Searching for Neptune After Dark
Last updated 9/19/2022 at 1:13pm
Remember a few years back when Pluto was deemed to be no longer a planet? The internet erupted with protests. "Why isn't Pluto a planet?" people cried. "It was a planet when I went to school and, as far as I'm concerned, it still is!"
Well, scientists are in the business of classifying everything, and when new data or understanding becomes available, they must reclassify objects to make them better fit the scheme. So, it should have come as no surprise to anyone who follows science that astronomers reclassified Pluto, a tiny ice ball near the edge of our planetary system, as a "dwarf planet."
And that means that Pluto's reclassification out of official planethood gives the honor of being the most distant planet from the sun to Neptune.
Neptune was discovered after astronomers learned that the planet Uranus, which William Herschel had found six and a half decades earlier, didn't keep to the precise path skywatchers had expected.
A young English astronomer named John Couch Adams calculated that the motion of Uranus was apparently being affected by another world that lay beyond and its gravitation was tugging on it. Adams even calculated where this unknown planet might be found; unfortunately, no one in England ever bothered to search for it.
The same was true in France where Urbain Le Verrier independently made the same calculations. Again, no one seemed to care.
But Le Verrier didn't give up. He showed his calculations to the German astronomer Johann Galle, who aimed his telescope skyward and found the new planet – eventually named Neptune – on his very first night of searching!
That was in 1846 and, since then, few beginning stargazers have ever even looked for this distant world. Well, now's a good time to change that because, this week, Neptune reaches its opposition point where it not only lies at its nearest to Earth – about 2.69 billion miles – but also shines at its brightest.
Finding Neptune among the faint stars of Aquarius isn't easy, however, and since this distant world is invisible to the unaided eye, you'll need to use "star-hopping" techniques and have a very dark rural sky, binoculars and lots of patience to spot it.
First, find brilliant Jupiter in the eastern sky, and the faint star Phi Aquarii to its west; that star forms a nice little "arrow" that aims at right angles to Jupiter. Aim your binoculars about two-thirds of the way between Jupiter and Phi. There, you might spot Neptune as a faint bluish "star." A small telescope aimed in this direction will show a distinctive bluish-green hue that distinguishes it from neighboring stars.
If you're not sure you've found it, sketch the area, being careful to mark every star in its exact position. Then, a week or two later, check out this same region of the sky and see which of the faint objects has changed its position. That's Neptune!
If needed, you can visit theskylive.com/neptune-info for a more detailed finder chart for the planet.
As challenging as Neptune might be to find, there's something really special about seeing with our own eyes the farthest planet of our Solar system!
Visit Dennis Mammana at dennismammana.com.