#celestial_objects

Hubble's image of spiral galaxy NGC 6951 shows its bright blue spiral arms, bars, patches of star clusters, and clumps of dust. The galaxy NGC 6951, which lies 78 million light-years from Earth, was captured in a new Hubble image created by the Wide Field Camera (WFC3) and the Advanced Camera for Surveys (ACS). The image shows bright blue spiral arms, star clusters, and a dark orange dust cloud. [caption id="attachment_64740" align="aligncenter" width="780"] spiral galaxy NGC 6951[/caption] The history of this galaxy is quite amazing. About 800 million years ago, NGC 6951 was known for its high rate of star formation, but then star formation stopped for 300 million years. Over the past 25 years, six powerful supernova explosions have occurred, causing the extinction of some of these stars. The average age of a star cluster in the galaxy is between 200 and 300 million years, but some have reached the age of one billion years. An angle straight to the heart: Hubble captured a detailed image of the spiral galaxy NGC 6951 NGC 6951 is classified as a Type II Seyfert galaxy due to its infrared emission and the presence of a slow-moving gaseous environment at the center. However, some astronomers also consider it to be a low-ionization galaxy with an emission line in the core, implying a cooler and less ionized core. Near the center of the galaxy lies a supermassive black hole, which is surrounded by a ring of stars, gas, and dust with a diameter of about 3,700 light years. This ring is also known as the "central ring" and is thought to have star formation for 1 to 1.5 billion years, with 40% of its mass consisting of stars less than 100 million years old. This image of NGC 6951 is part of NASA's Hubble Photo Sharing Campaign, which features new images taken by the space telescope every day from October 2 to October 7.

Scientists from Italy and Germany have discovered exoplanet GJ 367b, which is likely composed entirely of iron. Using the HARPS spectrograph and TESS observations, they found that more than 90% of the planet's mass is made up of its iron core. Researchers from the University of Turin in Italy and the State Star Observatory of Thuringia in Germany have made an interesting discovery: the exoplanet GJ 367b is most likely composed entirely of iron.  This makes it the densest known planet with a short orbital period. GJ 367b was first spotted in 2015 by NASA's TESS (Transiting Exoplanet Survey Satellite) space telescope and has a density 1.85 times that of Earth. [caption id="attachment_69273" align="aligncenter" width="780"] GJ 367b[/caption] Using the European Southern Observatory's HARPS spectrograph and TESS observations, scientists determined that more than 90% of the planet's mass is made up of its iron core. The origin story of GJ 367b remains a mystery, but it may have once been a rocky planet like Earth or Mars. Its two neighboring planets, orbiting further out, are also rocky, indicating that they all formed in a similar way. GJ 367b is an exoplanet consisting only of an iron core However, GJ 367b likely went through a unique series of events that led it to lose its outer rocky layers, leaving only the core. Possible explanations include collisions with another planet closer to the host star. Another possibility is that GJ 367b was intensely irradiated by its star, causing its outer layer to burn away leaving only an iron core. The outer material could turn into gas and then be dispersed into space. It is also possible that GJ 367b underwent a combination of collisions and irradiation to form the metallic planet that astronomers observe today. The question still remains: how did GJ 367b get so close to its star? It is unlikely that it formed there. Scientists believe that gravitational interactions with other planets could have caused it to move away from its original formation site. Further study of GJ 367b could provide valuable insights into the formation and evolution of rocky and short-period planets.

