How the Universe expanded in 2013

In the past year, there were no revolutions in Astrophysics. However, this does not mean that there were no interesting discoveries in this area. Doct. physical. Sciences, V.N.S. Department of relativistic Astrophysics of the GAS of Moscow State University Sergey Popov tried to cover the spectrum of astrophysical studies of 2013 as widely. For this purpose, he used reviews of the astrophysical part of the archive (arxiv.org), which publishes more than 1000 works a month. The article tells about the most important results of astrophysical studies published in the archive last year.

1. Mysterious bursts

Let's start the story with an incomprehensible mysterious bursts. In astronomy, outbreaks are often found, the nature of which, it turns out, is very difficult to determine. This year there were three similar discoveries, deserving of a detailed consideration. All heard about gamma-ravers, opened back in the late 1960s with the help of American intelligence satellites launched to control nuclear tests. Only in the late 1990s it was possible to reliably determine that bursts come from cosmological distances. Apparently, short bursts (a length of order of a second) are associated with the mergers of neutron stars, and long - with a special type of supernova.

Observations showed that outbreaks in the gamma-band can be accompanied by longest bursts in the radio-and in visible rays. And in 2013, Brandley Cenko and co-authors found (Arxiv: 1304.4236), which are bursts that in optics and in radio behave like sources of gamma-splays, only the outbursts themselves are not visible. The surge was originally discovered in the visible range as part of the project “Palomar Transient Factory” (Palomar Transient Factory). Then they saw that there was a surge in the radiodiapason. The authors believe that they discovered the first example of a new type of space outbreaks. Perhaps this is the "cousin" of the gamma-vplesov, associated with the supernova, but for some reason, the strict radiation is suppressed there.

Another interesting surge was opened in the X -ray range. Peter Jonker and co -authors studied the archival data of observations on the Chandra satellite for 2000 and saw a flash there (Arxiv: 1310.7238). The distance to her is unknown, so there is a scope for imagination. True, there is one indirect evidence that can lead on the trail. The flash came from a direction close to the famous Galaxy M86.

The authors think that it was like that. In a small (not visible) ball cluster of the M86 galaxy, the white dwarf was torn by a tide created by the black hole of the intermediate mass. We are talking about a size of about 10 thousand masses of the Sun (much larger those black holes that are obtained from stars, and noticeably smaller than masked black holes in the centers of galaxies). An extremely interesting opportunity. True, not the only one. Perhaps the launch of the Spectr-RG satellite, which will overview of the sky in the X-ray range, will allow you to detect several similar events and establish their nature.

And now-the most important “back of the fuel” opening of 2013. The story began a few years ago. At the very beginning of the XXI century, radiostronomers have learned to highlight the individual extremely short - millisecondny enough! - Splash. Technically, this is not an easy task, because In the magnetosphere of the Earth, something is constantly “noisy”. The first discovery using the new methodology was the discovery of a new type of activity of neutron stars. But then the discovery in the field of extramalactic astronomy arrived.

In 2007, Duncan Lorimer and his colleagues discovered a millisecond radio capeus, which came from a distance of billions of light years. Theorists rushed to invent what it could be. And they waited for observers to open something else like that. But in the radiapasis, it is difficult to look for short outbreaks, because It is difficult to conduct reviews of a large area of ​​the sky.

Estimates showed that in the whole sky such outbreaks can occur a hundred times a day, but only small areas of the sky can be studied at a time. There were no new discoveries, and gradually began to gain the strength of the voice of skeptics, who said that this was some new phenomenon in the magnetosphere of the Earth, and not something amazing at cosmological distances.

Another similar surge was discovered in 2012 (the authors even suggested that it could be the last “cry” of the evaporating black hole-it was the search for such events that brought John O'SAllivan to the Wi-Fi inventor). But this surge was opened in the plane of our galaxy, and it was not obvious that he was a twin of the burst of Lorimer. Now it was possible to put a bold point.

Douglas Thornton (Douglas Thornton) and his colleagues presented (Arxiv: 1307.1628) data on four new bursts similar to Lorimer's surge. Now we are sure that there is an amazing class of millisecond radio supports that come to us from distant-long galaxies. It remains only to understand that this is: or these are outbreaks of magnetars - neutron stars with large magnetic fields, or it is massive neutron stars turn into black holes, or the result of the merger of neutron stars ... We do not know. We do not know yet.

