Around the Sky in 28 Days – Day 10

This evening (Sept 18) the Moon is in the middle of Capricornus and can still be used to find the double-double combo of Alpha and Beta Cap. If you observe a few hours after sunset, look towards the southeast to find Jupiter. Over the next few days watch as the Moon closes in on the “King of Planets”.

Meteor Activity Outlook for September 18-24, 2010

The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook can be found at the American Meteor Society’s site.

September offers longer nights in the northern hemisphere that tend to be less hazy than those experienced in mid-summer. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. Most of the shower activity this month is produced from the Perseus-Aurigid complex active this time of year. These showers rarely produce more than five meteors per hour but still manage to produce most of the shower activity seen this month. Unfortunately the Perseus-Aurigid complex lies too low in the northern sky for southern hemisphere observers to view very well. Video studies have shown that the Southern Taurids are visible as early as September 7th therefore after this date the Antihelion radiant will no longer be listed until the Taurid showers end in December. The Antihelion meteors are still active but their radiant is superimposed upon that of the more numerous Taurids, therefore it is impossible to properly separate these meteors. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Southern Taurid radiant is not too badly placed so observers south can expect to see a little of this activity this month.

During this period the moon reaches its full phase on Thursday September 23rd. At this time the moon will be located opposite the sun and will rise as the sun sets and sets as the sun rises. This weekend the waxing gibbous moon will set during the early morning hours and will allow a short window of opportunity between moonset and morning twilight to view meteor activity under dark conditions. The estimated total hourly rates for evening observers this week is ~2 from the northern hemisphere and ~1 from the southern hemisphere. For morning observers the estimated total hourly rates should be ~16 from the northern hemisphere and ~6 as seen from the southern hemisphere. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning September 18/19. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately five sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fourteen per hour as seen from rural observing sites and three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are slightly reduced due to moonlight.

The following showers are expected to be active this week:

Southern Taurids (STA)

The center of the large Southern Taurid (STA) radiant lies at 00:56 (014) +05. This position lies in southern Pisces, three degrees southeast of the fourth magnitude star Delta Piscium. Since the radiant is so large, any meteor from Pisces, western Cetus, or southwestern Pegasus could be a candidate for this shower. The radiant is best placed near the meridian near 0200 LDT, but activity may be seen all night long. Striking the atmosphere at 29 km/sec., the average Southern Taurid meteor travels slowly through the skies. Rates this week should be near two per hour no matter your location.

Nu Eridanids (NUE)

Many radiants in the region of Eridanus and Orion have been suspected this time of year. Recent studies have verified a radiant active in Eridanus and moving on into Orion from September 3rd through the 24th with maximum activity occurring on the 6th. The Nu Eridanid (NUE) radiant is currently located at 05:00 (075) +06. This position lies in western Orion, five degrees west of the second magnitude star Bellatrix (Gamma Orionis). Old time observers may recall a radiant active in Orion this time of year called the Sigma Orionids. This may be a verification of that activity. The radiant is best placed near 0500 LDT, when it lies highest above the horizon in a dark sky. Rates should less than one per hour this week. With an entry velocity of 68 km/sec., most activity from this radiant would be swift. With the radiant lying close to the celestial equator, these meteors are seen equally well from both hemispheres.

The list below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.

Shower Name                 RA     DEC   Vel     Rates
                                         km/s   NH    SH
STA Southern Taurids      00h 56m  +05    30     2     2
NUE Nu Eridanids          05h 00m  +06    68    <1    <1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a
        dark site
NH - Northern Hemisphere
SH - Southern Hemisphere

Around the Sky in 28 Days – Day 9

For the past 2 days the Moon was traversing Sagittarius, which is a Centaur archer or a teapot depending upon how you see it. For the next few days the Moon will travel among the stars of Capricornus, a half fish half goat but really just looks like a sack of potatoes to those lucky enough to observe from skies dark enough to even see the constellation.

Still for a faint constellation it has a lot going for it and a few faint naked eye (or bright binocular) stars are within a star hoop from the Moon. Alpha and Beta Capricorni make a wide double star just to the upper left of the Moon. A closer examination of both stars find that each is also part of an even closer double pair.

