Seeing Stars with James Wooten: Exciting Rare Mercury Transit Next Monday!

May Starmap

Jupiter is now high in the south at dusk. It outshines all stars we ever see at night, so you can’t miss it.

Mars and Saturn become late evening objects this month. Tonight, May 2, Mars rises in the southeast at 9:48 p.m. while Saturn comes up soon afterwards, at 10:24 p.m. By May 15, though, both planets rise during twilight, and on Memorial Day both are in the southeastern sky as soon as it gets dark. Mars and Saturn are still above the distinctive pattern of Scorpius, the scorpion. As you watch them rise, Mars is to the upper right and is much brighter.

In fact, this month, Mars outshines all of the stars and even rivals Jupiter in brightness! That’s because on May 22, Earth passes between the Sun and Mars. That alignment is called ‘opposition’ because it puts Mars opposite the Sun in our sky, making Mars visible literally all night long. It also makes Mars much brighter than normal in the sky, since we’re as close to it as we’ll ever get until Earth overtakes Mars again in 2018. Saturn comes to opposition June 3.

Venus is lost in the Sun’s glare and out of sight all month.

A swath of brilliant winter stars sets in the west at dusk. Orion, the Hunter, is still visible in the west as May begins. His two dogs, represented by Sirius and Procyon, are to his left.  Gemini, the Twins, are above Orion. The Big Dipper is above the North Star, with its handle pointing to the right. From that handle, you can ‘arc to Arcturus’ and then ‘speed on to Spica’; those stars are high in the east and in the south, respectively, at dusk. Leo, the Lion, passes almost overhead at dusk.

As Orion and his dogs set, look for Antares, the brightest star in Scorpius, the Scorpion, to rise in the southeast. Saturn and Mars will rise with the Scorpion’s head, above Antares. At the same time, Vega, brightest star of the Summer Triangle, appears low in the northeast. These stars remind us that summer is on the way.

Moon Phases

Moon Phases in May 2016:

New: May 6, 2:30 p.m.

First Quarter: May 13, 12:02 p.m.

Full: May 21, 4:14 p.m.

Last Quarter: May 29, 7:12 a.m.

Mercury Transit:

On Monday, May 9, 2016, Mercury overtakes Earth on its much faster orbit. This time, though, when Mercury passes Earth, the alignment is almost exact, such that Mercury appears in silhouette against the sun’s disk. This event is known as a transit of Mercury. Keep in mind that the planets are almost, but not exactly, in the same plane. Indeed, Mercury’s orbit is the most inclined — tilted up to 7 degrees from Earth’s orbital plane. That’s why Mercury does not usually transit the sun when it overtakes Earth. Monday’s event is therefore rare and special, occurring only 14 times in the 21st century (the next one occurs Nov. 11, 2019).

Transit_of_Mercury_May_9_2016_path_across_sun

Thus, weather permitting, the Houston Museum of Natural Science has arranged for volunteers from local astronomy clubs to set up solar telescopes outside our museum’s main entrance, near the sundial, to show you the transit. Mercury, already in the sun’s disk by sunrise in Houston, takes until 1:42 p.m. to cross to the other side of the sun’s disk. If skies cooperate, we’ll observe the transit from 10 a.m. until 1:42 p.m. on Monday, May 9. If there are sunspots on the sun’s disk while Mercury is there, Mercury will stand out because its disk is fully round and because Mercury moves noticeably across the sun’s disk during the hours we’re watching.

We will observe the sun (and Mercury in silhouette) through telescopes with filters especially designed to filter the sun safely, and by projecting the sun’s image onto a screen. These are the only two ways to observe the Sun safely. Please do not try to observe the sun directly or through an unfiltered telescope, as this will lead to permanent eye damage or blindness. Our common sense tells us this because we always avert our eyes when we accidentally turn towards the Sun. When something cool happens on the sun, some of us try to override our common sense, and there is no reason to do so. Come observe safely with us.

On most clear Saturday nights at the George Observatory, you can hear me do live star tours on the observation deck with a green laser pointer. As of now, George is closed which Brazos Bend State Park dries out from last month’s floods, and is scheduled to reopen May 10. If you’re there, listen for my announcement. 

Seeing Stars with James Wooten: Last Chance for Winter Constellations in April

Starmap April

Jupiter is now high in the east-southeast at dusk. It outshines all stars we ever see at night, so you can’t miss it. 

