Today, September 14, 2013, marks exactly 5 years since the sudden activation of the Shiveluch volcano, which led to partial destruction of its foundation. On this day, we tried to select the 10 largest volcanic eruptions, which were recorded and assessed by a special scale - the Volcanic Explosiveness Index (VEI).
This scale was developed in the 80s, it includes many factors, such as the volume of the eruption, speed and others. The scale includes 8 levels, each of which is 10 times greater than the previous one, that is, a level 3 eruption is 10 times stronger than a level 2 eruption.
The last level 8 eruption took place on earth more than 10,000 years ago, but there have still been powerful eruptions throughout the history of mankind. We offer you the TOP of the 10 largest volcanic eruptions over the last 4000 years.
Huaynaputina, Peru, 1600, VEI 6
This volcano created the largest eruption in South America in the history of mankind. The instantaneous release instantly created several mudflows that headed towards the Pacific coast. Due to the ash thrown into the air, summers in South America were one of the coldest in half a millennium. The eruption destroyed nearby cities, which were rebuilt only a century later.
Krakatoa, Sunda Strait, Indonesia, 1883, VEI 6
All summer, a powerful roar inside the mountain foreshadowed the eruption that occurred on April 26-27. During the eruption, the volcano threw out tons of ash, rock and lava; the mountain was heard thousands of kilometers away. In addition, a sharp shock created a forty-meter wave; even on another continent, increases in waves were recorded. The eruption killed 34,000 people.
Volcano Santa Maria, Guatemala 1902, VEI 6
The eruption of this volcano was one of the largest in the 20th century. A sharp shock from a volcano that had been dormant for 500 years created a crater one and a half kilometers wide. The volcano claimed the lives of hundreds of people.
Novarupta Volcano, Alaska Peninsula, June 1912, VEI 6
This volcano is part of the Pacific Ring of Fire and had the largest eruption of the 20th century. The powerful explosion sent 12.5 cubic kilometers of ash and magma into the air.
Volcano Pinatubo, Luzon, Philippines, 1991, VEI 6
The eruption released so much ash that the roofs of nearby houses collapsed under its weight. In addition to ash, the volcano released other substances into the air, which reduced the temperature of the planet by half a degree for a year.
Ambrym Island, Republic of Vanuatu, 50 AD, VEI 6 +
One of the largest eruptions in history occurred on this small island. To this day, this volcano remains one of the most active in the world. The eruption formed calderas 12 km wide.
Volcano Ilopango, El Salvador, 450 AD, VEI 6 +
Although this mountain is located only a few miles from the capital, San Salvador, it has created an incredible eruption in the past. It destroyed all Mayan settlements and covered a third of the country with ash. Trade routes were destroyed, and the entire civilization was forced to move to the lowlands. Now the crater contains one of the largest lakes in El Salvador.
Mount Thera, Greece, circa 1610 BC, VEI 7
Archaeologists believe that the force of the eruption of this volcano is comparable to several hundred nuclear bombs. If there were inhabitants here, they either fled or died under an irresistible force. The volcano not only raised huge Tsunamis and lowered the temperature of the planet with huge clouds of sulfur, but also changed the climate as a whole.
Changbai Volcano, China-Korea border, 1000 AD, VEI 7
The eruption was so strong that there was ash deposits even in northern Japan. Over the course of a thousand years, the huge craters have turned into lakes that are popular with tourists. Scientists suggest that still unexplored creatures live in the depths of the lakes.
Mount Tambora, Sumbawa Islands, Indonesia, 1815, VEI 7
The eruption of Mount Tambora is the most powerful in the history of mankind. The mountain roared so loudly that it was heard 1,200 miles away. In total, about 71,000 people died, and ash clouds covered many hundreds of kilometers around.
Tenth planet of the solar system discovered
The International Astronomical Society has confirmed the discovery of the 10th planet in the solar system.
California Institute of Technology spokesman Mike Brown said the new planet is larger than Pluto, which has a diameter of about 2,250 km, and is twice as far from the Sun. According to scientists, the distance to it is now 97 times the distance from the Earth to the Sun. The planet revolves around the Sun in approximately ten and a half thousand Earth years. And the orbital radius is 130 billion kilometers.
