Lunar eclipses and solar eclipses usually go together (though two weeks apart). A nearly total lunar eclipse occurred on the night of Nov. 18/19 followed Saturday by a total solar eclipse, which there wasn’t much coverage about since the path of totality was over the Southern Ocean and a small section of Antarctica.
The new moon was just two hours from perigee — the closest orbit point to Earth — so the moon was moving fastest sideways in the sky. Earth is also getting close to perihelion — the closest orbit point to the sun — so the sun appears slightly larger in our sky than at other times of the year. Put both of those things together and yesterday’s total solar eclipse was at best slightly less than two minutes long.
The next total solar eclipse will be the April 2024 eclipse going through the middle of the U.S. and northern Mexico and a small piece of Canada. All of the orbital elements will work together to make that eclipse last up to nearly five minutes long. The longest total solar eclipse this decade will be the one in August 2027 visible in Spain, northern Africa, Saudi Arabia and Yemen. That will be just over six minutes long. Although short, they are truly awesome events that have to be experienced in person; video broadcasts don’t do them justice.
Keeping watch on asteroids
The day before Thanksgiving saw the launch of the Double Asteroid Redirection Test (DART) mission that will crash into the small asteroid moon of a larger asteroid sometime between Sept. 26 and Oct. 1 next year. The moonlet, called Dimorphos, is just 530 feet (160 meters) across and it orbits the asteroid Didymos, which is 2,560 feet (780 meters) in diameter.
Neither asteroid is ever going to hit Earth, and the impact of DART into Dimorphos is not going to change that fact. However, the change of Dimorphos’ orbit around Didymos will be much easier to measure than if we tried the redirection of a single asteroid’s orbit around the sun.
Riding along with the main spacecraft is LICIACube, a CubeSat built by the Italian Space Agency that will separate from the DART shortly before impact to record what happens. Several observatories on Earth will also be watching from a safe distance of 6.8 million miles (11 million kilometers) away. Four years later, the European Space Agency will send the Hera mission to examine the two asteroids up close.
All sorts of computer simulations have been done to predict what will happen when DART rams Dimorphos, but we need to test the computer models with an actual experiment. DART is the first Planetary Defense test mission and it’s a simple test: How well can we nudge an asteroid?
There are no known asteroids larger than 140 meters in size that will hit Earth in the next 100 years but we have probably found only about half of the estimated 25,000 near-Earth objects (NEOs) that are 140 meters and larger so far. An asteroid 140 meters in diameter hitting Earth would produce only regional effects while something 300 meters across would affect a continent or two and a 1-kilometer object would have a global effect (mass extinctions everywhere).
The Vera Rubin Observatory, which will go online next year, was expected to find a bunch more NEOs but the deployment of the constellations of tens of thousands of communication satellites such as SpaceX’s Starlink, OneWeb and Amazon’s Project Kuiper will make that search impossible. Even if we can get the satellite constellations below naked eye visibility, each satellite will still be millions of times brighter than a dark asteroid on its way to Earth.
In the night sky
We’ve been enjoying the brilliant Venus in our evening sky in the west. On Saturday, it was at maximum brilliance. Venus has “rounded the corner” on its orbit as seen from Earth, so it’ll now be drawing closer to the sun in our sky as it begins to move in between us and the sun.
Tonight, Venus will set almost three hours after sunset, but by the end of the month it will set just one hour after sunset. In a telescope, you’ll see Venus become a very thin crescent shape. If you know right where to look low in the southwest, you might be able to see an extremely thin waxing crescent moon but Monday will bring an even prettier sight of a slightly fatter waxing crescent moon just below the brilliant starlike Venus.
To the left of Venus will be the giant planets Saturn and Jupiter. Jupiter will be the brighter one of the two on the left. Saturn is near the right side of Capricornus and Jupiter is now midway between Capricornus and Aquarius. The crescent moon will pass under Saturn on Dec. 7 and Jupiter on Dec. 8. The moon will be at first-quarter phase on Dec. 10.
On Dec. 18, the moon will be full and this one will be a “micromoon” — full phase near the apogee or farthest point in its orbit around Earth. Since this full moon is the one nearest the winter solstice, the full moon take its farthest north path across the night sky, staying above the horizon for a long time.
Orion becomes visible in the east shortly before 7 p.m. and it’ll be highest in the sky due south at about 12:20 a.m. The two brightest stars in the dog constellations, Canis Major and Canis Minor, are Sirius and Procyon, respectively. Those stars are first visible at about 8:45 p.m.
Contributing columnist Nick Strobel is director of the William M. Thomas Planetarium at Bakersfield College and author of the award-winning website AstronomyNotes.com.
