A proactive approach to apocalyptic scenarios: Join us for a distinguished lecture Jan. 16 on finding near-earth objects — before they find us

Of all the natural disasters that could befall us, only an Earth impact by a large comet or asteroid has the potential to end civilization in a single blow. Yet these near-Earth objects also offer tantalizing clues to our solar system’s origins, and someday could even serve as stepping-stones for space exploration.

Dr. Donald Yeomans is coming to HMNS to explain the science of near-Earth objects — its history, applications, and the ongoing quest to find near-Earth objects before they find us.

Distinguished Lecture Jan. 16: Near Earth Objects: Finding Them Before They Find UsIn its course around the sun, the Earth passes through a veritable shooting gallery of millions of nearby comets and asteroids. One such asteroid is thought to have plunged into our planet 65 million years ago, triggering a global catastrophe that killed off the dinosaurs.

Yeomans provides an up-to-date and accessible guide for understanding the threats posed by near-Earth objects, and also explains how early collisions with them delivered the ingredients that made life on Earth possible. He shows how later impacts spurred evolution, allowing only the most adaptable species to thrive — in fact, we humans may owe our very existence to objects that struck our planet.

Yeomans will take us behind the scenes of today’s efforts to find, track, and study near-Earth objects. He will show how the same comets and asteroids most likely to collide with us could also be mined for precious natural resources like water and oxygen, and used as watering holes and fueling stations for expeditions to Mars and the outermost reaches of our solar system.

What: Distinguished Lecture, “Near Earth Objects: Finding Them Before They Find Us”
Who: Donald Yeomans, NASA Jet Propulsion Laboratory, California Institute of Technology
When: Wednesday, Jan. 16, 6:30 p.m.
Where: HMNS Main, 5555 Hermann Park Dr. 77030
How Much: $18 for the public; $12 for members

Dr. Donald Yeomans is a Senior Research Fellow with the Near-Earth Object Program Office at NASA Jet Propulsion Laboratory at California Institute of Technology. Following the lecture, he will sign copies of his new book Near Earth Objects: Finding Them Before They Find Us.

Click here for advance tickets.

This month, see a ‘Hairy Star!’

An unexpected visitor graces our skies this month.  Comet Lulin is now visible through binoculars in late evening and morning skies.  It makes its closest approach to Earth on February 24, when it may even be dimly visible to the naked eye!

Comet Hale-Bopp
Creative Commons License photo credit: tlindenbaum

Comets are made of ice and dust and are often called ‘dirty snowballs.’ They are believed to be left over from the formation of the solar system.  As comets approach the sun, ice changes into gas and the dust embedded within the ice is released.  A cloud of particles expands out to form a coma around the comet’s solid nucleus. This coma may be a hundred thousand miles across. Radiation pressure of sunlight and the powerful solar wind sweep gases and dust off of the comet, forming tails pointing away from the Sun. The coma and tails of a comet reminded the ancient Greeks of hair; the Greek word ‘kometes’ means ‘hairy.’   

Astronomers traditionally name comets after their discoverers.  On July 11, 2007, Lin Chen-Sheng of Lulin Observatory in Nantou, Taiwan took some photographs of the sky.  The photos were part of the Lulin Sky Survey, in which astronomers search the sky for Near-Earth Objects which might pose a risk of colliding with Earth.  One of his students, Ye Quanzhi, spotted what he thought was an asteroid in three of the pictures.  Closer observation, however, revealed the coma of a comet.  Officially designated C/2007 N3, the comet was named Lulin after the observatory where it was discovered. 

Here are some interesting facts about Comet Lulin’s orbit:

The eccentricityof an orbit describes its shape.  Bound orbits are ellipses with eccentricities between 0 and 1; 0 is a perfect circle while 1 is a parabola.  Lulin has an eccentricity of 0.9999948, almost 1.  This indicates an orbit so oblong that Lulin won’t return to the inner solar system for about 50 million years.  Some sources indicate an eccentricity slightly greater than 1.  In that case, Lulin will never again approach the Sun.

Lulin was closest to the Sun (at perihelion) on January 10.  But it approached the Sun from the far side (from our perspective).  Thus, as Lulin recedes from the Sun, it approaches Earth, with closest approach on February 24.  Not to worry, though–even at its closest, Lulin will be about 150 times as far away as the Moon.

Many comets’ orbits are highly inclined to ours.  (An inclination of 0 degrees would describe an orbit in the same plane as Earth’s orbit.)  Comet Lulin has an inclination of 178.37 degrees.   This inclination of almost 180 degrees puts Lulin back in the plane of the solar system, orbiting backwards compared to the planets’ orbits. 

Since Lulin orbits almost in Earth’s orbital plane, we see not only a tail but an ‘anti-tail.’  This is dust and debris left behind as the comet moves on its path.  Lulin is now moving away from the Sun, so the dust it leaves behind seems to point towards the Sun. The true tail of a comet always points away from the Sun (and therefore, the tail leads the comet as it moves away from the Sun). 

The Hale-Bopp Comet
Creative Commons License photo credit: Wolfiewolf

Because Lulin is roughly in the plane of the solar system, traveling backwards, it appears against the same zodiac band where we find the Sun, Moon, and planets in our sky.  As I type this, Lulin is among the stars of Virgo, the Virgin, moving towards Leo, the Lion. 

As we pass more or less between the Sun and Lulin next week, we’ll see it in Leo, first near Saturn and then near the bright star Regulus.  Lulin will be rising in the east at about dusk, highest in the sky about midnight, and setting in the west just before dawn.  Since Lulin and Earth are going in opposite directions, we see Lulin move quite noticeably night to night. 

This page has some finder charts for Lulin.  Some observers have reported seeing Lulin naked-eye, at the threshold of visibility.  You must get far from city lights, therefore, to see it without binoculars or a telescope.  Remember to scan the sky for a diffuse object about half as big across as the full Moon (and much dimmer than that), not a point of light.  Those who saw the spectacular comets Hyakutake and Hale-Bopp in the ’90s should keep in mind that Lulin will be barely (if at all) be visible to the unaided eye and will not come close to their displays.  If you find Lulin, see if you can follow it as it gets dimmer but higher in the evening sky in March. 

Once it fades away, we’ll never see it again.