I'm Still Here - But Only Just

I lost my dear mother 6 Nov 2008. She went home to be with the Saviour after a long illness. I miss her terribly and I weep for her almost every day. She stayed with me during her illness and I took care of all her needs with the help of her GP and Macmillian Cancer support.

I will be back to the astronomy blogging world, but not just yet.

Hope you are all well and happy.

~Z~

Clear Skies

Finally, the other night I was able to get the telescope out in the back garden and give it a try. The moon had already gone behind some trees by the time I got outside so I missed that. But! I pointed it toward the Pleiades and oh what a sight! Clear, crisp points of light with no refraction and no jiggling about. Seeing conditions were exceptional, however. I can't wait to try for the moon. Maybe I'll get lucky tonight.

I have no experience with telescope optics but this little scope of mine seems to be perfect for a beginner like myself.

Went outside last night to take a look around and thought about hauling the scope out to take a look at Mars, but since the planet was almost overhead, I changed my mind.

Not Meant to Be

It has been crystal clear all day - not a cloud in the sky and the sun so bright I've had to sit here with the drapes slightly closed because my poor eyes can't take the brightness. So, I thought I'd get the telescope out in the back garden to cool down and do a bit of observing but guess what? Yeah, big, dark, black clouds are blowing in from the west.

Oh well, perhaps I'll get to use it sometime soon. Seems like when the weather co-operates my health does not. Hopefully everyone else is having better luck.

New 'Scope

Got my telescope set up today. Hurrah! It was easy to put together and seems to be a great beginner telescope. I can't wait to try it out.

As I write this, seeing conditions are not good. Cloudy with a 30% chance of precipitation so no testing the telescope tonight.

It's good to be back and I promise to update more often.

Toodles!

I'm Back!

Been MIA for the past few months but I've not abandoned my blog. Been working through some health issues these past months most recent being a bad back. Anyway......

Santa is bringing me a telescope. Nothing spectacular just one of those Bresser Skylux refractors that Lidl sells most every year at this time. Santa wanted to get me a much more better telescope but I told him I needed something I could handle (bad back, you know) and not too complicated - although that German equatorial mount may give me probs until I get the hang of it. Plus, with the crummy weather we have here I cannot for the life of me justify more £'s for an instrument I'll not be able to use more than a few times per year. I'm really looking forward to doing some active observing.

Happy Holidays!

~Z~

Leo

The brightest star of this constellation, alpha Leo, called Regulus (meaning: the little king), is a blue-white star (spectral type B7 V) of 1.35 mag. When viewed with binoculars or small telescopes a wide companion of 8th mag is revealed.
At the tip of the lion's tail the beautiful blue-white main sequence star beta Leo, Denebola is located. Viewed through a telescope beta Leo seems to have an orange companion. But actually the two stars are far away from each other.
Another optical double is tau Leo; the 7th mag companion of this orange 5th mag star can be seen in binoculars.
The binary gamma Leo, called Algieba (the lion's mane), is a magnificent pair, which components consists of a orange-red giant of 2.6 mag brightness and a yellow giant with 3.8 mag. A small telescope is sufficient to split gamma Leo into the single stars. Using binoculars a unrelated 5th mag star, 40 Leo, can be seen next to them.
The binary omega Leo (a 7390) is a very difficult object to resolve. You will at least need a scope with 250mm aperture. The two stars revolve each other with a period of 117 years.
With very low power 54 Leo can easily be resolved into a pair of 4.5 mag and 6.3 mag.
Between eta Leo and gamma Leo the double a 7704 can be found; but to resolve its components into single stars (both are about 7.5 mag) telescopes of at least 100mm aperture are required.
Zeta Leo is an optical triple star of 3.44 mag. Using binoculars this stars seems to have two companions of 6th mag, but they are not physically related together.
The red giant R Leo is a long period variable star. Its brightness varies from mag 4.4 to mag 11.6 (the Bright Stars Catalog gives an average of 6th mag) with a period of about 313 days. It is located in the Lion's foreleg.
For Leo is located far away enough from the dust and the star clouds of the Milky Way the farther away galaxies became visible. There are some interesting galaxies in this region, but they are not easy objects for small telescopes. The three galaxies M65, M66 and NGC 3628 form a conspicuous triple.
The other two Messier objects, M95 and M96 are two fainter spiral galaxies. For more information and observing hints please follow the links to the Messier database.
There is a large number of meteor showers associated with this constellation. The most famous are the Leonids. This shower radiates from the region of gamma Leo and can be seen form November 14-20; the maximum can be observed on November 17th. Although the hourly rate from 10 to 15 meteor seems to be small there is a cycle of about 33 years with an enhanced activity. The next spectacular storm is predicted to take place in 1999.
The shower of the Alpha Leonids was first confirmed by Radio Meteor Project. The duration of this shower cover the period from January 13th to February 13th.
From February 14th to April 25th the Beta Leonids are active. The maximum takes place around March 20th.
Nearly at the same time - from February 2nd to March 19th - the Delta Leonids can be observed. The maximum of the activity peaks at February 22nd.
A rather weak shower are the Gamma Leonids, which are active from August 14th to September 12th with a maximum occuring on August 25th.
The meteor shower of the Rho Leonids seems to be non-existent; yet it has been discovered by radio studies in the 1960's. It seems to be "active" around March 14-15th.
The Sigma Leonids are another storm of doubt. Only one observation has been made.
Detailed information for all meteor showers can be found in Gary Kronk's database about meteor showers.

