Welcome to the Boston Astronomy Site ...
Phases of the Moon:
The Moon & Planets:
Comets:
Current Night Sky: the Solar System:
Mercury passes through superior conjunction – a position on the opposite side of the Sun - on February 7, and becomes visible in the evening sky the last week of the month. By the 29th, it is 15° above the horizon at sunset but, because of the ecliptic’s angle to the horizon, sets an hour and a half after the Sun. On that evening, the planet shines at magnitude -1.0; a telescope shows it as a gibbous disk 70% illuminated and 6.3 arc-seconds across.
The next planet outward from the Sun,
Venus, is much more conspicuous. As February begins, the
planet is at an altitude of 33° above the horizon - a third of
the way to the zenith – at sunset, and sets almost 3 and a half
hours after the Sun. By month’s end, it is 40° up at sunset and
sets almost 4 hours after the Sun. It’s brightness during the
month increases from magnitude -4.1 to -4.3. Venus is by far the
brightest planet in Earth’s skies, due to a combination of
several factors. It is, of course, closer to the Sun than our
planet; what’s more, it is the planet that gets closer to us
than any other. (Mars, often regarded as the closest planet,
gets no closer than 55 million km, while Venus approaches to
within 38 million km.) In addition, Venus is covered by a
uniform layer of white, highly reflective clouds that bounce
back much of the sunlight hitting them into space. Those same
clouds – featureless in visible light - make Venus a
disappointment in a telescope. On the 1st
of the month, it appears as a
gibbous disk 15.1” across and 74% illuminated; by month’s
end it will be 18.2” in diameter and 64% lit.
This month, Venus serves as an excellent guide for locating Uranus. Uranus starts out the month to the west of – or lower than – Venus, but the two pass each other as Venus gains altitude and Uranus loses it. Their closest approach is on February 9th, when the two wind up just 0.3° apart – within the same field of view of a telescope at low power. Uranus, at magnitude 5.9, is about 10,000 times dimmer than Venus. At higher power, it may be possible to make out its 3.4”-diameter green-grey disk.
Brilliant
Jupiter needs to
help from Venus; it is the second-brightest point of light in
the sky. Nevertheless, only about 40° separate the two as
February begins, and, by month’s end, they are just 12° - barely
a fist-width – apart. Jupiter dims somewhat – from magnitude
-2.3 to -2,2 – during the month. It doesn’t set until midnight,
affording prime-time viewing. A telescope will show its disk,
flattened from rotation, 39.2” across its equator as February
begins and 36.2” across at month’s end. Generally, the dark
North Equatorial Belt and South Equatorial Belt will be easy to
see, along with a number of less distinct belts and zones
approaching the polar regions. If you look at the right time,
you may see the Great Red Spot, but be prepared for a feature
that has lost much of its color in recent years and appears, at
best, a pale pink. Lately, there have been a number of prominent
dark spots, or barges, extending into the light-colored zones.
Jupiter’s atmosphere is always a work in progress. The four Galilean moons – Io, Europa,
Ganymede, and Callisto – always put on a performance. One
example:: on the 22nd, a transit of Europa is
underway as darkness falls in eastern North America; mere
minutes before the transit ends, Europa’s shadow begins
transiting Jupiter. The shadow transit ends at 10:00 PM EST.
As February begins, Mars rises
shortly after 8 PM local time; by month’s end, it is rising just
after sunset. The planet is approaching opposition in early
March, and – though it is a relatively distant one as
oppositions go (see our “What’s New” page) – Mars’ viewing
prospects are improving dramatically. During February, the
planet undergoes nearly a doubling in brightness – from
magnitude -0.5 to -1.2. It is not only the brightest point of
light in the constellation Leo but is instantly recognizable due
to its ruddy red color. As viewed through a telescope, Mars’
disk swells from 11.8” to 13.8” in diameter, and its north polar
cap, though shrinking during the northern hemisphere spring,
should still be prominent. Other features that should be
discernible are the large dark areas such as Syrtis Major and
Sinus Meridiani. It is during times such as this that 19th-century
astronomers labored long into the night to see a few precious
seconds of clarity when the atmosphere of Earth was sufficiently
still to reveal detail on the Martian surface. In next month’s
Sky Report, we’ll discuss some modern day techniques for
achieving the same results in mere minutes, and with equipment
affordable to any amateur astronomer.
