Perseid Meteor Shower 2013

It's August, and that means it's time for one of the best meteor showers of the year, the Perseids. This shower occurs every year around August 11-12-13, bringing with it the promise of 50-100 meteors per hour under ideal viewing conditions. There are a lot of great resources on the web to learn about it (see below). For San Francisco and Bay Area residents, here are my thoughts on how to best enjoy it.

In the City: San Francisco and the Bay Area have a bit too much light pollution to see all of the meteors clearly, but you will certainly see some within city limits. The most important things are (a) to have a broad horizon with a view of as much of the sky as possible, and (b) to situate yourself in as dark of a spot as you can find, ideally shaded from streetlights or houselights. Let your eyes adapt and look overhead; you could see 5-10 per hour.

Outside the City: The best way to enjoy a meteor shower is outside of city limits, where darkness prevails and you have a broad view of the sky. As with any stargazing endeavor, you want to dress warmly and bring along creature comforts such as a sleeping bag, lawn chair, and a warm drink. Give yourself plenty of time to dark-adapt. And do this with friends -- it's much more fun when you share this with others.

Where to look: Directly overhead. They appear to originate from a spot in the eastern sky in the constellation Perseus, but they will be visible over all of the night sky.

When to look: meteor showers are always best viewed after midnight, when the rate of meteors goes up considerably. The peak nights for the 2013 Perseids are Sunday night (11th-12th) and Monday night (12th-13th), although Saturday night August 10th will be a fine night as well, as the meteors start to approach their peak and the weekend is in full swing.

In you live in the Bay Area, join the San Francisco Amateur Astronomers high atop Mt. Tamalpais for a full evening of astronomy and meteor watching on Saturday 10th. We'll have a lecture, star gazing through telescopes, and meteor viewing until 1:00 am. Admission is free. More details here: http://www.sfaa-astronomy.org/

Here are two excellent web resources on the Perseids:

http://www.skyandtelescope.com/observing/home/Get_Ready-for-the-2013_Perseids-218037521.html

http://earthsky.org/astronomy-essentials/earthskys-meteor-shower-guide

Enjoy the show!

A Graceful Moon

A Graceful Moon

This week we enjoy the start of the lunar cycle, from New Moon on the 6th through the waxing crescent phases. The Moon travels higher and more southerly each evening, as it starts its monthly orbit around the Earth, gracefully slipping along the ecliptic and closely brushing up against planets and bright stars. The view on Thursday 9th should be particularly engaging, as bright Venus stands in contrast to the brighter (but more diffuse) thin crescent Moon. You will need a good western horizon to enjoy this, where the pair will shimmer in the dusk sky. Later in the week the Moon will slide past bright star Spica and Saturn, and happily will set well before midnight, so as not to interfere with the Perseids meteor shower. More on the Perseids in my next blog post. For now, Clear Skies and Happy Viewing!

Clear Skies!

Amateur astronomers often sign off an email or message with the phrase "Clear Skies" because anyone interested in enjoying the night sky needs to have a clear sky to start with. I often close blog posts on this blog with the phrase "Clear Skies!" as a kind of wishful thinking and good luck charm.

Right now in San Francisco, I need all the good luck I can get. The coastal weather pattern each summer ensures that clear skies will be rare indeed, especially in the Outer Richmond district where I live. So I have had precious few viewing opportunities from my own backyard this summer, and the San Francisco Amateur Astronomers have been forced to cancel most of their "City Star Parties" that take place near Lands End on the western side of the city, due to fog.

Venus and the sunset sky

When we get the rare clear sky, or when I am in another part of the Bay Area and am enjoying a stunning view of the western horizon just after sunset, I am reminded why I love astronomy; the beautiful changing color of the sunset sky, and the gradual transition into night, and the dazzling light of Venus in the west, all combine to motivate me to look up in the sky, and more than ever, I appreciate the clear skies that usually are available here in the Bay Area.

So to all of you, I wish you "Clear Skies" and a warm night somewhere this summer to enjoy the heavens.

Image courtesy Pete Lawrence.

The Five Visible Planets

As an amateur astronomer and public speaker, I find the five visible planets fascinating. These 'wanderers

The Solar System

' are beautiful to watch with the naked eye, and are interesting in a telescope as well, even in a big city. Consequently, I am a close watcher of the changing motions and of these bodies, and I point them out often to groups at star parties. The planets all follow the band of the Zodiac across the sky, of course, because they move along the ecliptic, the projection of the orbits of all of the Solar System planets across the sky. And as such, their motion is interesting to watch, whether they are the inner planets of Venus and Mercury with their unusual twilight appearances, or the outer planets of Mars and Jupiter and Saturn, enjoying long seasons in the limelight of the night sky. 

We just had some interesting patterns of planets and stars, and of course can always enjoy those by knowing where to look for the five visible planets. Earth Sky has a fine article on these planets for July.

