What’s in the Sky in September

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September

 

The best time to observe the dust orbiting Earth, which is known as the Zodiacal Light, is around the Southward Equinox which falls this year on 22nd September  AEST.
So a couple of days either side you can look for it.
You do need a dark sky to see the zodiacal light so head to the darkest sky you can reach and look just after sunset. Turn off unnecessary lighting to help keep the night dark.
  • 1st Saturn is approaching  Opposition  on the 8th September and is rising at ( closest position to Earth, which was on 8th September and is a stunning evening object at Magnitude o.6, distance 1296.3 million km,  72.07 light minutes away. The image above is Saturn at 20:hrs AEST on the 1st September at an altitude of 17 degrees 31 min.
  • 6th  Moon at Apogee, furthest point from Earth this month, 0:53hrs AEST,  distance from Earth 406,209.2 km.
  • 21st Introduction to Astronomy Course 17:15 – 19:15hrs Inquiries 0419 103 213 Viewing of Saturn and other objects if clear afterwards, BYO Telescope and Binoculars if you have them but they are not necessary.
  • 22nd Southward Equinox 22:44hrs AEST.
  • 28th Moon at Perigee, Closest point to Earth this month, 23:26hrs AEST, distance from Earth 357,285.7km.
  • 6th Oct Daylight Savings begins. AEDT Time.

 

  • Universal Nomenclature of the      Equinoxes and Solstices Each celestial object has coordinates similar to a street directory to locate its’ position in the heavens.Celestial Sphere – An imaginary sphere surrounding the Earth on which the celestial bodies appear to lie.Celestial Longitude (CLong) – coordinateon the Celestial Sphere that corresponds tothe longitude on Earth and is measuredfrom 00.00h. Measured in hours, minutes, seconds or sometimes given as degrees,minutes seconds corresponding to degreesin a circle, ie 360 degrees. 

    Celestial Latitude (CLat)– corresponds to latitude on Earth’s surface and is measured

    in degrees, minutes, seconds. Up to 90

    degrees North (Nth) or South (Sth) of the Celestial Equator.

    + for the Northern Hemisphere,

    – for the Southern Hemisphere.

     

    Celestial Equator – directly above the

    Equator on the Earth’s surface.

     

    Northward Equinox – Day & Time the

    Sun crosses the Celestial Equator travelling into the northern Hemisphere. 00.00h CLong

     

    North Solstice   – Date and Time Sun reaches its’ furthest northern position ~ 23.5 degrees Nth. of the Celestial Equator. The Tropic of

    Cancer on the Earth’s surface, northern limit

    of Sun overhead.

                       

    Southward Equinox – Day and Time

    Sun crosses the Celestial Equator travelling into the Southern Hemisphere.

     

    South Solstice – Date and Time the Sun

    reaches its furthest southern position ~ 23.5 degrees Sth. of the Celestial Equator.

    The Tropic of Capricorn on the Earth’s

    Surface, southern limit of Sun overhead.

     

    The preceeding 4 terms indicate:

    1.Direction of the Earth’s Poles

    relative to the Sun.

    2.Extent of the Nth/Sth movement

    of the Sun overhead

    3.Direction of seasonal change of the

    position of the Sun due to the angle of the

    Earth’s axis of rotation,  ~ 23.5  degrees.

    Ecliptic – Path of the Sun against the background of the stars.

     SCP – South Celestial Pole

    NCP -North Celestial Pole

    Both directly above the Earth’s Poles.

     

    The Point of Northward Precession –

     The point the Sun crosses  the Celestial Equator travelling  into the Northern Hemisphere. The point is actually moving 1/7 sec/day. It is linked  to Celestial Longitude as the point slowly  slips along the Celestial Equator.

     

    Epoch   For a printed map the stars positions are fixed and so the Epoch date needs to be stated, ie Current Epoch is 2000.  Printed star maps are good for about 50 years, then the next epoch data is required for astronomers, ie next epoch will be 2050.

     

    Tropical Year – Time for the Sun to travel from one Northward Equinox to next,

    365.2422 days.

     

    Siderial Year – Time taken for the Earth to complete one orbit relative to the fixed stars, 365.2564 days.

     

    The difference between the Tropical and Siderial years is due to the effects of

    precession, a gradual westward drift in the ecliptic. The gravitational pull of the Sun and Moon on the Earth’s equatorial bulge cause

    the Earth’s axis to trace out  a circle on the sky every 25,800yrs.

     

    Judith Bailey – Ballarat Municipal Observatory & Museum

    E:  info@ballaratobservatory.org.au 0429 199 312

     

What’s in the Sky in August

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Image: Looking towards the centre of our Milky Way Galaxy.  Credit: Mark Justice

August

At this time of the Year the spectacular heart of our Milky Way Galaxy is now setting earlier and the best views for this year end this month.

  • 9th Moon at Apogee, furthest from Earth for the month 11:34hrs AEST, 405,295.5km.
  • 11th  Saturn is rising at 20.08hrs AEST and is at a distance 1,312,914,389 km, magnitude +0.8 and is moving closer and due to reach opposition on 8th September. tilt of planet is 2.7469 degrees, almost edge on.
  • 11th Jupiter is rising at 03:13hrs AEST with magnitude -2.2, distance 811,025,822 km. Locate low in the East near Mars rising at 03:04hrs AEST at magnitude 0.9.

Meteor Showers

  • 12th-13th Perseid Meteor shower peaks very low in the East. This is not a good shower for the Southern Hemisphere but some meteors could be visible just before dawn, start observing from after midnight on 12th August. Jupiter and Mars are up also at this time.

The shower is active: July 17–August 24; Maximum: August 12, 13h to 16h UT   August 12th 23h – August 13th 04hrs Ballarat Time. The Meteor rate ZHR = 100 for Northern Hemisphere viewers.

The orbital period of the parent comet 109P/Swift-Tuttle is about 130 years. The Perseids produced strong activity from a primary maximum throughout the 1990s. Enhanced activity was last observed in 2016 due to passages through separated dust trails.
A filament crossing occurred on 2018 August 12 around 20h UT  06h Ballarat time. (A filament is thought to be an accumulation
of meteoroids in a mean-motion resonance.)
High activity well after the main peak has been reported during some recent returns. On 2021 August 14, shortly after 08hUT , a sharp increase of the ZHR – more than 100 above the basic level – was observed by different techniques. This was about 1.5 days after the
nodal maximum and about 0.7 days after the lesser late maxima in 2018 and 2020. Nothing similar has been observed during the 2022 return.
J´eremie Vaubaillon noted that there are encounters with five very old trails (four of them more than 1,300 years old) mainly on August 12 between 04h and 11h UT. Monitoring activity during this period is of interest because such observations are scarce.

 

DATA Credit: IMO