What was that? Unusual sightings in the night sky
One of the ways Perth Observatory serves the taxpayers of Western Australia is by answering enquiries from the public. Many of these involve interpreting people's naked-eye observations of something in the sky. Hopefully, reading this section will stimulate an awareness of what is visible in the night sky as well facilitating an increase in observing skills so that anyone can make scientifically meaningful observations. More details concerning some of the objects discussed here can be found in the Solar System fact sheet pages, or even more detailed information is available in the annual WA Astronomy Almanac.
Most careful and detailed observations of apparently unusual objects are explicable by known phenomena. When given thorough (but time consuming) examination, less than 2% of allegedly unusual observations remain 'unidentified'. Just because they are unidentified does not mean they are evidence of extraterrestrials, or their technology! The late Professor Carl Sagan stated that, 'extraordinary claims require extraordinary evidence'.
- The following objects are the subject of most enquiries:
- Venus
- - is the brightest star-like object in the sky. It can appear as
an 'evening star' as well as a 'morning star' - it just depends on its and
Earth's positions in their respective orbits around the Sun. Venus orbits closer
to the Sun than Earth, so it is only visible up to about three hours after sunset
or before sunrise - it can never be visible around midnight (except in polar regions).
Consult the monthly sections of Perth Observatory's
annual WA Astronomy Almanac for
information on the visibility of this planet (and other planets).
Below is a table containing the Venus viewing opportunities for WA.
visible in evening visible in morning August 2008 - February 2009 April - November 2009 March - October 2010 November 2010 - July 2011 October 2011 - May 2012 June 2012 - March 2013 For more information consult our fact sheet about Venus.
- Meteors / Shooting stars
- - are the glow of energy released as small particles about the size of a grain of sand 'crash' into Earth's upper atmosphere. Very bright meteors are called fireballs or bolides. Sometimes they are so bright they can even be observed in the daytime, and sometimes a sonic boom can be heard as they break the sound barrier when they plough through the atmosphere. At certain times of the year the Earth passes through a cloud of comet debris and the number of meteors substantially increases (see meteor showers in the Solar System Information Section). Some meteors are the debris from collisions between asteroids.
- Artificial Satellites
- - are generally visible for a few hours after sunset and a few hours before sunrise as they reflect sunlight off their highly reflective outer surfaces. Around midnight low-Earth orbiting satellites (the majority) are not visible because they are in Earth's shadow. Most satellites are launched in a roughly West to East orbit as this has the lowest fuel requirements. This is also the trajectory of most of the space junk that glows on re-entry into the atmosphere. Space junk re-entries have orbits essentially parallel with the ground so they last for a longer duration and can be viewed along a long path across the Earth. Weather and reconnaissance satellites can orbit North to South (or vice versa) in order to get a longer duration view of the Earth. Iridium communication satellites have one highly reflecting surface and when the geometry is favourable we can observe a slow flash of light that builds up to a maximum in about 5 seconds, and then fades over a similar time. About one of these flashes is visible from any location on the Earth every night, and about once per month a flash about ten times brighter than Venus provides a spectacular sight. Information about the visibility of satellites can be found in the Astronomy internet links page. Alternatively, go to our web page with links to heavens-above.com satellite viewing opportunities for your town in Western Australia.
- Clouds
-
- can partially obscure the Moon, planets and aircraft thus giving the
impression of changing lights or a halo effect. Beams of light moving through the
sky, or circles of light on the under side of clouds result from searchlights
operated on the ground (usually to promote some entertainment activity). High-altitude
aircraft can also leave a trail of water vapour called
a contrail.
- Refraction
- - (the bending of light) through ice crystals or water droplets high in the atmosphere can create halos and coronae (coloured clouds) near the Sun or Moon.
- Pranks
- - some people make artificial 'UFOs'. One of the Observatory staff has actually recovered one after tracking it. Such 'UFOs' may have the appearance of either a solitary yellow or orange/red light, or a string of lights moving in unison across the night sky. This prank can be very dangerous because of the fire and aviation hazards involved.
Recording your observations
You can submit your observations using the web form below. Or download a Sighting Report Form, then fax or mail it to the Observatory. Assistance with completing the form below is also provided in order to assist in the recording of scientifically useful observations. If you don't need assistance just use our brief version of the web form.
One important point to remember is: record your own observations as soon as possible after the event. Try not to be influenced by those who may have accompanied you. Instead, get them to complete their own Sighting Report Forms. We don't all observe things in the same way, so multiple individual reports of a sighting will provide a more accurate description of the event. Also, try to be objective about your observations. This can be difficult because a spectacular or sudden event can evoke a variety of emotions.
