One of my favorite summertime celestial treats is the “Summer Triangle”. While the Summer Triangle can be seen from late spring through late fall, its most glorious season is summer while high overhead.

The Triangle is not a constellation but rather the three brightest stars in three of the most prominent summer constellations. The stellar members of our Summer Triangle are Altair in constellation Aquila, the Eagle; Vega in Lyra, the Harp and Deneb, the brightest star in Cygnus, the Swan.

You’ll find Cygnus, Lyra, Aquila and our Summer Triangle high above the eastern horizon as darkness falls in late August and early September. If you venture out around 11 pm look directly overhead (astronomers call this zenith) and see if you can spot our illustrious trio.

Chart courtesy Smoky Mountain Astronomical Society. Click to enlarge

Look carefully at the charts. If you’re out observing before midnight and facing east Vega will be on “top” of the triangle, Deneb to your left and Altair the right.

Altair is the nearest of the trio at a distance of 17 light years. When you look at Altair you’re seeing photons (light) that left the star 17 years ago. It’s about one and a half times the size of our Sun and 10 times brighter. Altair is one of the Eagle’s “head” stars, or at least its portrayed that way in the star charts. I have another vision of the Eagle which I’ll share in a moment.

Vega is the next closest at 24 light years distant. When you see it tonight you’re seeing it as it appeared 24 years ago! Lyra, the Harp is a small parallelagram shaped constellation. If you’re fortunate enough to be doing your stargazing at a relatively dark location and have a telescope look for M57, the Ring Nebula, at the base of the Harp opposite Vega. M57 is a very faint “smoke ring” remnant of a super nova. By the way Vega is the star Jodi Foster “beamed” to in the movie “Contact”. It is about twice the diameter of our Sun and 50 times brighter. Chart prepared using Stellarium freeware. Click to enlarge chart

The third star in our Summer Triangle, Deneb, is spectacular by all comparisons. Deneb means “tail” in Arabic and the star marks the tail of the beautiful stellar swan, Cygnus. I’ve also found varying estimates of Deneb’s distance from our little corner of the galaxy.

 In his 1952 book “The Stars: A New Way to See Them” author H.A. Rey placed Deneb at a distance of 50 light years. Other star charts and books published in the past decade list Deneb’s distance at 3,200 light years. More recent charts and data place the star at 1,500 light years distance. Regardless of Deneb’s distance, its size and brilliance are astonishing. Deneb is thought to be 115 times larger and 55,000 times brighter than our Sun! If it were as near as Vega or Altair it would be the brightest star in the sky, bright enough to cast a shadow similar to the first quarter Moon and would likely be visible during daylight!

As mentioned earlier Deneb marks the tail of Cygnus, the Swan. The Swan’s wingspan and body are also known as the “Northern Cross”. Albireo, the Swan’s “beak” is a beautiful blue/orange double star. Use the chart and try to define the shape of the Swan.

My vision of the Eagle varies from the way he is portrayed in the star charts. Most show the constellation with Altair and the star Tarazed as the Eagle’s head and our celestial Accipitridae flying toward the Swan. I see the Eagle winging its way south and west flying in formation toward the heart of the Milky Way with the Swan.

As promised here is the last video episode “Star Hustler” Jack Horkheimer produced and its all about celebrating the Summer Triangle.

Clear skies! Mark, the Stargeezer

If you’ve been wondering about the bright “star” rising to the east these late evenings or to the southwest before dawn, its not a star, its Jupiter. Tonight (August 26/27) the waning gibbous Moon will appear about 6 degrees NNW (above and slightly right of) Jupiter.

The chart to the left shows a view of the sky to the Southeast at midnight, Thursday, August 26th. Click image to enlarge

Remember, with your arm fully extended your fist will subtend about 10 degrees of sky. The Moon and Jupiter will appear about “half a fist” apart. The pair will rise about 10:30 pm and be visible in the sky until dawn.

Another fun observing exercise is watching the Moon’s position as it glides eastward each night. Jupiter makes a good reference point. From night to night through the weekend take a look each night as the Moon appears further east of the planet. Bear in mind that the Moon rises later each night, therefore by Sunday night it will be rising after midnight. Observing Jupiter with binoculars or a telescope is fascinating. For more on observing Jupiter contact me.

Next: The stars of the Summer Triangle.

The Perseid meteors are coming! Many consider the Perseids to be the best shower of the year. Mild summer weather and occasional hourly rates exceeding 100 make observing the Perseids a delight. Perseids are bright and fast. Meteors are tiny bits of dust and cosmic debris. Most are the size of grains of sand.

We encounter the dust trail of comet Swift Tuttle each year from late July through mid August. It is these flecks of dust and grains of sand which are responsible for the Perseid shower. The debris from comet Swift Tuttle is a dust trial left on visits to the inner solar system in 441, 1479 and 1862. This will be a good year for the Perseids because the Moon will set shortly after sunset. Lunar glare will not be a concern. The Moon was new on Tuesday, August 10.

The shower will peak on Wednesday and Thursday nights. The best to watch is Thursday night between 10pm and dawn local time Friday morning. One prediction expects a spike in activity at 0045 UT (8:45 pm EDT) Thursday night Friday morning. This spike favors observers in Europe and Scandinavia. Another spike is expected at 1202 UT Friday morning (8:02 am EDT). This spike will favor observers in the Pacific and Asia. See predictions from Mikhail Maslov here. These predictions call for an overall peak in activity between 18 UT 12 August and 7 UT 13 August.

