April 24, 2014

12.06.10: Refurbished Hubble Catches Interstellar Speedster.

Runaway star as seen from the HST. (NASA/ESA/C. Evans/N. Walborn).

Runaway star as seen from the HST. (NASA/ESA/C. Evans/N. Walborn).

 

     New instruments installed aboard the Hubble Space Telescope on the final repair mission are now starting to really show their stuff. Recently, astronomers revealed a new find; a massive star speeding away from the Tarantula Nebula. Located 170,000 light years distant in the Large Magellanic Cloud, this nebula is also sometimes referred to as 30 Doradus or NGC 2070. At the heart of the nebula is a star forming region known as R136. The star in question is speeding outward at an amazing 250,000 mph, or almost 70 miles a second. This would easily span the Earth-Moon distance in one hour! Already, the star has covered about 375 light years in its young estimated 1 to 2 million year long life. What accelerates a star to such a dizzying velocity? One event capable is a nearby supernova explosion. This is unlikely, because any of the siblings within 30 Dor would have been equally young. Another, more likely scenario is that this star had several early encounters with neighboring stars and promptly got flung out of the nebula. 30 Dor boasts several stars in the massive 100+ solar mass category, and is home to some of the largest stars known in the nearby universe.  First indentified in 2006 during a survey conducted at the Siding Spring Observatory in Australia, astronomers got a new view of the stellar runaway when they used it as a calibration target for the newly installed Cosmic Origins Spectrograph. They found a star perhaps 90 times the mass of our Sun unleashing furious stellar winds and carving an enormous bubble in space. COS conducts its observations primarily in the ultraviolet. Observations also confirmed that this star is one single massive entity, and not a close spectroscopic binary. Massive stars such as this are destined for a short life, ending its fusion role as a supernova and eventually leaving a remnant black hole.

07.06.10: Mega-Scope Site Selected.

An Artists' Conception of the E-ELT. (Credit: ESO/Swinburne Astronomy online).

An Artists' Conception of the E-ELT. (Credit: ESO/Swinburne Astronomy online).

 

   The dawn of the mega-scopes is almost upon us… earlier last month, the European Southern Observatory (ESO) consortium announced a site selection for their whopping 42 meter monster; the E-ELT (European Extremely Large Telescope) which will be perched atop Cerro Armazones in central Chile. The 10,020 foot high summit beat out four other possible sites in Chile and the Canary Islands during the long site evaluation process due to its outstanding clarity and seeing. First light is projected to be 2018, and the E-ELT will be composed of a 1,000 hexagonal mirror segments bringing light to focus on a Nasmyth instrument platform.  While designers had to “settle” from designs that included scopes as large as the proposed 100-meter Overwhelmingly Large telescope (!) The E-ELT will still be four times as large as most single aperture scopes in use today. To give you an idea of its scale, the secondary mirror will be larger than the legendary Hale Telescope’s 200-inch primary! Such an engineering project will also pose crucial challenges to designers, as well as kick the “aperture envy” up among astronomers a notch…and like most new instruments, E-ELT will be able to probe the near-infrared as well as the optical. With a billion Euro sticker price, the E-ELT is sure to be one of the engineering feats of our time!

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!

30.05.10: The Faces of Gum 19.

Wide and narrow field views of the Gum 19 region.

Wide and narrow field views of the Gum 19 region.

(Credit: ESO/Sofia/Digitized Sky Survey).

   Take a look at the Nebula pictured above. This is the current visual state of affairs of the nebula known as Gum 19, 22,000 light-years distant in the southern constellation Vela. This rich star forming region is pictured in the Digitized Sky Survey above, and the seemingly non-descript Gum 19 Nebula is perched towards center. Using a an infra-red spectrograph known as Sofia coupled to ESO’s New Technology Telescope, astronomers were able to capture Gum 19 as never before. The nebula itself seems to be canted about 90 degrees to our line of sight, hence its two-faced, dark/light appearance. Gum 19 also houses a monster; a supergiant blue star known as V391 Velorum. This tempestuous star illuminates its nebulous surroundings, and has a surface temperature of 50,000°F. Such a beast is not destined to last for long; blue giants typically go supernova within a 10 million year time span. Will V391 be the next visual supernova in our galaxy to pop? Whatever is the case, enjoy the above ESO provided view while you can!

15.04.10- Do We Know the Future of our Sun?

(Credit: Oliver Beatson).

(Credit: Oliver Beatson).

  You Are Here!

    Our modern understanding of stellar evolution states that our Sun is a middle-aged main sequence star, destined to bellow up into a Red Giant in a few billion years and eventually wind up as a degenerate white dwarf embedded in a shroud of a planetary nebula. Looking out at the stars in various stages of evolution in our galaxy, we see systems that have done just that. These Red Giants often exhibit a rhythmic oscillation as their atmospheres swell and contract, but about one third also display a longer five year variation that scientists do not completely understand. Now, a study conducted by the European Southern Observatories’ Very Large Telescope (VLT) is looking into this mystery by studying 58 sun-like stars towards their elderly Red Giant stage located in the Large Magellanic Cloud. Known since the 1930’s, this mystery has baffled astronomers. “Astronomers are left in the dark, and for once, we do not enjoy it,” stated Christine Nicholls of Australia’s Mount Stromlo Observatory. Some of the long term pulsations could be explained by the presence of an unseen binary companion, but not all. This phenomenon is of special interest to astrophysicists because our own Sun may one day throw similar temper tantrums. Could stellar evolution be in need of tweaking?

19.10.09: 32 New Exoplanets Revealed!

Gliese 667 C, a 6xEarth and one of the "32" (Credit: ESO/Artist's Impression).

Gliese 667 C, a 6xEarth and one of the "new 32" (Credit: ESO/Artist's Impression).

Anybody notice the exoplanet tally on our front page hop up to 402 this morning? That’s because the European Southern Observatory (ESO) revealed a stunning 32 (count em!) new exoplanets identified this morning at their conference at Porto, Portugal. The discoveries were thanks to HARPS, the High Accuracy Radial Velocity Planet Searcher, a sensitive spectrograph attached to the 3.6 meter telescope at La Silla. First installed in 2003, HARPS has thus far discovered 75 of the 400+ worlds now known, or nearly 25%! today’s haul represents the largest single day release. Any special firsts? Well, the grab bag of exo-worlds substantially increases the pool of “super-earths”, as well as three planets found orbiting metal deficient stars, something that may be cause for tweaking planetary formation theory a bit. HARPS is capable of measuring radial shifts as small as 2 miles per hour, an impressive feat. The gauntlet has now been thrown; will the Kepler space telescope rise to the challenge as it stares into Cygnus looking for exo-transits? Do we sense a “exoplanet-war” brewing on mountain tops and chat boards across the world? Stay tuned!

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

An IR, Optical & UV Composite of GRB 090423 as seen from Swift. (Credit: NASA/Swift/Stefan Immler).

An IR, Optical & UV Composite of GRB 090423 as seen from Swift. (Credit: NASA/Swift/Stefan Immler).

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.