The storms over the planet Jupiter, meteors and meteor targets, the rising of the impressive Pegasus group, and other stars and various objects that you can see in the coming weeks in the sky. A detailed guide for amateur astronomers
Ofer Yaron, Galileo
When we look at the night sky from a fairly dark place and on a cloudless night, many points of light can be noticed. Most of the points are stars - bodies that emit radiation similar to our sun - belonging to our galaxy, the Milky Way. In addition to the stars, we sometimes also see one or more planets. These belong to our solar system, are much closer to us than the distant stars, and do not produce their own light but reflect sunlight from their surface. By the way, a method to differentiate between a point of light that is a star and a point of light that is a planet (when looking with the naked eye) is to focus on the point for a few seconds.
If you detect a twinkle (or flicker), there is probably a distant star in front of us. If the light looks steady, it's probably a planet. The reason for this is that a star, due to its enormous distance from us, is a point source of light, while a non-point flux of radiation comes from a planet. Because of the refraction of the light rays in the atmosphere and the dynamism of the atmosphere, the radiation from the star is sometimes deflected from our eyes and then returns, and thus a twinkling effect is obtained. Convincing proof of these differences is obtained by observing through a telescope. Even if you look at high magnification, a star will always appear pointy (brighter or less bright, except for individual stars observed from large research telescopes and with the help of special observation devices), while observing a planet will reveal a disk appearance, which allows you to distinguish its shape and dimensions.
In this article I will briefly describe the constellations and other bodies visible in the sky from the latitude of Israel in the evening hours of this season, the early summer months. I will also briefly explain what meteors are and how meteor targets are formed at fixed times throughout the year thanks to the presence of remnants of comets, which orbit the sun and come close to the orbit of the earth around it. In conclusion, a few words will be said about Tzedek and a new friend who joined the big and familiar red spot.
My name is summer
On June 21, the summer solstice - the longest day in the Northern Hemisphere - we officially marked the beginning of summer. The collection of bright stars that most characterize the coming of summer are those that make up the great summer triangle: Vega in the harp group (the legendary musical instrument that Orpheus played, which was set in the sky after his death, for the pleasure of the listening gods), Deneb - the swan's tail , and Altair in the Nesher group. In the evening hours of the height of summer (August-September) there is this triangle of stars, which can be easily identified in the sky, above our heads, near the zenith. Next to the bright Vega in the constellation Nebula, four stars form a parallelogram. Between the southern pair of stars in the triangle is the planetary nebula M57 - the Ring Nebula (see pictures in the previous column). The Ring Nebula is actually the outer shells of a star that ended its life as a white dwarf, shedding all the shells around its dense core into the interstellar medium.
If you continue the line from Denev - the tail of the swan - through the middle star of its wingspan (the middle of the three stars arranged in a clear row before Denev), you reach a double star of the most beautiful - aka Albireo, the head of the swan (about halfway and a little above the line connecting Vega and Altair ). Albireo is about 385 light years away from us. To the unaided eye it appears as a single star, but through a telescope it appears separated into two - one yellow at magnitude 3.1, and the other blue, at magnitude 5.4, with the angular distance between the two being about 34 seconds of arc (about half a minute, which is 1/60 of a degree).
Viewing double stars in general, and Albireo in particular, is enjoyable, because not only are there more stars in the field of the telescope or binoculars than the single star visible to the eye, but when stars are close (angular) to each other, you can notice more strongly the differences in brightness and especially the differences in colors between them . There is no one like Alberio to demonstrate this phenomenon. Within the summer triangle, between the swan and the eagle, there are two small groups: the Vulpecula group whose stars are pale, and next to it the Sagitta group, whose shape matches its name and whose stars are brighter. To the east of the summer triangle are two more lovely groups - a dolphin group, in the shape of a prominent rhombus of stars with a tail, and next to it a foal group (Equuleus).
Next to Zenit is the most prominent group in this period - the fifth largest group (out of 88 groups) - named after a mythological hero, aka Hercules. The Hercules group is a paradise for double stars (such as Zeta (z), Delta (d) and Alpha (a, also known as Rasalgethi, which means "head of the kneeler" - he is the hero himself, Hercules).
The Hercules group has a variety of variable stars (stars that change their brightness in some cycle), and it is also home to two beautiful globular clusters - M13 and M92, as well as the planetary nebula NGC 6210 (which is 4,700 light-years away from us and spans almost half a light-year) . M13 (photo 1) is the most familiar object in the group, located, quite conveniently for observers, on one of the sides of the central square. It is a globular cluster about 25 light-years away from us and contains hundreds of thousands of stars, maybe even a million.
The cluster was discovered in 1714 by the renowned English astronomer Edmund Halley, and 34 years ago the cluster was chosen as the destination for one of the first radio messages intended for potential extraterrestrial intelligent beings. The message was sent from the large radio telescope in Arecibo (by the way, the message will of course take about 25 years to reach the cluster area; that is, we should not expect an answer before 50 years or so). Other prominent globular clusters in the night sky of this season are M5 in the area of the head of the serpent (Serpent group - Serpens - is the only group that is divided into two - head and tail, with another but definitely related group located between the two parts, which is the serpent bearer - Ophiuchus), and The famous M4 is near the heart of the scorpion - Antares, which we will describe later.
