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The night sky for May 2017

The Night Sky This Month - Sun, 14/05/2017 - 19:00
Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during May 2017.

The Stars and GalaxiesThe Planets
  • Jupiter
    came into opposition on April 7th so, this month, transits in the late evening and is visible rising in the east at dusk. It is moving in retrograde motion lying in Virgo initially some 9 degrees over to the right of its brightest star, Spica. This increases to ~11 degrees as May progresses. The size of Jupiter's disk decreases slightly from 43.5. to 40.8 arc seconds during May with its magnitude reducing very slightly from -2.4 to -2.3. With a small telescope one should be easily able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Galilean moons as they weave their way around it.
  • Saturn
    rises around 11:30pm BST as may begins and will be highest in the pre-dawn sky at ~4am BST. By the end of May it will rise at ~9:30pm BST and transit at around 2am BST. Lying in the western part of Sagittarius, its diameter increases from 17.8 to 18.3 arc seconds during the month as it brightness increases slightly from magnitude +0.3 to +0.1. It will be high enough in the south-east in the hours before dawn to make out the beautiful ring system which, at over 26 degrees to the line of sight, are nearly as open as they ever become. If only it were higher in the ecliptic; its elevation this year never gets above ~18 degrees and so the atmosphere will hinder our view of this most beautiful planet. [Note: I have acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations. If imaging Saturn (or Jupiter), Registax 6 has a tool to align the red, green and blue colour images to largely remove the dispersion from the image.]
  • Mercury
    is lost in the glare of the Sun this month so cannot be observed.
  • Mars
    lies in Taurus initially making a shallow triangle with Aldabaran to its lower left and the Pleiades cluster to its lower right. In early May, Mars has an elevation of ~11 degrees above the western horizon at sunset, but this reduces to ~5 degrees by month's end when Mars will be lost in the Sun's glare. It will then be lost from view all summer as it passes behind the Sun. By month's end it will lie some 6.5 degrees over to the left of Alnath, Beta Tauri. Its brightness falls slightly during the month from magnitude +1.6 to +1.7 whilst its angular diameter falls from 3.9 to 3.7 arc seconds. No details would be expected to be seen on its salmon-pink surface.
  • Venus
    rises in the east in the morning twilight on the first of the month and then climbs a little higher each morning as May progresses. On May 1st, the disk, forming a crescent 38 arc seconds high, is just 27% lit shining with a magnitude of -4.7 - its maximum brightness. By the end of the month, Venus shines at magnitude -4.5 with its angular size reduced to 25 arc seconds and its illuminated fraction increased to 48%. It is then close to its greatest elongation from the Sun of 46 degrees which it will reach on June 3rd. But, due to the shallow angle that the ecliptic makes to the horizon at this time of the year, it will then only have an elevation of ~16 degrees at sunrise.

JupiterThis is a great month to observe Jupiter which came into opposition on April 7th so, during May, will be visible in the south during the evening. It is moving down the ecliptic and lies in Virgo. It now reaches an elevation of ~36 degrees when crossing the meridian. An interesting observation is that the Great Red Spot appears to be diminishing in size. At the beginning of the last century it spanned 40,000 km across but now appears to be only ~16,500 Km across - less than half the size. It used to be said that 3 Earths could fit within it, but now it is only one. The shrinking rate appears to be accelerating and observations indicate that it is now reducing in size by ~580 miles per year. Will it eventually disappear?

May: Look for the Great Red Spot on JupiterA list gives some of the best evening times during May to observe the Great Red Spot which should then lie on the central meridian of the planet. The times are in UT.

May 4/5th - after midnight: The Moon occults the double star 49 LeonisJust after 00:20 BST, the dark limb of the Moon will occult the double star 49 Leonis (magnitudes +5.8 and +7.9 separated by 2 arc seconds). As a result, the starlight will take longer to be extinguished than from a single star. If the seeing were good, it might be possible to split the pair using a high magnification and see each component disappear.

