Their spectra contain moderately strong ultraviolet absorption at wavelengths below about 0.4 μm to 0.5 μm , while at longer wavelengths they are largely featureless but slightly reddish .
Their spectra contain moderately strong ultraviolet absorption at wavelengths below about 0.4 μm to 0.5 μm , while at longer wavelengths they are very featureless but slightly reddish .