When will we see another bright comet?
By Joe Rao
May 10, 2019, 1:58:30 PM EDT
Recently, a friend of mine asked when we might be able to see a comet. He was surprised when I said there are several visible right now.
Indeed, you can find a list of upcoming visible comets on this useful site compiled by Japanese comet enthusiast Seiichi Yoshida. The site provides information on comets that are currently visible as well as comets that will be visible each month for the next five years. For this month, Yoshida lists four observable comets.
But none gets brighter than magnitude +12 (lower magnitudes are brighter), and the comets are visible only under dark, clear skies, using moderately large telescopes. Indeed, the vast majority of periodic comets — comets whose orbits are well known and have been observed more than once — fall into this category. These comets quietly come and go and are known only to enthusiastic amateur astronomers who make a concerted effort to hunt them down with good binoculars or telescopes. Generally, they are unimpressive to the eye, usually appearing as nothing more than faint fuzzballs, even in large telescopes.
Of course, when my friend asked his question, I knew exactly what he was alluding to: He wanted to know when we might see a stupendously brightand/or fantastically structured comet, perhaps one that would develop a tail stretching a quarter of the way or more across the sky. Unfortunately, such objects give no advance notice as to when they will appear. But with some confidence, I can state that at least one of these comets is heading toward the inner solar system even as I type these words.
But whether it will appear three weeks, three months or three years from now is unknown.
So what are our chances of seeing such a celestial showpiece? More on that in a moment, but first, let's talk about what needs to happen to produce a bright comet.
Recipe for a bright comet
The unpredictability of a passing comet's appearance and brightness is no surprise to those who study these enigmatic objects. What we see depends on many variables — the comet's orbit; the relative locations of the comet, Earth and the sun; and the size and composition of that icy clumping of solar system rubble that forms the comet's nucleus.
The nucleus's dusty, rocky material and frozen gases are similar to the composition of Saturn's rings. This part of a comet, usually only a few miles across, is gradually warmed by the sun's heat, and expels gas and dust into space, often in distinct jets. But such emissions from the nucleus are often nonuniform. To predict comets' activity, astronomers have developed general formulas and models for comet brightness based on the observed behavior of many comets going back to the late 19th century. Usually, a comet's activity increases rapidly as it draws closer to the sun; the brightness typically varies (roughly) as the inverse fourth power of its solar distance.
Put another way, as a comet's distance from the sun is halved, its brightness increases by a factor of 16, or three magnitudes.
But comets can be capricious and, like people, have their individual quirks. The physical appearances and behaviors of comets are as varied as the appearances and behaviors of people; no two are alike.
More Weather News
Weather News - June 20, 2019, 3:55:22 PM EDT
Residents of the central United States will have to remain alert for daily rounds of severe weather through this weekend.
Weather News - June 20, 2019, 4:10:01 PM EDT
This week's stormy weather pattern in the northeastern United States is coming to an end, but not before severe weather and flash flooding threaten more communities along the Interstate 95 corridor into Thursday night.
Weather News - June 20, 2019, 3:36:57 PM EDT
Services were canceled Wednesday, but that didn't stop worshipers from showing up -- and several children sheltered inside when the storm tore through.
Weather News - June 20, 2019, 12:29:42 PM EDT
A potentially dangerous heat wave will grip parts of Europe next week.
Weather News - June 20, 2019, 3:01:59 PM EDT
On the heels of the announcement that this year's wildfire season could be worse than 2018, residents from California to New Mexico will face a heightened fire danger into Saturday.
Weather News - June 20, 2019, 10:30:43 AM EDT
An area of showers and thunderstorms in the Philippine Sea is slowly becoming more organized and may become the next named tropical system in the West Pacific basin.
Weather News - June 20, 2019, 1:33:16 PM EDT
Cyclone Vayu brought needed rainfall and a break from intense heat to parts of northwest India in recent days; however, a return to hot and dry weather is expected beginning on Friday.
Weather News - June 20, 2019, 11:26:19 AM EDT
Spectators endured wet weather both Tuesday and Wednesday, but improvement is expected for the final days of the festival.