Do the periods of comets decrease because they lose mass every time they get near the Sun? Robert BaileyConover, Wisconsin Great question! Assuming you're referring specifically to the orbital period - in other words,

In the photo from the space station, the comet is captured just above Earth’s horizon, which is illuminated by a bright light — also known as airglow — that occurs in the planet’s upper atmosphere when atoms and molecules emit light after being excited by sunlight.

I pick out North America’s celestial highlights for the week ahead (which also apply to mid-northern latitudes in the northern hemisphere).

Astronomer Dean Regas gives us the lowdown on the best things to look out for this winter, from a “planet parade” to the ATLAS comet.

Plus: Saturn’s moon Iapetus is visible, our Moon passes the bright star Spica, and Mars skims south of Pollux in Gemini in the sky this week.

On Monday night you may have a chance to witness the moon obscuring the Red Planet at its brightest, as well as a comet’s closest approach to the sun.

A new study, currently under review for publication, suggests that an ancient cosmic visitor might have significantly altered the orbits of our solar system's giant planets. Scientists propose that this interstellar object,

thought the star of Bethlehem was also a comet. Jerusalem’s sky on November 12th, 7 BC, with Jupiter and Saturn in conjunction. Even though the records of Chinese astronomers appeared to corroborate this idea, there is still a major flaw: the comet ...

On Tuesday evening, six planets will line up in the night's sky - Mars, Jupiter, Neptune, Saturn, Uranus and Venus. Best viewed in skies free of cloud, the planets should be easily spotted amongst the stars.

Venus, Mars, Jupiter and Saturn are visible to the naked eye this month and for part of February. Uranus and Neptune can be spotted with binoculars and telescopes.

The night sky is putting on a celestial show with a dazzling "planetary parade" featuring six major planets and a bonus comet.