Astronomy: The Week Ahead – Sun 30 Aug to Sat 05 Sep 2015

AstroTitlePhoto Aug 30

Sunday August 30


The Moon will rise in perigee tonight, due east. This is the Moon’s closest point to us in its monthly orbit. But look to Libra in the southwest. Saturn in a telescope is a great sight. The ringed planet is leaving us until next season, and will soon disappear into the glare of sunset. While you can, also compare the color of Scorpius’ star Antares.

Monday August 31


Tonight Neptune is at opposition. The Earth lies directly between Neptune and the Sun. That means Neptune rises at sunset, is in the sky all night, and sets with sunrise. This is the best time to view the distant world! Here you can see it low in Aquarius, and how to use two of the constellation’s stars to point to it. Neptune is at magnitude 7.8, and can be seen in binoculars, but it is much easier to recognize its blue tone with a telescope. It is only 2.4 arcseconds in size, and with high power will appear a small bluish disk. The planet is its closest to us tonight, at almost 29 AU (astronomical units; 1 AU is the distance from the Earth to the Sun).

Tuesday September 01


Venus is at its longest western elongation today, at 25 degrees from the Sun. Find it in the predawn sky in Cancer, near the head of Hydra, and below Gemini the twins. That red “star” nearby is Mars. Venus is inside our orbit just over 30 million miles away, and shows a very generous 51 arcseconds in size, as a 10% illuminated crescent. If you can view it through a telescope, you’ll be in for a visual treat! Mars is outside our orbit 150,000 million miles away, showing only a 3.7 arcsecond size disk. You can imagine a point during the year when the earth would be between the two!

Wednesday September 02


Here’s a challenge for those viewing through telescopes in somewhat dark evening skies. NGC globular clusters 7006 and 6934 lie in the constellation Delphinus, roughly between Altair in Aquila, and Enif in Pegasus. Both are small, at 3.6 and 7.1 arcminutes, respectively. They shine at magnitudes 10.6 and 8.9. Both will be unresolved, you can’t see individual stars in them. So, they will both appear as somewhat granular, fuzzy glows.

Thursday September 03


Lying between the paws of the Great Bear, Ursa Major, and the twins of Gemini, is the dim constellation Lynx, the cat. It has only one star brighter than magnitude 4.5, Alpha Lyncis, at magnitude 3.12 and 223 light years distant. It is a supergiant star, at 118 solar radii, and has the luminosity of 1622 suns!

There are only four main stars in the constellation, and they seem to get dimmer as you progress from Alpha. Can you make out the figure? This area has many dim open clusters and one famous globular cluster, which we’ll discuss Saturday.

Friday September 04


How far can you see with the “naked eye”? Try for M31, the Great Andromeda Galaxy. Distance estimates range from 2.3 to 2.9 million light years. It will appear as a dim fuzzy patch, a short hop above the orange star Beta Andromedae. Find the sweep of the constellation Andromeda between the famous ‘W’ of Cassiopeia, and the Great Square of Pegasus. Once you identify the two arc comprising Andromeda, jump up from the star Beta, to dimmer star just above it, the up again about the same distance. Do you see the dim elongated glow? If so, grab some binoculars and try again.

Saturday September 05


Here’s another challenge object. NGC 2419 is a globular cluster in the constellation Lynx. It measures a bit over 2 arcminutes in size and shines dimly at magnitude 10.4. It appears unresolved in most amateur telescopes, but will break up into individual stars at high power in larger telescopes. Thought to be 200,000 light years from Earth, it is the farthest such object in our galaxy. Most globular clusters in our galaxy are less than 1/3 that distance. Speculation exists that it was captured from another passing galaxy, and has been named “Intergalactic Wanderer.”

Happy viewing!


Astronomy: The Week Ahead – Sun 5 Apr to Sat 11 Apr 2015

Sunrise in Space via the ISS. Credit: NASA & ESA

Sunrise in Space via the ISS.
Credit: NASA & ESA


Sunday April 5

Pluto is at Western Quadrature this morning, 90 degrees west of the sun from us at is heads toward morning twilight. It is located conveniently in the Teaspoon asterism of Sagittarius, an easy location to see with the naked eye. Pluto will require a telescope and detailed chart.


Monday April 6

Between Leo and Hydra is the dim constellation Sextans, a modern creation introduced in 1687 by Johannes Hevelius. Use Regulus in Leo and Alphard in Hydra to help locate it. Sextans is rich in deep sky targets, as it covers an area away from the Milky Way.

Today, just before sunrise, Uranus reached conjunction with the sun. The sun lies between us. You can imagine this, as the constellation Sextans near tonight’s “anti-solar point”, the point in the sky the sun. In a truly dark sky, you can see the anti-solar point, it’s called “Gegenshein”.


Tuesday April 7

It’s time to bid a fond adieu to some favorite winter constellations. Canis Major, Orion and Taurus are now sinking into the early evening twilight. They will make a lovely sight this evening!


