Category Astronomy

The Orion Nebula, the brightest nebula in the sky and occupying an area twice the diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers.

The Orion Nebula’s position in our galaxy is well-known. If we could view the Milky Way from above, it would appear as a pinwheel with four spiral arms. The galaxy contains hundreds of billions of stars and massive amounts of gas and dust. Our solar system resides in the Orion Spur, which sits between the Perseus and Sagittarius arms, about halfway out from the galactic center.

Our earthbound view is different. On a clear summer night in the Northern Hemisphere, the Milky Way’s glow stretches from Cassiopeia in the northeast to Scorpius in the south. From this vantage point, we’re looking along the galaxy’s rim. Toward Scorpius is the central part of the Milky Way. Rather than seeing a field of blazing stars, our view is obscured by huge clouds of dust and gas.

In the winter, we see the sky opposite the stellar traffic jam found toward the galaxy’s center. The winter Milky Way is there, but you need a dark sky to see it with unaided eyes. The winter sky is the brightest of the seasonal skies — it contains the highest concentration of bright stars — and its most famous representative is Orion.

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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.

Picture Credit : Google

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.

Picture Credit : Google