Source: Seds

Lunar Eclipse 2007

What a gorgeous sight! Went outside around 21:40 to set up my little telescope and already La Luna was changing colour. The sky was crystal clear with minimal turbulence. I kept the scope on the moon and when not looking at the eclipse I admired the Pleiades, Taurus and Orion. The view was good in my 10x50 bins as well.

I hope everyone else had as good a view and I can't wait to read about what other bloggers have to say about Lunar Eclipse 2007.

Aurigia!

The yellow giant alpha Aur, called Capella, is the 6th brightest star in the sky (0.08 mag). It is also a spectroscopic binary consisting of a G5III and a G0III. They revolve each other every 104 days.
Menkalinen, beta Aur, is also a spectroscopic binary. Within just four days the stars complete their revolution much faster than those of alpha Aur. Since they are eclipsing each other the brightness of beta Aur seems to vary.
The eclipsing binary epsilon Aur has an extraordinary long period; every 27.1 years the brightness varies from 3.0 mag down to 3.8 mag as the brighter component is then eclipsed by the darker companion. This eclipse lasts a full year (the last eclipse took place in 1983). Calulations show that the dark component of epsilon Aur has about 10 -12 solar masses. Because of its small size it is a good candidate for a black hole; unfortunately this conflicts with the observed lost of brightness during the eclipse. According to studies of Wilson and Cameron the solution is a ring of obscuring material which surrounds the black hole. (There is still doubt that the companion is a black hole; a star which a 10 times smaller brightness would fit the model, too.)
Another eclipsing binary is zeta Aur; a K4 bright giant and a B8 main sequence star revolve each other every 2 2/3 years.
The double omega Aur can be viewed with small telescopes; it consists of a 5th mag and a 8th mag companion.
Telescopes with an aperture of at least 100mm and a high magnification are required to split the tight double theta Aur. An A0psi star of 2.62 mag is accompanied by a star of 7th mag.
The planetary nebula NGC(*) 2149 (the asterisk indicates that this object can be found in the NGC supplementary catalogs of J.L.E. Dreyer) appears as a small oval ring of 10th mag.
The diffuse nebula I 405 is also called Flaming Star.
I 410 consists of a cluster with an nebulosity attached.
There a several open clusters in this constellations.
About 60 members belong to M36. Its a good object for the use of binoculars. A beautiful group of stars is M38 showing an oval shape. The richest of these three Messier objects is M37. It contains about 150 stars with magnitudes of 12.5 and brighter and about 500 in total. Detailed information about all three Messier objects can be found in the Messier database.
The meteor shower of the Aurigids is generally observable between January, 31st, and February, 23rd. This shower is known for its bright fireballs.
From August, 25th, till September 6th, the shower of the Alpha Aurigids is active. Although the annual maximum is about 9 meteors, outbursts of up to 30 were observed in 1935 and 1986.

Source: Seds

Snow!

My little Yorkie loves it. We got at least three inches and she looked like a little pink snow-plow.

**Sigh** So much happiness and love in such a little package.

Orion: Part Two

A constellation, which is the head of a constellation family, located in the equatorial region of the sky and belongs certainly to the most famous constellations. It extends from RA=4h 40m to RA=6h 20m and DECL=+23 degrees to DECL=+8 degrees.

