Posted by on Jan 25, 2023 in Main |

A Winter Hunter – Orion

Venus, Jupiter and Mars are brilliant beacons in the evening sky, along with more ‘A’ list stars than you will see in any other month. The first signs of spring are now on the way, well as far as the night sky in concerned. The winter star patterns, Orion, Taurus and Gemini, are drifting westward as a result of our annual orbit around the Sun. Leo and Bootes are rising higher in the east.

The Plough is now higher in the north east, with its handle pointing in the general direction of the horizon. If you follow the curve of the handle you will come to a bright orange star low in the sky. This is Arcturus in the constellation of Bootes. Arcturus is the brightest star in the spring sky.

The ‘W’ of Cassiopeia is high in the north west.

Orion still dominates the southern part of the sky. However, as Orion is a little to the west of south, now is the best time to see Sirius the Dog Star. This is the brightest star in the sky. Using the three stars that form Orion’s belt to form a line, continue down that line and you will reach Sirius.

The stars are a very long way away. Sirius, although the brightest, is in fact very close to us, at around 8.5 light years away.

The other winter stars, Aldebaran and the Seven Sisters in Taurus are now starting to get lower in the west, while Castor and Pollux together with Procyon are now at their highest points. Capella is still high, being just past the overhead position. However, while Capella is very high, Vega, which occupied the overhead point in summer, is now at its lowest, close to the northern horizon.

The Planets:-

The innermost planet is deep in the dawn twilight of the south western sky, in the constellation of Capricornus. At magnitude –0.2, the innermost planet rises about 6.30am.

Venus is spectacular after sunset. Shinning at magnitude –3.9 it sets below the horizon about 8pm. As the month progresses Venus moves inexorably upwards towards the second brightest planet, Jupiter. The crescent Moon joins these two bright planets on the 22nd February.

The red planet can be found among the stars of the constellation of Taurus, just to the left of the Pleiades star cluster. Mars falls below the horizon about 3.30am. At magnitude +0.1, the red planet is a little brighter than the constellations principal star; the red giant Aldebaran. On the 27th February the first quarter Moon is close by.

Brighter than any of the stars at magnitude – 2.1, Jupiter can be found in the constellation of Pisces. It sets around 9pm. The crescent Moon passes by the gas giant on 22nd of the month, when Venus is also encroaching.

The ringworld is lost in the Sun’s glare this month and unfavourable for observation.

This distant world is just on the edge of naked eye visibility at magnitude +5.7. It is usually difficult to identify among the background stars. This month Uranus lies in the constellation of Aries. It sets bellow the horizon around 1.30am.

The outermost planet lies on the borders of Aquarius and Pisces in the southern sky. With a magnitude of +7.9, you may just catch a view with binoculars or a telescope. Neptune falls below the horizon around 8pm. On the 15th of this month you can use bright Venus to locate Neptune, as it will be just below the evening star.

This distant planet is located in the constellation of Sagittarius, however it will be well below the horizon during the dark hours.

The largest body in the asteroid belt can be located in the constellation of
Virgo. At magnitude +7.4, it rises above the horizon just after 10pm.

Highlights of the month:-

The year is off to a great start for comet hunters, as what could be the best comet of 2023 is now set to take centre stage this month. In January Comet C/2022 E3 (ZTF) made its closest approach to the Sun. Then, after zipping around the Sun, it will make its closest approach to Earth on Wednesday 1st February.

Comet C/2022 E3 (ZTF) was first discovered in March 2022 by the Zwicky Transient Facility (ZTF), which scans the entire Northern Hemisphere sky once every two days from Palomar Observatory in California. You may have noticed many other comets have the acronym ZTF in their names, too. That’s because they were discovered by the same facility.C/2022 E3 began its long journey in the far outer reaches of the solar system, within the Oort Cloud.

After rounding the Sun, C/2022 E3 has grown brighter, and the comet’s brightness is predicted to peak around 1st of this month when it makes its closest approach to Earth by passing within about 0.28 AU of our planet. At this point, many observers and astrophotographers hope C/2022 E3 will reach naked-eye magnitudes as it skims through a particularly rich region of the sky near the northern pole, setting the scene for some gorgeous photos.

Even at its brightest, however, Comet C/2022 E3 (ZTF) is not expected to form a bright, long tail that’s visible without a telescope. Still, even without a tail, the comet will be a memorable sight. Plus, comets can always surprise us with unexpected outbursts, so it’s worth following C/2022 E3’s progress to see what it will do!

On the last day of January, C/2022 E3 is just 11.5° from the star Polaris and moving at a speedy clip. The comet will cover about 12″ per minute, forcing astroimagers to opt for shorter exposures if they seek to capture any sharp details.

Shortly after C/2022 E3 makes its closest approach to Earth at a distance of 0.28 AU (42 million km). The comet is expected to get brighter than magnitude 6 and thus become visible with the naked eye from a dark sky site, appearing as a smudge in the sky. During its closest approach to Earth it will appear near the north celestial pole and be located within the Camelopardalis constellation. On February 10th –11th the comet will pass 1.5 degrees from Mars and on February 13th to 15th will pass in front of Hyades star cluster.

The unusual green colour is likely due to presence of diatomic carbon, chiefly around the comet’s head. The C2 molecule, when excited by the solar ultraviolet radiation, emits mostly in infrared but its triplet state radiates at 518 nm. It is produced by photolysis of organic materials evaporated from the nucleus. It then undergoes photodissociation, with lifetime of about two days, therefore the green glow appears in the comet’s head but not the tail.

The comet will then fade over time as it heads away from the Sun toward the outer solar system, and scientists aren’t yet sure whether or not it will ever return.

Venus is spectacular this month and on the 15th it passes very close to Neptune. So you can use Venus to identify the outermost planet. Point your binoculars or a low power telescope towards the evening star, and you will find the much fainter Neptune just 20 arcminutes to the lower right. Venus at magnitude 03.9 is 60,000 times brighter than Neptune at magnitude +7.9.

On the 22nd of this month there is a fantastic sight in the west after sunset, with the crescent Moon lying between the two brightest planets Venus and Jupiter. Jupiter being the one that is above the Moon, with Venus below. The following night of the 23rd Jupiter will be below the crescent Moon with brighter Venus lower down towards the horizon.

The night of the 27th sees the first quarter Moon close to the red planet Mars with the giant red star Aldebaran just below.

February is the month most favoured for the appearance of the rare type of cloud known as nacreous or ‘mother-of-pearl’. Although not strictly an astronomical phenomenon, it can provide a spectacularly beautiful sight for sky-watchers.

Cold polar air is forced into layers of the atmosphere between 8 and 12 km high giving rise to colourful and impressive clouds that are seen at their most vivid around the time of sunset. Observers should be alert on all clear days, and keep the sky under regular scrutiny.

Phases of the Moon this month are:-

Full Moon 5th February

Last quarter 13th February

New Moon 20th February

First quarter 27th February