Go Stargazing! January Edition

Jupiter, now in the west at dusk, dominates this month’s evening skies.  It outshines all stars in the sky, so it’s easy to find.  Face west southwest at dusk and look for the brightest thing there.

Venus remains a dazzling morning star.  Face southeast at dawn and you can’t miss it.

Saturn is in the south southwest at dawn, above the much brighter Venus.

Mars is still lost in the sun’s glare; it will remain invisible to us all winter as Earth passes around the far side of the sun from it.

The Great Square of Pegasus sets in the west, while brilliant winter stars shine in the south.  Orion, the Hunter, is almost due south.  His two dogs, represented by Sirius and Procyon, are to his left.  Above Orion is Taurus, the Bull with Aldebaran as its eye. Gemini, the Twins, are to Orion’s upper left.

Moon Phases in January 2011:

New Moon                              January 4, 3:03 a.m

1st Quarter                             January 12, 5:32 a.m

Full Moon                               January 19, 3:22 a.m.

Last Quarter                          January 26, 6:58 p.m.

The new moon of Tuesday, January 4, partially blocks the sun, causing a partial solar eclipse.  This event occurs during our nighttime, however; the eclipse is visible only in Europe, western Asia, and northern Africa.

Eclipsed? Not totally.
Creative Commons License photo credit: James Jordan

At about 1 p.m. on Monday, January 3, the Earth is as close to the sun as it will get all year. In other words, Earth is at perihelion. Earth’s orbit is not a perfect circle but an ellipse, so its distance from the sun varies between about 147 million kilometers in January and 152 million kilometers in July. This variation is too small to affect our seasons; the effect of Earth’s 23.5 degree title on its axis dominates it. That’s why it’s colder now than in July. The actual moment of perihelion varies each year between late on January 1 and early on January 5.

At Houston’s latitude, the latest sunrise of the year occurs Friday, January 10.  Of course, days have been lengthening since the solstice, which makes sunset later and sunrise earlier.  However, Earth is still going a little faster than average on its orbit, since it is just past perihelion (its closest approach to the sun).  This causes sunrise, local noon, and sunset to occur slightly later each day.  Until mid-January, we are still close enough to perihelion that the second effect actually predominates.  As a result, sunset gets a little later during early January even while the days are getting longer.

Go Stargazing! April Edition

Saturn, up all night long last month, can now be found in the east southeast at dusk.  We are seeing its rings a little more edge on than earlier in the year, an effect that gets even more pronounced next month.

Venus keeps getting higher in the evening sky during the month of April.  Face west at dusk and look for a point of light that outshines everything in the sky. As April opens, Venus has a companion; the elusive Mercury is to its lower right.  Normally too close to the sun to appear in our night sky, Mercury has come from behind the sun and appears far enough to its side that we can still see it just after sunset. Mercury’s greatest elongation (apparent distance from the sun) occurs on April 8.  After that date, we see Mercury return towards the sun’s glare.

Mars is very high in the evening sky, although not as bright as it was in winter.  Since Jan. 29, the Earth has been pulling ahead of Mars on its faster orbit.  As a result, Mars gets slightly dimmer each night for the rest of 2010.  However, during April, Mars remains brighter than average and thus remains easy to see.  Look high in the south at dusk for a reddish point of light.

Jupiter is low in the southeast at dawn this month.  Look for it low in twilight as day begins to break.  It will be higher in the southeast by the end of the month.

Johannes Hevelius drew the Orion constellation
in Uranographia, his celestial catalogue in 1690

Now that the winter is over, the winter stars have shifted to the west.  Dazzling Orion is high in the southwest.  His belt points right to Aldebaran, the eye of Taurus, the Bull.  The Dog Stars Sirius and Procyon are to Orion’s left.  Sirius is the brightest star we ever see at night.  Gemini, the Twins, are to Orion’s upper left.  Look for two stars of equal brightness less than 5 degrees (three fingers at arms’ length) apart.  These are Castor and Pollux, marking the twins’ heads.  High in the northwest is Capella, the sixth brightest star ever seen at night.

