11 March 2008
Space Shuttle and Space Station visibility
The Space Shuttle launched this morning and will be orbiting Earth for the next few weeks. While orbiting, it will be docked with the International Space Station from the 12th to the 24th. The two will be visible on a regular basis for brief periods just before sunrise or just after sunset. Look here for details of visibility from San Francisco. You can also check visibility for any location on Earth.
04 March 2008
24 February 2008
How to see Mercury
I've been asked in the past how to find Mercury. Because it is so close to the Sun compared to any other planet in the Solar System, it is harder to spot than the rest and never appears very far away from the Sun (that is, it never appears high up in the night sky). However, because it is relatively close to Earth, it can also become quite bright. These two factors combine to make Mercury a challenge to see but still a fun goal for many. The coming weeks offer an opportunity to try to see it.
Mercury and Venus are both circling the Sun inside the orbit of Earth and both move faster than Earth. In a single 12 month period of time, Mercury will circle the Sun over 4 times. As it speeds on its orbit, it is visible low on the horizon in the evening or morning sky. Right now both Mercury and Venus are very low on the horizon in the morning and if you have a clear view and good timing, you can see the two dance along the horizon. The diagram shows where to look for them.
In 2004 NASA launched the Messenger spacecraft to explore Mercury and in January 2008 it finally made its first pass, flying just over 100 miles above the surface of Mercury. Messenger is returning some amazing photographs of the planet. To my surprise, Mercury looks exceedingly similar to our own Moon. For pictures, visit http://www.nasa.gov/mission_pages/messenger/main/index.html.
Mercury and our Moon have much in common, being of similar age, made of similar minerals, and both having no atmosphere*, they are bombarded by meteors and have no erosion or surface flows which change its appearance over time. Hence they both appear similar on their surfaces. For me, seeing the photos reminds me that there are lots of things we share in common with our neighbors in space and by exploring our own Solar System we can better understand what is happening in other star systems and galaxies.
* Note: Mercury has an extremely thin atmosphere due to the solar wind lifting particles off the surface of the planet, but this layer of atoms is being constantly "burned off" and is not a permanent atmosphere as we have on Venus, Earth or Mars.
Mercury and Venus are both circling the Sun inside the orbit of Earth and both move faster than Earth. In a single 12 month period of time, Mercury will circle the Sun over 4 times. As it speeds on its orbit, it is visible low on the horizon in the evening or morning sky. Right now both Mercury and Venus are very low on the horizon in the morning and if you have a clear view and good timing, you can see the two dance along the horizon. The diagram shows where to look for them.
In 2004 NASA launched the Messenger spacecraft to explore Mercury and in January 2008 it finally made its first pass, flying just over 100 miles above the surface of Mercury. Messenger is returning some amazing photographs of the planet. To my surprise, Mercury looks exceedingly similar to our own Moon. For pictures, visit http://www.nasa.gov/mission_pages/messenger/main/index.html.
Mercury and our Moon have much in common, being of similar age, made of similar minerals, and both having no atmosphere*, they are bombarded by meteors and have no erosion or surface flows which change its appearance over time. Hence they both appear similar on their surfaces. For me, seeing the photos reminds me that there are lots of things we share in common with our neighbors in space and by exploring our own Solar System we can better understand what is happening in other star systems and galaxies.
* Note: Mercury has an extremely thin atmosphere due to the solar wind lifting particles off the surface of the planet, but this layer of atoms is being constantly "burned off" and is not a permanent atmosphere as we have on Venus, Earth or Mars.
12 February 2008
Total Lunar Eclipse on February 20th
Mark your calendar for Wednesday February 20. Weather permitting, we will experience a total eclipse of the moon, one of the best timed eclipses in years and the last total lunar eclipse until December 2010. This one is timed well because it will be underway at sunset and will be at its peak during the 7:00 pm hour, much easier to see than the eclipse last August which took place in the middle of the night in San Francisco.
A total lunar eclipse is a beautiful showcase of many astronomical phenomena. Lunar eclipses were used by scientists hundreds of years ago to prove that the Earth is round because the darkening of the Moon is actually being caused by the curved shadow of the Earth. The early and late phases of a lunar eclipse are punctuated by the curved shadow of the Earth moving across the otherwise full Moon. These phases take a little over an hour to happen and as the Moon glides deeper into Earth's shadow, the illuminated surface of the Moon becomes less and less.
During the period of "totality" all direct sunlight is obscured by the Earth and the Moon fades into a dark disk, a rather stunning image to behold. Every total lunar eclipse has a different appearance because a small amount of sunlight is refracted by the atmosphere of the Earth and illuminates the otherwise-darkened surface of the Moon. The same effect that causes the sky to turn red, orange or pink at sunset is responsible for the color that you see on the Moon. Think of the light as the collective light of all the sunrises and sunsets around the entire globe. Since no direct sunlight is reaching the surface of the Moon during totality, anything we see will have been first refracted by the Earth's atmosphere, then it will have traveled 240,000 miles to the moon, and then will reflect back from the Moon to the Earth for us to enjoy!