In conclusion, we note that this year an interesting gamma-string GRB130427A was registered. This is a regular long gamma-ray gamut that happened relatively close: at the red displacement Z = 0.34. Therefore, for him it was possible to simultaneously measure a lot of effects: optical radiation at the time of a surge, supernatal, postponement, as well as radiation of the galaxy, in which this all happened. Maybe the study of this event (which caused the stream of articles, including several publications in Science at once) will help to better understand the details of the work of the gamma-implaces mechanism.

2. Supernova

From the bursts of mysterious we will move on to the bursts of a well -known, but not yet fully understandable. What is supernovae, it is known quite well for several decades. But it is still not possible to cover the whole variety of these phenomena and understand important details of the processes (it is enough to say that computer simulations cannot reproduce the explosion of a massive star without additional tricks), but without supernova would not have been with you.

2013 was rich in the discoveries of interesting supernova. For example, Cosimo Inserra (Cosimo Inserra) with colleagues found explosions that can be explained only by suggesting that as a result of the explosion, a magnet was born, which additionally “fester” the luminosity of the supernova (ARXIV: 1304.3320), which allows us to understand why the supernova remains brighter than usual. Eran Ophek and his colleagues were able to see the “cramps” of the star about a month before the explosion, as a result of which the star threw a shell weighing about 1% of the sun (1302.2633).

But the most interesting, in my opinion, opening is associated with Supernova PS1-10AF, opened during the Pan-Starrs project (Arxiv: 1302.0009). Ryan Chornock (Ryan Chornock) and co -authors found a distant one (red displacement Z = 1.4, i.e. the light from it has been 9 billion years old) a powerful supernova, the parameters of which cannot be explained by any model. In addition to great energy, it looks too red and gained shine too quickly. Perhaps the discovery of such exotic, in the end, will inspire theorists to create a truly realistic working model that “explodes in the computer”.

3. Neutron stars

After supernova explosions, neutron stars most often remain, because it's time to go to them. For “pulsarians”, probably one of the important observations of 2013 is the opening of the rapid restructuring of the PSR B0943+10 pulsar, discovered by Um Hermsen (Wim Hermsen) and its co -authors (1302.0203) for simultaneous observations in radio and X -ray ranges. Potentially, this can shed light on the work of the “Pulsar car”, theorists just continue to study this issue, and several important new studies have appeared in the outgoing year. But we will discuss a little more details of the other two works.

Firstly, once again a record of the mass of neutron stars is broken. True, quite a bit. The mass of the pulsar opened by John Antoniadis (John Antoniadis) and its co-authors (ARXIV: 1304.6875), barely exceeded 2 sunny (previously the record was “slightly less than 2 masses of the Sun”). But this is not important. It is significant that a massive neutron star enters a very close system with a white dwarf. It is known about this double (since the white dwarf was able to see directly in the optical range, measure the spectra, etc.), so now we have a very good tool for checking the theories of gravity. What astronomers will not slow down.

Secondly, astronomers were able to detect a strong magnetic field in a magnetar with a weak field (Arxiv: 1308.4987). “Paradox,” you say. Almost. This is the matter here. The neutron star SGR 0418+5729 shows classical magnetic activity. Outbreaks in the hard X -ray range were recorded from it. In the standard model, this behavior is associated with the release of energy of powerful electric currents. They create strong magnetic fields, therefore, more often they talk about the release of the energy of the magnetic field, where and the name of the entire class of objects - magnetars.

Magnetic fields of single neutron stars (for example, radio pulsers) are most often evaluated by the rate of slowing down their rotation. So, SGR 0418+5729 slows down slowly, which seems to be talking about a weak field. However. If we look at the sun, then, on the one hand, he has a rather weak large -scale (the so -called dipole, the very one that looks like a butterfly or eight, or a sign of infinity) field, and on the other, in the vicinity of solar spots, there are very powerful fields, which are just associated with solar outbreaks.

It turned out that some magnetars in this sense are similar to the sun. These neutron stars have a weak dipole field (relatively weak - only ten billion times stronger than the sun or earth; such fields are typical for radio pulsars). But near the surface there are colossal magnetic fields. If Andrea Tiengo and his colleagues measured everything exactly, then this is the largest magnetic field ever measured by man. And it was possible to do this thanks to a detailed study of the SGR 0418+5729 spectrum.