May 5th and 6th before dawn: The Eta Aquarid Meteor ShowerThe Eta Aquarids are one of the finest meteor showers that can be seen from the southern hemisphere, but, in the northern hemisphere, may be glimpsed in the pre-dawn sky in the south-east around 90 minutes before dawn. Sadly, this year the peak is when the Moon is coming towards full - but happily low on the western horizon - so there will be some moonlight to hinder our view.

May 7th - evening: The Moon and JupiterThis evening the Moon, three days before full, will pass just 1.5 degrees above Jupiter.

15th May - evening: Observe the Galilean Satellites.If clear on the evening of the 15th and using a small telescope, one could observe the 4 Galilean Moons lined up on one side of the giant planet.

22nd May - dawn: Venus and a thin crescent MoonBefore dawn on the 22nd, Venus will be seen over to the left of a very thin waning crescent Moon.

22nd to 31st May - all night: Observe Comet 2015 V2 (Johnson)During the last 10 days of May, with no Moonlight to hinder our view, binoculars or a small telescope could be used to spot Comet Johnson as it moves down through the constellation Bootes closing in on the bright star Arcturus. It might reach magnitude +6 so should be easily visible with binoculars. The chart shows its position during this time.

27th May - ~23:20 BST: a shadow transit of Jupiter.After sunset on the last three day of the month, one can observe, if clear, a thin waxing crescent Moon passing the Beehive cluster (M44) as it moves up to pass Regulus, in Leo, on the 31st.

May 3rd and 16th, evening: The Hyginus RilleThese evenings, should it be clear, are a superb time to view the Hyginus Rill as it will lie close to the terminator. For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity. We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contrast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events. It can quite easily be seen to be surrounded by dark material. It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.

Southern Hemisphere

Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during May 2017.

Kia ora and welcome to the May Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.

Our evening skies this month are dominated by Jupiter and Saturn, along with some of our brightest stars. Jupiter will be one of the first objects to appear, visible in the north east shortly after the Sun has set. A bright waxing gibbous moon will pass within 2 degrees of the planet on the evening of May 8th, that’s 4 moon diameters apart. Both will be visible within the same binocular field of view.Just to the right of Jupiter is Spica, the brightest star in the constellation of Virgo, and below, just above the horizon is orange coloured Arcturus, which at magnitude −0.05 is the brightest star in the northern celestial hemisphere and the 4th brightest in the night sky.

Arcturus has a similar mass to the Sun, but it is further along in its lifespan and has already expanded to become a red giant, with 25 times the diameter and 170 times the luminosity of our own star. When close to the horizon it often appears to twinkle red and green as its light is broken up by our atmosphere.

All three of the brighter stars are in the southern hemisphere, and are also visible in our evening skies this month. The brightest, Sirius , sits halfway up the western sky at the beginning of the month, with Orion’s belt, now almost vertical, below. Rigel and Betelguese , the seventh and ninth brightest stars sit to either side of the belt. Both Orion and Sirius will soon be disappearing from our evening skies, before reappearing before the Sun in the morning skies over the coming months.

The second brightest star Canopus is circumpolar here in New Zealand, never dropping below the horizon. This month it sits a little higher than Sirius, further around towards the south west. To complete the trio, the third brightest star, Alpha Centauri is high in the southeast, pointing the way to the Southern Cross.

Below Alpha Centauri, rising in the twilight sky is the curve of stars making the body of Scorpius, the scorpion. Its brightest star Antares is a variable star, which ranges in brightness from magnitude 0.6 to 1.6, and is on average the 15th brightest in the night sky. Antares is a red supergiant, , one of the largest stars known, almost 900 times the diameter of the Sun. If it were placed at the centre of the Solar System, its surface would extend to the middle of the asteroid belt. The name Antares means rival of Mars, because of its striking red colour. To Māori the star is known as Rehua and represents a drop of blood Maui pulled from his nose to bait his fishhook. In Aotearoa, the constellation of Scorpius in seen as Maui’s hook, te Matau a Maui, which was used to pull up a great fish which became the north island of New Zealand.

