Nowadays, scientists have the ability to observe the universe across many wavelengths, including those that cannot be seen by unaided human eyes – such as infrared and gamma rays. However, there is still some “blind spots” for the astronomers in the electromagnetic spectrum, such as the high energy X-rays region.
In order to clarify our view of these cosmic X-rays, NASA has just launched the Nuclear Spectroscopic Telescope Array (NuSTAR), a sci-fi looking space observatory that will allow us to better understand the physics and chemistry behind the most extreme objects in the universe.
NuSTAR is going to observe the same kind of X-rays used in medicine – when the doctors need to take a look at our bones – and in airports – to see what’s inside our luggage. Although we have spacecraft able to take X-ray images, like NASA’s Chandra and ESA’s XMM-Newton, these facilities aren’t able to get sharp images of this energetic form of light.
Surveying the Extreme Universe
The NuSTAR’s primary mission – projected to last for at least two years – is intended to provide a detailed survey of both stellar and supermassive black holes. Although being known as objects capable of swallowing pretty much everything nearby – even light – the region around the black holes – called the accretion disk - emits vast amounts of X-ray radiation, produced by the friction between the pieces of debris orbiting the black hole. NuSTAR is equipped to detect these radiation bursts and locate black holes that would be otherwise invisible.
It’s also going to analyse the young-supernovae remnants, more specifically, the radioactive nuclei produced by the exploding stars. These nuclei are the key to understanding the conditions in which each explosions occurred, the nuclear ignition, structure and dynamics of the explosion, giving us clues as to how exactly the elements are formed in the hidden core of a star.
The brightest objects visible to NuSTAR are the jets emitted by supermassive black holes – that can be found in the core of most galaxies – in a specific kind of galaxy known as a blazar. These are a form of active galaxy that produce jets composed of particles travelling in very high speeds that happen to be pointing towards the Earth – therefore we see them much brighter than we would otherwise. By observing the variation of the light intensity of these beams, we’ll be able to figure out how the black hole’s accretion disk looks like, as well as the physical structure and composition of the jets.
And that’s not all: the probe will also peer at the Solar corona, the outer atmosphere of the Sun. This region is known for its extreme temperatures – as a matter of fact, even hotter than the Sun’s surface. By studying the corona, we can get a close-up look at the particle acceleration processes similar to those that take place in objects like supernova remnants and black hole jets.
Looking Further than Ever
What makes NuSTAR able to archive all these goals is its ingenious focusing mechanism: a pair of Wolter-I mirrors pointing at the same patch of sky. Moreover, in order to improve its reflection capacity, these mirrors are coated with structures known as “depth-graded layers”, made of a mix of low and high density materials.
The unprecedented sensibility of NuSTAR – along with the data from the other observatories – will allow us to study the universe as never before, from the surface of the Sun to the galaxies at the other edge of the universe, going through the most extreme objects known by humankind.
NuSTAR has successfully reached orbit and is preparing for the commencement of its observations.
The Eagle Nebula is one of the most well known regions in the universe having been snapped many times over the years by several telescopes including Hubble.
The latest images of the region come from the ESA’s Hershel Infrared Space Observatory and the XXM-Newton X-ray Observatory.
This image spans approximately 75 light years across the entirety of the nebula.
This image is a combination of data from both telescopes of the dense central region of the nebula. We can learn more about the information the image displays if we separate the data from each observatory, first lets have a look at the XXM-Newton X-ray data.
Each individual dot on the image is an X-ray source with the various colours indicating the energy of the X-rays being emitted by the source, red being the lowest energy (0.3-1keV) working up through medium energy sources shown in green (1-2keV) to the highest energy sources displayed in blue (2-8keV).
The XXM was observing the area to help determine the source of the Eagle Nebula’s strong emission. One theory suggests that a hidden supernova remnant could be supplying the nebula with large quantities of energy whilst remaining obscured by the nebula’s dense cloud. To help determine if this theory is valid the XXM is scouring the area in an attempt to detect any sign of a faint X-ray emission extending from the central region. The scientists believe that if the XXM doesn’t detect any more emitting material than has already been identified by previous searches using Sptizer and Chandra this will be strong support of the hidden SNR explanation.