4. Stars

From neutron stars we will move on to the usual and discuss two plots. The oldest star was investigated (Arxiv: 1302.3180). She was called Mafusail. The star is at the stage of a subgant, which is more accurately determined by age, this makes the object unique. The distance to Mafusail is less than 200 light years. This is a little, so the object can be studied in detail. The inaccuracy in the assessment of age is associated only with an insufficiently measured chemical composition of the star.

Given the uncertainty, the age of the star surpasses 13.66 billion years. That is, it could be the star of the very first generation, but. Its chemical composition according to Howard Bond and co -authors indicates a noticeable (albeit small) content of elements heavier than helium. So the first stars still have to open. But Mafusail allows you to better understand the evolution of our galaxy.

Marek Nikolajuk and Roland Walter analyzed the flash, which was discovered in 2011 in 2011 in the direction of the NGC 4845. The splash is quite unusual (ARXIV: 1304.0397). Apparently, the central ultra-massive black hole, whose mass is estimated at a third of a million sunny, tore some object with its tide. Unusuality is associated with this object. This is either a very heavy planet or a brown dwarf. The mass of the "victim" is approximately 14-30 masses of Jupiter.

5. Explanet

So we got to exoplanets. Astronomers continue to remove cream in this extremely young field of research. In it, one could distinguish the ten most interesting results. In addition to discoveries, there are even interesting “closures”. For example, Paul Kalas (Paul Kalas) and his colleagues (Arxiv: 1305.2222) showed that the Fomalgaut B object, which was considered an exoplanet, is not such (though, apparently, this is even more interesting - such a bunch of construction waste in the disk around the young star).

There is an extremely interesting, but not yet one hundred percent result-the first discovery of the free (i.e., not rotating around any star) exoplanets with a satellite (ARXIV: 1312.3951), this was done by microlysising methods. We’ll talk a little more about three topics: measurement accuracy, unusual planets and zones of abode.

The modern accuracy of obtaining data on exoplanets is well illustrated by two results. Firstly, Thomas Barclay, Thomas Barclay, were able to find a planet in the “Kepler-37^ sizes less than Mercury (Arxiv: 1305.5587) in the data of the“ Kepler ”satellite.

Secondly, two groups of authors -Francesco Pepe and its co -authors (Arxiv: 1310.7987) and Andrew Howard with colleagues (ARXIV: 1310.7988) -firstly presented data in size and by mass for the planet of the Earth type. Its name is a fireplace -78. The mass is 1.86 earthly, and the radius is 16% more than that of our planet. The density is about 5.5 times higher than that of water. That is, it is an iron-stone planet. It would seem, what is the importance of this discovery? Wouldn't it be that? It turns out that it happens in every way, and therefore it is extremely important with high accuracy to confirm the expectations of astrophysics.

As an example, we consider the Kepler-87C planet. According to Kepler, its size is 6 times larger than earthly. But the mass, according to Aviv OFIR and his colleagues (Arxiv: L3L0.2064), more than the ground is not in tens, as you could expect, but only ... the same 6 times. That is, the density is 7 times less than that of water. This is a record for planets in the mass range of less than 10 earthly. And a riddle.

So far, we still do not know what exoplanets can be, but we increase statistics. At the end of December, the Kepler team presented new data based on the processing of 22 months of observation. The number of good candidates increased by more than 20% and exceeded 2.7 thousand. The number of stars with such exoplanets now exceeds 2 thousand (ARXIV: 1312.5358). The number of planets in the zones of habitability also increased, the boundaries of which, by the way, were slightly revised (Arxiv: 1312.3337). The fact is that the results of the new detailed modeling showed that we were previously too conservative, determining the internal boundary of the region where liquid water can exist on the surface of the planet.

