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Wednesday, January 31, 2018

A Very Special Tu B'Shevat on January 31, 2018

Tu B'Shevat is known as the "Birthday of the Trees". The name is simply the Hebrew date, the 15th of the month of Shevat, which usually falls in late January or early February. It is the date from which the age of trees is counted for purposes of taking tithes during Temple times or the age of a tree of purposes off eating its fruit. The Torah forbids eating the fruit of a tree until it is 4 years old ("Orlah"). How do we know how old a tree is? We start counting from Tu B'Shevat. That's why it's called the "Birthday of Trees". So, for halachic purposes, a tree planed one day before Tu B'Shevat becomes 1 year old on that day. And another year old on each successive Tu B'Shevat.

This year's TuB'Shevat is extra special because it corresponds to the triple astronomical whamy of a Super-Blue-Blood-Moon. (http://www.astronomyisrael.com/2018/01/super-blue-blood-moon-on-january-31-2018.html) The last time this triple astronomical whamy happened was in 1866. I have no idea when it also last coincided with TuB'Shevat!

But you may be asking yourself why TuB'shevat was picked for the birthday of the trees. Why not another date? And the answer, perhaps not surprisingly, is astronomical. TuB'Shevat is the birthday of the trees because it is a lunar, cross-quarter day. That is, it marks the cross over the middle of the winter quarter. It is half-way between the winter solstice on December 21 and the Spring equinox of March 20. So, half the winter is behind us on this day, and we start looking forward to the coming of spring. And because of this, in the temperate climate of Israel, and other similar climates, the trees beging to set their first flowers. Of course,  the Jewish  calendar being a lunar calendar, this is marked by a lunar event, the full moon of Shevat, which occurs on the 15th of the month, hence the Hebrew letters tet-vav (pronounced tu [two]), whose numerical value is 15. That TuB'shevat falls this year on a Super-Blue-Blood-Moon night is extra special. In fact TuB'shevat ends this year as the supermoon rises over Israel at 5:18PM in Jerusalem. I'm sure those versed in Kabbalh, Zohar, Chasidus, and astrology can tell you exactly what this means in each of those traditions, although I cannot.

Many folk cultures celebrate this cross-quarter day, but in the solar calendar, not the lunar calendar. Do you know what day that is? That's right - it's Groundhog Day (February 2) in the United States. That's the day Puxtahawney Phil emerges from his burrow and lets the world know if winter is over or if there will be another 6 weeks of winter. Why 6 weeks? Because it's half of 12 weeks (or half the winter season behind, half ahead), with just another 6 weeks to go until the Spring Equinox. It's the solar cross quarter day. It derives from the German Candelmas Day, which like many Christian traditions, derives from the Jewish TuB'Shevat.

So, the next time Groundhog Day rolls around, just remember it's the way the rest of the world celebrates TuB'shevat.









Sunday, January 21, 2018

Super Blue Blood Moon of Tu B'Shevat on January 31, 2018

There are alot of things, alot of colors going on here. Let's talk about what you're actually going to see.

In Israel, you are just going to see a full moon. It won't be blue; it won't be a blood red color. But because this full moon occurs when the moon is closest to earth in its orbit it will be bigger and brighter than usual, hence the term "supermoon". A supermoon is only 10%-15% bigger than a regular full moon but up to 30% brighter. Most experts will tell you that you can't see the difference unless you compare a supermoon in the sky to a regular full moon, which of course you can't do. But almost everyone, including me, who sees a supermoon feels it is much bigger than the last full moon they saw. Since a rising full moon looks bigger than usual when it's near the horizon anyway (called the "moon illusion"), most people strive to see a supermoon at moon rise to enhance the effect even more. A full moon always rises at sunset since it is opposite the sun (that's why it's full). In Israel this will be around 5:18pm on Wednesday, January 31, although the actual time will probably be anywhere from 15-30 minutes later since most people don't have a clear flat eastern horizon. Did I mention the moon will rise in the east, like all celestial bodies (you did know that, right?) So, you will need a clear eastern horizon. The full, supermoon will be in the sky all night long, you won't just see it at moon rise, but it will look biggest and brightest at moon rise due to the aforementioned "moon illusion".

Since this is the second full moon of January, it's called a "blue moon", although it never looks blue. The second full moon of a calendar month is called a "blue moon". The first one of this January was on January 1. It has come to refer to any event that occurs rarely, as a second full moon in a month is a relatively rare event. It occurs on average about every 2.72 years.