In some ways the central part of this constellation reminds on a oblique sand-glass. In wintertime Orion is a magnificent constellation which can easily be found by the the three stars forming a line building the belt of the Hunter. The belt stars point towards Sirius, the brightest star in the constellation of the Larger Dog, Canis Major, situated SE of Orion.
From his belt there hangs a well defined deggar, which is known for one of the most famous nebulas in the sky: The Large Orion Nebula (M42).
Orion lies close enough to the Milky Way to be interesting enough to be swept even with low-power telescopes or binoculars.
Additionally to the data given above there is a skychart to locate the stars and objects.

Stars and objects

The shoulder star alpha Ori, Betelgeuse, is a variable red giant; its brightness varies from 0.4 mag to 1.3 mag with no set period. It belong to the 20 brightest stars in the sky. During it pulsations the diameter of the star varies from 300 to 400 times the diameter of the sun.
The leg of the hunter, beta Ori, Rigel (arab.: the foot), is a blue-white giant of 0.08 mag. This makes it the sixth brightest star in the sky and the brightest in the constellation Orion. With medium sized telescopes it is possible to distinguish the companion of Rigel, a 7th mag star (smaller telescopes may fail to reveal the companion because of the glare of Rigel).
This constellation offers a great number of binaries and multiple stars:
For binoculars and smaller telescopes the following stars are of interest:

delta Ori, Mintaka (arab.: upper end of the girdle), a blue-white star of 2.2 mag with a 7th mag companion.

iota Ori, a 3rd mag and a 7th mag star forming an unequal double; in the same field the wider double

Struve 747 can be found - a pair of a 5th mag and a 6th mag star.

lamba Ori, a tight pair of 4th and 6th mag stars.

sigma Ori is a terrific multiple star; in binoculars this blue-white star of 4 mag and a 7th mag companion can be resolved; using a small telescope two closer companions of 7th mag and 10th mag are revealed. These stars are grouped in a way that they look like a planet with moons.

If the resolution is not too high in the same telescopic field as sigma Ori the triple star Struve 761 can be seen. It consists of a triangle of 8th mag and 9th mag stars. Together with sigma Ori this triple star gives a delightfully rich grouping.

NGC 1981, a little cluster of 10 stars including the binary Struve 750, a pair of a 6th mag and a 8th mag star.

The multiple star theta1 Ori, the northern star of the deggar of the Hunter is also called the Trapezium; it is located in the heart of the Orion nebula. This group of stars has been formed from the gas of the nebula, which now glows in their light. Small telecopes (about 2-inch and higher) show four stars, ranging from 5th mag to 8th mag, which form a rectangular figure. Scopes with an aperture of about 100 mm show two more stars of 11th mag in this group.
Next to it lies theta2 Ori, a duo of a 5th and a 6th mag star.
For resolving the tight double of zeta Ori (Alnitak) in its consisting parts, a bright star of 2.02 mag and a 4th mag companion, scopes with an apertur of at least 75mm and a high resolution are required. Further more there is a wider companion of 10th mag.
Eta Ori is a difficult pair. Scopes with an aperture of 100 mm and higher are necessary to split it into its 4th mag and 5th mag stars.
The constellation Orion became most famous for its nebula. The Messier database has detailed information about The Large Orion Nebula M 42 and M 43, the DeMairan nebula, which is a part of the Orion Nebula.
Around October 21 each year the famous Orionid meteor shower reaches its peak. Coming from the the border to the constellation gemini as much as 20 meteors per hour can be seen. More information about this meteor shower and the Chi Orionids, which are active around the beginning of december can be found in the meteor shower calendar by Gary Kronk. (Readers in the US might use the original site of Gary Kronk).

Mythological Background:

According to greek mythology Orion died being stung by a scorpion. He is set such in the sky that he sets in the west while his slayer, the Scorpius raises in the east.
Followed by his two dogs he is now fighting the bull Taurus.
According to Secrets of the Night Sky (Bob Berman, William Morrow &Co, 1995) the ancient Sumerians saw in this star pattern a sheep. The name Betelgeuse literally means "the armpit"; in case of the Sumerians it meant "the armpit of the sheep."

Source: http://www.seds.org/

Orion

Here's something Hubble reported on last year. I just can't get enough of this picture.

