Quadrantids Meteor Shower - January 3-4, 2011

2011 starts with an impressive meteor shower for those ready to brave a cold night. The Quadrantids take place the night of Monday January 3rd into the morning of Tuesday January 4th, and are made better by the fact that the Moon is new, meaning no interference from moonlight.

As always, the best viewing of any meteor shower is from a dark location, ideally away from city lights. But I have had some success right in my backyard in San Francisco by positioning myself away from direct lights such as streetlights and houselights, and allowing myself 5 to 10 minutes to adapt to the darkness. Once dark adapted, the winter sky shimmers and Quadrantids are readily visible. In dark skies outside of cities you can expect up to 2 meteors per minute, but in the City I am happy to see 1 meteor every few minutes. This year should be as good a show as any, and despite our rainy Northern California weather the outlook is good.

To see this shower, position yourself facing northeast but give yourself as much of a view of the sky as possible. A lawn chair is best (along with blankets and a hat), as the meteors appear to originate in the constellation Bootes in the northeast part of the sky, but the meteors radiate in every direction away from this point.

For some fun background and history of this meteor shower, check out Astronomy.com and NASA's "What's Up" blog series. Image is courtesy of NASA.

Stay warm, and here's to good skies!

Shimmering Early Morning Sky

As we approach the latest sunrise of the year (January 4th at 7:25 am in San Francisco), the morning sky remains dark enough to see stars until well after 6:00 am. That means that the early riser is rewarded with some lovely sights to close out 2010 and welcome 2011. Brilliant Venus dominates the sky each morning, shining bright in the South-East well before dawn. This week the waning Moon presents a changing landscape as it moves past Saturn, the bright star Spica (see diagram on the right), and then later in the week Venus and Mercury. Following the Solstice-Total-Lunar-Eclipse, the Moon is tracking downward on the Ecliptic, meaning that each Morning it is following the planets from high in the sky on a steep angle toward the horizon.

If you are not an early riser, don't despair. I'll have a post about the Winter skies soon. All you have to do is look up (especially if you are up at midnight on New Year's Eve and have clear skies). The Winter is a fantastic time to enjoy the stars.

Image courtesy of Sky and Telescope Magazine.

Total Lunar Eclipse of December 20, 2010

Monday night December 20th, we get to witness a very exciting astronomical spectacle, a Total Lunar Eclipse. This one promises to be a special one, capping the longest night of the year with the strange and beautiful view of the full Moon being blotted out by the shadow of the Earth. The geometry of an eclipse is fairly textbook, but the experience is quite dramatic.

This eclipse will be visible from the western hemisphere, meaning that anyone on the entire night side of Earth will have a view of the full Moon and will see the phases of the eclipse. In this particular eclipse, the Moon passes through the darkest part of the Earth's shadow (umbra) meaning that the entire surface of the Moon will no longer have direct sunlight shining on it, but because of the atmosphere of the Earth, refracted rays of sunlight will in fact bend around the Earth and illuminate the Moon, creating a trademark orange or reddish color on the Moon, an eerie effect indeed. The excellent NASA Eclipse Website has much more detailed information on the eclipse.

The event starts at 10:33 pm in San Francisco, as the partial phases of the eclipse take about an hour. The period of "totality" when the entire surface of the Moon is dark, lasts about an hour from 11:41 pm until 12:53 am, and then the Moon is slowly revealed again for another hour. Cross your fingers for good weather, dress warmly, and enjoy this fascinating spectacle of nature. And if you have binoculars or a telescope, use them - this is exactly the time to get a close-up look at one of the wonders of the sky.

Image courtesy of the Universe Today.

Geminid Meteor Shower 2010

One of the best Meteor Showers of the year takes place in favorable conditions on Monday night December 13th into the morning hours of December 14th. The shower is called the Geminids, named after the constellation Gemini. The Geminids appear to originate from the constellation Gemini which rises shortly after sunset and is high in the sky around midnight. This point in the sky is called the radiant, and if you trace the paths of the meteors backwards, they will all converge in this point.

Meteor showers generally get better late into the night because the Earth is rotated in the direction of its orbit around the Sun and consequently we encounter a higher number of meteors, on average. This is certainly true for the Geminids, and in dark conditions after midnight you might see 1 or even 2 meteors a minute. Being winter, you have to really prepare for this by dressing extremely well for your local conditions. I plan to get up early and look for Geminids in the early morning hours of Tuesday 14th, since the Sun does not impact the viewing until after 6:00 am.

This year is particularly favorable for the Geminids because the Moon is at First Quarter and will not be a factor after midnight. Stay warm and enjoy the show!

Image courtesy of Earth Sky.

KFOG Podcast - December 3, 2010

Today on the KFOG Morning Show Podcast with Irish Greg, we talked about the discovery of new stars in the galaxy, alien life forms right here on Earth, the upcoming Geminids Meteor Shower on December 13-14, the upcoming Total Lunar Eclipse on December 20-21, and Holiday Shopping including a special 10% discount on anything at Scope City in San Francisco (my favorite place to shop) if you mention KFOG or The Urban Astronomer. Click here to listen. And take advantage of the 10% offer while it lasts!

Brilliant Venus and Old Moon in the Dawn Sky

With sunrise at 7:00 in the morning, I find this time of year to be one in which I can do some early morning stargazing without having to change my morning routine. This week the waning Moon provides a lovely scene against the backdrop of brilliant Venus, bright Saturn and the bright star Spica. The illustration demonstrates what to expect in the eastern skies as the Moon shrinks each day on its way to the New Moon on December 5^th. If you are a morning person with an interest in astronomy, this will be an excellent week for you. Get out your binoculars for an especially riveting view of these heavenly bodies, and take in a few minutes of beauty about an hour before the sunrise.

Review of iPhone Astronomy Apps: ISS Visibility and Iridium Flares

Two of my favorite iPhone apps are ISS Visibility and Iridium Flares, apps that help you to locate satellites very precisely. I use these two apps extensively, anytime I have clear skies and want to enjoy the spectacle of dazzling satellites crossing the sky, even here in the bright city lights of San Francisco. Continuing from my previous post on iPhone apps, here are two more reviews.

