January 2008

2008.01.12
Local:Atalaia (Montijo 38º44N 8º48W)

Atalaia XXX

Another great gathering night at Atalaia, despite the annouced death of the already not very abundant dark sky. They had to plant an international airport within 500 metes from us.
The threatening satellite images did not waver the many who were there, and for whom, used the time as weel spent, which might have been perhaps for me the shortest that I spent there, all thanks to the clouds that began to slowly emerge from midnight. There was a lot of humidity, temperature of about 5 degrees, eyes fogged the eyepiece by only looking, but to compensate the turbulence was generally low. The SQM marked 20.40.

This time, I took my veteran telescope of many open skies, the 20cm dobson , which at the moment is unfit for consumption of double stars and planetary images, the broken collimation screw, but will also serve to see naturally fuzzy objects like the comet Tuttle sketched below.

This comet,visit us each 13 years, is about to reach its perihelion (27 January), moving through the sky at the time of observation apparently -0.58 degrees / day in RA and -2.47 degrees in declination, vertigionous falling through the constellation of Whale (Cetus), which at the time was already very attenuated by the Montijo's light pollution dome. Nevertheless, was quite noticeable, as a low condensed rounded nebula ,with no tail.

The amazing comet 17P Holmes is still an naked eye object , found a little less than two degrees from Algol (Beta Persei) in the Perseu constellation.

Comet P/Tuttle 8P (20080112 2200 UT)

I've focused then on the current season favorite cluster , the NGC 2264.
This cluster is interesting for several reasons. In a telescope that reverses the image, as a Newtonian, it is quite similar to the triangular shape of a Christmas tree, but with a "star" on the base and not on top, dominating the cluster, or more accurately an association (OB), occupies about half a degree field, which in panoptic 24mm field was well framed.
This young association extend some 2400 light-years from us. The associations, unlike clusters are groups of stars that are not gravitional associated , and the more remote, the oldest will be. This is very compact and has involved a large region full of nebulae and dust, responsible for the spectacularly colorful long exposure images , such as "Cone" Nebula and "Fox Furr " - unfortunately visually weren't even suspicious.
The star above (S Monocerotis) is however very special, being a star type O7.5III Vf ( before you that change channel, , O7.5 - temperature between 25000 ° - 45000 ° Kelvin, III-V light giant-dwarf f issuing the lines of helium and nitrogen), is almost nearing the top of the scale of temperatures of stars. Even at a distance of 1020 ± 230 light-years, she shines in our eyes at around magnitude 5. Stars with this flaregrant brightness are very rare, and by this relatively rare to find, much less visually as has been the case.

At a little less than two degrees, the Hubble's variable nebula, (NGC 2261) is in it's turn illuminated by the R Monocerotis, which can not be observed at visible light (or with the even with Hubble telescope) but is very close to a 10 magnitude star (TYC 746 1024), which served as a modest beacon. The nebula was visible only using the averted vision, too faint to catch its characteristic form of comet, I had no choice left but to random blur the paper with the fingertip. In the absence of better, here is an image that made 3 ago here in the Patio.

The variability of this nebula is already known since 1861, but became famous for being one of the first images made by Edwin Hubble with just inaugurated Mount Palomar's 200" Hale Telescope in 1947. He noted when comparing two images separated by a few years that the nebula had different brightness. Since then variations in the brightness up to 4 magnitudes have been observed , which depends not only of the variation of the star, but also the movement local dust. The responsible star is buried in 200 AU of dust, and seems to have all signs of a star birth: lots of dust, gas and lots of action, with accretion and loss of mass simultaneously. The R Monocerotis will be a star-type A or B with twice the mass of our Sun, its partner 1.5 solar mass T-Tauri , will form as usual, another fine double stars.

NGC 2261 & NGC 2264

Worth of notice was a curious grouping of Saturn's satellites brightest excluding Titan, planet wich presented his rings much less inclined than has been usual in recent years. A "cigar" galaxy M82 (if perhaps it is time to choose a more politically correct nickname ), presented good detail of the it's many dust veins. All this on the Alberto's Obsession 15" , where also an attempt was made to observe the elusive Sirius B, however getting only a telescopic memory of the brightest star in the sky fused on the retina.

A delightfull and well attended night, opening the new season at Atalaia. As always, there is are more to read and see at www.atalaia.org . .

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