In Our Skies: Asteroid coming closer to Earth

The first-known representatives of the objects we now call asteroids were discovered shortly after the beginning of the 19th century.

At first only a small handful of these objects were known, but during the latter half of that century more and more asteroids began to be discovered. By the final years of the 19th century over 400 asteroids had been discovered, with every one of these small worlds orbiting the sun in what we now call the main asteroid belt between the orbits of Mars and Jupiter.

This all changed on Aug. 13, 1898, with the discovery of a new asteroid by the German astronomer Gustav Witt at the Berlin Observatory and independently that same night by the French astronomer Auguste Charlo is at the Nice Observatory.

The newly-discovered asteroid was found to be traveling in an orbit with a period of 21 months that carried it not only within the orbit of Mars, but also not too far outside Earth’s orbit – becoming, in the process, the first-known near-Earth asteroid, of which several thousand are now known. It has been found to be an elongated object some 21 miles by 7 miles by 7 miles in size – one of the largest of the near-Earth asteroids – and has been given the name Eros, after the Greek god of love.

Eros had passed 14.2 million miles from Earth in January 1894, but of course its existence wasn’t known at that time. It passed 16.2 million miles from Earth in January 1931 and, among other studies, detailed observations of it then helped refine the scale of distances in our solar system – this being before the days of radar- and spacecraft-based measurements which have since superseded these observations.

In January 1975 Eros passed 14.1 million miles from Earth, the closest approach it has made to our planet since its discovery; during this time, it became bright enough to detect with ordinary binoculars. This author, at that time a junior in high school, performed a detailed examination of it as a Science Fair project, and among other things measured its rotation period by studying its variations in brightness, and calculated some of its orbital speeds and physical brightness parameters.

His Science Fair display featured a log, spray-painted black, mounted on top of a birdbath pedestal, all of which were intended to represent Eros’ elongated shape and its rotation.

In this endeavor he was mentored by a local amateur astronomer, Phil Simpson – at that time an officer at the nearby Holloman Air Force Base – who suggested some of the observational studies and who was able to provide access to the local Public-School Observatory. This author was saddened to learn that Phil Simpson passed away just this past September at the age of 83.

This author considers that Science Fair project as the breakout event of his burgeoning career as an astronomer. In addition to winning various awards (including First Place in the Earth and Space Science Division) all the way up to the State level in the Science Fair program, it also introduced him to professional astronomers at New Mexico State University, where he would eventually seek and obtain his Doctoral degree over a decade later.

While life has gone on for this author, Eros has continued its regular orbits around the sun as well. It achieved additional notoriety around the beginning of the 21st Century when NASA’s Near-Earth Asteroid Rendezvous (NEAR) mission – later renamed NEAR Shoemaker in honor of the late planetary geologist Eugene Shoemaker – approached Eros and went into orbit around it, becoming the first spacecraft to orbit an asteroid. After orbiting and studying Eros for the next year, NEAR Shoemaker performed a soft landing onto Eros’ surface on Feb. 12, 2001 and became the first spacecraft to land upon an asteroid.

Eros again came close to Earth in January 2012, when it passed 16.6 million miles from our planet. And now, seven years later, it is doing so again: on this coming Tuesday, January 15, it passes 19.4 million miles from Earth – the fourth-closest approach it will have made to our home world since its discovery.

At this time Eros is located in the southeastern regions of the constellation Perseus, now high in our northeastern sky during the evening hours. Over the coming few weeks it travels towards the south-southeast, passing slightly to the west of the “pentagon” shape of the constellation Auriga, and by the latter part of this month it will be in eastern Taurus, the bull, between the “V”-shaped Hyades star cluster (that marks the bull’s “face”) and the two stars that mark the bull’s horns. For the time being Eros is easily detectable with small backyard telescopes and can be seen with binoculars from dark rural sites.

While, especially in light of the NEAR Shoemaker mission, there is probably not much additional information that can be learned about Eros from Earth-based observations, perhaps there are some students out there who might be interested in recreating this author’s investigations from all those years ago. This author, certainly, has found it interesting to relive those times as he has watched Eros brighten over the past few weeks as it has approached Earth.

It will be a long time before Eros approaches our planet again: that doesn’t happen until January 2056, when it approaches to 13.9 million miles, marginally closer than it was in 1975. This author would be 97 years old at that time; when he pointed this out to his science-minded friends when he was in High School, they jokingly suggested that he could do another Science Fair project then. Well, probably not . . . but perhaps there might be students – even some who would be studying it now – who could study Eros from Eros itself as part of some expedition to that small world. At the very least, let us help create a better world here on Earth that is worthy of such an endeavor.

Alan Hale is a professional astronomer who resides in Cloudcroft. Hale is involved in various space-related research and educational activities throughout New Mexico and elsewhere.