Saturn rises just before midnight local time on February 1st and about two hours earlier by month’s end. The planet brightens slightly from magnitude +0.6 to +0.4 during the month; it is thus slightly brighter than 1.0-magnitude Spica, the most brilliant in its host constellation of Virgo. A telescope will show the beautiful ring system inclined about 15° to our line of sight. The globe of the planet itself grows from 17.6” to 18.4” in diameter, while the visible rings swell from 39.9” to 41.8” across.
Neptune passes through solar conjunction on February 19th, and is thus not visible this month.
Dwarf Planets/Asteroids:
Vesta moves from Aquarius into Pisces on February 18th. On the 21st, it passes a half-degree N of 4th-magnitude 30 Piscium. On the 27th, it is 5° S of Uranus.
Weather permitting, this is a perfect time to observe Mars. Why?
A cycle of oppositions of Mars.
This is why the opposition is 2012 is about as poor a one as possible.
The Sky in February
This website has been created by and is supported by a group of Boston-area amateur astronomers. It is intended to be a convenient site to access news and information about astronomy and space-related activities of interest to the community and the public.
The class trip to the Observatory on January 31 is cancelled due to predictions of cloudy weather.
We will meet as usual in the classroom at 8:00 PM this week.
We will reschedule the Observatory trip for next Tuesday, Feb. 7.
Thanks for your patience!
Introduction to the Solar System
Spring of 2012
When we look up at the sky, the easiest objects to
see are the members of our Solar System: the Sun, the Moon, and the
planets. Yet how truly familiar are they? In this course we’ll learn how
to identify the planets that will be prominent this spring: Mercury,
Venus, Mars, and Saturn. The ancients that named them could do as much,
but we’ll also learn to recognize the planets as more than just points
of light in the sky. Centuries of observation by telescopes have
transformed these specks into worlds, and decades of space exploration
have now transformed them into landscapes. Modern astronomy is now on
the verge of providing answers to age-old questions about the planets:
Where did they come from? What are they really like? Are any of them
capable of supporting life? And how is our destiny bound up with theirs?
We’ll discuss these and other ideas about the Solar System around us.
One of our meetings will be at a local observatory;
there we will be able to use a large telescope to learn about the Solar
System first-hand.
No math or science background required!
8 Tuesdays 8:00 PM – 9:30 PM. Runs April 3 - May 22,
2012.
We look forward to seeing you!
The Sky in February 2012
Current Night Sky: At A Glance
Phases of the Moon:
|
Full Moon |
February 7 |
4:54 PM EST |
|
Last Quarter Moon |
February 14 |
12:04 PM EST |
|
New Moon |
February 21 |
5:35 PM EST |
| First Quarter Moon | February 29 | 8:21 PM EST |
On February 9th, a waning gibbous Moon passes S of Mars. On the
13th, a waning gibbous passes S of Saturn. On the evening of the 22nd,
a very thin crescent lies to the right of Mercury. A crescent passes N of Venus
on the 25th, and N of Jupiter on the 26th.
Evening Planets (after sunset):
- Jupiter, in SW
- Mars, in E
Mercury, in W
Uranus, in W
Uranus, in W
Visible At Midnight:
Mars, in SE
- Saturn, in SE
Morning Planets (before sunrise):
- Mars, in W
- Saturn, in SW
- Saturn, in SW
Comets:
Comet C/2009 P1 (Garradd), may
brighten slightly, from magnitude 6.8 to 6.7. It moves from
Hercules into Draco on February 13th, and on into
Ursa Minor on the 29th. This month the comet
becomes circumpolar from mid-northern latitudes. Photo op
alert: it passes within a half-degree of the globular
cluster M92 on February 3rd.
Meteors:
There are no major meteor
showers in February.
