NASA's New Planet-Hunting Telescope Catches a Comet and Other Celestial Sights

NASA's new planet-hunting telescope wasn't even formally on the job when it caught sight of a fascinating set of celestial happenings, which the agency has shared in a new video.

The telescope, formally called the Transiting Exoplanet Survey Satellite but nicknamed TESS, will spend two years scanning the sky for exoplanets orbiting close to small, faint stars by looking for dips in a star's brightness.

That's not what the telescope saw here, but the new video showcases some of the same traits the instrument will need to succeed at its primary mission, a NASA statement explains. The video includes images taken across 17 hours, and shows TESS' ability to produce stable views that can be stacked on top of each other to study a set swath of the sky. [NASA's New Planet Hunter Begins Its Search for Alien Worlds]

But instead of using that ability to observe changes in star brightness, in the video TESS focused on a handful of other phenomena that astronomers call transients because of their temporary appearance in the sky.

The comet C/2018 N1 is seen by NASA's Transiting Exoplanet Survey Satellite (TESS) in this view captured by the spacecraft on July 25, 2018. The comet was discovered June 25 by NASA's Near-Earth Objects Wide-field Infrared Survey Explorer.
(Image: © Massachusetts Institute of Technology/NASA’s Goddard Space Flight Center)

The most obvious of the transients is a comet called C/2018 N1, which appears as a bright blob crossing TESS' field of view from right to left. The instrument captured enough detail about the object to watch its tail change directions in response to the flow of the solar wind coming from the sun. The comet was discovered less than a month before TESS spotted it, according to NASA, and is currently about 29 million miles (48 million kilometers) away from Earth.

The field of view also includes two variable stars, NASA explained in the video, which brighten and dim at a regular pace. (That's not the same dimming as is caused by the planets TESS is meant to find blocking the star; it's a dimming within the star itself caused by stellar mechanics alone.)

Perhaps the strangest phenomenon on view in the images is a faint beam of light reflected off Mars, which is out of the frame. Because Mars was just two days before its opposition when the images were taken — meaning it was almost directly opposite the sun from Earth — it was particularly bright; therefore, TESS was able to catch a glimpse of the Red Planet's reflection.

Finally, the video shows a host of asteroids sprinting on their own journeys across the sky. They're tricky to spot at slower speeds earlier in the video but stand out clearly in the fast boomerang view that NASA shares later in the video.

The images were taken shortly before TESS began its primary scientific observations on July 25.

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