My Science School

At the center of our galaxy is a supermassive black hole in the region known as Sagittarius A. It has a mass of about 4 million times that of our Sun.

Almost every galaxy, including our Milky Way, has a supermassive black hole at its heart, with masses of millions to billions of times the mass of the Sun. Astronomers are still studying why the heart of galaxies often hosts a supermassive black hole.

Observations of several stars orbiting Sagittarius A*, particularly star S2, have been used to determine the mass and upper limits on the radius of the object. Based on mass and increasingly precise radius limits, astronomers have concluded that Sagittarius A* is the Milky Way's central supermassive black hole.

Reinhard Genzel and Andrea Ghez were awarded the 2020 Nobel Prize in Physics for their discovery that Sgr A* is a supermassive compact object, for which a black hole is the only currently known explanation.

In 2017, direct radio images were taken of Sagittarius A* and M87* by the Event Horizon Telescope. The Event Horizon Telescope uses interferometry to combine images taken from widely spaced observatories at different places on Earth in order to gain a higher picture resolution. It is hoped the measurements will test Einstein's theory of relativity more rigorously than has previously been done. If discrepancies between the theory of relativity and observations are found, scientists may have identified physical circumstances under which the theory breaks down.

 

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A bolide is an extremely bright meteor, especially one that explodes in the atmosphere. In astronomy, it refers to a fireball about as bright as the full moon, and it is generally considered a synonym for a fireball. In geology, a bolide is a very large impactor.

Many explosions recorded in Earth's atmosphere are likely to be caused by the air bursts that result from meteors exploding as they hit the thicker part of the atmosphere. These types of meteors are also known as fireballs or bolides with the brightest known as superbolides. Before entering Earth's atmosphere, these larger meteors were originally asteroids and comets of a few to several tens of metres in diameter, contrasting with the much smaller and much more common "shooting stars".

The most powerful recorded air burst is the 1908 Tunguska event. Extremely bright fireballs traveling across the sky are often witnessed from a distance, such as the 1947 Sikhote-Alin meteor and the 2013 Chelyabinsk meteor, both in Russia. If the bolide is large enough, fragments may survive such as the Chelyabinsk meteorite. Modern developments in infrasound detection by the Comprehensive Nuclear-Test-Ban Treaty Organization and infrared Defense Support Program satellite technology have increased the likelihood of detecting airbursts.

 

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Ethyl formate is an ester formed when ethanol (an alcohol) reacts with formic acid (a carboxylic acid). Ethyl formate has the characteristic smell of rum and is also partially responsible for the flavor of raspberries. It occurs naturally in the body of ants and in the stingers of bees.

This unlikely discovery was made by astronomers studying interstellar objects for new molecules. They had the IRAM radio telescope trained on Sagittarius B2 – a gas cloud at the centre of the Milky Way galaxy – when they found a chemical called ethyl formate. This is one of the aroma compounds that creates the sweet scents of fruit, wine and flowers, and it smells a lot like rum. It is also the chemical that gives raspberries their distinctive flavour.

Ethyl formate is made from ethanol – a common molecule found in star-forming gas clouds – with formic acid, which is a mix of hydrogen, oxygen and carbon atoms. It’s visible to radio telescopes because ethyl formate molecules absorb the radiation from the stars and re-radiate it at radio wavelengths. Ethyl formate molecules are some of the largest molecules ever found in space and are among the building blocks of amino acids, which are vital for life as we know it.

Even though Sagittarius B2 is extremely dense as far as star-forming regions go, it still only has around 3,000 molecules per cubic centimetre, compared to around 25 million trillion molecules per cubic centimetre in the air that we breathe on Earth. So, even if you could breathe in the nebula, it would sadly be too rarefied to actually smell the rum or taste the raspberries.

 

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Scientists have obtained the first image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun. This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity.

The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers reveal that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.

This breakthrough was announced today in a series of six papers published in a special issue of The Astrophysical Journal Letters. The image reveals the black hole at the center of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun.