Wednesday April 8

A bright waxing gibbous moon, 85% illuminated, pairs closely in the southwestern morning sky with creamy yellow Saturn, in Scorpius. The pair are under a degree and a half apart, and will look great together in binoculars or a wide-field telescope. This also presents a great imaging opportunity!


Thursday April 9

Two solar system events occur today. Beginning at 22:51 PDT Jupiter’s moon Io begins a transit across the disk of the planet. At 23:12 you’ll see the Great Red Spot (GRS) appearing on the planet’s limb, then at 00:02 on 4/10, its shadow ingresses, quickly catches up to and passes the GRS. By 02:23 all the Io action comes to an end. Get out your telescope and watch, you’ll be amazed at Io’s speed!

Today Mercury is at Superior Conjunction. Just like Uranus a few days ago, this speedy little planet is on now the exact opposite side of the sun from us.


Friday April 10

M51 is the famous Whirlpool Galaxy, near the equally famous asterism called The Big Dipper, part of the constellation Ursa Major. M51 lies just across the constellation boundary in Canes Venatici, the Hunting Dogs, anchored by the bright star Cor Caroli (the Heart of Charles). In a dark sky, M51 shows nice spiral structure in a telescope. This is the beginning of the season to observe it in the early evenings, as it is rising. It lies 23 million light years distant, and shines at magnitude 8.4, but seems somewhat dimmer due to its large size of 9.8 arc minutes. This is a great target to observe!


Saturday April 11

The last quarter Moon is tonight, giving us Saturday with plenty of time for dark sky astronomy. Spica, rising east after sunset ushers in galaxy season, with Virgo, Leo and Coma Berenices chock full of treasures.

Enjoy & happy viewing!


Astronomy: The Week Ahead – Sun 08 Mar to Sat 14 Mar 2015


Sunday March 8

Due south at sunset is the constellation Canis Major and its brightest star Sirius. Sirius is the brightest star in the night sky at magnitude -1.5 and is a double star, a binary star system. The companion, Sirius B, is a white dwarf star, shining at magnitude 8.5. The brightness of the primary can make seeing the companion difficult, but you can do it in a telescope. Its separation from Sirius A changes around every 50 years, and it is now approaching its widest separation. Read up on Sirius, you’ll be amazed at what you learn, it’s a very interesting star!


Monday March 9

The constellation Scorpius is one of the twelve Zodiac constellations, lying along the ecliptic. The Moon and planets all traverse this constellation in their paths across the sky. Seen as a scorpion in ancient times, the constellation Libra represented its claws in Babylonian times. Antares is the red beating heart.

Scorpius is beautifully positioned due south currently for northerners, in the predawn skies.


Tuesday March 10

Get your telescope or binoculars out this morning for a view of two globular clusters just off Antares in Scorpius. M4 resolves into hundreds of stars in a telescope. It is about 7900 light years distant and very bright at magnitude 5.9, and visually about the size of our full Moon. Nearby, almost in the glow of Antares is NGC 6144, a 4.9′ magnitude 9 glow that will not resolve into individual stars. This smaller, dimmer globular is located 33,000 light years away. Nice contrast between this two similar objects!


Wednesday March 11

NGC 2903 is sometimes referred to as the “forgotten Messier.” It is certainly bright and big enough to warrant inclusion in the famous catalog. And it is easy to locate off the “tip of the nose” in Leo. Easiest is to use Regulus to move up the Sickle, then extend beyond it to the nearest bright star, and drop down slightly. At magnitude 9.7 and a generous size of 12.6’x6.0′, this galaxy discovered by Sir William Herschel is a great target.


Thursday March 12

An hour before sunrise the Moon and Saturn are paired three degrees apart high up in Scorpius. The soft creamy yellow glow of Saturn will be very apparent contrasted against the whiteness of 21 day old waxing gibbous moon, 62% illuminated.


Friday March 13

The last quarter Moon occurs today, and will be located in Ophiuchus an hour before sunrise. The position of the moon allows us to see the “bottom line” of Ophiuchus easily, as two pair of stars, one pair wide, and the other close. Another pair extends west into Serpens Caput.

A last quarter Moon on a weekend is especially nice, as it rises late, affording us plenty of dark sky time to observe dim targets such as galaxies and nebulae. Lucky us, on this Friday the 13th!


Saturday March 14

Revisit Canis Major this evening, for a look at two interesting open clusters. M41 is a large and classic open cluster you’ll see in binoculars. This cluster is thought to have been known by Aristotle, around 325 B.C. It is a bit larger than a full Moon, and bright enough to be seen naked-eye at magnitude 4.5. NGC 2362 will require a telescope. It is stunning, with the extremely large and luminous star Tau Canis Majoris at its center. A fun trick of the eye is to tap your telescope when viewing, and watch Tau jump around while the other stars seem almost stationary!

Happy viewing!