July 2021 has been quite an exciting month in the arena of discoveries and advancements in physics and astronomy. It offered a variety on the plate, from discovering a swarm of black holes to achieving the fastest internet speeds. Here are some of the most exciting scientific adventures that humanity witnessed in July:

A swarm of black holes in Palomar 5

In a striking event, astronomers found a swarm of over 100 stellar-mass black holes hiding within a globular cluster named “Palomar 5” that lies 65,000 light-years away from us in the direction of the constellation Serpens.

Palomar 5 was discovered in 1950 and is one of the fluffiest known clusters to date. On average, the stars within the cluster are spaced up to 30,000 light-years away from each other. Like most other globular clusters, Palomar 5 was formed in the earliest phases of galaxy formation. However, in Palomar 5, the number of black holes found is roughly three times larger than expected from the number of stars in the cluster. Each black hole has a mass of about 20 times the mass of the Sun. And it is thought that they formed in supernova explosions at the end of the lives of massive stars when the cluster was still very young.

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Representational image of a globular cluster of stars | Image: NASA

With this, more than 20% of the total mass of Palomar 5 is coming from the black holes. The cluster is in the process of dissipating, which means that it is a host to tidal streams. To clarify, tidal streams are long streams of stars ejected from disrupting star clusters or dwarf galaxies. Simulations revealed that Palomar 5 likely formed with a lower concentration of black holes. As time passed by, stars escaped more easily than black holes from the cluster.

With this, the fraction of black holes to stars in the cluster increased tremendously. Moreover, the interaction between the black hole and the stars created gravitational slingshots, leading to the cluster’s fluffy appearance and caused even more stars to escape, fueling the exiting tidal stream. Thus, it is expected that in a billion years from now, just before the cluster completely dissolves, all the stars will escape, and the cluster will consist entirely of black holes.

Water vapors found in Ganymede’s atmosphere

In another breakthrough in astronomy, researchers have detected water vapors on Ganymede for the first time. The new findings have solidified the assumptions that water vapors exist in the atmospheres of icy bodies in the outer solar system.

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Ganymede, as photographed by Juno | Image: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

Previous studies had predicted that Ganymede contains more water than all of the Earth’s oceans. This made Ganymede a potential target in our hunt for extraterrestrial life. However, this Jovian moon is so cold that the water on its surface is completely frozen. And even if there exists any liquid water on Ganymede, it would lurk about 100 miles (160 kilometers) below its crust. This indicates that the detected water vapors are not an outcome of the evaporation of this ocean. So, where do these water vapors came from?

The answer to this question lies in the early studies that showed water vapors could directly form from solid ice instead of liquid water via a phenomenon know as sublimation on Ganymede. Although the presence of water vapors in Ganymede’s thin atmosphere was expected, this is the first time that a confirmation has been made.

The new inference has been made by analyzing the old and new data of Ganymede from NASA’s Hubble Space Telescope. In 1998, Hubble captured the first ultraviolet images of Ganymede. The ultraviolet signals detected in the moon’s auroral bands suggested the presence of oxygen molecules. However, some of the observed features did not match the expected emissions from an atmosphere consisting purely of molecular oxygen. Initially, it was concluded that the discrepancy was likely related to higher concentrations of atomic oxygen in Ganymede’s atmosphere.

To everyone’s surprise, Hubble hardly discovered any atomic oxygen there. This suggested that there must exist another explanation for the earlier ultraviolet signals. It is a known fact that Ganymede’s surface temperature varies strongly throughout the day. It can reach as high as about minus 190 degrees Fahrenheit (minus 123 degrees Celsius) at noon at the equator and drop as low as about minus 315 degrees Fahrenheit (193 degrees Celsius) at night.

Ice can become warm enough to convert directly into vapor at the hottest spots, thereby causing sublimation. It was noted that the differences in the UV images closely matched where one expected water in the moon’s atmosphere based on its climate.

Moon-forming disk around an exoplanet

For the first time, astronomers spotted a moon-forming disc around PDS 70c, an alien world lying only 370 light-years away from us.

Planets usually form in the dusty discs surrounding young stars. They carve out cavities in these discs and gobble up the material to grow as time goes by. But sometimes, in doing so, the planets also acquire their discs, which further contribute to their growth and ultimately lead to moons’ birth. Most of the exoplanets found to date have been confirmed either by NASA’s Transiting Exoplanet Survey Satellite (TESS) instrument or the dearly departed Kepler Space Telescope. Both these tools analyzed the dip in the host star’s luminosity as the planets transit in front of it.

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However, the PDS 70 system is not positioned to be detected by the transit method. Luckily, the system’s unique orientation allowed the European Southern Observatory’s Very Large Telescope (VLT) to observe the planetary disk and to look at PDS 70c and 70b with comparatively higher precision and in greater detail. Although there were some hints of PDS 70c having a Moon-forming region around it, this is the first time the disk has been confirmed. The image showed PDS 70c as a bright point inside a hazy proto-planetary disc. The disc has a diameter of about 1 AU, equal to the distance between the Earth and the Sun.