If the Moon is very dark during the eclipse, you should be able to spot two bright objects on either side of the Moon. These are the bright star Regulus in the constellation Leo, and the planet Saturn. The entire grouping should fit nicely in the field of view of binoculars so get out whatever you have, dust it off, and pull up a chair. The totality phase of the eclipse will be from 7:00 until 7:52 pm.
By watching the eclipse from start to finish you can get a very good feel for just how far and fast the Moon moves in its orbit around the Earth. When the Sun sets on the evening of the 20th, the Moon will rise due east and quickly move across the southern half of the sky. This motion is due to the rotation of the Earth on its axis. However, the darkening of the Moon as it moves through the shadow of the Earth is due to the orbiting of the Moon around the Earth, something which is slower and thus more subtle. By watching the changing position of the Moon against Regulus and Saturn, you will be able to get a sense how far it moves against the background stars in a short span of time.
A total lunar eclipse is a beautiful showcase of many astronomical phenomena. Lunar eclipses were used by scientists hundreds of years ago to prove that the Earth is round because the darkening of the Moon is actually being caused by the curved shadow of the Earth. The early and late phases of a lunar eclipse are punctuated by the curved shadow of the Earth moving across the otherwise full Moon. These phases take a little over an hour to happen and as the Moon glides deeper into Earth's shadow, the illuminated surface of the Moon becomes less and less.
During the period of "totality" all direct sunlight is obscured by the Earth and the Moon fades into a dark disk, a rather stunning image to behold. Every total lunar eclipse has a different appearance because a small amount of sunlight is refracted by the atmosphere of the Earth and illuminates the otherwise-darkened surface of the Moon. The same effect that causes the sky to turn red, orange or pink at sunset is responsible for the color that you see on the Moon. Think of the light as the collective light of all the sunrises and sunsets around the entire globe. Since no direct sunlight is reaching the surface of the Moon during totality, anything we see will have been first refracted by the Earth's atmosphere, then it will have traveled 240,000 miles to the moon, and then will reflect back from the Moon to the Earth for us to enjoy!
If the Moon is very dark during the eclipse, you should be able to spot two bright objects on either side of the Moon. These are the bright star Regulus in the constellation Leo, and the planet Saturn. The entire grouping should fit nicely in the field of view of binoculars so get out whatever you have, dust it off, and pull up a chair. The totality phase of the eclipse will be from 7:00 until 7:52 pm.
By watching the eclipse from start to finish you can get a very good feel for just how far and fast the Moon moves in its orbit around the Earth. When the Sun sets on the evening of the 20th, the Moon will rise due east and quickly move across the southern half of the sky. This motion is due to the rotation of the Earth on its axis. However, the darkening of the Moon as it moves through the shadow of the Earth is due to the orbiting of the Moon around the Earth, something which is slower and thus more subtle. By watching the changing position of the Moon against Regulus and Saturn, you will be able to get a sense how far it moves against the background stars in a short span of time.
01 February 2008
Gorgeous Dawn Sky
Sometimes the stars do in fact align and all is well. OK, perhaps not the stars but the planets, and suddenly they shine in the sky as the clouds and rain in San Francisco have miraculously disappeared just in time. The morning of Friday February 1st is one of those special moments when the brightest objects in the sky line up and make for great viewing. As Venus graces the morning skyline, it is being joined by Jupiter which is rising each morning higher out of the morning glare of sunrise. They pass very near to each other on the morning of the 1st and are about a half degree apart - that's about one full moon's width. But the moon is not far off, a crescent just up and to the right next to the bright star Antares in Scorpio.
The next few weeks will offer the chance to see the change in the lineup, as Jupiter continues to climb each day in the morning sky while Venus stays low on the horizon. That is because Jupiter, being considerably further away from the earth, moves at more the same pace across the sky as the sun, whereas Venus, being much closer, actually is speeding around the Sun and stays lower on the horizon.
The next few weeks will offer the chance to see the change in the lineup, as Jupiter continues to climb each day in the morning sky while Venus stays low on the horizon. That is because Jupiter, being considerably further away from the earth, moves at more the same pace across the sky as the sun, whereas Venus, being much closer, actually is speeding around the Sun and stays lower on the horizon.
