Year in Astronomy: 2005
Huygens Arrives on Titan
2005 kicked off with a spectacular feat. After a 7½-year interplanetary journey aboard Cassini, the European Space Agency’s Huygens probe finally reached Saturn’s moon Titan on January 14. Shortly after touchdown, the findings along with 350 or so first images of the large moon’s surface came flooding in to ESA headquarters. Among them: water ice and methane on the moon’s surface, haze in its atmosphere, possible drainage channels, and much more. Planetary scientists will be working this treasure trove of data for years to come.
The first direct image of an extrasolar planet was an elusive goal this year. But thanks to a team led by Gael Chauvin (European Southern Observatory) astronomers have finally captured the photograph. Chauvin's team found the planet candidate in April 2004, but the discovery was not picture perfect; its pitiful mass, just 5 times that of Jupiter, depended on an unproven physical connection with a brown dwarf called 2M 1207. But in May, Chauvin's team released follow-up VLT observations that clinched the case for the two objects being bound. "This confirmation, by common proper motion, that the companion is really orbiting the brown dwarf puts the entire system on firm footing," says independent commentator Geoff Marcy (University of California, Berkeley), who leads the team that has discovered the majority of the 160 or so known exoplanets.
Amateurs Make Exoplanet Discoveries
Among those known exoplanets, amateur astronomers made one of the most important discoveries this year an exoplanet milestone for the amateur community. New Zealand amateurs Grant W. Christie and Jennie McCormick made crucial observations in April that helped several international collaborations of professional astronomers nail down the existence of the planet. The newly discovered planet, just the second one found by gravitational microlensing, is roughly three times the mass of Jupiter and orbits its unnamed host star at approximately three times the average Earth-Sun distance.
Amateur astronomers have previously detected exoplanets transiting their parent stars, but only after professionals made the initial findings. However, later in the year this proved not to be the case. A day before professional astronomers announced a new transiting planet, California amateur astronomer Ron Bissinger detected a partial transit of the same object. HD 149026b is now the third transiting exoplanet detected by amateurs.
NASA Gets New Chief and Returns to Flight
Physicist and aerospace engineer Michael D. Griffin took the helm as NASA's next administrator on April 13th, just one month following his nomination. Griffin succeeded Sean O'Keefe, who resigned from the space agency in mid-February. In his first year on the job Griffin set the tone by participating in a study of the Bush administration's "Vision for Space Exploration." Along with many resolutions, the group recommended phasing out the Space Shuttle sooner than the president's proposed date of 2010, accelerating the development of a new piloted space vehicle, and curtailing spending on the International Space Station (ISS) to help fund future missions to the Moon and Mars.
An overdue servicing mission to the Hubble Space Telescope seems within reach now that the space shuttle has returned to flight. Space Shuttle Discovery launched from NASA's Kennedy Space Center on July 26, ending a 2½ year lull following the tragic Columbia disaster that grounded the fleet in 2003. Discovery returned to Earth August 9th at Edwards Air Force Base in California. A mandated follow-up "return to flight" mission is currently set for launch in May 2006.
Asteroid 2004 MN4: The Near Miss and …
The recently discovered near-Earth asteroid 2004 MN4 made headlines early this year when astronomers estimated that it had a 1-in-38 chance of hitting Earth in 2029. The threat quickly passed when old images narrowed down the asteroid's orbit well enough to guarantee that it would not hit our planet in 2029. Extremely precise radar observations by NASA's Near Earth Object Program calculate that the asteroid will pass 4.7 Earth radii (30,000 kilometers, or 18,600 miles) from Earth's surface on April 13, 2029. With an estimated diameter of 320 meters, 2004 MN4 will appear up to 2 arcseconds wide, making it barely resolvable in amateur telescopes.