The problem arose when one of the three gyroscopes gave incorrect readings. The team is working to fix the problem, but for now all scientific missions are suspended NASA has suspended all current science missions of the Hubble telescope due to a gyroscope malfunction. The problem arose on November 19, when the telescope went into safe mode after one of its three gyroscopes gave erroneous readings. The team quickly resumed work after fixing the problem, but the unstable gyroscope attracted attention twice, causing the telescope to go into safe mode again on November 21 and 23. After the incident on November 21, the agency was able to restore operations. However, on November 23, the telescope went into safe mode again, prompting NASA to suspend all science missions until the cause was determined. [caption id="attachment_85327" align="aligncenter" width="780"] Hubble Telescope[/caption] Hubble Telescope temporarily suspends science missions due to faulty gyroscope Gyroscopes are important components of the Hubble Telescope, helping to measure its rotation speed and determine its direction. The NASA team is actively working to determine the cause of the gyroscope malfunction. The gyroscopes were last replaced during the shuttle's fifth and final executive mission in 2009. Six gyros were replaced as part of this mission, and the faulty gyro is one of three that are still operational. Despite the need for another service mission, NASA believes Hubble will continue to make breakthrough discoveries with the James Webb Telescope for the rest of this decade, and possibly well into the next. The space agency has not released details about when it hopes to return Hubble to service once the gyroscope problem is fixed. Even if you need to turn off the faulty gyroscope, the telescope will be able to continue working, since NASA claims that for Hubble to continue moving and participate in scientific missions, one working gyroscope is enough. Hubble launched in 1990 and spent 33 years exploring our Universe, giving us iconic views of the cosmos, including a spectacular view of the Creation Pillars, which was also photographed by astrophotographers and the James Webb Telescope.

The research team studied the planetary nebula's central star in the star cluster, determining that it had lost 70% of its mass over its lifetime. It also turned out that the star has an unusual chemical composition and does not contain hydrogen. Stars like our Sun end their lives as white dwarfs. Some of them are surrounded by a planetary nebula, consisting of gas ejected by a dying star just before the outburst. An international research team led by Professor Klaus Werner from the Institute of Astronomy and Astrophysics at the University of Tübingen studied the central star of a planetary nebula located in an open star cluster. Scientists were able to accurately determine the mass that the central star lost during its life. There are more than a thousand open star clusters in our Galaxy. Each of them includes up to several thousand stars that were formed from a dense cloud of gas and dust. “The stars in the cluster are of the same age, and this is of particular importance for astrophysics,” says Klaus Werner. They differ only in their mass. “The greater the mass of a star, the faster it consumes its nuclear fuel, burning hydrogen into helium. So the life of a large star is shorter and it turns into a white dwarf faster,” he explains. [caption id="attachment_68877" align="aligncenter" width="780"] nebula Messier 37[/caption] Observation of a star cluster shows the development of stars of different masses at the same age. “In astronomy, star clusters can be used as a kind of laboratory where we can test how correct our theories of stellar development are. One of the most uncertain aspects of the theory of stellar development is how much matter a star loses during its life. Stars like our Sun lose almost half their mass by the time they become white dwarfs. Stars eight times heavier than the Sun lose about 80% of their mass,” says the astrophysicist. The mass of white dwarfs in star clusters can be directly related to their mass at birth. Data on very young white dwarfs is especially valuable because they are the central stars of planetary nebulae. But none of their central stars in such nebulae have been studied before because they are all very distant and dim. The research team pointed one of the world's largest telescopes, the ten-meter GRANTECAN telescope, at the central star in the Messier 37 cluster and analyzed its spectrum. They were able to determine the star's mass to be 0.85 solar masses, meaning an original mass of 2.8 solar masses. How the central star of the planetary nebula Messier 37 survived the loss of 70% of its mass “The star thus lost 70% of its matter during its lifetime,” explains Werner. Another feature is its special chemical composition. There is no longer any hydrogen left on its surface. This points to an unusual event in its recent past - a short-term burst of nuclear reactions. The ability to accurately determine the start-to-end mass relationship of a star is of fundamental importance in astrophysics. It determines whether a star becomes a white dwarf, becomes a neutron star during a supernova, or becomes a black hole at the end of its life. From the ejected matter at the moment of “rebirth” of the star, new generations of stars are formed, enriched with heavy elements as products of nuclear reactions. The chemical evolution of galaxies, and ultimately the entire Universe, depends on this.

