May 27, 2020

04.06.10- “Hot Jupiters” in Retrograde.



A unique battery of telescopes is revealing an unusual feature in many exoplanetary systems. Earlier this year, the Royal Astronomical Society unveiled nine new exoplanets, transiting “hot Jupiters” that cross the face of their parent star as seen from Earth. No big deal nowadays, as the exoplanet count sits at 455 and climbing, and at the time of discovery, 73 transiting exoplanets were known. What makes these beasties so unusual is that they all orbit their host in retrograde orbits. That is, their orbits run counter to their host stars’ rotation.  And just how do you discern the direction of motion for a transiting exoplanet? That’s our impromptu astro-vocabulary builder term of the day; the Rossiter-McLaughlin Effect.  The motion of a spinning star can be discerned in its spectra; the approaching limb is ever so slightly blue shifted, and the receding limb is red shifted. Enter our dark transiting body. When the planet enters the frame, a slight but perceptible “spectral mis-match” occurs; if this occurs in the blue shifted portion, the orbit is prograde; in the red shifted end, the orbit is retrograde. The observations were conducted via the Super-WASP (Wide Angle Search for Planets) consortium. This is a pair of robotic instruments each consisting of eight CCD coupled telephoto lenses (they’re Canon 200mm f/1.8s!) each capable of capturing a field of view 7.8° degrees square. Super-WASP North is located in the Canary Islands, while Super-WASP South is stationed at the site of the South African Observatory. These enable a cost affordable way to survey the entire sky looking for the tiny signature dimming of a transiting exoplanet. Conceived in the 1990s by Don Pollacco, Super-WASP has identified 26 extra-solar planets to date. How these retrograde hot Jupiters came to be remains to be solved… but it is still truly awesome how much data we can glean from a tiny string of photons!

30.10.09:The World’s Largest Telescope is Unveiled.

Move over Keck… the world’s largest telescope is now in service! The Gran Telescopio Canaris (GTC) was commissioned this summer on July 24th. Perched on La Palma island in the Canary Islands, this beast sports a 10.4-meter segmented mirror. This gives it a collection area over 6 square meters larger than contending 8 to 10 meter instruments world-wide. A joint effort of Spain, Mexico, and the University of Florida, this instrument is expected to further push back our understanding of the frontiers of astronomy. Of course, as reported earlier, bigger scopes are on the drawing board; but as astronomy moves out beyond the Earth’s atmosphere, the age of the terrestrial mega-scope may be coming to an end in our lifetime. Scopes like the GTC rely of computer sensors to keep its 36 mirror segments aligned and acting as one. This is much easier than the old school method of casting one giant parabolic mirror, which would be cumbersome and nearly impossible from an engineering standpoint. The GTC sits at an altitude of 2,400 meters, well above a good bulk of the blurring atmosphere. Other scopes, such as the Large Binocular Telescope (LBT) on Mount Graham, Arizona, rely on a technique known as interferometry to increase resolution. This places two telescopes along a precisely measured base line, and thus provides the resolution of one large mirror. Terrestrial scopes up to 100 meters (!) in size have been proposed and are on the drawing board…let the scope wars begin!

4.10.9:A Gamma-Ray Burst for the Record Books.

A Gamma-ray burst from the primordial universe sent astronomers reeling earlier this year with the most distant sighting yet. The burst was picked up by NASA’s Swift spacecraft on April 23, 2009 at 3:55 EDT. E-mails and instant messages flew to observatories around the globe as astronomers raced to pin-point the fading afterglow. Dubbed GRB 090423, (get the year/month/day thing?) This burst measures in at a redshift of 8.2, or a distance of 13.035 billion light years. This hails from a time when the universe was a tender young age of only 630 years old, young, compared to our circa 14 billion year current age. The old record was a red shift of 6.7 set in September 2008. the current “holy grail” in cosmology is to break the “redshift 10″ barrier, which may well happen in the coming year. A gamma-ray burst occurs when a super massive star collapses into a black hole, briefly creating a “hyper-nova” in the process. Such events are the most luminous in the universe and are thought to have been common amoung first generation stars. Backup observations were provided by Italy’s Galileo national telescope in the Canary Islands and the ESO’s Very Large Telescope in Chile.