To eclipse chasers in the Pacific Ocean on April 8th, a near miss would have been devastating. The year's hybrid solar eclipse was viewed across the land in parts of Central America and the Caribbean where the eclipse was partial. But the total phase of this hybrid solar eclipse was viewed by an estimated 1,500 passengers and crew members aboard three cruise ships since the path of totality never made landfall. Experienced eclipse-chasers aboard the MV Discovery described the eclipse as the most colorful one they'd ever seen. S&T editor in chief and observer Rick Fienberg reported the event vividly: "When totality set in, the Moon's black silhouette was rimmed with a thin and nearly complete ring of magenta fire that was in turn enveloped by a fainter and more expansive white glow the solar corona, or outer atmosphere that extended in opposite directions like a bow tie."
The next total solar eclipse happens on March 29, 2006, for parts of western and northern Africa, the eastern Mediterranean, Turkey, and Central Asia. A partial eclipse will be visible across Europe, the Middle East, most of western Asia, and most of Africa.
A slew of observations made this year have led the way to a better understanding short-lived species of gamma-ray bursts (GRBs). Short GRBs (those lasting less than 2 seconds) flash in every direction of the sky. Until this year, astronomers could only theorize about their cause, since the bursts notoriously expire almost as quickly as they shine. The first breakthrough came as NASA's Swift Observatory recorded a short burst on May 9th lasting just 0.03 second. The space telescope swiveled around and imaged a weak, fast-fading X-ray afterglow the first ever captured from a short GRB source. By targeting the event's location, Swift took a crucial first step toward discovering the mechanism causing these types of events.
Then in mid-year, the long-standing mystery of these bursts' origins cracked open. A short burst flared on July 24th and observations of the afterglow, which lingered for 35 hours, support the leading theoretical model: that a binary system, consisting of either two neutron stars or a black hole and a neutron star, come together in an explosive flash of gamma rays. Furthermore, the observed events each occurred in the outskirts of old elliptical galaxies with minimal star formation evidence that strengthens the merger theory.
While the May 9th and July 24 events provide strong evidence that short GRBs come from mergers, a similar event observed on December 27, 2004, is too fresh in this year's recollection to be ignored. Powerful flares on magnetars neutron stars with stupendously powerful magnetic fields are viable sources of gamma rays in the universe, as the giant flare from the Milky Way magnetar SGR 1806-20 reminded us. This event was the brightest gamma-ray source from outside the solar system ever observed in the history of astronomy, perhaps only the Sun has doused Earth with more total energy than SGR 1806-20's superflare did during the two-tenths of a second that it peaked in intensity. (Thanks to the magnetar's great distance, the superflare posed no threat to humanity or Earth's biosphere.)
Then, on November 3rd, another flare occurred. Lasting just one-tenth of a second, that flare possibly originated from a magnetar in another galaxy. The powerful burst of gamma rays were detected originating from an area in Ursa Major, near M81 and M82, two relatively large galaxies located about 12 million light-years away. If the burst originated in M81 or M82, its total energy and spectrum closely resemble those of the December 2004 giant flare from SGR 1806-20.
Astronomers Discover "10th Planet" and Pluto Bulks Up with Two New Moons
2005 will forever be remembered as the year a new planet was discovered. Or will it? The planet debate will rage on as the year comes to a close, but one thing is for sure: In July Michael E. Brown (Caltech) and his team of astronomers announced the discovery of the largest Kuiper Belt object (KBO) ever and it's bigger than Pluto.
Finally, 2005 was marked as a year of fireworks on July 4th when NASA scientists successfully slammed Deep Impact's 372-kilogram (820-pound) projectile into Comet Tempel 1. The head-on collision took place at more than 37,000 kilometers (23,000 miles) per hour, generating the explosive force of nearly 5 tons of TNT. The impactor's camera relayed a steady stream of detail-rich images until just seconds before its demise.
It's been months since the Deep Impact comet crash, and astronomers are continuing to learn about the physics of the event, the nature of the excavated debris, and the structure of the comet's nucleus. The latest findings of the $333-million mission were discussed last September, when the American Astronomical Society's Division for Planetary Sciences met in Cambridge, England.
Ring in the New Year
As a quick search of our online news archive makes abundantly clear, this annual review only scratches the surface of another amazing year in amateur astronomy and scientific space exploration. That's why S&T's editors and contributors with the help of the worldwide astronomical community work overtime to keep you in touch with the sky and its endless mysteries. In the meantime, we wish you a safe and happy New Year.