The object has not yet received an official name, but the discoverers are temporarily calling it 2003 UB313 or Sednaya - in honor of the sea deity of the Eskimo Inuit tribe.
The new planet was discovered by Michael Brown of Tsaltech, Chad Trujillo of the Gemini Observatory in Hawaii, and David Rabinowitz of Yale University.
In an interview with BBC, Rabinovich said: "This is an amazing day and an amazing year. 2003 UB313 is possibly larger than Pluto. It is less bright than Pluto, but is three times further away than it. If only it were at the same distance as "Pluto, then it would be brighter than it. Now the world knows that there are other Plutos that are located on the outskirts of the solar system, where they are difficult to find."
The planet was discovered using the Samuel Oschin Telescope at the Palomar Observatory, as well as the Gemini North Telescope in Hawaii.
"The spectral samples obtained at Gemini Observatory are particularly interesting because they indicate that the surface of this planet is very similar to the surface of Pluto," said Chad Trujillo. It is composed mainly of rocks and ice.
The orbit of 2003 UB313 is not similar to the orbits of other planets, possibly due to the influence of Neptune. Astronomers believe that at some point in the planet's history, Neptune's gravitational influence threw it into an orbit rotated 44 degrees to the ecliptic plane.
The new cosmic body was first noticed on October 21, 2003, but then scientists did not suspect that it was moving. Fifteen months later, in January 2005, telescopes were unable to detect it at the same point in the sky. Researchers say they tried to locate the planet using the Spitzer Space Telescope, which detects infrared light, but were unable to find it. From this it was concluded that the object was moving.
The upper limit of observational error under these conditions is 3 thousand km, which means that the diameter of the planet cannot be greater than this figure, scientists say. And even the lowest limit of observational error makes the new planet a larger celestial body than Pluto.
However, if the diameter of the cosmic body turns out to be only about 2 thousand km, the discovered object will fall from the category of planets under the definition of “planetoid”.
However, the celestial body presumably has its own satellite. This explains the extremely long period of rotation of the find around its axis - from 20 to 50 days.
As Brown explained, 2003 UB313 will be visible in telescopes over the next six months in the constellation Cetus. He also admitted that scientists hoped to first double-check all the data and then only make the discovery public, but there was a leak of information. Previously, the Spaniards named the discovered cosmic body 2003 EL61, and the Americans - K40506A.
As BBC science columnist David Whitehouse points out, since the discovery of Neptune in 1846, this planet has become the largest celestial body discovered by astronomers in the solar system.
How does this relate to the recent discovery of another planet?
The period of revolution here and there is 10,000 years
Top right: The 48-inch telescope of the Schmidt system of the Palomar Observatory, on which, over the course of three years, the following were successively discovered: Quaoar (June 2002, classic Kuiper belt object with a diameter of about 1250 km), Sedna (November 2003, “something” with a diameter no more, but not much less than 1700 km) and Planet 2004 DW (February 2004, resonance from the plutino family with a possible diameter in the range of 840-1800 km).
We discovered the minor planet 2003 VB12 (popular name Sedna) - the most distant object in the Solar System found to date. Old photographs from 2001, 2002, 2003, in which it was found, allowed us to clarify the orbit of Sedna. It turned out to be very elongated, and at the same time completely lying outside the Kuiper belt: its semi-major axis is 480 ± 40 AU. and perihelion distance 76±4 AU.
Such an orbit is unexpected from our current understanding of the solar system. It can be either (1) the result of scattering on an as yet undiscovered distant transplutonian planet, or (2) the result of disturbance from a passing star that passed extremely close, or, finally, (3) the result of the formation of the Solar System in a close star cluster.
In all of these scenarios, there would likely be another significant population of trans-Neptunian objects beyond those we know of in the Kuiper Belt (classical Kuiper Belt objects, resonances, and diffuse Kuiper Belt objects). Moreover, in the two most likely scenarios, Sedna receives the best explanation as an object in the inner part of the Oort cloud.