Solstice and Super Moon: Transitions

We have two special moments this week in the heavens, moments that attract public attention because they are transition points in the cycles of nature. As Earth orbits the Sun, and the Moon orbits the Earth, we are aware of changes in the relationship between these bodies, and the special alignments that come and go. This week, we experience the Summer Solstice in the northern hemisphere, and also a Super Moon, a full moon that coincides with the closest approach of the Moon to Earth.

Solstice is a special moment, driven by the Earth's tilt with respect to its orbit around the Sun. The 23 degree tilt of Earth's axis brings about considerable change in the length of time the Sun is above the horizon, and obviously that affects weather, and affects how people live, in particular in northern latitudes. Solstice marks the seasonal shift from lengthening days to shortening days. June 21st marks the moment this year when that happens.

Super Moons are a popular thing now, and this too marks a special moment, a transition in the Moon's orbit around the Earth when the Moon reaches the closest point on its elliptical path, and appears larger in the sky. Along with the somewhat larger size in the sky comes an increased impact on tides, and groups such as the California King Tides Initiative have worked to raise awareness of global warming by measuring the impact of high tides on coastal communities. This month's Super Moon occurs on the night of Saturday June 22nd to the morning of Sunday June 23nd, when the Moon reaches perigee (closest approach to Earth) within a few minutes of the moment of Full Moon.

The heavens are full of moving objects, from the planets in the Solar System, to asteroids and comets, and even galaxies and stars. All of this motion creates patterns and alignments that are beautiful to behold. And the transitions between key alignments make for interesting moments to ponder our place in the universe.

Hercules

The Stars of Hercules

The early summer skies feature a fascinating constellation that climbs high into the night sky and provides several interesting features to see with the naked eye, binoculars or a telescope. Hercules is the Roman mythological hero that is adapted from the Greek hero Heracles. In the night sky, he is kneeling in the sky with a club overhead, engaged in battle with other mythological enemies throughout the heavens. Similar to Orion the Hunter, Hercules has a distinctive shape; in stark contrast to Orion, Hercules has no bright stars - no first magnitude stars, and only one that is barely second magnitude, and hence Hercules takes some effort to find. But it's worth the effort.

Hercules is visible due east after sunset in June, and is directly overhead by midnight. The middle four stars form a distinctive shape, well known to astronomers as the Keystone. This trapezoidal shape is the center of the figure of Hercules, and it contains a beautiful deep space object known as Messier 13, the Great Globular Cluster in Hercules. It is a spectacular sight to behold in binoculars or a telescope; M13 is a rich cluster that shimmers from the 300,000 stars located in it.

The stars of Hercules are not particularly bright, but they are quite interesting. One of the brightest stars is called Rasalgethi, and it is a a binary star system with a red giant star and a companion that orbit each other every 3,600 years. The brightest star is called Kornephoros, a yellow giant star 148 light years from Earth.

Exploring the heavens is more fun when you know what to look for. Spend a few minutes on Hercules with a telescope or binoculars, and you'll see plenty of interesting objects, even from within a big city.

Image courtesy of SkySafari.

Transitions in the Evening Twilight

Every night, the sky appears a bit different to us, and in June as the long days of summer unfold, the sunset sky changes more rapidly than usual. The trio of planets that dominated dusk are now a pair, as Mercury and Venus climb higher into the west, and the bright stars and constellations of winter rapidly fade from view.

June's evening sky

The bright twin stars Castor and Pollux in the constellation Gemini are dropping gradually into the western sky after sunset, and the later and later onset of darkness combine with the change in position to speed these two stars out of view over the coming days. As they are lower and lower each night, Venus and Mercury will move higher each night and over the next 3 weeks, they will move closer to each other.

As you watch the changing landscape in June, take note of the gradual slowing in the onset of darkness as we approach the summer solstice later this month. The evening sky is a beautiful place to see transitions, and the visiting planets this month provide a fine guideline for this.

The Dance of the Planets - a spectacular celestial alignment

This week is the culmination of a spectacular celestial alignment, creating a rare and beautiful triangle of three planets on Sunday 26th. The planets will be low in the west after sunset, and as the glare of the sunset fades, the three bright dots of light will emerge from that glare, and if you have a good western view, you'll see them for a short window of time before they set.

The Triangle of Planets

Jupiter has been dominating the night sky for months, but each successive night has brought it closer to the time when it slips 'behind' the Sun, from our vantage point, and is shielded from our view. This happens to all of the outer planets throughout the course of a year or two. But by cosmic coincidence, Mercury and Venus are rapidly rising into the sunset sky, as their orbits bring them out of the glare from being 'behind' the Sun, and they quickly pop up into the evening sky. This week, they appear to move higher and higher in the sky just as Jupiter is 'falling' and they cross over in a lovely pattern.

To see this spectacle, head out any evening and look west. The configuration will be changing noticeably each night, and for me, that is the real fun here -- to not only see a rare and unusual alignment on Sunday, but to watch the set up in the days before and after. Here are a number of good links with additional information:

Sky & Telescope Magazine
The Always-Engaging Tony Flanders on SkyWeek
NASA Science Cast

Enjoy the show, and may you have clear skies!

Image courtesy of Sky & Telescope