Using computer models, scientists were able to simulate the formation of intermediate-mass black holes in star clusters. This opens up new ways to study mysterious objects The Universe is teeming with black holes from stellar masses to supermassive monsters. But there is one class that remains elusive: “average” black holes. They are called intermediate-mass black holes. How common are they, how are they formed and where are they located? To answer these questions, astronomers modeled possible formation scenarios. Intermediate-mass black holes lie in the mass gap between stellar mass and a supermassive black hole. They range from 100 to 100,000 solar masses. If they exist, do they indicate a hierarchical model of black hole formation and do small black holes form from the collapse of supermassive stars? If this is so, then intermediate-mass black holes will be a kind of “transition link” between stellar mass and supermassive black holes. If this idea is correct, then is it possible that intermediate-mass black holes could collide with each other and form the seeds of supermassive black holes? Astronomers need more observational data to answer all these questions. [caption id="attachment_68861" align="aligncenter" width="780"] star clusters[/caption] At the same time, astronomers have enough data on stellar-mass black holes. They are formed during the collapse of supermassive stars. Supermassive black holes located at the centers of galaxies are most likely formed through the accretion of matter, as well as mergers with other black holes. The existence of intermediate-mass black holes appears to be beyond doubt, but their observation presents certain difficulties. This doesn't mean they don't exist. Observers have found candidates for intermediate-mass black holes in the Milky Way. They also appear to be present in active galactic nuclei, where accretion effects are observed. Additionally, some ultraluminous X-ray sources may also have these "average" black holes. The Sloan Digital Sky Survey also found several potential candidates that emit strongly in the X-ray range. X-ray emission is one of the characteristics of activity around a black hole. One of the most interesting observations involves the gravitational waves emitted when two massive black holes merge. As a result, a black hole with a mass of about 150 solar masses was formed - exactly the kind of mass that can be classified as intermediate. Simulation reveals secret of origin of intermediate-mass black holes in star clusters Scientists are sure they exist, but still cannot determine exactly where and how they are formed. An international group led by Arca Sedda from the Gran Sassa Institute (Italy) modeled the possible mechanisms of their formation.  [caption id="attachment_68862" align="aligncenter" width="451"] star clusters[/caption] “Current observational limitations do not allow us to say anything definitive about the population of intermediate-mass black holes with masses between 1,000 and 10,000 solar masses, and they cause headaches for scientists regarding the possible mechanisms of their formation,” Sedda explained. Sedda and his team looked at star clusters as possible birthplaces for intermediate-mass black holes, and they created computer models that could simulate the formation of these mysterious objects using DRAGON-II data. This is a collection of 19 computer models representing dense clusters of up to a million stars each. Using these in further simulations, the team discovered that the objects they were interested in could form star clusters. This occurs due to a complex combination of three factors: mergers between stars much more massive than the Sun, accretion of matter from the star onto stellar-mass black holes, and mergers between stellar-mass black holes. "The latter process makes it possible to 'see' these phenomena through the detection of gravitational waves," Sedda explained. The team also hypothesized what happens after the birth of intermediate-mass black holes. They appear to be ejected from their clusters by complex gravitational interactions, or experience "relativistic recoil" when formed. This keeps them from gaining weight.  “Our models show that although seeds form naturally from interactions in star clusters, they are unlikely to become heavier than a few hundred solar masses unless the parent cluster is extremely dense or massive,” Sedda said. Finding out the history of the origin of these black holes still does not answer the question of whether they are the missing link between stellar and supermassive black holes. For a better understanding, we need two ingredients: one or more processes capable of forming black holes in the intermediate mass range and the ability to preserve such black holes. Our study places strict constraints on the first ingredient, providing clear insight into what processes may contribute to the formation of intermediate-mass black holes. Looking at more massive clusters containing more binary star systems in the future may be the key to obtaining the second ingredient. But this will require enormous effort from a technological and computational point of view.