Beta Cap (also called Dabih) is magnitude +3.1 with a much fainter magnitude +6.1 companion. Both are easily seen and separated with a pair of binoculars. The two stars are located at a distance of 330 light-years from us and 21,000 AU from each other. The fainter star, Dabih Minor, is a class B giant with a too-close-to-be-seen F dwarf 30 AU away. The brighter star, Dahib Major, is probably a K giant with a less massive class B companion. There is even evidence of other unseen stars in the system!

Alpha Cap (also called Algedi) consists of 2 stars that can be resolved with the unaided eye. The stars are ~7 arc minutes apart, or ~1/5 the span of the Moon. Though each star is very similar in type (both G), they are not related to each other and it is just coincidence that they appear so close together on the sky. The brighter star is 109 light-years away and is 43 times more luminous than the Sun while the fainter is 6 times further away at 690 light-years and over 900 times more luminous than the Sun. For more, on Alpha Cap see the STARS site, for more on Beta Cap go here.

For tomorrow – Day 10 – I’m actually not sure yet…

Recent Discoveries – Sept 16-17, 2010

The discoveries keep rolling in as the prime discovery surveys continue to enjoy clear skies. The number of new finds should start tailing off soon as the moon approaches Full. When bright moonlight battles faint asteroids, the faint guys usually lose out.

The La Sagra Survey of Spain have reported their 4th comet discovery (all in the past 2 years). Comet La Sagra is a short-period comet with a very asteroidal orbit. In fact, the orbit is smack in the middle of the Main Belt of asteroids making this comet one of the few known Main Belt comets (MBC). This type of comet represents a intermediate state between usually dry asteroids and icy comets. The rapidly increasing number of MBCs means that many asteroids (especially in the mid- to outer-belt) still retain some volatiles that occasionally sublimate to produce cometary activity. At 18-19th magnitude this comet is not expected to get brighter and should fade as it moves away from the Sun and Earth. The comet was discovered with La Sagra’s CCD-equipped 0.45-m (18″) reflector.

2010 RC130 will brighten up to magnitude 15.0 on October 3 as it closes to within ~10 times Lunar Distance.

Asteroid    Type     MOID     a     e     i     H  Mag  Discoverer      MPEC
2010 SJ     Aten    0.050   0.92  0.17  11.5  23.3  19  Catalina        2010-S14
2010 SH     Amor    0.150   1.58  0.31  23.1  23.2  20  Mount Lemmon    2010-S13
2010 SF     Aten    0.014   0.84  0.22   9.4  25.6  18  Catalina        2010-S09
2010 SE     Apollo  0.008   1.05  0.29  20.2  24.1  18  Catalina        2010-S08
2010 SD     Apollo  0.021   1.36  0.40   3.4  24.8  19  Mount Lemmon    2010-S07
2010 SC     Amor    0.025   1.56  0.34   3.3  26.0  20  Mount Lemmon    2010-S06
2010 SB     Amor    0.208   2.90  0.59   7.5  21.9  20  Mount Lemmon    2010-S05
2010 RK135  Amor    0.056   2.46  0.57   4.5  25.6  21  Mount Lemmon    2010-S12
2010 RD130  Apollo  0.024   1.99  0.55   2.2  25.3  21  Mount Lemmon    2010-S04
2010 RC130  Apollo  0.032   2.45  0.58   9.2  21.6  18  LINEAR          2010-S03
2010 RB130  Amor    0.020   2.15  0.52   1.0  24.1  18  Catalina        2010-S02

Comet       Type       T        q     a     e     i  Mag  Period MPEC
P/2010 R2 (La Sagra)
            MBC   2010-06-25  2.62  3.10  0.15  21.4  18   5.46  2010-S11

Type
Aten -  Earth crossing with semi-major axis (avg distance from Sun) < 1 AU
Apollo - Earth crossing with semi-major axis (avg distance from Sun) > 1 AU
Amor - non-Earth crossing with perihelion distance < 1.3 AU
JFC - Jupiter family comet
HFC - Halley family comet
LPC - Long-period comet
MBC - Main belt comet

T - Date of Perihelion
MOID - Minimum Orbit Intercept Distance, minimum distance between asteroid and Earth's orbit
a - semi-major axis, average distance from Sun in AU (1 AU = 93 million miles)
e - eccentricity
i - inclination
H - absolute magnitude
Mag - magnitude at discovery
Discoverer - survey or person who discovered the object
MPEC - Minor Planet Electronic Circular, the discovery announcement

Around the Sky in 28 Days – Day 8

The Moon is now well past First Quarter and is steadily “fattening” as it approaches Full Moon. This evening is the last it will spend among the stars of the summer Milky Way. The chart below shows the southern sky an hour after sunset from the middle of North America.