Meanwhile, the spring stars are high in the east.  A distinct backwards question mark shape outlines the mane and forepaws of Leo, the Lion.  Three stars forming a right triangle rise underneath; they mark Leo’s hindquarters.  The Big Dipper is high in the northeast at dusk. If you have a clear eastern horizon, you can extend the curve of its handle to ‘arc to Arcturus’ and then ‘speed on to Spica.’  These stars are along the eastern horizon by dusk tonight.

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

The large contrast between the bright winter stars in the west at nightfall and the dimmer spring stars in the east arises because of the shape of our Milky Way. The Galaxy is a barred spiral much thinner than it is wide across. Thus, most stars are near the plane of the galaxy.  Orion, Taurus, Gemini, and the Dogs are near the galactic plane, while Arcturus and the stars of Leo and Virgo are far above it.



Moon Phases in April 2010:

Last Quarter                  April 6, 4:37 a.m.

New Moon                      April 14, 7:30 a.m.

1st Quarter                     April 21, 1:19 p.m.

Full Moon                       April 28, 7:18 p.m.

Go Stargazing! March Edition

Saturn is up all night long by month’s end.  On Mar. 21, Earth passes between the sun and Saturn.  This alignment is called opposition because it puts Saturn and the sun on opposite sides of the Earth.  As a result, Saturn rises at dusk and sets at dawn on this date.  Look for Saturn to rise due east around 8:00 p.m. tonight. It will rise just a little bit earlier each night.

Venus enters the evening sky by the end of March.  As March opens, Venus is still setting during twilight, making it hard to notice at dusk.  By the end of the month, though, Venus has come out from behind the sun far enough for us to notice it clearly.  Face west at dusk and look for a point of light that outshines everything in the sky but the sun and the moon.

Mars has become an evening object.  It is now already up in the east-northeast by dusk.  On Jan. 29, Mars came to opposition as Earth passed between Mars and the sun, putting Mars in our sky all night long.  Earth is now pulling ahead of Mars on its faster orbit.  As a result, Mars is slightly dimmer each night for the rest of 2010.  However, during March, Mars remains brighter than average, and thus remains easy to see.  Look high in the southeast as dusk (due south by the end of the month) for a reddish point of light sort of in line with the two Dog Stars 

Jupiter is mostly out of sight this month.  Viewers with a very clear east-southeast horizon may notice Jupiter low in the sky at dawn by the end of March.  

STEAL ME FOR YOUR DESKTOP!! (The Bokeh Galaxy)
Creative Commons License photo credit: kevindooley

Dazzling Orion is high in the south.  His belt points up to Aldebaran, the eye of Taurus, the Bull.  The Dog Stars Sirius and Procyon are to Orion’s left.  Sirius is the brightest star we ever see at night.  Gemini, the Twins, are to Orion’s upper left.  Look for two stars of equal brightness less than 5 degrees (three fingers at arms’ length) apart.  These are Castor and Pollux, marking the twins’ heads.  High in the northwest is Capella, the sixth brightest star ever seen at night.  At dusk on March evenings, look below Sirius and a bit to its right for Canopus, the second brightest star we ever see at night. This star is in the keel (bottom) of the legendary ship Argo.  Canopus is so far south that most Americans never get to see it.  We, however, are far enough to the south that it barely rises for us, remaining low on the southern horizon.  

Meanwhile, spring stars are rising in the east.  A distinct backwards question mark shape outlines the mane and forepaws of Leo, the Lion.  Three stars forming a right triangle rise underneath; they mark Leo’s hindquarters.  The Big Dipper is once again fully risen at dusk. Later in the evening, you can extend its handle to ‘arc to Arcturus’ and then ‘speed on to Spica’.  These stars will be along the eastern horizon by 9:30 tonight, and even earlier later in the month.