*****

In one of the most detailed astronomical images ever produced, NASA's Hubble Space Telescope captured an unprecedented look at the Orion Nebula. This turbulent star formation region is one of astronomy's most dramatic and photogenic celestial objects. More than 3,000 stars of various sizes appear in this image. Some of them have never been seen in visible light. These stars reside in a dramatic dust-and-gas landscape of plateaus, mountains, and valleys that are reminiscent of the Grand Canyon. The Orion Nebula is a picture book of star formation, from the massive, young stars that are shaping the nebula to the pillars of dense gas that may be the homes of budding stars.

Source: The Hubble Site

Template Change

The old template was not working for me. I converted to blogger beta but chose to use the original blogger template format and tried a few tweaks....that didn't work. I really liked the look of the old template and it was so easy to maintain but sometimes the text spilt out over the post box limit. So, I went looking for something more suitable before the blog got any bigger and I think this will work. Fortunately, I didn't lose any of my comments.

Happy New Year!

To all my friends (and you know who you are) in the astronomy-blog world. May this new year bring you health, happiness and all the good things in life.

Focus on Taurus

The Pleiades star cluster, also known as the Seven Sisters and Messier 45, is a conspicuous object in the night sky with a prominent place in ancient mythology. The cluster contains hundreds of stars, of which only a handful are commonly visible to the unaided eye. The stars in the Pleiades are thought to have formed together around 100 million years ago, making them 1/50th the age of our sun, and they lie some 130 parsecs (425 light years) away. From our perspective they appear in the constellation of Taurus, with approximate celestial coordinates of 3 hours 47 minutes right ascension and +24 degrees declination. For northern hemisphere viewers, the cluster is above and to the right of Orion the Hunter as one faces south, and it transits -- reaches its highest point in the sky, midway between rising and setting -- around 4am in September, midnight in November, and 8pm in January.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ALDEBARAN (Alpha Tauri). Aldebaran is by far the brightest, and therefore the Alpha, star of the constellation Taurus. The ancient name, from Arabic, means "the Follower," as the star seems to follow the Pleiades, or Seven Sisters star cluster, across the sky. Aldebaran, 60 light years away, is positioned in front of the sprawling Hyades star cluster (in mythology, half-sisters to the Pleiades) that make the face of Taurus the Bull, but is not a part of it, the cluster over twice as far away. In most renderings of the constellation, Aldebaran makes the celestial Bull's eye. As part of a constellation of the zodiac, Aldebaran is close to the Sun's path, the Sun passing to the north of it about June 1, the star also regularly covered, or occulted, by the Moon. This class K star, of first magnitude and 13th brightest in the sky, is a low- level irregular variable star that fluctuates erratically and to the eye unnoticeably by about two-tenths of a magnitude. Aldebaran's surface temperature of just under 4000 degrees Kelvin (compared to the Sun's 5800 degree temperature) gives it a distinct orangy color. It is a giant star, a star in an advanced state of evolution in which the interior hydrogen fuel has run out, the star now running on the fusion of helium into carbon. Some 350 times more luminous than the Sun, it has expanded to a radius about 40 times solar, making it big enough to enable astronomers to measure its small angular diameter of only 0.021 seconds of arc (the apparent size of a US nickel seen at a distance of 50 kilometers). This large star is an extremely slow rotator, taking almost two years to make a full spin. If placed at the position of the Sun, Aldebaran would extend halfway to the planet Mercury and would appear 20 degrees across in our sky, making life on Earth quite impossible. Yet Aldebaran may have its own "solar system." Recent, though still-unconfirmed, observations show that the star may be slightly shifting back and forth in response to a small body with a mass at least 11 times that of Jupiter and a two-year orbital period. We do not yet know if the body -- if it exists at all -- is a massive planet or a low-mass "brown dwarf," a failed star that is too small to run supporting thermonuclear reactions in its core.

Source: Jim Kaler, Professor Emeritus of Astronomy, University of Illinois

Missing Old Friends

It's been a while since I've seen some of my old friends - and I'm missing them! The clear -well sometimes- nights in January is the best month for visiting with them.

I'm talking about stars people! I can't wait to see them again so I must start planning now.

Today in Astronomy History

Thomas Henderson 1798-1844

Scotland's First Astronomer Royal

Of all the Astronomers Royal for Scotland, only 3 were Scots, and of these 2 were born in Dundee - Thomas Henderson and Malcolm Longair. Henderson was born on 28 December 1798, the younger son of a tradesman, and educated at Dundee Academy under Thomas Duncan, rector, (later Professor of Mathematics at St Andrews) where he showed a great aptitude for mathematics and science. At 15 he entered a Dundee law office, was promoted to Edinburgh, and eventually became Secretary to the Earl of Lauderdale then to the Lord Advocate.