The Moon is in one of my favorite constellations or, should I say, asterism. The constellations were created over the millenia and every culture had their own take on what the stars looked like. Though many constellations (mostly the fainter ones) were created during the last few hundred years, the brighter ones go back thousands of years. The current shapes and mythologies of the constellations came to us by way of Western Europe via the Arabs via the Romans via the Greeks via the Babylonians via even earlier cultures.

Today the Moon is in the constellation of Sagittarius. To the ancients Sagittarius was an archer Centaur. Centaurs being mythical half man, half horse creatures. But to be honest, I don’t see it. Rather my modern eyes see a simple teapot. In fact, Sagittarius can be both. The all the stars in Sagittarius make up the constellation of Sagittarius while the only the bright stars are needed to see the Teapot. Since the Teapot only includes a few of the stars it is called an asterism. Basically a shape that can be created by only part of a constellation (or parts of multiple constellations). The best known example being the Big Dipper which is made up of only a part of the much larger constellation of Ursa Major. So what do you see?

Centaur archer?

or Teapot?

Tomorrow – Day 9 – you have got to be kidding, after a arrow slinging man-horse now we visit a goat-fish…

Recent Discoveries – Sept 14-15, 2010

2010 RA91 was discovered by Arizona amateur Joe Hobart. Joe used a 0.36-m or 14″ Schmidt-Cassegrain located at his observatory, named Kachina Observatory, in Flagstaff.

I forgot to mention that one of the NEAs presented in ‘Recent Discoveries – Sept 12, 2001‘, 2010 RN80 was also found by an amateur astronomer. Leonid Elenin is an amateur astronomer from Lubertsy City, Russia who routinely observes asteroids, comets and variable stars with a remotely operated telescope in New Mexico. The 0.45-m or 18″ astrograph he used is part of Tzec Maun Observatory.

The weather is once again clear in the American Southwest so the discoveries should continue for a few more days. Then the brightening Moon will shut the surveys down for a few nights.

Asteroid    Type     MOID     a     e     i     H  Mag  Discoverer      MPEC
2010 RM122  Amor    0.043   1.30  0.22   7.2  25.6  21  Mount Lemmon    2010-R114
2010 RA91   Apollo  0.003   2.16  0.35   5.6  23.4  19  J. Hobart       2010-R110

Comet       Type     MOID     q     a     e     i  Mag  Discoverer      MPEC
None

Type
Aten -  Earth crossing with semi-major axis (avg distance from Sun) < 1 AU
Apollo - Earth crossing with semi-major axis (avg distance from Sun) > 1 AU
Amor - non-Earth crossing with perihelion distance < 1.3 AU
JFC - Jupiter family comet
HFC - Halley family comet
LPC - Long-period comet
MBC - Main belt comet
MOID - Minimum Orbit Intercept Distance, minimum distance between asteroid and Earth's orbit
a - semi-major axis, average distance from Sun in AU (1 AU = 93 million miles)
e - eccentricity
i - inclination
H - absolute magnitude
Mag - magnitude at discovery
Discoverer - survey or person who discovered the object
MPEC - Minor Planet Electronic Circular, the discovery announcement

Around the Sky in 28 Days – Day 7

The Moon is now a day past First Quarter or when it appears half Full in the evening sky. It is also getting bright enough that it is hard to see some of the objects nearby. Still this evening the Moon can be used to locate one of the most easily observable star formation regions in the sky.

Called the Lagoon Nebula (also known as NGC 6523, Messier 8, or M8 for short), it is a region of gas and dust stretching across 140×60 light-years at a distance from Earth of 5,200 light-years. All of these numbers are somewhat uncertain so errors up to 10-20% should be assumed. Much of the energy powering the “glow” of the nebula is produced by a cluster of stars which is currently forming from the nebula.

