The Crestone Eagle • July, 2020

Skies Over Crestone: July 2020

by Kim Malville

 

An artistic depiction of the surface of Titan, with lakes of liquid methane. 

Sagittarius, the Lagoon Nebula, and the Black Hole in the Center of our Galaxy.

The Lagoon Nebula. photo courtesy of Laszlo Francsics

July 4:  One of the paradoxes of living in the northern hemisphere is that we are farthest from the sun on this day of Earth’s aphelion, when the center of the earth is at its farthest distance from the center of the sun, a full 94,507,635 miles.

July 5: The full moon forms a triangle with Jupiter and Saturn.

July 14: Jupiter is at opposition with the sun, rising at sunset, setting at sunrise.

July 20: Saturn reaches opposition with the sun. Both Saturn and Jupiter have their fastest retrograde motion at opposition, when the faster moving Earth passes these planets in our race around the sun.

July 22: Look to the west soon after sunset for a beautifully thin crescent moon lying close to Regulus.

July 28-29: The Delta Aquariid meteor shower. This shower precedes the famous Perseid shower of August by a week and a half. As it fades, the Perseids will begin to appear. This should get you in the mood. Best time for viewing them is in the early morning hours after the moon has set.

July 29: The moon is close to the red supergiant star Antares, which is the bloody heart of the Scorpion.

Constellation of the Month: Sagittarius

Summer evenings are great occasions (if there are not too many mosquitos) for admiring the most brilliant part of our Milky Way in the vicinity of Sagittarius. The Milky Way is truly gorgeous in Crestone, and Sagittarius is its most brilliant part. Sagittarius is named after the Archer, but it makes a much better Teapot. Near the spout of the teapot is the center of our galaxy, some 26,000 light years away wherein lies a supermassive Black Hole containing some 4 million solar masses. It’s a dangerous place with asteroids, planets, and falling stars crossing into it and producing flares of energy: not a good place to raise a family nearby!

In fact, in its vicinity you would need to hold your baby very tight.  In July 2019, astronomers spotted a star traveling outward from the center at 4,000 mph. The star appears to have been propelled out of the center of the galaxy by the Black Hole.  This runaway star appears to have once been part of a double star system that came too close to the black hole. One of the pair was torn away and fell into the event horizon. The other was hurled away, never to return.

This July you might consider lying back with binoculars and sweeping the sky near Sagittarius. In that region of the Milky Way you may find the Lagoon Nebula, one of largest star-forming gas clouds near us. The nebula has obvious dark lanes and looping patterns, a fine sight in almost any telescope and in binoculars. You can’t miss it; the Lagoon is three full moons across. 

The Lagoon Nebula was discovered a 1654 by a little-known Catholic astronomer-priest Giovanni Hodierna living in remote Ragusa, Sicily. Hodierna was a staunch follower of Galileo, believed in the heliocentric solar system, and built a crude telescope similar to that of Galileo.  Because he lived so far from Rome and was unknown to the Inquisition, he escaped the fate of Galileo. Less than 20 years earlier, in 1633, Galileo had been accused of heresy and sentenced to house arrest by the Inquisition for insisting that the earth went around the sun.

Hodierna was interested in discovering comets and recorded as many as 40 nebulae, such as the Lagoon, in order to avoid mistaking them for comets. He died in 1660, “far from the madding crowd’s ignoble strife.”

Saturn’s largest moon, Titan, is truly exceptional. Among our solar system’s more than 150 known moons, Titan is the only one with a substantial atmosphere, and besides Earth is the only object to have rivers, lakes and seas on its surface with liquid methane and ethane. The largest seas are hundreds of feet deep and hundreds of miles wide. Beneath a thick crust of water ice there appears to be a an ocean primarily of water rather than methane. Titan’s subsurface water could be a place to harbor life as we know it. Its surface lakes and seas of liquid hydrocarbons could conceivably harbor life that uses different chemistry than on Earth. Recently we’ve learned that Titan is moving! It was born close to the planet, but during the past 4.5 billion years, it has traveled 746,000 miles to its present orbit. Now it is moving outward at 4.3” every year. Apparently Titan gravitationally squeezes Saturn in such a way that the gas giant oscillates and forces Titan to move away.

Our own moon is also squeezing Earth but moving outward at a slower rate. As we know, the moon causes tides in the oceans here on Earth. Because the Earth rotates faster than the moon revolves around the earth, friction between the oceans and the earth pulls the tides slightly ahead of the moon. The mass of the pile up of water in the tides has the effect of pulling the moon forward in its orbit.  The result is the moon is forced into a higher orbit, amounting to 1.5” per year. As the moon moves outward, it appears smaller. Total eclipses occur because the moon just happens to have an apparent size in the sky similar to that of the sun. But as the moon moves out, total eclipses will become less and less common and will eventually cease to occur. About 600 million years from now, there will be no more total eclipses. So for now, catch the beauty of a total eclipse, while you can!