Observer Details
Name:
Address:
Email:
Telephone:
Mobile:
Fax:
Sighting Details
The Sighting Details section has many parts, but please try to be brief as well accurate with your report.
The date and time are important details. Don't forget to look at your watch or a clock as soon as possible after the sighting (this is probably inappropriate during the sighting). Local time (appropriate to your time zone) should be recorded to the nearest minute.
Date: Time (24 hour): hours minutes
Try to be fairly precise with your location. It is acceptable to record this in relative terms such as '100 metres west of Fremantle Railway Station', 'in my backyard', etc. Observatory staff can always determine the location more accurately later if need be.
Location:
Also note the sky conditions as best you can. Conditions other than clear, dark skies can really limit the quality of the observation or distort an otherwise commonplace event such as the motion of an aeroplane.
Sky Conditions (clear, 1/2 moon, 1/3 cloud, raining, etc):
Method of Observation (naked eye, binoculars, etc):
Some sightings are over in an instant, but try to determine the duration. It's probably inopportune to look at your watch during a sighting, but you could try to count the seconds using some mental (or voiced) counting method like - one (thousand and), two (thousand and), three (thousand and) ... Beware, most people are notoriously unreliable at guessing time intervals after a particularly startling event.
Duration:
hours/minutes/seconds
Some phenomena have sound associated with them so report anything that you hear.
Sound (rumble, boom, whistle etc):
The trajectory, or path across the sky, or the location of a stationary event, is important data. The altitude above the horizon and the compass bearing where you first detected the object are the first things to note. The horizon has an altitude of 0° (assuming any surrounding hills and valleys are of insignificant size), while straight overhead (the zenith) is at altitude 90°. One way to estimate altitude is by spreading out your hand and holding it out at arm's length. The span between the tips of your thumb and little finger is approximately 20°. Compass bearings start at 0° for due North, and progress to 90° for due East, 180° for due South, 270° for due East, and 360° (reset back to 0°) for the full circle around to due North. A compass will give you an accurate bearing and the difference between true North and Magnetic North is generally negligible in this context. If you can't determine the altitude and bearing at the time, then work them out at a later time providing you remember these quantities with respect to the scene around you, eg "above the South-side neighbour's highest tree when I was standing on my front door step". Apply the same principles for the altitude and bearing when the object was last seen. Record if it disappeared below the horizon. Note the requirement for direction to be expressed in angular format.
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Actual distance measurements are extremely unreliable for objects in the sky because there are few, if any, distance markers on which to base your estimate.
Try to estimate the angular size of the object. For comparison the Moon is 1/2 degree in diameter and a finger width at arm's length from your eye is about 1 to 2 degrees wide.
Apparent Angular Size (eg Full Moon is 1/2 degree): degrees
Also note any colour (and whether you are colour blind!).
Colour:
Record the structure of the object: was it a star-like point, did it fragment, etc?
Structure (eg point-like, streak, fragments):
Your observation will gain greater credibility if it is confirmed by another independent observer (who should complete a separate Sighting Report Form) or by use of another observing method such as photography.
Confirmation (other observer, video, etc):
Finally, record anything you think is relevant concerning the sighting or your particular observation.
Other Comments:
NOTE: This is not particularly sensitive information so ignore the email warning when you submit.
Please note that we do not intent to respond to each submission to our sightings database - we don't have sufficient staff.
Please feel free to copy the Sighting Report Form as many times as you need. Take them with you on your holidays, give them to your friends who live on (say) a remote cattle station or to your police officer sister-in-law etc. It is unlikely that you will discover a new phenomenon unknown to science, but not impossible! One type of object you may sight quite often is a bright meteor. Your observation may assist in recovering any piece that reaches the ground. This extraterrestrial material is scientifically valuable as it gives clues on such matters as the formation of Solar System.
If you complete a Sighting Report Form, or this web form, please read the first part of this article. You will probably be able to identify what you observed. Then, if appropriate, please mail (or fax) your report to the address on the Sighting Report Form. If you think your sighting is of immediate interest please telephone the Observatory and relay the information you have just recorded. (Observatory staff will attempt to answer the telephone at night but sometimes they are too busy with observing duties). Use of the Sighting Report Form, or this web form, should not only assist you as an observer but should also aid Perth Observatory staff in interpreting your sighting.
Finally, it's important to just enjoy viewing the night sky - its beauty has entranced humankind for untold millennia.