Rice. 1. The Eskimo goddess of the sea Sedna, in whose honor the distant transplutonian planet 2003 VB12 received its name (still unofficial). According to Eskimo myths, Sedna lives in the dark depths of the cold Arctic Ocean. Astronomers have found that a good celestial analogue for these regions is the distant outskirts of the Solar System beyond the Kuiper Belt.
Rice. 2. The discoverer of the planet, Michael Brown, asked the Eskimo goddess of the sea, Sedna, for a small delicacy in honor of his discovery. Apparently, she did not leave him without a reward.
Introduction
The planetary zone of the Solar System (the so-called zone of almost circular orbits with a low inclination to the ecliptic) apparently ends at a distance of about 50 AU. from the sun. This figure just marks the outer edge of the classical Kuiper belt. As is known, many bodies from the planetary zone with highly eccentric orbits - comets and scattered Kuiper belt objects - successfully cross this boundary, but their perihelia always remain within the planetary zone.
Far beyond its borders lies the kingdom of comets. Astronomers believe that many of these icy bodies inhabit the hypothetical Oort cloud, the distance to which could be about 10 thousand AU. The lion's share of the comets in this hypothetical cloud probably remain there indefinitely, with only disturbances from passing stars or galactic tidal effects occasionally disturbing the orbits of some of them, causing them to invade the inner solar system. Here they are discovered by astronomers under the guise of new long-period comets.
Thus, it turns out that any currently known or expected in the future object of the Solar System must have at least one of two properties: either its perihelion lies inside the planetary zone, or its aphelion is in the Oort cloud (possibly both).
Beginning in November 2001, my colleagues and I began systematically scanning the sky for distant, slow-moving objects on Palomar Observatory's 48-inch Schmidt telescope using the new QUEST wide-field CCD camera. This survey will last approximately 5 years and should cover most of the sky accessible to the Palomar Observatory telescopes. Once completed, it will be the largest sky survey aimed at searching for distant moving objects since a similar survey by Pluto discoverer Clyde Tombaugh (1961). The main goal of our survey: the search for those rare large Kuiper belt objects that were missed in local, but more sensitive surveys, which brought us the bulk of faint Kuiper belt objects discovered over the past twelve years.
Rice. 3. Dome of the 48-inch Schmidt telescope (Mount Palomar, 1700 m above sea level). This unique instrument's field of view is 36 square degrees, allowing it to perform a wide variety of sky surveys with high efficiency.
Rice. 4. The new 172-megapixel QUEST camera, mounted at the focal point of Palomar's 48-inch Schmidt, is truly a machine of great discovery. Under two rectangular curtains there is hidden a whole field of CCD matrices (122 pieces), with a total area of 25 x 20 cm. It was on them that Quaoar, Sedna and planet 2004 DW cast their dim light, revealing their existence. However, even such a giant light detector as the QUEST camera does not cover the entire clear (non-vignetted) field of view of the telescope with a diameter of 5.4°. Schmidt's camera is a great thing!
It was as part of this review that on November 14, 2003, we first saw Sedna, which, in three consecutive images taken at an interval of an hour and a half, moved by only 4.6 arcseconds. Over such a short time interval, the displacement of a trans-Neptunian object, almost in opposition to the Sun, is determined almost entirely by the parallax caused by the Earth's motion in its orbit. In this case, we can approximately estimate the distance to the object using the formula R = 150/delta, where R is the heliocentric distance to the object in astronomical units, and delta is its angular velocity in arcseconds per hour. It immediately follows that the object we found is approximately 100 AU away from the Sun! This is significantly further than the outer limit of the planetary zone (50 AU), as well as any of the objects in the Solar System known to us. It was temporarily designated as a minor planet with the number 2003 VB12.
Rice. 5. Animation of three images taken on November 14, 2003 at 6:32, 8:03 and 9:38 UTC in which Sedna was first spotted.