ISS Visibility does exactly what it promises by telling you when and where to look to see the International Space Station. Transits of the ISS across the evening or morning sky are impressive, whether the viewing is of the space station crossing a broad arc across the sky, or a short appearance that ends in the impressive flickering and fade of the ISS as it crosses the Earth's shadowline from daylight to night. At a price of $1.99, ISS Visibility gives you simple-to-use charts based on your location, and shows you where to look along with a nice 2D map showing the location of the ISS over Earth as it passes your viewing site.

Iridium Flares are bright lights in the sky that shine when Iridium Satellites in orbit around Earth reflect sunlight back toward the planet and produce a particularly bright glint of light in the sky for a few seconds. I find iridium flares wonderful to watch because at their best they flare up to -7 or -8 magnitude, many times brighter than Venus or Jupiter at their brightest. Also, being able to predict these special events is quite a lot of fun. I love to show off iridium flares to friends when the conditions permit. The Iridium Flares iPhone App costs a mere $0.99 but will pay back many times over.

Enjoy these two apps to see things in the sky that will certainly impress you.

Leonid Meteor Shower 2010

A very fine meteor shower arrives this week. The Leonids peak on the night of November 17 and morning of November 18th, bringing a fairly reliable collection of meteors to the eastern skies. Best viewing is well after midnight into the early morning hours (around 4:00 AM until sunrise), when the Moon will have set and the Earth is better positioned to intersect more meteors.

Star Date Online has a nice article and image about the Leonids, so named because they appear to originate in the zodiac constellation of Leo. The constellation rises in the early morning sky and dominates the eastern sky. As the Sun does not break the darkness of the morning sky until 5:30 AM, the best darkness will be from 4:00 until 5:30 at which an observer in dark skies can see dozens of meteors per hour. Another good online resources is Astronomy.com with a good article on the Leonid shower.

Image from Astronomy.com.

KFOG Podcast - October 26, 2010

Today's Urban Astronomer talk with Irish Greg of the KFOG Morning Show features the North Star, Meteor Showers in November and December, some early shopping tips for the holidays, cool iPhone Apps, Jupiter and more. It's always a treat to talk with KFOG and share some astronomy tips with the listeners. Click here to listen.

Waning Moon, Morning Darkness

Each month the Moon makes a 29 1/2 day journey around the Earth, bringing different faces of the Moon to light, making beautiful patterns with the surrounding stars and planets, and shining light into the evening, midnight or morning skies. Right now, the Moon is waning, getting smaller each night as it passes through gibbous phases while moving from Full Moon to Last Quarter, lining up with bright celestial objects such as the Pleiades and Taurus. During the gibbous phases, the orientation of the Moon is quite different from what we normally expect in the evening skies.

The illustration shows the changing orientation of the Moon just after sunset in the waxing phases, as the Moon grows from New to Full. This view is for Northern Hemisphere viewers. But after the Full Moon, the orientation reverses and is best measured in the sunrise sky. So the view you can see right now is of a Moon curved not toward the east as normally seen in the evening sky, but rather curved toward the west in the morning sky. It's refreshing to see this time of year while it is so dark in the morning, and it provides a chance to see things in a different light. Eye-opening.

Image courtesy of University of Virginia.

An Elusive Comet in Urban Skies: Hunting for Hartley 2

Comets can be bold and brash, streaking across the sky like Hale-Bopp in 1997 (see image on right), a comet that was visible even in light-polluted urban areas. Comets can be more humble but then unexpectedly brighten, as did Comet Holmes in 2007. This year marks the return of periodic Comet Hartley 2, a small but frequent visitor to the inner Solar System that is making a fairly close pass to the Earth (11 million miles) on October 20th. Because of the bright Moon on October 20th, this and last week mark the best chances to see the comet because the Moon is young and not brightening the sky. So I took a look last week and again this week to see if I could spot this elusive comet from a city location (last week in a suburb of Frankfurt, Germany and this week from my home in San Francisco).

I hunted quite a while on both occasions, using this very helpful map from Sky and Telescope Magazine. In fact, S&T has been running updates as viewers report seeing Comet Hartley 2 with binoculars. However, it seems that to see Comet Hartley 2 you need a location with very dark skies. I can attest to this, having twice tried and failed to discern the comet from the surrounding stars.

However, all is not lost. Searching for Hartley 2 requires you to find Cassiopeia, Perseus and Auriga, three very nice constellations that grace the Fall and Winter skies. While searching the path of the comet, you encounter a range of deep space objects near and between Cassiopeia and Perseus, and tonight the view was quite good. So even though city lights may have drowned out the faint comet, I enjoyed my first good look at the Double Cluster in Perseus and other celestial gems in the spiral arm of the Milky Way that is beyond Cassiopeia.

I recommend a good jacket, a comfortable chair or blanket, a few minutes patience, the S&T sky map, and binoculars. No matter whether your hunt for Comet Hartley 2 is a success or not, you will be glad you made the effort.

Autumnal Equinox and the rate of change of the length of the day

Today is the Autumnal Equinox, one of two Equinoxes of the year. These are days that mark the transition from one season to the next, but also are days that have very special significance as the Earth orbits the Sun. Because of the tilt of the Earth's rotational axis, the Northern and Southern Hemispheres receive radically different amounts of sunlight from June through December, as the seasons progress from Summer to Fall to Winter (northern hemisphere). This is well understood and we learn from basic science courses that the in-between points while transitioning from Summer to Winter, for example, are the days that have equal periods of the Sun above the horizon and below the horizon -- equal duration of night and day -- hence Equinox. Today, everywhere on the planet, the Sun spent exactly 12 hours above the horizon and 12 below, and the Sun rose due East and set due West. From now through March, the Sun will be above the horizon more than 12 hours a day in the Southern Hemisphere, and less than 12 hours a day in the Northern Hemisphere.

I love the symmetry and simplicity of the Sun's motion on this day. It marks a transition as the days are getting shorter in the Northern Hemisphere. Everyone can feel the shortening of the days and sense, innately, that the changes in daylight and darkness are sudden and surprising. This is another fascinating change happening at the Equinox, more subtle but no less fascinating to me. When people sense the changes to the onset of darkness in the evening or the late sunrise in the morning, they are noticing that the length of the day is changing quite quickly and they feel that the times of day that might have been bright and sunny only a few weeks ago are now getting dark. At the time of the Equinox, the length of the day is changing most rapidly. For example, here in the San Francisco Bay Area, the longest day in summer is nearly 15 hours long and in winter the shortest day is approximately 9 1/2 hours. As the seasons change, the time of sunset and sunrise changes slowly, starting at the solstice in June - maybe only 1/2 to 1 minute per day. But then the changing becomes more rapid approaching the Equinox. At the time of the Equinox this week, the length of a day is changing 3 minutes per day -- that is, about 20 minutes in one week! So if you feel like the length of the days is changing very fast, you are absolutely correct.