Transit Lune/Saturne du 22 mai 2007
Creative Commons License photo credit:
ComputerHotline

Moon Phases in March 2010:

Last Quarter                  March 7, 9:43 p.m.

New Moon                      March 15, 4:02 p.m.

First Quarter                  March 23, 5:59 a.m. 

Full Moon                        March 29, 9:25 p.m.

At 12:33 p.m. on Saturday, Mar. 20, the sun is directly overhead at the equator.  This, then, is the vernal equinox. On this date, everyone in the world has the same amount of daylight and the same amount of night.  After this date, daytime is longer than night in the Northern Hemisphere, while night is longer than daytime in the Southern Hemisphere. 

Sunday, Mar. 14, is the second Sunday in March.  Accordingly, we spring forward into Daylight Saving Time at 2 a.m. that morning (1:59:59 a.m. is followed by 3:00:00 a.m.).  Don’t forget to set your clocks forward by one hour before going to bed Saturday night!

Go Stargazing! February Edition

Jupiter!
Creative Commons License photo credit: Joshua Bury

Jupiter leaves the evening sky this month.  You can still see it during the next two weeks if you face southwest at dusk and look for the brightest point of light there. Jupiter sets by 7:30 as February opens, so you must look soon after dusk to see it.   However, Jupiter sets earlier and earlier and appears lower and lower to the horizon each February night, and soon disappears into the sun’s glare.  On Tuesday, Feb. 16, observers with a clear view of the horizon during twilight can try to see a very close conjunction of Jupiter and Venus, which is slowly moving out of the sun’s glare.  By the end of the month, Earth and Jupiter are on opposite sides of the Sun and Jupiter is therefore invisible to us.

Mars has become an evening object.  It is now already up in the east-northeast by dusk.  Mars already outshines all stars in the night sky except the very brightest (Sirius), and will continue to brighten throughout February.  On Jan. 29, Mars came to opposition as Earth passed between Mars and the sun, putting Mars in our sky all night long.  Earth now starts to pull ahead of Mars on its faster orbit.  As a result, Mars is slightly dimmer each night for the rest of 2010.  However, during February, Mars remains about as bright as the brightest stars, and thus remains easy to see.

Saturn is now high in the southwest at dawn.  Although not as bright as Mars this month, Saturn is brightening as it approaches its own opposition in March.

Joseph Nollekens (1737 - 1823) Castor and Pollux front (V&A 2007)
Castor and Pollux
Creative Commons License photo credit: ketrin1407

Dazzling Orion is high in the south, reminding us that winter is here.  His belt points up to Aldebaran, the eye of Taurus, the Bull.  The Dog Stars, Sirius and Procyon, are below Orion in the east.  Sirius is the brightest star we ever see at night.  Gemini, the Twins, are to Orion’s left as he rises (and to his upper left once they appear to the south).  Look for two stars of equal brightness less than 5 degrees (three fingers at arms’ length) apart.  These are Castor and Pollux, marking the twins’ heads.  High in the northeast is Capella, the sixth brightest star ever seen at night.  On February and March evenings, look below Sirius and a bit to its right for Canopus, the second brightest star we ever see at night. This star is in the keel (bottom) of the legendary ship Argo.  Canopus is so far south that most Americans never get to see it.  We, however, are far enough to the south that it barely rises for us, remaining low on the southern horizon.

Moon Phases in February 2010:

Last Quarter                  February 5, 5:50 pm
New Moon                      February 13, 8:52 pm
1st Quarter                     February 21, 6:42 pm 
Full Moon                       February 28, 10:37 am

The new moon of Feb. 13 is the second new moon after the winter solstice.  Accordingly, it marks the Chinese New Year, beginning the Year of the Tiger.  (Correct for the time zone difference, and you’ll see that the date is February 14 in China).

Chinese New Year - Dragon
Creative Commons License photo credit: ajagendorf25