The EHT links telescopes around the globe to form an Earth-sized virtual telescope with unprecedented sensitivity and resolution. The EHT is the result of years of international collaboration, and offers scientists a new way to study the most extreme objects in the Universe predicted by Einstein’s general relativity during the centennial year of the historic experiment that first confirmed the theory.

 

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Neutron stars are the smallest and densest stellar objects, excluding black holes and hypothetical white holes, quark stars, and strange stars. Neutron stars have a radius on the order of 10 kilometres (6.2 mi) and a mass of about 1.4 solar masses.

Neutron stars, with a solid crust (and even oceans and an atmosphere!) are the densest solid object we can observe, reaching a few times the density of an atomic nucleus at their core. A sample of neutron star material the size of a grain of sand would weigh roughly the same as the largest ship ever to sail the seas — more than 500,000 tonnes.

Neutron stars also offer a wealth of extreme behaviour which makes them a compelling target for astrophysicists. For the public, however, they seem to suffer from an image problem, lacking the visual appeal of objects that we can image directly, or the otherworldly weirdness of black holes.

Neutron stars comprise one of the possible evolutionary end-points of high mass stars. Once the core of the star has completely burned to iron, energy production stops and the core rapidly collapses, squeezing electrons and protons together to form neutrons and neutrinos. The neutrinos easily escape the contracting core but the neutrons pack closer together until their density is equivalent to that of an atomic nucleus. At this point, the neutrons occupy the smallest space possible (in a similar fashion to the electrons in a white dwarf) and, if the core is less than about 3 solar masses, they exert a pressure which is capable of supporting a star. For masses larger than this, even the pressure of neutrons cannot support the star against gravity and it collapses into a stellar black hole. A star supported by neutron degeneracy pressure is known as a ‘neutron star’, which may be seen as a pulsar if its magnetic field is favourably aligned with its spin axis.

 

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Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and the only naked-eye comet that can appear twice in a human lifetime. Halley last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.

Astronomy began changing swiftly around the time of Shakespeare, however. Many astronomers of his time held that Earth was the center of the solar system, but Nicolaus Copernicus — who died about 20 years before Shakespeare's birth — published findings showing that the center was actually the sun.

It took several generations for Copernicus' calculations to take hold in the astronomy community, but when they did, they provided a powerful model for how objects move around the solar system and the universe.

The comet appeared in 1531, 1607 and 1682. Halley suggested the same comet could return to Earth in 1758. Halley did not live long enough to see its return – he died in 1742 – but his discovery inspired others to name the comet after him.

On each successive journey to the inner solar system, astronomers on Earth turned their telescopes skyward to watch Halley's approach.

The comet's pass in 1910 was particularly spectacular, as the comet flew by about 13.9 million miles (22.4 million kilometers) from Earth, which is about one-fifteenth the distance between Earth and the sun. On that occasion, Halley's Comet was captured on camera for the first time.

 

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Ceres is the earliest known and smallest of the current category of dwarf planets. Sicilian astronomer Giuseppe Piazzi discovered Ceres in 1801 based on the prediction that the gap between Mars and Jupiter contained a missing planet. It is only 590 miles (950 km) in diameter and has a mass of just 0.015 percent that of Earth.

In fact, Ceres is so small that it is classified as both a dwarf planet and an asteroid, and is often named in scientific literature as one of the largest asteroids in the solar system. Although it makes up approximately a fourth of the mass of the asteroid belt, it is still 14 less massive than Pluto.

NASA's robotic Dawn mission arrived at Ceres in 2015. The mission has shown many interesting features on its surface, ranging from various bright spots to a 4-mile-high (6.5-kilometer-high) mountain. (Another mission, the European Space Agency's Herschel Space Observatory, spotted evidence of water vapor in 2014.) 

 

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Known as "the hexagon", this weather feature is an intense, six-sided jet stream at Saturn's North Pole. Spanning some 30 000 km across, it hosts howling 320 km/h winds that spiral around a massive storm rotating anticlockwise at the heart of the region.