The change is even more dramatic the farther north or south you are. For example, in Alaska, the length of the day is changing right now about 5-6 minutes per day, or about 40 minutes in one week! Imagine how that would feel, and it is a natural thing that happens every Spring and Fall. I think it is amazing how much the seasons impact the different geographies of the world, and a little understanding of the natural foundation for these effects is a nice thing to have.

Jupiter's closest approach to Earth

Today Jupiter is at its closest point to Earth for 2010, a mere 368 million miles. Although not a particularly astonishing event, it is nonetheless a prime time to get out your binoculars or telescope to view the giant planet as it dominates the night sky. Jupiter is a fun target to view up close because it offers so much to see: Four bright Moons, colors and textures from its cloud belts, and for a brief time right now it guides you to find the distant planet Uranus.

Every year as the Earth moves around the Sun, at some point in time it is at its closest approach to Jupiter. This moment is called "opposition" and is when the Earth, Sun and Jupiter are all in a perfect line. Each year the distance between the Earth and Jupiter might be a bit more or less depending upon the circumstances of each planet's orbit. This year, the distance is smaller than usual (closest since 1963 and until 2022), but that difference is relatively small from year to year. More important is that the planet is at its brightest for the year, and remains high in the sky for optimum viewing for the entire night.

Sky and Telescope Magazine has an excellent article about this close encounter if you want more details.

Blue Star, Red Star, Yellow Star

When conducting a star party, I always point out star colors. Most of the time, people see the stars as uniformly white, but in fact upon closer inspection it's easy to see that stars have color, sometimes very dramatic color. This time of year there are several colorful bright stars that illustrate nicely the range of what you can see in the sky.

The southern sky is dominated by the distinctive shape of Scorpius, the Scorpion of the Zodiac constellations. The "heart" of this constellation is the bright red supergiant star Antares. It is in the middle of the body of the scorpion and it is one of the biggest stars we can see, so big that if places in the Solar System it would enclose Mercury, Venus, Earth and Mars. To the observer, it looks a reddish-orange color.

High above this time of year is the Summer Triangle, featuring three of the brightest stars in the sky. One of these three is Deneb in the constellation Cygnus, the "Northern Cross." Deneb appears blue to the observer and in fact is indeed a blue-white supergiant star, similar to Antares in terms of massive size, brightness and distance from the Sun.

These two beautiful stars should be enough to whet your appetite for detail when you look at the night sky. They are bright enough and easy to spot and display color quite nicely. But don't stop there. A simple pair of binoculars gets you enough resolution to see an amazing array of color in so many of the stars in the sky.

The colors of the stars is an indication of their temperature. Like the different levels of heat in flame, the colors of stars follows a similar pattern with red being cooler and blue being hotter. There are yellow stars, hotter than the red giants, and next in line are white stars, cooler than the blue stars. Details of Stellar Classification and Color Index are documented on very fine websites for those who want to learn more about star colors.

KFOG Podcast - September 10, 2010

Another fun visit with Irish Greg of the KFOG Morning Show, today featuring a discussion of constellations to see this time of year (Sagittarius, Scorpius, The Summer Triangle) and the difference between an asterism and a constellation, plus deep-space objects you can see in the Milky Way with an ordinary pair of binoculars. And the latest happenings with the Moon and Venus, and an update on a great star party and lecture this weekend. All in 7 short minutes! Click here to listen.

Get Involved: Astronomy Lectures, Star Parties and more

The Bay Area has many great astronomy resources and if you want to expand your knowledge of the universe and have a good time, check out one of these upcoming astronomy-oriented events.

Star Party and Lecture on Mount Tamalpais: The San Francisco Amateur Astronomers (SFAA) hosts monthly lectures and star parties at the Mountain Theater on Mount Tam in Marin County from April through October. Ken Frank is giving a talk this weekend (Saturday 11th September at 8:30 pm) on the Globe At Night project, highlighting the effects of light pollution

worldwide. Details on the Mount Tam website. Following the lecture, the SFAA has telescopes set up for public viewing.

Benjamin Dean Lecture Series at Cal Academy: The California Academy of Sciences in Golden Gate Park in San Francisco hosts excellent programs on many areas of science. The Dean Lectures focus on astronomy and this month (Monday 13th September at 7:30 pm) the talk is on the Search for Extraterrestrial Intelligence (SETI) with Jon Jenkins of the SETI Institute. Tickets and information at the Cal Academy website.

The San Francisco Amateur Astronomers monthly meeting is always open to the public. This month's meeting features NASA Ames astronomer Chris McKay speaking about extreme environments on heavenly bodies in the Solar System. The meeting is on Wednesday 15th September at 7:30 pm at the Randall Museum in San Francisco. More details on the SFAA Website.

I hope to see you at one of these excellent events.

Perspective of the Solar System

After weeks of foggy skies in San Francisco, the sky has started clearing, yielding spectacular sunsets and sky shows at Ocean Beach. I have been writing about (but not seeing much of) the amazing sight of the planets dancing across the evening sky. With the clear skies, the view was great, showcasing Venus and Mars very close together, with Saturn just to the lower right and the bright Zodiac start Spica (in Virgo) just to the upper left.

This configuration traces a curve in the sky and if you have a clear southern horizon you can "connect the dots" from this cluster of stars and planets to the south where bright Jupiter dominates the sky. Beyond that, the Moon is slicing across the lower southern sky, providing the observer with a nice visual of the Ecliptic, the line of the planets, Moon and Sun. This is a great way to visualize the path of the planets in the Solar System when you look out from our Earth-bound perspective.

Over the coming months, Mars and Saturn and eventually Venus fade, but the giant planet Jupiter will be dominating the Fall skies.

