Comet Johnson Getting Brighter in Small Telescopes

Image of Comet Johnson (C/2015 V2) at Apparent Visual Magnitude +8, with an obvious tail, photographed in the Constellation Hercules the Hero on the night of April 1-2 by Ade Ashford.
(Image Source: AstronomyNow Magazine from the United Kingdom)

By Glenn A. Walsh

Reporting for SpaceWatchtower

Comet Johnson (C/2015 V2) has now become the brightest comet visible in small telescopes and possibly binoculars. It will come closest to the Earth on June 5.

Currently, Comet Johnson is passing through the Constellation Bootes the Herdsman. An hour after sunset, it can be found about 40 degrees above the eastern horizon. It will pass Bootes' brightest star, Arcturus, on June 6. Comet Johnson is visible most of the night. It is highest in the southern sky around local Midnight.

Comet Johnson will appear as a diffuse white ball, looking nothing like the pinpoint-like stars or oval planets of our Solar System. Only in the larger, professional telescopes are the two tails visible. The larger one is the traditional dust tail, while a much thinner tail is composed of gas.

At closest approach to Earth, Comet Johnson will be at a distance of 0.812 Astronomical Units or 75,480,115.505697 miles / 121,473,471.0084 kilometers. Used by astronomers to measure the great distances within our Solar System, one Astronomical Unit (AU) is the average distance between the Earth and the Sun: 92,955,807.273026 miles / 149,597,870.70 kilometers.

Visible in small telescopes and binoculars evenings after dusk, the Comet currently shines at an Apparent Visual Magnitude +7.05. Comet Johnson will reach perihelion (closest approach to the Sun) on Monday Morning, 2017 June 12 at 5:31:39 a.m. Eastern Daylight Saving Time (EDT) / 9:31:39 Coordinated Universal Time (UTC).

In late June, after Comet Johnson reaches perihelion, it could possibly reach a maximum brightness of +6—which would be barely (particularly considering the diffuse nature of a comet) bright enough to be seen with the naked-eye under ideal conditions. However, it should continue to make a good target for small telescopes and, possibly, binoculars.

For the first part of Summer in the Northern Hemisphere, Comet Johnson will be particularly visible to northern viewers due to its favorable orbit, which has a high inclination of 50 degrees relative to the ecliptic. However, by the end of July this comet will become an almost exclusively Southern Hemisphere object, as it continues progressing southward in the sky.

On the evening of 2015 November 3, astronomer Jess Johnson discovered Comet Johnson as part of the Catalina Sky Survey. When first seen, the Comet had a very dim Apparent Visual Magnitude of +17, at a distance of 6.17 AU or 573,537,330.874568 miles / 923,018,862.219 kilometers.

This is the first and last time we will see Comet Johnson, at least in the Inner Solar System. Comet Johnson has a hyperbolic orbit. Once it goes around the Sun, it will move away and never come back, eventually leaving our Solar System for-good.

American astronomer Fred Whipple described a comet as a “dirty snowball.” Comets are a combination of rocks, dust, water ice, and other frozen gases, from the early days of our Solar System.

The solid core of a comet is known as the nucleus. Streams of dust and gas released from the comet, as it nears the Sun, form a thin atmosphere around the comet nucleus called the coma. The coma is composed mostly (90 per-cent) of water, with dust making-up the rest of the coma.

Most, but not all, comets have one or more visible tails. The tail(s), which is usually not visible in the Outer Solar System, is composed of dust and gases emanating from the comet, caused by solar radiation as the comet comes closer to the Sun; this radiation usually is too weak to create tails in the Outer Solar System. Normally, a comet's tail(s) points away from the Sun, no matter the direction of movement of the comet; hence, a comet leaving the Inner Solar System often has a tail pointing in the direction of the comet's motion.

Comets usually have a highly-eccentric, elliptical orbit around the Sun, which brings a comet into the Inner Solar System for a short time, while it spends most of its time in the Outer Solar System. Short-period comets originate in the Kuiper Belt, just beyond the orbit of the Planet Neptune, while long-period comets are thought to originate in the Oort Cloud, a spherical cloud of icy bodies beyond the Kuiper Belt.

Short-period comets may have an orbit of only a few years, while long-period comets, potentially, could have an orbit of several million years. Some comets have very short lives, and they disappear into the Sun before they can resume traveling to the Outer Solar System. Other comets, known as hyperbolic comets, go around the Sun once and never come back, continuing into Interstellar Space forever.

To more easily see comets, it is better to be away from city lights, as artificial lighting can drown-out the dimmer comets. Bright moonlight can also drown-out some of the dimmer comets, so monitor the Moon Phase on the monthly SpaceWatchtower Astronomical Calendar.

When looking for a comet, it is best to be in an area that gets a good view of the entire sky (with few obstructions such as buildings, trees, or hills). Of course, you definitely want an unobstructed view for the area of the sky where you expect to find the comet. And, if the comet is expected to be low on the horizon where you expect to view it, you want your observation site to be as high in elevation as possible.

Of course, viewing comets, like all celestial observations, are weather-permitting. If there are more than a very few clouds in the sky, a comet will be much more difficult to find.

And, you want to go out ahead of time, before you actually start looking for comets, to get your eyes accustomed to the dark sky. Dark-adapting your eyes for comet-watching could take up to a half-hour.

Internet Links to Additional Information ---

SpaceWatchtower Monthly Astronomical Calendar ---
Current Month (2017 May):
Link >>> http://spacewatchtower.blogspot.com/2017/05/astronomical-calendar-2017-may.html
Calendar Archives: Link >>> http://buhlplanetarium3.tripod.com/Buhlnews.htm#astrocalarchiv

Comet: Link >>> https://en.wikipedia.org/wiki/Comet

Comet Johnson (C/2015 V2) -
Link 1 >>> https://theskylive.com/c2015v2-info
Link 2 >>> https://en.wikipedia.org/wiki/C/2015_V2

Related Blog Post ---

"4 Comets May Be Visible w/ Small Telescopes." 2017 April 12.

Link >>> http://spacewatchtower.blogspot.com/2017/04/4-comets-may-be-visible-w-small.html

     Safe Public Viewing of the Great American Solar Eclipse
                         Monday, August 21, 2017
     Mt. Lebanon Public Library, South Suburban Pittsburgh
More Info: Link >>> http://buhlplanetarium.tripod.com/archivenews/releases/poster-flyer/2017SolarEclipse-Flyer.htm

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2017 May 22.

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