The Enigmatic Eagle

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.

The Eagle Nebula seen by Hershel and XXM-Newton Credits: far-infrared: ESA/Herschel/PACS/SPIRE/Hill, Motte, HOBYS Key Programme Consortium; X-ray: ESA/XMM-Newton/EPIC/XMM-Newton-SOC/Boulanger

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.

XXM data of the Eagle Nebula Credits: ESA/XMM-Newton/EPIC/XMM-Newton-SOC/Boulanger

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:

Hershel's view of the Eagle Nebula Credits: ESA/Herschel/PACS/SPIRE/Hill, Motte, HOBYS Key Programme Consortium

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 Pillars of Creation as seen by Hubble Credits: NASA/ESA/STScI, Hester & Scowen (Arizona State University)

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.

The Pillars of Creation as seen by ANTU Credits: VLT/ISAAC/McCaughrean & Andersen/AIP/ESO

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.

Composite image of the Eagle Nebula Credits: far-infrared: ESA/Herschel/PACS/SPIRE/Hill, Motte, HOBYS Key Programme Consortium; ESA/XMM-Newton/EPIC/XMM-Newton-SOC/Boulanger; optical: MPG/ESO; near-infrared: VLT/ISAAC/McCaughrean & Andersen/AIP/ESO

You can read more about this fantastic collection of images here.

A Heavenly Veil – Updated

This truly stunning image of the Eastern Veil SNR was released at the very end of 2010 by the Issac Newton Group of Telescopes.

NGC 6992 Credit: A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro

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.

The Western Veil Nebula Credit: Nick Howes

You can read more here.

The Life of Discovery – Recovered

This post has been produced by VanessaG for the Young Astronomers

Discovery, with her maiden flight on 30 August 1984, with STS-41D. On the ascent she carried more than 41,000 lbs of cargo which was a record at the time. This cargo was mainly science experiments to study the effects of microgravity. Discovery was also the first shuttle to retrieve a satellite and bring it back to Earth. In 1985 Discovery was the first shuttle to fly four missions in one year.

Discovery as seen from the ISS during STS-128 Credit: NASA

On STS-51D the first sitting member of the US congress blasted off into orbit, Jake Garn, the republican senator of Utah. During the landing she suffered a blown front tire and subsequent brake damage. This then meant that all further flights for five years were directed to land at Edwards Air Force Base, California until nose wheel steering was introduced and brakes improved.

After the Challenger and Columbia disasters it was Discovery who was called upon to return the US to space again and regain their independence. The return after Columbia, STS-114 under the leadership of Eileen Collins; who earlier on STS-63 was the first female pilot. This mission was also the first to do a back flip on approach to the ISS so that the station crew could photograph the underside of the shuttle which then could be studied to check for damage. This was also the first time a repair had been made to a spacecraft while in orbit, the EVA crew removing two protruding spacers in the thermal shielding.

In April 1990, on STS-31, Discovery released the Hubble Space Telescope. This was also the highest ever flown by a shuttle at 380miles. And the ‘scope is still in use twenty years later and continues to provide valuable insights into the beginnings of the universe.

STS-60, February 1994, was the first co operative mission between the then enemies of Russia and the US. This laid the foundations for international cooperation which is one of the fundamental aspects of the International Space Station. With a Russian cosmonaut flying about the American shuttle Discovery. Discovery’s next flight, STS-63 was the first mission to be piloted by a woman, Eileen Collins, who laid further foundations into international cooperation as she piloted Discovery to within 40ft of MIR. Correcting the final approach for the first shuttle docking with the Russian space station.

Discovery has seen many other significant events in international development, the first spacewalk by an African-American, the last shuttle to visit MIR. The oldest astronaut, John Glen on board STS-95 who at the time of the flight was seventy seven, and still is the oldest person to ever fly in space.  Discovery also celebrated the 100^th shuttle fight on board mission STS-92. And on STS-120 lead by commander Pamela Melroy met Peggy Whitson, commander of Expedition 16 on board the ISS in 2007. This not only was not only the first time the ISS has been commanded by a woman but the first time two female commanders met in space.

In her 26 year lifetime Discovery has achieved many great things in the world. Not only advancing science but also cooperation and technology that you will use everyday. In total 180 people have travelled on board Discovery and a total of 150 million miles have been travelled in orbit.

Discovery Launches to Begin STS-128 Credit: NASA/Jerry Cannon, George Roberts

Opportunity from Orbit – Recovered

NASA’s Mars Reconnaissance Orbiter (MRO), has used its High Resolution Imaging Science Experiment (or HiRISE – and yes I know what you are thinking, and yes they did do that deliberately), to capture this amazing image of the Santa Maria Crater, including the rover Opportunity sitting on the crater’s edge.