Now lets examine the Hershel data:
This displays the nebula in infra red wavelengths with 70 microns displayed in blue, 160 microns in green (both of these wavelengths were captured using filters in the PACS – Photodetector Array Camera - instrument) and finally 250 microns in red(images by SPIRE - Spectral and Photometric Imaging Receiver).
All these wavelengths are associated with very cold gas, indeed any gas displayed in blue here is just 40K above absolute zero down to that displayed in red which is a chilly 10K.
The twisted gas tendrils are still collapsing and will continue to form the next generation of stars for quite some time yet before the nebula finally disperses. Perhaps the most famous region within the nebula are the ‘Pillars of Creation’ which are in the above images which can be viewed just below the central point in the image (the eagle for which the nebula is named is located half way up the image on the left hand side, with its head pointing inwards). Indeed the Pillars are the central feature in one of the most recognisable image in all of astronomy:
The image was taken by Hubble in visible light using filters that isolate emission from excited hydrogen (Hα), singly ionised sulphur (SII) and doubly ionised oxygen (OIII). For scale, the tallest pillar is approximately four light years in height.
Now if we look at the same region in the infra red part of the spectrum (this time the data is provided by the ESO‘s, VLT’s ANTU telescope using the ISAAC instrument – yes that is quite a lot of acronyms), it looks completely different.
At these wavelengths all but the densest regions of the Pillars are virtually transparent allowing us to gaze in wonder at the clumps of stars forming at the tips.
I leave you with this composite image, containing X-ray, visible and infra red data, enjoy.
You can read more about this fantastic collection of images here.
This truly stunning image of the Eastern Veil SNR was released at the very end of 2010 by the Issac Newton Group of Telescopes.
The nebula is located approximately 1470 light years from Earth and was produced by a detonating star that died between 5000 and 8000 years ago.
The nebula is the visible portion of the much larger Cygnus Loop and is divided into several arcs, with the image above showing part of the eastern section. Since it’s formation the remnant has expanded to a size that makes it appear to have a diameter around 6 times that of the full moon, or 36 times it’s area when viewed in the night sky. This translates to roughly 50 light years in physical diameter.
The loop is one of the brightest features in the X-ray skyscape as viewed from Earth. The nebula contains large quantities of hydrogen, sulphur and doubly ionised oxygen (OIII) each of which have been picked up in the filters used by the Newton Telescopes. They are displayed in the image as red, blue and green respectively.
The classification name given to this section is NGC 6992 of the nebula, and the Eastern section is also happens the brightest region of the loop.
The nebula was first observed by William Hershel in September 1784.
As the nebula is part of the Cygnus loop it can be viewed in the constellation Cygnus and is most spectacular when viewed through an OIII filter.
You can read more here.
The galaxy cluster Abell 2052 is in a bit of a swirl.
The cluster is located at 489 million light years from Earth (z=0.03549) in the direction of the constellation Serpens – The Serpent. Abell 2052 contains many galaxies with the brightest being UGC 9799, that also has a Seyfert 2 class AGN.
The main image is a combination of X-ray data obtained by NASA’s Chandra Space Observatory and optical data from the ESO’s VLT.
X-ray data is displayed in blue, and shows hot gas at temperatures of around 30 million Kelvin, optical information is displayed in gold.
The large spiral of this superheated material in the centre of the image, which spans over one million light years in reality, was produced when a smaller galaxy cluster collided with the larger main cluster, throwing gas and dust outwards whilst heating it.
The smaller cluster passed through the main cluster several times under the action of gravity, with a spiral pattern being formed as the collisions were off centre – a perfectly lined up series of collisions would have produced a collisional ring.
The disturbance of the material has several effects on the galaxies:
- Cooler, denser gas is thrown outwards – this limits the ability of the material left in the core to cool and contract, thus limiting star formation
- Heavier elements such as Iron, Nitrogen and Oxygen are distributed throughout the region perhaps helping to stimulate the production of planets, and further down the line, life
You can read more here
 A description of how to interpret the z variable is pending. The distance estimate used in the post was calculated using WolframAlpha
 A detailed explanation on the various types of AGN is pending. Data for UGC 9799 was obtained using SIMBAD
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