet is currently visible for almost 1.5 hours, appearing in a dark sky. At the latitude of Moscow, the period of visibility of Venus does not reach even up to an hour. Even further north, in view of the white nights, even less. At the same time, the planet rises against the background of the dawn. But you can still find it in St. Petersburg because of the great brightness of the planet (during June it stays around -4m). Note that at the time of rising, Venus, which is actually white, can be red, orange and deep yellow, confusing the beginner. In this case, we are faced with the typical reddening of space objects near the horizon due to dust floating in the Earth's atmosphere.

What will happen in the sky with Venus during the month? I must say that throughout June the planet has a direct movement (that is, it moves against the background of stars in the same direction as the Sun, from west to east), moving along the constellation Aries. Venus gradually catches up with the star in the sky, but in June the distance is reduced slightly - from 37 to 30 degrees. The position of the planet's rising point is slightly shifted to the north.

30 degrees from the Sun is a very comfortable distance to observe such a bright planet in the predawn sky. However, in temperate latitudes and in the north, white nights intervene, which somewhat complicates its observation. But even in this case, as we said above, Venus can be seen quite easily with the naked eye, not to mention observations through a telescope or binoculars. Before sunrise, the planet has time to rise into the sky at the latitude of Moscow by about 10 °, at the latitude of Sochi - by 15 ° above the horizon.

Perhaps it is after sunrise that the June observations of Venus through a telescope will be most interesting and productive. Already in the morning, the planet rises high enough above the horizon that atmospheric turbulence does not greatly distort the picture in the eyepiece, and the low contrast between the dazzling white Venus and the blue background of the sky often allows you to notice much more detail in the planet's cloud cover than usual.

During June, the apparent dimensions decrease from 14 to 12 arc seconds, and the phase increases from 0.77 to 0.86. (The planet, following a smaller orbit, overtook the Earth and is now moving away from it, and in a few months will hide behind the Sun.)

Venus and the Moon in the morning sky on June 24th. The dimensions of the moon are increased by 4 times for clarity.

I must say that during the day it is quite possible to see Venus with the naked eye. To do this, it is enough to isolate oneself from the bright Sun and consider a section of the sky 30 ° to the right of the star. In the first half of the day, Venus will be slightly above the Sun, in the second, respectively, below. Finally, on June 24, an excellent reference point for finding Venus, both before sunrise and in the daytime sky, will be the “aging” Moon, whose narrow crescent will approach the planet up to 3.5 °.

Mars

It's been 2 months since Mars' opposition in April. The brilliance and apparent size of the Red Planet have decreased significantly and continue to decrease rapidly. However, in June, Mars remains one of the most visible celestial bodies during the evening and night hours.

All month the planet is in the constellation Virgo, moving against the background of the stars in the same direction as the Sun and gradually approaching Spica, the main star of the constellation Virgo. Mars appears in the evening twilight in the southwest at 25 ° above the horizon (at the latitude of Moscow). The planet can be distinguished from stars by its characteristic pinkish color and even radiance (stars tend to twinkle noticeably).

At the beginning of June, the visibility of Mars is about 4 hours, at the end - only 2 hours. The brightness of the planet decreases from -0.5m to 0.0m, the diameter of the visible disk is from 11.9″ to 9.5″. In a good amateur telescope with a lens of 120 mm or higher, a lot of interesting details can be found on the planet's disk - polar caps, dark and light areas, areas with various shades of yellow, red and even blue. And in modern digital images, the Mysterious Planet still appears very impressive today.

The planet Mars, photographed on May 7, 2014. The image clearly shows the northern polar cap, dark areas of the Chryse region and bright cirrus clouds.

Jupiter

Saturn, Moon, Mars and Jupiter on the evening of June 8th. Jupiter in the evenings in the first half of June is visible in the rays of the evening dawn low in the northwest.

Shining in our sky for almost a year, Jupiter ends the period of evening visibility in June. The planet moves in the same direction as the Sun, but being farther from us than the daylight, it moves against the background of stars slower than the Sun. At the end of July, the Sun will catch up with Jupiter and the planet will again, like last year, move to the evening sky, where on August 18 there will be a remarkable approach to Venus.

