Take a series of photos from the Juno spacecraft and just project them in sequence to make a timelapse movie of the spacecraft swinging past Jupiter. Sounds easy… Right?
Not easy at all. As the spacecraft orbited past the planet the perspective changes rapidly. To make a natural seeming animation much more would have to be done. Mathematician Gerald Eichstaedt did just that… Taking 36 images he projected each image on a mathematically modeled sphere, then panned through each image using the orbital trajectory of the spacecraft to create a view to simulate actually being there.
There is one question we all have to ask when a beautiful comet graces the skies…
Where to look?
Like any other solar system object, comets move against the sky. Even worse, when close to the Earth or Sun they can be moving so quickly against the stars that coordinates quickly become out of date. Aiming a telescope using coordinates a day old, or sometimes even only an hour old will result in a view of empty sky. A few stars perhaps, but no comet.
You need a table of coordinated calculated for regular time intervals, an ephemeris. Alternately you need a set of coordinates calculated for the exact time you will be looking.
Astronomers, professional and amateur alike, are getting ready for comet C/2012 S1 ISON, possibly the highlight of a year that has already seen several good comets.
Discovered in September 2012 by Vitali Nevski and Artyom Novichonok, of the ISON project, a group of telescopes dedicated to discovering and tracking solar system objects. The comet was then an 18th magnitude object in the outer solar system, an impressive find for a small telescope.
When astronomers first calculated the comet’s orbit they found a surprise. The comet will pass close to the Sun. Not just close, but extremely close! On November 28th the comet will pass perihelion, its closest approach to the Sun. At a mere 1,860,000km (1,150,000miles) this will be a close pass indeed. As perihelion is measured from center to center, the distance is even closer if you consider the 695,500km (432,200mile) radius of the Sun. Subtracting the solar radius you realize the comet will pass a mere 1,165,000km (724,000miles) above the surface of the Sun. At this distance the intensity of the solar radiation will be nineteen thousand times more intense than a sunny day on Earth.
The next surprise was hinted at by the orbital calculations. The orbital solution indicated a nearly hyperbolic path, suggesting that this was a new comet, one that had not visited the inner solar system before. This possibility was strengthened by later observations of the comet.
This week Mercury will be exiting the dawn sky, sliding closer to the Sun in our sky each day. It will pass through superior conjunction on January 17th, heading for an evening apparition beginning in the final days of January.
Winter solstice occurs today at 01:12HST. Today the Sun will occupy the most southerly position in the sky of the year. The term solstice comes from the latin terms Sol (the Sun) and sistere (to stand still). On this day the Sun seems to stand still as it stops moving southwards each day and begins move to the north. This is the first day of winter as marked by many cultures in the northern hemisphere.
Today Mercury reaches maximum elongation, the furthest point it will reach from the Sun in the sky and the highest it will be above the sunrise for this morning apparition. The planet is easily visible as a bright, starlike object about 15° above the rising Sun as the twilight begins. Over the next couple weeks Mercury will slide back into the sunrise, heading for superior conjunction on February 16th.
Today the Earth is furthest from the Sun, a point called apehelion. We will be about 152,098,232km (94,509,459miles) from the Sun. Compare this to the 147,098,290km (91,402,639miles) we were at perihelion on Jan 4th, a difference of about 5,411,169km (3,362,344miles) occurs throughout one orbit.
It may seem odd that we are actually at the furthest for the middle of northern summer, you just have to remember that proximity to the Sun is not the cause of the seasons. The seasons are caused by the axial tilt of the Earth, creating short and long days throughout the year, with a resulting change in the angle and intensity of the sunlight.
Spring equinox occurs today at 19:14HST. Today there will be little difference between the length of the night compared to number of daylight hours. This is the first day of spring as marked by many cultures in the northern hemisphere.
Some calendars may mark the first day of spring on the 20th. And it is, for much of the world. For Hawai’i the equinox occurs on the 19th when you consider the time zone difference.