Perseid Meteor Shower 2010

The Perseid Meteor Shower reaches its peak this week and the timing is very good for a fine display of meteors. Every year when the Perseids come around, the biggest concern is the Moon. Its beautiful light is a welcome sight to many, but for amateur astronomers and anyone wishing to see more than a few meteors, moonlight can ruin an otherwise-perfect evening of viewing. This year the Moon is very young during the Perseids and sets not long after sunset, leaving a dark sky for the shower.

The Perseids peak on the nights of Thursday 12th and Friday 13th, with best viewing on Thursday night / Friday morning. You can get detailed information on the Sky and Telescope website or on numerous other web resources.

The best way to see the meteor shower is to find a dark location, give your eyes plenty of time to adapt to the darkness, and be prepared to stay up late (or get up early). Meteor showers are almost always best viewed after midnight when the Earth is powering directly into the meteor stream and the rate increases substantially. The Perseids appear to originate in the constellation Perseus which is in the east after midnight, but that does not mean you have to specifically look east to see the meteors. Lying on a blanket facing directly overhead gives you the most expansive view and you can see meteors coming from the east or passing overhead toward the west. Meteors are wonderful, fast, elusive wonders and you simply need to be warmly dressed, in a place where you can see as much of the sky as possible without light distractions, and patience. I wish you clear skies and a great night or two observing.

Trio of Planets

The evening sky brings us a trio of planets in a close grouping this week. The bright beacon of light, Venus, shines brightly and moves quickly from night to night, especially by comparison to the slower-moving Mars and Saturn. The image shows the view on Sunday August 8th, so looking at this earlier in the week you will find Venus lower and to the right of the other two planets, and after the 8th you will see Venus glide to the upper left of the two planets. We are witnessing the motion of Venus along its orbit around the Sun, moving much more quickly from our vantage point on Earth than Mars and Saturn. Venus will continue to dominate the evening sky for many weeks to come.

KFOG Podcast - July 16, 2010

I was in San Francisco this morning recording another podcast for the KFOG Morning Show Podcast Series. Morning Show Producer Irish Greg and I had a very spirited and lively conversation about planets, the Solar System, Star Parties, Iridium Flares, Dark Energy and Dark Matter. In a fast-paced 9-minute conversation we discuss everything from the phase of the Moon to the origin of the Universe. Get inspired to see the sky tonight: Click here to listen.

A Must See: Four Planets and the Moon

This week the sky features four of the brightest planets in a beautiful lineup in the sunset sky. The illustration on the left, borrowed from Sky & Telescope Magazine, demonstrates how the planets all align themselves in a path across the sky known as the Ecliptic. This line in the sky, actually a gentle curve from west to east across the south part of the sky, is the plane of the Solar System as viewed from our observing platform on Earth. We see fast-moving Mercury close to the Sun, then Venus, Mars and Saturn, a most impressive line-up.

To set this into perspective, the young Moon emerges from the glare of the Sun on Tuesday 13th, moving somewhat parallel to the Ecliptic but each day a bit farther south of the Ecliptic. This is because the orbit of the Moon around the Earth is slightly inclined to the rest of the bodies in the Solar System. And as we just had a Total Solar Eclipse on Sunday, the Moon is following a path away from the Ecliptic into what is called the "descending node" south of the Ecliptic.

I will be talking about this at the California Academy of Sciences at their Nightlife event this Thursday in Golden Gate Park. If you are in or near San Francisco, please join me on the roof for Star Tours!

Total Solar Eclipse 2010

One of the most dramatic spectacles of nature takes place Sunday July 11th, as the New Moon passes in front of the Sun and creates a Total Solar Eclipse over the South Pacific Ocean. This eclipse will be especially unique for those who travel to Easter Island to see it. As the shadow of the Moon sweeps across the ocean at speeds of up to 1000 miles per hour, the darkness will pass directly across Easter Island and the famous Moai, the large stone statues that are nearly 1000 years old.

I have experienced Total Solar Eclipses in the past and they are remarkable, not only for the brilliant image you see in the sky, but also for the dramatic changes in the environment you experience as the sky slowly darkens, the horizon changes color, the animals begin to react strangely, and the fellow eclipse-chasers react with great anticipation. Although I will not travel to this one, I plan to travel to one of the upcoming eclipses in the next few years.

For those in the US who don't want to travel far, your next chance to experience at Total Solar Eclipse will be 2017.

Star-and-Planet Drama

The evening sky over the next few weeks offers a study in the changes that take place in the sky along the path of the Moon and the path of the planets. This is exciting to watch and helps to unveil some of the intricacies of the Solar System, something you can see right from your own backyard. For quite a while now I have been particularly fond of sharing the path of the planets across the sky (the "Ecliptic") while conducting star parties and giving astronomy talks. I find that the ability to visualize this band across the sky is an important one for those who wish to have a basic understanding of the motion of the planets across the sky. And for several months the bright planets, a collection of bright stars, and the monthly sweep of the Moon across the sky have provided a perfect laboratory for learning. This month is no exception.

Shortly after sunset there is an excellent parade of planets and stars easily visible as the glare of dusk fades, starting with brilliant Venus in the west, and then in succession from west to south are Regulus, Mars, Saturn and Spica. These bright objects show the line of the Ecliptic.

At the end of this week there is a total solar eclipse (unfortunately not visible

from the San Francisco Bay Area). The eclipse comes at the middle of an Eclipse Season and as such, the Moon follows a descending path below the Ecliptic in the days that follow the eclipse, in particular from the 12th to the 17th of July. As it moves from day to day, it swoops just below the Ecliptic and makes a pleasant arc across the southern sky below Venus and Regulus, then Mars, then Saturn and then Spica.

And in addition, we are just coming into a period of time when fast-moving Venus has close encounters with the other planets and stars along the Ecliptic, starting with a close encounter of Regulus on the 9th of July. More drama to come in the next few weeks -- stay tuned!