There was a new statistics on planets of the type of earth, located in stars like the Sun in orbit with periods of about a year. These results were presented by Eric Pe-Tigura, Andrew Howard and Jeffrey Marsi (Erik Petigura, Andrew Howard, Geoffrey Marcy) (Arxiv: 1311.6806). The complexity of the task was that it was necessary to determine quite accurately how bad the “keupler” could open small planets with large periods. Estimates show that 3.5-7.5% of stars of the Sun type have planets with approximately earthly size and orbital periods of 200-400 days. This is a lot! Finally, an interesting Kepler-62 system (Arxiv: 1304.7387) was added. It contains five planets, two of them are in the zone of habitability, and their dimensions are only 1.4 and 1.6 earthly.

6. Galaxy

Concluding the conversation about the stars and exoplanets of our galaxy, before leaving it, we cast a glance at the Galaxy as a whole. In this, the Planck satellite will help us. Currently, the most cited work in astronomy is the map of galactic dust according to IRAS satellites (Infrared Astronomical Satelite), the infrared orbital observatory (1983), and COBE (Cosmic BackGround Explorer), and the space observator (1989).

“Planck” is a “third -generation COBE”, launched in 2009 to study the variations of the cosmic microwave. The second generation was WMAP (Wilkinson Microwave Anisotropy Probe) - a spacecraft launched to study relict radiation in 2001. It is not surprising that a new dust card in the galaxy, now already compiled according to Iras and the Planck (Arxiv: 1312.1300), will soon be able to become one of the most cited articles. The fact is that dust interferes with everyone, everyone looks through it and want to clean its “contribution” from the results of their observations. And for this you need accurate maps.

7. Extrogalactic astronomy

And here we are in the intergalactic expanses. A lot of interesting things were discovered there. So, the installation of Alma (Atacama Large Millimeter/Submillimeter Array), from which they expect important data in the field of non -healactic astronomy, showed the presence of giant molecular gas flows with masses exceeding 10 billion of the sun, in bright central galaxies of Abell 1664 cloths and the galaxies of the sun. Abell 1835 (Arxiv: 1309.0013; 1309.0014). A group of three quasars is open (Arxiv: 1302.0849). This is just a second such case.

But we will be interested in more distant objects. Let's start with the record. Steven Finkelstein and co -authors presented (Arxiv: 1310.6031) a reliable definition of red displacement for the most distant galaxy. Red displacement Z = 7.51 corresponds to the time of 700 million years after the start of the expansion. There are candidates for more distant objects, but for them there is no such reliable definition of red displacement (by which you can determine the distance).

But here not only this record result is important here. Молодая галактика обладает довольно высоким темпом формирования звезд-в сто раз выше, чем сейчас в нашей Галактике. При этом новый объект был обнаружен в небольшом обзоре. Получается, что эта галактика должна быть довольно типичной. Таким ообразом, еще до запуска нового космического телескопа или сверхбольших наземных телескопов мы начинаем узнавать, как выглядели галактики в первые сотни миллионов лет своего существования.

Однако на больших красных смещениях можно обнаружить настоящих монстров звездообразования. Доминик Ришер (Dominik Riechers) и его коллеги представили данные наблюдений далекой галактики с темпом образования звезд в 2000 раз больше, чем в нашей Галактике! Объект находится на красном смещении z = 6,34, что соответствует 880 млн лет после Большого взрыва. В этой галактике много пыли, и наблюдать ее пришлось в инфракрасном диапазоне с помощью космической обсерватории «Гершель».

8. Нейтрино сверхвысоких энергий

Как известно, из космоса к нам прилетают частицы высоких энергий — так называемые космические лучи. В основном это протоны, но могут быть и ядра более тяжелых элементов. Их энергия больше, чем у частиц в Большом адронном кол-лайдере в сотни миллионов раз! Но мы не знаем точно, откуда эти частицы летят. Знаем только, что им приходится преодолевать межгалактические расстояния. Почему же мы не можем определить источники? Дело в том, что заряженные частицы отклоняются магнитным полем. И хотя поля в нашей Галактике и, тем более, в межгалактическом пространстве очень слабы, зато частицы там находятся долго. К счастью, в природе есть и нейтральные частицы. Например нейтрино.

Поиск космических нейтрино сверхвысоких энергий является одной из основных задач установки IceCube в Антарктиде. Наконец-то группа исследователей представила первые положительные результаты (arxiv:1311.5238). Ими зарегистрировано почти три десятка событий с энергиями в 2-20 раз выше, чем на LHC. Немного, но и этого очень долго ждали. Пока статистики мало — рано говорить об отождествлении источников с какими-нибудь активными ядрами галактик или другими объектами. Но начало положено, поэтому будем ждать новостей.

