April 18, 2014

27.04.11: Detecting “Exo-Aurorae.”

Saturian aurora seen in the infrared via the Cassini spacecraft. (Credit: NASA/JPL).

Planetary Scientists may soon have a new technique in their arsenal in the hunt for exo-solar planets. Current tried-and-true methods involve measuring tiny radial velocity shifts, catching a gravitational lensing event, or watching and measuring a tiny dip in brightness as a planet transits its host star. [Read more...]

04.06.10- “Hot Jupiters” in Retrograde.

An Artist's family portrait of retrograde exo-worlds. (Credit: ESO/A. C. Cameron).

An Artist's family portrait of retrograde exo-worlds. (Credit: ESO/A. C. Cameron).


   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!

24.04.10-Our Existence: Justified.

(Credit: NASA/JPL).

(Credit: NASA/JPL).

 Earth: Safe & Sound?

   The formation of the Earth poses a key dilemma to planetary accretionary theory; namely, why are we here at all? Standard models would say that the Earth and other planets coalesced out of the proto-solar nebula to form. However, spiral density waves within the same nebula should have drawn down orbital energy to shorten the planets orbit, slowly drawing it in. Looking at other “hot Jupiter” systems, that’s just what we see; large gas giant worlds that formed further out, only to migrate inward into tight orbits… just how did we end up in our nice, neat orbit?

Now, computational astrophysicist Mordecai-Mark Mac Loc at the American Museum of Natural History may have the answer. Accounting for temperature and spin variability, resonance key holes can occur; planets like Earth may simply spiral inward and get hung up in these safe zones between dragging pressure waves. Of course, a majority of proto-planets don’t make the cut and simply spiral inward to a fiery end, but they’re not around for us to see today. One discovery that would perhaps give observational weight to this theory would be the discovery of exo-Earths also parked in nice neat orbits… the Kepler space telescope may pave the way for this discovery as it stares off into Cygnus. For now, thank computational mathematics that you’re here reading this, just as it says you should be!

Astro-Challenge: What’s so Special About 51 Pegasi?

A northern hemisphere finder chart for 51 Peg, looking NW after dusk. (Created in Starry Night).

A northern hemisphere finder chart for 51 Peg, looking NW after dusk. (Created in Starry Night).

It’s hard to imagine a time before we knew of worlds beyond our own solar system. These days, extra-solar (or “exoplanets”) are back page news, as discoveries occur almost daily.  But scant decades ago (Waaay back in the pre-Internet Stone Age of the early 1990’s) no exoplanets were known, and the entire field was open to great conjecture. This was also one of the great variables underpinning the famous Drake Equation which attempts to quantify how many intelligent civilizations might exist in our galaxy; i.e. “how many stars possess solar systems?” That all changed in the 90’s, and the discovery of a planet in October 1995 by Geoffrey Marcy and Paul Butler orbiting the star 51 Pegasi in the constellation Pegasus was pivotal in opening the flood gates. [Read more...]

26.10.09:Seeing Starspots.

A simulation of Corot-2a with transiting hot Jupiter and starspots. (Simulation and phot by author).

A simulation of Corot-2a with transiting hot Jupiter and starspots. (Simulation and photo by author).

We know more about our Sun than any other star because it gives us the opportunity to study solar activity up close. But just how normal is it? Recently, astronomers have been able to spy activity on other suns, teasing the data out of exoplanet transits. These are planets that happen to cross the tiny visible face of their parent star as seen from our line of sight and thus exhibit a tiny but measurable dip in their apparent brightness. Earlier this year, a team at the Hamburg Observatory has been refining this technique by monitoring the star Corot-2a. A younger Sun-like star, Corot-2a spins once every 4.5 earth days and possesses a transiting “hot Jupiter” which orbits once every 1.74 days. Examining a statistical analysis of the light curve as seen by the European Space Agencies’ (ESA) prolific Corot space observatory has yielded “notches” in the smooth curve, a tell-tale sign of “starspot” activity. This was conducted over 80 successive transits. The goal is to begin puzzling together a “butterfly diagram” for alien suns, much like the familiar 11 year cycle diagram yielded by Sporer’s Law for our own Sun. Doubtless, other suns follow different cycles, and this data will add to our understanding of stellar evolution. This will also answer such questions about our own Sun, such as; why do sunspots never form above a particular latitude? Are there larger interwoven cycles? And just what was our Sun like in its juvenile days?

02.10.09: A Small Observatory Helps with a Big Discovery.

Stately Rosemary Hill Observatory in Bronson, Florida. (Credit: University of Florida).

Stately Rosemary Hill Observatory in Bronson, Florida. (Credit: Dr. Francisco Reyes).

When it comes to cutting edge astronomy, many think of lofty mountaintop behemoths, such as Keck, or the orbiting Hubble Space Telescope. But how many of us think of… Gainesville, Florida? This article caught my eye this morning because its literally right in our backyard here at Astroguyz HQ in Hudson, Florida. As any would-be Floridian astronomer knows, the Sunshine State is not an optimal environment for astronomy, as humid, damp, East Coast conditions predominate. But that didn’t stop astronomers at the University of Florida in Gainesville from using the Rosemary Hill Observatory in nearby Bronson to help with observations of a transiting exoplanet; HD 80606b. 200 light-years distant, this hot-Jupiter is in an extremely eccentric orbit and was only recently realized to be a transiter, i.e. to occasionally pass in front of its host star as seen from Earth. Astronomers, however, were faced with a problem; the next transit was due occur June 4th of this year, when HD 80606b would be low in the twilight sky. This meant that observations of the eclipse could only occur over a short span from any given longitude. Enter U of F astronomers Ford, Reyes and Colon, who realized that Rosemary Hill might just be positioned to catch such an event. Located, as is most of Florida, at a scant 140 feet above sea level, Rosemary Hill may just qualify as the “lowest” observatory in the world. It sports 30” and 18” reflecting telescope(s), which are primarily used for education and training, as the U of F astronomers tend to travel to the “big guns” in the Canary Islands for “serious” research. The night of the 4th, however, Rosemary Hill showed its stuff; as a participating observatory in Massachusetts was clouded out, leaving the Gainesville astronomers as key to gathering data at their respective longitude. Colon noted that the experience of actually guiding the telescope and monitoring the star during transit was “definitely unique” and different from the remote observing now prevalent at larger observatories… the data gathered will go far towards understanding this bizarre exoplanet and its 111 day orbit. And the moral of the story is…every telescope can contribute, even your home town observatory!