The Santa Maria Crater as Seen by the MRO's HiRISE Camera Credit: NASA/JPL/University of Arizona

The astounding detail of the image also shows the tracks of the rover on the left hand side of the image.

The small blob indicated by the arrow is the rover itself.

The image was captured on the first of March 2011 which corresponds to Opportunity’s 2,524th Martian day of operation on the Red planet.

You can read more here and here.

Japanese Solar Sail Craft with LCDs! – Recovered

This post has been produced by DeepikaG for the Young Astronomers

This is innovation at its best. Scientists at JAXA (the Japan Aerospace Exploration Agency) not only created a satellite with solar sails (something poor guys at the planetary society will probably be fuming at) but created an innovative method to control its attitude, not by using rocket motors but a simple liquid crystal display. Yes this is the same stuff used to make the displays in your calculators and watches!

The liquid crystal device on the craft is a thin-film instrument that changes the surface reflection characteristics of sunlight by turning on and off the power of the device.

Location of the LCDs on the IKAROS craft, Image Courtesy: JAXA

For the uninitiated, a solar sail works just like an ordinary wind-sail. The major difference being that instead of wind, it uses pressure generated by incident light radiation from the sun. When electromagnetic radiation is incident on a solid, it exerts a small force on the target, that may cause it to move. Solar sails ave potential application in deep space missions, as the maximum theoretical speed gained from a solar sail is the speed of light!

The difference in solar pressure is used to generate torque and re-orient the spacecraft.

The IKAROS was launched from the Tanegahima Space Center on May 21, 2010.

Related Links:

How Solar Sails work 
Planetary Society Solar Sail Initiative

Astrophotographer of the Year 2012

The Royal Greenwhich Observatory launched its annual Astrophotographer of the Year competition yesterday. All you budding astrophotographers should really take the chance to enter your shots so you can be in with a chance of wining some fantastic prizes.

If you want to find out more or how to enter, keep reading!

Here is the information provided to us by the competition organisers themselves: -

The Royal Observatory Greenwich, in association with Sky at Night Magazine, launched its 2012 Astronomy Photographer of the Year competition yesterday– kicking off its annual global search for the most beautiful and spectacular visions of the cosmos, whether they are striking pictures of vast galaxies millions of light years away, or dramatic images of the night sky taken much closer to home.

Entries to the competition must be submitted by midday on 29 June 2012 and the winning images will be showcased in the annual free exhibition at the Royal Observatory Greenwich from 21 September 2012 to February 2013. Last year the competition, which was first launched in 2009, attracted a record number of entries with over 700 spectacular images submitted from around the world.  The competition also saw its first UK overall winner, as amateur astronomer Damian Peach scooped the top prize for his incredibly detailed shot of Jupiter along with two of its 64 known moons, Io and Ganymede, showing the surface of the gas giant streaked with colourful bands and dotted with huge oval storms.  Sir Patrick Moore, who is one of the competition judges, was impressed by the quality of entries, describing Damian’s shot as a “very worthy winner against extremely strong competition”.

Other winning photos from 2011 included: the rich star fields of the Milky Way stretching across a tropical skyline of palm trees by Tunç Tezel (Turkey); the spectacular aftermath of a supernova explosion showing the bright red and blue wispy remnants of the dead star by Marco Lorenzi (Italy); and American newcomer Harley Grady’s image of Zodiacal Light reaching into the sky above a barn in Texas.  The Young Astronomy Photographer of the Year accolade was won by 15 year old Jathin Premjith from India who impressed the judges with his skillfully executed image of the coppery-red Moon taken during a lunar eclipse.

Dr Marek Kukula, Public Astronomer at the Royal Observatory Greenwich and judge in the competition said:  “Astronomy is becoming increasingly popular with the public which is reflected in the big rise in entries we saw in 2011.  Every year the competition has brought new surprises, I love the fact that we receive entries from people all around the world and from complete beginners as well as seasoned experts.  All the judges are excited about what we’re going to see this time around.”

The competition is powered by the photo-sharing website Flickr.  Photographers can enter online by visiting www.rmg.co.uk/astrophoto and each entrant may submit up to five images to the competition.

Competition judge and Sky at Night Magazine Editor, Chris Bramley, said “The standard of astro images in 2011 was breathtaking. With once-in-a-lifetime events like the last transit of Venus for 105 years occurring this year, I’m eagerly anticipating the judging of 2012’s entries.”

Astronomy Photographer of the Year 2012 has four main categories:

• Earth and Space – Photographs that include landscape, people and other earth-related things alongside an astronomical subject ranging from the stars, the Moon or near-Earth phenomena such as the aurora.
•  Our Solar System – Imagery which captures the Sun and its family of planets, moons, asteroids and comets.
•  Deep Space – Pictures that capture anything beyond the Solar System, including stars, nebulae and galaxies.
•  Young Astronomy Photographer of the Year – Pictures taken by budding astronomers under the age of 16 years old.