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This image, taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows wide (left) and close-up (right) views of the moon-forming disc surrounding PDS 70c, a young Jupiter-like planet nearly 400 light-years away. The close-up view shows PDS 70c and its circumplanetary disc center-front, with the larger circumstellar ring-like disc taking up most of the right-hand side of the image. The star PDS 70 is at the center of the wide-view image on the left. Two planets have been found in the system, PDS 70c and PDS 70b, the latter not being visible in this image. They have carved a cavity in the circumstellar disc as they gobbled up material from the disc itself, growing in size. In this process, PDS 70c acquired its own circumplanetary disc, which contributes to the growth of the planet and where moons can form. This circumplanetary disc is as large as the Sun-Earth distance and has enough mass to form up to three satellites the size of the Moon.

It is still not clear how much of this disc will eventually fall into the planet, but the ALMA data has revealed that there is quite a lot of matter floating around, enough to form three satellites equivalent to the size of Earth’s moon.

The PDS system is expected to offer a unique opportunity to observe and study planet and satellite formation processes.

Signs of life on Enceladus?

Enceladus is a fascinating place armored by a thick shell of ice. And in a new leap, astronomers have witnessed uncanny plumes spewed by Enceladus into the deep space that hints at signs of life on Saturn’s icy moon.

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The surface of Saturn’s moon Enceladus | Image: NASA

In 2014, Cassini discovered evidence of a large subsurface ocean on Saturn’s sixth-largest moon, Enceladus. Cassini found geysers of liquid water spraying from fractures in the icy shell at the moon’s south pole. This hinted at the presence of a salty liquid ocean below the icy surface. But the question was how a celestial body lying far away from the sun and covered with ice could sustain a liquid ocean! The answer to this question hinted at the presence of hydrothermal vents. These are the vents in the ocean floor from where the heat from the warm interior seeps into the surrounding ocean and helps in keeping it at a non-freezing temperature.

On Earth, these vents offer environments for life to flourish and are fascinating ecosystems. So, if hydrothermal vents are present on Enceladus, it hints at a pretty good possibility for the existence of life on the icy moon. Furthermore, the plumes were thought to contain water vapors, dihydrogen(H2), and various carbon-containing organic compounds, including methane (CH4).

On earth, H2 provides energy to some microbes to produce methane from carbon dioxide, in a process called methanogenesis. Surprisingly, the amount of methane found in the plumes seemed peculiarly high. Since Cassini also spotted carbon dioxide and methane, it further solidified the arguments in favor of methanogenesis on Enceladus.

However, there also existed a possibility that instead of biological processes like methanogenesis, some weird abiotic or geochemical processes might be producing methane and carbon dioxide on the moon. So to assess the probability of Enceladus’ methane being generated biologically, researchers built a series of mathematical models. The investigations found that the known abiotic and geochemical processes could not perfectly explain the methane concentrations observed by Cassini. However, on adding the contributions from methanogenic microbes, the observed concentrations were justified.

It must be noted that the new study does not specifically argue that life exists on Enceladus. It only hints at the possibility of microbial life existing in the icy world, among other prospects. It is still possible that the icy moon features some weird abiotic methane-producing reactions that aren’t known to us.

A population of “free-floating” planets is roaming in deep space

Astronomers have found enthralling evidence for a mysterious population of “free-floating” planets roaming in deep space in a recent breakthrough. Well, these are the planets that are not bound to their host star and are wandering out there. Instead, these objects have probably been ejected from the planetary system in which they were formed or have never been gravitationally bound to any star.

The recent observation was made using the data obtained in 2016 during the K2 mission phase of NASA’s Kepler Space Telescope. During the two-month campaign, Kepler analyzed millions of stars near the center of the Milky Way. As a result of Einstein’s theory of General relativity, stars can act as magnifying glasses for objects behind them. When one star in the sky appears to pass nearly in front of another, the light rays of the background source star bends due to the gravitational field of the foreground star. In this manner, the foreground star becomes a virtual magnifying glass and amplifies the brightness of the background source star.

The short burst in brightness can last from hours to a few days, depending upon the mass of the foreground star. And, the foreground star is referred to as the lens star, and the phenomenon is termed as lensing. Sometimes, even planets can act as lenses, although the effect is minimal, and the phenomenon is termed microlensing. Following this, Kepler made observations every 30 minutes to find rare gravitational microlensing events. Surprisingly, the team found 27 short-duration microlensing signals that varied over timescales of between an hour and 10 days. Although many of these signals had been previously seen, the four shortest events were witnessed for the first time.