The Solar System in February
Current Night Sky: the Solar System:
The Planets
Mercury passes through superior conjunction – a position on the opposite side of the Sun - on February 7, and becomes visible in the evening sky the last week of the month. By the 29th, it is 15° above the horizon at sunset but, because of the ecliptic’s angle to the horizon, sets an hour and a half after the Sun. On that evening, the planet shines at magnitude -1.0; a telescope shows it as a gibbous disk 70% illuminated and 6.3 arc-seconds across.
This month, Venus serves as an excellent guide for locating Uranus. Uranus starts out the month to the west of – or lower than – Venus, but the two pass each other as Venus gains altitude and Uranus loses it. Their closest approach is on February 9th, when the two wind up just 0.3° apart – within the same field of view of a telescope at low power. Uranus, at magnitude 5.9, is about 10,000 times dimmer than Venus. At higher power, it may be possible to make out its 3.4”-diameter green-grey disk.
Saturn rises just before midnight local time on February 1st and about two hours earlier by month’s end. The planet brightens slightly from magnitude +0.6 to +0.4 during the month; it is thus slightly brighter than 1.0-magnitude Spica, the most brilliant in its host constellation of Virgo. A telescope will show the beautiful ring system inclined about 15° to our line of sight. The globe of the planet itself grows from 17.6” to 18.4” in diameter, while the visible rings swell from 39.9” to 41.8” across.
Neptune passes through solar conjunction on February 19th, and is thus not visible this month.
Vesta moves from Aquarius into Pisces on February 18th. On the 21st, it passes a half-degree N of 4th-magnitude 30 Piscium. On the 27th, it is 5° S of Uranus.
Mars Gets Near
Weather permitting, this is a perfect time to observe Mars. Why?
Earth, on its inner orbit, moves faster than Mars and consequently “passes” it;
this happens roughly every 26 months. Such events are called “oppositions”, and
one is approaching in early March. It is at such times that Mars and Earth are
at their closest. It is also at such times that Mars is in the opposite side of
Earth from the Sun; by necessity, then, Mars will rise at sunset, be visible all
night, and set at sunrise. If the orbits of Earth and of Mars were circular,
that would be the end of the matter.
The orbit of Earth around the Sun is very nearly circular, with its distance at
the aphelion – the point of greatest distance from the Sun – about 4% greater
than that at perihelion – the point of closest approach to the Sun. The orbit of
Mars, however, is decidedly eccentric, with a difference of over 20% between
aphelion and perihelion distances. This means that, as far as Earth-Mars
distance goes, all oppositions are definitely not equal; the separation between
the planets at opposition depends on where along Mars’ orbit Earth passes
the Red Planet. As it happens, the quality of oppositions seems to vary in a
15-17 year cycle, and the opposition of 2012 is the worst one of the cycle!
In fact, Mars reaches aphelion on February 15th – just seventeen days
before opposition. The result, as you can see from the diagram below, is that
the distance of Mars from both the Sun and the Earth is near a maximum:
And, incidentally, the eccentric orbit of Mars accounts for the fact that, even
though Mars reaches opposition on March 3, it is closest to Earth on March 5. On
that day the two planets will be 100.78 million km, or 62.6 million miles apart.
The Sky in February
8:00 PM EST on February 15th
Looking at Zenith, South at Bottom.
(click to enlarge)*
Not far from the zenith on early February evenings
lies one of the most remarkable objects in the sky: the
Crab Nebula. The Crab exploded into our planet’s history
in the year 1054 AD, when Indian, Arabic, Chinese, and
Japanese records mention the appearance of a bright star
in the region. For a time it was brilliant enough to be
visible in broad daylight. Telescopic observers in the
1700’s noted a nebula in the region, and the object
became M1 – Messier object number one – in Charles
Messier’s catalog of non-cometary objects. In 1848 the
Earl of Ross called it the Crab Nebula because of its
shape. It is now known to be the remnant of a supernova
- a star that has reached the end of its normal life and
undergone a massive explosion. The remnant of the star’s
core has become an ultradense neutron star – an object
perhaps 30 km across and spinning at a furious rate of
over 30 revolutions per second! Who says astronomy is
dull?