Transit of Mercury

Frequently, we observe solar and lunar eclipses here on our blue marble we call Earth. Solar eclipses are when the moon passes in front of the sun. Lunar eclipses are when Earth cuts between the sun and moon, with the moon covered in our shadow. Less commonly observed are planetary transits. Because we live on the third rock from the sun, we only get to see Mercury and Venus pass in front of it. Because orbits wobble and planes aren't aligned, this is something that is only seen a few times per century.

Transit of Mercury as seen with the unaided eye

Mercury transited the sun on November 11. Because the sun is so bright and Mercury is so small, a telescope with solar filter is a requirement to witness the event. I took a field trip to Philadelphia's Franklin Institute to see it for myself with their telescope. Because seeing Mercury normally requires a clear horizon at sunrise or sunset, most folks don't get to see it. This was my first time, and now I've finally seen all six naked eye planets- I included Earth, which I see every day.

Franklin Institute's telescope with solar filter

I got a shot of Mercury being live-streamed on the big screen

Sadly, I wasn't able to get my own pictures of Mercury, but I did get pictures. NASA was live-streaming and has a video up on their Youtube page. If you want to see a Mercury transit live and in person, you'll have to wait until 2032. You'll need to be in Africa, eastern Europe, or western Russia to see it. Otherwise, the next transit here in the states won't be until 2049. But if you think that's bad, the next transit of Venus won't happen until 2117.

NASA posted this picture of a prior transit on their Facebook page.
The little black spot on the bottom is Mercury. The one on
the top is a sunspot.

Star of Wonder

Science is very good at explaining things and can even solve a mystery that has no remaining witnesses. Science is able to tell us how long ago a frozen cave man lived, and even how he died. One mystery that science has been unable to explain, but has offered many possible solutions to, is the Star of Bethlehem that the Magi followed. The star is mentioned in the gospels, and many biblical events have been confirmed by archaeology. But is the star a legend, a myth, a miracle, or something perfectly logical?

There are several astronomical phenomena that could explain the star. People at the time were very astute when it came to sky watching, as the stars and moon were (and still are) great navigational aids, so anything out of the ordinary appearing in the sky would have been noticed and documented. Some examples of astronomical phenomena that could have occurred on the First Noel include a planetary conjunction, a nova, a supernova, and a comet.

A planetary conjunction is when two or more planets appear very close to each other in the night sky, and may even appear to be a single object. Just such an event- a Jupiter and Saturn conjunction- took place in the year 7 BC, just outside the accepted date of Jesus’s birth (6 BC- 4 BC). The timing is very close and the position in the sky is correct, but the planets were not close enough to appear as a single star and while the conjunction may have led the Magi in the general direction of Bethlehem from Jerusalem, but did not stand over Bethlehem as stated in the Bible. 

Conjunction of Venus and Jupiter, 2015

A nova (“new star”) is star that suddenly flares up many times in magnitude. It is given this term because in most cases, it is a star that ordinarily is not visible to the naked eye. Similar to a nova is a supernova, a star which has exploded. Chinese and Korean records indicate either a nova or supernova occurred in the year 5 BC, which also fits the timeframe for the nativity. Unlike the planets, however, a nova or supernova would remain in a fixed position in the sky. 

Remnants of 1987 supernova (NASA)

A comet is best described as a dirty snowball orbiting the sun. Depending on location and trajectory, they can become visible to the naked eye as they approach the sun. The period of visibility and brightness vary from comet to comet, but as an object in orbit, it would certainly move about the sky. Chinese records indicate a comet appearing in the year 5 BC, which is within the accepted time of Jesus’s birth. The comet’s location in the sky would have it preceding the Magi first to Jerusalem, then to Bethlehem. It even appeared during spring, which is when it is believed he was born, even though we celebrate Christmas in December. That’s a different story for a different blog. 

Comet ISON (NASA)

Over 2000 years later, the great mystery of the Star of Bethlehem may finally have an answer thanks to forensic astronomy and the meticulous records of the Chinese. Was it really a comet, a completely rational cosmic occurrence, which led the Magi to Bethlehem? If so, did divine intervention place the comet where it needed to be at the right time? That question might never be answered.

This week's information comes from two sources. Speculation about conjunctions and comets comes from Colin J. Humphreys and the speculation about novae and supernovae comes from Mark Kidger.

Cosmic Ballet, Part 2

Despite dire warnings not to travel to Oregon for the solar eclipse, I went any way. Traffic was not as bad as predicted. My gamble that everyone going to Oregon would have left over the weekend paid off. My gamble that homeward-bound traffic would be going the opposite direction of where I was headed paid off. I even managed to get some pictures for those of you who weren't lucky enough to witness totality, which was a first for me.

Before totality, small chunk of sun missing from top right

The eclipse caused these funky curved shadows

Using your hands to make a pinhole viewer

Totality! The black circle is the moon, the white ring is the sun's corona

The sky was dark enough that some stars were visible. I think this is Venus.

The eclipse got underway just after 9 AM Pacific time, immediately preceded by a flock of birds flying overhead away from the sun. Was that related to the eclipse? I don't know. I don't recall seeing any birds until after the eclipse was over. It took a while to notice any changes in lighting, but as totality got closer it was like someone turning a dimmer switch until it got dark. At that point, the eclipse glasses came off, the pop of some fireworks, and the crowd at the nearby football field let out a cheer. It was oddly quiet and oddly dark for about a minute until there was a flash of light where the top of the sun came out from behind the moon and the dimmer switch turned the other way and daylight returned.
The next total solar eclipse to hit the US is in April 2024. At that time, I hope to be in the field studying how animals react to an eclipse. Not much is known because they are such an infrequent event. Many animals run on a solar (day-night) cycle and scientists like myself wonder what they do when night suddenly happens during the day for a brief period.
Stay tuned for more stories from the road following Nature Minute's great American road trip!

The Worlds Around Us

This week’s Nature Minute is out of this world! Nature isn’t just limited to Earth. Head outside after sunset and check out our neighbors in the solar system. Venus is the brightest object in the night sky and you can find it in the constellation Aquarius, in the southwestern sky. If you happen to have a telescope handy, look for distant Neptune just above and to the left of Venus. Higher above Venus and more the left but still close by is Mars, which appears to be a bright red non-twinkling star. Jupiter is the brightest object (other than the moon) after midnight. Again, if your telescope is handy and you are still awake, check out Jupiter. You may be able to see some of its moons. Jupiter, the largest planet, is almost like a mini solar system within our solar system. If you are an early riser, or maybe just can’t sleep, Saturn and Mercury rise just before the sun. Mercury is hard to see because it is close to the sun and therefore always low on the horizon. In my area, trees to the west or Cascade Mountains to the east make viewing Mercury impossible. Saturn is a treat to view through the telescope. Its rings are not visible to the naked eye, but they pop when viewed through the telescope. I’ve seen them a few times before and I never get over it. It’s very surreal. It looks fake.

Lunar eclipse

Venus (bottom) and Jupiter (top) in conjunction

To check out the planets and stars, get out of town. The darker the sky, the better. Up in the mountains, in the desert, or along the beach are great places for stargazing. The full moon is your worst enemy, unless you are checking out the moon. If you want to check out Saturn or Mercury, use caution not to get your telescope caught in the rising sun, unless you happen to have a solar filter. In that case, you really don’t need to be reading this blog. You probably know more about space than I do. This week’s planetary positions are courtesy of the good folks at EarthSky.org.