SJAA Ephemeris November 2011 | SJAA Home | Contents | Previous | Next

The Last Month in Astronomy

In the image to the left, an ALMA image from the submillimeter section of the electromagnetic spectrum is superimposed over an image taken by the Hubble Space Telescope. In the middle is a picture of the ALMA installation with about one third of the antennae in place. The dishes (there will be 66 of them eventually) can only be separated up to 125 meters but will some day be separated up to 16 km. That separation greatly increases the resolution of the images. The third image shows the Antennae galaxies (NGC 4038, 4039). These are spiral galaxies colliding. The top image is from the ESO Very Large Telescope (VLT). The bottom image is from ALMA. The ALMA complex and the VLT are both located in the Atacama desert region of Chile. ALMA is at an altitude of 5000 meters. The VLT is 2635 meters high. Photo credit is B. Saxton, (NRAO/AUI/NSF), ALMA (ESO/NAOJ/NRAO). Visible light image: the NASA/ESA Hubble Space Telescope


OCT-10-2011 • Neptune 16 hour day • Neptune’s day has been calculated to be 15 hours, 57 minutes and 59 seconds. A quick Google search finds estimates like 19.1 hours, 16.11 hours, 16 hours plus 6 minutes. This new estimate was done by Erich Karkoschka of the University of Arizona. He used 500 images from Hubble taken over the 20 year history of the HST. He found 2 objects that appear to be consistent, the South Polar feature and the South Polar Wave. He found 6 more objects on the more detailed images from the 1989 Voyager flyby of Neptune.

OCT-07-2011 • Uranus many hits • New simulations suggest that Uranus must have been hit by multiple large objects. Previously it was thought that one large object might have knocked Uranus so that its rotational axis is knocked over 90 degrees from what other planets are. “Having shown that giant collisions had to happen frequently on these planets (Uranus and Neptune) is an important piece of information on the way to understanding their origin” according to Alessandro Morbidelli from the Observatory of Cote d’Azur in Nice, France. But others like Steven Desch of ASU thinks it is unlikely that two large objects could be created and then slammed into Uranus.

OCT-06-2011 • Old photos show planets • A reanalysis of Hubble images from 1998 show large planets around HR 8799. These planets were not noticed earlier. Two things made it easier to find them now. First, the planets were detected by earlier methods in 2007 and 2008. Second, new processing abilities improve resolution by a factor of 10. This is the first multi-exoplanet system to be directly imaged - unless some other pictures are waiting to be reanalyzed.

OCT-05-2011 • Kuiper Belt Oceans • The Herschel Space Observatory has analyzed the hydrogen isotopes on comet Hartley 2. The ratio of deuterium to normal hydrogen atoms is the same as it is in the oceans. This suggests that Kuiper Belt objects like the short period Hartley 2 probably played a major role in the delivery of water to Earth. Other comets that have been studied have longer orbits and are therefore more likely to be from the Oort Cloud. These Oort cloud objects have more deuterium. When water has higher ratios of deuterium it is called “heavy water”.

OCT-04-2011 • Nobel Winners • The discovery that the expansion of the universe is accelerating resulted in a Nobel Prize for Saul Perlmutter (Berkeley), Brian Schmidt (Australian National University), and Adam Riess (Space Telescope Science Institute). Riess said “My involvement in the discovery of the accelerating universe and its implication for the presence of dark energy has been an incredibly exciting adventure. I have also been fortunate to work with tremendous colleagues and powerful facilities.” Alex Filippenko, our scheduled speaker for January 7, 2012, was also heavily involved with this research.

OCT-03-2011 • ALMA First Light • The Atacama Large Millimeter/submillimeter Array (ALMA) is only one-third complete but images are already being released. According to Tim de Zeeuw, the Director General of ESO (the European partner in ALMA) “Even in this very early phase ALMA already outperforms all other submillimeter arrays.” The online versions of this newsletter include some images from ALMA.

SEP-29-2011 • Shrinking Asteroids • The Wide-field Infrared Survey Explorer (WISE) spacecraft has found that there are fewer than 20,000 near-Earth asteroids of the mid-size variety (330-3300 feet wide). Previous estimates suggested that 35,000 such objects exist. Are we safer than we thought? Not necessarily. It is not clear that the number of hazardous asteroids (the closest to Earth) is less than expected. The WISE spacecraft was also used to rule out the possibility that a piece of an asteroid named Baptistina was the impactor that led to the demise of the dinosaurs.

SEP-15-2011 • Tatooine • The Kepler research team has found a planet that orbits two stars (called a circumbinary orbit). Lawrence Doyle (SETI Institute) said “Most of what we know about the sizes of stars comes from such eclipsing binary systems, and most of what we know about the sizes of planets comes from transits. Kepler-16 combines the best of both worlds.” The planet (Kepler-16b) is very cold and about the size of Saturn. The planet completes an orbit in 229 days, about the length of a Venusian year. The binary stars are in an eccentric orbit of 41 days but the planet’s orbit is nearly circular. The two stars are .2 and .69 solar masses. The reference to Tatooine is from Star Wars, the home planet of Luke Skywalker.


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