Astronomy Week is Here, the Moon is New, and Bright Stars and Jupiter Light the Night!
Astronomy Week is here! Check your local astronomy organizations for star parties and other public events. The week ends with Astronomy Day, Saturday, April 29.
There are lots of bright stars to learn in the sky this time of year. Facing west after sunset, look low in the sky for the bright orange star Aldebaran in Taurus (the Bull). Above Aldebaran, and to the west (right) is yellowish Capella in Auriga (the Charioteer). Lower, and to the east (left), is Orion (the Hunter) with his three-starred belt. Bright reddish Betelgeuse sits above the belt, and blue Rigel mirrors it from below. Both are giant stars, very bright despite being more than 500 light-years away.
About 20 degrees to the east (left) of Orion are Sirius, the entire night sky’s brightest star, and Procyon. These two represent the Big and Little Dog constellations, respectively. Swinging around to the eastern sky, past Jupiter, is yellow-orange Arcturus, the brightest star in Bootes (the Herdsman). Finally, climbing the northeastern later evening sky is Vega, in Lyra (the Harp). This star is the first corner of the Summer Triangle asterism to appear. Northern hemisphere summer is coming!
Binocular Comets Update
The comets I’ve been mentioning recently are still observable in binoculars and low power telescopes, easier with the moonless nights this week. Expect the comets to appear as faint greenish blobs (quite different from a star). If they develop a tail, it will point roughly away from the Sun.
Comet C/2015 ER61 (PANSTARRS) is a pre-dawn comet in the eastern sky that is moving eastward (towards the left) through Aquarius (the Water Bearer). It might brighten a bit more before it swings around the Sun next month.
Comet 41P/Tuttle-Giacobini-Kresak is an all-night comet visible in the eastern evening sky as soon as it’s fully dark, but highest in the sky before dawn. It is still brightening, but nearing its expected peak. This week, the comet is dropping past Hercules’ eastern (left-side) leg, towards the bright star Vega. Keep an eye on it — this comet has a reputation for sudden outbursts that dramatically brighten it.
Comet C/2015 V2 (Johnson) is still fairly stationary, sitting just above Hercules’ western (right-side) foot, which is above the northeastern horizon in mid-evening, and nearly overhead in the wee hours. Being near the pole star, this comet stays up all night.
The Moon and Planets
The moon reaches its New Moon phase on Wednesday morning. With the moon always positioned in the sky near the Sun on the days surrounding new moon, it leaves our night skies dark for meteors and stargazing. In the eastern pre-dawn sky on Monday, April 24, Venus and the old crescent moon will rise together. The moon will be about 9 degrees below the bright planet. Starting on Thursday, you can look for the thin silver crescent of the very young moon, low in the western sky after sunset.
Venus, which is shining brightly in the eastern pre-dawn sky, has been shifting southward as it swings wide of the Sun. Next Sunday, Apr 30 it reaches maximum brightness (visual magnitude -4.53). Yellowish Saturn rises in the southeast just after midnight local time, and can be spotted until about 6 am, when it is about two fist diameters above the southern horizon.
Reddish Mars still resides in the western early evening sky. This week, it’s setting shortly after 10:30 pm local time. Look for the orange-ish bright star Aldebaran about a fist diameter to the upper left of the planet.
Bright white Jupiter still catches the eye in the eastern evening sky this month. It is about a palm’s width above Virgo’s brightest star Spica. At midnight, both objects are about halfway up the southern sky. At dawn, the star and planet are sinking below the western horizon. Jupiter’s four large moons, discovered by Galileo in 1609, occasionally cross in front of the planet, casting little round black shadows beneath them. A moderately sized telescope can see the phenomenon, if you know when to look. The events I list below are visible anywhere in the world where Jupiter is visible in a dark sky. Just correct the Eastern Daylight Times (EDT) to your time zone. (The same goes for the Great Red Spot appearances below.)
Europa shadow crosses on Monday, Apr 24 from 1:06 am to 3:33 am, Io’s shadow on Tuesday, Apr 25 from 11:42 pm to 1:54 am, and Ganymede’s shadow on Saturday, Apr 29 from 2:26 am to 4:47 am. The Great Red Spot is visible for about three hours centred on Mon, Apr 24 at 2 am and again at 9:51 pm, Wed, Apr 26 at 11:30 pm and Sat, Apr 29 at 1 am and 9 pm.
Stargazing News for this week (from April 23rd) by Chris Vaughan.