Our summer almanac 20.08.2010 – 26.08.2010


The Veil Nebula
The Veil Nebula, is part of the Cygnus Loop, radio source W78, or Sharpless 103. Other parts of the loop include the ‘Eastern Veil’, the ‘Western Veil’ or ‘Witch’s Broom Nebula’, and Pickering’s Triangular Wisp. It is a large, relatively faint supernova remnant in the constellation Cygnus.

The source supernova exploded some 5,000 to 8,000 years ago, and the remnants have since expanded to cover an area of ~3×3 degrees; about 6 times the diameter or 36 times the area of a full moon. The distance to the nebula is not precisely known, with estimates ranging from 1,400 to 2,600 light-years. It was discovered on 1784 September 5 by William Herschel.

Detail of the Veil Nebula as photographed by the Hubble Space Telescope.

The Moon is shrinking!

It was announced by NASA on 19 August that the Moon is shrinking!

The NASA website says:
NASA’s LRO Reveals ‘Incredible Shrinking Moon’

ewly discovered cliffs in the lunar crust indicate the moon shrank globally in the geologically recent past and might still be shrinking today, according to a team analyzing new images from NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft. The results provide important clues to the moon’s recent geologic and tectonic evolution.

The moon formed in a chaotic environment of intense bombardment by asteroids and meteors. These collisions, along with the decay of radioactive elements, made the moon hot. The moon cooled off as it aged, and scientists have long thought the moon shrank over time as it cooled, especially in its early history. The new research reveals relatively recent tectonic activity connected to the long-lived cooling and associated contraction of the lunar interior.

“We estimate these cliffs, called lobate scarps, formed less than a billion years ago, and they could be as young as a hundred million years,” said Dr. Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum, Washington. While ancient in human terms, it is less than 25 percent of the moon’s current age of more than four billion years. “Based on the size of the scarps, we estimate the distance between the moon’s center and its surface shrank by about 300 feet,” said Watters, lead author of a paper on this research appearing in Science August 20.

“These exciting results highlight the importance of global observations for understanding global processes,” said Dr. John Keller, Deputy Project Scientist for LRO at NASA’s Goddard Space Flight Center, Greenbelt, Md. “As the LRO mission continues in to a new phase, with emphasis on science measurements, our ability to create inventories of lunar geologic features will be a powerful tool for understanding the history of the moon and the solar system.”

The scarps are relatively small; the largest is about 300 feet high and extends for several miles or so, but typical lengths are shorter and heights are more in the tens of yards (meters) range. The team believes they are among the freshest features on the moon, in part because they cut across small craters. Since the moon is constantly bombarded by meteors, features like small craters (those less than about 1,200 feet across) are likely to be young because they are quickly destroyed by other impacts and don’t last long. So, if a small crater has been disrupted by a scarp, the scarp formed after the crater and is even younger. Even more compelling evidence is that large craters, which are likely to be old, don’t appear on top any of the scarps, and the scarps look crisp and relatively undegraded.

As the moon contracted, the mantle and surface crust were forced to respond, forming thrust faults where a section of the crust cracks and juts out over another. Many of the resulting cliffs, or scarps, have a semi-circular or lobe-shaped appearance, giving rise to the term “lobate scarps”. Scientists aren’t sure why they look this way; perhaps it’s the way the lunar soil (regolith) expresses thrust faults, according to Watters.

Because the scarps are so young, the moon could have been cooling and shrinking very recently, according to the team. Seismometers emplaced by the Apollo missions have recorded moonquakes. While most can be attributed to things like meteorite strikes, the Earth’s gravitational tides, and day/night temperature changes, it’s remotely possible that some moonquakes might be associated with ongoing scarp formation, according to Watters. The team plans to compare photographs of scarps by the Apollo Panoramic Cameras to new images from LRO to see if any have changed over the decades, possibly indicating recent activity.

Raksha Bandhan August 24
Raksha Bandhan is the Hindu festival that celebrates brotherhood and love. “Raksha Bandhan” means a thread for protection.
Raksha Bandhan celebrates brotherhood and love. It is celebrated on the full moon in the month of Sravana in the lunar calendar.

The word Raksha means protection, whilst Bandhan is the verb to tie.

Traditionally, during the festival sisters tie a rakhi, a bracelet made of interwoven red and gold threads, around their brothers’ wrists to celebrate their relationship.

Breaking news 25 August
The Guardian reports: New solar system looks much like home.
The newly discovered solar system may contain the largest number of planets ever found orbiting another star. Astronomers have discovered a new solar system 127 light years away that is tantalisingly similar to our own.

The team used observations from the European Southern Observatory (Eso) in Chile to find five Neptune-like planets orbiting a Sun-like star called HD 10180. The planets are closer to their star than Mars is to the Sun.

They also have some evidence that two more planets might be in the star system, one of which would have the lowest mass of any extrasolar planet ever found. If the existence of these two additional planets is confirmed, the discoveries would make the HD 10180 solar system very similar to our own, with seven planets (to our eight) and a regular pattern of orbits. “We have found what is most likely the system with the most planets yet discovered,” said Christophe Lovis of the University of Geneva in Switzerland. “This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system.”

The five gas giants are between 13 and 25 times as massive as the Earth and take between six and 600 days to orbit the star, writes Lovis in a paper published in the journal Astronomy and Astrophysics.

One of the two as-yet-unconfirmed planets is likely to be similar to Saturn, with a minimum mass of around 65 Earths and an orbit of 2,200 days. The other planet would be the least massive exoplanet ever discovered, say astronomers, with a mass around 1.4 times that of the Earth.

The similarities end there, however. The rocky planet is likely to orbit very close to its star – just 2% of the distance between the Earth and the Sun. A single “year” on this planet would last only 1.18 Earth days. Scientists have confirmed the existence of 15 “extrasolar systems” that have at least three planets and the previous record-holder was 55 Cancri, which has five planets in orbit around it.

The latest discovery was announced today at an international meeting at the Observatoire de Haute-Provence in France.

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