The Path That Leads to the Earth's Shadow

We are in an "Eclipse Season," a five week period of time when the Moon's orbit around the Earth is aligned in a way that the Full or New Moon crosses the path of the Earth around the Sun. When that happens, we experience a Lunar or Solar Eclipse and right now we have one of each coming up: a partial Lunar Eclipse on Saturday 26th, and a total Solar Eclipse on July 11th. The Solar Eclipse will not be visible from North America so we don't get a chance to experience that, but the Lunar Eclipse will be. More on that next week.
During an Eclipse Season, the Moon's position in the sky is special, as it is moving just above or just below the plane of the planets (the "Ecliptic") in the interval from New Moon to Full Moon. A few days ago as the Moon emerged from the evening glare waxing each evening, you could see it move just below Venus, then below Regulus and Mars, and now it is below Saturn and Spica, all objects on or near the Ecliptic. As it nears Full Moon and the Lunar Eclipse on the 26th, it is moving closer and closer to the Ecliptic and will intersect the Earth's shadow on the 26th.
I like to imagine that there is a dark spot in the sky where the Earth's shadow projects out into space. Every month as the Moon nears Full, it sweeps close to that spot. But only during an Eclipse Season -- every six or twelve months -- does it slip into the shadow of the Earth and display to all of us the curved shadow of the Earth. That is something to look forward to next weekend.

Heavenly Line-Up

Over the past months the evening sky has been graced by a number of bright stars and planetary configurations. As summer approaches and these stars and planets move westward toward the sunset day after day, heavenly line-ups are emerging that are beautiful to see and are dynamic in nature, changing dramatically from one day to the next.

This evening the planet Venus moves into a very impressive alignment with the two “twin” stars of Gemini, Castor and Pollux. Although Venus is considerably brighter than the two stars, the pattern of the three celestial objects will be distinct, emerging from the sunset glow with Venus as the guide star and Castor and Pollux shining a short while later.

On the 13^th and 14^th, the trio is joined by the young crescent Moon. The combination of these heavenly bodies in the twilight should be an impressive sight indeed.

KFOG Podcast - June 4, 2010

Today I spent a few minutes talking with Irish Greg of the KFOG Morning Show for their podcast series. Greg is one of those people with boundless enthusiasm and an insatiable appetite for discussion about any topic, so when we talk astronomy it's always a good time. Today's conversation ranged from the Summer Solstice to the upcoming lineup of Mars and Venus and some bright stars, to the June 26th Lunar Eclipse and the Search for Extraterrestrial Intelligence (SETI). Click here to listen.

High in the sky: The Big Dipper

The Big Dipper is one of the easiest groupings of stars in the sky to identify, and it serves as a guide to some of the more interesting stars in other parts of the sky. Late Spring evenings it is nearly overhead as seen from San Francisco, and its distinctive pattern provides an interesting exercise for understanding the motions of objects in the heavens.

The Big Dipper is not a constellation, by strict definition, because it is only the brightest 7 stars of the larger constellation Ursa Major. A named combination of stars within a constellation such as the Big Dipper is known as an "asterism." Because of its distinctive shape, the Big Dipper is a very well known asterism, one of several celestial groupings that lives up to its name (I put Leo, Scorpius, Cygnus and a few other constellations in this special class).

The Big Dipper points to the North Star (Polaris) if you follow the two stars at the side of the bowl of the dipper. This Wikipedia article illustrates this nicely. The line along the pointers from the Big Dipper to Polaris is helpful because this line is similar to an hour hand on a 24-hour clock. Every 24 hours the Big Dipper makes one counter-clockwise rotation around Polaris. From latitude 38 degrees north (approximately the latitude here in San Francisco) the Big Dipper is high in the sky when it is above Polaris (as it is now at sunset) and low in the sky when it is rotated half way around Polaris just above the horizon (as it will be in late Fall evenings).

The three stars in the handle of the Big Dipper form a curve, and if you think of this curve as an arc, you can follow it to a very bright star called Arcturus (in the constellation Bootes), and by continuing along this arc you end up at another bright star called Spica (in the constellation Virgo).

One more fun thing to find in the Big Dipper is the middle star of the handle, known as Mizar. This star has a very close companion, Alcor, next to it and if you want to test your eyesight, see if you can split the two without using binoculars or a telescope.

Enjoy learning about the Big Dipper in the pleasant weather of May and June. It's full of surprises and one of my favorite stops when sharing the sky with friends and guests at star parties.

Planets and Bright Stars along the Ecliptic

This is a great time of year to enjoy the view of bright stars and planets demarcating the ecliptic. I am hosting a lot of star parties these days (last week in Tomales, this week in Fremont, next week in Healdsburg and the week after in San Mateo) and I always love to point out the ecliptic, the band across the sky where the planets and Moon are found in their wanderings across the heavens.

The ecliptic is the plane of the Solar System, the imaginary line across the sky that marks the orbits of the planets and the Moon. In a planetarium this can easily be shown, but under the heavens it is daunting to visualize this. I use a laser pointer to show the path across the sky, and that helps to visualize this, but right now the skies are cooperating to make this a bit easier for those of you without an amateur astronomer and a laser pointer :-)

Face South about 30-45 minutes after sunset and you will be looking toward the ecliptic. It stretches from the point of sunset to your right (West) where bright Venus gives you one reference point, then stretches up and toward the south to Castor and Pollux, the two twin stars of the zodiac constellation Gemini. Just to the upper left of the pair is bright orange Mars, and continuing left you encounter blue-white Regulus, the brightest star in the zodiac constellation Leo. Now the line of the ecliptic moves down toward the East, that is, down and to the left as you face South. Lower left of Leo is the planet Saturn, a bright, milky-white dot of light. And continuing to the lower left of Saturn is the bright star Spica, in the zodiac constellation Virgo.

Enjoy the tour, and if you have a star chart, put it to work so you can use these bright points of light to help you learn a few constellations. Even in the big city, all of these are visible.

The image on this page was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version.

A Beacon in the Twilight

As the days grow longer and the last vestiges of twilight linger later in the evening, look to the West this week for some very beautiful planetary/celestial lineups. The week features fast-moving Venus passing very near to some of the most spectacular star clusters in the night sky, the Pleiades and the Hyades.

When you look into the twilight sky, the brightest objects shine majestically against the bright blue background. That is the case for Venus this week, as it is for the young crescent Moon each month when it shines low in the West in the first few days after new Moon. However, in order to see the star clusters near Venus, you will need to use binoculars. The stars are there to see, but the bright twilight makes them all but invisible to the naked eye. It's worth the time to get out and see this spectacle. Sunset in San Francisco is just before 8:00 pm, and the sky will be dark enough about 45 minutes to an hour after that.

