by Geoff Chester, USNO Public Affairs | 06 February 2024 Jupiter, with Europa, Io, & Callisto, imaged 2024 February 6 at 00:30 UT imaged at the U.S. Naval Observatory with the 30.5-cm (12-inch) Clark/Saegmüller refractor The Moon returns to the evening sky by the end of the week, with New Moon occurring on the 9th at 5:59 pm Eastern Standard Time. For an observing challenge, try to find the hairline crescent Moon about half an hour after sunset on the evening of the 10th. Luna will be just five degrees above the southwest horizon at that time, so you will need an open view toward that direction. Use a pair of binoculars to locate The Moon’s slender arc. Just above the lunar crescent is Saturn, which should be easy to see in binoculars. Luna will be easy to spot on the following night, and she ends the week closing in on the bright glow of Jupiter. The February Globe at Night program continues through the evening of the 10th. As we mentioned last week, the target constellation is Orion, who strides across the meridian between 8:30 and 9:00 pm. If there is one star pattern that can be said to be “universally” recognized, Orion is the one. He is visible from every inhabited part of the globe, and his three “belt stars”, which form an almost perfect straight line, are often one of the first asterisms that casual skywatchers learn. You can record your observation of Orion and his surroundings on the Globe at Night web app and add your contribution to science! As Orion heads toward the west, he is followed by his trusty hunting dogs, Canis Major and Canis Minor. Each of these constellations is marked by a bright star on the eastern side of the Great Winter Circle. Sirius leads Canis Major, who seems to jump at Orion’s heel, while Procyon stands about 25 degrees above the brighter star. Sirius and Procyon are bright due to their proximity to the solar system. Sirius is a mere 8.5 light years distant, while Procyon lies about 11.4 light years away. Both stars have white dwarf companion stars that were first discovered by their gravitational action on their brighter companions. The existence of Sirius B was inferred by careful measurements made by the German astronomer Friedrich Bessel in 1844, and was discovered in 1862 by the American telescope maker Alvan Graham Clark while testing the 18.5-inch lens for a telescope destined for the Dearborn Observatory in Chicago. Procyon B was also predicted by Bessel, but it wasn’t observed until 1896, when it was spotted with the 36-inch refractor at Lick Observatory. These faint companions are the remnants of stars that have exhausted all of their nuclear fuel. They have masses similar to that of the Sun, compressed by gravity into spheres smaller than the Earth. Gravity crushes the nuclei of atoms together, stripping away the electrons that repel atoms in normal matter. A teaspoon of white dwarf material would outweigh our biggest aircraft carrier! The constellation of Canis Major is one of the few star patterns that resemble a stick figure of its namesake. From a dark sky the constellation is dominated by the bright glow of Sirius, but there are several second-magnitude stars that trace out the Dog’s outline. This area of the sky is full of star clusters that resolve nicely in binoculars or a small telescope. Look a few degrees below Sirius for the clump of stars that betray Messier 41. About 8 degrees east of the asterism that marks the Dog’s hindquarters you will find another rich star cluster, Messier 93. If it’s clear on the evening of the 10th, use the slim crescent Moon and a pair of binoculars to get your last look at Saturn until the summer is upon us. The ringed planet passes behind the Sun on the 28th. Jupiter is best placed for viewing during the evening hours. He is still the best planet for viewing in the small telescope, but try to give him a look before 9:00 pm. Later in the evening we are looking through more of our atmosphere, which will degrade the view of fine details in the giant planet’s atmosphere. Venus still greets early risers from a position in the southeastern sky, but her glow is only visible as twilight gathers. Venus will linger in twilight for the next few month, but spotting her will become more difficult as she gradually creeps up on the Sun.