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: Canopus rises in Texas this February

This star map shows the Houston sky at 9 pm CST on February 1, 8 pm CST on February 14, and 7 pm on February 28. To use the map, put the direction you are facing at the bottom. The Great Square of Pegasus sets in the western sky. Taurus, the Bull, is almost overhead. Dazzling Orion, the Hunter is high in the south, with his two dogs behind him. Sirius, the Big Dog Star, is the brightest star we ever see at night. Jupiter, in Gemini, approaches the zenith on February evenings. Look for Canopus, second brightest star ever seen at night, low in the south.

This star map shows the Houston sky at 9 p.m. CST on Feb. 1, 8 p.m. CST on Feb. 14, and 7 p.m. on Feb. 28. To use the map, put the direction you are facing at the bottom. The Great Square of Pegasus sets in the western sky. Taurus, the Bull, is almost overhead. Dazzling Orion, the Hunter is high in the south, with his two dogs behind him. Sirius, the Big Dog Star, is the brightest star we ever see at night. Jupiter, in Gemini, approaches the zenith on February evenings. Look for Canopus, the second brightest star ever seen at night, low in the south.

This month, Venus has entered the morning sky. Look southeast at dawn for the brightest point of light there; only the Sun and Moon outshine Venus. Venus remains a morning star for almost all of 2014.

Jupiter, up literally all night long last month, remains well placed for evening observing all winter and spring. Look for it in the east at dusk and almost overhead later in the evening.

Mars remains in the morning sky. It continues to brighten a bit in the south at dawn.

Saturn remains in the pre-dawn sky. Face south-southeast right before sunup to see it.

In February, the Big Dipper only partly risen at dusk. Its two pointer stars — the stars farthest from the handle which point at the North Star —may be high enough to see over trees and buildings.

Watch the Great Square of Pegasus set in the west at dusk. 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, which contains Jupiter this winter.

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 (second to Sirius). Thus, it is clearly noticeable along the southern horizon on February and March evenings. However, you must be south of 37 degrees north for Canopus to 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. Observers in Canada, for example, have many circumpolar stars, but there is also a large area of stars that they never see. 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, although it’s always up for most Americans. On the other hand, Canopus, too far south to rise for most Americans, rises here.

Moon Phases in February 2014:

1st Quarter: Feb. 6, 1:21 pm
Full: Feb. 14, 5:54 pm
Last Quarter: Feb. 22, 11:16 am
New: Mar. 1, 2:02 am

The Moon takes 27.34 days to orbit Earth; one cycle of Moon phases lasts 29.54 days. At 28 days long, February is the only month shorter than a lunar phase cycle, and thus the only month that can have only three of the four main phases. That’s the case this year, as a New Moon occurred at the end of January and the next comes early on March 1.

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 to you!

Go Stargazing! November Edition

Jupiter is up virtually all night long as November begins.  

Hubble Images Suggest Rogue Asteroid Smacked Jupiter
Creative Commons License photo credit: NASA Goddard Photo and Video

That’s because on Friday night, October 28, Earth passed between the Sun and Jupiter.  In this alignment (‘opposition’) Jupiter rose at dusk and set at dawn.   Face east at dusk and look for the brightest thing there—that’ll be Jupiter.   For the first half of the month, Jupiter does not set until after 5am. 

Venus has begun to emerge from the Sun’s glare.  Look for it low in the southwest in twilight. (Venus is slightly higher in the twilight sky each night this month). This is the beginning of Venus’ apparition as evening star; it gets higher and easier to see for the rest of this year and is spectacular for about the first half of 2012.  For more of a challenge, try to find Mercury under Venus during the first half of the month, as they both set in twilight.

Mars is now high in the east-southeast at dawn.  It now approaches the first magnitude star Regulus in Leo.

Saturn emerges from behind the Sun into the morning sky this month.  Look low in the southeast at dawn, near the star Spica.  (From the Big Dipper’s handle, arc to Arcturus and speed on to Spica).  

The Summer Triangle is high in the west as Sagittarius, the Archer, sets in the southwest.