Subsequent observations of the object with the 0.36-meter Tenagra IV telescope (Arizona), the 1.3-meter SMARTS telescope at Cerro Tololo Observatory, and the 10-meter Keck Telescope, carried out between November 20, 2003 and December 31, 2003, allowed us to calculate the preliminary orbit of the new planet . To do this, we used the method of Bernstein and Kushalani (2000; hereafter BK2000), which was developed specifically for distant objects in the Solar System, as well as the least squares method, which is free from any a priori assumptions regarding the calculated orbit. Both methods independently produced a distant eccentric orbit with the object now approaching perihelion. However, the resulting semimajor axes and eccentricities varied greatly, and this difference is caused by the natural limitations of the methods in determining the orbits of extremely slowly moving objects with small observed displacements in the sky. For such celestial bodies, at least a multi-year observation interval is required to obtain a more or less accurate orbit, which we did not have.
Rice. 6. Here is a unique automated private amateur observatory "Tenagra", located in Arizona at an altitude of 1312 m above sea level. It was built, or more precisely, made his childhood dream come true, by professional archaeologist Michael Schwartz. Many professional astronomers use the services of this observatory today! (This is really amateur help to professionals.)
Despite the fact that the text of the author’s article mentions the smallest 36-cm telescope of the observatory, Tenagra IV (the distant white dome in the photo), this is most likely a typo: Sedna with a magnitude of 21 m is beyond the power of such an instrument. The website of the Tenagra Observatory says that Sedna was photographed by the largest 0.81-m telescope of this observatory, which is hidden under one of the two nearby domes.
Rice. 7. The 0.81-meter Tenagra II telescope of the Ritchie-Chrétien system, specially designed for fully automated control. Provides exceptionally accurate positioning and guidance of selected objects. A 5-minute exposure without filters easily allows the telescope to reach stars with a magnitude of 22 m. Note that Michael Schwartz managed to hide this serious telescope in a really small dome.
Images of Sedna in old photographs
Fortunately, the discovered planet turned out to be bright enough to try to find it in archival images of recent years. At the same time, each time we found it in some old photograph, we were able to recalculate the orbit more accurately and accurately search for it in photographs of even more distant eras.
To begin with, it turned out that on August 30 and September 29, 2003, the new planet was supposed to fall into the field of view of the same Palomar QUEST camera during a survey scan of the sky performed by another team of astronomers. Its position on these days was predicted from our initial orbits within a very small error ellipse of 1.2 x 0.8 arc seconds (both methods, diverging in the exact orbital parameters, nevertheless gave almost identical positions for this period). It actually contained a celestial body of the corresponding brilliance, and the only one. The orbit, now refined over a four-month interval, allowed us to predict the position of Sedna even earlier, and thus four more images of the new planet were found until September 2001.
An attempt to calculate the orbit for the year 2000 and even earlier resulted in several probable images of Sedna in the corresponding images, but with significantly lower data quality. For this reason, we decided not to consider them.
Calculating the exact orbit
The most probable orbit in the BK2000 method for the entire set of data in the interval 2001-2003 gave the following orbital parameters:
The current distance from the Sun to Sedna is 90.32±0.02 AU.
- semimajor axis a = 480±40 au.
- inclination of the orbit to the ecliptic i = 11.927°
In this orbit, Sedna will reach perihelion on September 22, 2075 (±260 days), being at a minimum distance from the Sun of 76 AU. The least squares method yielded a generally similar orbit with parameters within the errors of the BK2000 method.
Rice. 8. Orbit of Sedna. At the center of coordinates is the Solar System, surrounded by a swarm of planets and known Kuiper Belt objects.
The current heliocentric distance to Sedna is 90 AU. fits well with the simple assessment we made already on opening night. Thus, Sedna now turns out to be the most distant body in the Solar System known to us. At the same time, we know well that many comets and Kuiper belt objects, moving along their highly eccentric orbits, will sooner or later end up even further from the Sun, and there is nothing unusual about this. Thus, the very location of Sedna at such a great distance is not at all something challenging for our ideas about the Solar system.
It's not about him, but about the anomalously large perihelion distance! After all, the farthest perihelion of previously discovered trans-Neptunian objects is 46.6 AU. It is possessed by the minor planet 1999 CL119. The perihelion of Sedna does not fit into any framework. To test its reliability, we rushed to recalculate Sedna's orbit, randomly adding 0.8 seconds of noise to its astrometric coordinates (that's two root mean square errors!). Having performed this procedure 200 times, we were convinced that the resulting perihelion did not fall outside the range of 73-80 AU.
