The Night Sky

The Night Sky in and around Swindon - April 2024

<font face="Arial, Helvetica, sans-serif" size="2"></font>

April 12: Comet Pons-Brooks below Jupiter

Comet Pons-Brooks
Image: Nigel Henbest/Philip's

On this evening Comet Pons-Brooks passes just below Jupiter. The Pleiades, Uranus and Jupiter will all appear in a line above it.

April 11: Pleiades just above the Moon

The Moon & Jupiter
Image: Stellarium

The Pleiades, also known as the Seven Sisters, is a bright star cluster in the constellation Taurus. On this date, it will appear just 0.4° north of the Moon, offering a dazzling juxtaposition of the star cluster next to our natural satellite.

The planets this month

The following data is drawn from Space.com

Jupiter

Jupiter will be quite brilliant with a silver-white luster in 2024. It starts the year in the constellation Aries the Ram, then crosses over into Taurus the Bull on April 28 where it will remain for the balance of the year.

During evenings from Jan. 1 to April 26, it'll shine brightly, as well as during mornings from June 8 to Dec. 6. Evening viewing will be optimal again from Dec. 7 to December 31.

Saturn

Saturn shines like a yellowish-white "star" of moderate brightness. The famous rings, however, are only visible in a telescope.

The rings were at their maximum tilt toward Earth in Oct. 2017, but are now rapidly closing to our line of sight. They will turn edge-on to the Earth during the spring of 2025. The process will begin in 2024 within the boundaries of the constellation Aquarius, the Water Carrier, and the planet will remain there for the rest of the year.

You can catch Saturn during evenings from Jan. 1 to Feb. 11, mornings from March 17 to Sept. 7, then evenings again from Sept. 8 to Dec. 31. Saturn's brightest in 2024 will fall between Aug. 25 to Oct. 1. Saturn will be in opposition to the sun on Sept. 8. Saturn and Venus will appear dramatically close to each other (with Saturn just 0.2-degree S) on the morning of March 21 and will be 0.4-degree S of Mars on April 10.

Mercury

As an evening star, Mercury appears in the western sky and sets about an hour after the sun does. As a morning star, it appears in the eastern sky, rising about an hour before the sun. There must be a clear, unobstructed horizon on these occasions.

Mars

This will be another "off" year for Mars, as for much of 2024 it will appear relatively dim while dawdling in the morning sky. Mars will actually be invisible for the first 10 days of the new year, too deeply immersed in the bright dawn twilight to be seen.

Venus

Always brilliant, and shining with a steady, silvery light, you can catch Venus during mornings in the eastern sky at dawn from Jan. 1 to April 8; evenings in the western sky at dusk from July 30 to Dec. 31

The constellation Leo

The constellation Leo is now in the south-eastern sky in the evening. One of the few constellations that genuinely resembles its name, it looks likes one of the Lions in Trafalger Square, with its main and head forming an arc (called the Sickle) to the upper right, with Regulus in the position of its right knee. Regulus is a blue-white star, five times bigger than the sun at a distance of 90 light years. It shines at magnitude 1.4. Algieba, which forms the base of the neck, is the second brightest star in Leo at magnitude 1.9. With a telescope it resolves into one of the most magnificent double stars in the sky - a pair of golden yellow stars! They orbit their common centre of gravity every 600 years. This lovely pair of orange giants are 170 light years away.

Leo also hosts two pairs of Messier galaxies which lie beneath its belly. The first pair lie about 9 degrees to the west of Regulus and comprise M95 (to the east) and M96. They are almost exactly at the same declination as Regulus so, using an equatorial mount, centre on Regulus, lock the declination axis and sweep towards the west 9 degrees. They are both close to 9th magnitude and may bee seen together with a telescope at low power or individually at higher powers. M65 is a type Sa spiral lying at a distance of 35 millin klight years and M66, considerably bigger than M65, is of type Sb. Type Sa spirals have large nuclei and very tightly wound spiral arms whilst as one moves through type Sb to Sc, the nucleus becomes smaller and the arms more open.

