From possibly spotting the farthest galaxy ever to confirming cryovolcanism on Pluto, April 2022 offered some significant insights into the secrets of the universe. Here is a list of the top five discoveries of April 2022 that you must know.

The most distant galaxy ever seen

In an astronomical breakthrough, Astronomers have spotted the most distant galaxy ever known. It has been named HD1 and lies 13.5 billion light-years away from us. This far-flung galaxy is expected to contain some of the universe’s first stars along with a supermassive black hole at its center.

The detection was confirmed after a careful analysis of data collected during the 1,200 hours of observation cycle with the Subaru Telescope in Hawaii, VISTA Telescope in Chile, the U.K. Infrared Telescope, and the Spitzer Space Telescope (now retired). Further, the follow-up observation campaigns were conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, which confirmed the galaxy’s record-breaking distance.

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This picture shows HD1 (in red) at the center of a zoom-in image | Image: Harikane et al.

However, HD1 is a mystery in itself. The galaxy is extremely bright in ultraviolet wavelengths. This suggests that some extremely energetic processes are occurring in the galaxy. At present,  scientists have two plausible theories to explain these emissions. It could either be a herculean starburst galaxy or a mighty quasar.

A starburst galaxy is one with an exceptionally high star formation rate or SFR for short. The star formation rate is an important parameter in galactic and extra-galactic astronomy. A starburst is a phase in a galaxy’s evolution that can happen for different reasons.

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The Antennae Galaxies | Image: Hubble/ESA

Even galactic interactions can lead to a starburst, like in the case of the antennae galaxies. These two galaxies have been merging for the past 100 million years, and their star formation rate has skyrocketed because of the interaction. In the image above, the blue regions represent high star formation activity.

High SFR rates make a galaxy luminous, so astronomers calculated the number of stars that would have to be forming to produce that much light. And it came out to be 100 per year. That’s ten times what you would expect for a galaxy this old. However, there’s an explanation for this. The first generation of stars formed was significantly hotter and more luminous than the modern stars. If that is the case, we might be looking at the light from the so-called population III stars with little to no elements other than hydrogen and helium.

The second possibility is that the luminosity is because of a mighty quasar. A quasar is the most powerful object in the Universe. This active galactic nucleus involves a supermassive black hole feasting on the surrounding material at such a rate that the heat generated blazes of light across the Universe. The team calculated the size of the supermassive black hole required to match the observed luminosity of HD1, and the results were surprising.

They found that the black hole had to be 100 million times more massive than the Sun. That’s a lot of mass, given the period we are talking about. Three hundred thirty million years after the big bang is too soon for a black hole to become so massive. If it indeed is a quasar, it must have grown out of a gigantic seed at an unprecedented rate. This poses a significant challenge to the current black hole models.

The team hopes that future observations with the James Webb Space Telescope, a machine optimized for peering into the early Universe, will reveal the nature of this mysterious dawn light with its advanced infrared capabilities.

Micronova: A mini version of a typical nova

Astronomers have discovered a new kind of explosion on the surface of active white dwarfs, termed micronova. This stellar explosion occurs specifically in systems where the white dwarf is actively slurping down material from a close binary companion and is known to burn down tens to hundreds of quintillions of kilograms of stellar material in hours.

In a typical white dwarf nova, when stars in a binary system whirl around each other, hydrogen from the smaller companion gets aggressively gulped by the smaller, denser, and more massive white dwarf. When this hydrogen accumulates on the white dwarf’s surface, it gets heated up. When the mass on the surface becomes high enough that the pressure and temperature at the bottom of the layer are sufficient to trigger a thermonuclear explosion, the white dwarf violently expels the excess material into space, thereby causing a nova.

Researchers believe a micronova is a mini version of the nova and occurs when the excessive material is channeled to the white dwarf’s poles by its magnetic field. And when sufficient material gets accumulated on the poles, they result in causing outbursts that are similar to the typical white dwarf nova but at a smaller scale.

For over the last 40 years, one of the white dwarfs in the TV Columbae binary system has exhibited such flashes. Similar bursts have also been reported on other highly magnetized white dwarfs. The discovery of micronova is expected to explain these phenomena and play a crucial role in understanding the thermonuclear outbursts on dead stars in a better manner.

