06 November 2019

Transit of Mercury on November 11, 2019 - don't miss it !

On Monday November 11 we will have a chance to witness a very unique and special event, a transit of the planet Mercury across the face of our Sun. This is a rare event, happening only 13 times in a century. The next one won't take place until 2032.

What is a transit? It is a precise alignment of the Sun, Earth and another celestial body. In this case, that body is Mercury, the closest planet to the Sun and a fairly small planet. It orbits the Sun every 88 days, and when we have this special alignment with a transit, we are witnessing the proper motion of the planet as it progresses in its orbit around the Sun. Mercury's diameter is 194 times smaller than the Sun so it will in fact appear as a tiny, perfectly round black dot against the surface of the Sun (the Photosphere) and will take approximately 5 1/2 hours to cross from solar limb to solar limb.
Time Lapse of Mercury Transit in 2016

If you want to see this, you will need special equipment that incorporates the correct level of filtering to reduce the Sun's intensity to a safe level, and magnification to make it possible to see the shape of Mercury against the disk of the Sun. Many astronomy clubs and public observatories will host viewing events. Here in Munich, the Volkssternwarte M√ľnchen will be open for the entire duration that the transit is visible from here, starting at 1:35 pm and continuing through sunset which is at 4:39 pm on Monday. We just need clear skies and a proper filter and we can enjoy this unique and rare event.

For general information about the transit and more detailed timing for US-based locations, check out this article from Space.com.

Warning: do not stare directly at the Sun for any length of time, and in particular do not look at the Sun through a telescope or binoculars with "eclipse glasses" as these will not protect your eyes sufficiently. Only observe the Sun directly with a high quality solar filter built especially for a telescope or binoculars.

Image courtesy of NASA.

14 October 2019

Cygnus and the Milky Way

Autumn brings us cooler evenings and earlier sunsets, but it’s not yet too uncomfortable to go outside and gaze up into the heavens for a look at our own galaxy, the Milky Way. The best way to enjoy this from a city setting is to get out to a place where you can lie flat on your back (on a blanket or lounge chair) and look directly overhead. In the evening the constellation Cygnus dominates the sky and is easy to find even with light pollution around you. Cygnus is also known as the Swan, as it resembles a giant swan flying gently toward the north-east and is also known as the Northern Cross, since its brightest stars outline a cross quite clearly. The brightest star of Cygnus is Deneb, a beautiful blue giant star that is one member of the Summer Triangle, an asterism that is made up of three of the brightest stars in the summer and fall skies. The diagram below shows the region of the sky directly overhead (zenith) with the three bright Summer Triangle stars identified in white, and the cross shape of Cygnus in purple.

Cygnus the Swan, or Northern Cross
Cygnus is directly in the band of stars of the Milky Way that we can see across the night sky. In dark conditions, the band of the Milky Way glows like a faint cloud but in the city that is unfortunately lost to light pollution. However, if you have binoculars or a telescope you can still enjoy the richness of the Milky Way by looking deeply into Cygnus where you will find many treasures that are quite accessible. I’ll cover some of those in a future post. For now, just see if you can get out and gaze up into Cygnus and into the elliptical arms of our own home galaxy. There are little gems and surprises awaiting you!

Image courtesy of Sky Safari.

02 October 2019

Time to restart - October 2019

It's been two years since I posted on this blog. It's time to restart. Since I started this blog I moved from San Francisco, California to Munich, Germany. Here the skies are slightly different and the weather is not nearly as reliable so I am observing less frequently. However, I still want to write occasional articles that describe the astronomical highlights in the night sky, in particular those accessible to city dwellers. More to follow ....