Here is the forecast from Robert Lunsford of the International Meteor Organization:

The Perseids (PER) are active from a radiant located at 02:03 (031) +55. This position lies in western Perseus, twelve degrees north of the famous second magnitude double star Almach (Gamma Andromedae). The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. Current rates would be two to three per hour at best, as seen from the northern hemisphere. Activity from this source is not visible south of 40 degrees south latitude. With an entry velocity of 61 km/sec., most activity from this radiant would be swift

You won’t need binoculars or a telescope. Find the darkest spot available and make yourself comfortable on a blanket or lawn chair. Watch the darkest part of the sky. Meteor activity is generally greatest in the hours just before dawn because observers in that part of the world are moving through space on Earth’s “front bumper”. Over the past few nights I’ve popped outside between 3 and 6am for a few minutes. Saturday morning I saw two Perseids in 5 minutes.

This shower is called the Perseids because the meteors appear to originate from a radiant in the northern part of the constellation Perseus which rises to the northeast around 12:30 am at this time of year. See the chart. If you’d care to join me and members of the LAS contact me through the link above.

A European group of astronomy enthusiasts will be Tweeting their meteor counts here

IMO Twitter

Other links:

MeteorWatch

Tonight planets Venus, Mars and Saturn will appear clustered within a circle of a diameter of less than 5 degrees. Go out at 9:45 pm or as soon as darkness falls. Look to the west where the sun set.

Start by finding bright, sparkling Venus.  It’s the brightest object in the western sky and it will be the first thing you see. Mars and Saturn are much dimmer than Venus. You’ll find rusty red Mars just above and left of Venus. Yellowish Saturn appears directly right of Mars and above right of Venus.

If you have binoculars use them. Viewing with binoculars will be much more enjoyable if you steady them against a porch post or the corner of a building.

During the next few evenings Venus will continue gliding past the other two in easterly motion. Mars’ eastward motion is apparent also but at a slower rate. Saturn appears essentially stationary. Why are these apparent motions different? Venus is “only” about 40 million miles distant. Currently Mars is about 190 million miles away and Saturn is about 5 times further away at around a 1 billion (with a B!) miles away from you

If you have access to a telescope use it to scan for asteroid Vesta which will be a few degrees above and right of Saturn. Vesta is the 4th brightest asteroid in our solar system

The sky chart was prepared using John Walker’s “Your Sky” online planetarium

For more info see NASA Science News August 5

On Sunday, August 1st a huge solar storm threw millions of tons of plasma toward earth. Storms like this are associated with sunspots and cause Coronal Mass Ejections or CMEs.

 Image: NASA/SDO The Sun in extreme ultraviolet. Taken during July, 2010. Click image for link to Space Weather Prediction Center

If this plasma reaches Earth and interacts with the Geomagnetic field Aurora Borealis (northern lights) and Aurora Australis (southern lights) result. There is a very slight chance these geomagnetic storms will be sufficiently strong for aurorae to be visible at mid-northern latitudes (40 degrees north).

My best guess is that as the next waves of plasma arrive our best chance for seeing aurora will come Wednesday night into Thursday morning. The first wave of plasma from Sunday’s CME arrived at planet Earth Tuesday afternoon. Observers in Denmark at latitude 56 north experienced a nice display Tuesday evening just after dark.

At our latitude here at 38 north we can usually expect visible aurorae about 10-15 days during each 11 year solar cycle. The last solar cycle peak occurred in 2001. In the intervening years there has been an unusally long solar minimum. The Sun may be awakening as Solar Cycle 24 gets under way in earnest.

This forecast was issued by the Space Weather Prediction Center on Tuesday, August 2nd.

Geophysical Activity Forecast: Geomagnetic field activity is expected to be at unsettled to minor storm levels on day 1 (04August) as the current CME passage continues. Activity is forecast to increase to active to minor storm levels with a chance for major storm levels on day 2 (05 August) due to the arrival of the halo-CME observed on 01 August (associated with a large filament disappearance). Activity is expected to decrease to unsettled to
active levels on day 3 (06 August) as CME effects subside.

This is per the SWPC/NOAA forecast issued at 2200 UT August 3rd (6pm local time) the magnitude of the planetary K index must remain at 9 for geomagnetic storms strong enough to produce visible aurorae at mid-latitudes (latitude 40 north). Actually the Kp (planetary K index) has to be at 9 (maximum) for an extended period of time, 18 hours or more and the “POES Auroral Activity level” at 10+ at our magnetic latitude which is 48

The Kp hit 6 at 00UT and the POES AAL is presently (01 UT/9pm local) at 9. So we need a little more soup (at least up two more levels) if there’s any hope of visible aurorae in the midwestern US.

Another factor to be aware of: generally the best auroral displays occur at the longitude just east of the sunset terminator when the plasma bursts from the CMEs arrive. The geomagnetic field tends to funnel the plasma in along the “bow
shock” that follows the sunset terminator.

Such was  the case during the excellent auroral displays of 8 November, 2004. I watched and photographed the display for more than 4 hours. If we do see auroral displays set your camera on a tripod, set the ISO 200 and try exposures of 30-45 seconds.  Click the image to enlarge

 Courtesy NASA/SDO. A full disc image of the Sun showing sunspot region 1092

For a ground based image of the sunspot taken by my friend Don Spain click here

Other resources:

NASA/Solar Dynamics Observatory

Solar Cycle 24

NOAA Space Weather Prediction Center