9. Космология, реликтовое излучение

Наконец-то мы добрались до космологии. Здесь основные результаты связаны с изучением реликтового излучения. Посмотрим, как много астрофизики смогли узнать, занимаясь его изучением. Важно понимать, что основные космологические выводы основаны на большом количестве разнообразных, дополняющих друг друга данных, полученных конкурирующими группами, которые, вообще-то говоря, работали над тем, чтобы не столько подтвердить известное, сколько обнаружить что-то новое.

Давайте взглянем на очень красивый результат. Используя телескоп на Южном полюсе (South Pole Telescope), авторы сумели измерить (arXiv:1312.2462), как менялась температура реликтового излучения от z = 1,35 (4,7 млрд лет после Большого взрыва) до z = 0,05 (2/3 млрд лет назад). Таким образом ими был покрыт диапазон более 8 млрд лет жизни Вселенной.

В данной работе были использованы данные по 150 скоплений галактик. Эффект Зельдовича-Сюняева, связанный с взаимодействием фотонов реликтового излучения с электронами горячего газа в скоплениях галактик, позволяет измерить температуру реликта в ту эпоху, в которой мы видим скопление. Полученные результаты прекрасно укладываются на кривую, соответствующую стандартной космологической модели. Это хорошая новость, но надо двигаться дальше.

Для продвижения вперед ученые осваивают новые методики. На том же South Pole Telescope Дункан Хэн-сон (Duncan Hanson) с соавторами (arxiv:1307.5830) впервые измерили важную характеристику реликтового излучения. Это так называемая B-мода поляризации. Не будем углубляться в детали. Поясним лишь, насколько эта характеристика важна, что в ней закодировано.

Свет, распространяющийся к нам в течение почти 14 млрд лет, испытал влияние всего того, что встречалось ему по дороге. В частности, свет чувствует гравитацию массивных тел. Самое массивное — это крупномасштабная структура распределения галактик. Излучение линзируется — пусть и очень слабо- на этой структуре. Информация об этом оказывается «спрятанной» в B-моде поляризации.

Таким образом, потенциально эта характеристика может рассказать нам, как распределено вещество в больших масштабах на всем пути фотонов к нам, т.е. практически во всей видимой части Вселенной. Именно этот сигнал и начали «видеть» на South Pole Telescope. Чуть позже об аналогичном результате заявил проект POLARBEAR (arXiv:1312.6646). Для восстановления крупномасштабной структуры понадобится еще много работы, много наблюдений, но начало положено.

Мало того, в B-моде поляризации реликта скрыта еще и информация о первичных гравитационных волнах, рожденных в молодой Вселенной. Обнаружение этого сигнала позволило бы подтвердить инфляционную модель, что было бы крайне важно. Но для этого нужно нечто более мощное, чем телескоп на Южном полюсе: например спутник «Планк».

Команда «Планка» представила свои первые космологические результаты в марте 2013 года (arxiv:1303.5062, arxiv:1303.5076). Они вызвали большую дискуссию, продолжающуюся до сих пор (видимо, некоторую ясность внесет новый релиз данных в 2014 году). Дело в том, что хотя в целом «Планк» подтвердил стандартную космологическую модель, тем не менее, в деталях есть изменения по сравнению с результатами спутника WMAP.

Космологическая постоянная стала на несколько процентов меньше, доля темного вещества — на несколько процентов больше (за счет темной энергии). В чем причина этих расхождений — пока не ясно. В остальном всё стандартно. Вселенная плоская, сортов нейтрино — три.

Важно, что появились хорошие, пусть и недостаточно прямые, аргументы в пользу инфляционной модели (это удалось понять, изучив спектр первичных возмущений плотности, которые «отпечатались» в реликте). Теперь будем ждать, когда команда «Планка» сможет уточнить свои данные и дополнить их результатами измерения поляризации.

За новостями астрономии и астрофизики 2014 года вы можете следить по моим обзорам,публикующимся на странице ГАИШ МГУ: http://xray.sai.msu.ru/~polar/sci_rev/current.html .

Статья основана на материале С. Попова, опубликованном на сайте «Газета.Ру».