Origin of Sedna
The orbit of the new planet turned out to be unlike any previously known. It resembled the orbits of scattered Kuiper Belt objects, with the only difference that its perihelion was much further away - so far away that the formation of such an orbit cannot be explained by scattering on the known planets of the Solar System. The only mechanism that could place Sedna in such an orbit would require either disturbance from an as yet undiscovered distant planet or forces acting on Sedna from outside the solar system.
1. Scattering on an undiscovered planet
Scattered Kuiper Belt objects ended up in their highly eccentric orbits due to the gravitational influence of the solar system's giant planets. As a result of scattering, they receive different portions of energy and thus different semi-major axes, but - and this is important - they almost do not change their perihelion distance. It is believed that objects scattered by Neptune may achieve a perihelion distance of no more than 36 AU. Although more complex interactions, taking into account the possible migration of Neptune in the past, sometimes make it possible to “raise” the perihelion of a scattered body to 50 AU. Thus, before the discovery of Sedna, we had the necessary mechanism to explain each and every orbit of known Kuiper Belt bodies, including objects such as 1999 CL119.
Sedna with perihelion around 76 AU. obviously violated the harmony of the overall picture, because it could not be scattered by any of the known giant planets. The first thought that comes to mind to restore the broken picture is the thought of the existence of a planet not yet discovered by astronomers at a distance of about 70 AU, which scatters distant objects in the same way as Neptune does in the Kuiper belt. The current state of our survey is that we have covered at least 80% of the sky in a 5º wide band around the ecliptic - the region most likely to find such a planet - and have not found any planet there (Brown and Trujillo 2004). Based on this, we are inclined to think that such a planet most likely does not exist there, although we still cannot exclude the possibility itself.
If it really exists - or was there at some time in the past - its signs will inevitably appear in the orbital parameters of those new small planets that will be discovered in the future in that distant region. Namely: they should have moderate orbital inclinations and perihelion distances close to 76 AU. (like Sedna).
Rice. 9. The outer reaches of the solar system. This intricate diagram shows the shaved shapes of trans-Neptunian objects known by the year 2000. In red are the orbits of plutino, in blue are the orbits of classical Kuiper Belt objects, in black are the orbits of scattered Kuiper Belt objects. A careful study of the latter shows that their perihelia are always close to the orbit of Neptune. The reason is clear: a scattered body, moving along a closed elliptical orbit, will always return to the zone from which it was scattered.
Sedna's orbit, which does not obey this rule, suggests that somewhere beyond Neptune another planet rotates - Planet X, which "scattered" Sedna into a highly eccentric orbit with a high perihelion.
2. Close passage of a star
Sedna's unusual orbit bears many similarities to the suspected orbits of Oort cloud comets. It is believed that the latter were formed in the ordinary solar system at the dawn of its existence. During close encounters with giant planets within the planetary zone, they were scattered into highly eccentric orbits. If such an orbit takes the comet at a sufficiently large distance from the Sun, random gravitational disturbances from nearby stars and galactic tidal forces can change it in such a way that the comet's perihelion "rises" far beyond the planetary zone and thus loses all connection with the planet itself. system.
Calculations taking into account the expected frequency of stellar encounters in the vicinity of the Sun and the magnitude of galactic tidal forces show that the comet must have a semi-major axis of at least ~10 4 AU before these external forces begin to play a noticeable role (this result was obtained by Oort in 1950). When the comet does go to such large distances, its orbit is significantly thermalized: it receives an arbitrary inclination (distribution of orbital inclinations i becomes isotropic) and the average eccentricity is about 2/3. Continued disturbances can bring the perihelion back into the planetary zone, and then the object again becomes visible - like a comet with a still huge semi-major axis of the order of 10 4 AU.
The obvious incompatibility between the standard picture of the formation of the Oort cloud and the orbit of the newly discovered planet lies in its “dwarf” semi-major axis, which is clearly not enough for external forces to effectively influence the orbit of Sedna and shift its perihelion.