Mercury is visible just after sunset this month. Face west at twilight, and look low in the sky over the point where the sun sets. Mercury isn’t as brilliant as Venus or Jupiter, but it easily outshines the stars near it in the sky, so it’s not too hard to find. 

Mars is in the south-southwest at dawn. Noticeably reddish in tint, Mars continues to brighten each day until its opposition in May. It has now surpassed nearby Saturn in brightness.

Saturn is in the south-southwest at dawn, above the distinctive pattern of Scorpius, the scorpion. Mars remains close to Saturn this month.

Venus is becoming lost in the sun’s glare. Already, it doesn’t rise until deep into morning twilight, and Venus continues to approach the sun all month.

April is the last month to see the set of brilliant winter stars which now fill the western evening sky. Dazzling Orion is in the southwest at dusk. His three-starred belt is halfway between reddish Betelgeuse and bluish Rigel. Orion’s belt points rightward to Aldebaran in Taurus the Bull. To Orion’s upper left are the twin stars Castor and Pollux, marking the heads of Gemini, the Twins. You can find Sirius, the brightest star we ever see at night, by drawing a line from Orion’s belt towards the left. Forming a triangle with Sirius and Betelgeuse is Procyon, the Little Dog Star. 

Joining the winter stars are stars of spring rising in the east. Look for Leo, the Lion at dusk. Ursa Major, the Great Bear, which includes the Big Dipper, is high above the North Star on spring evenings. Extend the Big Dipper’s handle to ‘Arc to Arcturus’ and then ‘speed on to Spica’. There are fewer bright stars in this direction because of where the plane of our galaxy is in the sky. The area of sky between Gemini and Taurus and over Orion’s head is the galactic anticenter, which means that we face directly away from the galactic center when we look in this direction. Those bright winter stars setting in the west are the stars in our galactic arm, right behind the sun. On the other hand, if you look at the sky between Ursa Major, Leo, Virgo, and Bootes, you’re looking straight up out of the galactic plane, towards the galactic pole. There are fewer stars in this direction.

Moon Phases

Moon Phases in April 2016:

New: April 7, 6:24 a.m.

First Quarter: April 13, 10:59 p.m.

Full: April 22, 12:24 a.m.

Last Quarter: April 29 10:29 p.m.

On most clear Saturday nights at the George Observatory, you can hear me do live star tours on the observation deck with a green laser pointer. If you’re there, listen for my announcement. 

Clear Skies!

Seeing Stars with James Wooten: Five planets at dawn, leap day this February!

Star Map

Jupiter is now a late evening object, rising in the east. It rises by 9 p.m. on Feb. 1, and by Feb. 29 it comes up just before 7 p.m., which is during evening twilight. Jupiter comes to opposition on March 8, which is when Earth aligns with Jupiter and the Sun. That is why Jupiter is up all night long in late February and early March.

As dawn approaches this month, Jupiter will still be visible, this time high in the west.  Meanwhile, the four other visible planets will have risen as well. That’s right, February 2016  features all five naked-eye planets at dawn!

Venus is in the southeast at dawn. You can’t miss it, as Venus outshines all the stars we see at night, and in fact outshines everything but the Sun and the Moon.

Mars is in the south at dawn. Noticeably reddish in tint, Mars continues to brighten each day until its opposition next spring. 

Saturn is in the south southeast at dawn, above the distinctive pattern of Scorpius, the scorpion. Mars slowly approaches Saturn this month.

Mercury is the biggest challenge to find. This month, though, Mercury is very close to Venus and to its left. Thus, once you find Venus, the brightest dot to its left is Mercury. 

Mercury is the first planet to leave the gathering as it heads back towards the Sun late this month. The cutoff date of Feb. 20 is somewhat arbitrary, though. It’s better to watch the sky and, using Venus as your guide, see for yourself when is the last day you can still see Mercury before losing it the Sun’s glare. The next to leave is Jupiter, which shifts into the evening sky after opposition. 

Taurus, the Bull, is high in the south. Look for the Pleiades star cluster above reddish Aldebaran. Dazzling Orion, the Hunter, takes center stage on winter evenings.  Surrounding Orion are the brilliant stars of winter. Orion’s belt points down to Sirius, the Dog Star, which outshines all other stars we ever see at night. The Little Dog Star, Procyon, rises with Sirius and is level with Orion’s shoulder as they swing towards the south. To the upper left of Orion’s shoulder is Gemini, the Twins.

