Category: Astronomy

Exploring the cosmos

Comet C/2012 S1 ISON

A new comet discovered earlier this week has caught the attention of the astronomy community. Comet C/2012 S1 (ISON) was discovered Tuesday by a telescope affiliated with ISON, the International Scientific Optical Observation Network. This is a network of mid-sized telescopes dedicated to surveillance of the near earth region of our solar system.

The reason this comet is intriguing is a combination of a large estimated size and an orbit that appears to provide both a close approach to the Sun and favorable viewing from the Earth.

The comet will approach the sun as close as 0.012 AU on November 28th, 2013, quite close indeed. The comet will also approach Earth as close as 0.4 AU (60 million kilometers or 37 million miles) on December 26th, 2013. As a result this comet could achieve a magnitude well into the negative numbers, brighter than most objects in the sky except the Sun or Moon.

This comet is in addition to comet C/2011 L4 (PanSTARRS), expected to be an unaided eye comet during the spring of 2013. If we get lucky 2013 will be a great year for comets.

As I have cautioned in the past, comet predictions are to be taken with a good amount of skepticism. This could be a spectacular comet, or this could be a mediocre comet, we will just have to wait and see. In the meantime pay attention to the light curve as it nears the Sun. As my friend David Levy observed… “Comets are like cats; they have tails, and they do precisely what they want.”

A Line of Planets in the Sunset

As Mercury rises clear of the Sun’s glare it joins Mars and Saturn in the sunset sky. Tonight the three will form a nice line of planets. Mercury will still be quite low, about 12° from the Sun at sunset. Saturn is next in the line at 19° elevation at sunset. Mars will be over 30° high at sunset. As usual Mars and Saturn are about the same brightness, Mars at 1.2 magnitude, Saturn at 0.72. Mercury will be the brightest at -0.6 magnitude, which will aid in seeing the planets lower in the sunset.

The three will dance in the sunset over the coming weeks with Saturn and Mercury joining up for a close set around October 4th.

Dusty Road

Rush hour for Mauna Kea is just before sunset. This is when the day crews are coming down, while the summit tours and telescope operators are heading up.

The timing of this rush can be variable depending on time of year and what time sunset occurs. Twice a year this rush is at its worst, when everyone heads up and down at the same time. This can lead to some difficult driving conditions… A lot of vehicles on a road that can be challenging. A cloud of fine cinder dust and a setting Sun just adding to the confusion…

Dust Out
Fine cinder dust creating a hazardous “dust out” condition on the Mauna Kea summit access road

Fall Equinox

Fall equinox occurs today at 04:49HST. Today there will be little difference between the length of the night compared to number of daylight hours. This is the first day of fall as marked by many cultures in the northern hemisphere.

2012 Solstices and Equinoxes

UT HST
Perihelion Jan 5 03:59UT Jan 4 17:59HST
Spring Equinox Mar 20 05:14UT Mar 19 19:14HST
Summer Solstice Jun 20 23:09UT Jun 20 13:09HST
Apehelion Jul 4 23:59UT Jul 4 13:59HST
Fall Equinox Sep 22 14:49UT Sep 22 04:49HST
Winter Solstice Dec 21 11:12UT Dec 21 01:12HST
Source: USNO Data Services Website and the NASA Sky Calendar

 

Mercury in the Sunset

Mercury is beginning its third and final evening apparition of the year. Today the planet will be over 10° from the Sun, rising a little further each day until maximum elongation on October 26th. The planet will pass Saturn around October 4th and have a very close conjunction with the Moon on October 16th.

Continue reading “Mercury in the Sunset”