Now for the "blood moon". A blood moon is the name given to a moon in full eclipse, as it tends to look reddish during totality. This is because the earth acts like a lens and bends sunlight around itself to strike the moon during totality. This small amount of sunlight is filtered through the earth's atmosphere which makes the residual light falling on the moon red, just as the sun itself is reddened by the earth's atmosphere when it sets. You actually do see a reddish or "blood moon" during a total lunar eclipse, but sad to say, you won't in Israel, at least not this time. That's because totality ends before moon rise in Israel. You'll just see a regular, full, supermoon. No colors this time. Sorry. If you want o see the lunar eclipse on Wednesday you'll need to watch online. See the links below.

The best place for most of our readers to see the total lunar eclipse is in the wetern US. See times below. As you can see, the eclipse begins early in the morning on the east coast of the US with the moon setting in the west. It should make for a great photo opportunity! The west coast will get to see the entire even with totality beginning on the west coast at 4:52AM PST, again with the moon setting in the west.

Lunar eclipse times in the US on the morning of January 31, 2018


This is the first triple-header event since 1866: A super, blue blood moon. But wait! It gets better than that because this triple-header coincides this year with Tu B'Shevat, the 15th day of the Hebrew month of Shevat, known as the Birthday of Trees. It's the day that the age of trees is calculated from biblically for purposes of bringing tithes and offerings to the Temple and allowability to eat its fruits. (Fruits of tress are biblically prohibited until they are 4 years old, called "Orlah".) Of course, since it's the 15th of the month, it always coincides with a full moon, but I have no idea (and have not seen anyone else who does) when the last time Tu B'Shevat coincided with a super, blue, blood moon!

Unfortunately, the total lunar eclipse part of this event will not be visible in Israel. The western US will be the best place to see the lunar eclipse. (See above)







http://www.jewishpress.com/news/religion/get-ready-for-wednesdays-once-in-150-years-blood-moon-thats-also-super-moon-blue-moon-lunar-eclipse-and-tu-bshvat/2018/01/28/

NASA webcast of total lunar eclipse:
https://www.nasa.gov/press-release/nasa-television-to-air-live-coverage-of-upcoming-rare-lunar-eclipse

Other sites to watch the lunar eclipse online:
http://www.skyandtelescope.com/astronomy-news/where-to-watch-lunar-eclipse-online/

Meteor Shower Guide for 2018

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

Wednesday, January 3, 2018

Quadrantid's Meteor Shower Peaks January 3-4

The first meteor shower of 2018, the Quadrantid's, peaks on the night of January 3 and the early morning of January 4. The peak is predicted for midnight, Israel Standard Time (IST). Unfortunately a nearly full moon will be in the sky all night and spoil the fun for all but the brightest members of the shower. If you're going to try viewing it just find a dark location and look up. No optical aid is required or even desirable. Just your own two eyes. Forecast rates for the peak are 11 meteors per hour, but on good years I have seen many more. This full moon of January 1-2 was the  full Wolf Moon of winter, a supermoon, occurring during  the moon's closest approach to earth, hence bigger and brighter than a regular full moon. Its light blocks out many meteors during peak shower nights. If you go out, stay warm!



Monday, November 27, 2017

Geminids Meteor Shower 2017 in Israel

Did you get skunked by the Leonids meteor shower last month? Me, too. The run up to the peak was disappointing with only a handful of meteors seen in the early evening up to the day before the peak. The peak occurred on Shabbat when we don't go out, so we don't know what it was like, but the denouement the following days was also sparse with meteors.

You get to try again with the Geminids meteor shower which peaks this year during Chanukah on the night of December 13 and December 14. The actual peak itself is forecast to fall at 8:30AM, Israel Standard Time, on the morning of December 14, in other words in daylight. But the previous night of the 13th and the night of the 14th itself should still be very good, especially since this year there is no bright moon in the sky to interfere with the shower.

The Geminids is one of the most reliable showers of the year with the peak showing up to 120 meteors per hour. It is also a good shower for children since the radiant of the shower, the point in the sky from which the meteors appear to emanate, is already high overhead early on winter evenings, starting around 9:00 to 10:00PM. The radiant is in the constellation Gemini from which the shower, like all meteor showers, takes its name. It is already high up early in the evening. All meteor showers show best after midnight, since then the earth is turning in the direction of its orbit around the sun, increasing the entry velocity of the meteoroid particles into the earth's atmosphere. But it isn't necessary to wait until after midnight to see lots of meteors if the shower performs as expected.

norteast 
The radiant of the Geminids meteor shower lies in the constellation Gemini. It lies near the bright star Castor in Gemini. It isn't necessary to look at teh radiant when observing but since meteors come from all sides of it, one generally sees more meteors when lookin in the direction of the radiant. For the Geminids look northeast before midnight. After that, follow the constellation as it crosses the sky in the early hours of the evening.


