That bracketed dot in the image is the ESA Herschel Space Observatory. After three years of exporing the Universe in the infrared Herschel depleted its helium coolant in April and was switched off in June after being put into a heliocentric orbit. Herschel was parked ~ 932,000 miles /1.5 million km from us and was moving away in this image.
Herschel has been the subject of an observation campaign, in part for fun (too darned cloudy here to play) and in part to nail down the orbit. Hershel’s new orbit, heliocentric, is around the Sun and it should come back around to us in around 13 years. If we can pin down the orbit perhaps we can find it again when the time comes, otherwise probably not.