In the first half of June, Jupiter can be observed for about 2 hours in the evening twilight in the northwest (90 ° to the right of Mars); at the end of the month, the planet actually hides in the rays of the Sun.

Despite the fact that Jupiter is currently located near the most distant point of its orbit from the Earth, the planet is so large that its brightness and size have not decreased significantly compared to the winter period. In June, Jupiter's brightness is around -1.9m, and the diameter of the visible disk is about 32″. The planet is still perfectly visible even in small telescopes; its observations will be hampered to a much greater extent by the low position above the horizon and the bright background of the sky in temperate latitudes than by the distance from the Earth.

Saturn

The approach of the Moon and Saturn at midnight on June 11, 2014. Please note that Saturn, Mars and the bright star Arcturus form an almost isosceles triangle in the sky in June.

The position of Saturn in the sky makes this planet the most convenient to observe in June 2014. Being in the constellation of Libra all month, the ringed giant appears at dusk in the south at an altitude of 15-20 degrees above the horizon, depending on the latitude of observation. In the south of Russia, Ukraine, Kazakhstan, the visibility of Saturn will be about 6 hours, in temperate latitudes the planet will be visible throughout the short night.

In terms of brightness (0.4m), Saturn is comparable to the brightest stars, but this may not be enough for a beginner to confidently identify the planet in the bright June night sky. Especially for beginner astronomy lovers, we will inform you that in the evening Saturn can be found 30 ° (about 3-4 fists of an outstretched hand) east of the reddish and brighter Mars. When searching, it is important not to confuse Mars with the star Arcturus, which is also reddish and has about the same brilliance as Mars. In general, Mars, Arcturus and Saturn form an isosceles triangle in the June sky, at the base of which are two planets. The easiest way to find the planet will be on the night of June 10-11. At this time, next to Saturn (only 1.5 ° south of the planet), the Moon will be in a phase close to the full moon.

The color of Saturn is yellow. Already in a small telescope one can see the disk of the planet flattened towards the poles and the luxurious rings of the planet opened at 20 °. The visible dimensions of the planet are 18″, and the rings are 40×15″. In a telescope with a lens of 100 mm or more, you can try to see the Cassini Gap in the rings of the planet. Even with smaller instruments, Saturn's largest moon Titan can be seen as an 8.4m star.

Uranus and Neptune

The last planets in our review are Uranus and Neptune. The distant giants are too faint to be observed with the naked eye (only Uranus at opposition can be seen at the limit of visibility on a moonless night). And in most amateur telescopes, they look at best like tiny greenish-blue discs without any details.

Now both Uranus and Neptune are in the morning sky in the constellations of Pisces and Aquarius, respectively. The visibility of Uranus in June is about 1 hour at the beginning of the month and rises to 2 hours at the end. The brightness of the planet is 6.0m, the apparent size of the planet is 3.4″; to see the disk, you will need a telescope with a lens of at least 80 mm and a magnification of 80× or higher. Note that it is almost impossible to observe the planet north of Moscow due to the white nights.

To an even greater extent, the latter also applies to Neptune, which, even if it rises almost an hour earlier than Uranus, has a brightness of only 8m. Like Uranus, Neptune moves across the sky in the same direction as the Sun. It can be found near the star Sigma Aquarii (magnitude 4.8m). To see the disk of the planet, you need a more serious tool: a telescope with a 100-120 mm lens and a magnification of over 100 ×.

We repeat that the search and observation of these planets, due to their remoteness from the Earth, have only cognitive value for amateurs at best.

Let's summarize. In June, all the planets are visible in the sky, except for Mercury, which enters inferior conjunction with the Sun on the 19th. The most favorable conditions will develop for the observation of Saturn and Mars. These two planets appear in the sky at dusk in the south and southwest, respectively. The planets are located at an altitude of about 20 ° above the horizon and are visible for 6 and 4 hours, respectively. In temperate latitudes, Saturn can be observed throughout the short night.

Venus is visible in the east in the morning for about an hour before sunrise. The brilliance of the planet allows you to observe it both during the day, both with a telescope and with the naked eye. Jupiter can still be seen in the evenings in the northwest, in the rays of the evening dawn. Its visibility is rapidly decreasing, and at the end of the month the planet will hide in the rays of the Sun.