‘Great Conjunction’: Earthlings treated to rare alignment of Jupiter and Saturn

By Peter Szekely

NEW YORK (Reuters) -The evening sky over the Northern Hemisphere treated stargazers to a once-in-a-lifetime illusion on Monday as the solar system’s two biggest planets appeared to meet in a celestial alignment that astronomers call the “Great Conjunction.”

The rare spectacle resulted from a near convergence of the orbits of Jupiter and Saturn that happened to coincide with Monday’s winter solstice, the shortest day of the year. For those able to observe the alignment in clear skies, the two frozen-gas spheres appeared closer and more vibrant – almost as a single point of light – than at any time in 800 years.

Jupiter – the brighter and larger of the pair – has been gradually nearing Saturn in the sky for weeks as the two planets proceed around the sun, each in its own lane of an enormous celestial racetrack, said Henry Throop, an astronomer at National Aeronautics and Space Administration headquarters in Washington.

“From our vantage point, we’ll be able to be to see Jupiter on the inside lane, approaching Saturn all month and finally overtaking it on Dec. 21,” Throop said in a statement last week.

At the point of convergence, Jupiter and Saturn appeared to be just one-tenth of a degree apart, roughly equivalent to the thickness of a dime held at arm’s length. In reality, of course, the planets remained hundreds of millions of miles apart, according to NASA.

A conjunction of the two planets takes place about once every 20 years. But the last time Jupiter and Saturn came as close together in the sky as on Monday was in 1623, an alignment that occurred during daylight and was thus not visible from most places on Earth.

The last visible great conjunction occurred long before telescopes were invented, in 1226, halfway through construction of the Notre Dame cathedral in Paris.

The heightened brightness of the two planets as they almost merge in the sky has invited the inevitable speculation about whether they formed the “Christmas star” that the New Testament describes as having guided the three wise men to the baby Jesus.

But astronomer Billy Teets, acting director of Vanderbilt University’s Dyer Observatory in Brentwood, Tennessee, said a Great Conjunction is only one of several possible explanations for the biblical phenomenon.

“I think that there is a lot of debate as to what that might have been,” Teets told WKRN-TV in Nashville in a recent interview.

Astronomers suggested that the best way to view Monday’s conjunction was by looking toward the southwest in an open area about an hour after sunset.

“Big telescopes don’t help that much, modest binoculars are perfect, and even the eyeball is okay for seeing that they are right together,” Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, wrote in an email to Reuters.

The next Great Conjunction between the two planets — though not nearly as close together — comes in November 2040. A closer alignment similar to Monday’s will be in March 2080, McDowell said, with the following close conjunction 337 years later in August 2417.

(Reporting by Peter Szekely in New York; Additional reporting by Joey Roulette in Washington; Editing by Lisa Shumaker and Sonya Hepinstall)

On Saturn’s moon Titan, plentiful lakeside views, but with liquid methane

Ligeia Mare, the second largest known body of liquid on Saturn's moon Titan, shown in data obtained by NASA's Cassini spacecraft, is pictured in this NASA handout image released January 17, 2018. NASA/Handout via REUTERS

By Will Dunham

WASHINGTON (Reuters) – Scientists on Monday provided the most comprehensive look to date at one of the solar system’s most exotic features: prime lakeside property in the northern polar region of Saturn’s moon Titan – if you like lakes made of stuff like liquid methane.

Using data obtained by NASA’s Cassini spacecraft before that mission ended in 2017 with a deliberate plunge into Saturn, the scientists found that some of frigid Titan’s lakes of liquid hydrocarbons in this region are surprisingly deep while others may be shallow and seasonal.

Titan and Earth are the solar system’s two places with standing bodies of liquid on the surface. Titan boasts lakes, rivers and seas of hydrocarbons: compounds of hydrogen and carbon like those that are the main components of petroleum and natural gas.

The researchers described landforms akin to mesas towering above the nearby landscape, topped with liquid lakes more than 300 feet (100 meters) deep comprised mainly of methane. The scientists suspect the lakes formed when surrounding bedrock chemically dissolved and collapsed, a process that occurs with a certain type of lake on Earth.

The scientists also described “phantom lakes” that during wintertime appeared to be wide but shallow ponds – perhaps only a few inches (cm) deep – but evaporated or drained into the surface by springtime, a process taking seven years on Titan.

The findings represented further evidence about Titan’s hydrological cycle, with liquid hydrocarbons raining down from clouds, flowing across its surface and evaporating back into the sky. This is comparable to Earth’s water cycle.

Because of Titan’s complex chemistry and distinctive environments, scientists suspect it potentially could harbor life, in particular in its subsurface ocean of water, but possibly in the surface bodies of liquid hydrocarbons.

“Titan is a very fascinating object in the solar system, and every time we look carefully at the data we find out something new,” California Institute of Technology planetary scientist Marco Mastrogiuseppe said.

Titan, with a diameter of 3,200 miles (5,150 km), is the solar system’s second largest moon, behind only Jupiter’s Ganymede. It is bigger than the planet Mercury.

“Titan is the most Earth-like body in the solar system. It has lakes, canyons, rivers, dune fields of organic sand particles about the same size as silica sand grains on Earth,” Johns Hopkins University Applied Physics Laboratory planetary scientist Shannon MacKenzie said.

The research was published in the journal Nature Astronomy.

(Reporting by Will Dunham; Editing by Sonya Hepinstall)

Five planets visible in pre-dawn sky for first time in 11 years

Early-morning stargazers will have the rare opportunity to observe five planets at the same time during the next few weeks, according to a recent post on astronomy website EarthSky.org.

EarthSky says it’s the first time in more than 11 years that the five brightest planets — Mercury, Venus, Mars, Jupiter and Saturn — will simultaneously appear in the sky above Earth.

People had their first chance to catch the five planets before sunrise this morning, according to EarthSky, and the rare sight can be witnessed just before dawn every day through February 20.

The planets can be seen without a telescope or binoculars from anywhere on Earth, the EarthSky post says. Unclear skies could prevent some people from observing the spectacle on certain days.