03/22/11 – Ephemeris – The Big Dipper
Tuesday, March 22nd. The sun will rise at 7:42. It’ll be up for 12 hours and 14 minutes, setting at 7:57. The moon, 3 days past full, will rise at 12:17 tomorrow morning
We are a few days into spring. And while the winter constellation of Orion and its cohorts hold forth in the southwestern sky the Big Dipper is sneaking up in the northeast. At 9 p.m. the Big Dipper is standing on the tip of its handle in the northeastern sky. The stars at the front of the bowl are at the top of Big Dipper now. An imaginary line through them to the lower left will point to Polaris the North Star. The Big Dipper never sets for us, in the north country. It scrapes the northern horizon on autumn evenings, climbs the northeastern sky in the winter, is overhead, in spring, and descends in the northwest in summer. The Big Dipper points to, well it leaks on Leo the Lion. The bright star Arcturus, now rising in the east is found by following the curve of the handle.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Big Dipper points to other stars and constellations. Created using my own LookingUp program. Click on the image to enlarge.
03/21/11 – Ephemeris – The constallation of Hydra
Monday, March 21st. The sun will rise at 7:44. It’ll be up for 12 hours and 11 minutes, setting at 7:55. The moon, 2 days past full, will rise at 11:00 this evening.
In the south and southeastern sky at 10 p.m. can be found the constellation of Hydra the water snake. Unlike the monster of the same name this Hydra has but one head, which is its most distinctive part. At 10 p.m. look to the south. The head of Hydra is located below a line from the constellation Leo the Lion in the southeast and Gemini high in the south. Hydra’s head is a small but distinctive group of 6 stars that make a drooping loop to the right. The rest of Hydra wends its way to the southeastern horizon, and eventually ends near the spring and summer transitional constellation of Libra the scales. Over the next few months Hydra will slither across the southern skies.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Hydra Rising. Created using Stellarium a free planetarium program.
03/18/11 – Ephemeris – Spring is almost here
Ephemeris for Friday, March 18th. The sun will rise at 7:49. It’ll be up for 12 hours and 2 minutes, setting at 7:52. The moon, 1 day before full, will set at 7:16 tomorrow morning.
We are now two days and some hours from the beginning of spring. Spring will arrive at 7:21 p.m. Sunday evening. At that instant the sun will appear to cross the celestial equator, the projection of the earth’s equator on the sky, heading northward. This will give us six months of over 12 hours daylight, culminating on June 21st with over 15 and a half hours of daylight for our listening area. This is the spring or vernal equinox, or to be hemisphericaly correct, the March equinox, because those folks south of the equator will begin autumn. Earth’s seasons are due to the tilt of its axis by 23 and a half degrees. The earth’s axis is nearly fixed in space, but changes its orientation with respect to the sun during our yearly orbit.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
MESSENGER’s in orbit of Mercury!
Just like clockwork! I’m looking for a year of new discoveries about this nearest planet to the sun.
They’re tweeting at http://www.twitter.com/messenger2011.
MESSENGER’s web site is at http://messenger.jhuapl.edu/.
NASA’s MESSENGER page is at http://www.nasa.gov/mission_pages/messenger/main/.
03/17/11 – Ephemeris – MESSENGER spacecraft arrives at Mercury tonight
Ephemeris for St. Patrick’s Day, Thursday, March 17th. The sun will rise at 7:51. It’ll be up for 11 hours and 59 minutes, setting at 7:50. The moon, 2 days before full, will set at 6:48 tomorrow morning.
This evening the MESSENGER Spacecraft will fire its main engine for 15 minutes to put itself in orbit of the planet Mercury. The rocket firing will be at 8:45 this evening. Due to light time delays caused by Mercury being 97 million miles away, we won’t know if the rocket fired until 8:54. While its high gain antenna won’t be pointed at earth, we should get a signal from its omni- directional antenna. We did get a signal from Cassini with its orbital insertion of Saturn in 2004, and that was nearly a billion miles away. I don’t know if NASA TV’s covering the insertion live, but Johns Hopkins Applied Physics Laboratory is having a live webcast. Google “messenger mercury live orbital insertion” It was the first hit. I’ll have the address on the blog. http://messenger.jhuapl.edu/mer_orbit.html
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
03/16/11 – Ephemeris – The bright planets this week
Ephemeris for Wednesday, March 16th. The sun will rise at 7:53. It’ll be up for 11 hours and 56 minutes, setting at 7:49. The moon, 3 days before full, will set at 6:19 tomorrow morning.
It’s Wednesday and time again to take a look at the whereabouts of the bright planets for this week. If the weather cooperates tonight we might get a glimpse of Mercury just above Jupiter low in the west shortly after sunset. Jupiter is the brighter of the two and will set first at 9:07, with Mercury following at 9:18. The best time to view them will be about 8:30 or so. The ringed planet Saturn will rise at 9:17 p.m. in the east southeast and will move due south at 3:05 a.m. In telescopes Saturn shows its rings which are a year and a half along their seven and a half year opening. Venus is brilliant in the morning sky and will rise at 6:27 a.m. in the east southeast. It is really a beautiful sight in the morning twilight.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter-Mercury Conjunction March 16, 2011. Created using Stellaruim.
03/15/11 – Ephemeris – The Lunar Highlands
Ephemeris for Tuesday, March 15th. The sun will rise at 7:55. It’ll be up for 11 hours and 52 minutes, setting at 7:48. The moon, half way from first quarter to full, will set at 5:48 tomorrow morning.