The galaxies M65 and M66

The second pair of galaxies, M95 and M96, lie a further 7 degrees to the west between the stars Upsilon and Iota Leonis. M95 is a barred spiral of type SBb. It lies at a distance of 38 million light years and is magnitude 9.7. M96, a type Sa galaxy, is slightly further away at 41 million light years, but a little brighter with a magnitude of 9.2. Both are members of the Leo I group of galaxies and are visible together with a telescope at low power.

There is a further ~9th magnitude galaxy in Leo which, surprisingly, is in neither the Messier or Caldwell catalogues. It lies a little below lambda Leonis and was discovered by William Herschel. No 2903 in the New General Catalogue, it is a beautiful type Sb galaxy which is seen at somewhat of an oblique angle. It lies at a distance of 20.5 million light years.

The 8.9th magnitude, type Sb, Galaxy NGC2903

The constellation Taurus

Taurus is one of the most beautiful constellations and you can almost imagine the Bull charging down to the left towards Orion. His face is delineated by the "V" shaped cluster of stars called the Hyades, his eye is the red giant star Aldebaran and the tips of his horns are shown by the stars beta and zeta Tauri. Although alpha Tauri, Aldebaran, appears to lie amongst the stars of the Hyades cluster it is, in fact, less than half their distance lying 68 light years away from us. It is around 40 times the diameter of our Sun and 100 times as bright.

To the upper right of Taurus lies the open cluster, M45, the Pleiades. Often called the Seven Sisters, it is one of the brightest and closest open clusters. The Pleiades cluster lies at a distance of 400 light years and contains over 3000 stars. The cluster, which is about 13 light years across, is moving towards the star Betelgeuse in Orion. Surrounding the brightest stars are seen blue reflection nebulae caused by reflected light from many small carbon grains. These relfection nebulae look blue as the dust grains scatter blue light more efficiently than red. The grains form part of a molecular cloud through which the cluster is currently passing. (Or, to be more precise, did 400 years ago!)

VLT image of the Crab Nebula

Close to the tip of the left hand horn lies the Crab Nebula, also called M1 as it is the first entry of Charles Messier's catalogue of nebulous objects. Lying 6500 light years from the Sun, it is the remains of a giant star that was seen to explode as a supernova in the year 1056. It may just be glimpsed with binoculars on a very clear dark night and a telescope will show it as a misty blur of light.

Lord Rosse's drawing of M1

Its name "The Crab Nebula" was given to it by the Third Earl of Rosse who observed it with the 72 inch reflector at Birr Castle in County Offaly in central Ireland. As shown in the drawing above, it appeared to him rather lile a spider crab. The 72 inch was the world's largest telelescope for many years. At the heart of the Crab Nebula is a neutron star, the result of the collapse of the original star's core. Although only around 20 km in diameter it weighs more than our Sun and is spinning 30 times a second. Its rotating magnetic field generate beams of light and radio waves which sweep across the sky. As a result, a radio telescope will pick up very regular pulses of radiation and the object is thus also known a Pulsar. Its pulses are monitored each day at Jodrell Bank with a 13m radio telescope

The constellation Virgo

Virgo, rising in the east in late evening this month, is not one of the most prominent constellations, containing only one bright star, Spica, but is one of the largest and is very rewarding for those with "rich field" telescopes capable of seeing the many galaxies that lie within its boundaries. Spica is, in fact, an exceedingly close double star with the two B type stars orbiting each other every 4 days. Their total luminosity is 2000 times that of our Sun. In the upper right hand quadrant of Virgo lies the centre of the Virgo Cluster of galaxies. There are 13 galaxies in the Messier catalogue in this region, all of which can be seen with a small telescope. The brightest is the giant elliptical galaxy, M87, with a jet extending from its centre where there is almost certainly a massive black hole into which dust and gas are falling. This releases great amounts of energy which powers particles to reach speeds close to the speed of light forming the jet we see. M87 is also called VIRGO A as it is a very strong radio source.

The Giant Elliptical Galaxy M87

Below Porrima and to the right of Spica lies M104, an 8th magnitude spiral galaxy about 30 million light years away from us. Its spiral arms are edge on to us so in a small telescope it appears as an elliptical galaxy. It is also known as the Sombrero Galaxy as it looks like a wide brimmed hat in long exposure photographs.
The Sombrero Galaxy

M104 - The Sombrero Galaxy