I paid a visit to the KFOG Morning Show and had a fun chat
with Renee about the Supermoon, Perseid Meteor Shower, How to Look At The Night
Sky, and Star Parties in and around San Francisco. Click here to listen.
After the Moon, the two brightest objects in the night sky
are the planets Venus and Jupiter. Venus is a close neighbor and a very
reflective planet, dominating morning and evening skies with its brilliant
white shimmer against the changing colors of the dawn or dusk sky. Jupiter is
the giant planet of the Solar System and despite its distance, is a bold and
bright object for us to enjoy, especially in a telescope or binoculars.
Venus & Jupiter Conjunction
These two planets, like all of the objects in the Solar
System, gradually change their position with respect to the background stars
from day to day. All of the objects in the Solar System move along a common
path across the sky, the Ecliptic. And from time to time these objects line up
and create beautiful patterns and visually stunning sights.
On the morning of Monday August 18th (from North
America), we will see Venus and Jupiter in a conjunction, a close alignment of
the two bodies from our Earthbound point of view. The two will be in the east
just before sunrise, so you’ll have to get up early to see this, but it will be
rewarding. The two will be less than the Moon’s width apart, and given their
bright nature, the pairing should be spectacular. Through binoculars, you will
also be able to see a lovely star cluster, the Beehive Cluster, in the
background of stars, as Jupiter and Venus will be in the constellation Cancer
and passing through the Beehive.
The image (courtesy of Sky & Telescope) shows where to
look. From San Francisco, sunrise will be at 6:30 am and the Venus-Jupiter pair
will rise at 5:00 am, so you will need a good northeastern horizon to see the
pairing, and the 30 minute window starting at 5:00 will provide the best dark-sky
viewing conditions as the glare of dawn will start to interfere by 5:30.
This year’s Perseid Meteor Shower will peak on August
11-12-13 and should offer up a moderately pleasing view of meteors but will be
impacted by the nearly Full Moon. Meteors come in all sizes and shapes and
during a reliable shower like the Perseids, you can see them all. However,
moonlight increases the ambient lighting of the entire night sky and
consequently makes the faint meteors all but invisible. The medium-strength
meteors and the fireballs will shine through the glare of course, so the
Perseids will have a showing, but just not at the rate we often see during a
truly dark sky shower.
I’ve often written that meteor showers are best viewed after
midnight, when we are turned toward the path of Earth’s orbit (we are on the
“front-face of Earth” after midnight), and we get better meteors. This still
holds true, but in a recent article in Sky & Telescope, author Alan
MacRobert suggests that early evening is a very good time to look for earth-grazers,
meteors that enter the Earth’s atmosphere as a low angle and can be seen for
much longer periods of time.I will
certainly be looking for these. I’m not an all-night observer and prefer
looking out into the sky waiting for meteors when I am a bit more awake. So the
idea of seeing grazers carries appeal for me in more ways than one. Last week on Mt. Tam we witnessed some spectacular meteors, one of which had a trajectory that suggested it was an early Perseid grazer.
For more information on the Perseids, check out these
We are in the midst of a three-month period of Supermoons, a confluence of orbital nodes that brings us the Full Moon phase at the same time as Perigee, the closest approach of the Moon to the Earth. The next one is on August 10. The difference in the Moon's distance from the Earth from Perigee to Apogee is quite substantial, varying from 222,000 miles out to 253,000 miles, leading to the a 14% difference in the apparent size of the Moon. In addition, the Moon will be at the peak of the ascending node of its orbit, placing it somewhat higher in the sky than is typical for summer Full Moons.
In 2005 I began writing a column for the San Francisco Waldorf School newsletter called "The Urban Astronomer." I started this blog in 2007 as a place to archive my articles and to offer additional insights on the night sky - even if you live in a big city. In 2008 I became an occasional guest on the KFOG Morning Show, and more recently on KALW and KGO. Archived shows are posted on the blog.