The cart is lowered
At this time in the evening, the great chariot descends towards the northern horizon, west of the North Star (Polaris), while Cassiopeia, which is in front of it, with the W shape, is already protruding above the horizon, east of Polaris. It is still possible to follow the arc of stars that form the three stars of the cart handle, through Arcturus who is shepherding bears, and ending with Sika of Virgo. And if we've reached the zodiac groups, then it's time to say goodbye to the impressive Leo group that is already nearing sunset in the early evening hours. Between Virgo and Libra proudly shines the planet Jupiter (on its spots in the titles), which will faithfully accompany us in the southern and western skies until the beginning of autumn.
Just above the southern horizon, one of the groups that Shaman faithfully describes their appearance - the Scorpio group - from the head to the stinger at the end of the tail. The brightest star in the group, and one of the brightest in the sky, is Antares. It is a red and inflated supergiant of spectral type M (see legend on the map), which is about 600 light-years away from us and whose diameter exceeds the distance of Jupiter from the Sun (alternatively, it has a diameter that exceeds the diameter of our Sun by approximately 660 times). To the east of the Scorpion rises parallel to the southeastern horizon the group of Sagittarius (Sagittarius), and the entire area, facing towards the center of our galaxy, is saturated with stars and other magnificent celestial bodies. It is recommended to line up the area of Keshet and a little north of it (past Magen group) also using binoculars, then fields of stars and other luminous objects will be discovered in an impressive density.
As we approach the end of August, we will already be able to notice in the evening the rise of a large group from the east - Pegasus. About her - in the next column.
Meteors and meteor targets
A meteor is seen when a small particle enters the Earth's atmosphere from space. In most cases, the diameter of the particles is less than one millimeter. The speed of these particles is very high - about 10-70 km per second - and due to the heat created by the friction in the upper atmosphere of the earth, they burn at an altitude of about 120 to 80 km. The particles excite the atoms in the atmosphere along their trajectory (moving electrons in the atom to higher energy levels) and ionize them (release electrons from the atom).
When the atoms return to their original state, electromagnetic radiation is emitted in the visible light field (a similar phenomenon occurs in a fluorescent light bulb), which is visible to an observer from the ground as a fast light trail (this is actually the phenomenon known in popular parlance as a "falling star"). In rarer cases, when the body penetrating the atmosphere is larger and composed of stone or iron, the body may survive during the passage through the atmosphere, and part of it may hit the ground (see Noah Brosh's article "The never-ending story of 2004 MN4", in this issue). The impacting body is called a meteorite. The many impact craters that can be seen on the moon, for example, are the result of meteorites hitting the lunar surface.
Every night it is possible to notice individual (sporadic) meteors originating from dust particles that randomly crossed the Earth's orbit. Sometimes the Earth passes through a swarm of dust left behind by a comet in its orbit around the Sun, and a meteor shower occurs. All the meteors in the swarm travel in parallel orbits, and therefore, due to the phenomenon of perspective, the resulting meteors appear as if they emerge from a single point in the sky. The starting point on the surface of the firmament is called the radiant.
In most cases, the meteor shower is named after the constellation in which the radiant is located. On August 12, as indicated on the map, the annual Perseid shower will reach its peak - meteors coming from the direction of the constellation Perseus, and therefore named after her. The origin of the Perseid shower is the comet Swift-Tuttle, which orbits the Sun once every 133 years (the last pass near the Earth occurred in 1992).
(This article appeared in Galileo at the beginning of the month, so it is an event that has already taken place)
The new companion of the Great Red Spot and the possible collision
In February 2006, the white elliptical body BA - White Oval, which is the product of mergers between three storms (which occurred during the years 2000-1998), was observed on the surface of Jupiter, changing its color to a reddish shade that is getting stronger, very similar to the color of the old great red spot. Since then this spot has been called Red Spot Junior (hereafter, "the young spot"). The young spot is located west of the Great Red Spot across one of the cloud bands in Jupiter's southern hemisphere, and is about the same diameter as the Earth (about half the size of the Great Spot).
Researchers believe that the appearance of the young spot on its new color, a fact that probably indicates the strengthening of the storm, is related to climatic changes on a wider scale (global changes) occurring in Jupiter's atmosphere. Like the Great Spot, the Younger Spot also appears to protrude several kilometers above Jupiter's cloud tops. It is not yet clear what is the reason for the color of these spots, but one of the leading theories holds that the currents rising inside the storms bring up material from lower layers in the atmosphere, and certain compounds in it undergo chemical changes under the influence of UV radiation from the sun and turn red. These compounds probably include traces of sulfur, phosphorus and various hydrocarbons (compounds made of carbon and hydrogen atoms in different ratios).
If you want to try to observe Jupiter and the red spots through telescopes (high-quality and large key, it should be said, because good magnification is needed), you can get the times when the big spot is directed to us, for example on the page on the website Sky & Telescope .
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