Category: Astronomy

Exploring the cosmos

First Potentially Habitable Earth-Sized Planet Confirmed by Keck and Gemini Observatories

The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory. The initial discovery, made by the Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes.

Kepler-186f
The artist’s concept depicts Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone. Credit NASA AMES/SETI Institute/JPL-CalTech
“What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form,” says Elisa Quintana of the SETI Institute and NASA Ames Research Center who led the paper published in the current issue of the journal Science. The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.

Steve Howell, Kepler’s Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot an exoplanet of this size and proximity to its host star. “However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option.”

With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected. To do this, the team obtained extremely high spatial resolution observations from the eight-meter Gemini North telescope on Mauna Kea in Hawai`i using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-meter Keck II telescope, Gemini’s neighbor on Mauna Kea. Together, these data allowed the team to rule out sources close enough to the star’s line-of-sight to confound the Kepler evidence, and conclude that Kepler’s detected signal has to be from a small planet transiting its host star.

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Vesta at Opposition

Today the minor planet 4 Vesta will pass through opposition.

4 Vesta is one of the largest objects orbiting between Mars and Jupiter, a region often referred to as the Asteroid Belt. This is the second largest asteroid, at 530km (329miles) in diameter. It is also usually the brightest asteroid that can seen by earthbound observers. When Vesta is at opposition it is bright enough to be just visible to the unaided eye, usually around 6th magnitude.

This year Vesta will reach magnitude 5.7 at opposition. This magnitude requires a dark site to view without the aid of a telescope. Precise knowledge of the location is also helpful. Given these two items it becomes possible to see an asteroid with the unaided eye.

The minor planet is currently located in Virgo about 2.5° northwest of τVir. Interestingly enough the dwarf planet 1 Ceres will be located about 2° east and a touch south of Vesta. Despite being much larger than Vesta it will be over a full magnitude dimmer at about 6.9 magnitude.

Vesta was visited by the Dawn spacecraft during 2011 and 2012. Dawn is now on course for Ceres with a planned rendevouz in February 2015.

Vesta 28May2007
Vesta (marked), Jupiter and Summer Milky Way, 40s, 17mm@f/4, fixed tripod on 28May2007

Venus and Neptune

Over the next few days Venus will swing quite close to Neptune. Today the pair is separated by 2°41′. This will decrease to 49′ on the 11th and remain close at 51′ on the 12th.

The pair is quite a mismatch… Neptune is a mere 7.9 magnitude while Venus is a brilliant -4.2, over 60,000 times brighter. The 4.8 magnitude star σAqr will be 1.5° southwest of the two, the only nearby object that can be confused for the planet.

Next month, on May 15th, Venus will pass about 1° from to Uranus for a similar oddball conjunction.