The winners will be announced at a ceremony on the 20th of September at the Royal Observatory itself. The exhibition of the winning photographs will open on the 21st September in the Observatory’s Astronomy Centre and entry is free.

Prizes

• Overall Winner – £1500
• Category Winners – £500
• Runners Up – £250
• Highly Commended - £125

There are also three special prizes: People and Space recognises the best photo featuring people in the shot; Best Newcomer is awarded to the best photo by an amateur astrophotographer who has taken up the hobby in the last year and who has not entered an image into the competition before; and Robotic Scope, which was a  new prize introduced in 2011, is awarded for the best photo taken using one of the increasing number of computer-controlled telescopes at prime observing sites around the world which can be accessed over the internet by members of the public.

The winners of the special prizes will recieve £325 and the runner up for the People and Space special prize will receive £125

Get entering folks!

Image of the Week – A New Look at the Helix – 19/01/2012

I’m sure all of are aware of NGC 7293\Caldwell 63. No? Perhaps if we use its more common name – The Helix Nebula – we can jog your memory a little.

The ESO has used the VISTA telescope shows the nebula in a way that has never been seen before.

VISTA's view of the Helix Nebula Credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit

This image shows the nebula in infra-red radiation which reveals the details of the cool gas and dust structures within the nebula which ironically aren’t visible in images taken in the visible range of the spectrum. The image reveals the exquisite sub structure of the inner rings as well as the faint trails on the outskirts of the nebula.

The Helix is a planetary nebula produced by a dying star flinging off its outer layers into space. The central star is visible as the tiny blue dot in the centre of the structure, within a few short million years the star will have fully transitioned to a white dwarf and the nebula will dissipate into the interstellar medium leaving nothing but the faint, cooling remnant.

It is loacted in the direction of the contellation Aquarius at 695 (+98/-52) light years from Earth and spans a region of approximately 2.5 light years at its widest point.

A comparison between the Infra-red image and a visible image of the Helix Nebula Credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit

You can read more here

A Solar Storm is on the Way!

Solar activity has been ramping up for some time now and the latest blast is heading our way.

Sunspot 1401 emitted an M3 class solar flare this afternoon that it is on its way towards Earth and is projected to arrive at about half ten on the 21st of January.

The current SDO image of the Sun Credit: SDOHMI

We can expect to hear more about 1401 as it moves across the disk of the sun. It is currently producing one M class flare per day and has yet to come into direct alignment with Earth, so stay tuned for more developments!

Planck Completes its Primary Mission

The ESA’s Planck Space Telescope completed its mission on Saturday.

The mission was designed to peer into the detail of the cosmic microwave background radiation (CMB) – the residual energy left after the Big Bang.

An artist's impression of the Planck spacecraft with a microwave background Credit: ESA

Planck also used its microwave detectors to gaze at the cold dust within our galaxy and beyond, detecting many new galaxy clusters in the distant universe. Some of these even appear to be interacting and merging to form even larger superclusters.

The first data from Planck was released last year and included the improved catalogue of galaxy clusters, though the first data set on its study of the CMB is yet to be released, though this will be made available to scientists outside the project in the early stages of 2013.

The mission was originally planned to make two surveys of the entirety of the sky over the space of 15 months. Planck performed better than expected and completed five surveys over 30 months, double the original mission expectancy.

The data released so far also reveals that stars in the universe were being formed at one thousand times the current rate, a fairly phenomenal statistic!

The telescope is equipped with two instruments:

• The High Frequency Instrument or HFI
• ow Frequency Instrument or LFI

These two instruments work in tandem to build up a highly accurate map of the CMB. Unfortunately the HFI is now offline as the spacecraft depleted the last of its coolant supply and has now warmed above the critical temperature required for the useful opperation of the detector. The LFI however is still in working order and will continue to provide additional data over the rest of the year.

No doubt the data from Planck will reveal many new interesting features of the universe over the next few years, I for one am very excited!

You can read more here.

Stellar Spectral Classes – Explained – Updated

As I explained in a previous post about star types there are many varieties of stars; they range from red dwarfs to blue supergiants. As I’m sure you can see these are broad groups with, in some cases, very different types of stars being lumped together under the same banner. Thankfully astrophysicists have another stellar classification system that is considerably more definitive, this is the spectral class system.
The system first splits all the stars visible in the universe into broad categories based on their colour: -

• O – Blue
• B – Blue-white stars
• A – White
• F – Yellowish white (cream)
• G – Yellow
• K – Orange
• M- Red

If you have difficulty in remembering these classes why not use the mnemonic

Oh Be A Fine Girl\Guy Kiss Me

An image showing Spectral classes of main sequence stars Credit: Kieff

With the discovery of brown dwarfs, three new groups have been added to this system:

• L – Very dim red dwarfs & hot brown dwarfs
• T – Cool brown dwarfs
• Y – As of yet hypothetical cold brown dwarfs, with surface temperatures close to room temperature

These groups are also quite broad but are subdivided by adding a number after the general class. This number ranges from 0-9 and indicates roughly where a particular class lies within its broader spectral class with the system being accurate to 1/10 of a class.  For example a F4 star is a Yellow white star 4 tenths between an F0 and A0 star.

