Andy’s Astronomy: Centaur 5145 Pholus

By Andy Kober

There is much more to our Solar System than our Sun and planets — including Centaur 5145 Pholus.

Public school education provides precious little time to astronomy so most people are unlikely to have ever heard of Centaurs or 5145 Pholus.

Defined as “minor planetoids” and sometimes called ‘planet crossers”, Centaurs are small objects, similar to asteroids, which are found orbiting the Sun and generally located between the planets Jupiter and Neptune.

Some of the Centaurs, including 5145 Pholus, have a stretched or oblong orbit and as a result during part of their orbit they will be closer to the Sun than Saturn, but on the opposite end of their orbit will be further from the Sun than Neptune. It takes Pholus almost 92 years to orbit the Sun.

But that is not what makes it special.

5145 Pholus was the second Centaur discovered and that was by American astronomer David Rabinowitz in 1992. At the time Rabinowitz was with the University of Arizona’s Spacewatch Project.

It is thought that 5145 Pholus originally came out of the Kuiper Belt. It has not passed close to a planet since 764 BC and will not pass close to a planet again until the 5290.

But that is not what makes it special, either.

5145 Pholus is thought to be about 115 miles in diameter, and have minimal surface gravity.

But what makes Pholus special is that it has a reddish color leading astronomers to believe there could be organic compounds on its surface.

That is not to infer there is life on 5145 Pholus, but perhaps carbon-based compounds are present.

Space in the News

American astronauts Suni Williams and Barry Wilmore, stranded on the International Space Station since June, should soon be returning home and might have returned home prior to this column being published.

SpaceX launched a Dragon spacecraft into space last Friday with a crew of four on board. On the return trip, the SpaceX is slated to bring Williams and Wilmore back to Earth along with astronaut Nick Hague and cosmonaut Aleksanr Gorbuno.

Williams and Wilmore were stranded on the ISS due to problems with Boeing’s spacecraft.

Spot the Space Station

There is only one more real opportunity to see the International Space Station during March.

On Friday, Mar. 28, the space station should be visible for about three minutes beginning at 9:30 pm. Look north-northwest about 10 degrees above the horizon and the space station should appear. It will track to the north-northeast reaching a height of about 36 degrees above the horizon.

Going outside and looking at the sky, especially the night sky, can be fun and educational for the entire family.

There are a number of free apps available to help identify stars and constellations.

Happy skywatching!