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The redshift range from 2.2 to 3, is known as the 'redshift desert' ofquasars because quasars with redshift in this range have similar optical colorsas normal stars and are thus difficult to be found in optical sky surveys. Aquasar candidate, SDSS J085543.40-001517.7, which was selected by a recentlyproposed criterion involving near-IR $Y-K$ and optical $g-z$ colors, wasidentified spectroscopically as a new quasar with redshift of 2.427 by theLAMOST commissioning observation in December 2009 and confirmed by theobservation made with the NAOC/Xinglong 2.16m telescope in March 2010. Thisquasar was not targeted in the SDSS spectroscopic survey because it locates inthe stellar locus of the optical color-color diagrams, while it is clearlyseparated from stars in the $Y-K$ vs. $g-z$ diagram. Comparing with other SDSSquasars we found this new quasar with $i$ magnitude of 16.44 is apparently thebrightest one in the redshift range from 2.3 to 2.7. From the spectralproperties we derived its central black hole mass as $(1.4\sim3.9) \times10^{10} M_\odot$ and the bolometric luminosity as $3.7\times 10^{48}$ \ergs,which indicates that this new quasar is intrinsically very bright and belongsto the most luminous quasars in the universe. Our identification supports thatquasars in the redshift desert can be found by the quasar selection criterioninvolving the near-IR colors. More missing quasars are expected to be recoveredby the future LAMOST spectroscopic surveys, which is important to the study ofthe cosmological evolution of quasars at redshift higher than 2.2.

A very bright i=16.44 quasar in the `redshift desert' discovered by LAMOST