Scorpius/te Matau a Maui is our winter constellation and will be dominating our skies over the coming months, visible throughout the night.

Sitting just 1.3 degrees to the west of Antares, and visible in the same wide field telescope view, is the 5.9 magnitude globular cluster Messier 4, just about visible to the naked eye in a clear, dark sky. M4 is one of the nearest globular clusters in the sky, at just 7,200 lightyears away and is the only globular cluster that Messier was able to resolve with the modest equipment he was using, 20 years before William Herschel was able to resolve all of the Messier globular clusters with his much larger telescopes.

M4 is one of the loosest, most open globular clusters and features a central bar of 11th magnitude stars, which can be resolved in a 10cm telescope. Through binoculars the cluster is seen as a round hazy patch.

Messier 4 contains some of the oldest stars known in our galaxy, with an estimated age of 13 billion years. Discovered by the Hubble Space Telescope in 1995, these White Dwarf stars are the remnants of ancient solar like stars that have already shed their outer layers into space.

In 2003 a planet was discovered orbiting one of these White Dwarfs and its Pulsar companion, the first circumbinary (ie orbiting both stars)”planet ever found, and the first planet detected in a globular cluster. With a mass of around 2.5 Jupiters and an estimated age of 12.7 billion years, it is also one of the oldest known extrasolar planets, earning it the unofficial nicknames “Methuselah” and “The Genesis Planet”.

A little over half way from Antares to Arcturus is another globular cluster, M5, or NGC 5904, in the constellation of Serpens. At almost 6th magnitude it is also tough to spot with the naked eye in anything but the darkest conditions, but with binoculars it is easy to find, although you will need a small telescope to begin to resolve it and start to pick out a slightly elongated shape and a few edge stars.

With a calculated age of around 13 billion years, M5 is one of the oldest globular clusters known, and at 165 light years in diameter and containing hundreds of thousands of stars, it is also one of the largest. It also contains 105 known variable stars, with the brightest and most easily observed, Variable 42, changing from magnitude 10.6 to 12.1 in just under 26.5 days.

To find M5 you can star hop from the faint star 109 Virginis to 110 Virginis and then around twice the distance again to find 5 Serpentis, and M5 is just 20' to the North West.

Below Antares, and rising a little later in the evening, is bright, cream coloured Saturn. It’s a great time to observe Saturn through a small telescope at the moment with its rings at close to maximum tilt. Saturns largest moon , Titan, can be spotted orbiting around for ring diameters from the planet, with several smaller, closer moons also visible in larger telescopes.

In the morning sky Venus rises in the east around 4am and is joined by Mercury around an hour and a half before sunrise. Mercury reaches its greatest elongation west on the 18th of May and is making its best morning appearance of the year, rising before twilight begins throughout the month.

If you’re out planet spotting in the early hours then take a look for the eta aquarids meteor shower, which peaks around the 6th of May. This shower is caused by the Earth passing through the trail of debris left behind by the famous comet Halley. The shower appears to radiate from a point near the fourth magnitude star Eta Aquarii, one of the brightest in the zodiac constellation of Aquarius, representing the water bearer.

The radiant won’t rise in the eastern sky until around 2am here in New Zealand, so the best time to go meteor spotting is in the few hours before sunrise. At the shower’s peak you may be able to spot up to a meteor a minute, many of them fast and bright and leaving glowing trails behind them. Viewing conditions this year will be much better than last, with the Moon setting on the other side of the sky in the early hours of the morning, giving you a good few hours of observing time before the Sun rises just after 7 am.

