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	March/April 1999 Planet Search Continues With New Techniques The announcement in January of the discovery of two more extrasolar planets brings the total to 17 since the first was reported in 1995. All have been detected and confirmed using the radial velocity method, in which astronomers measure the slight shift in the frequency of a star's light caused by the tug of gravity of its planets (see table below). Other detection methods are expected to bear fruit in 1999, including astronmetry, which measures a star's wobble caused by a planet; transit photometry, which looks for predictable variations in a star's brightness caused by a planet passing in front of it, and microlensing, in which a planet perturbs a star's gravitational field. More information about extrasolar planets. Back to March/April 1999 View back issues by year 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 View back issues by issue Browse Back Issues July/August 2008 May/June 2008 March/April 2008 January/February 2008 - Sky Almanac November/December 2007 September/October 2007 July/August 2007 May/June 2007 March/April 2007 January/February 2007 - Sky Almanac November/December 2006 September/October 2006 July/August 2006 May/June 2006 March/April 2006 January/February 2006 - Sky Almanac November/December 2005 September/October 2005 July/August 2005 May/June 2005 March/April 2005 January/February 2005 - Sky Almanac November/December 2004 September/October 2004 July/August 2004 May/June 2004 March/April 2004 January/February 2004 - Sky Almanac November/December 2003 September/October 2003 July/August 2003 May/June 2003 March/April 2003 January/February 2003 - Sky Almanac November/December 2002 September/October 2002 July/August 2002 May/June 2002 March/April 2002 January/February 2002 November/December 2001 September/October 2001 July/August 2001 May/June 2001 March/April 2001 January/February 2001 November/December 2000 September/October 2000 July/August 2000 May/June 2000 March /April 2000 January/February 2000 November/December 1999 September/October 1999 July/August 1999 May/June 1999 March /April 1999 January/February 1999 November/December 1998 September/October 1998 July/August 1998 May/June 1998 March/April 1998 January/February 1998 November/December 1997 September/October 1997 July/August 1997 May/June 1997 March/April 1997 January/February 1997
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