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.
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.
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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