Tuesday, August 22, 2006

Faint, Fainter, Faintest

Astronomers are always observing stars or galaxies that are faint, i.e., not very bright. This is usually because by pushing the limit we learn more about the Universe. A team of astronomers led by Harvey Richer from UBC have used the Hubble Space Telescope to observe the faintest stars ever observed, in the globular cluster NGC 6397.

Their research revealed the lowest mass stars on the main sequences in this cluster. These are the smallest stars that will burn hydrogen through fusion and live many billions of years rather than simply fading away after 1 billion years or so.

Richer and colleagues also detected a characteristic change in the color of white dwarfs in the cluster that is related to the onset of molecular hydrogen being formed in the cooling atmospheres as the white dwarfs die. With this information in hand, astronomers can learn more about the physics of low mass stars and white dwarfs and perhaps improve the estimate of the ages of these stars and the universe.

Thursday, August 10, 2006

Planets Without Stars

Astronomers have always thought that objects with the mass of planets orbit stars, or failed stars, know as brown dwarfs. Now a discovery by a team led by a University of Toronto researcher, Ray Jayawardhana, has shown otherwise.

The team's discovery of a seven-Jupiter-mass companion next to a planetary mass object, only twice its mass. Both objects have masses similar to those of extra-solar giant planets, usually found in orbit around a star. Unexpectedly, these bodies appear to circle each other.

The team discovered the companion candidate in an optical image taken with the European Southern Observatory’s 3.5-meter New Technology Telescope on La Silla, Chile, and investigated it further with optical spectra and infrared images obtained with ESO’s 8.2-meter Very Large Telescope on Paranal, Chile. These followup observations confirmed that both objects are young, at the same distance, and much too cool to be stars. The existence of this wide pair poses a challenge to a popular theory which suggests that brown dwarfs and planemos are embryos ejected from multiple proto-star systems.

Wednesday, August 02, 2006

A Tale of Two Telescopes

Those familiar with sky probably know of Castor and Pollux the Gemini Twins. Well, there is another pair of Gemini twins in the Universe and those are the twin 8-meter telescopes operated by the Gemini ObservatoryGemini NorthGemini is unique in having telescopes in both the northern and southern hemispheres giving astronomers access to the complete sky.

The Gemini Observatory runs two of the world's largest telescopes, Gemini North (located on the extinct volcano Mauna Kea, on the Big Island of Hawaii) and Gemini South (located at Cerro Pachon, in the Chilan Andes). These telescopes use the latest technologies to achieve the best performance possible. The Gemini telescopes are optimized for both image quality and performance in the mid-infrared.

Image quality refers to the sharpness of the stars imaged by the telescope. The earth's atmosphere naturally blurs slightly images taken by telescopes. However, astronomers have developed a technique called adaptive optics which mostly corrects for this blurring effect.

Gemini South

Mid-infrared astronomy is very challenging. Think of it as trying to look through an optical telescope at mid-day on a snowy field which reflects all of the sunlight. The problem is that everything on the telescope is emitting at the wavelengths at which you are trying to observe. Gemini has taken great precautions to ensure that as little of the telescope emission finds its way into the camera. The two Gemini telescopes are the best performing telescopes on the planet today.

Don't worry if you are unable to visit either of the Gemini telescopes. There is a Virtual Tour available on CD for the cost of an e-mail.