Binocular Comets Update
The comets I’ve been mentioning recently are still observable in binoculars and low power telescopes, easier as the moon wanes 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 that is moving eastward (towards the left) through Aquarius (the Water Bearer). It’s might brighten a bit more before it swings around the Sun next month.
Comet 41P/Tuttle-Giacobini-Kresak is an all-night comet visible 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 the prominent stars that mark the head of Draco (the Dragon), passing close to the star Rastaban overnight on April 18/19. Then it drops towards Venus. Keep an eye on it — this comet has a reputation for sudden outbursts that dramatically brighten it.
Comet C/2015 V2 (Johnson) is also still brightening. It is still fairly stationary, sitting just above Hercules ‘foot, which is above the northeastern horizon in mid-evening, and nearly overheading the wee hours. Being near the pole star, this comet stays up all night.
Brand new Comet C/2017 E4 (Lovejoy) is well within the brightness range of small binoculars or sharp eyes under dark skies, and still brightening. This week, it is in the pre-dawn northeastern sky about a palm’s width to the right of the Andromeda Galaxy, and moving eastward (to the lower left).
Meteor showers occur when the Earth’s annual trip around the Sun carries us through zones of debris that have been left behind by comets and other interplanetary “dump trucks”. Once shed, the sand-sized (and sometimes larger, sometimes smaller) dust particles remain in place. As we pass through a debris field, our gravity pulls the particles downward into our atmosphere where they burn up as “shooting stars”. Large pieces that make it to the ground are called meteorites. The word “meteor” comes from the same root as meteorology, the study of weather, because meteors only occur due to our atmosphere.
The density of the debris train, and its width, dictate the intensity and duration of the shower. A global peak in the number of observed meteors occurs when the Earth is traversing the densest region of debris. For sky watchers, the most meteors will be spotted when the sky overhead is plowing directly into the debris field — as if you’re standing at the prow of a moving ship or seeing bugs splatter on the windshield of your car. For that reason, meteor shower peaks occur just after local midnight, when the sky directly overhead is pointed in the direction of our orbit. The constellation that sits in that patch of sky gives name of the shower but, despite the term “shooting star”, the stars have no connection with meteors.
The annual Lyrid Meteor Shower runs from April 16 to 25, reaches its local peak after midnight through dawn on Friday night into Saturday morning, April 21/22, and is best observed in the Northern Hemisphere. You can start watching from now through next weekend. This shower is produced when the Earth’s orbit takes us through the debris trail left by Comet C/1861 G1 (Thatcher), and it has been occurring for 2,600 years!
In a normal year, the Lyrid shower produces around 20 shooting stars every hour. Unfortunately this year, the Moon is full at the peak and remains above the horizon all night, washing out the fainter meteors. The meteors can appear anywhere, but will appear to originate in a spot near the bright white star Vega in Lyra the Lyre. During evenings, that is low in the northeast, and by dawn is more or less overhead. I’ll post a sky chart of the shower here.
The Moon and Planets
After the recent Full Moon, the moon is now waning and rising after midnight to linger in the morning daytime sky. Last Quarter occurs on Wednesday morning at 6 am EDT. Monday morning, it will sit to the left of Saturn in the predawn southeastern sky. And next Sunday morning, April 23, look for the pretty sight of the crescent moon less than an outstretched fist diameter to the lower right of bright Venus.
Rising before nightfall, bright white Jupiter is now dominating the eastern evening sky. It is just a few finger widths above Virgo’s brightest star Spica. 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.)
Jupiter’s moon Europa casts its shadow on the planet on Sunday, Apr 16 from 10:30 pm to 1 am. Io’s shadow crosses Jupiter on Tuesday, Apr 18 from 9:50 pm midnight, and Ganymede’s shadow passes on Friday, Apr 21 from 10:30 pm to 12:45 am. The Great Red Spot is visible for about three hours centred on Mon, Apr 17 at 1:10 am and again at 9 pm, Wed, Apr 19 at 10:40 pm and Sat, Apr 22 at 12:20 am.
Dim, but very reddish Mars is still sitting partway up the western sky after sunset. It sets about 10:40 pm local time this week. On the evenings surrounding April 20, Mars will pass the Pleiades cluster, which will sit less than four degrees to the upper right of the planet. After the sky darkens, they should be visible together within your binoculars’ field of view.
Yellowish Saturn rises in the southeast before 1 am local time, and can be spotted until about 6 am, when it’s 2.5 fist diameters above the southern horizon. During this summer’s Saturn season, the bright reddish star Antares in Scorpius (the Scorpion) is less than 20° to the right (southwest) of the planet. Rounding out the planets, extremely bright white Venus precedes the sun in the eastern morning sky, rising after 5 am local time. A telescope will reveal that it is showing a thin crescent phase.
Stargazing News for this week (from April 16th) by Chris Vaughan.