[en] | (164121) 2003 YT1

2003 YT₁ is a member of the Earth-crossing group of Apollo asteroids, the largest group of near-Earth objects with approximately 10 thousand known members.^[1][2]

It orbits the Sun at a distance of 0.8–1.4 AU once every 1 years and 2 months (427 days; semi-major axis of 1.11 AU). Its orbit has an eccentricity of 0.29 and an inclination of 44° with respect to the ecliptic.^[2] The body’s observation arc begins with a precovery taken at the Siding Spring Observatory in November 1989, more than 14 years prior to its official discovery observation at Catalina.^[1]

The asteroid has an Earth minimum orbital intersection distance of 0.0027 AU (404,000 km; 251,000 mi), which corresponds to 1.05 lunar distances and makes it a potentially hazardous asteroid due to its sufficiently large size.^[2] On the Torino Scale, this object was rated level 1 on 27 December 2003 with an observation arc of 8.7 days.^[15] It was removed from the risk table on 29 December 2003.^[16] Over the next ten million years the asteroid has a 6% chance of impacting Earth.^[17]

On 30 April 2004 it made a close approach at a nominal distance of 0.073 AU (28 LD), and on 31 October 2016, it passed Earth at 0.034 AU (13 LD). The asteroid’s closest encounter with Earth will be on 29 April 2073, when it is projected to pass at 0.0113 AU (4.4 LD) only (see table).^[2]

2003 YT₁ has unique orbital characteristics among minor planets. It is the only known binary asteroid to have an Earth MOID within the Moon’s Apogee.^[18]

On 28 April 2017, a 2.7 cm (1 in) fragment of 2013 YT₁ is suspected of having impacted Earth creating a fireball over Kyoto, Japan.^[17] The fragment would have broken off the parent body within the last ten thousand years.

This object has been characterized as a bright Vestian-like V-type asteroid.^[12][14][13]

Several rotational lightcurve of this asteroid have been obtained from photometric observations (U=2/n.a./3/3).^{[8][3][9][10]} Analysis of the best-rated lightcurve gave a short rotation period of 2.343 hours with a brightness amplitude between 0.16 and 0.27 magnitude.^[12]

According to radar observations with the Arecibo Observatory and the survey carried out by the NEOWISE mission of NASA’s Wide-field Infrared Survey Explorer, this asteroid measures between 1.0 and 1.717 kilometers in diameter and its surface has an albedo between 0.198 and 0.4861.^{[3][5][6][7][11]}

The Collaborative Asteroid Lightcurve Link derives an albedo of 0.5848 and adopts a diameter of 1.0 kilometer based on an absolute magnitude of 16.2.^[12]

The Arecibo radar observations in May 2004 revealed that 2003 YT₁ is a synchronous binary asteroid.^[3] Follow-up observations confirmed a 210-meter sized minor-planet moon orbiting its primary every 30 hours at a distance of 2.7 km.^[4][9]

This minor planet was numbered by the Minor Planet Center on 26 September 2007 (M.P.C. 60686).^[20] As of 2018, it has not been named.^[1]

• 2003 YT1, IAUC 8336, 6 May 2004
• List of the Potentially Hazardous Asteroids (PHAs), Minor Planet Center
• Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
• PHA Close Approaches To The Earth, Minor Planet Center
• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• (164121) 2003 YT1 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
• (164121) 2003 YT1 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical properties · Summary
• (164121) 2003 YT1 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters