The Young Astronomers
Currently viewing the tag: "WISE"
A new image from NASA’s WISE mission has been released showing the beauty of a region of the Orion Molecular Cloud Complex known as the Flame Nebula.
The Flame Nebula as seen by WISE Credit: NASA/JPL-Caltech
The nebula is glowing with infra-red light thanks in no small part to a star 20 times the mass of our own sun that is blanketed with a dense surround of dust and gas. The star churns out vast quantities of energy that warm the dust causing it in turn to give of the infra-red light that has been collected to form this image.
The surrounding dust is so dense it causes the star to appear an amazing 4 billion times fainter to the naked eye than if it was free in space. Without this obscuring dust that star would appear as bright as the stars of Orion’s belt itself.
The smaller bright region about half way down the image is the nebula NGC 2023 – A reflection nebula surrounding a bright B class star
NGC 2023 Credit: Adam Block/NOAO/AURA/NSF
Slightly below and to the right of NGC 2023, the tuft of protruding material is actually the famous Horsehead Nebula:
The Horsehead Nebula Credit: ESO
The final remarkable feature in this image is the bright red crescent in its lower right portion. This is the bowshock – a wave of material deflected out of the way of a moving star – of the star Sigma Orionis.
You can read more about this image here
The latest release from NASA’s WISE mission has shown that just over 200 previously unidentified high energy objects are likely to be blazars.
Artist's Impression of an active Blazar Credit:NASA/JPL-Caltech
A blazar is a form of active galactic nucleus (AGN) – a galaxy where the central black hole is ‘feeding’ on large amounts of material resulting in the release of huge amounts of radiation including two tight very bright jets.
The angle at which the AGN is situated relative to the Earth determines which form of AGN we observe even though all are tied to the same processes.
In the case of a blazar we are looking directly down the AGN’s jets you could even say right down the barrel of the gun!
AGN at various angles; Credit: Aurore Simonnet, SSU NASA E/PO.
As the AGN must be lined up almost exactly with Earth for a blazar to be observed they are understandably rare compared to the other forms of AGN which have a much larger range of possible viewing angles. That being said the WISE data has the potential to reveal several thousand more.
A team using the WISE data looked at 300 objects that had previously been detected as high energy gamma-ray sources by the Fermi Space Telescope, though up to now had remained unidentified.
Using WISE the team was able to observe these gamma ray hotspots in infra-red wavelengths and showed that just over half are most likely to be blazars. WISE had also observed 50 new blazars outside those Fermi oddities along with taking observations of more than 1000 previously identified blazar candidates.
One of the project leads, Francesco Massaro has explained that there may be several thousand more as of yet unknown blazars hidden within the WISE data that could be revealed using the techniques developed for this first sample.
An image of one of the new WISE identified blazars Credit:NASA/JPL-Caltech/Kavli
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NASA’s WISE mission has produced a stunning image of the area of space surrounding the star Pi Scorpii (or Π Scorpii if you prefer), specifically the reflection nebula DC 129.
DG 129 and Pi Scorpii Credit: NASA/JPL-Caltech/WISE Team
The nebula sits in the middle of the constellation Scorpios’ ‘claw’ (the linking of stars into constellations with apparently ‘recognisable’ shapes is something that I fail to grasp).
It is located approximately 500 light years from the Earth and is classed as a reflection nebula as it is reflecting the light of nearby stars rather than producing its own light.
As I’m particularly interested in stellar astrophysics (the study of stars) I find Π Scorpii to be particularly interesting. In this image, Π Scorpii is the star on the right partially obscured by a greenish ‘fog’, but we see as one star is actually three – a ternary system.
The nebula DG 129 was first catalogued by the German astronomers, Johann Dorschner and Josef Gürtler, in 1963.
This image was obtained after spacecraft had depleted most of its coolant and had started to warm up rendering its longest wavelength detector (sensitive to 22 micron infra- red radiation) useless. Due to this failure, this image is composed of data from three filters rather than four. They are 3.4 microns (blue in the image), 4.6 microns (green in the image), and finally 12-micron (shown in red).
You can find more about this image here.
As I am sure, many of you know high mass stars end their lives in powerful explosions – supernovae. These explosions are among the most powerful single events in the universe and can be detected across vast distances; one has been detected in a galaxy 3 billion light years away from Earth, but this particular supernova is a little bit out of the ordinary.
The Smothered Supernova - Artist's impression - Credit: - NASA/JPL-Caltech/R. Hurt.
The explosion was detected by astronomers using NASA’s Spitzer Space Telescope whilst they were surveying the distance universe forAGN (Active galactic nuclei). The survey used Spitzer to detect the large amounts of infrared radiation (IR or heat) emitted by the AGN. As they searched through the data, they discovered a very hot area, which was emitting huge amounts of IR radiation from its centre. The astronomers found that the cloud did not fit the standard model of an AGN and data from the galaxies visible light spectrum lacked any sign of an AGN (this was confirmed using data from the ground based Keck Telescope in Hawaii).
It was concluded that the heat source was a very powerful supernova or hypernova. Whilst this is not the first hypernova to be detected, it is unusual in that the vast majority of the energy released in the six-month flare up during the event was in the IR radiation band. More normal supernovae release the majority of their energy in the visible range (along with UV, X and gamma rays).
The astronomers concluded that the explosion must have been muffled somehow, with most of its higher energy light photos being absorbed and converted into IR before being re-radiated. The solution comes from the activity of the star itself. As it is projected to have been around 50 times the mass of the sun, it would have been very unstable as it neared the end of its life. In a final effort to keep itself from blowing apart, it would have shed chunks of its atmosphere into space forming expanding dust shells around itself.
Studies of the area of the galaxy the supernova was detected in show evidence of at least two such shells, an outer one emitted around 300 years before the supernova with the second lying much closer to the star as it was released much closer to the time of the supernova (around 4 years prior to the main event). When the star finally exploded the majority of the energy released as high energy light (visible, UV, X and gamma rays) was absorbed by the dust shells, warmed them up to a temperature of around 1000 kelvin (just above the surface temperature of Venus) and then was re-emitted to the universe as IR radiation.
The star may brighten again in around a decade as the shockwave produced by the supernova smashes the two dust clouds together. Many more such supernovae may be detected in the data provided byNASA’s WISE spacecraft. We may not even have to wait that long for such a supernova to occur considerably closer to home – one of the brightest stars in the Milky Way – Eta Carinae is expected to go supernova in a similar way within the next few millennia.
You can read more here.
This superb image shows the runaway star Zeta Ophiuchi
Zeta Ophiuchi Credit: NASA/JPL-Caltech/WISE Team
The star is located about 460 light years from Earth and is a relative newcomer on the galactic seen at around four million years old.
Despite looking rather serene in this stunning infra-red image obtained by the WISE spacecraft, the star is 20 times the mass of our sun and is 65,000 times as luminous. To make matters even more interesting it is travelling through space at a phenomenal 24 km a second!
The extreme speed is causing the distortions and compressions in the interstellar dust ahead of the star heating it up, and causing it to appear red in this image.
The various colours in the image come from data from WISE’s four infra-red filters.
Despite being only 4 million years old, Zeta Ophiuchi is already middle aged and is expected to explode as a supernova within around 4 million years.
That would mean that Zeta Ophiuchi would follow in the footsteps of is projected partner – an even more massive star that has already gone supernova. It is this explosion that is thought to have given the star enough energy to plough through space so rapidly.
You can read more here
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