Under Sirius and low to the southern horizon this month is a star that most Americans never get to see—Canopus. Representing the bottom (keel) of the legendary ship Argo, Canopus is the second brightest star ever visible at night. Thus, it is clearly noticeable along the southern horizon on February and March evenings. However, you must be south of 37 degrees north to see Canopus rise. (This is the line that divides Utah, Colorado, and Kansas from Arizona, New Mexico, and Oklahoma.)

The sky we see depends on our latitude as well as on the time of night and time of year.  From any given location in our hemisphere, there is an area of the sky around the North Star in which stars never set (circumpolar stars), and an equivalent area around the South Celestial Pole in which stars never rise. The closer you are to the pole, the larger these areas are. The closer you get to the equator, the fewer circumpolar stars there are, but there are also fewer stars that never rise for you. At the equator, no stars are either circumpolar or never visible; all of them rise and set as Earth turns. 

That’s why, down here in south Texas, the Big Dipper sets for a while although it’s always up for most Americans. On the other hand, Canopus, too far south to rise for most Americans, rises for us.

Moon Phases

Moon Phases in February 2016:

Last Quarter: Jan. 31, 9:28 p.m.

New: Feb. 8, 8:39 a.m.

First Quarter: Feb. 15, 1:46 a.m.

Full: Feb. 22, 12:20 p.m.

(February is so short that last quarter Moons occur on Jan. 31 and March 1, but not in February). 

The New Moon of Feb. 8 is the second New Moon after the winter solstice. Accordingly, it marks Chinese New Year. Welcome to the Year of the Monkey!

Monday, Feb. 29, is leap day. This day exists because our normal year of 365 days is too short. The true length of one Earth orbit around the Sun is 365 days and almost 6 hours.  No one wants to begin a year in the middle of a day, however. Therefore, we let the error add up over four years, until it becomes 24 hours, or one whole day, then add that day back to the calendar. Thus, February 29 occurs every four years. 

Almost 6 hours?  Well, alright, the difference between our orbit and our year is actually 5 hours, 49 minutes, and 16 seconds. That makes our system a very slight overcorrection.  To prevent that from adding up, we’ll skip leap day in 2100, 2200, and 2300. 

On most clear Saturday nights at the George Observatory, you can hear me do live star tours on the observation deck with a green laser pointer. If you’re there, listen for my announcement. 

Clear Skies!

Geminid Meteor Shower offers a brilliant weekend at the George!

The annual Geminid Meteor Shower peaks this weekend, and we’ve got some tips for stargazers hoping to catch it.

The Geminids are unique among meteor showers because they are associated not with a comet but with an asteroid, 3200 Phaethon. Comet orbits are so oblong that that they cross Earth’s orbit almost at right angles. For most meteor showers, then, Earth doesn’t rotate us to face the debris field until after midnight. The less oblong orbit of an asteroid meets Earth’s orbit at a shallower angle. Thus, we rotate to face into the debris field earlier in the night, even before midnight. With Geminids, then, we see significant activity as early as 9 or 10 p.m., although the shower will likely peak just before dawn.

geminid

The Geminid meteor shower is one of the brightest, most active, and most remarkable annual stellar events.

A new moon falls on Thursday, Dec. 10 this year. That makes Sunday night’s moon a slender crescent which sets by 8 p.m. This should guarantee us nice, dark night for viewing once the shower gets going. The Geminid Meteor shower peaks every December and is one of the best, most reliable showers, producing an average of 100 meteors per hour.

They’re called the Geminids, by the way, because we see them seem to ‘radiate’ from an area of sky near Castor, a bright star in Gemini, the Twins. In December, Gemini is still rising at dusk, but it has cleared the horizon by 8 p.m., passes high overhead at about 1 a.m., and is in the west by dawn. Remember, though, that not all meteors will be in Gemini! They just seem to radiate from that direction, which means that wherever they appear, the streak will seem to move away from Gemini.

geminids-2014

Therefore, it’s best to lie on your back so you can observe as much of the sky as possible at once. Remember to have patience, as the 100 meteors per hour is about one or two per minute on average. One minute can be a long time if you waiting for something to happen.

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Weather permitting, telescopes, including the Gueymard Research Telescope, will be available for public use at the George Observatory until 10 p.m. during the Geminid Meteor Shower event.

As with all showers, the Geminid Meteor Shower will be best viewed away from city light pollution, weather permitting. The George Observatory will be open Sunday night until midnight for observation. For directions to The George, located just an hour southwest of Houston, click here. Entry to Brazos Bend State Park is $7 per person; free for kids under 12. You don’t need any special equipment for viewing, just a chair, blankets and maybe some hot apple cider.