Even with this subdivision there is a problem: – A main sequence red dwarf could have the same spectral class as a red supergiant. This is avoided using the final section of the classification system, a roman numeral from zero (technically the Romans didn’t use a zero but anyway  ) to seven is used to denote the general type of the star. There are also various subclasses which are not covered here.

• Type O are the largest ‘hypergiant’ stars.
• Type I are the supergiants.
• Type II are the bright giants – stars smaller than supergiants but having a higher luminosity than most ‘normal’ giant stars
• Type III are the normal giants
• Type IV are the subgiants – stars larger than the main sequence but not large enough to be classed as a true giant.
• Type V are the main sequence stars or dwarfs (not white dwarfs however).
• Type VI are the sub-dwarfs – small stars that sit below the main belt of main sequence stars
• Type VII are the white dwarfs

These when plotted produce the following diagram: -

Diagram showing the main elements of the Yerkes spectral classification. Note spectral class is along the base and absolute magnitude increases when moving up the diagram. Modifications: Peter Clark

So using the full classification system our sun or Sol is a class G2V star.

As well as helping to separate stars into classes the colour of a star also hints at its temperature.  However this may appear counter intuitive: – Humans have become accustomed to blue meaning cold and red meaning hot however with stars the opposite is true – the bluest of stars are the hottest and the red varieties are much cooler. The other colours fall within these extremes  (the first image above shows the main temperatures of stars ranging from cool red main sequence stars on the to the much hotter blue main sequence stars on the right).

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This seemingly strange colour pattern can be explained using the principles of electromagnetic emission:  - The hotter the star the more high energy, high frequency, electromagnetic (EM) radiation it emits. A hot star will emit most of its energy in the form of X and gamma rays, what visible light it releases will be in the high energy blue region of the spectra giving its blue colour. A moderately hot star will emit visible light at a larger range of frequencies and so takes on a white appearance (white is a mixture of all the visible colours of light). An average temperature star like our sun releases more of its energy towards the lower energy end of the spectrum and so appears yellow. A ‘cool’ star emits much of its energy in the low energy end of the spectrum emitting little X or gamma rays. This means that more of the stars energy is released in the lower frequency, lower energy part of the E-M spectrum (such as radio and microwaves), this in turn means that the majority of the visible light they emit is in the red end of the visible spectrum and as such these stars appear red.

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The next paragraph relates directly to main sequence stars – those stars that are fusing hydrogen in to helium in their cores.

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The temperature of a star is not the only difference between the spectral classes. As can be seen in the above diagram an O class main-sequence star is many times the size of an M class main-sequence star. This is in part due to the mass difference between the two classes an M class main sequence star can be as low as 0.1 solar masses (10% the mass of our sun) whilst the mass of an O class star can be as much as 60 solar masses. Due to the higher mass the star needs more room to store the mass and so has a larger radius.

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There is a close relationship between the temperature of a star and its luminosity - brightness. A cool M class star emits very little energy per second and so has a low luminosity value – it is dim.  A hot O class star releases a great deal of energy per second and so is bright – it has a high luminosity. However this is not the full story, an M class supergiant will be more luminous that a G class main sequence star as can be seen below. This is because despite a red star releasing less energy per square area than a yellow star, a supergiant has much more area to emit radiation over than a yellow main sequence star and thus is inherently brighter.

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All this information can be used to plot a star on the Herztsprung-Russell diagram (See below).

The H-R Diagram (Original Image Designer Unknown)

The diagram plots the spectral class (and thus the temperature), the luminosity, mass and the lifetime (for main sequence dwarfs) of stars.
To help visualise this information I have added some labels to the standard diagram (which are colour coded to their appropriate arrows).

Altered H-R Diagram Modifications: Peter Clark

All stars start their lives on the main sequence and it is here where they remain for most of their lives. After they deplete their reserves of hydrogen and swell into red giants they move of the main sequence towards the top right hand corner of the diagram. The most massive of which ascend the diagram even further and enter the horizontal branch of the supergiants. Once (or if) a star becomes a white dwarf it drops to the bottom left of the diagram where it slowly lowers further to become a dead black dwarf.
I hope this post has shed some light (pun intended  ) on the classification of stars.

You can read more generally about spectra here