The absence of white dwarfs in the Hyades cluster is of interest to astronomers, and this case helps reconstruct the history of the cluster The Hyades star cluster is located about 153 light years away. At such a short distance it is visible to the naked eye in the constellation Taurus. THIS proximity makes it easier for professional astronomers to observe than many other objects. The Hyades cluster contains many stars with approximately the same age - about 625 million years, the same metallicity, and similar trajectories. But it lacks white dwarfs - there are only eight of them in the center of the cluster. The Hyades cluster is quite common. His research greatly helps in understanding star clusters. But such a feature as the almost complete absence of white dwarfs puzzles astronomers.  A new study has found one "escapee" from the cluster. This is a white dwarf whose mass is approaching the limiting value for this type of star. The study is called "A White Dwarf That Was Able to Escape the Hyades Star Cluster." [caption id="attachment_68737" align="aligncenter" width="769"] star cluster[/caption] An extremely massive white dwarf was able to escape the Hyades star cluster Clusters such as the Hyades are weakly gravitationally bound, and over time they lose stars through their interactions with gas clouds, other clusters, and between the cluster stars themselves. Study author David Miller of the Department of Physics and Astronomy at the University of British Columbia and his co-authors studied the phenomenon of the absence of white dwarfs in the Hyades to reconstruct the history of the cluster. If we can identify the stars that were expelled, especially white dwarfs in this case, then it is possible to reconstruct the history of the cluster. The European Space Agency's Gaia space telescope tracks more than 1 billion stars in the Milky Way, providing Miller and his colleagues with a huge amount of data. The team found three white dwarfs with trajectories indicating possible escape from the Hyades cluster. For two of them, the range of masses makes it unlikely that they originated in a cluster, but for the third object, it is possible. "We estimate there is a 97.8% probability that the candidate is a true native of the Hyades" White dwarfs have a mass comparable to the Sun, but their size is comparable to the Earth. They consist of degenerate matter and emit only residual thermal energy. This is the final state of about 97% of the stars in the Milky Way. Their mass is governed by the Chandrasekhar limit and at maximum can reach about 1.44 solar masses. Large white dwarfs are usually found in binary star systems and gain mass by pulling matter from a companion; such white dwarfs eventually explode in a type 1a supernova, and all their mass is dissipated. [caption id="attachment_68738" align="alignnone" width="780"] star cluster[/caption] The white dwarf that left the Hyades is called an ultramassive white dwarf. These have a mass of 1.10 or more solar masses. This is well below the Chandrasekhar limit, but well above the average mass of a white dwarf, which is about 0.6 solar masses. Such high-mass objects typically originate from two-parent stars in a binary system, where one star has "taken" material from the other, increasing its mass. However, the Hyades ultramassive white dwarf has a mass of 1.317 solar masses and an age consistent with only one parent star. It appears to be the most massive white dwarf to come from a single progenitor.

Astrophysicists have discovered that the young star cluster IRS13 near the supermassive black hole Sagittarius A* is much younger than expected. The IRS13 cluster migrated to the black hole due to friction with the interstellar medium and collisions with other clusters An international team led by Dr. Florian Peisskei from the Institute of Astrophysics at the University of Cologne has studied in detail a young star cluster near the supermassive black hole Sagittarius A* (Sgr A*) at the center of our galaxy and found that it is much younger than previously estimated. This cluster, known as IRS13, was discovered more than twenty years ago, but only now has it been possible to identify its components in detail by combining a wealth of data collected using different telescopes over several decades. The stars inside the cluster are several hundred thousand years old—they are extremely young by the standards of stellar life. For comparison, our Sun is about 5 billion years old. The galaxy's high-energy radiation and tidal forces make it surprising to have so many young stars near a supermassive black hole. [caption id="attachment_65577" align="aligncenter" width="453"] IRS13 star[/caption] Young stars near a black hole: the mystery of the IRS13 star cluster near Sagittarius A* The study used observations from the James Webb Space Telescope (JWST) to record a spectrum free from interference from the galactic center. This spectrum reveals the presence of water ice in the galactic center. This water ice, which is often found in dusty disks around very young stars, was another independent indicator of the