22 August 2014

KFOG Broadcast - August 12, 2014

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

14 August 2014

Jupiter & Venus Conjunction – Closest Approach Since 2000

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.

You can find an excellent write up on the conjunction on Sky & Telescope's website. 

10 August 2014

Perseid Meteor Shower 2014 - what to expect

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.

Perseid Meteor
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 resources.

Image courtesy of Stefano De Rosa 

07 August 2014

August 2014 Supermoon

Moon at Apogee and Perigee
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.

There will be an earth-bound effect in the king tides that will result from the Supermoon and other factors. Here's my write-up about the impact on tides and the significant ebb tides we can expect this weekend.

Image courtesy of Wikipedia.