The south part of the moon that can be seen tonight appears brighter than the darker areas that we call seas, that make up the face of the man in the moon. These and other bright areas are called the lunar highlands, and are the most primitive surface of the moon. Here the landscape is saturated with craters. In binoculars the crater Tycho with its rays are just beginning to become prominent. These rays, are thought to be small craterlets caused by the ejecta from the creation of Tycho which occurred perhaps less than 1.1 billion years ago. This makes Tycho a relatively fresh crater in the moon’s nearly 4.5 billion year history. A telescope will reveal more, including the large crater Clavius with its arc of smaller craters within.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
03/14/11 – Ephemeris – The Lunar Jura Mountains
Ephemeris for Monday, March 14th. The sun will rise at 7:57. It’ll be up for 11 hours and 49 minutes, setting at 7:46. The moon, 3 days past first quarter, will set at 5:13 tomorrow morning.
On the moon tonight the gibbous phase and the terminator on the left side of the moon is revealing a large semi circular mountain range called the Jura Mountains that encloses a flat lava plain that looks like a bay in the margin of the Sea of Showers or Mare Imbrium. It is easily visible in binoculars this evening when the sunrise line is crossing the bay. The Jura Mountains will appear as a hook out of the upper left edge of the moon. That’s about the coolest sight that’s visible on the moon that can be seen with binoculars. It’s especially striking if seen in a small telescope. I’ve added these programs to my web log or blog and I can add images to illustrate what I’m talking about, as I did today. The blog’s address is bobmoler.wordpress.com.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Jura Mountains sticking up into morning daylight. Created from the Virtual Moon Atlas.
What we used to know about Mercury
On Thursday evening, 8:45 p.m. March 17 EDT (12:45 a.m. March 18 UTC) the MESSENGER spacecraft will complete the second of NASA’s 2011 planetary trifecta when it will, if all goes well, fire its rocket engine to drop into orbit of the tiny planet Mercury. We’ve had six quick peeks at Mercury so far. Three by the Mariner 10 spacecraft in the 1970’s which looked at the same half of the planet due to Mercury’s unique rotational period. And three more by MESSENGER as it used Mercury to put on the breaks, so it would be going slow enough this time, so it’s rocket engine could drop it into polar orbit of the planet.
At first blush, Mercury looks like the moon. But it’s not. The moon is light, being made up, apparently, of mostly the crustal materials expelled by the earth and another Mars sized body. So it has a relatively small core. Mercury, on the other hand has a large core, and is the second densest planet at 5.43 grams per cubic centimeter. It’s only beaten out by the earth’s 5.52 g/cm3.
We’re going to learn a lot more about Mercury in the next year or so as MESSENGER maps Mercury and the complex interaction between it and the solar wind and magnetic field coming from the sun. Lets look back at the early history of our knowledge of Mercury.
It seems the that early Greeks noticed this elusive planet. They saw it in the morning sometimes, and then they saw it in the evening. At first they thought it was two separate planets that they gave the name Hermes in the evening and Apollo in the morning before they figured out that it was the same planet. The name Mercury we know the planet by today is the Roman equivalent of Hermes.
Another revelation came later. In my youth Mercury was thought to be in tidal lock with the sun, like our moon is to the earth. The rather poor markings found on the planet seen low in the sky at dusk and dawn seemed to bear that out an 88 day rotation to match its 88 day revolution of the sun. It wasn’t until 1965 that radar observations proved that the rotation was 2/3 of 88 days. Every 2 orbits of the sun Mercury rotates 3 times. It seems that the best times to spot Mercury are when it’s in the same part of its orbit, but basically every other return to that spot. Funny thing. The northern hemisphere’s best views of Mercury are for its eastern elongation on spring evenings and western elongations on autumn mornings. In effect we’re viewing Mercury at the same point in its orbit, when it is near its perihelion, when it is closest to the sun. The southern hemispheric observers get to see more favorable views of Mercury, when it’s farthest from the sun.
As we’ve found with all the planets that we’ve gotten a close look at, the generalities of our long-standing ignorance is brushed away. Each planet is its own unique place in the sun.
Taken from my March, 2011 article in the Stellar Sentinel,the newsletter of the Grand Traverse Astronomical Society.
Here is the MESSENGER web page. This mission is run for NASA by the Johns Hopkins Applied Physics Laboratory.
MESSENGER’s First Look at Mercury’s Previously Unseen Side
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
03/11/11 – Ephemeris – Time change again
Friday, March 11th. The sun will rise at 7:02. It’ll be up for 11 hours and 40 minutes, setting at 6:43. The moon, 1 day before first quarter, will set at 1:52 tomorrow morning.
This weekend we go back to Eastern Daylight Saving Time. It may be a boon to most folks, lengthening the evening daylight hours, but around here it makes stargazing difficult by pushing it to the late night hours, especially in June or July. In the old days noon was when the sun was due south in the sky. Railroad schedules were the impetus for the creation of standard time zones, one hour wide. Thanks to politics Michigan is in the eastern time zone, rather than the closer central time zone. We’re about 43 minutes behind Philadelphia, the eastern time meridian. With the imposition of daylight time, it pushes our time meridian 15 degrees of longitude farther east, out into the Atlantic Ocean. So late winter, or spring, forward Sunday morning.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
