Continued photometric monitoring of the gravitational lens system 0957+561A,B in the g and r bands with the Apache Point Observatory (APO) 3.5 m telescope during 1996 shows a sharp g band event in the trailing (B) image light curve at the precise time predicted in an earlier paper. The prediction was using gravitational lenses and some other possible implications and uses of the 0957+561A,B light curves.

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Knowledge of the properties of ␥-ray bursts has increased substantially following recent detections of counterparts at X-ray, optical and radio wavelengths. But the nature of the underlying physical mechanism that powers these sources remains unclear. In this context, an important question is the total energy in the burst, for which an accurate estimate of the distance is required. Possible host galaxies have been identified for the first two optical counterparts discovered, and a lower limit obtained for the redshift of one of them, indicating that the bursts lie at cosmological distances. A host galaxy of the third optically detected burst has now been identified and its redshift determined to be z ¼ 3:42. When combined with the measured flux of ␥-rays from the burst, this large redshift implies an energy of 3 ؋ 10 53 erg in the ␥-rays alone, if the emission is isotropic. This is much larger than the energies hitherto considered, and it poses a challenge for theoretical models of the bursts.Ever since their discovery nearly three decades ago 1 , it was understood that progress in solving the puzzle of ␥-ray bursts (GRBs) depends on their identification at other-preferably opticalwavelengths, so that the distances could be measured using standard spectroscopic techniques. From distances and flux measurements one can then infer luminosities and other physical parameters, which can then be used to test theoretical models of the bursts and their origins.A recent breakthrough in this field was the precise localization of bursts by the BeppoSAX satellite 2 , which has led to the first identifications of GRBs at other wavelengths: X-rays 3 , optical 4 and radio 5 . This has further led to the determination of the distance scale of GRBs, with the detection of intergalactic absorption lines 6 in the optical transient 7,8 (OT) of GRB970508 (refs 9, 10). Apparent host galaxies have been detected for the first two optical afterglows found 11-14 .Here we report follow-up studies of the OT 15 of a relatively bright burst, GRB971214 (refs 16-18). As the OT faded away, we found an extended object with a red-band magnitude R ¼ 25:6 Ϯ 0:15 at the position of the OT. Based on the excellent positional coincidence, 0:06 Ϯ 0:06 arcsec, we argue here that this is the host galaxy of GRB971214. Spectroscopic observations show that the host is a typical star-forming galaxy 19-21 at a redshift z ¼ 3:418.Given this high redshift, the ␥-ray energy release of this burst is unexpectedly large, about 3 ϫ 10 53 erg, assuming isotropic emission, corresponding to about 16% of the rest-mass energy of our Sun. Energy released in other forms of radiation, for example, neutrinos or gravity waves, is not included in this energy budget. Nonetheless, the inferred energy release in ␥-rays alone is so substantial that it may present difficulties for some of the currently popular theoretical models for the origin of the bursts (coalescence of neutron stars). We may be forced to consider even more energetic possibilities 22,23 or to find ways of extracting...