Friends of the Planetarium Newsletter April 2008

Friends of the Planetarium Newsletter April 2008


Mars and Saturn currently grace our evening skies. Both are easy to find, as they lie close to bright stars in their respective Zodiac constellations. Mars is getting lower each night but can still be spotted just above Castor and Pollux, the heads of the twins of Gemini. In mythology, Pollux and his twin brother Castor were members of the Argonauts’ crew. They became the patron saints of mariners and appeared in ships’ rigging as the electrical phenomena known as Saint Elmo’s Fire. Look for the three bright objects forming a rough triangle low in the northwest once the sky has darkened. Mars will show a slightly red colour compared to the other two, which are distant stars. Mars starts the month of May in Gemini but will be in Cancer by the evening of May 6. Its path takes Mars towards Praesepe, the Beehive star cluster, which it crosses between May 22 and 24. It will be just north of the centre of the cluster on the evening of May 23. This should present a splendid binocular view and a photographic opportunity. By the end of June Mars will have traveled all the way to Leo and be very close to the bright star Regulus (more about Regulus later). Our knowledge of Mars grows daily with the two rovers Spirit and Opportunity still working after four years on the surface. In orbit, several spacecraft are in operation with a new arrival expected in late May. NASA engineers have adjusted the flight path of the Phoenix Mars Lander, setting the spacecraft on course for its May 25 landing on the Red Planet. The landing area is an ellipse about 100 kilometers by 20 kilometers. Researchers have mapped more than five million rocks in and around that ellipse, each big enough to end the mission if hit by the spacecraft during landing. Knowing where to avoid the rockier areas, the team has selected a scientifically exciting target that also offers the best chances for the spacecraft to set itself down safely onto the Martian surface. Phoenix will dig to an ice-rich layer expected to lay within arm's reach of the surface. It will analyze the water and soil for evidence about climate cycles and investigate whether the environment there has been favorable for microbial life.

This artist's concept depicts the Phoenix Lander a moment before its touchdown on the arctic plains of Mars. Pulsed rocket engines control the spacecraft's speed during the final seconds of descent. Image credit: NASA/JPL-Caltech/University of Arizona

Meanwhile, in orbit, NASA's Mars Reconnaissance Orbiter used its High Resolution Imaging Science Experiment (HiRISE) camera to take two images of the larger of Mars' two moons, Phobos, within 10 minutes of each other on March 23. This is the first, taken from a distance of about 6,800 kilometers. The illuminated part of Phobos seen in the images is about 21 kilometers across. The most prominent feature in the images is the large crater Stickney in the lower right. With a diameter of 9 kilometers, it is the largest feature on Phobos.

Getting back to the night sky, look farther around to the east to find Saturn lurking near Regulus, the brightest star in Leo the Lion at magnitude 1.4. For most of the month only 2 degrees will separate them, with Saturn to the right of Regulus. Saturn is a full magnitude brighter than Regulus, which is understandable, given the distance to Regulus is 85 light years. Regulus has almost always been associated with royalty and kingly power. In Arabia it was known as Malikiyy, the “Kingly One”. Copernicus has been credited with giving the star its current name, a diminutive of Rex, or king. It may also relate to the four so-called “Royal Stars” (with Aldebaran, Antares and Fomalhaut), all situated about ninety degrees apart in the sky. By May 31, Saturn will be setting at about 11.30 pm and will be its highest and best placed for viewing at the end of evening twilight. The half lit Moon will join this lovely pairing of Saturn and Regulus on the evening of May 12, presenting another photo opportunity. Speaking of photo opportunities and Saturn, the Cassini spacecraft continues to send back truly amazing images of Saturn, its rings, and its ever more numerous and fascinating moons. A selection of the best images from Saturn, its rings and moons are appearing in an exhibition which opens this week at the American Museum of Natural History in New York City. The show, called "Saturn: Images from the Cassini-Huygens Mission," will run through March 29, 2009. It features dramatic, up-close-and-personal images in small individual views and super-large mosaics. Roughly 50 images taken by the Cassini-Huygens mission in visible light, infrared and radar have been handpicked by a team of Cassini scientists.

Montage of images of Saturn and some of its moons, taken by the Cassini spacecraft. Image credit: NASA/ESA/JPL/Space Science Institute/Univ. of Arizona

Visit the Cassini website to see these images in full colour.

As the winter months approach, the familiar stars of Scorpius are beautifully displayed along the eastern horizon. The scorpion likeness is most clearly seen when the stars are well risen but still low in the sky. By 10:00 p.m. the next zodiac constellation, Sagittarius, has emerged from the eastern horizon, followed closely by Jupiter, which is currently located in the handle of the “Teapot”. Jupiter will provide excellent viewing opportunities throughout the winter months. Even a pair of binoculars mounted on a camera tripod or held very steadily will show four of Jupiter’s moons. This orbital ballet changes by the hour as the faster moving moons pass in front of or behind Jupiter. A small telescope will begin to show some of the different cloud bands in the turbulent atmosphere of this enormous gas giant planet. Get out there and have a look.

We had a few enquiries from the November 2007 Newsletter regarding Gary Sparks’ visit to Peru and whether or not some type of presentation was going to be made. Gary is doing two talks about his archaeoastronomy trip in the coming weeks. On April 29, he will be speaking at the Planetarium for the Royal Society. The talk begins at 7:30 p.m. and seats must be booked in advance. Entry is by gold coin donation. Contact Lynne Trafford at 06 8356336 or by email at . The second talk is for the Lions Club of Napier Host and might be for members only. This one is on June 18. Contact a member of the Lions for details.

Finally, it is the time of year when we ask you to renew your subscription to Friends of the Planetarium. A subscription renewal form is included with this newsletter. We appreciate the support that you have given us and hope that it will continue. Please tell your friends about Friends and about the Planetarium. It is open to the public on Sunday evenings from 7:00 p.m. to 9:00 p.m. No bookings are required.