Saturn, with its multiple rings, is sometimes referred as "The jewel of the Solar System". The hexagonal pattern at Saturn's North Pole had been shrouded in mystery for a long time. Some believe it to be natural phenomena, while others thought it to be the result of some alien activity. The spacecraft Cassini's dive into Saturn has given us a lot of photographs and information that comes very close to decoding this anomaly.

However, a team of scientists has created a new atmospheric model that suggests the storm is thousands of miles deep.

They tested the theory in a lab and think it deep roots could explain why the hexagon has been a feature on Saturn's surface for so long.

The 3D model was created by scientists at Harvard University.

It's based on previous storm hypotheses that claim jet streams in the gas giant planet's atmosphere or within its pressurised mass could be responsible.

Using their 3D spherical shell model, the researchers found that deep rotating changes in temperature between gasses on the planet could be causing the storm to form in that shape.

 

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Van Allen radiation belt, doughnut-shaped zones of highly energetic charged particles trapped at high altitudes in the magnetic field of Earth. The zones were named for James A. Van Allen, the American physicist who discovered them in 1958, using data transmitted by the U.S. Explorer satellite.

Van Allen's experiment on Explorer 1, which launched Jan. 31, 1958, had a simple cosmic ray experiment consisting of a Geiger counter (a device that detects radiation) and a tape recorder. Follow-up experiments on three other missions in 1958 — Explorer 3, Explorer 4 and Pioneer 3 — established that there were two belts of radiation circling the Earth.

While observations have continued for decades, our knowledge of the belts became more enhanced when the Van Allen Probes launched in 2012. They found that the belts were more complex than previously imagined. The probes showed that the shape of the belts depends on what particle is being studied. They also uncovered information hinting there is less radiation than imagined in certain parts of the Van Allen belts, which means spacecraft and humans would not need as much radiation protection if they are voyaging in that region.

 

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Created as surface ice vaporizes under the distant light of the Sun, Pluto’s atmosphere is predominantly nitrogen gas, along with small amounts of methane and carbon monoxide. Haze particles form high up in the atmosphere, more than 20 miles above the surface, as methane and other gases react to sunlight, before slowly raining down to the icy surface.

New Horizons found evidence of these particles when it sent back images showing a blue-tinted haze to Pluto’s atmosphere. Now, SOFIA’s data fills in even more details by discovering that the particles are extremely small, just 0.06-0.10 microns thick, or about 1,000 times smaller than the width of a human hair. Because of their small size, they scatter blue light more than other colors as they drift toward the surface, creating the blue tint.

With these new insights, scientists are reevaluating their predictions on the fate of Pluto’s atmosphere. Many forecasts indicated that as the dwarf planets moved away from the Sun, less surface ice would be vaporized — creating fewer atmospheric gases while losses to space continued — eventually leading to atmospheric collapse. But rather than collapsing, the atmosphere appears to change on a shorter cyclical pattern.

 

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The seventh planet from the Sun with the third largest diameter in our solar system, Uranus is very cold and windy. The ice giant is surrounded by 13 faint rings and 27 small moons as it rotates at a nearly 90-degree angle from the plane of its orbit. This unique tilt makes Uranus appear to spin on its side, orbiting the Sun like a rolling ball.

The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel, although he originally thought it was either a comet or a star. 

Uranus took shape when the rest of the solar system formed about 4.5 billion years ago, when gravity pulled swirling gas and dust in to become this ice giant. Like its neighbor Neptune, Uranus likely formed closer to the Sun and moved to the outer solar system about 4 billion years ago, where it is the seventh planet from the Sun.

As an ice giant, Uranus doesn’t have a true surface. The planet is mostly swirling fluids. While a spacecraft would have nowhere to land on Uranus, it wouldn’t be able to fly through its atmosphere unscathed either. The extreme pressures and temperatures would destroy a metal spacecraft.

Uranus has 27 known moons. While most of the satellites orbiting other planets take their names from Greek or Roman mythology, Uranus' moons are unique in being named for characters from the works of William Shakespeare and Alexander Pope.