youth of some stars near the black hole. In addition to JWST's unexpected discovery of young stars and water ice, the researchers also discovered that IRS13 has a turbulent formation history. The results of the study suggest that IRS13 migrated to the supermassive black hole under the influence of friction with the interstellar medium, collisions with other star clusters, or internal processes. And then this star cluster was attracted by the gravity of the black hole. The process also created a compacted formation at the “top” of the cluster due to the dust surrounding the cluster. The increase in dust density stimulated further star formation. This explains why young stars are found mostly at the "top" or front of the cluster. “The analysis of IRS13 and interpretation of the history of this cluster is the first attempt to resolve a decades-old mystery about unexpectedly young stars at the galactic center. In addition to IRS13, there is another star cluster - the so-called S-cluster, which is even closer to the black hole and also consists of young stars. They are also much younger than is possible according to accepted theories,” says Dr. Paisskea. The results obtained about the IRS13 star cluster provide an open opportunity for further studies of the relationship between proximity to the black hole and regions several light years away. The second author of the study, Dr Mišal Zajaček from Masaryk University in Brno (Czech Republic), added: “The IRS13 star cluster appears to hold the key to the origin of the dense stellar population at the center of our galaxy. We have collected extensive evidence that very young stars within the range of a supermassive black hole could form in star clusters such as IRS13. This is also the first time we have been able to identify stellar populations of different ages - hot main sequence stars and young embryonic stars in a cluster so close to the center of the Milky Way."

James Webb showed that bright galaxies in the early universe are the result of intense star formation and not a failure of the standard model of cosmology. Computer simulations have confirmed that these galaxies become bright due to bursts of star formation Bright galaxies discovered by the James Webb Space Telescope (JWST) in the early Universe may be the result of bursts of massive star formation. And this probably makes galaxies brighter for a particular era of their existence than expected. This conclusion was reached by researchers who created computer simulations of the birth of these galaxies and the beginning of star formation. When JWST began observing in the summer of 2022, its observations of the universe quickly revealed high-redshift galaxies. These are galaxies that seemed to exist in the universe before astronomers had ever seen them. Galaxies that were visible when the universe was less than 400 million years old turned out to be brighter than the standard model of cosmology predicts for that epoch. This has led to claims that the standard model, which describes "beginning" as small galaxies and their hierarchical growth through mergers, must be wrong. [caption id="attachment_63725" align="aligncenter" width="780"] galaxies[/caption] James Webb solved the mystery of bright galaxies in the early Universe “The discovery of these galaxies was a big surprise because they were much brighter than expected. Usually, a galaxy is bright because it is large, but since these galaxies formed early in the life of the Universe, not enough time has passed since the Big Bang. How did these massive galaxies form so quickly?" says Claude-André Faucher-Gigour, part of a team led by Guochao Sun at Caltech that created simulations of the formation of the first galaxies. They found that the galaxies observed by JWST are not large, but bright because they were observed during periods of active star formation. The simulations allow us to simulate not only the brightness of galaxies but also their density distribution, which is fully consistent with JWST observations. Such bursts of activity are not unusual. Astronomers sometimes see them happening in modern galaxies—when galaxies merge. This process can cause the gas to mix in such a way that gravity grabs it and causes it to fragment and collapse, forming many stars at once. In the early Universe, where the environment was quite unstable, the first galaxies could not accumulate all their star-forming matter evenly. We think that the following process occurs: groups of stars appear, and after a few million years these stars explode in the form of a supernova. Gas is ejected [from the galaxy] and then pulled back to form new stars, maintaining the star formation cycle. In the early Universe, galaxies were much smaller than they are today and grew in part by accumulating clouds of intergalactic gas, but also by merging with other galaxies. The larger they became, the more gravity they had. And so they reached a point where they could accumulate more material to form stars. This stabilized the rate of star formation, and today galaxies such as our Milky Way form stars at a more relaxed pace.