 As the stars of summer shift to the west, those of autumn fill the sky.   Watch for the Great Square of Pegasus high in the east now and almost overhead at dusk by Thanksgiving.  Pegasus is one of several patterns which depict characters in a single Greek myth (later made into two movies called ‘Clash of the Titans’).  The story begins with Cassiopeia, a queen of Ethiopia who offended the gods by comparing her beauty to that of the Nereids (sea nymphs).  To punish Cassiopeia, the sea god Poseidon sent a giant sea monster, Cetus, to ravage Ethiopian shores.  Cassiopeia’s husband, King Cepheus consulted an oracle and learned that the only way to appease Poseidon was to sacrifice their only daughter, Andromeda, to Cetus.  Andromeda was chained to a rock as everyone waited for Cepheus to come and feed.  However, at just the right moment, the hero Perseus came by.  He had just won great fame by killing Medusa, a woman so hideous that anyone who looked at her turned to stone.  Upon Medusa’s death, the winged horse Pegasus sprang fully formed from her blood, and flew away.  On his way home from that adventure Perseus (flying on winged sandals loaned from Hermes) passed by Ethiopia.  As Cetus rose from the waters to claim his prize, Perseus slew him, saved Andromeda, and married her.  They lived happily ever after. 

Star Cloud Over Saskatchewan.jpg
Creative Commons License photo credit: Space Ritual

In the sky, she is always across the North Star from the Big Dipper. 

In late autumn, as the Big Dipper hugs the horizon and actually sets for us in Houston, Cassiopeia is high in the north, looking like an ‘M’.  In the sky, Cetus swims the very dim region of sky to the south, under Pegasus and Pisces.  Cepheus stands next to his wife in the northern sky, a little to her left as you face north tonight.  Andromeda’s head is Alpheratz, the northeastern star in the Great Square of Pegasus.  From Alpheratz, a curve of stars similar in brightness to Alpheratz and the rest of the Great Square forms her body.  That same curve leads to Perseus in the northeast.
  

Moon Phases in November 2011:
First Quarter November 2, 11:28 am
Full November 10, 2:17 pm
Last Quarter September 20, 8:39 am
Full November 25, 12:10 am

By the way, 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.

Go Stargazing! August Edition

Saturn is the only planet visible to the naked eye at night this August.  Face southwest at dusk and you’ll see Saturn near a star of similar brightness—Spica in Virgo.  Saturn is a bit to the right of Spica as you face southwest.   The ringed planet remains well placed for evening viewing and remains in the night sky until late September 2011.

Hubble Images Suggest Rogue Asteroid Smacked Jupiter
Creative Commons License photo credit: NASA Goddard Photo and Video

Mars and Jupiter are in the pre-dawn sky.  Jupiter, set against a background of very dim stars, dominates the southeastern pre-dawn sky and is due south at dawn by the end of the month.  Mars is dimmer and much lower in the east northeast.  It has fully emerged from the sun’s glare and will brighten slightly each morning. Venus is now out of sight.  Superior conjunction (alignment on the far side of the sun) is on August 16.

The Big Dipper is to the left of the North Star, with its handle pointing up.  From that handle, you can ‘arc to Arcturus’ and then ‘speed on to Spica’; those stars are in the west and southwest at dusk.  Antares, brightest star of Scorpius, the Scorpion, is in the south, with the ‘teapot’ of Sagittarius to its left.  Meanwhile, the Summer Triangle is approaching the zenith.  The stars of summer now dominate the evening sky.  In late evening, you can watch the Great Square of Pegasus rise in the east.

Moon Phases in August 2011:

1st Quarter                     August 6, 6:08 a.m.

Full Moon                       August 13, 1:57 p.m.

Last Quarter                  August 21, 4:56 a.m.

New Moon                      August 28, 10:03 p.m.

The annual Perseid Meteor Shower peaks this year on Saturday morning, August 13.  Unfortunately, the moon (full on the 13th) hides all but the very brightest meteors and thus spoils the show.  If you want to see just how many Perseids can outshine the moonlight, the best hours are from roughly 2 a.m. to dawn.