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Pluto is still alive!

New research has claimed that Pluto might be home to some exotic and active volcanoes that don’t spew out lava like the usual volcanoes. Instead, they throw out ice, water, and ices of gases like methane, which rightfully earns them the name the “ice volcanoes.”

The revelation came after a team of researchers analyzed the data from New Horizons’ July 2015 flyby of Pluto. The spacecraft had pictured two mysterious peaks towering over the dwarf planet’s surface. The first one is a 150 km wide mountainous feature called Wright Mons, and the second is a feature named Piccard Mons, which rises to a height of almost 7 kilometers and has a width of around 225 kilometers.

Both these surface features sit at the southwest edge of the Sputnik Planitia ice sheet, which is dominated by folds and rises, appearing like wrinkles over a smooth cover of ice. A careful analysis has shown that such terrain can only be fueled by multiple eruption sites located near each other. This means that possibly, some cryovolcanic eruptions occurred on Pluto, and the material ejected during these eruptions coated the entire region with layers over layers of ice.

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3-D topographic maps showing Wright Mons and Piccard Mons | Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Moreover,  the surface material in this region is primarily water-ice instead of nitrogen or methane ice found in other younger parts of the planetary surface. This further solidifies the possibility of cryovolcanic activity. However, for a body to be volcanically active, it must have a legit heat source driving the eruptions. And for Pluto, the source of this energy is possibly the leftover heat that got trapped during its formation.

As the New Horizon only made a flyby and observed the planet just for one day, it’s still difficult to confirm if cryovolcanism is still active on Pluto or if the exotic ice volcanoes have become dormant. But if it is still active, it would strengthen the possibility of finding a liquid ocean and life on Pluto.

Two different speeds of sound on Mars

New data from Perseverance has revealed that sound waves travel more slowly on Mars than on Earth. But along with that, sound waves also have two different speeds on Mars, with lower-pitched sounds traveling more slowly than higher-pitched ones.

The speed of sound depends on a range of factors, including the density of the material through which the sound waves travel.  As Mars’ atmosphere is over 100 times thinner than Earth’s, the sound was expected to travel slowly through it. However, the two different sound speeds came as a surprise to the researchers. To explain this strange behavior, scientists considered the thermal fluctuations in the first 10 kilometers of Mars’ atmosphere above the planet’s surface and the behavior of carbon dioxide molecules in the atmosphere.

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The SuperCam instrument (upper right) on NASA’s Perseverance rover | Image: JPL-CALTECH/NASA, MSSS

During the day, as the sun’s rays hit the Martian surface, convective drafts and turbulence stir this specific layer of the Martian atmosphere, eventually changing the behavior of carbon dioxide molecules. But at frequencies above 240 Hz, the collision-activated vibrational modes of carbon dioxide molecules don’t have enough time to relax or return to their original state,  which results in sound waves at higher frequencies traveling more than 32 feet per second.

This would make the higher-pitched sounds arrive sooner to the listener than the lower-pitched ones. The team plans to continue using SuperCam microphone data to understand the factors affecting the speed of sound on Mars in more detail.

A ‘missing link’ black hole

While browsing through the archival data from the Hubble Space Telescope, astronomers have spotted GNz7q. This ancient black hole existed only some 750 million years after the Big Bang and is expected to hold the missing link between supermassive black holes and quasars.

GNz7q sits at the core of a dusty starburst galaxy and was found lurking through the Great Observatories Origins Deep Survey-North (GOODS-N) field, which is a famous and well-studied sky field. GNz7q marks the first-ever observation of a rapidly growing black hole in the early universe.

Supermassive black holes are born in the hearts of dusty and actively star-forming galaxies. Over the years, they throw off the surrounding shroud of gas and dust and begin to appear as highly luminous cosmic objects called quasars. At present, the inner portion of GNz7q’s accretion disk is obscured with the outer part is just beginning to reveal itself. If this scenario is confirmed, it would mean that GNz7q is passing through a critical transitional stage that has only been predicted by theoretical models so far.

Now, the researchers aim to use the James Webb Space Telescope to examine the early universe in a better way and find more such possible missing links.

Have you ever wondered?

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