The image below shows the Lagoon in all its glory. Unfortunately this is not what it looks like to any human being. The picture is the result of long exposures on a large telescope. For most of us the Lagoon complex will appear as it does in the finder chart above. To the unaided eye the Lagoon is visible as small faint cloud though that is only true from dark sites. With the Moon so close even dark site observers may not be able to see it without help. oTo really see the Lagoon point a pair of binoculars or a small telescope a few degrees to the right of the Moon. A line of 5th-6th magnitude stars are superimposed on the Lagoon. Within this line of stars you may make out the Lagoon’s associated star cluster sand perhaps the inner core of the nebula itself.

Image of the Lagoon Nebula and associated star cluster. Image taken as part of the GigaGalaxy Zoom project with the MPG/ESO 2.2-m telescope. Credit: ESO.

Tomorrow – Day 8 – Moon in a Teapot.

Around the Sky in 28 Days – Day 6

This evening the Moon drifts between the constellations of Scorpius and Sagittarius. In fact according to modern constellation boundaries, the Moon is located in Ophiuchus which isn’t even one of the traditional 12 zodiac or ecliptic constellations.

If you live someplace dark, the Milky Way is a common sight. Even with the bright Moon in the sky, the Milky Way should be obvious behind the Moon. For those under bright skies, you can use the Moon to point you towards the center of the Milky Way even if you can’t see it. Just look a few degrees to the lower left of the Moon and you’ll be looking roughly at the Milky Way’s center.

The Milky Way is our galaxy. It is a barred spiral galaxy with 200-400 billion stars. Its disk is 100,000 light-years across but only 1,000 or less light-years wide. This is why the Milky Way appears as a narrow band that circles the entire sky.

Tomorrow – Day 7 – Moon near the Lagoon.

Recent Discoveries – Sept 13, 2010

Two days ago 10 NEAs were announced, yesterday saw only a single announcement. The reason… most asteroid surveys are located in the southwest US (Arizona and New Mexico) so a bout of clouds over this part of the country will put a major dent in the number of discoveries. Hopefully the discoveries will ramp back up again tonight.

Yesterday’s sole announcement was larger than most recent discoveries. Nowadays most of the larger NEAs have been found. 2010 RO82 is probably somewhere between 3/4 of a km and 2.5 km across. Chances are an object this big and bright has been seen before though it may not have been recognized as an NEA. Though it is an NEA it really doesn’t come very close to Earth (MOID of 0.163 AU).

Asteroid    Type     MOID     a     e     i     H  Mag  Discoverer      MPEC
2010 RO82   Amor    0.163   2.47  0.60  18.0  16.9  19  Siding Spring   2010-R107

Comet       Type     MOID     q     a     e     i  Mag  Discoverer      MPEC
None

Type
Aten -  Earth crossing with semi-major axis (avg distance from Sun) < 1 AU
Apollo - Earth crossing with semi-major axis (avg distance from Sun) > 1 AU
Amor - non-Earth crossing with perihelion distance < 1.3 AU
JFC - Jupiter family comet
HFC - Halley family comet
LPC - Long-period comet
MBC - Main belt comet
MOID - Minimum Orbit Intercept Distance, minimum distance between asteroid and Earth's orbit
a - semi-major axis, average distance from Sun in AU (1 AU = 93 million miles)
e - eccentricity
i - inclination
H - absolute magnitude
Mag - magnitude at discovery
Discoverer - survey or person who discovered the object
MPEC - Minor Planet Electronic Circular, the discovery announcement

Around the Sky in 28 Days – Day 5

Tonight the Moon visits the bright star Antares, the “heart” of Scorpius. This obviously red star is the 15th brightest in the sky at an average magnitude of +1.0. We say “average magnitude” because like many red supergiants Antares is a variable star and can brighten and dim by a few 10s of percent. It is truly a supergiant star. If it were located in our solar system it would extend past the orbits of Mercury, Venus, Earth and Mars to a point well within the asteroid belt. That’s over 800 solar radii. Located a distance of 550 lightyears, Antares produces up to 60,000 times as much energy as the Sun though due to its relatively cool surface most of this energy is radiated in the infrared. It is massive enough at 15-18 solar masses that it will end its life as a brilliant supernova.

The name Antares is Greek and means “like Ares (Mars)” or “holds against Ares (Mars)”. The Greek Ares was the equivalent of the Roman Mars. Both the planet and the star are similar in color and often similar in brightness. Try comparing Antares with slightly fainter Mars which is still located low in the southwest just below bright Venus.

Tomorrow – Day 6 – The Moon passes the heart of the Milky Way.

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