Let's assume that Sedna was once scattered into a highly elongated orbit by one of the giant planets, for example, Neptune. Calculations show that a body with a semimajor axis of 480 AU. and perihelion within the planetary zone can, under the influence of external forces, change its perihelion distance over the entire lifetime by only 0.3%. A stronger perihelion shift for a body so tightly attached to the Sun (compared to Oort cloud comets) is possible only as a result of a much closer stellar encounter than can be expected in the current galactic neighborhood of the Solar System.
Only a small fraction of the geometrically possible configurations of stellar encounters are able to change the orbit of scattered Kuiper Belt objects so that they become more reminiscent of the orbits of bodies from the Oort cloud. One example is the passage of a solar mass star at a speed of 30 km/s perpendicular to the ecliptic plane at a distance of only 500 AU. from our luminary. Such a rendezvous could transform an orbit with a perihelion distance of ~30 AU. and semimajor axis 480 AU. into an orbit with a perihelion distance of 76 AU, keeping the semi-major axis unchanged (in other words, transfer the diffuse Kuiper belt object to the orbit of Sedna).
The need for a special geometry of rapprochement is not surprising, but let’s assume that it was just like that.
It is much more difficult to explain the fact that, in the current stellar environment of the Solar System, one can expect only one such close passage of another star during the entire existence of our planetary system.
If the population size of scattered Kuiper Belt objects in highly eccentric orbits (with major semi-axes like Sedna) were always high, the uniqueness of such a rapprochement would not raise any questions - it could have happened at any time over the past 4.5 billion years and done its job . However, in reality, the number of such highly elongated scattered orbits (the perihelia of which can be “raised” to the level of Sedna and obtain a purely Sedna orbit) should have been high only in the early era of the history of the Solar System - when it was actively cleared of icy planetesimals and actively populated the Oort cloud. In light of this, the probability of a super close encounter between the Sun and another star at precisely this short moment in the existence of the Solar System looks very low.
However, if such a rapprochement really took place, its signs will also unmistakably appear in the orbital parameters of all objects that will be discovered in this area subsequently. Namely, if all the bodies in the inner part of the Oort cloud have orbital parameters compatible with the geometry of a unique close flyby event, it will be obvious that we are dealing with signs of this event imprinted in them.
3. Formation of the Solar System in a star cluster
Close stellar encounters could have occurred much more frequently in the early era of the Solar System if the Sun was born inside a star cluster. Moreover, under these conditions, the relative velocities of stars during approach should have been significantly lower, which would have led to much more powerful dynamic effects. Numerical simulations performed by G. Fernandez and A. Brunini in 2000 showed that multiple, slow, moderately close approaches could very well place scattered Kuiper Belt objects into orbits similar to Sedna.
This process is identical to the proposed process of formation of the more distant Oort cloud, with the only difference that in a closer stellar environment, comets (or planetesimals) do not need to have such huge orbital semi-major axes in order for external influences to begin to work. Calculations by Fernandez and Brunini predict that the formation of the Solar system in a close stellar environment should fill the inner part of the Oort cloud with a whole population of objects with semi-major axes ~10 2 - ~10 3 AU, perihelia in a wide range of ~50 - ~10 3 AU i.e., large eccentricities (on average 0.8) and a wide distribution of inclinations (FWHM ~90°).
We consider this scenario the most plausible to explain the orbit of the newly discovered planet. The birth of the Solar System in a star cluster is a completely logical assumption, indirect evidence of which has been found in its other features (Goswami & Vanhala, 2000). If this scenario turns out to be true, the orbits of objects subsequently discovered in this region will unmistakably reflect the early era of the solar system's life in the cluster. They will have a wide range of inclinations and perihelion distances, but will not fit into the geometry of a single unique stellar encounter. Moreover, numerical calculations by Fernandez and Brunini show that the exact distribution of orbits in the inner region of the Oort cloud will reflect the size of the parent star cluster!