Meteors are bright streaks of light made by tiny particles of dust and rock from comets or asteroids. As these particles fall to earth they burn up from the heat of friction in the earth's atmosphere. Most of these particles are the size of a grain of sand, so  obviously we are seeing the brilliant light they make as they incinerate themselves in the earth's dense atmosphere, not the particle itself. So meteors are very much local phenomena, becoming visible some 75-150 miles in the air above us.

Although meteors can be seen every night throughout the year, a meteor shower occurs when the earth passes through the path of an ancient comet or asteroid as it orbits the sun. Then all of the debris of the comet or asteroid falls to earth at roughly the same time, creating showers of particles in our atmosphere. Meteor showers are whole sky phenomena and not only is optical  aid unnecessary it is detrimental to viewing the shower. Your unaided vision gives you the widest field of view of the sky.


A meteor shower occurs when the earth crosses the path of an ancient comet or asteroid and the debris from the object rains down on the earth simultaneously.
The Geminids meteor shower originates not from a comet but from  3200 Phaethon, an asteroid discovered in 1983 that circles the sun every 3.3 years. In fact, recent observations suggest that Phaethon might be a "rock comet" that sheds particles when its surface heats up roughly to 1,300 degrees F (700 degrees C) at each perihelion.

We will have star tours every night of Chanukah, including of course the peak shower nights of December 13 and 14. Come on out and enjoy the show.

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Tuesday, November 14, 2017

Leonids Meteor Shower 2017 in Israel

The Leonids Meteor  Shower peaks on the night of  November 17 and early morning November 18. The night of November 16 should also be good. The peak number of meteors visible at maximum, the Zenith Hourly Rate (ZHR), is 20 meteors per hour. This is when the radiant of the shower, in the constellation Leo, is overhead. The radiant is the point in the sky where the meteors seem to emanate from when a line is drawn back from their path of travel in the sky. These lines converge at a point in the sky called the radiant. For this meteor shower it is located in the constellation Leo, hence the name of the shower.

The ZHR is a predicted maximum. Most meteors during a shower are quite dim, so very few people every see the theoretical maximum for the shower. Even far more intense showers than the Leonids frequently show far fewer numbers than the peak rate, especially if you miss the exact maximum or do not have fully dark skies. There is no moon in the sky during the peak of the Leonids this year, so it should put on a nice show if you can get to a dark location.

Meteors are bits of rock from comets or asteroids that fall to earth at very high speeds and burn up in the earth's atmosphere. Most are quite tiny, about the size of a grain of sand. We see the bright light they make as they burn up from the heat of friction in the earth's atmosphere, not the body itself. The comet from which the Leonids result is Comet Tempel-Tuttle.

We will be having a star tour on Thursday night, November 16, 2017 at 9:30pm. We don't go out on Shabbat and won't be having a star tour on Saturday night November 18. November 19 and 20 should also have some shower activity, but it's difficult to tell how intense it will be. If you'd like to join us that would be delightful.

Status Update:
As of the evening of November 16, nothing major to report. Only a handful of meteors seen on star tours up through and including Thursday night, November 16.


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The radiant of the Leonids meteor shower lies within the boundary of the constellation Leo. You don't have to be looking directly at it to see shower members. They can appear anywhere in the sky. But since Leo will be rising in the East for much of the peak night, it's best to lie on the ground facing eastward. No optical aid is required. Meteor showers are entirely naked eye events. This is the sky at about 5:30am on November 18, 2017. It will look substantially the same the entire week of November 12, except for the moon which will get smaller and smaller and closer and closer to the horizon as the week progresses. It is new on November 19.

If you stay up until dawn the week of November 12 you will be treated to the sight of Venus and Jupiter in conjunction with each other and the waning crescent moon getting ever closer to them morning by morning. This is the sky at 5:31am on November 17, just before dawn, which is when Jupiter, Venus and the moon will start to become visible above the eastern horizon. What a treat  to see them all together with the peak of the Leonids meteor shower!


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