All of Uranus' inner moons appear to be roughly half water ice and half rock. The composition of the outer moons remains unknown, but they are likely captured asteroids.

 

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There are more volcanoes on Venus than on any other planet in the solar system. Astronomers know of more than 1,600 volcanoes on its surface, but there are likely many more too small for us to see. Scientists think most of these are dormant, though a handful may still be active.

Even though there are over 1,600 major volcanoes on Venus, none are known to be erupting at present and most are probably long extinct. However, radar sounding by the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest volcano Maat Mons, in the form of ash flows near the summit and on the northern flank. Although many lines of evidence suggest that Venus is likely to be volcanically active, present-day eruptions at Maat Mons have not been confirmed. Nevertheless, other more recent studies, in January 2020, suggests Venus is currently volcanically active.

In 2020, a study by University of Maryland supported by Swiss National Science Foundation and NASA discovered that 37 of Venus coronae show signs of ongoing activity. Maryland professor Laurent Montesi said, "we are able to point to specific structures and say ‘Look, this is not an ancient volcano but one that is active today, dormant perhaps, but not dead..." The active coronae are clustered near each other, so positioning geologic survey instruments would now be easier.

 

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China’s Five-hundred-metre Aperture Spherical Radio Telescope (FAST) passed national evaluation and officially began operation in January 2020. With a dish the size of 30 football fields, it is the world’s largest single-dish radio telescope and the most sensitive listening device. The single-dish radio telescope is made of 4,450 individual panels.

The facility will help scientists learn more about the Universe’s early days, detect low-frequency gravitational waves and hunt for signals that may have been produced by distant alien civilizations.

• NASA’s Spitzer Space Telescope was retired in January 2020. Launched in 2003, Spitzer studied the universe in infrared light, revealing wonders of the Solar System, our galaxy, and beyond. Among its many scientific contributions, Spitzer studied comets and asteroids in the Solar System and found a previously unidentified ring around Saturn.


• In April 2020, the Hubble Space Telescope completed 30 years of service. Perched on the low Earth orbit, the telescope’s modest 2.4-metre mirror continues to give us an unprecedented window on the Universe. Thanks to Hubble and the Gaia space observatory, we were able to calculate the age of our Universe, which is approximately 13.8 billion years old. From observations from Hubble, we also learnt that black holes are at the centre of almost every major galaxy.

Did you know?

• NASA’s James Webb Space Telescope (JWST) is scheduled to be launched in October 2021. While it is touted as the successor of the Hubble Space Telescope, some scientists believe the two telescopes are actually complementary. Hubble has limited capabilities at near-infrared wavelengths, but it is best suited for observing in the ultraviolet and optical ranges of the light spectrum. Whereas James Webb is perfectly poised to study things in infrared range and these include formation of stars and planets, extremely distant galaxies, and even the atmospheres of exoplanets.


• The Hubble’s mission ends in 2021, unless NASA decides to extend it.

 

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NASA, the U.S. space agency, partnered with SpaceX, a private space company, to send astronauts to the International Space Station (ISS) in a commercially built and operated spacecraft. As part of this partnership, the first crewed test flight, Demo-2, was launched successfully on May 30, 2020, from NASA’s Kennedy Space Center in Florida. The SpaceX’s Crew Dragon spacecraft carried NASA astronauts Robert Behnken and Douglas Hurley on the company’s Falcon 9 rocket.

The Demo-2 mission has many firsts to its credit. SpaceX’s Crew Dragon, responsible for mission, is the first privately designed and built spacecraft to carry astronauts to space. The company has hitherto been delivering only cargo to the space station. The launch also marked the first time since the final flight space shuttle Atlantis in 2011 that NASA had sent from the U.S. soil. Ever since the retirement of Atlantis, human spaceflights to and from the ISS have been carried out using Russia’s Soyuz rocket.

With the success of Demo-2 NASA and SpaceX plant to launch the company’s first full mission with astronauts in October. Known as Crew-1, the mission will see three U.S. astronauts and one Japanese astronaut launch in a SpceX Crew Dragon capsule to the ISS.

 

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