KFOG Podcast - April 14, 2010

Mars and the Beehive

Over the past few weeks I have been watching the gradual change in position of Mars as it moves from retrograde to prograde motion across the sky, now moving steadily eastward across the constellation Cancer and next to a beautiful cluster of stars knows as the Beehive Cluster, or M44.

Mars, like all other planets, moves eastward from our point of view most of the time but when Earth have just the right alignment (as we did with Mars over the last few months) a planet may appear to travel westward, and we call this motion "retrograde." Click on the image to see how Mars was in retrograde from December through March.

Now that Mars is moving eastward again, it is traversing a part of the constellation Cancer where you can find the Beehive Cluster, an open cluster of stars (like the nearby Hyades cluster in Taurus). It is relatively close to the Solar System compared to most clusters, and it is a gem in binoculars. With Mars as your guide "star" you can easily navigate to the Beehive Cluster high overhead this time of year. It's worth a few minutes to see if you can spot it.

Seeing Mercury in the evening sky

Mercury makes its way into the evening sky, visible shortly after sunset for the next few weeks. The fleet-footed planet never strays far from the Sun from our point of view, so we get glimpses of Mercury in the evening, then the morning before sunrise, and again in the evening several times a year. Right now Mercury is going to be easy to find because it will move near Venus this week. Venus is the bright evening "star" in the west, shining through the glow of dusk, and Mercury, although dimmer, will be fairly easy to spot now that you know where to look.

Full Moon Fever

It's time for the first full moon of Spring, rising up to dominate the sky Monday evening. The first full moon following the Vernal Equinox (the moment when Spring arrived on March 20th) marks the arrival of Passover and Easter week, holidays that are based on lunar calendars. The Moon passes near Saturn on its trek across the eastern sky in the early evening on the 28th and 29th, and then onward toward the bright star Spica on the 30th. The Moon is full at exactly 7:25 pm pacific time on Monday 29th.

Winter Triangle

One of the highlights of the winter sky is the Winter Triangle. This shape is a nearly perfect equilateral triangle that shines in the southern sky over the next few months. It includes three of the most brilliant stars in the sky, and it is called an "asterism" because it is not a single constellation, but a combination of stars from three different constellations.

The first and brightest star is Sirius, the brightest star in the night sky. Sirius is close to the Solar Systems (8 light years) and has a slight blue coloration. Sirius is in the constellation Canis Major, the big dog that accompanies Orion. To the upper right is Betelgeuse, a red supergiant star in Orion that is a distinctive orange color. Betelgeuse is so big that if it was our Sun, it would envelop Mercury, Venus, Earth and Mars! And the third star of the triangle is Procyon, in the constellation Canis Minor, the small dog that accompanies Orion. Procyon is actually a double-star system with a faint partner star.

Inside the Winter Triangle you can find numerous clusters of stars. I spent some time looking here a few nights ago and was able to see quite a few of these clusters, even in San Francisco. My backyard has a dark western horizon so by looking through binoculars later in the evening I was able to see quite a bit in and around the asterism. Try this for yourself sometime soon.

KFOG Podcast - Mar 16, 2010

Get Involved: Chart the Skies, Hear a Lecture, Attend a Star Party

There are many ways to take your interest in astronomy up a notch. Here are a few things that are sure to enhance your interest and knowledge of the skies.

Globe at Night: I am a big fan of this annual project, one that combines astronomy with awareness of light pollution and is also a global participation project. Go outside tonight and look up at Orion, then report what you see at the Globe at Night website. It only will take a few minutes but it will change how you see the sky at night. I am certain about this one.

Lecture: Each month the San Francisco Amateur Astronomers hold their meeting at the Randall Museum in San Francisco. The meetings are open to the public and feature a speaker on a topic of interest in astronomy. This month the meeting takes place on March 17th and features Andrew Pohorille from NASA Ames Research Center for a presentation on "The Origins of Life in the Universe."

California Academy of Sciences Nightlife: Every Thursday the Cal Academy stays open late for a fun, festive evening with music, drinks and science. When the skies are clear you can stargaze and look up close at the universe through telescopes on the Living Roof. And this week, on Thursday March 18, I'll again be a guest at NightLife giving a talk about the Night Sky and laser-guided star tours on the roof. I hope to see you there. (note: must be at least 21 years of age)

Star Parties: The San Francisco Amateur Astronomers host monthly star parties at Lands End in San Francisco, weather permitting. The next on is on Sunday March 21st. And on April 17th the Mount Tamalpais lecture series and star parties return. These are an excellent combination with lectures at the Mountain Theater and star gazing in a dark setting atop Mt. Tam. You won't be disappointed -- even when it is foggy in San Francisco it is generally clear and dark on Mt. Tam.

The Moon and the Ecliptic

Continuing from the last post, here's a snapshot of the Moon continuing on its journey across the morning sky, a series of guideposts to the Ecliptic. The view is what you would see around 5:30 am each morning here in San Francisco.

Moon Traveling Along the Ecliptic

The Moon, like the planets and the Sun, travels along a special path in the sky called the ecliptic. Observationally, the path arcs generally across the southern half the sky from west to east, but it is not a simple arc that is in the exact same part of the sky year round. Rather, it curves higher in the sky and lower in the sky as the seasons change.

Right now, in late winter, the Sun remains low in the sky but is gradually climbing the ecliptic, getting slightly higher each day. The Moon this week is just past full, and therefore is traveling along the opposite side of the ecliptic in a part of the sky where the ecliptic follows a low arc in the sky from west to east. And because the Moon takes 29 days to circle the Earth once, and the Sun appears to take 365 days to "circle" the Earth once, we can observe the Moon's motion along the ecliptic much more readily than the Sun's. The image helps to visualize this over the course of four days in which the position of the Moon at the same time in the dawn (an hour before sunrise, about 5:30 to 5:45 am this week in San Francisco) traces out the low, sloping arc of the ecliptic -- and slices close to Saturn as well.

The Urban Astronomer speaks!

I want to let Bay Area readers know about a very exciting event coming up on Tuesday March 2nd in San Francisco. The event, Ignite Bay Area, is one of a collection of global "Ignite" events happening next week. If you have never experienced an Ignite presentation, they are very fast and focused 5-minute talks about everything from geek technology to social trends to .... astronomy! I'll be presenting a talk on amateur astronomy that I trust will inspire and motivate many to look up in the night sky and make a cosmic connection. Hope to see you there!