Moreover, the new signals were consistent with planets having a similar mass as Earth and did not show an accompanying longer signal expected from a host star. This hinted at the possibility that these new events may be associated with free-floating planets. Thus, although Kepler was not designed to find planets using microlensing, it has provided tentative evidence for the existence of a population of Earth-mass, free-floating planets.

Physicists at CERN discovered a new particle

Particles physics and CERN never fail to amaze us. And as far as the latest discovery at CERN is concerned, physicists have discovered an exotic new particle that is quite exciting. The newly discovered particle, Tcc+, belongs to a rare class of particles called the tetraquarks. Moreover, it possesses an unusual composition which further makes it the longest-lived exotic hadron found so far.

These particles containing more than 3 quarks have been theorized for decades and have been discovered in recent years. Tcc+ is one of these exotic particles carrying four quarks, and that is why it is known as a tetraquark.

To be precise, this new particle contains two charm quarks along with an up antiquark and a down antiquark. This is quite a unique configuration. Because whenever quarks and antiquarks pair up, they usually do so within their flavor: i.e., a charm quark will pair up with a charm antiquark. But this is the first particle that has been found to have had charm quarks that aren’t paired up with their antiquarks. Because of this configuration, Tcc+ is also known as a “double open charm.”

The charm quarks are heavy, while the up and down antiquarks are comparatively lighter. This difference in masses slows down the decay process, making Tcc+  more stable and even the longest-lived exotic hadron known. However, If one or both of the charm quarks are swapped out for bottom quarks in a particle, that particle would last several orders of magnitude longer. So if such a particle is discovered in the future, Tcc+ will lose its title of being the longest-lived exotic hadron,

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Jupiter’s 40 year old mystery solved!

Jupiter has the most powerful aurorae in the solar system. Moreover, Jupiter is the only planet with aurorae that have been found to emit X-rays. The Jovian X-ray auroras often pulse-like clockwork, which means that the emissions occur in regular beats that can be a few dozen minutes long or even dozens of hours long.

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Overlaid images of Jupiter’s pole from NASA’s satellite Juno and NASA’s Chandra X-ray telescope. | Image: NASA Chandra/Juno Wolk/Dunn

Since their discovery about four decades ago, Jupiter’s X-ray auroral emission has fascinated planetary scientists. However, for 40 years, it wasn’t clear how the energy required to produce these energetic flares is generated! So to investigate the reason behind the gas giant’s pulsating X-ray auroras, researchers took the aid of computer simulations. The simulations suggested that this behavior might connect with Jupiter’s closed magnetic fields generated inside Jupiter and then stretch out millions of miles into space before turning back.

But no matter how elegant a computer model is, it always requires observational and experimental evidence to be accepted. So to check the authenticity of predictions made by the simulations, researchers turned to the data acquired by Juno and XMM-Newton from July 16 to 17, 2017. During these two days, XMM-Newton observed Jupiter continuously for 26 hours and saw X-ray aurora pulsating every 27 minutes. At the same time, Juno had been traveling between 62 and 68 Jupiter radii above the planet’s pre-dawn area. This was the same region that was pointed by simulations for triggering the pulsations.

Following this, the team searched the Juno data for any magnetic processes occurring at the same rate. And the results were promising! Juno found that solar wind particles directly strike the outer boundary of Jupiter’s magnetic field and compress it. The compressions heat the ions trapped in Jupiter’s extensive magnetic field, millions of miles away from the planet’s atmosphere.

Following this, the particles are directed along the field lines, triggering a phenomenon called electromagnetic ion cyclotron (EMIC) waves. As guided by the field, the ions ride the EMIC wave across millions of miles of space. Eventually, they slam into Jupiter’s atmosphere and trigger the X-ray auroras. This sums up the fact that Jupiter’s magnetic field fluctuations cause the pulsating X-ray auroras.

Japan broke the record by achieving fastest internet speed

Technological advancements are breaking barriers with each passing day, and Japan has taken a big leap in this regime. To put things into perspective, Japan has broken records for the fastest internet speed in history. The new speed is almost 7 million times faster than the average speed in the US and 24 million times faster than the average speed in India.

The never-seen-before speeds have been achieved in a lab by constructing a recirculating transmission loop set-up by combining two earth-doped fiber amplifiers. The researchers used advanced fiber-optic technology with a 4-core optical fiber of a standard outer diameter of 0.123 mm. The scientists were able to stretch the signal for more than 3,000 km with the combination of erbium and thulium-doped fiber amplifiers and distributed Raman amplification.

This test broke the previous record of 178 Tb/s that Japan and Britain set in 2020. 

Learn Astrophysics at Home

Did you always want to learn how the universe works? Read our 30-article Basics of Astrophysics series absolutely free of cost. From the popular topics such as stars, galaxies, and black holes to the detailed concepts of the subject like the concept of magnitude, the Hertzsprung Russell diagram, redshift, etc., there is something for everyone in this series. All the articles are given here. Happy reading!

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