You may also have a chance for some binocular comet hunting this month as Comet PanSTARRS (C/2015 ER61) heads towards Perihelion (its closest approach to the Sun) on the 10th of May. At the start of the month it will be moving from Aquarius through to Pisces and may be visible with binoculars in our morning skies. On 4th April the comet experienced an outburst, brightening from 8th to 6th magnitude almost overnight, and whilst it is always hard to predict how bright a comet is going to get, this one is definitely worth keeping an eye on.Wishing you clear skies from the team here at Space Place at Carter Observatory.

Ancient Ogunquit Beach on Mars

APOD - Sun, 14/05/2017 - 10:00

This was once a beach -- on ancient Mars. This was once a beach -- on ancient Mars.

Star Formation in the Tadpole Nebula

APOD - Sat, 13/05/2017 - 08:00

What's all of the commotion in the Tadpole nebula? What's all of the commotion in the Tadpole nebula?

Week In Images

ESA Top News - Fri, 12/05/2017 - 15:00

Our week through the lens:
8-12 May 2017

Novel use of satnav saves precious water

ESA Top News - Fri, 12/05/2017 - 14:33

Water conservation is a growing concern globally, and particularly for farmers in the USA, where decades of irrigating huge fields has depleted vital resources of fresh surface water and groundwater. An ESA spin-off that can help to preserve water supplies while guaranteeing crop irrigation is now undergoing final testing.

Negribreen on the move

ESA Top News - Fri, 12/05/2017 - 09:47

Rapid acceleration of an Arctic glacier over the past year has been detected by the Copernicus Sentinel-1 satellites.

Uintah Basin

ESA Top News - Fri, 12/05/2017 - 09:05

Earth observation image of the week: the border of the US states Utah and Colorado is pictured in this Sentinel-2 image, also featured on the Earth from Space video programme

Galaxy Cluster Abell 370 and Beyond

APOD - Fri, 12/05/2017 - 06:00

Some 4 billion light-years away, massive galaxy cluster Abell 370 Some 4 billion light-years away, massive galaxy cluster Abell 370

The Bull's Eye and the Young Moon

APOD - Thu, 11/05/2017 - 17:00

The Bull's Eye and the Young Moon The Bull's Eye and the Young Moon

Revisit #FutureEO

ESA Top News - Thu, 11/05/2017 - 16:15

Watch the replays of the "Paradigm shifts and future prospects in Earth observation" seminar

Earth from Space

ESA Top News - Thu, 11/05/2017 - 13:50

Join us Friday, 12 May, at 10:00 CEST for the ‘Earth from Space’ video programme

Winning plans for CubeSats to the Moon

ESA Top News - Thu, 11/05/2017 - 10:09

If you could fly a CubeSat to the Moon, what could such a tiny satellite do there? ESA posed this question – and now four proposals will be studied in more detail for possible flight over the coming decade.

The Perseus Cluster Waves

APOD - Wed, 10/05/2017 - 15:00

The Perseus Cluster Waves The Perseus Cluster Waves

International rescue

ESA Top News - Wed, 10/05/2017 - 10:15

Technology image of the week: a rescue drone designed to save lives, developed by an ESA-based start-up in the Netherlands

NGC 3628: The Hamburger Galaxy

APOD - Tue, 09/05/2017 - 13:00

No, hamburgers are not this big. No, hamburgers are not this big.

Future EO

ESA Top News - Tue, 09/05/2017 - 10:45

Follow the "Paradigm shifts and future prospects in Earth observation" seminar via live webstream on 11 May at 09:00 CEST

Approach above Sunset

APOD - Mon, 08/05/2017 - 11:00

There it is! There it is!

I spy…

ESA Top News - Mon, 08/05/2017 - 08:10

Space Science Image of the Week: Looking into the Cheops telescope that will study planets circling other stars

Cooling Neutron Star

APOD - Sun, 07/05/2017 - 09:00

The bright source near the center is a neutron star, The bright source near the center is a neutron star,

Cassini Looks Out from Saturn

APOD - Sat, 06/05/2017 - 07:00

This is what Saturn looks like from inside the rings. This is what Saturn looks like from inside the rings.

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