Category: astrophysics

The VISIR instrument on ESO’s VLT captured thi…

The VISIR instrument on ESO’s VLT captured this stunning image of a newly-discovered massive binary star system. Nicknamed Apep after an ancient Egyptian deity, it could be the first gamma-ray burst progenitor to be found in our galaxy.

Apep’s stellar winds have created the dust cloud surrounding the system, which consists of a binary star with a fainter companion. With 2 Wolf-Rayet stars orbiting each other in the binary, the serpentine swirls surrounding Apep are formed by the collision of two sets of powerful stellar winds, which create the spectacular dust plumes seen in the image.

The reddish pinwheel in this image is data from the VISIR instrument on ESO’s Very Large Telescope (VLT), and shows the spectacular plumes of dust surrounding Apep. The blue sources at the centre of the image are a triple star system — which consists of a binary star system and a companion single star bound together by gravity. Though only two star-like objects are visible in the image, the lower source is in fact an unresolved binary Wolf-Rayet star. The triple star system was captured by the NACOadaptive optics instrument on the VLT.

Credit: ESO/Callingham et al.

New computer simulations are giving scientists…

New computer simulations are giving scientists a ringside seat to observe the effects of unimaginably powerful electric and magnetic fields generated by pulsars, the fast-spinning, collapsed cores left over from supernova explosions, that spew out a complex web of charged particles and radiation.

The simulations, carried out on NASA supercomputers, let the researchers “explore the pulsar from first principles,” said Constantinos Kalapotharakos of NASA’s Goddard Space Flight Center. “We start with a spinning, magnetised pulsar, inject electrons and positrons at the surface, and track how they interact with the fields and where they go. The process is computationally intensive because the particle motions affect the electric and magnetic fields and the fields affect the particles, and everything is moving near the speed of light.”

The simulations show electrons tend to stream outward from the pulsar’s magnetic poles while positrons, their anti-matter counterparts, mostly flow out from lower latitudes and form a structure known as a current sheet. Some of the particles in the current sheet where the pulsar’s magnetic field “reconnects,” converting magnetic energy into heat, are accelerated to extreme velocities.

source – video

On that day in 1873 was born the physicist and…

On that day in 1873 was born the physicist and astronomer Karl Schwarzschild

He provided the first exact solution to the Einstein field equations of general relativity, for the limited case of a single spherical non-rotating mass, which he accomplished in 1915, the same year that Einstein first introduced general relativity. The Schwarzschild solution, which makes use of Schwarzschild coordinates and the Schwarzschild metric, leads to a derivation of the Schwarzschild radius, which is the size of the event horizon of a non-rotating black hole.

Schwarzschild accomplished this while serving in the German army during World War I. He died the following year from the autoimmune disease pemphigus, which he developed while at the Russian front. Various forms of the disease particularly affect people of Ashkenazi Jewish origin.

Asteroid 837 Schwarzschilda is named in his honour, as is the large crater Schwarzschild, on the far side of the moon. (source) (biography) (more)

On this day in 1873 was born the  chemist and…

On this day in 1873 was born the 

chemist and astronomer Ejnar Hertzsprung

Ejnar Hertzsprung (8 October 1873 – 21 October 1967) was a Danish chemist and astronomer born in Copenhagen. In the period 1911–1913, together with Henry Norris Russell, he developed the Hertzsprung–Russell diagram. (read more)

The Hertzsprung–Russell diagram, abbreviated H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars’ absolute magnitudes or luminosities versus their stellar classifications or effective temperatures. More simply, it plots each star on a graph measuring the star’s brightness against its temperature (color). It does not map any locations of stars. The related colour–magnitude diagram (CMD) plots the apparent magnitudes of stars against their colour, usually for a cluster so that the stars are all at the same distance.

The diagram was created circa 1910 by Ejnar Hertzsprung and Henry Norris Russell and represents a major step towards an understanding of stellar evolution. (source) (video)

Solar flares produce gamma rays by several p…

Solar flares produce gamma rays by several processes, one of which is
illustrated here. The energy released in a solar flare rapidly
accelerates charged particles. When a high-energy proton strikes matter
in the sun’s atmosphere and visible surface, the result may be a
short-lived particle – a pion – that emits gamma rays when it decays.

Credit: NASA’s Goddard Space Flight Center

Quark star

Quark star

A quark star is a hypothetical type of compact exotic star, where extremely high temperature and pressure has forced nuclear particles to form a continuous state of matter that consists primarily of free quarks.

It is well known that massive stars can collapse to form neutron stars, under extreme temperatures and pressures. In simple terms, neutrons usually have space separating them due to degeneracy pressure keeping them apart. Under extreme conditions such as a neutron star, the pressure separating nucleons is overwhelmed by gravity, and the separation between them breaks down, causing them to be packed extremely densely and form an immensely hot and dense state known as neutron matter, where they are only held apart by the strong interaction. Because these neutrons are made of quarks, it is hypothesized that under even more extreme conditions, the degeneracy pressure keeping the quarks apart within the neutrons might break down in much the same way, creating an ultra-dense phase of degenerate matter based on densely packed quarks. This is seen as plausible, but is very hard to prove, as scientists cannot easily create the conditions needed to investigate the properties of quark matter, so it is unknown whether this actually occurs.

