Circumhorizontal Arc

Circumhorizontal arcs (pictured here) occur only between 55 degrees South and 55 degrees North, usually near the time of the respective summer solstice. They are formed by plate-shaped ice crystals in high level cirrus clouds. Other accepted names for circumhorizontal arcs are circumhorizon arc and lower symmetric 46° plate arc. Due to their large angular size they are rarely seen complete and most often appear as part of a cloud, as seen here on May 23, 2012 at 39°36'5"N, 74°20'17"W.

May 23, 2012    39°36'5"N, 74°20'17"W     (Click for full-size image)

The Cosmic Coincidence

Cosmologists tend not to get all that excited about the universe being 74% dark energy and 26% conventional energy and matter (albeit most of the matter is dark and mysterious as well). Instead they get excited about the fact that the density of dark energy is of the same order of magnitude as that more conventional remainder. (Image adapted from Lineweaver and Egan. The Cosmic Coincidence as a Temporal Selection Effect Produced by the Age Distribution of Terrestrial Planets in the Universe (subsequently published in Astrophysical Journal 2007, Vol 671, 853.)

Source: Cosmic coincidence (Physorg.com)

Triple Eclipsing Variable Star System - But Stranger Than That!

Normally, a binary eclipsing variable star system is characterized by a change of aggregate brightness as one star eclipses the other from the vantage point of Earth. Described in the report below however is a triple system with the weird feature that when both of the smaller stars are in front of the larger star, the brightness barely changes. This is due to the fact that despite vastly different sizes, the stars have almost the same surface brightness, and as described below, "just as a white rabbit cannot be seen in snow-fall, the red dwarfs in front of the red giant are also almost invisible"!

From Physorg:

The object, catalogued as HD 181068 and nicknamed `Trinity' by the research team, and is a seventh magnitude star that is almost visible to the naked eye. University of Sydney astronomer Daniel Huber from the School of Physics says: "We found what was a seemingly single star is in reality a complex triple system in which three stars reside in a very special geometry.

The observations we have show mutual eclipses as each of the stars gets behind or in front of the others. The most luminous object is a red giant star around which a close pair of two red dwarfs orbits with a period of 45.5 days." Lead author on the paper Aliz Derekas from the Eotvos University and Konkoly observatory, Budapest, Hungary says: "Thanks to the fortunate viewing angle from Earth, the combined light from the three stars change very characteristically. There are sharp brightness decreases with a period of 0.9 days produced by the mutual eclipses of the close pair of dwarfs, while it takes two days for the close pair to pass in front of or behind the red giant.

"A mind-boggling feature of the variations is that when the red dwarfs are in front of the red giant, their short-period eclipses disappear. This is because the surface brightness of the three stars are actually very similar, and just as a white rabbit cannot be seen in snow-fall, the red dwarfs in front of the red giant are also almost invisible, hence no light is lost when they eclipse each other." 

To the Editor #2 - Kevin Myers

Another letter to the editor found on the old machine. The Irish Independent article is here, which was in response to the column by Kevin Myers here. Maybe Kevin and this guy should get together...

Y-Leonis

I just came across some data from when I was studying physics... This is a light curve of the eclipsing binary system Y-Leonis published and validated by the American Association of Variable Star Observers. The data was collected with a 0.41m (16") telescope with f/8 Ritchey-Chretien optics on an open fork equatorial mount. There is a Santa Barbara Instrument Group (SBIG) ST-1001E large format, megapixel CCD camera mounted to the telescope via a custom filter wheel. The camera head is thermoelectrically cooled and regulated to operate at a temperature of -40C. I have another lightcurve at the AAVSO. You can generate this curve by entering the Julian date range 2452723.559 - 2452723.875. My observer code is BBD.

NGC 4921

Click Here For Link To Hi-Res 

This very deep image taken with the NASA/ESA Hubble Space Telescope shows the spiral galaxy NGC 4921 along with a spectacular backdrop of more distant galaxies. It was created from a total of 80 separate pictures through yellow and near-infrared filters.

Credit:

NASA, ESA and K. Cook (Lawrence Livermore National Laboratory, USA)

No Extraterrestrial Life...? Try Getting a Life!

Is this guy nuts? (click here)

According to him, since it has been determined that 500 exoplanets are too inhospitable to support life as we know it there must be no extraterrestrial life in the universe. WHAT?

Let's do come quick quick back-of-the-envelope calculations:

There are approximately 100 × 10²² stars in the observable universe. Let's be sceptical and say, i don't know,  that one in 500 (Professor Smith's magic number) stars have one planet. That leaves 20 × 10²⁰ planets. That is 2,000,000,000,000,000,000,000 planets.  We just searched 500 of them, and came to an amazing conclustion that there is no other life in the universe. If we are stupid enough to subtract 500 from that number that leaves 1,999,999,999,999,999,999,500 planets. Let's say that we discover a new exoplanet per second. (Yeah right). It will take 63,419,583,967,529 years to search them all. That is 4,530 times longer than the universe has been in existence just to check them all. I think that perhaps Professor Smith was just a bit too early off the mark with this one.

Just to make you feel more sane, here's a new solar system to play with. And if that got boring, here's five more planets.