14 January 2008
Moon in Action / Being on KFOG
This week the waxing moon journeys across Taurus and Gemini. As it does, it encounters the Pleiades, the small but distinctive cluster of stars in Taurus also known as "the Seven Sisters." On the evening of January 17th, the moon will graze through this region of the sky in what is called an "occultation" of the Pleiades. Occultations are special times when a celestial object is "blocked" from our point of view by another object. The most common are occultations of stars and planets by the moon. When this is being caused by the moon, it affords anyone with binoculars or a telescope to easily observe the motion of the moon against the background stars as the moon makes its monthly journey around the earth. On the evening of January 17th as the moon variously covers and uncovers stars in the Pleiades, you will be able to sense that motion. Over the course of approximately three hours the moon will move across the Pleiades.
Two days later, the nearly full moon will pass very close to Mars but will not occult the planet from our vantage point in San Francisco. Observers much further north (in Canada) will in fact see the moon completely cover Mars. Because Mars is bright and fairly close to earth right now, the sight of it so close to the full moon will be quite beautiful. Take a few moments on the evening of January 19th to enjoy this spectacle. I observed a similar lineup of moon and Mars in December during the previous full moon two days before Christmas.
Earlier this month I was a guest on the KFOG radio morning show (104.5 FM in San Francisco). KFOG features the best morning show program in the San Francisco Bay Area (in my humble opinion) because the DJ and his crew talk about relevant subjects and current news items in an intelligent way. I thought it would be interesting for the KFOG listeners, affectionately known as Fogheads, to hear about astronomy and I asked to be a guest on the program. Morning show producer Greg McQuaid welcomed me to join and on January 8th I was a guest. The program went well and the Fogheads asked interesting questions. I am invited to return to the morning show in March and will post an update to the blog when the date is confirmed.
There were many more questions from Fogheads that we did not get to answer during the show, so I will post them to this blog from time to time.
Two days later, the nearly full moon will pass very close to Mars but will not occult the planet from our vantage point in San Francisco. Observers much further north (in Canada) will in fact see the moon completely cover Mars. Because Mars is bright and fairly close to earth right now, the sight of it so close to the full moon will be quite beautiful. Take a few moments on the evening of January 19th to enjoy this spectacle. I observed a similar lineup of moon and Mars in December during the previous full moon two days before Christmas.
Earlier this month I was a guest on the KFOG radio morning show (104.5 FM in San Francisco). KFOG features the best morning show program in the San Francisco Bay Area (in my humble opinion) because the DJ and his crew talk about relevant subjects and current news items in an intelligent way. I thought it would be interesting for the KFOG listeners, affectionately known as Fogheads, to hear about astronomy and I asked to be a guest on the program. Morning show producer Greg McQuaid welcomed me to join and on January 8th I was a guest. The program went well and the Fogheads asked interesting questions. I am invited to return to the morning show in March and will post an update to the blog when the date is confirmed.
There were many more questions from Fogheads that we did not get to answer during the show, so I will post them to this blog from time to time.
08 January 2008
05 January 2008
Astronomy Resources
The web is filled with excellent astronomy resources. Here are some of the sites I frequent for different kinds of information.
Visit daily: Astronomy Picture of the Day
Photos and Images: NASA has a wealth of photos from all of its missions.
Eclipses: the authority on all things related to eclipses: Fred Espenak's NASA site
Good for listening: StarDate is a quick daily dose of very general astronomy topics. Astronomy Cast is an excellent weekly podcast for those looking for deeper insights.
General Resources: Sky and Telescope Magazine or Astronomy Magazine are very good portals covering many aspects of astronomy for the amateur and hobbyist. Spaceweather.com has very useful up-to-date information and news about the goings-on in space.
Sun and Sky Conditions: The Clear Sky Clock provides a wealth of detail on sky conditions with details on transparency, darkness, seeing, and so on. The US Naval Observatory provides exact sunrise and sunset times anywhere on the globe.
Clubs: San Francisco Amateur Astronomers have a range of activities and resources if you want to get more involved in astronomy.
Visit daily: Astronomy Picture of the Day
Photos and Images: NASA has a wealth of photos from all of its missions.
Eclipses: the authority on all things related to eclipses: Fred Espenak's NASA site
Good for listening: StarDate is a quick daily dose of very general astronomy topics. Astronomy Cast is an excellent weekly podcast for those looking for deeper insights.
General Resources: Sky and Telescope Magazine or Astronomy Magazine are very good portals covering many aspects of astronomy for the amateur and hobbyist. Spaceweather.com has very useful up-to-date information and news about the goings-on in space.
Sun and Sky Conditions: The Clear Sky Clock provides a wealth of detail on sky conditions with details on transparency, darkness, seeing, and so on. The US Naval Observatory provides exact sunrise and sunset times anywhere on the globe.
Clubs: San Francisco Amateur Astronomers have a range of activities and resources if you want to get more involved in astronomy.
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