In Edinburgh he had access to the Observatory of the Astronomical Institution on Calton Hill, which was frequented by various city notables and gentry, and was encouraged by Professors William Wallace and John Leslie to use the modest instruments. On frequent visits to London on legal business he made friends with several astronomers including G. B. Airy, John Herschel and Sir James South who gave him full use of his observatory at Camden Hill. But Henderson had poor eyesight, perhaps a squint, and decided to concentrate on mathematical astronomy rather than observing. In a number of papers he demonstrated computational methods used in Germany but not then common in Britain, and began to be noticed by the astronomers of the Nautical Almanac, Board of Longitude and the Royal Astronomical Society. In 1830 he compiled a list of moon-culminating stars (for determining longitudes by lunar distances) for Sir John Ross's Arctic expedition.

He was turned down as a candidate for the vacant Chair of Astronomy at Edinburgh, (it was under threat of abolition, the previous incumbent, Robert Blair, having treated it as a sinecure for 42 years) and as Superintendent of the Nautical Almanac, but friends persuaded him to accept the post of Astronomer at the Cape of Good Hope. From April 1832 to May 1833, with one assistant, Lieutenant Meadows, and with indifferent instruments, he carried out a prodigious observing programme including a catalogue of the positions of southern stars, estimates of the distance of the sun and moon and observations of comets.

At the Cape he began observations of the exact position with respect to the surrounding stars of the bright star Alpha Centauri which a fellow astronomer had pointed out to him had an unusually high Proper Motion, i.e. its movement against the sky background, although in itself this was very tiny. Henderson surmised that it might be a close star. However, he resigned in 1833 with his health shattered and having had enough of the "dismal swamp" among "slaves and savages".

He returned to Edinburgh, subsisting on a small pension from his legal firm, and calculated his Cape results. The position of Alpha Centauri showed a residual error of about one second of arc (1/3600 of a degree, or 1/1800 of the moon's angular diameter) which was confirmed by observations of the star at the Cape by his successor Thomas Maclear. This was concluded to be the angle of parallax of the star against the background of distant stars, caused by the motion of the earth round the sun, and therefore the first estimate of the distance of a star at about 3.25 light years. (A later measurement gave 0.75 seconds of arc, at about 4.5 light years.) However, the great German mathematician Friedrich Wilhelm Bessel of Konigsberg, working independently and with a much superior instrument and a different method, announced a parallax for 61 Cygni, a somewhat more distant star in the northern hemisphere, 2 months before Henderson, and thereby got the Gold Medal of the Royal Astronomical Society and all the credit. Henderson had been cautious because his instrumentation was suspect, he needed confirming observations and he feared ridicule because false parallaxes had been announced before. Despite this Henderson and Bessel became friends and even holidayed in Scotland together.

In 1834 the Astronomical Institution of Edinburgh was in financial trouble. It was arranged that the Calton Hill Observatory be taken over by the government to run as a state establishment with the Observer to be jointly Regius Professor in Edinburgh University and Astronomer Royal for Scotland. Henderson was duly elected, supported by his many distinguished friends, and during the last 10 years achieved another prodigious workload with the help of his assistant Alexander Wallace, although he did very little teaching. He made some 60,000 observations, which amazed his successor Charles Piazzi Smyth, and many were published in the first volumes of The Edinburgh Astronomical Observations, but later errors were found, caused by the irregular thermal expansion of the stone pillars of the Fraunhofer transit telescope. He was a Fellow of the Royal Societies of Edinburgh and of London, but never took a degree.

But the daily climb up the hill from his official residence at 1 Hillside Crescent, and the death of his wife in 1842, were too much for a frame already weakened by heart disease. He died on 23 November 1844 and is buried in an almost forgotten corner of Greyfriars Churchyard. There is a memorial tablet to him on the west side of the Playfair Building. No proper portrait of him is known to exist.

Catching the Light

I really enjoy looking at photos others have taken of the heavens and I admire anyone who has the patience to go out there and give astro-photography a go.

Here’s a link to a great site. Catching the Light.