Rice. 10. It's hard to believe that beyond the outer edge of the Kuiper Belt there are worlds that never approach the Solar System, from which it is clearly visible. However, the discovery of Sedna shows that this is the case. Moreover, it may turn out that there are a great many of them there and among them there are very large specimens.
Results
Each of the three described scenarios for the appearance of Sedna in the Solar System imposes its own unique requirements on the dynamic characteristics of the distant population of trans-Neptunian objects beyond the Kuiper Belt. While only one such object has been discovered, the parameters of its orbit do not allow us to prefer either hypothesis. But as soon as new discoveries follow, uncertainty may dissolve before our eyes.
You can even roughly estimate how soon this will happen. Before the discovery of Sedna, as part of our survey, we came across 40 new Kuiper belt objects. Assuming that the size distribution of the distant population of sedna-like objects is the same as in the Kuiper Belt, one would expect other sky surveys to show the same ratio in the proportion of objects discovered - 1:40 - if they are, of course, as sensitive to slow-moving ones objects. The number of discovered trans-Neptunes as of March 15, 2004 was 831. It turns out that by this time, astronomers should have already had about 20 Sedna-like bodies in their catalogs!
Despite the crudeness of this assessment, the shortage is glaring. Therefore, either most sky surveys aimed at searching for small planets beyond Neptune are insensitive to slow-moving bodies (1.5 arcseconds per hour for Sedna), or there is a clear overpopulation of the inner part of the Oort cloud with relatively bright bodies (a region attractive for large planets?) . In any case, it seems to us that new facilities in the Sedna area will be opened very soon.
Until this happens, we can say that at first glance the third scenario (the birth of the Solar system in a dense star cluster) looks the most plausible. In this scenario, the Oort cloud would be filled from the farthest inferred outskirts (about 105 AU) all the way to the close vicinity of the Kuiper Belt (i.e., Sedna). In addition, under this scenario, the mass of the Oort cloud should be many times greater than previously thought, and the expected population of large objects such as Sedna would be considerable. Our view can spot Sedna no more than 1% of its orbit - near perihelion. This means that for every Sedna discovered, there are about 100 more like it, which are now far away and inaccessible to the QUEST camera. Moreover, the almost isotropic distribution of inclinations of the orbits of Sedna-like planets leads to the fact that for every discovered Sedna there should be about 5 more equally bright ones, which are currently located high above the ecliptic and simply have not yet fallen into the 5-degree band that we managed shoot. Taken together, this means that the discovery of just one Sedna itself predicts the existence of an entire population of similar bodies numbering about 500 objects. If the size distribution for objects from the inner part of the Oort cloud is still similar to the Kuiper belt, the total mass of this population will be about 5 Earth's. The invisible population of bodies with even greater perihelia than Sedna should most likely be even larger.
Obviously, subsequent discoveries of trans-Neptunian bodies with orbits lying entirely outside the Kuiper belt will make it possible not only to choose one of the described scenarios, but also to shed light on the early history of the formation of the Solar system in general.
shortened translation:
A.I. Dyachenko, columnist for the magazine "Zvezdochet"
> Sedna
Sedna– dwarf planet of the Solar system and trans-Neptunian object: description with photo, discovery, name, orbit, composition, connection with the Oort cloud, research.
The discovery of distant dwarf planets led to the fact that we lost Pluto as a planet. But scientists are not discouraged, because this provides a new field for research. In 2003 they noticed Sedna, considered the most distant object living in the Oort Cloud.
Discovery and name of the dwarf planet Sedna
This find also belongs to Michael Brown's team, which spotted the dwarf planet Sedna in 2003. Initially called 2003 VB12. It all started back in 2001, when a survey at the Palomar Observatory showed that at a distance of 100 AU. The object is located away from the Sun. Observations with the Keck telescope in 2003 demonstrated movement along a distant and eccentric orbital path.
Later it turned out that the celestial body was also included in the survey of other researchers. Sedna received its name in honor of the Inuit deity of the seas. Sedna was once mortal, but drowned herself in the Arctic Ocean, where she began to live with sea creatures.
The team announced the official name before documentation, which violated the protocol procedure. But the MAS did not object.