Winter Sky Show: Gemini, Mars and the Moon

Gemini is one of the finest constellations you can see during the winter months, easy to spot because it traverses the highest spot in the sky (the zenith) and features two bright stars, the twins Castor and Pollux. These two stars are well known because they symbolize the heads of the mythical twins. The stars that make up the rest of the bodies of the twins are less bright and require slightly darker conditions than we will have this week, but I provide an image nonetheless so you can see the rest of the stars when conditions permit.

Mars is the bright orange beacon of light that is gracing the night sky, the brightest object high in the sky for the next many weeks. As Mars orbits the Sun, we observe it moving against the backdrop of the Zodiac constellations, changing its position gradually from month to month as it travels eastward from our Earthbound perspective (this is called prograde motion, in contract to retrograde motion – more on that in a future post). It is about to start moving away from the twins of Gemini through Cancer toward Leo the Lion where it will arrive in May.

The Moon sweeps through this busy part of the sky, passing slightly south of Gemini, Mars and later this week the bright star Regulus in the constellation Leo. The bright Moon will drown out the background stars of these otherwise bright constellations, but the prominent stars Castor, Pollux and Regulus, along with Mars, will shine beside the waxing gibbous Moon. Binoculars or a telescope are a good idea if you want to see this close up!

KFOG Podcast - Feb 12, 2010

I've been a frequent guest on KFOG 104.5-FM in San Francisco for the last two years. I am going to start a new series of programs with KFOG's Irish Greg that they will include in their Morning Show "Web Show" page. I am looking forward to regular recordings with KFOG, keeping the Fogheads up to date with the goings-on in the sky. Here's the first of our recordings with conversation about what to see in the Winter sky, a few words about the San Francisco Sidewalk Astronomers, and some tips for telescope shopping.

Old Moon, Young Moon

Every 29 1/2 days the Moon completes one cycle in its orbit around the Earth. For the last few days of the cycle we have an "old moon" and then just after New Moon we have the opportunity to see a very "young moon." I love the challenge of locating the very thin crescent Moon on the horizon, but when found, the reward is worth it, because the Moon always looks a jewel in the sky.

This week we've had a few opportunities to see the very old moon passing by Mercury in the dawn glare. After the New Moon on Saturday, find a good western horizon and try to locate the very young Moon in the glow of dusk. On Sunday 14th it will pass just next to Jupiter and Venus, extremely low on the horizon. You will want to have binoculars nearby to enhance the view. On Monday the Moon is higher in the west, and by Tuesday it is an easy target in the sunset sky. Well below the Moon on Tuesday, however, Jupiter and Venus have their closest approach for quite a while, being about 1/ 2 degree apart (a moon width). For this, you will want binoculars because the two planets will be just on the horizon after sunset.

Get Involved: Cal Academy, Star Parties, meet John Dobson

February is a busy month here in San Francisco for those who are ready to take a step forward and get involved in a local astronomy event or two. Here's the lineup.

On February 11, the San Francisco Amateur Astronomers (SFAA) team up with the California Academy of Sciences for a new series of astronomy talks and star tours on the Living Roof of the Cal Academy. I'll be giving the talk this Thursday during the NightLife event at 7:15 pm. More information and tickets on the NightLife webpage.

On February 17, the SFAA holds its monthly meeting and lecture at the Randall Museum in San Francisco. And on February 20th they have their City Star Party and Telescope Workshop. You can dust off your old telescope and bring it out for a quick lesson on using your telescope (before the sun sets), and then enjoy stargazing at the City Star Party. This is at Lands End in San Francisco.

On February 25th and 26th, the amateur astronomy community of San Francisco bids farewell to a living legend in the field, John Dobson. John is a co-founder of the San Francisco Sidewalk Astronomers (they call what they do "urban guerilla astronomy") and the creator of the easy-to-build and easy-to-use telescopes that bear his name, Dobsonians. There will be a get together with John on Thursday 25th in the Sunset District of San Francisco, and sidewalk astronomy with John at a location to be determined in the city, to say Farewell as John moves from San Francisco to Los Angeles. I am impressed with Sidewalk Astronomers and especially with John Dobson, who had a singular vision to make telescopes accessible to anyone who wants to build one out of inexpensive parts, and to get these telescopes out on the street so everyone can appreciate the wonders of the sky and see something they hadn't seen before. I respect that.

I hope to see you at one of these events.

Annular Solar Eclipse of 2010

Eclipses are very exciting events, special moments that provide beautiful visual spectacles in the sky. Every year there are typically two to three eclipses of the Sun ("solar eclipses") and two to three eclipses of the Moon ("lunar eclipses"). And for each eclipse the event can be "total" (where the Sun or Moon is fully blocked out), or "partial" where a portion of the Sun or Moon is blocked out, but a portion is still visible.

Last month there was one such event, a type of solar eclipse called an Annular Eclipse. In this configuration, the Moon's disk appears to block out most the Sun but does not completely block it out. What makes the Annular Eclipse very special, however, is that the disk of the Moon is fully encircled by the Sun. The eclipse in January was not visible here in San Francisco but was seen in the eastern hemisphere. A fellow astronomy blogger and resident of Sri Lanka, Desh, put together an eclipse page that has video footage of the event and lots of great photographs. He organized a major eclipse viewing event for Sri Lanka.

Throughout 2010 there are more eclipses. The biggest event of the year is the Total Solar Eclipse that happens this July 11th, but again will not be visible here in San Francisco. To see this one you will need to travel to the South Pacific. The NASA Eclipse web site is full of details on this and every eclipse and for those of you who want to travel to see a Total Solar Eclipse someday, consult the NASA Total Solar Eclipse Paths map on their website. I think of it as a long-range travel planner!

For those of us in the Bay Area (and the entire Western Hemisphere), mark your calendars for December 21st when we get a beautiful Total Lunar Eclipse on the solstice to welcome in the winter.

Note: for a nice audio description of an eclipse, listen to my recent interview on KALW (just after the stargazing part of the interview).