Meteor Showers 2007

January
Quadrantids January 3-4 Frequency:		Typically, 40 or so bright, blue and fast (25.5 miles per second) meteors will radiate from the constellation Bootes, some blazing more than halfway across the sky. A small percentage of them leave persistent dust trains. This shower usually has a very sharp peak, usually lasting only about an hour.
Parent Comet: 2003 EH1
April
Lyrids April 21-22 Frequency:		The swift and bright Lyrid meteors disintegrate after hitting our atmosphere at a moderate speed of 29.8 miles per second. They often produce luminous trains of dust that can be observed for several seconds.
Parent Comet: C/Thatcher
May
Eta Aquarids May 5-6 Frequency:
Parent Comet: 1P/Halley
June
Lyrids June 14-16 Frequency:		The June Lyrids is a low-rate shower during which you could see up to 10 meteors per hour during its peak.
July
Delta Aquarids July 28-29 Frequency:		At peak time about 20 bright, yellow meteors can be observed per hour. Because these meteors nearly broadside the Earth, their speed is a moderate 25.5 miles per second.
Capricornids July 29-30 Frequency:		The Capricornids are characterized by their often yellow coloration and their frequent brightness. They are also slow interplanetary interlopers, hitting our atmosphere at around 15 miles per second. Though you can expect only 15 meteors per hour at best under dark sky conditions, the Capricornids are noted for producing brilliant fireballs.
August
Perseids August 12-13 Frequency:		This shower produces about 60 meteors per hour, and its performance is farily consistant from year to year.
Parent Comet: 109P/Swift-Tuttle
October
Draconids October 8-9 Frequency:		Expect a peak rate of 10 meteors per hour under clear, moonless conditions.
Parent Comet: 21P/Giacobini-Zinner
Orionids October 21-22 Frequency:		This shower produces a peak rate of 20 yellow and green meteors per hour, which are fast moving at 41.6 miles per second and are known to produce fireballs.
Parent Comet: 1P/Halley
November
Leonids November 17-18 Frequency:		The Leonids are best known for their 33-year peaks, during which 100s of meteors per hour can be observed. The last of these peaks occured in 2001.
Parent Comet: 55P/Tempel-Tuttle
December
Geminids December 13-14 Frequency:		The most reliable meteor shower of the year, the Geminids are characterized by their multi-colored display--65% being white, 26% yellow, and the remaining 9% blue, red and green.
Parent Comet: 3200 Phaethon

Source: Skyscrapers, Inc.

Ice Age Map of the Night Sky

A painted map of the prehistoric cosmos is on the wall of a famous Ice Age cave at Lascaux in central France.

Cro-magnon man — distant ancestors of humans living much later than the earlier Neanderthals and Aurignacians — painted the Lascaux caves with drawings of bulls, horses and antelope some 16,500 years ago. Thus, the map may be 16,500 years old.

The Ice Ages were cold periods in ancient history when glaciers descended across the northern continents and then receded. The temperatures experienced by humans and their ancestors alternated between cold and warm. Scientists say there have been at least four Ice Ages. Today, when people speak of "the Ice Age," they usually refer to the most recent glacial period, which ended about 8,000 years ago.

Summer Triangle. The painted walls of the Lascaux caves were discovered in 1940. The sky map was identified year later in a region of the Lascaux caves known as the Shaft of the Dead Man. Painted on to the wall of the shaft is a bull, a strange bird-man and a mysterious bird on a stick.

Since it was in the time we call pre-history — before people started recording history — no one knows if a cave could have been used as a kind of planetarium where stars were charted.

European researcher Michael Rappenglueck, however, suggests that it is a map of three particular stars — Vega, Deneb, Altair — that astronomers today refer to the Summer Triangle. Those stars are among the brightest objects in the sky during the middle of a northern summer. Rappenglueck sees the eyes of the bull, bird-man and bird as representing Vega, Deneb and Altair.

Source: Space Today Online

Heavyweight Stars Light Up Nebula NGC 6357

The small open star cluster Pismis 24 lies in the core of the large emission nebula NGC 6357 in Scorpius, about 8,000 light-years away from Earth. Some of the stars in this cluster are extremely massive and emit intense ultraviolet radiation. The brightest object in the picture is designated Pismis 24-1. It was once thought to weigh as much as 200 to 300 solar masses. This would not only have made it by far the most massive known star in the galaxy, but would have put it considerably above the currently believed upper mass limit of about 150 solar masses for individual stars. However, high-resolution Hubble Space Telescope images of the star show that it is really two stars orbiting one another (inset pictures at top right and bottom right). They are estimated to each be 100 solar masses. The Hubble Advanced Camera for Surveys images were taken in April 2006.

Source: The Hubble Site