Classification dwarf planet Sedna
Sedna's status is still debated. Its discovery caused controversy over the definition of the planet. According to the IAU, the planet is obliged to clear its territory of unnecessary objects, which Sedna did not do. But to be a dwarf planet, it must also be in hydrostatic balance (become a spheroid or ellipsoid). With an albedo of 0.32 and a diameter of 915-1800 km, it has enough mass and brightness to form a spheroid. Therefore, Sedna is considered a dwarf planet.
Size, mass and orbitdwarf planet Sedna
Physical characteristics of the dwarf planet Sedna |
|||||
| Opening | |||||
|---|---|---|---|---|---|
| Discoverer | M. Brown, C. Trujillo, D. Rabinovich |
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| opening date | November 14, 2003 | ||||
| Orbital characteristics | |||||
| Perihelion | 76.315235 a. e. | ||||
| Aphelion | 1006.543776 a. e. | ||||
| Major shaft ( a ) | 541.429506 a. e. | ||||
| Orbital eccentricity ( e ) | 0,8590486 | ||||
| Sidereal period | approximately 4404480 d(12059.06 a) | ||||
| Orbital speed ( v ) | 1.04 km/s | ||||
| Average anomaly ( M o ) | 358.190921° | ||||
| Inclination ( i ) | 11.927945° | ||||
| Longitude of the ascending node (Ω) | 144.377238° | ||||
| Periapsis argument (ω) | 310.920993° | ||||
| physical characteristics | |||||
| Dimensions | 995±80 km | ||||
| Weight ( m ) | 8.3 10 20 -7.0 10 21 kg (0.05-0.42 of the mass of Eris) |
||||
| Average density (ρ) | 2.0? g/cm³ | ||||
| Acceleration of gravity at the equator ( g ) | 0.33-0.50 m/s² | ||||
| Second escape velocity ( v 2) | 0.62-0.95 km/s | ||||
| Rotation period ( T ) | 0.42 d (10 h) | ||||
| Albedo | 0.32±0.06 | ||||
| Spectral class | (red) B−V = 1.24; V−R = 0.78 | ||||
| Apparent magnitude | 21,1 20.4 (at perihelion) |
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| Absolute magnitude | 1,56 | ||||
In 2004, the upper limit for the diameter was 1800 km, and in 2007 – 1600 km. A survey with the Herschel telescope in 2012 set the boundaries at 915-1075 km. Sedna has no satellites found, so its mass cannot be calculated. But it ranks 5th among TNOs and dwarf planets. It circles the star along a highly elliptical orbital path and moves away to 76 AU. and 936 a.u.
It is believed that one orbital passage takes 10,000-12,000 years.
Compound dwarf planet Sedna
At the time of its discovery, Sedna appeared to be a bright object. The color of the dwarf planet is almost red like Mars, which could be caused by the presence of tholins or hydrocarbons. The surface is uniform in color and spectrum.
The crust is not dotted with crater formations, so there are not many bright ice trails. The temperature drops to -240.2°C. Models show an upper limit of 60% for methane ice and 70% for water ice. But M. Barucci's model indicates the composition: titons (24%), amorphous carbon (7%), nitrogen (10%), methanol (26%) and methane (33%).
Nitrogen hints that the dwarf may have had an atmosphere in the past. When approaching the Sun, the temperature rises to -237.6°C, which is enough for the sublimation of nitrogen ice. This may also result in the presence of an ocean.
Origin dwarf planet Sedna
The team believed that the celestial body belonged to the Oort Cloud, where comets reside. This was based on the remoteness of Sedna. It was recorded as the inner body of the Oort Cloud. In this scenario, the Sun formed in an open cluster with other stars. Over time, they separated, and Sedna moved to a modern orbit. Computer simulations support this idea.
If Sedna were to appear in its current position, it would hint at further expansion of the protoplanetary disk. Then its orbit would be more circular. Therefore, it would have to be pulled by powerful gravity from another object.
Or the orbit could have formed from contact with a large binary neighbor, 1000 AU distant. from the sun. Nemesis was even considered among the options. But there is no direct evidence.