SKY REPORTER: Gaia’s Eyes are Opening

Gaia calibration image of the star cluster NGC 1818.
Credit: ESA

The European Space Agency’s recently released image of star cluster NGC 1818 in the Large Magellanic Cloud is part of fine-tuning and testing procedures inaugurating the ambitious Gaia mission sent into space last December. The spacecraft is now being prepared for its five year mission studying the Milky Way and other galaxies. Gaia’s tasks center on providing a three-dimensional map of the Milky Way, thereby refining our knowledge of positions and motions of a billion stars to a degree 200 times more precise than what is currently available.

Gaia continues a notable line of astrometric pioneering that serendipitously revealed aspects of the universe. Early practitioners include Hipparchus of Nicaea who catalogued stars in the second century BC and discovered the subtle cycle of Earth’s axial wobble; Tycho Brahe working in 16^th century Denmark produced the finest pre-telescopic compilation of planet and stellar positions—enabling Kepler’s discovery of the three basic laws of planetary motion; and John Flamsteed who compiled the first telescope based star catalogue, published in 1725.

Gaia’s goals include measuring positions, velocities, distances, brightness, temperature, and composition of one percent of the Galaxy’s stars. Knowledge will be gleaned about the Milky Way’s present state and hopefully reveal telling aspects of its evolution. The mission also has potential for discovering many thousands of extra-solar planets and extra-Galactic objects.

Three sets of Gaia instruments will provide positional and velocity data, photometric information about objects in ultraviolet, visual, and near infrared wavelengths, and facilitate high resolution spectroscopic observations. Systems providing these functions share access to the mission’s two telescopes, and are assigned specific receptor areas on the huge half square meter CCD detector array. Each telescope has a rectangular primary mirror measuring 1.45 by 0.5 meters, about the area of a 63 inch TV screen.

The Gaia mission is now in a complex Lissajous orbit looping around the L2 Sun-Earth Lagrangian point, 930,000 miles above the night side of our planet.

The Moon

Planets

Mercury is low in the evening sky during the first part of February, then after inferior conjunction on the 15th the planet may be seen in the predawn sky. Venus is quite apparent in the southeast before dawn all month and is at maximum brightness on the 15th. The waning crescent moon is near Venus on the mornings of February 25th and 26th. Mars is in Virgo and rises in the later hours of February evenings. The waning gibbous moon is in the vicinity of Mars on the nights of the 18th and 19th. Jupiter retains its prominence and is visible until early morning hours throughout the month. The moon passes near Saturn between February 21st and 22nd. Aside from the moon those nights, Saturn is currently the brightest object in the zodiac between Mars and first magnitude Antares in Scorpius.