Travelers In The Night

My Catalina Sky Survey teammate Jess Johnson was very surprised when the large comet with a long stringy tail, which he has just imaged with our 60 inch telescope on Mt. Lemmon, Arizona, was an unknown object. Jess quickly emailed his discovery observations along with a description of the comet's coma and tail to the Minor Planet Center. Over the next eight days astronomers at 11 different observatories around the world tracked Jess's new comet. Scientists at the Minor Planet used these data to calculate it's path around the Sun, verify it to be a comet, and give it the name C/2018 F3 (Johnson). We now know that Comet C/2018 F3 (Johnson) had crossed the orbit of Pluto in 1997 and had reached it's closest point to the Sun 217 days previous to Jess's discovery observations. Further, about two weeks before Jess spotted it , moving through the constellation of Leo, Comet 2018 F3 (Johnson) had streaked unnoticed past the Earth. Unfortunately Jess's comet is likely to be visible only in electronic camera images and in 2037 will once again cross Pluto's average distance from the Sun on a path which will take it into truly deep space. Until a few years ago all of the comets human astronomers had observed originated in the distant regions of our solar system, the Kuiper Belt or the Oort Cloud . Perhaps C/2018 F3 (Johnson) is an interstellar visiting Comet and is thus a sample of a place currently beyond our reach.

Viewed in a telescope an asteroid appears as a moving star like point of light while  a comet often appears to be a fuzzy point of light with a tail.  The orbit of an asteroid is governed force of gravity exerted by the Sun, planets, and in some cases our moon. In addition the Yarkovsky Effect can cause the orbit of a spinning asteroid to shift slightly over millions of years as the heat it absorbs from the Sun radiates back into space. Comets on the other hand can have orbits which change erratically as its nucleus emits small rocket like bursts when frozen gases trapped within it are heated by the Sun.

On Saint Patrick's Day, while searching for Earth approaching asteroids with the Catalina Sky Survey's 60 inch telescope on Mt. Lemmon, Arizona I spotted a slightly enlarged star like object with a tiny tail moving through the constellation of Virgo. After checking to see that it was not a known comet, I sent my discovery observations along with a description of it's coma and tail to the Minor Planet Center. Turns out that it had been observed as a moving point of light, but not noticed to be a comet, by the PanSTARRS group in Hawaii 3 month's earlier. Given the PanSTARRS historical observations along with those from other observatories around the world it only took scientists at the Minor Planet Center 2 days of additional observations to verify it to be a newly discovered comet. Since the naming rules state that a comet should be named after the first observer that identified it to be a comet it was given the C/2018 F1 (Grauer). In December of 2018 and July of 2019 Comet C/2018 F1 (Grauer), which I share with my wife Annie Grauer, will be closest to Earth on it's 5,555 year orbital path about our Sun. Unfortunately it is not likely to be visible to the unaided eye, appearing only as faint moving comet in the night sky on electronic camera images, leaving us to speculate on the condition of humanity when Comet C/2018 F1 (Grauer) returns in the year 7573 AD.

Recently a pair of JPL SynTrack Robotic automated telescopes located at a high altitude low light pollution site in California provided 4 tracking data points taken less than 30 minutes apart which indicated that a small space rock with a diameter smaller  the height of a human being was on a collision course with Earth.

To give you an idea of the asteroid traffic in our neighborhood, on a mostly cloudy night, through holes in the clouds, in a space of less than 2 hours, my Catalina Sky Survey teammate Richard Kowalski posted 7 new close approaching asteroid discoveries on the Minor Planet Center's Near Earth Object Confirmation Page