If quark stars can form, then the most likely place to find quark star matter would be inside neutron stars that exceed the internal pressure needed for quark degeneracy – the point at which neutrons (which are formed from quarks bound together) break down into a form of dense quark matter. 

They could also form if a massive star collapses at the end of its life, provided that it is possible for a star to be large enough to collapse beyond a neutron star but not large enough to form a black hole. 

However, as scientists are unable so far to explore most properties of quark matter, the exact conditions and nature of quark stars, and their existence, remain hypothetical and unproven. The question whether such stars exist and their exact structure and behavior is actively studied within astrophysics and particle physics.

If they exist, quark stars would resemble and be easily mistaken for neutron stars: they would form in the death of a massive star in a Type II supernova, they would be extremely dense and small, and possess a very high gravitational field. They would also lack some features of neutron stars, unless they also contained a shell of neutron matter, because free quarks are not expected to have properties matching degenerate neutron matter. For example, they might be radio-silent, or not have typical size, electromagnetic, or temperature measurements, compared to other neutron stars. source | quarks | neutron star

AR9077: Solar Magnetic Arcade On July 14…

AR9077: Solar Magnetic Arcade

On July 14th, solar active region 9077 (AR9077) produced a massive flare. The event also blasted an enormous cloud of energetic charged particles toward planet Earth, triggering magnetic storms and dramatic auroral displays. This striking close-up of AR9077 was made by the orbiting TRACE satellite shortly after the flare erupted. It shows million degree hot solar plasma cooling down while suspended in an arcade of magnetic loops. 

Credit: TRACE, Stanford-Lockheed ISR, NASA

What is a protostar?The formation of stars beg…

What is a protostar?

The formation of stars begins with the collapse and fragmentation of molecular clouds into very dense clumps.  These clumps initially contain ~0.01 solar masses of material, but increase in mass as surrounding material is accumulated through accretion.  The temperature of the material also increases while the area
over which it is spread decreases as gravitational contraction
continues, forming a more stellar-like object in the process.  During
this time, and up until hydrogen burning begins and it joins the main sequence, the object is known as a protostar.

This stage of stellar evolution may last for between 100,000 and 10 million years depending on the size of the star being formed. If the final result is a protostar with more than 0.08 solar
masses, it will go on to begin hydrogen burning and will join the main
sequence as a normal star.  For protostars with masses less than this,
temperatures are not sufficient for hydrogen burning to begin and they
become brown dwarf stars.

Protostars are enshrouded in gas and dust and are not detectable at visible wavelengths.  To study this very early stage of stellar evolution, astronomers must use infrared or microwave wavelengths.

Protostars are also known as Young Stellar Objects (YSOs).

Solar Prominence A prominence is a large,…

Solar Prominence

A prominence is a large, bright, gaseous feature extending outward from the Sun’s surface, often in a loop shape. Prominences are anchored to the Sun’s surface in the photosphere, and extend outwards into the Sun’s corona. While the corona consists of extremely hot ionized gases, known as plasma, which do not emit much visible light, prominences contain much cooler plasma, similar in composition to that of the chromosphere. The prominence plasma is typically a hundred times more luminous and denser than the coronal plasma. (source

animation:

Chuck Manges

What are nebulas?. And why nebulas are big as …

What are nebulas?. And why nebulas are big as galaxies.

Basically, a nebula a huge cloud of gas and dust. Some nebulae are the rest of the death of a giant star, like a supernova. Other nebulae are where new stars are forming. (more)

The nebulae are divided into some types:

  • Emission Nebulae
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Emission nebulae are gas clouds with high temperature. The atoms in the cloud are energized by ultraviolet light from a nearby star and emit radiation when they decay to lower energy states. Emission nebulae are usually red, because of hydrogen, the most common gas in the Universe and commonly emitting red light.

  • Reflection nebulae
image

Reflection nebulae are dust clouds that simply reflect the light of a star or nearby stars. Reflection nebulae are usually blue because the blue light is spread more easily. Emission and reflection nebulae are usually seen together and are sometimes called diffuse nebulae.

  • Dark nebulae
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There are also dark nebulae, they are clouds of gas and dust that almost completely prevent the light from passing through them, are identified by the contrast with the sky around them, which is always more starry or bright. They may be associated with star formation regions.

  • Planetary nebulae
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Planetary nebulae were named after William Herschel because when they first appeared to the telescope, they resembled a planet, later it was discovered that they were caused by ejected material from a central star. This material is illuminated by the central star and shines, and an emission spectrum can be observed. The central star usually ends up as a white dwarf.

  • Remnant of supernova
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Remnant of supernova is a gas envelope, composed of the remains of a star that was destroyed by a violent explosion, supernova, marking the death of this.