Leo the Lion

Leo is one of the twelve zodiac constellations, the name "zodiac" sharing its origin with the word "zoo" -- appropriate for the ring of mythical animals found in the sky. Leo is a very easy-to-locate constellation because it has one very bright star (Regulus) and quite a few moderately bright stars in a distinctive pattern that resembles a lion. The image at left shows the general outline of the stars in Leo, with the sickle (or backwards question mark) at the head of the lion, something that is easily identifiable as Leo rises in the east in the winter. For the coming months, it will be appearing higher in the east and traversing nearly overhead throughout the evening.

Because they form a band around the sky that follows the Sun's path, each of the zodiac constellations has frequent visitors as they grace the night sky, from the Moon to the planets. Leo has been the home of Saturn for the last three years, but now Saturn is drifting slowly eastward into Virgo. On the west side of Leo is Mars, currently in retrograde in Gemini, but soon to be speeding toward Leo and a close encounter with the bright star Regulus in June.

Take some time to become acquainted with this celestial Lion, and you'll know how to quickly navigate to Saturn and Mars throughout the spring and into the summer.

Mars and the Biggest Full Moon of 2010

The next few days offer a chance to see Mars and the full Moon together while each celestial body passes through its closest point to the Earth in their orbit. When Mars and Earth line up in their orbits around the Sun, we call that "opposition" and it represents the closest approach between the two planets. This takes place approximately every two years and when it does, Mars appears brighter than usual and is larger in a telescope. Also at opposition, Mars rises just as the Sun sets and is up all night. Mars is at opposition on Friday January 29th.

The Moon has an elliptical orbit around the Earth and as such, each orbital period (approximately 29 days) it is a bit closer to Earth (called Perigee) and then a bit farther from Earth (called Apogee) This month, the Moon is full and is at Perigee on the same date, Friday January 29th. It is also next to Mars so when you look outside on Friday evening, you'll be seeing a nice lineup of a couple of our nearest neighbors. When the Moon is at Perigee, it is a considerably bigger object in the sky than usual. The website Spaceweather.com highlights this nicely in their article.

I have written about the biggest full moon of the year in a previous blog post, if you want to get more information about that subject.

Regarding Mars and opposition, there was a great deal of hype in August 2003 when Mars had a particularly close opposition and was inaccurately stated as "being as big as the Full Moon." That won't ever happen, of course, but it certainly inspired a lot of people to take a look at Mars that summer. This week Mars will be less bright and big compared to 2003 but still a worthy binocular or telescope target. The next close encounter that will rival the 2003 lineup will be in 2018. For an extremely detailed chart and description of the Mars opposition phenomenon, visit the seds.org site.

Jupiter and a Young Moon

Despite the cloudy weather here in San Francisco these last few days, bright Jupiter shines through from time to time as it slowly works its way down the western sky after sunset. The next few days offer a chance to see one of my favorite views, that of the young Moon and a bright planet. In this case the waxing crescent Moon slides across the south-western horizon each night for the next few nights. With Earthshine illuminating the dark portions of the Moon, the visual effect is quite striking. If clouds part in the next few days, find a good western horizon for this beautiful scene.

KALW broadcast - January 14, 2010

Review of iPhone astronomy apps: iSolarScape and Planets

My admiration for the iPhone grows as I add more astronomy apps to it. Continuing from my last review of iPhone apps here on the Urban Astronomer blog, I review two more apps that I enjoy using.

iSolarScape: This is an impressive app for $0.99. It provides a broad range of information for the star gazer, from fun facts and figures about the Solar System, to up-to-date information about sunrise, sunset, Moon phase, the location of Jupiter's Galilean Satellites, and more. iSolarScape is the first app I reach for when I want the basics before an evening of stargazing.

The core views of the app are: Sun, Moon, Planets, Asteroids and Zodiac. I use the Sun and Planets selections the most, because they offer me important timing information and wonderful facts and figures about the objects in the Solar System. When I am conducting a star party, iSolarScape has answers to the typical questions (and also the fun and unusual questions) being asked: how far away is a planet, how hot (or cold) is it on the Moon, how many moons does Saturn have, and so on. I marvel at the range of information and ephemeris data I can find throughout the app.

For a great visual tour visit the iSolarScape website.

Planets: This fine app provides a wealth of information and given that the price is free, just load it up and enjoy! A recent upgrade added the "Sky 3D" view, an excellent map of the constellations of the night sky, something that is easy to use and yet quite complete, especially for an Urban Astronomer like me that can only see the brightest stars in constellations most nights. Another view is "Visibility," a planet-by-planet display of when a particular planet is visible in the sky (with back-side data and fun-facts about each object in the Solar System). The "Globe" view is a very cool 3D display of each planet in the Solar System and of course a beautiful Earth map that can be spun around and tilted in any direction allowing you to see the lit side or night side of the Earth.

The publisher of Planets, Dana Peters of QContinuum Software, has a very simple website. For much more vivid illustrations of the Planets app visit the iTunes Store.

I'll have more iPhone asrronomy app reviews in the coming months. Happy viewing!

International Space Station coming to a city near you!

The International Space Station (ISS) is one of the brightest satellites visible in the sky, and for the next few evenings it is making a particularly good set of passes over the USA and Canada in the evening. If you have not seen it fly over, it is worth a few minutes out of your day to use an online tool such as the Simple Satellite Tracker from spaceweather.com or the NASA Satellite Tracker.

Here in San Francisco we can look forward to four consecutive evenings of good fly overs. Wednesday 6th it is visible from 6:36 to 6:38 pm, Thursday 7th it is visible from 5:59 to 6:02 pm, and Friday 8th it is visible from 5:44 to 5:47 pm.

The ISS looks like a fast-moving airplane, but the light is perfectly smooth (not blinking, not red and white) and the path is a very clean arc from west to east. Given the current orientation of the ISS as it orbits Earth, the upcoming passes across North America will generally be from the west to east and from the south to north.

Mars arrives in the evening sky

Mars is back on display, now visible shortly after sunset in the eastern sky. During the month of January it will reach "opposition" when it appears exactly opposite the Sun in the sky. At opposition Mars is also at closest approach to Earth (and is therefore at its brightest for the year). It shines a distinctive red-orange color especially when compared to the stars in Leo and Cancer that surround it. Through binoculars or a telescope Mars appears as a small colorful dot of light. This week the Moon serves as a guide for locating Mars.